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CHERISE MARTIN FINaL 1809856

This document is an honours dissertation submitted by Cherise Martin to the University of Auckland in November 2015. The dissertation investigates using sodium concentrations in speleothems as a proxy for past wind conditions and storm events in New Zealand. Laser ablation inductively coupled plasma mass spectrometry was used to measure trace element concentrations in two speleothems from Waitomo and Wairoa caves over the period of 0-800 AD. Preliminary results show larger sodium peaks in the Wairoa speleothem that correspond with periods of increased storms identified in nearby lake sediments, suggesting sodium in speleothems may be a useful proxy for reconstructing paleo-wind and storm conditions.

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! ! ! ! Honours!Dissertation! ! ! !!!!!!!!!!! ! !!!!!!!!!!!!!!!!Earth!Science ! ! ! ! November!2015! ! Sodium!concentrations!in!speleothems! as!a!proxy!and!archive!for!past!wind! conditions!and!storm!events! ! Cherise!Martin! The!University!of!Auckland! ! ! ! ! ! ! ! ! ! Word!count! (Includes!abstract,!chapter!1>4!&! ! ! 8,!827!!words! conclusion,!excludes!figure!captions):!! ! ! ! Total!word!count:!! ! ! ! 11,!098!words!
! ii! ! Sodium!concentrations!in!speleothems!as!a!proxy!and!! archive!for!past!wind!conditions!and!storm!events! ! by! ! Cherise!Martin! ! A!dissertation!submitted!to!fulfil! the!requirements!for!a! Bachelor!of!Science!(Hons)! for!the!School!of!Environment! at! The!University!of!Auckland! ! Professor!Joel!Baker! &! Simon!Barker! ! Date!submitted! 16th!November!2015! ! Keywords:!speleothem,!sodium,!paleoclimate,!wind!and!storm!events,!ICP>MS! ! ! ! ! ! ! ! ! ! !
! iii! Acknowledgments! ! I! could! not! have! completed! my! dissertation! without! the! help! of! several! individuals,! whom! I! deeply! thank.! My! advisor,! Professor! Joel! Baker,! whom! offered! the! incredible! opportunity!to!work!with!state!of!the!art!and!innovative!technology!in!Wellington.!He! matured!and!evolved!my!understanding!in!the!geochemistry!world.!Dr!Simon!Baker!who! was!continuously!there!to!guide!my!understanding.!!Both!have!given!me!support!and! constructive! criticism.! Dr! Paul! Williams! who! was! available! for! all! my! questions! and! provided!me!with!my!two!speleothems.!My!friends,!which!I!am!fortunate!to!have!too! many!to!name!individually,!whom!promoted!balance.!My!family,!both!far!and!near!for! the!unconditional!encouragement.!I!am!also!thankful!for!the!financial!contributions!from! the!Faculty!of!Science!for!my!research.!I!greatly!appreciate!help!in!the!laboratories!from! Andreas,!Dan,!Simon,!Joel,!Neville,!as!well!as!analytical!assistance!from!Michael!Rowe.! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
! iv! ! ! ! !
! v! Abstract(( ! Trace!element!data!were!measured!by!laser!ablation!inductively!coupled!plasma!mass! spectrometry! in! two! speleothems! from! Waitomo! (GG5;! western! North! Island)! and! Wairoa!(DS;!eastern!North!Island)!over!the!period!0–800!AD.!The!focus!of!this!study!was! to!investigate!if!Na!concentrations!in!speleothems!provide!a!proxy!and!archive!for!past! wind!conditions!and!storm!events.!The!Waitomo!speleothem!has!significantly!higher!Mg! concentrations!as!compared!with!the!Wairoa!speleothem,!interpreted!to!reflect!greater! cave! depth! at! Waitomo.! Mg/Ca! ratios! in! the! Wairoa! speleothem! show! clear! cyclical! variations!with!distinct!peaks,!which!are!most!likely!recording!past!climatic!variations.! The!Wairoa!speleothem!is!a!more!sensitive!archive!that!better!records!climatic!change! relative!to!the!Waitomo!speleothem!due!to!the!former!being!a!shallower!cave!system.!As! such,! Na! was! normalised! to! Mg! in! order! to! minimise! the! effect! of! cave! depth! on! speleothem!chemistry.!Na/Mg!ratios!are!higher!on!average!and!show!larger!peaks!in!the! Wairoa!speleothem!than!in!the!Waitomo!speleothem,!which!most!likely!reflects!the!fact! that!the!Wairoa!speleothem!was!taken!from!a!site!relatively!close!to!the!coast.!Large!Na! peaks!in!the!Wairoa!speleothem!between!0–120,!470–550!and!680–830!AD!correspond! with!periods!of!increased!storms!identified!from!the!character!of!sediments!in!nearby! Lake!Tutira.!Cyclicity!of!smaller!Na!peaks!in!the!speleothems!appear!to!correspond!with! the!frequency!(ca.!10–15!yr)!of!the!El!Niño!–!La!Nina!cycle.!The!results!of!this!study! indicate! that! Na! concentrations! in! speleothems! hold! considerable! promise! for! reconstructing! paleoWwind! and! Wstorm! conditions! related! to! large! storm! events! and! climate!cycles!that!affect!New!Zealand!and!elsewhere.! ( ( ( ( ( ( ( ( ( (
! vi! Table(of(contents( ! Acknowledgements………………………………………………………………………………………………! Abstract……………………………………………………………………………………………………………….! Preface…………………………………………………………………………………………………………………! ! Chapter(One…………………………………………………………………………………………...………….! 1! 1.0!Introduction!! 1.1#Objective…………………………………………………………………………………..………….! 1! 1.2#Background……………………………………………………………………………….…………# 1! # 1.2.1#Speleothems#formation…………………………………………………………….# 1! # 1.2.2#Speleothem#geochemistry…………………………………………………………! 2# 1.2.3#δ18O#and#δ13C#stable#isotopes…………………………………………………….! 3# # 1.2.4#UraniumDseries#dating………………………………………………………..……! 4! # 1.2.5#Sodium………………………………………………………………….………………..! 5# # 1.2.6#Late#Holocene#climate#and#cycles#in#New#Zealand…..………………….! 5# # 1.2.7#Storm#Events……………………………………………………….………………….! 7# # 1.2.7.1#Historic#storm#events………………………………………………….! 7! # 1.2.7.2#Prehistoric#storm#events……………………………………….…….! 9 ! # # 1.2.8#Structure#of#thesis…………………………………………………..…….! 9! # Chapter(Two……………………………………………………………………………………………………..! 10! 2.0!Methodology…………………………………………………………………………………………………! 10! ! 2.1#Selection#of#speleothems#for#study………………………………………………………….! 10# # 2.2#Speleothem#GG5#(Waitomo)#………………………………………………………..………..! 11# # # 2.2.1#GG5#sample#preparation…………………………………………………………..! 11! # 2.3#Speleothem#DS#(Wairoa)#………………………………………………………………………! 12! ############### 2.3.1#DS#sample#preparation#(DS)……………………………………………..………! 12! # 2.4#Data#collection#techniques…………………………………………………….………………! 13! # # 2.4.1#Laser#ablation#inductively#coupled#plasma#mass#spectrometry……! 13# 2.5!Data!processing!techniques………………………………………………………………….! 15! ! ! 2.6.1!Iolite!data!processing……………………………………………….…………….! 15! ! Chapter(Three…………………………………………………………………………………………………...! 16! 3.0!Results…………………………………………………………………………………………………………..! 16! ! 3.1!Trace!element!data!normalised!to!Ca……………………………………………………! 16! ! 3.2!Trace!element!normalised!to!Mg……………………………………….………………….! 22! ! 3.3!Trace!element!correlations…………………………………………………………………..! 26! ! ! ! ! !
! vii! Chapter(Four……………………………………………………………………………………………………..! 30! 4.0!Discussion……………………………………………………………………………………………………..! 30! ! 4.1!Similarities!and!differences!for!Mg/Ca,!Sr/Ca,!and!Ba/Ca…….………………..! 30! ! 4.2!PaleoWclimate!inferences!from!Mg/Ca,!Ba/Ca!and!Sr/Ca………………….….…! 35! ! 4.3!PaleoWclimate!inferences!from!Na/Ca………………………………………...…………! 37! ! Chapter(Five………………………………………………………………………………………………………! 44! 5.0!Conclusion……………………………………………………………………………………………………..! 44! ! List(of(figures…………………………………………………………………………………………………….! 1. Cave!environment…………………………………………………………………………………….! 2! 2. Uranium!decay!chain………………………………………………………………………………..! 4! 3. El!Niño!wind!anomalies…………………………………………………………………………….! 6! 4. La!Niña!wind!anomalies……………………………………………………………………………! 6! 5. Rainfall!for!New!Plymouth………………………………………………………………………..! 6! 6. Rainfall!for!Napier……………………………………………………………………………………! 7! 7. Landslide!and!soil!erosion!from!cyclone!Bola…………………………………………….! 8! 8. Location!of!DS!and!GG5…………………………………………………………………………….! 10! 9. Cross!section!of!GG5…………………………………………………………………………………! 11! 10. Cross!section!of!DS…………………………………………………………………………………...! 12! 11. ICPWMS!experimental!setup………………………………………………………………………! 14! 12. TimeWseries!of!Na/Ca………………………………………………………………………………..! 16! 13. TimeWseries!of!Mg/Ca………………………………………………………………………………..! 18! 14. TimeWseries!of!Sr/Ca…………………………………………………………………………………! 19! 15. TimeWseries!of!Ba/Ca………………………………………………………………………………..! 20! 16. TimeWseries!of!U/Ca………………………………………………………………………………….! 21! 17. TimeWseries!of!Na/Mg………………………………………………………………………………..! 22! 18. TimeWseries!of!Sr/Mg………………………………………………………………………………...! 23! 19. TimeWseries!of!Ba/Mg………………………………………………………………………………..! 24! 20. TimeWseries!of!U/Mg…………………………………………………………………………………! 25! 21. Mg/Ca!vs!Na/Ca………………………………………………………………………………………..! 27! 22. Sr/Ca!vs!Na/Ca…………………………………………………………………………………………! 28! 23. U/Ca!vs!Na/Ca………………………………………………………………………………………….! 29! 24. TimeWseries!of!Mg/Ca………………………………………………………………………………..! 30! 25. TimeWseries!of!Mg/Ca!for!GG5!&!DS!vs!Nettlebed……………………………………….! 33! 26. TimeWseries!of!Sr/Ca!for!GG5!&!DS!vs!Nettlebed…………………………………………! 34! 27. TimeWseries!of!Mg/Ca………………………………………………………………………………..! 36! 28. TimeWseries!of!Na/Ca………………………………………………………………………………..! 38! 29. Mg/Ca!vs!Na/Ca………………………………………………………………………………………..! 39! 30. Sr/Ca!vs!Na/Ca…………………………………………………………………………………………! 39! 31. U/Ca!vs!Na/Ca………………………………………………………………………………………….! 39! 32. TimeWseries!of!Na/Mg………………………………………………………………………………..! 41! 33. TimeWseries!of!Na/Mg!&!Mg/Ca………………………………………………………………….! 43!
! viii! ! List(of(tables……………………………………………………………………………………………...………! 1. Wind!patterns!record!cyclone!A)!Drena,!B)!Gisele,!C)!Bola!&!D)!Fergus……....! 8! 2. Stormy!periods!from!deposits!in!Lake!Tutira……………………………………………..! 9! 3. Reference!values!for!NIST!SRM610……………………………………………………………! 13! 4. Reference!values!for!NIST!SRM612……………………………………………………………! 13! 5. Pearson!linear!correlation…………………………………………………………………………! 26! 6. Mg,!U,!Ba!&!Sr!concentrations!for!Nettlebed!speleothem…………………………….! 32! 7. Pearson!linear!correlation…………………………………………………………………………! 34! ( References……………………………………………………………………………………..…………………..! 46! ! Electronic(Appendix(One:(Analytical(Data……………………………………..…………………….!( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ! ! ! ! ! !
! 1! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!1! ! 1.0!Introduction!! ! 1.1#Objectives# Historic!climatic!records!in!New!Zealand!only!extend!back!for!the!last!ca.!100!years!(The! National!Climate!Database!(NIWA);!retrieved!15!August!2015).!In!order!to!improve!our! understanding!of!climatic!changes!and!events!beyond!this!timeframe,!it!is!necessary!to! use!quantitative!proxies!of!past!environmental!conditions!and!apply!them!to!dateable! archives! that! can! then! be! used! to! reconstruct! past! environmental! conditions.! Recent! studies! have! shown! that! speleothems! (secondary! cave! carbonate! deposits)! are! important!paleoclimate!archives,!due!to!the!fact!that!speleothems!can!be!reliably!dated,! and! the! composition! of! the! precipitated! carbonate! varies! according! to! external! parameters! and! during! their! systematic! growth.! Speleothems! have! the! potential! to! reconstruct! past! climatic! conditions! at! annual! to! subannual! resolution.! This! study! investigates!the!potential!to!use!speleothem!trace!element!chemistry,!with!a!focus!on! sodium!(Na)!contents,!to!track!wind!conditions!and!storm!events!for!a!period!of!800!yr.! Two!speleothems!have!been!studied!from!two!different!cave!systems!from!(near)!the! west!and!east!coasts!of!the!North!Island!of!New!Zealand!over!the!time!interval!of!0–800! AD.! ! 1.2#Background# # 1.2.1#Speleothem#formation# Speleothems!are!secondary!mineral!deposits!of!calcium!carbonate!formed!on!the!ceiling,! walls! and! floors! of! caves.! The! precipitation! of! speleothems! relies! on! meteoric! water! seeping!through!the!carbonatePrich!lithologies!(limestone)!found!above!caves!(Calaforra! et!al.,!2008).!As!the!water!enters!the!atmosphere!and!seeps!through!the!upper!soil!it! incorporates!carbon!dioxide!from!the!atmosphere!as!well!as!from!the!organic!material! trapped! within! the! soil,! which! makes! the! water! acidic.! The! acidic! water! continues! to! leach! downwards! and! partially! dissolves! carbonatePrich! rocks.! As! the! meteoric! water! enters! the! cave! system,! the! carbon! dioxide! is! lost! to! the! cave’s! atmosphere! and! previously! dissolved! minerals! precipitate! out! to! form! speleothems! (Figure! 1).!
! 2! Speleothems!can!take!various!forms,!depending!on!a!cave’s!internal!atmosphere.!The! water!can!drip,!seep,!condense!or!flow,!which!creates!different!secondary!formations.! The! four! major! formations! include! dripstones,! flowstones,! pore! deposits! and! pool! deposits!(Huang!et!al.,!2001).!The!two!speleothems!in!this!study!are!from!different!caves! with!varying!conditions!and!thus!illustrate!two!different!types!of!speleothems.!GG5!is!a! stalactite! and! grows! downwards! from! the! caves! roof,! whereas! DS! is! a! flowstone! and! grows!as!water!flows!and!leaves!a!film!of!calcite.!These!two!processes!are!illustrated!in! Figure!1.!!! ! # 1.2.2#Speleothem#geochemistry# Speleothems!are!regarded!as!valuable!archives!of!past!climatic!conditions!due!to!their! relatively!simple!geometry,!and!the!fact!that!they!can!be!precisely!dated!(Ma!et!al.,!2010;! Harms! et! al.,! 2008).! The! trace! element! chemistry! and! stable! isotopic! compositions! of! speleothems!can!be!used!to!infer!past!climate!(McDermott,!2004;!Harms!et!al.,!2008).! Study! of! the! youngest! parts! of! speleothems! can! be! used! to! calibrate! the! relationship! between! climate! and! speleothem! chemistry! by! crossPcomparison! with! historic! Figure!1:!Schematic!of!a!typical!cave!environment!illustrating!key!processes!in!the! precipitations!of!speleothems!(adopted!from!Fairchild!et!al.,!2012).! ! Stalagmite) Stalac+te) Soil) Decay)of)plant)li2er)producing)CO2)) Slow)drips)allow) for)degassing)of) CO2))at)the)roof)of) the)cave)to)form)a) stalac+te) Fast)drips))allow) for)degassing)of) CO2)at)the)floor) of)the)cave)to) form)a)stalagmite) Flowstone)) Carbonate)rich) Country)rock) Atmosphere) Plant)respira+on)producing)CO2)
! 3! meteorological!records!from!The!National!Climate!Database!(NIWA).!The!stable!isotopic! compositions! of! speleothems! can! provide! climatic! proxies! for! diverse! environments! including!low!latitude!and!elevation!(Bieniok!et!al.,!2011)!environments!to!high!latitudes! and!elevation!environments!(Cruz!et!al.,!2015:!Orland!et!al.,!2014).! Speleothems! incorporate! minor! and! trace! elements! into! their! calcite! matrix! during! growth.!Stable!oxygen!and!carbon!isotopes!are!common!proxies!that!have!been!applied! in!speleothem!paleoclimate!studies!(McDermott,!2004;!Cruz!et!al.,!2015;!Li!et!al.,!2014),! along! with! some! trace! element! studies! (e.g.,! Mg,! Sr,! Ba! and! U).! These! geochemical! variations!have!been!used!to!reconstruct!regional!changes!in!precipitation,!temperature! and! paleoPvegetation! (Ku! and! Li,! 1998;! McDermott,! 2004).! Mg,! Sr! and! Ba! have! previously!been!used!by,!for!example,!Fairchild!et!al.!(2012),!Orland!et!al.!(2014)!and! Huang!et!al.!(2001)!to!infer!hot–wet!and!cold–dry!periods.!Low!Mg/Ca!ratios!with!high! Sr/Ca!and!Ba/Ca!ratios!characterise!relatively!warmPwet!periods!whereas!the!inverse! signals!coldPdry!periods!(Cross!et!al.,!2015;!Cruz!et!al.,!2015).! ! ! 1.2.3##δ18O#and#δ13C#stable#isotopes# Oxygen!and!carbon!isotopes!have!been!extensively!studied!in!speleothems!in!order!to! interpret! past! climate! events.! For! example,! Frappier! et! al.! (2007)! identified! δ18O! excursions!in!a!stalagmite!extracted!from!a!cave!in!central!Belize.!The!variations!in!δ18O! are!associated!with!11!tropical!cyclone!events.!The!study!achieved!weekly!to!monthly! temporal!resolution!and!found!that!major!negative!δ18O!excursions!coincided!with!the! landfall!of!tropical!cyclones!near!Belize!during!the!period!1977–2000.!This!stalagmite! (ATM7)!was!collected!three!months!after!Hurricane!Keith,!but!the!fingerprint!of!this!was! not! observed! in! the! stalagmite,! suggesting! that! infiltration! rates! cause! a! lag! time! between!such!events!and!their!incorporation!into!speleothems.!This!implication!of!lags! in! the! isotopic! signals! in! speleothems! was! recognised! by! McDermott! (2004)! and! attempts!to!analyse!D/H!ratios!in!fluid!inclusions!trapped!in!speleothems.!A!speleothem! from!Devil’s!Hole!recorded!continuous!δ18O!variations!for!500,000!yr.!These!speleothem! variations! were! shown! to! be! consistent! with! the! Vostok! ice! core! record! and! broadly! delineated! interglacial! and! glacial! periods! using! stable! isotope! data! (Legrand! et! al.,! 1988;!Winograd!et!al.,!1992).! ! !
! 4! ! 1.2.4#UraniumDseries#dating# Speleothems! have! been! established! as! one! of! the! best! terrestrial! archives! for! paleoclimate! reconstruction! as! they! can! be! precisely! dated! by! UPseries! techniques.! UraniumPseries!dating!measures!the!equilibrium!between!238U!and!230Th.!238U!decays!to! 234Th! through! alpha! decay! at! a! rate! of! 4.5! x! 109! yr.! The! decay! continues! through! a! number!of!other!decay!steps!(234Pa;!1.2!min),!(234U;!2.5!x!105!yr)!and!then!further!decays! to! 230Th! (7.7! x! 104! yr)! (Figure! 2)! (Ulusoy! et! al.,! 2014).! UraniumPseries! age! determinations! allow! growth! intervals! and! rates! for! individual! speleothems! to! be! determined!with!exquisite!resolution!(years!to!centuries).#The!banding!in!speleothems! illustrates! variable! periods! of! growth,! with! the! surface! of! the! speleothem! being! the! youngest!age,!and!the!interior!getting!progressively!older!towards!the!centre.!Each!band! can!be!dated!by!measuring!how!much!uranium!has!decayed!into!thorium!(Maher!et!al.,! 2014;!Ulusoy!et!al.,!2014).!The!uranium!from!the!surrounding!bedrock!is!leached!into! the!subsurface!and!is!incorporated!into!the!speleothem!matrix!(Maher!et!al.,!2014).!It!is! presumed!that!there!is!no!initial!230Th.!The!concentration!of!the!daughter!isotope!230Th! is!directly!related!to!the!decay!of!the!parent!isotopes!238U!and!234U!(Ulusoy!et!al.,!2014).! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 238U! 4.5x109! years! 234Th! 24.1! days! 234Pa! 1.17! minutes! !!!234U! 2.4x105! years! !!!230Th! 7.7x104! years! !!!226Ra! 1600! years! Element!! UP!Uranium! ThP!Thorium! PaP!Protactinium! RaP!Radium! α" α"α" β" β" Figure!2:!Uranium!238!decay!chain!(adopted!from!Ulusoy!et!al.,! 2014).!
! 5! ! 1.2.5#Sodium#(Na)# New! Zealand! is! a! narrow! and! seaPsurrounded! landmass! and,! as! such,! atmospheric! particles!delivered!to!land!are!strongly!influenced!by!sea!salts!from!marine!aerosols.!The! soluble!Na!in!aerosols!comes!solely!from!sea!salts,!which!are!higher!in!summer!than!in! winter,!and!higher!at!coastal!regions!relative!to!inland!areas!(Wang!and!Shooter,!2001).! Aerosol!concentrations!of!Na!are!strongly!affected!by!wind!direction!and!mildly!affected! by!wind!speed!(Wang!and!Shooter,!2001).!!Atmospheric!Na!is!transported!by!wind!and! is!dissolved!in!precipitation!and!deposited!on!land.!Na!is!thought!to!be!leached!into!the! subsurface! and! groundwater! and! then! may! be! incorporated! in! speleothems! found! in! caves.!Other!possible!sources!of!Na!in!speleothems!could!come!from!rock!surrounding! the! cave! environment.! This! dissolved! Na! from! the! country! rock! would! be! a! constant! background!phenomenon!and!anomalous!concentrations!might!be!able!to!be!inferred! from!wind!and!storm!events!(Bieniok!et!al.,!2011)! ! 1.2.6#Late#Holocene#climate#and#cycles#in#New#Zealand## In! New! Zealand,! El! Niño! and! La! Niña! cycles! significantly! influence! wind! direction.! El! Niño!and!La!Niña!refer!to!opposite!ends!of!a!climate!spectrum!and!are!weather!patterns! that!occur!periodically!across!the!Pacific!Ocean!characterized!by!variable!levels!of!winds! and! rainfall! in! different! parts! of! New! Zealand! (NIWA).! During! an! El! Niño! event,! New! Zealand! summers! tends! to! experience! stronger/more! frequent! winds! from! the! west,! which!typically!leads!to!a!drought!on!the!east!coast!and!more!rain!on!the!west!coast.!In! winter,!southerly!winds!dominate,!bringing!colder!conditions!to!both!the!land!and!the! surrounding! ocean.! In! spring! and! autumn! southwesterly! winds! are! more! common! (Figure!3).!During!El!Niño!it!is!expected!that!summer!periods!will!result!in!higher!Na! aerosols!on!the!west!coast!and!lower!Na!on!the!east!coast.!Similar!inferences!apply!to! spring!and!autumn,!although!in!lower!concentrations.!Winter!periods!should!result!in! low!Na!aerosols!for!both!east!and!west!coasts.!La!Niña!events!have!contrasting!impacts! on! New! Zealand's! climate.! Northeasterly! winds! dominate,! which! tend! to! bring! rainy! conditions!to!the!northeast!of!the!North!Island,!and!reduced!rainfall!to!the!south!and! southwest!of!the!South!Island.!During!a!La!Niña!event!Na!aerosols!should!be!higher!on! the!east!coast!relative!to!the!west!coast!(Figure!4).!!
! 6! ! # # # # # # # # # ! In!1997–1998!there!was!a!strong!documented!El!Niño!event!that!caused!severe! droughts!and!floods!in!New!Zealand.!New!Plymouth!on!the!west!coast!of!the!North! Island!had!high!rainfall!events!with!some!days!reaching!a!maximum!rainfall!of!480!mm.! During!this!period,!Napier!on!the!east!coast!on!the!North!Island!had!relatively!very!little! rainfall!with!a!maximum!rainfall!for!a!given!day!of!28!mm.!(The!National!Climate! Database!(NIWA);!retrieved!15!August!2015)!(Figures!5!and!6).! # # Figure!3:!Typical!El!Niño!wind! anomalies!(adopted!from!NIWA).! Figure!4:!Typical!La!Niña!wind! anomalies!(adopted!from!NIWA).! Figure!5:!Rainfall!pattern!for!New!Plymouth!(west!coast)!during!the!1997–1998!El!Niño! event!(The!National!Climate!Database!(NIWA);!retrieved!15!August!2015).! 0" 100" 200" 300" 400" 500" 17/12/95" 4/07/96" 20/01/97" 8/08/97" 24/02/98" 12/09/98" 31/03/99" 17/10/99" Precipita)on,(mm), Date,
! 7! # # 1.2.6#Storm#events# 1.2.6.1%Historic%storm%events%% Between! December! and! April,! storms! from! the! tropics! move! south! towards! New! Zealand.! As! these! storms! reach! New! Zealand! waters,! they! bring! damaging! winds! and! heavy!rain.!In!April!1968,!Tropical!Cyclone!Gisele!moved!over!New!Zealand,!producing! winds!gusting!to!75!m/s!in!Wellington!(Sinclair,!1993).!Cyclone!Bola!precipitated!over! 900! mm! of! rain! and! produced! hurricanePforce! winds! in! regions! of! northern! New! Zealand! in! March! 1988! (Sinclair,! 1993),! More! recently,! Cyclones! Fergus! and! Drena! brought!heavy!rain!and!stormPforce!winds!to!the!North!Island!in!December!1996.!New! Zealand’s! climatic! records! of! such! events! are! stored! on! a! National! Climate! Database! (CliFlo).!CliFlo!is!a!web!system!and!stores!climatic!records!from!as!early!as!1850.!CliFlo! generates! outputs! that! are! hourly! to! yearly! raw! data.! The! tropical! cyclones! (Drena,! Gisele,!Fergus!and!Bola)!are!recorded!in!CliFlo!as!shown!in!Table!1.! ! !10$ 0$ 10$ 20$ 30$ 40$ 50$ 60$ 70$ 80$ 90$ 100$ 1/01/95$ 20/07/95$ 5/02/96$ 23/08/96$ 11/03/97$ 27/09/97$ 15/04/98$ 1/11/98$ Precipita)on,(mm), Date, Figure!6:!Rainfall!pattern!for!Napier!(east!coast)!during!the!1997–1998!La!Niña!event!(The! National!Climate!Database!(NIWA);!retrieved!15!August!2015).!
! 8! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Table!1:!Cyclones!A)!Drena,!B)!Gisele,!C)!Bola,!and!D)!Fergus!recorded!by!NIWA!using! wind!speed!data!(The!National!Climate!Database!(NIWA);!retrieved!26!June!2015).! ! ! ! ! ! ! ! % % % % % % % % Station Date(NZST) Time(NZST) Speed(m/s) 26/12/96 8:00 0 27/12/96 8:00 3.1 28/12/96 8:00 0 29/12/96 8:00 2.6 30/12/96 8:00 4.6 31/12/96 8:00 6.7 1/01/97 8:00 3.1 2/01/97 8:00 3.6 3/01/97 8:00 0 Whakatane4Aero Station Date(NZST) Time(NZST) Speed(m/s) 1/01/97 8:00 2.6 2/01/97 8:00 2.6 3/01/97 8:00 2.6 4/01/97 8:00 2.6 5/01/97 8:00 6.7 6/01/97 8:00 2.6 7/01/97 8:00 2.6 8/01/97 8:00 2.6 9/01/97 8:00 2.6 10/01/97 8:00 2.6 11/01/97 8:00 15.4 12/01/97 8:00 2.6 13/01/97 8:00 1 14/01/97 8:00 0 Te0Kuiti0High0School Station Date(NZST) Time(NZST) Speed(m/s) 4/03/88 8:00 4.6 5/03/88 8:00 0 6/03/88 9:00 4.6 7/03/88 9:00 6.7 8/03/88 9:00 9.8 9/03/88 9:00 12.4 10/03/88 9:00 2.6 11/03/88 9:00 4.6 12/03/88 9:00 6.7 13/03/88 9:00 4.6 Napier4Nelson4Park Station Date(NZST) Time(NZST) Speed(m/s) 5/04/68 9:00 4.1 6/04/68 9:00 3.1 7/04/68 9:00 2.6 8/04/68 9:00 3.6 9/04/68 9:00 7.7 10/04/68 9:00 2.1 11/04/68 9:00 0.5 12/04/68 9:00 3.1 13/04/68 9:00 3.6 New1Plymouth1Aero A)"Drena"(09"January"1997)" " ! B)"Gisele"(9/10"April"1968)" ! C)"Bola"(4"March"1988)" " " ! D)"Fergus"(30"December"1996)" " " ! Figure,7:"Landslides"and"soil"erosion"on"the"east"coast"of"New" Zealand"after"Cyclone"Bola""(Manatū"Taonga"Ministry"for"Culture" and"Heritage)."
! 9! 1.2.6.2%Prehistoric%storm%events% It!is!difficult!to!identify!prehistoric!storm!events.!However,!storm!events!cause!massive! landslips! and! slides,! which! may! be! recorded! in! geomorphic! and! geological! features! (Figure! 7)! ! (Manatū! Taonga! Ministry! for! Culture! and! Heritage).! A! fraction! of! New! Zealand’s!prehistoric!storm!events!are!recorded!by!lake!sediments!on!the!eastern!side!of! the!North!Island!at!Lake!Tutira.!Lake!Tutira!terrigenous!deposits!are!a!direct!response! to! rainfall! induced! erosion! (Page! et! al.,! 2010).! Sedimentary! cores! were! analysed! and! dated!back!to!ca.!7200!a.!The!cores!contain!very!abrupt!sedimentary!packages!recording! storm! events.! Numerous! stormy! periods! were! recorded! as! listed! in! Table! 2.! This! prehistoric!record!provides!a!template!with!which!to!compare!the!results!of!this!thesis! research.! Storm!Periods!(AD)! Duration!(yr)! 1750–1650! 100! 1570–1540! 30! 1450–1270! 180! 830–680! 150! 550–470! 80! 120–0! 120! ! Table!2:!Storm!periods!identified!from!sedimentary!deposits!in!Lake!Tutira!(Page!et!al.,! 2010).! # # 1.3#Structure#of#thesis# This!thesis!is!structured!and!presented!as!follows:!! Chapter!1!introduces!this!thesis!by!presenting!the!main!objectives!of!this!research.!It! then!provides!a!synthesis!of!relevant!background!material.! Chapter!2!describes!the!samples!that!were!analysed!as!part!of!this!study,!justifies!the! sample! selection,! and! details! the! analytical! methods! that! were! used! to! collect! and! process!the!data.!! Chapter!3!presents!the!geochemical!results!obtained!on!the!two!speleothems.!! Chapter!4!discusses!the!results!in!terms!of!whether!it!is!possible!to!use!the!geochemistry! of!speleothems!to!track!paleoPwind!and!Pstorm!events.!
! 10! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!2!! ! 2.0!Methodology! ! 2.1!Selection!of!the!speleothems!for!study! Two!speleothems!were!selected!from!the!University!of!Auckland!speleothem!collection! according! to! their! geographical! locations! (Figure! 8)! and! age.! Two! speleothems! were! selected! from! the! (near)! west! (Waitomo)! and! east! coast! (Wairoa)! regions! of! North! Island,! New! Zealand,! which! had! previously! been! dated! by! uraniumGseries! techniques.! The! two! study! sites! are! both! warm,! temperate! regions! and! experience! high! average! rainfall,!but!different!wind!patterns.!The!Waitomo!region!experiences!an!average!annual! temperature!of!22.2°C!and!an!average!rainfall!of!1102!mm!per!year.!Wairoa!experiences! an!annual!temperature!of!22.5°C!and!a!slightly!higher!average!rainfall!of!1187!mm!per! year!(Metservice);!retrieved!17!September!2015).!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Figure!8:!Map!of!the!North!Island!showing!the!location!of! speleothem!samples!(grey)!and!major!cyclone!events!(blue).! ! ! 1968% Gisel e% %1988% Bola% ! 1996% Fergus% ! 1996% Dren a% GG5! DS! !!N! 200km!
! 11! 2.2!Speleothem!GG5!(Waitomo)! The!speleothem!GG5!was!collected!by!Prof.!Paul!Williams!in!2005!from!Gardeners!Gut! cave!in!Waitomo!near!the!west!coast!of!North!Island.!!Gardeners!Gut!cave!has!a!passage! length!of!12.2!km!and!is!120–180!m!above!sea!level.!The!cave!is!35!km!inland!and!is! developed!in!gently!dipping!Oligocene!limestones,!overlain!by!Miocene!siltstones!and! volcanic!ash!soils!(P.!Williams,!pers.!comm.).!GG5!was!actively!growing!at!the!time!of! collection!and!is!75!mm!in!length,!with!clear!growth!bands!(P.!Williams,!pers.!comm.).! U/Th!dating!of!the!speleothem!indicates!that!the!interior!dates!back!to!12200!±!300!yr! (Figure!9).!However,!there!is!a!significant!hiatus!in!growth!at!ca.!5000!yr,!marked!by!a! distinct!change!in!the!colour!of!the!growth!bands!at!a!depth!of!45!mm!(Figure!9).!The! outer!45!mm!of!the!speleothem!provides!a!highGresolution!record!from!2300!yr!BP!to! the!modern!day!as!it!was!actively!dripping!at!the!time!of!sampling.! ! 2.2.1!GG5!sample!preparation! GG5! was! prepared! by! cutting! through! the! sample! with! a! diamond! saw! perpendicular! to! the!growth!bands.!It!was!then!mounted!flat!on! a!glass!slide!and!the!surface!was!polished!and! cleaned.!The!smooth!surface!was!microGdrilled,! and! previously! dated! by! U/Th! series! techniques! using! a! thermal! ionisation! mass! spectrometer! (TIMS).! Prior! to! trace! element! analysis! the! surface! of! the! speleothem! was! cleaned! with! methanol! and! preGablated! to! remove! any! surficial! contamination.! The! preG ablated! surface! was! then! reGablated! and! analysed.! ! ! ! ! ! ! Figure!9:!HighGresolution!crossGsectional! view!of!GG5,!showing!clear!growth!bands! with!annotated!uraniumGseries!dates.!! 1.680%ka% 2.012%ka% 2.334%ka% 1.207%ka%
! 12! 2.3!Speleothem!DS!(Wairoa)! The!speleothem!DS!was!collected!by!Prof.!Paul!Williams!in! 1992!from!the!east!coast!of!New!Zealand!in!Disbelief!Cave.! Disbelief!Cave!is!located!in!the!Wairoa!River!catchment!ca.! 29! km! northeast! of! Wairoa! township! in! northern! Hawkes! Bay.!The!cave!is!approximately!120!m!long!and!600!m!above! sea!level!and!developed!in!Late!Pliocene!limestone,!which!is! overlain! by! early! Pleistocene! sediments! (P.! Williams,! pers.! comm.).! DS! is! a! flowstone/shawl! that! was! not! actively! growing!at!the!time!of!collection.!It!has!been!dated!by!TIMS! techniques! to! be! ca.! 7600! yr! BP! in! age! and! the! tip! of! the! speleothem!is!<1000!yr!BP!in!age!! (P.! Williams,! pers.! comm.).! Speleothem! DS! is! 150! mm! in! length! with! clear! growth! bands! throughout! the! sample! (Figure!10).!! ! 2.3.1!DS!sample!preparation! Due!to!this!speleothem!being!very!fragile,!it!was!embedded! in! epoxy! resin,! which! supported! its! structure! prior! to! cutting.! DS! was! then! prepared! by! cutting! through! the! sample! with! a! diamond! saw! perpendicular! to! the! growth! axis,!in!close!proximity!to!the!regions!microGmilled!for!U/Th! series!dating!(Figure!10).!The!sample!was!then!polished!and! cleaned.! DS! was! then! mounted! in! preparation! for! trace! element! analysis.! Prior! to! ablation,! the! surface! of! the! speleothem!was!once!again!cleaned!with!methanol!and!preG ablated!to!minimise!surficial!contamination.!! ! The!time!interval!chosen!for!analysis!in!both!speleothems!is! 0–800! AD,! given! that! both! samples! have! similar! growth! rates!over!this!time!period.!! ! ! Figure!10:!HighGresolution!crossG sectional!view!of!DS!with! annotated!uraniumGseries!dates.!
! 13! ! 2.4!Data!collection!techniques! ! 2.4.1!Laser!ablation!inductively!coupled!plasma!mass!spectrometry! Trace! element! analysis! was! undertaken! by! laser! ablation! inductively! coupled! plasma! mass! spectrometry! (LAGICPGMS)! at! Victoria! University! of! Wellington.! This! system! comprises!a!Resonetics!S155GSE,!193!nm!excimer!laser!ablation!system!coupled!to!an! Agilent!7500!series!ICPMS.!This!is!an!analytical!technique!with!excellent!sensitivity,!high! analytical! throughput! and! high! spatial! resolution.! Calibrated! standards! were! run! as! unknowns!to!monitor!instrumental!drift!and!the!precision!and!accuracy!of!the!ICPGMS! throughout!analytical!sessions.!The!reference!material!used!for!this!study!are!the!NIST! 610!standard,!NIST!612!standard!and!MACS3,!and!reference!data!for!these!standards! were! acquired! from! georem.mpchGmainz.gwdg.de.! Data! for! the! NIST! standards! are! summarized!in!Tables!3!and!4.!NIST!610!standard!was!used!as!the!primary!calibrating! standard,!whereas!NIST!612!was!used!to!confirm!the!accuracy!and!the!precision!of!the! data.! ! NIST!610! Element! Value! Uncertainty! Unit! Ba! 452! 9! µg/g! Mg! 432! 29! µg/g! Na2O! 13.4! 0.3! %m/m! Sr! 515.5! 1! µg/g! U! 461.5! 1! µg/g! ! ! Table!3:!Reference!values!for!NIST!SRM610!(GeoReM,!2015).!! ! NIST!612! Element! Value! Uncertainty! Unit! Ba! 39.3! 0.9! µg/g! Mg! 68! 5.1! µg/g! Na2O! 13.7! 0.3! %m/m! Sr! 78.4! 0.2! µg/g! U! 37.38! 1.2! µg/g! ! ! Table!4:!Reference!values!for!NIST!SRM612!(GeoReM,!2015).!!
! 14! Inductively! coupled! plasma! mass! spectrometry! (ICPGMS)! is! a! technique! capable! of! detecting!metals!and!several!nonGmetals!at!concentrations!as!low!as!one!part!in!1015! (ppq)!on!nonGinterfered!lowGbackground!isotopes.!This!can!be!achieved!by!firing!a!laser! beam!onto!the!surface!of!the!speleothem,!with!the!energy!of!the!laser!beam!transferred! to!the!speleothem!and!causing!material!to!be!removed/ablated.!The!ablated!material!is! transported! by! a! flow! of! helium! gas! passing! through! the! sample! chamber! and! transported!to!an!ICPGMS.!As!the!material!passes!into!the!plasma!of!the!ICPMS,!elements! are!ionized.!The!ions!are!separated!in!the!mass!spectrometer!according!to!their!massGtoG charge!ratio!and!then!detected!and!counted!on!an!electron!multiplier!detector.! ! ! ! ! ! ! ! ! ! ! ! ! Figure!11:!Schematic!of!an!ICPGMS!experimental!setup!(Latkoczy!and!Ghislain,!2006).! ! ! ! ! ! ! ! ! ! ! !
! 15! ! 2.5!Data!processing!techniques! ! 2.5.1!Iolite!data!processing! ! All! the! raw! LAGICPGMS! data! were! processed! using! Iolite! software.! Iolite! is! data! processing!software!used!for!large!mass!spectrometry!datasets!(Paton!et!al.,!2011).!The! data! processing! involves! a! background! correction! as! well! as! normalising! the! trace! element!ratios!from!the!speleothems!to!the!ratios!measured!in!the!NIST!610!standard! relative!to!their!known!values!(Table!3).! !
! 16! !!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!3!! ! 3.0!Results! This! chapter! presents! detailed! geochemical! data! for! the! Wairoa! and! Waitomo! speleothems.!The!data!was!collected!by!ICP=MS!methods!and!processed!using!Iolite!as! described!in!Chapter!Two.! !! 3.1!Trace!element!data!normalised!to!Ca! The!Wairoa!and!Waitomo!speleothems!are!largely!comprised!of!calcium!carbonate!and! thus!the!measured!trace!element!data!are!presented!normalised!to!calcium.!This! technique!is!a!conventional!method!used!in!speleothem!science!(Fairchild!et!al.,!2012;! Huang!et!al.,!2001).!! ! ! Figure!12:!Time=series!of!Na/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From!0–800!AD!Na/Ca!ratios!in!both!the!Wairoa!and!Waitomo!speleothems!have!almost! identical! average! values! (4.34! x! 10–5! and! 4.32! x! 10–5,! respectively).! The! Waitomo! speleothem! has! Na/Ca! ratios! that! vary! from! a! minimum! value! of! 1.59! x! 10=5! ! to! a! maximum!value!of!1.01!x!10–4!!and!there!appears!to!be!cyclical!changes!from!31–110!AD,! 110–142!AD,!142–182!AD!and!182–275!AD.!The!cyclical!variations!are!less!marked!in! 0.00E+00! 2.00E=05! 4.00E=05! 6.00E=05! 8.00E=05! 1.00E=04! 1.20E=04! 1.40E=04! 1.60E=04! 1.80E=04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Na/Ca! Age!(AD)! Waitomo! Na! Wairoa! Na!
! 17! the! period! 275–714! AD.! There! are! distinct! peaks! in! Na/Ca! ratios! in! the! Waitomo! speleothem!at!110!AD,!142!AD,!182!AD,!275!AD!and!714!AD.!Na/Ca!ratios!in!the!Wairoa! speleothem!in!a!general!sense!behave!similarly!to!that!of!the!Waitomo!Speleothem!and! show!cyclical!variation!between!150–227!AD,!227–261!AD,!261–387!AD,!387–557!AD,! 557–750!AD!and!750–768!AD.!There!are!also!distinct!Na/Ca!peaks!at!150!AD,!227!AD,! 261!AD,!387!AD,!557!AD,!750!AD!and!786!AD!in!the!Wairoa!speleothem.!Na/Ca!ratios!in! the!Wairoa!speleothem!vary!from!a!minimum!value!of!2.14!x!10–5!to!a!maximum!value!of! 3.72!x!10–4.!The!Wairoa!speleothem!has!significantly!higher!Na/Ca!peaks!relative!to!the! Waitomo!speleothem.!In!general,!Na/Ca!peaks!in!the!two!speleothems!do!not!occur!at! the!same!time.!However,!there!are!intervals!where!smaller!scale!Na/Ca!peaks!in!the!two! speleothems!do!correlate!(142–153!AD,!173–210!AD,!239–272!AD,!319–341!AD,!511– 531!AD,!547–557!AD,!659–691!AD,!705–760!AD!and!775–800!AD),!and!there!are!also! intervals!where!the!Na/Ca!ratios!in!the!speleothems!appear!to!be!anti=correlated!(52–72! AD,! 76–101! AD,! 115–126! AD,! 153–157! AD,! 227–239! AD,! 269–289! AD,! 363–393! AD,! 479–491!AD,!534–548!AD,!617–647!AD!and!750–775!AD).! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
! 18! ! Figure!13:!Time=series!of!Mg/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From!0–800!AD,!Mg/Ca!ratios!in!both!the!Wairoa!and!the!Waitomo!speleothems!have! very!different!trends!and!values.!The!average!Mg/Ca!value!for!the!Wairoa!speleothem!is! 4.03!x!10–4!and!8.27!x!10–4!for!the!Waitomo!speleothem.!The!Waitomo!speleothem!has!a! minimum!value!of!3.71!x!10–5!and!a!maximum!value!of!1.12!x!10–3.!From!0–400!AD,! Mg/Ca!ratios!in!the!Waitomo!speleothem!increase!substantially!and!then!at!460!AD!the! Mg/Ca!ratios!drop!from!1.06!x!10–3!to!6.73!x!10–4.!!After!the!drop,!Mg/Ca!ratios!increase! back! to! 1.03! x! 10–3! for! ~90! years! where! the! Mg/Ca! values! stabilise! and! show! less! variability!until!800!AD.!There!is!no!clear!evidence!for!cyclicity!in!the!Mg/Ca!ratios!of! the! Waitomo! speleothem.! However,! Mg/Ca! ratios! in! the! Wairoa! speleothem! show! clearer!cyclical!trends.!The!Wairoa!speleothem!has!a!minimum!Mg/Ca!value!of!3.09!x! 10–4!and!a!maximum!value!of!7.02!x!10–4!and!peaks!at!52!AD,!154!AD,!257!AD,!384!AD,! 518! AD,! 647! AD,! 693! AD! and! 774! AD.! The! two! Mg/Ca! trends! from! the! different! speleothems!are!not!well!correlated,!and!do!not!show!similar!trends!or!spikes.! ! 4.00E=04! 5.00E=04! 6.00E=04! 7.00E=04! 8.00E=04! 9.00E=04! 1.00E=03! 1.10E=03! 1.20E=03! 2.80E=04! 3.80E=04! 4.80E=04! 5.80E=04! 6.80E=04! 7.80E=04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Mg/Ca! Age!(AD)! Wairoa! Mg! Waitomo! Mg!
! 19! ! Figure!14:!Time=series!of!Sr/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From!0–800!AD,!Sr/Ca!ratios!in!both!the!Wairoa!and!the!Waitomo!speleothems!have! significantly! different! average! values! (3.42! x! 10–4! and! 1.04! x! 10–4,! respectively).! Waitomo!Sr/Ca!values!varies!from!a!minimum!value!of!3.77!x!10–5!to!a!maximum!value! of! 1.91! x! 10–4! and! there! are! no! clear! cyclical! changes.! In! the! Waitomo! speleothem! between! 0–350! AD! there! is! more! variation! in! Sr/Ca! ratios! over! shorter! timesclaes! relative! to! 350–800! AD! where! varations! tend! to! be! more! muted.! Sr/Ca! ratios! in! the! Wairoa!speleothem!vary!from!a!minimum!value!of!1.66!x!10–4!to!a!maximum!value!of! 4.73! x! 10–4.! The! Wairoa! speleothem! has! higher! Sr/Ca! ratios! relative! to! the! Waitomo! speleothem.! In! general,! the! trends! for! the! two! speleothems! show! some! degree! of! correlation.! There! appear! to! be! common! trends! for! the! two! speleothems,! with! the! exception!of!between!400–500!AD,!at!0–100!AD,!120–242!AD,!250–400!AD,!500–650!AD! and!650–800!AD.!! ! ! ! ! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 0.00E+00! 1.00E=04! 2.00E=04! 3.00E=04! 4.00E=04! 5.00E=04! 6.00E=04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Sr/Ca! Age!(AD)! Wairoa! Sr! Waitomo! Sr!
! 20! ! Figure!15:!Time=series!of!Ba/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From! 0–800! AD,! Ba/Ca! ratios! in! both! the! Wairoa! and! Waitomo! speleothems! have! significantly! different! average! values! (9.49! x! 10–6! and! 2.82! x! 10–5,! respectively).! The! Waitomo! speleothem! shows! a! slight! trend! to! lower! Ba/Ca! ratios! with! time! that! vary! from!a!minimum!value!of!7.33!x!10–6!to!a!maximum!value!of!5.28!x!10–5.!The!Waitomo! speleothem!shows!slight!cyclical!variations!with!large!peaks!at!75!AD!and!250!AD,!and! smaller!peaks!at!417!AD,!507!AD,!580!AD,!640!AD!and!730!AD.!At!690!AD,!Ba/Ca!ratios! drop!from!2.4!x!10–5!to!7.33!x!10–6!and!steeply!increase!back!to!2.9!x!10–5.!The!Wairoa! speleothem! has! a! slight! increase! in! Ba/Ca! values! through! time! that! vary! from! a! minimum! value! of! 3.48! x! 10–6! to! a! maximum! value! of! 1.67! x! 10–5.! The! Wairoa! speleothem!has!stronger!cyclical!variations!than!that!of!the!Waitomo!speleothem,!with! peaks!in!Ba/Ca!at!90!AD,!180!AD,!265!AD,!310!AD,!357!AD,!435!AD,!547!AD,!622!AD,!684! AD,!714!AD!and!782!AD.!There!are!some!similarities!in!the!data!for!the!two!speleothems! whereby!some!peaks!and!lows!correlate!(e.g.,!67–157!AD!and!693–794!AD).! ! ! ! ! ! ! 0.00E+00! 1.00E=05! 2.00E=05! 3.00E=05! 4.00E=05! 5.00E=05! 6.00E=05! 0.00E+00! 5.00E=06! 1.00E=05! 1.50E=05! 2.00E=05! 0! 100! 200! 300! 400! 500! 600! 700! 800! Ba/Ca! Age!(AD)! Wairoa!Ba! Waitomo! Ba!
! 21! ! Figure!16:!Time=series!of!U/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! Average!U/Ca!ratios!in!the!Waitomo!and!Wairoa!speleothems!are!very!different!(6.87!x! 10–8!versus!5.23!x!10–7).!The!Wairoa!speleothem!has!a!wider!range!of!U/Ca!ratios!with!a! minimum!value!of!1.15!x!10–7!and!a!maximum!value!of!8.76!x!10–7!and!exhibits!very! noisy!variations.!There!are!some!clear!U/Ca!peaks!(72!AD,!150!AD,!196!AD,!267!AD,!307! AD,!383!AD,!429!AD,!552!AD,!637!AD,!677!AD!and!753!AD)!and!lows!(109!AD,!149!AD,! 208! AD,! 283! AD,! 328! AD,! 397! AD,! 518! AD,! 580! AD! and! 694! AD).! The! Waitomo! speleothem!has!lower!U/Ca!values!than!that!of!the!Wairoa!speleothem!with!a!smaller! range!in!values!from!1.51!x!10–4!to!22!x!10–7.!There!is!a!period!at!660!AD!where!U/Ca! values!in!the!Waitomo!speleothem!increase!significantly!to!4.22!x!10–7,!but!most!peak! U/Ca! values! are! ca.! 1! x! 10–7.! U/Ca! in! the! two! speleothems! do! not! appear! to! exhibit! similar!trends.! ! ! ! ! ! ! ! ! ! 0.00E+00! 5.00E=08! 1.00E=07! 1.50E=07! 2.00E=07! 2.50E=07! 0.00E+00! 2.00E=07! 4.00E=07! 6.00E=07! 8.00E=07! 1.00E=06! 0! 100! 200! 300! 400! 500! 600! 700! 800! U/Ca! Age!(AD)! Wairoa!U! Waitomo! U!
! 22! ! 3.2!Trace!elements!normalised!to!Mg! Trace!element!data!for!the!Wairoa!and!Waitomo!speleothems!were!also!normalised!to! Mg!to!examine!how!variations!with!respect!to!this!element!changed!over!time.!! ! ! Figure!17:!Time=series!of!Na/Mg!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).!! ! From!0–800!AD,!Na/Mg!ratios!in!the!Wairoa!speleothem!have!a!slightly!higher!average! value! than! the! Waitomo! speleothem! (1.05! x! 10–1! versus! 5.32! x! 10–2).! The! Waitomo! speleothem!varies!from!a!minimum!value!of!2.51!x!10–2!to!a!maximum!value!of!1.4!x!10–1! and!there!appears!to!be!cyclical!changes!between!31–105!AD,!105–134!AD,!134–142!AD,! 142–182!AD!and!182–275!AD.!The!cyclical!variations!are!less!marked!in!the!period!275– 720!AD.!There!are!distinct!peaks!in!Na/Mg!ratios!for!the!Waitomo!speleothem!at!110! AD,! 142! AD,! 182! AD,! 275! AD! and! 714! AD.! Na/Mg! ratios! in! the! Wairoa! speleothem! behave! similarly! to! the! Waitomo! speleothem,! in! that! it! shows! cyclical! variations! between!150–227!AD,!227–261!AD,!261–!325!AD,!325–387!AD,!387–557!AD,!557–750! AD!and!750–768!AD.!There!are!also!distinct!peaks!at!227!AD,!261!AD,!387!AD,!557!AD,! 750! AD! and! 786! AD.! The! Waitomo! speleothem! has! Na/Ca! ratios! that! vary! from! a! minimum!value!of!6.02!x!10–2!to!a!maximum!value!of!9.58!x!10–1!and!has!significantly! higher!Na/Ca!peaks!relative!to!the!Waitomo!speleothems.!In!general!the!timing!of!the! peaks!in!the!two!speleothems!do!not!correspond!with!each!other.! 0.00E+00! 2.00E=02! 4.00E=02! 6.00E=02! 8.00E=02! 1.00E=01! 1.20E=01! 1.40E=01! 1.60E=01! 0.00E+00! 2.00E=01! 4.00E=01! 6.00E=01! 8.00E=01! 1.00E+00! 1.20E+00! 0! 100! 200! 300! 400! 500! 600! 700! 800! (Na/Mg)! Age!(AD)! Wairoa! Na! Waitomo! Na!
! 23! ! Figure! 18:! Time=series!of!Sr/Mg!ratios!in!the!two!speleothems!GG5!(Waitomo;!blue)! and!DS!(Wairoa;!red).! ! From!0–800!AD,!Sr/Mg!ratios!in!both!the!Wairoa!and!the!Waitomo!speleothems!have! significantly! different! average! values! (8.65! x! 10–1! and! 1.27! x! 10–1,! respectively).! The! Waitomo!speleothem!has!Sr/Ca!ratios!that!vary!from!a!minimum!value!of!5.57!x!10–2!to! a! maximum! value! of! 3.12! x! 10–1! and! there! are! no! apparent! cyclical! changes.! In! the! Waitomo!speleothem!between!0–350!AD!there!is!more!variation!over!shorter!timescales! relative!to!350–800!AD!where!varations!tend!change!more!gradually.!Sr/Mg!ratios!in!the! Wairoa!speleothem!vary!from!a!minimum!value!of!3.85!x!10–1!to!a!maximum!value!of! 1.46.! Wairoa! has! higher! Sr/Mg! ratios! relative! to! that! of! the! Waitomo! speleothem.! In! general,! the! trends! of! the! two! speleothem! show! some! degree! of! correlation.! There! appear!to!be!common!trends!for!the!two!speleothems!with!the!exception!of!between!0– 100!AD,!120–242!AD!and!650–800!AD.!! ! ! ! ! ! ! 0.00E+00! 5.00E=02! 1.00E=01! 1.50E=01! 2.00E=01! 2.50E=01! 3.00E=01! 3.50E=01! 0.00E+00! 2.00E=01! 4.00E=01! 6.00E=01! 8.00E=01! 1.00E+00! 1.20E+00! 1.40E+00! 1.60E+00! 0! 100! 200! 300! 400! 500! 600! 700! 800! (Sr/Mg)! Age!(AD)! Wairoa!Sr! Waitomo! Sr!
! 24! ! Figure! 19:! Time=series!of!Ba/Mg!ratios!in!the!two!speleothems!GG5!(Waitomo;!blue)! and!DS!(Wairoa;!red).! ! From!0–800!AD,!Ba/Mg!ratios!in!both!the!Wairoa!and!Waitomo!speleothems!have!very! similar! average! values! (2.32! x! 10–2! and! 3.51! x! 10–2,! respectively).! The! Waitomo! speleothem! has! a! slight! negative! trend! in! Ba/Mg! ratios! with! time! that! vary! from! a! minimum!value!of!1.11!x!10–2!to!a!maximum!value!of!1.00!x!10–1.!Waitomo!shows!slight! cyclical!variations!with!large!Ba/Ca!peaks!at!75!AD,!200!AD,!250!AD!and!269!AD!and! smaller!peaks!at!450!AD,!507!AD,!580!AD,!640!AD!and!730!AD.!The!Wairoa!speleothem! has!a!slight!increase!in!Ba/Mg!values!through!time!that!vary!from!a!minimum!value!of! 8.14! x! 10–3! to! a! maximum! value! of! 5.20! x! 10–2.! The! Wairoa! speleothem! has! stronger! cyclical!variations!in!Ba/Ca!ratios!than!in!the!Waitomo!speleothem,!with!peaks!at!34!AD,! 108!AD,!117!AD,!180!AD,!276!AD,!310!AD,!357!AD,!435!AD,!547!AD,!615!AD,!680!AD,!714! AD!and!782!AD.!! ! ! ! ! ! ! ! ! ! 0.00E+00! 2.00E=02! 4.00E=02! 6.00E=02! 8.00E=02! 1.00E=01! 1.20E=01! 0! 100! 200! 300! 400! 500! 600! 700! 800! (Ba/Mg)! Age!(AD)! Waitomo! Ba! Wairoa! Ba!
! 25! ! Figure!20:!Time=series!of!U/Mg!ratios!in!the!two!speleothems!GG5!(Waitomo;!blue)!and! DS!(Wairoa;!red).!! ! Average!U/Mg!ratios!in!the!Waitomo!and!Wairoa!speleothems!are!very!different!(8.43!x! 10–5!versus!1.27!x!10–3).!Wairoa!has!a!wider!range!of!U/Ca!ratios!with!a!minimum!value! of!2.45!x!10–4!and!a!maximum!value!of!2.46!x!10–3!and!exhibits!very!noisy!variations.! There!are!some!clear!peaks!(96!AD,!129!AD,!189!AD,!267!AD,!307!AD,!356!AD,!460!AD,! 552!AD,!622!AD,!677!AD!and!753!AD)!and!lows!(37!AD,!109!AD,!159!AD,!220!AD,!283! AD,!328!AD,!391!AD,!518!AD,!554!AD,!694!AD!and!767!AD)!in!U/Ca!ratios.!The!Waitomo! speleothem!has!lower!U/Mg!ratios!than!the!Wairoa!speleothem!with!a!smaller!range!of! values!from!2.04!x!10–5!!!to!4.76!x!10–4.!There!is!a!period!at!660!AD!where!U/Mg!values! increase!significantly!to!4.76!x!10–4,!but!most!peak!U/Mg!values!are!ca.!1!x!10–4.!U/Mg! ratios!in!the!two!speleothems!do!not!appear!to!exhibit!similar!trends.! ! ! ! ! ! ! ! ! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 0.00E+00! 5.00E=04! 1.00E=03! 1.50E=03! 2.00E=03! 2.50E=03! 3.00E=03! 0! 100! 200! 300! 400! 500! 600! 700! 800! (U/Mg)! Age!(AD)! Wairoa!U! Waitomo! U!
! 26! ! 3.3!Trace!element!correlations! The!following!section!presents!Pearson’s!linear!correlations!between!trace!element!data! in!the!speleothems.!The!Pearson’s!linear!correlation!coefficient!is!a!statistical!measure!of! the!strength!of!a!linear!relationship!between!paired!data.!The!closer!the!value!is!to!1!or!– 1,!the!stronger!the!correlation!between!two!elements.!!Pearson’s!linear!correlation!(R2)! defines!values!of!±0!to!±0.19!as!very!weak,!±0.20!to!±0.39!as!weak,!±0.40!to!±0.59!as! moderate,! ±0.60! to! ±0.79! as! strong! and! ! ±0.80! to! ±1! as! very! strong! correlations.!! Elements! with! strong! correlations! suggest! that! similar! processes! control! their! variability.!! ! !! Na/Ca! Mg/Ca! Sr/Ca! Ba/Ca! U/Ca! Na/Ca! 1! (VW)!!!!! 0.05132! (VW)!!!!! 0.03193! (VW)!!! 0.12207! (W)!!!!!!!! 0.23617! Mg/Ca! (VW)!!!!! 0.08311! 1! (VW)!!!= 0.11014! (W)!!!!= 0.33975! (VW)!!!!= 0.12718! Sr/Ca! (VW)!!!!= 0.00287! (VW)!!!!= 0.11608! 1! (VS)!!!!! 0.83152! (W)!!!!!!!! 0.33829! Ba/Ca! (VW)!!!!! 0.10882! (M)!!!!!!= 0.42067! (VS)!!!!!!! 0.85081! 1! (W)!!!!!!!! 0.35519! U/Ca! (W)!!!!!!!! 0.26525! (VW)!!!!!!!! 0.1521! (W)!!!!!!= 0.21277! (VW)!!= 0.02331! 1! Table! 5:! Pearson!linear!correlation!table!for!elemental!ratios!in!the!two!speleothems! (GG5!=!blue;!DS!=!red)!(VW!=!very!weak,!W!=!weak,!M!=!moderate!and!VS!=!strong).! ! None!of!the!elements!correlate!strongly!except!for!Sr/Ca!and!Ba/Ca!(Waitomo!–!0.85;! Wairoa!–!0.83).!A!weak!positive!correlation!is!observed!in!the!Wairoa!speleothem!for! U/Ca!with!Sr/Ca!and!Ba/Ca!(0.34!and!0.36)!and!a!weak!negative!correlation!for!Ba/Ca! with! Mg/Ca! (–0.34).! ! A! weak! negative! correlation! is! observed! in! the! Waitomo! speleothem!for!Ba/Ca!and!Mg/Ca!(–0.42).!There!are!no!element!ratios!that!have!a!strong! or!moderate!correlation!with!Na/Ca,!although!a!weak!correlation!is!exhibited!between! Na/Ca!and!U/Ca!in!both!speleothems.! ! !
! 27! ! Figure!21:!Mg/Ca!versus!Na/Ca!ratios!for!speleothem!DS!from!Wairoa.! ! The! R2! (0.05)! value! for! Mg/Ca! and! Na/Ca! illustrates! that! there! is! no! statistical! correlation!between!the!two!ratios.!However,!qualitatively!there!appears!to!be!a!cluster! of!values!for!Na/Ca!from!2.43!x!10–5!to!6.58!x!10–5!and!Mg/Ca!from!3.15!x!10–4!to!5.53!x! 10–4.!! ! ! ! ! ! ! ! 0.00E+00! 2.00E=04! 4.00E=04! 6.00E=04! 8.00E=04! 1.00E=03! 1.20E=03! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 3.50E=04! 4.00E=04! Mg/Ca! Na/Ca! Wairoa!
! 28! ! Figure!22:!Sr/Ca!versus!Na/Ca!ratios!for!speleothem!DS!from!Wairoa.!! ! The!R2!(0.03)!value!for!Sr/Ca!and!Na/Ca!illustrate!that!there!is!no!statistical!correlation! between!the!two!ratios.!However,!qualitatively!there!appears!to!be!a!cluster!of!values!for! Na/Ca!from!2.44!x!10–5!to!6.62!x!10–5!and!Sr/Ca!from!1.88!x!10–4!to!5.16!x!10–4.! ! ! ! ! ! ! 0.00E+00! 1.00E=04! 2.00E=04! 3.00E=04! 4.00E=04! 5.00E=04! 6.00E=04! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 3.50E=04! 4.00E=04! Sr/Ca! Na/Ca! Wairoa!
! 29! ! ! Figure!23:!U/Ca!versus!Na/Ca!ratios!for!speleothem!DS!from!Wairoa.! ! The! R2! (0.2)! value! for! U/Ca! and! Na/Ca! illustrates! that! there! is! statistically! a! weak! correlation!between!the!two!ratios,!which!is!also!evident!from!Fig.!25.!There!appears!to! be!a!cluster!of!values!for!Na/Ca!from!2.38!x!10–5!to!7.62!x!10–5!and!U/Ca!from!2.09!x!10–7! to!8.66!x!10–7.! 0.00E+00! 2.00E=07! 4.00E=07! 6.00E=07! 8.00E=07! 1.00E=06! 1.20E=06! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 3.50E=04! 4.00E=04! U/Ca! Na/Ca! Wairoa!
! 30! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!4!! ! 4.0!Discussion! The! trace! elements! magnesium! (Mg),! strontium! (Sr)! and! barium! (Ba)! have! been! measured!routinely!in!speleothem!studies!worldwide!(Fairchild!et!al.,!2012;!Orland!et! al.,! 2014;! Huang! et! al.,! 2001).! The! chemistry! of! these! three! elements! is! quite! well! understood! and! much! is! known! about! what! controls! their! incorporation! into! speleothems.! As! such,! this! discussion! first! focuses! on! the! similarities! and! differences! observed!between!the!two!speleothems!with!regards!to!Mg,!Sr!and!Ba.!It!then!continues! by!focusing!on!paleoclimatic!interpretations!from!Mg,!Sr!and!Ba.!The!last!section!of!this! discussion!then!explores!the!main!focus!of!this!thesis!by!examining!if!Na!can!be!used!to! track!paleoNstorm!and!Nwind!events.! ! 4.1!Similarities!and!differences!in!Mg/Ca,!Sr/Ca,!and!Ba/Ca!values!in!Waitomo!and! Wairoa!speleothems! ! Figure!24:!TimeNseries!of!Mg/Ca!ratios!for!the!speleothems!GG5!(Waitomo;!blue)!and! DS!(Wairoa;!red).! ! ! ! ! 4.00EN04! 5.00EN04! 6.00EN04! 7.00EN04! 8.00EN04! 9.00EN04! 1.00EN03! 1.10EN03! 1.20EN03! 2.80EN04! 3.80EN04! 4.80EN04! 5.80EN04! 6.80EN04! 7.80EN04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Mg/Ca! Age!(AD)! Wairoa! Mg! Waitomo! Mg!
! 31! The! firstNorder! observation! for! the! Mg/Ca! record! in! the! two! speleothems! is! that! the! Waitomo!speleothem!has!significantly!higher!Mg!concentrations!as!compared!with!that! of!the!Wairoa!speleothem.!The!Waitomo!speleothem!has!a!higher!average!Mg/Ca!of!8.3!x! 10N4,! whereas! the! average! Mg/Ca! ratio! in! the! Wairoa! speleothem! is! 4.0! x! 10N4.! The! difference!in!this!ratio!could!be!due!to!differences!of!the!two!sites!in!terms!of:! 1. The!depth!of!the!cave!(hydrology).! 2. The!amount!of!precipitation!(climate).! As!meteoric!water!percolates!through!the!rocks!overlying!a!cave!it!incorporates!Mg.!If! there!is!less!precipitation!it!takes!longer!for!the!water!to!percolate!through!the!overlying! rocks!and!thus!higher!Mg/Ca!ratios!are!expected.!The!same!process!can!be!envisaged!to! occur! for! deeper! cave! systems,! as! the! meteoric! water! has! to! pass! through! a! greater! volume! of! overlying! rock! and,! therefore,! the! deeper! the! cave,! the! higher! the! Mg/Ca! values.!The!annual!rainfall!at!Waitomo!is!1102!mm/yr!and!Wairoa!has!a!similar!average! rainfall!of!1187!mm/yr!(Metservice);!retrieved!17!September!2015).!When!Prof.!Paul! Williams!collected!the!Waitomo!(GG5)!and!Wairoa!(DS)!speleothems!he!noted!that!the! Waitomo! cave! was! 50! m! below! the! surface,! whereas! the! Wairoa! cave! was! just! 10! m! below! the! surface.! The! annual! rainfalls! for! Waitomo! and! Wairoa! are! less! than! 10%! different!and!are!broadly!similar,!thus!the!different!average!Mg/Ca!ratios!for!Waitomo! (GG5)!and!Wairoa!(DS)!most!likely!reflects!cave!depth,!rather!than!regional!climate!(i.e.,! precipitation)!variations.!! !! A!secondNorder!observation!of!the!Mg/Ca!record!for!the!two!speleothems!is!that!there! are!cyclical!variations!superimposed!on!these!larger!scale!differences!in!Mg/Ca!values.! Mg/Ca! ratios! in! the! Wairoa! speleothem! show! clear! cyclical! variations! with! distinct! peaks,!whereas!the!Mg/Ca!ratios!in!the!Waitomo!speleothem!do!not!show!clear!cyclical! changes.!The!Mg/Ca!ratios!in!the!Wairao!speleothem!have!an!average!cyclical!time!of!ca.! 100!yr!between!the!peaks!(50–154!AD,!154–270!AD,!270–380!AD,!380–520!AD,!520– 660! AD,! 660–700! AD! and! 700–770! AD).! The! absence! of! cyclical! variations! in! Mg/Ca! ratios!in!the!Waitomo!speleothem!may!be!due!to:!! 1. A!more!stable!regional!climate!at!Waitomo!as!compared!with!Wairoa.! 2. The!sensitivity!of!the!cave’s!hydrological!system!to!overlying!changes!in!regional! climate!such!as!mean!annual!rainfall.!
! 32! The!Wairoa!and!Waitomo!regions!are!not!located!far!away!from!each!other!(Figure!8).! Events! that! affect! the! amount! of! precipitation! and! wind! such! as! El! Niño! and! La! Niña! events!should!be!recorded!in!both!speleothems.!With!prehistoric!storm!events!recorded! in!Lake!Tutira!(Page!et!al.,!2010)!and!historic!wind!anomalies!recorded!by!the!National! Climate!Database!it!is!clearly!evident!that!climate!varies!and!has!not!been!stable!over! the!course!of!the!period!0N800!AD.!Variations!in!Mg/Ca!for!each!speleothem!are!most! likely!responses!to!climate!variations.!However,!the!Wairoa!speleothem!appears!to!be!a! more! sensitive! archive! that! better! records! climatic! change! relative! to! the! Waitomo! speleothem.! Again,! this! sensitivity! may! be! a! reflection! of! the! Wairoa! cave! being! a! shallower!system!than!that!at!Waitomo.! ! Hellstrom! et! al.! (2000)! carried! out! an! ICPNMS! trace! element! study! of! a! speleothem,! which!was!a!flowstone!collected!from!a!deep!cave!system!200!m!below!the!surface!on! the! west! coast! of! the! South! Island,! New! Zealand! in! Nettlebed! cave.! The! speleothem! covered! 30,000! yr! of! growth! and! thus! showed! trace! element! (Mg,! Sr,! Ba! and! U)! variations!between!glacial!and!interglacial!periods.!Hellstrom!et!al.!(2000)!found!that! trace!element!chemistry!showed!glacial!conditions!rapidly!ended!around!15,000!yr!BP.! This!change!from!glacial!to!interglacial!conditions!is!marked!by!increases!and!decreases! in!different!trace!elements.!During!the!glacial!period!there!are!relatively!higher!Mg!and! U!concentrations!and!relatively!lower!Ba!and!Sr!concentrations.!! ! ! ! Glacial! ! Interglacial! Change!in!magnitude!from!glacial! to!interglacial!period! Concentration! Normalised! to!Ca! Concentratio n! Normalised! to!Ca! Concentratio n! Normalised! to!Ca! Percentage! Mg! 470!ppm!! 1.2!x!10N3! 340!ppm! 8.5!x!10N4! 130!ppm! 3.3!x!10J4! 38.8%! U! 125!ppb! 3.1!x!10N7! 55!ppb! 1.4!x!10N7! 70!ppb! 1.8!x!10J7! 128.6%! Ba! 1900!ppb! 4.8!x!10N6! 3000!ppb! 7.5!x!10N6! 1100!ppb! 2.8!x!10J6! 37.3%! Sr! 25!ppm! 6.3!x!10N5! 36!ppm! 9.0!x!10N5! 11!ppm! 2.8!x!10J5! 31.1%! Table! 6:! Mg,! U,! Ba! and! Sr! concentrations! and! element/Ca! ratios! in! a! South! Island! speleothem.!Highlighted!values!show!the!change!from!glacial!conditions!to!interglacial! conditions!for!this!relatively!deep!cave!system!(adopted!from!Hellstrom!et!al.,!2000).!!
! 33! ! Figure!25:!TimeNseries!of!Mg/Ca!ratios!for!the!speleothems!GG5!(Waitomo;!blue)!and! DS!(Wairoa;!red).!Also!shown!are!the!magnitude!of!the!glacial!and!interglacial!changes!in! Mg/Ca!values!from!a!South!Island!(Nettlebed)!speleothem!(Hellstrom!et!al.,!2000).! ! The! Nettlebed! speleothem! shows! significant! Mg/Ca! variations! associates! with! large! climate! variations! from! the! most! recent! glacial! to! interglacial! period.! The! Waitomo! speleothem!has!similar!average!Mg/Ca!values!to!the!Nettlebed!speleothem.!The!largest! change!in!Mg/Ca!values!for!the!Waitomo!speleothem!is!3.5!x!10N4!and!for!the!Wairoa! speleothem! is! 2.4! x! 10N4.! These! changes! are! broadly! similar! in! magnitude! to! those! observed! in! the! Nettlebed! speleothem,! despite! the! fact! that! both! the! Waitomo! and! Wairoa!speleothems!grew!wholly!within!the!Holocene!(0–800!AD).!For!some!reason,!the! chemistry! of! the! Waitomo! and! Wairoa! speleothems! are! more! sensitive! to! change! in! climate! than! the! Nettlebed! speleothem.! A! plausible! reason! for! the! large! variations! in! Mg/Ca! ratios! for! the! Waitomo! and! Wairoa! speleothems! is! that! they! reflect! more! sensitive!recorders!to!climate!variations!due!to!their!relative!shallow!cave!depth!relative! to! the! Nettlebed! speleothem.! Similar! size! magnitude! variations! are! observed! in! the! Nettlebed!speleothem,!which!is!known!to!cover!large!climate!variations!between!glacial! and!interglacial!periods!(Hellstrom.,!et!al,!2000).!!! ! ! ! ! 4.00EN04! 5.00EN04! 6.00EN04! 7.00EN04! 8.00EN04! 9.00EN04! 1.00EN03! 1.10EN03! 1.20EN03! 2.80EN04! 3.80EN04! 4.80EN04! 5.80EN04! 6.80EN04! 7.80EN04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Mg/Ca! Age!(AD)! Wairoa! Mg! Waitomo! Mg! 28.2%! 41.1%! Glacial!value:!1.2$x$10 '3$ !!! Interglacial!value:!8.5$x$10 '4$ Magnitude$change:$38.8%!
! 34! !! Na/Ca! Mg/Ca! Sr/Ca! Ba/Ca! U/Ca! Na/Ca! 1! 0.05! 0.03! 0.12! 0.24! Mg/Ca! 0.08! 1! –0.11! –0.34! N0.13! Sr/Ca! –0.00! N0.12! 1! 0.83! 0.34! Ba/Ca! 0.11! –0.42! 0.85! 1! 0.36! U/Ca! 0.27! 0.15! –0.21! –0.02! 1! Table! 7:! Pearson! linear! correlation! table! for! selected! element/Ca! ratios! in! the! two! studied!speleothems!(GG5!=!blue;!DS!=!red).! ! Sr/Ca! and! Ba/Ca! are! well! correlated! in! both! the! Waitomo! and! Wairoa! speleothems! (Table!7).!As!such,!discussion!of!Sr/Ca!ratios!can!be!combined!with!that!for!Ba/Ca!ratios.!! ! ! Figure!26:!TimeNseries!of!Sr/Ca!ratios!for!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).!! ! The!Waitomo!and!Wairoa!speleothems!have!very!different!Sr!concentrations!compared! with! the! Nettlebed! speleothem.! However,! the! Waitomo! speleothem! has! Sr/Ca! values! closer!to!the!Nettlebed!speleothem!relative!to!the!Wairoa!speleothem.!Cave!depth!could! be!a!plausible!factor!to!this!variation!as!the!Waitomo!cave!system!is!deeper!than!the! Wairoa!cave.!The!annual!rainfall!for!Nettlebed!is!812!mm/yr!(Metservice);!retrieved!17! September!2015).!!Therefore,!another!reason!for!the!Sr/Ca!variations!could!be!that!the! Waitomo!and!Wairoa!regions!experience!slightly!higher!average!rainfalls!as!mentioned! previously,!and!thus!have!a!warmer!and!wetter!climate!relative!to!the!Nettlebed!region.!! ! 0.00E+00! 5.00EN05! 1.00EN04! 1.50EN04! 2.00EN04! 2.50EN04! 0.00E+00! 1.00EN04! 2.00EN04! 3.00EN04! 4.00EN04! 5.00EN04! 6.00EN04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Sr/Ca! Age!(AD)! Wairoa! Sr! Waitomo! Sr! 277.8%! 168.9%! Glacial!value:!6.3$x$10 '5 $ Interglacial!value:!9.0$x$10 '5$ Magnitude$change:$31.1%$ !
! 35! ! 4.2!Paleoclimate!inferences!from!Mg/Ca,!Ba/Ca!and!Sr/Ca!ratios! These! three! element/Ca! ratios! have! been! chosen! to! infer! paleoclimate! because! they! have!been!previously!well!studied!and!understood!(Fairchild!et!al.,!2012;!Orland!et!al.,! 2014;!Huang!et!al.,!2001),!and!are!now!conventionally!used!as!paleoclimate!indicators.! ! Huang! et! al.! (2001)! investigated! the! variations! in! trace! element! concentrations! in! speleothems!from!the!Ernesto!cave!(northeast!Italy).!The!results!showed!that!Mg!largely! has!a!negative!covariation!with!Sr!in!bandings!formed!in!the!1990s,!and!a!positive!coN variation! with! bandings! formed! in! the! 1960s.! These! were! in! response! to! changes! in! hydroNenvironmental!conditions!and!climate!variations.!Therefore,!it!has!been!proposed! that! during! cold–dry! periods,! speleothems! will! have! relatively! high! Mg/Ca! with! relatively! high! Sr/Ca! and! Ba/Ca! ratios.! On! short! timescales,! New! Zealand’s! warm! periods! are! associated! with! less! rainfall! (warm/dry),! whereas! cold! periods! are! associated!with!more!rainfall!(cold/wet).!The!resolution!of!the!dataset!presented!in!this! study!is!only!applicable!to!larger!timescales!and!therefore!the!assumption!of!warm/wet! periods!and!cold/dry!periods!are!applicable.! ! In! the! Waitomo! speleothem,! Mg/Ca! ratios! increase! between! 250–400! AD! and! Sr/Ca! ratios!decrease!between!250–400!AD!(Figures!25!&!26).!However,!Sr/Ca!ratios!do!not! drastically!decrease.!This!subdued!inverse!relationship!indicates!that!during!the!period! of! 250–400! AD,! Mg/Ca! ratios! changed! in! response! to! climate! change.! Therefore,! between! 250–400! AD! there! would! have! been! less! rainfall,! with! moderately! warmer! temperatures.!Between!700–710!AD!and!460–480!AD!Mg/Ca!ratios!increase,!whereas! Sr/Ca! ratios! are! relatively! low.! These! periods! represents! a! time! of! less! rainfall! and! relatively!warmer!conditions.!! ! For! the! Wairoa! speleothem,! periods! between! 60–140! AD,! 160–250! AD,! 260–370! AD,! 400–500! AD,! 540–630! AD! and! 700–780! AD! have! relatively! low! Mg/Ca! ratios! and! periods! between! 60–100! AD,! 260–360! AD,! 410N507! AD,! 540–620! AD! have! relatively! high!Sr/Ca!ratios.!!These!periods!reflect!warmer!and!wetter!conditions!(Figure!27).!
! 36! ! Figure!27:!TimeNseries!of!Mg/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;! red).! The! timeNseries! highlights! peaks! in! Mg! for! the! Wairoa! speleothem! showing!warm–wet!climatic!conditions!(red!triangles)!and!periods!noted!as!prehistoric! stormy!periods!recorded!in!lake!sediments!from!Lake!Tutira!(black!boxes).!Green!boxes! show!warm–wet!periods!(Low!Mg,!High!Sr).! ! Changes!in!the!sediment!character!of!cores!taken!from!Lake!Tutira!can!be!interpreted!to! represent! changing! climatic! conditions! such! as! the! occurrence! of! major! storms! and! droughts!(Page!et!al.,!2010).!These!events!recorded!in!the!sedimentary!layers!will!only! capture!or!record!paleoNstorms!that!were!associated!with!extreme!rainfall!events.!Such! storm!events!would!be!needed!to!have!large!amounts!of!precipitation!in!order!to!wash! and!erode!detritus!material!into!the!lake!from!the!surrounding!hills,!and!thus!not!all! storms!(in!terms!of!windiness)!are!likely!to!be!recorded.!Page!et!al.!(2010)!identified!0– 120!AD,!470–550!AD!and!680–830!AD!as!periods!of!major!storms.!These!time!periods! described!by!Page!et!al.!(2010)!correspond!to!a!decreasing!Mg!peak!between!0–120!AD,! after!a!low!Mg!trough!for!470–550!AD!and!at!a!trough!in!Mg!between!680–830!AD.!The! low! Mg! concentrations! in! the! Wairoa! speleothem! are! located! around! these! stormy! events,!however!the!storm!periods!vary!somewhere!around!the!low!Mg!concentrations! either! due! to! a! lag! in! time! from! the! event! or! because! the! storms! were! perhaps! not! always!large!enough!to!cause!detritus!material!to!be!eroded!from!near!by!hills.!Page!et! al.!(2010)’s!findings!as!well!as!low!Mg!concentrations!are!consistent!with!a!warm–wet! climate!between!60–140!AD,!470–500!AD!and!680–770!AD!(Figure!27).!! !
! 37! ! 4.3!Paleoclimate!inferences!from!Na/Ca!values!in!speleothems! As!described!in!section!4.1,!cave!depth!and!hydrology!provide!a!firstNorder!control!on! the!speleothem!Mg!concentration!and,!as!such,!the!effects!of!this!have!been!normalised! out!by!normalising!Na!to!Mg!concentrations.!! ! Using! this! approach,! it! is! evident! that! the! Wairoa! speleothem! has! higher! Na! concentrations! relative! to! the! Waitomo! speleothem.! The! Wairoa! speleothem! has! an! average!Na/Mg!ratio!of!1.1!x!10–1!and!the!Waitomo!speleothem!has!an!average!Na/Mg! ratio!of!5.3!x!10N2.!Intuitively,!this!might!be!expected!as!sea!salt!spray!will!be!higher!at! (nearN)! coastal! regions! (i.e.,! Wairoa)! relative! to! more! inland! regions! (i.e.,! Waitomo).! Thus,!the!different!Na/Mg!averages!for!the!two!speleothems!may!be!due!to!Wairoa!being! closer!to!the!coast!than!Waitomo!(Figure!8).!! ! A!secondNorder!observation!is!that!Wairoa!has!significantly!larger!Na/Mg!peaks!than!the! Waitomo!speleothem.!Wairoa!has!seven!significant!Na/Mg!peaks,!where!distinct!influxes! of!Na!entered!into!the!hydrological!system!and!were!ultimately!incorporated!into!the! speleothem.!The!peaks!for!Wairoa!are!observed!at!150!AD,!227!AD,!261!AD,!320!AD,!383! AD,!557!AD!and!752!AD.!In!contrast,!Waitomo!has!more!subdued!Na/Mg!peaks!that!are! less!defined!than!the!Wairoa!Na/Mg!peaks.!The!Na/Mg!peaks!for!Waitomo!are!observed! at!31!AD,!103!AD,!134!AD,!192!AD,!275!AD,!487!AD!and!714!AD.!Previous!discussion!of! variations!in!Mg/Ca!values!(section!4.1),!as!well!as!the!Na/Mg!variations!discussed!in! this! section,! illustrate! again! that! cave! depth! appears! to! control! the! sensitivity! of! the! speleothem!chemistry!to!environmental!factors.! !
! 38! ! Figure!28:!TimeNseries!of!Na/Mg!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).!The!timeNseries!highlights!peaks!in!Na!for!the!Wairoa!speleothem!(green! rectangles)! corresponding! to! prehistoric! stormy! periods! recorded! in! lake! sediments! from!nearby!Lake!Tutira!(grey!boxes)!and!antiNphase!correlations!for!Na!concentrations! in!the!Wairoa!and!Waitomo!speleothems!(black!dotted!lines).! ! The! grey! rectangles! mark! periods! where! major! prehistoric! storm! events! took! place.! Some!storms!may!be!associated!with!only!windy!or!wet!conditions,!whereas!others!may! be!associated!with!both!windy!and!wet!conditions.!Not!only!do!the!deposits!rely!on!the! type!of!storm!but!also!the!size!of!the!storms.!This!complexity!might!explain!why!not!all! Na!peaks!have!corresponding!storm!records!from!Lake!Tutira.!The!Na!peaks!in!Figure! 28! highlighted! in! green! do! have! correlated! stormy! periods! recorded! in! Lake! Tutira.! Thus,!the!storms!observed!in!the!records!had!both!windy!and!wet!conditions.!! ! ! ! ! ! ! !
! 39! ! Figure!29:!Mg/Ca!versus!Na/Ca!ratios!for! the!Wairoa!speleothem.!! The!R2!(0.05)!value!for!Mg/Ca!and!Na/Ca! illustrates! that! there! is! a! very! weak! correlation!between!the!two!ratios.!There! appears!to!be!a!cluster!of!values!for!Na/Ca! from!2.43!x!10N5!to!6.58!x!10N5!and!Mg/Ca! from!3.15!x!10N4!to!5.53!x!10N4.! ! ! ! ! ! ! Figure!30:!Sr/Ca!versus!Na/Ca!ratios!for! the!Wairoa!speleothem.!! The! R2! (0.03)! value! for! Sr/Ca! and! Na/Ca! illustrates! that! there! is! a! very! weak! correlation!between!the!two!ratios.!There! appears!to!be!a!cluster!of!values!for!Na/Ca! from!2.44!x!10N5!to!6.62!x!10N5!and!Sr/Ca! from!1.88!x!10N4!to!5.16!x!10N4.! ! ! ! ! ! Figure! 31:!U/Ca!versus!Na/Ca!ratios!for! the!Wairoa!speleothem.! The! R2! (0.2)! value! for! U/Ca! and! Na/Ca! illustrates!that!there!is!statistically!a!weak! correlation!between!the!two!ratios.!There! appears!to!be!a!cluster!of!values!for!Na/Ca! from!2.38!x!10N5!to!7.62!x!10N5!and!U/Ca! from!2.09!x!10N7!to!8.66!x!10N7.! ! ! ! Mg/Ca! ! 0.00E+00! 1.00EN04! 2.00EN04! 3.00EN04! 4.00EN04! 5.00EN04! 6.00EN04! Wairoa! 0.00E+00! 2.00EN04! 4.00EN04! 6.00EN04! 8.00EN04! 1.00EN03! 1.20EN03! Wairoa! 0.00E+00! 2.00EN07! 4.00EN07! 6.00EN07! 8.00EN07! 1.00EN06! 1.20EN06! Wairoa! Sr/Ca! ! U/Ca! ! Na/Ca! !
! 40! The!data!plotted!in!Figures!28–30!all!show!considerable!variations!in!Mg,!Sr!and!U,!but! these! are! only! weakly! (U)! or! not! correlated! at! all! with! Na! concentrations,! which! randomly!extend!to!high!values.!These!points!are!controlling!and!lowering!the!R2!values! in!these!plots.!The!clusters!can!be!interpreted!as!the!normal!climatic!conditions!and!the! points!that!deviate!away!from!the!trend!are!the!events!(i.e.,!storms)!that!are!anomalous! and!deliver!Na!to!the!land!surface!and!cave!hydrological!systems.!! ! Where!Na/Ca!is!high!(>2.4!x!10N5),!Mg/Ca!varies!from!3.5!x!10N4!to!1.0!x!10N3!and!Sr/Ca! varies!from!1.7!x!10N4!to!4.0!x!10N4.!The!(generally)!high!Mg/Ca!and!low!Sr/Ca!values! when! anomalous! Na! peaks! occur! are! diagnostic! of! warm–wet! conditions.! Warm–wet! conditions! are! historically! associated! with! stormy! periods! as! it! forces! surface! air! pressures!to!drop,!creating!extreme!air!pressure!differences!and!thus!windy!and!wet! conditions.! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
! 41! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
! 42! ! El!Niño!and!La!Niña!cycles!significantly!influence!wind!direction!and!climate!patterns!in! New!Zealand.!Historic!records!for!El!Niño!and!La!Niña!events!only!extend!back!to!the! late! 1970s/early! 1880s! and! show! that! the! El! Niño! and! La! Niña! occurs! on! a! frequent! basis!between!every!ca.!5–15!yr!(Folland,!2002).!Figure!32!highlights!smaller!Na!peaks! to! occur! on! average! every! ca.! 10–20! yr,! with! larger! peaks! occurring! with! infrequent! intervals! of! 75,! 35,! 65,! 55,! 170! and! 200! yr.! The! frequency! of! the! smaller! Na! peaks! corresponds!with!the!frequency!of!the!El!Niño–!La!Niña!cycle.!As!historical!records!for!El! Niño!do!not!extend!back!to!the!period!between!0–800!AD,!a!plausible!explanation!for!the! larger!Na!peaks!is!extreme!El!Niño!events!or!nonNEl!Niño!tropical!storms.! La! Niña! events! lower! seaNsurface! temperatures! in! the! Pacific! Ocean! and! thus! New! Zealand!experiences!cooler!temperatures!during!a!La!Niña!on!the!west!coast!(NIWA);! retrieved! 13! August! 2015).! The! El! Niño! cycle! raises! seaNsurface! temperatures! in! the! Pacific! and! thus! New! Zealand! experiences! a! warmer! and! wetter! climate! on! the! west! coast.!During!a!La!Niña,!the!east!coast!experiences!northNeasterly!winds,!while!during!an! El!Niño!the!west!coast!experiences!southNwesterly!winds.!Due!to!the!dominating!wind! patterns!as!a!result!of!the!El!Niño!and!La!Niña!events,!it!is!observed!that!during!a!La! Niña! event,! the! Wairoa! speleothem! has! Na! peaks,! while! during! an! El! Niño! event,! Waitomo! has! Na! peaks.! This! is! seen! in! ! ! ! Figure! 28! where! the! small! scale! cyclicity! between!Wairoa!and!Waitomo!Na!concentrations!are!antiNphased!(dotted!black!lines!in! Figure! 28).! These! antiNphased! periods! are! seen! where:! Wairoa! has! increased! Na! concentrations!and!Waitomo!have!decreased!Na!concentrations!(20!AD,!84!AD,!170!AD,! 227!AD,!305!AD,!764!AD)!and!Wairoa!has!decreased!Na!concentrations!and!Waitomo! have!increased!Na!concentrations!(97!AD,!115!AD).! ! ! ! ! ! ! ! ! !
! 43! ! ! Figure!33:!TimeNseries!of!Mg/Ca!(purple)!and!Na/Mg!(green)!ratios!for!the!Wairoa! speleothem.!.!The!timeNseries!highlights!corresponding!Mg!peaks!and!troughs!for!peaks! in!Na.!The!correlations!between!Mg!and!Na!infer!climatic!conditions.! ! Figure! 33! compares! Mg! and! Na! concentrations! for! the! Wairoa! speleothem! to! infer! correlations!of!wet!periods!from!the!low!Mg!values!with!that!of!high!Na!values.!At!~80! AD,!~180!AD,!~320!AD,!~580!AD,!~610!AD,!~680!AD!there!are!small!peaks!in!Na!and! low!Mg!values.!These!periods!can!be!justified!as!little!storm!events!that!had!wet!and! relatively!little!wind.!At!~150!AD,!~220!AD,!~260!AD,!~390!AD!there!are!peaks!in!both! Na!and!Mg!values.!These!periods!can!be!thought!as!wind!events!with!no!rain.!At!~550! AD!and!~750!AD!there!are!massive!Na!peaks!with!low!Mg!values.!These!periods!are! thought!to!be!larger!storm!events,!which!were!both!rain!and!wind!events.!!
! ! 44! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!5!! ! 5.0$Conclusions$ $ A!trace!element!study!of!two!speleothems!from!the!Waitomo!and!Wairoa!regions!of!the! North!Island!of!New!Zealand!has!shown!that:! ! 1. The!Waitomo!speleothem!has!significantly!higher!Mg!concentrations!compared! with!that!of!the!Wairoa!speleothem,!and!that!the!different!average!Mg/Ca!ratios! for!the!two!speleothems!are!likely!to!be!primarily!due!to!cave!depth!at!each!site! rather!than!regional!climate!variations.!! 2. Mg/Ca!ratios!in!the!Wairoa!speleothem!show!clear!cyclical!variations!with! distinct!peaks,!which!are!most!likely!in!response!to!climate!variations.!The! Wairoa!speleothem!appears!to!be!a!more!sensitive!archive!that!better!records! climatic!change!relative!to!the!Waitomo!speleothem.! 3. A!previously!studied!speleothem!from!northwest!Nelson!(reference)!shows! changes!in!trace!element!chemistry!during!glacial!and!interglacial!periods.! Similar!sized!changes!are!observed!for!Mg!during!the!period!0–800!AD!in!both! the!Waitomo!and!the!Wairoa!speleothems,!but!not!for!Sr.!These!Mg/Ca!changes! support!the!conclusion!that!Mg!in!speleothems!is!partly!related!to!cave!depth.! The!cave!depth!also!alters!the!sensitivity!of!the!trace!element!chemistry!in!the! speleothems!to!changing!environmental!conditions.!The!deeper!the!cave,!the!less! sensitive!the!trace!element!chemistry!of!the!speleothems!is!to!changes!in! environmental!parameters.!!! 4. There!is!a!distinct!Na!difference!between!the!two!speleothems.!The!Wairoa! speleothem!has!higher!Na!concentrations!than!the!Watomo!speleothem.!This!is! due!to!Wairoa!being!a!more!(nearP)!coastal!region!than!that!of!Waitomo,!which!is! relatively!inland!as!compared!with!the!Wairoa!site.!! 5. Spikes!in!Na!concentrations!relate!to!either!windy!storm!events,!rainy!storm! events!or!both!wind!and!storm!events.!Rainy!storm!events!occur!when!Mg! concentrations!are!relatively!low!and!Na!concentrations!are!relatively!high.! Windy!storm!events!occur!when!Na!and!Mg!concentrations!are!relatively!high.!
! ! 45! Wind!and!rainy!storm!events!occur!when!Na!concentrations!are!very!high! relative!to!a!very!low!Mg!concentration.! 6. Na!concentrations!between!the!two!speleothems!shows!antiPphased!cycles.!It!is! hypothesized!that!during!a!La!Niña!event,!the!Wairoa!speleothem!has!Na!peaks! and!the!El!Niño!has!Na!depletions,!whereas!during!an!El!Niño!event,!Waitomo!has! Na!peaks!and!the!Wairoa!speleothem!has!Na!depletions.!This!is!because!during!a! La!Niña,!the!east!coast!experiences!northeasterly!winds,!while!during!an!El!Niño! the!west!coast!experiences!southwesterly!winds,!thereby!influencing!delivery!of! Na!via!marine!aerosols!to!each!site.!
! 46! References(( Bieniok,!A.,!Zagler,!G.,!Brendel,!U.,!Neubauer,!F.,!2011.!Speleothems!in!the!dry!cave!parts! of! the! GamslöcherGKolowrat! Cave,! Untersberg! near! Salzburg! (Austria).! International! Journal!of!Speleology!40!(2),!117!–!124.! Calaforra,!J.M.,!Forti,!P.,!FernandezGCortes,!A.,!2008.!Speleothems!in!gypsum!caves!and! their!paleoclimatological!significance.!Environmental!Geology!53!(5),!1099!–!1105.! Cross,!M.,!McGee,!D.,!Broecker,!W.S.,!Quade,!J.,!Shakun,!J.D.,!Cheng,!H.,!Lu,!Y.,!Edwards,! R.L.,!2015.!Great!Basin!hydrology,!paleoclimate,!and!connections!with!the!North!Atlantic:! A! speleothem! stable! isotope! and! trace! element! record! from! Lehman! Caves,! NV.! Quaternary!Science!Reviews!.! Cruz,! J.A.,! MartÃnGChivelet,! J.,! MarÃnGRoldán,! A.,! Turrero,! M.J.,! Edwards,! R.L.,! Ortega,! A.I.,!Cáceres,!J.O.,!2015.!Trace!elements!in!speleothems!as!indicators!of!past!climate!and! karst! hydrochemistry:! A! case! study! from! Kaite! Cave! (N! Spain).! Environmental! Earth! Sciences!1,!569!–!577.! Fairchild,!I.J.,!Baker,!A.,!Asrat,!A.,!DomÃnguezGVillar,!D.,!Gunn,!J.,!Hartland,!A.,!Lowe,!D.,! 2012.!Speleothem!Science:!From!Process!to!Past!Environments.!! Folland,!C.K.,!2002.!Relative!influence!of!the!Interdecadal!Pacific!Oscillation!and!ENSO!on! the!South!Pacific!Convergence!Zone.!Geophys!Research!Letters.!29!(13).! GeoRem:!A!New!Geochemical!Database!for!Reference!Materials!and!Isotopic!standards,! Retrieved!22GJulyG2015.!GeoRem:!georem.mpchGmainz.gwdg.de!(Weekly).! Harms,!B.,!Elmore,!R.D.,!Engel,!M.H.,!2008.!Inferring!climate!change!from!stable!isotope! compositions! of! ancient! speleothems! on! Earth:! Possible! implications! for! climatic! reconstructions!elsewhere!in!the!solar!system.!Proceedings!of!SPIE!G!The!International! Society!for!Optical!Engineering!7097.! Huang,!Y.,!Fairchild,!I.J.,!Borsato,!A.,!Frisia,!S.,!Cassidy,!N.J.,!McDermott,!F.,!Hawkesworth,! C.J.,!2001.!Seasonal!variations!in!Sr,!Mg!and!P!in!modern!speleothems!(Grotta!di!Ernesto,! Italy).!Chemical!Geology!175!(3!–!4),!429!–!448.!
! 47! Ku,! T.L.,! Li,! H.C.,! 1998.! Speleothems! as! high;resolution! paleoenvironment! archives:! Records!from!northeastern!China.!Proceedings!of!the!Indian!Academy!of!Sciences,!Earth! and!Planetary!Sciences!107!(4),!321!–!330.! Latkoczy,!C.,!Ghislain,!T.,!2006.!Simultaneous!LIBS!and!LA;ICP;MS!analysis!of!industrial! samples.!Journal!of!Analytical!Atomic!Spectrometry!21!(11),!1152!–!1160.! Legrand,!M.R.,!Lorius,!C.,!Barkov,!N.I.,!Petrov,!V.N.,!1988.!Vostok!(Antarctica)!ice!core:! Atmospheric! chemistry! changes! over! the! last! climatic! cycle! (160,000! years).! Atmospheric!Environment!22!(2),!317!–!331.! Li,!Z.H.,!Driese,!S.G.,!Cheng,!H.,!2014.!A!multiple!cave!deposit!assessment!of!suitability!of! speleothem! isotopes! for! reconstructing! palaeo;vegetation! and! palaeo;temperature.! Sedimentology!61!(3),!749!–!766.! Lorrey,!A.M.,!Griffiths,!G.,!Fauchereau,!N.,!Diamond,!H.J.,!Chappell,!P.R.,!Renwick,!J.,!2014.! An!ex;tropical!cyclone!climatology!for!Auckland,!New!Zealand.!International!Journal!of! Climatology!34!(4),!1157!–!1168.! Ma,! Q.L.,! Motto;Ros,! V.,! Lei,! W.Q.,! Boueri,! M.,! Zheng,! L.J.,! Zeng,! H.P.,! Bar;Matthews,! M.,! Ayalon,! A.,! Panczer,! G.,! Yu,! J.,! 2010.! Multi;elemental! mapping! of! a! speleothem! using! laser;induced! breakdown! spectroscopy.! Spectrochimica! Acta! ;! Part! B! Atomic! Spectroscopy!65!(8),!707!–!714.! Maher,!K.,!Ibarra,!D.E.,!Oster,!J.L.,!Miller,!D.M.,!Redwine,!J.L.,!Reheis,!M.C.,!Harden,!J.W.,! 2014.!Uranium!isotopes!in!soils!as!a!proxy!for!past!infiltration!and!precipitation!across! the!western!United!States.!American!Journal!of!Science!314!(4),!821!–!857.! Manatū! Taonga! Ministry! for! Culture! and! Heritage,! Story:! Landslides.! Te! Ara! –! The! Encyclopedia!of!New!Zealand!2015!(September!21).! Metservice,!Retrieved!17;September;2015.!National!Weather!Services!for!New!Zealand.! http://www.metservice.com/national/home! McDermott,! F.,! 2004.! Palaeo;climate! reconstruction! from! stable! isotope! variations! in! speleothems:!A!review.!Quaternary!Science!Reviews!23!(7;8),!901!–!918.!
! 48! Orland,!I.J.,!Burstyn,!Y.,!Bar;Matthews,!M.,!Kozdon,!R.,!Ayalon,!A.,!Matthews,!A.,!Valley,! J.W.,!2014.!Seasonal!climate!signals!(1990;2008)!in!a!modern!Soreq!Cave!stalagmite!as! revealed!by!high;resolution!geochemical!analysis.!Chemical!Geology!363,!322.! Page,! M.J.,! Trustrum,! N.A.,! Orpin,! A.R.,! Carter,! L.,! Gomez,! B.,! Cochran,! U.A.,! Mildenhall,! D.C.,!Rogers,!K.M.,!Brackley,!H.L.,!Palmer,!A.S.,!Northcote,!L.,!2010.!Storm!frequency!and! magnitude!in!response!to!Holocene!climate!variability,!Lake!Tutira,!North;Eastern!New! Zealand.!Marine!Geology!270!(1;4),!30;44.! Paton,! C.,! Hellstrom,! J.,! Paul,! B.,! Woodhead,! J.,! Hergt,! J.,! 2011.! Iolite:! Freeware! for! the! visualisation! and! processing! of! mass! spectrometric! data.! Journal! of! Analytical! Atomic! Spectrometry!26!(12),!2508!–!2518.! Sinclair,!M.R.,!1993.!A!diagnostic!study!of!the!extratropical!precipitation!resulting!from! Tropical!Cyclone!Bola.!Monthly!Weather!Review!121!(10),!2690!–!2707.! The! National! Climate! Database! (NIWA),! Retrieved! 26;June;2015.! CliFlo:! NIWA's! National!Climate!Database!on!the!Web.!http://cliflo.niwa.co.nz!(Weekly).! The! National! Institute! of! Water! and! Atmospheric! Research! (NIWA),! Retrieved! 13; August;2015.! https://www.niwa.co.nz/our;science/climate/information;and; resources/clivar/elnino! Ulusoy,! T.,! Anbar,! G.,! Bayari,! S.,! Uysal,! T.,! 2014.! ESR! and! 230Th/234U! dating! of! speleothems!from!Aladaǧlar!Mountain!Range!(AMR)!in!Turkey.!Quaternary!Research! (United!States)!81!(2),!367!–!380.! Wang,!H.,!Shooter,!D.,!2001.!Water!soluble!ions!of!atmospheric!aerosols!in!three!New! Zealand!cities:!Seasonal!changes!and!sources.!Atmospheric!Environment!35!(34),!6031!–! 6040.! Winograd,!I.J.,!Coplen,!T.B.,!Landwehr,!J.M.,!Riggs,!A.C.,!Ludwig,!K.R.,!Szabo,!B.J.,!Kolesar,! P.T.,! Revesz,! K.M.,! 1992.! Continuous! 500,000;year! climate! record! from! vein! calcite! in! Devils!Hole,!Nevada.!Science!258!(5080),!255!–!260.! !
! 49! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

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CHERISE MARTIN FINaL 1809856

  • 1.
    ! ! ! ! Honours!Dissertation! ! !!!!!!!!!!!! ! !!!!!!!!!!!!!!!!Earth!Science ! ! ! ! November!2015! ! Sodium!concentrations!in!speleothems! as!a!proxy!and!archive!for!past!wind! conditions!and!storm!events! ! Cherise!Martin! The!University!of!Auckland! ! ! ! ! ! ! ! ! ! Word!count! (Includes!abstract,!chapter!1>4!&! ! ! 8,!827!!words! conclusion,!excludes!figure!captions):!! ! ! ! Total!word!count:!! ! ! ! 11,!098!words!
  • 2.
  • 3.
    ! iii! Acknowledgments! ! I! could!not! have! completed! my! dissertation! without! the! help! of! several! individuals,! whom! I! deeply! thank.! My! advisor,! Professor! Joel! Baker,! whom! offered! the! incredible! opportunity!to!work!with!state!of!the!art!and!innovative!technology!in!Wellington.!He! matured!and!evolved!my!understanding!in!the!geochemistry!world.!Dr!Simon!Baker!who! was!continuously!there!to!guide!my!understanding.!!Both!have!given!me!support!and! constructive! criticism.! Dr! Paul! Williams! who! was! available! for! all! my! questions! and! provided!me!with!my!two!speleothems.!My!friends,!which!I!am!fortunate!to!have!too! many!to!name!individually,!whom!promoted!balance.!My!family,!both!far!and!near!for! the!unconditional!encouragement.!I!am!also!thankful!for!the!financial!contributions!from! the!Faculty!of!Science!for!my!research.!I!greatly!appreciate!help!in!the!laboratories!from! Andreas,!Dan,!Simon,!Joel,!Neville,!as!well!as!analytical!assistance!from!Michael!Rowe.! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
  • 4.
  • 5.
    ! v! Abstract(( ! Trace!element!data!were!measured!by!laser!ablation!inductively!coupled!plasma!mass! spectrometry! in!two! speleothems! from! Waitomo! (GG5;! western! North! Island)! and! Wairoa!(DS;!eastern!North!Island)!over!the!period!0–800!AD.!The!focus!of!this!study!was! to!investigate!if!Na!concentrations!in!speleothems!provide!a!proxy!and!archive!for!past! wind!conditions!and!storm!events.!The!Waitomo!speleothem!has!significantly!higher!Mg! concentrations!as!compared!with!the!Wairoa!speleothem,!interpreted!to!reflect!greater! cave! depth! at! Waitomo.! Mg/Ca! ratios! in! the! Wairoa! speleothem! show! clear! cyclical! variations!with!distinct!peaks,!which!are!most!likely!recording!past!climatic!variations.! The!Wairoa!speleothem!is!a!more!sensitive!archive!that!better!records!climatic!change! relative!to!the!Waitomo!speleothem!due!to!the!former!being!a!shallower!cave!system.!As! such,! Na! was! normalised! to! Mg! in! order! to! minimise! the! effect! of! cave! depth! on! speleothem!chemistry.!Na/Mg!ratios!are!higher!on!average!and!show!larger!peaks!in!the! Wairoa!speleothem!than!in!the!Waitomo!speleothem,!which!most!likely!reflects!the!fact! that!the!Wairoa!speleothem!was!taken!from!a!site!relatively!close!to!the!coast.!Large!Na! peaks!in!the!Wairoa!speleothem!between!0–120,!470–550!and!680–830!AD!correspond! with!periods!of!increased!storms!identified!from!the!character!of!sediments!in!nearby! Lake!Tutira.!Cyclicity!of!smaller!Na!peaks!in!the!speleothems!appear!to!correspond!with! the!frequency!(ca.!10–15!yr)!of!the!El!Niño!–!La!Nina!cycle.!The!results!of!this!study! indicate! that! Na! concentrations! in! speleothems! hold! considerable! promise! for! reconstructing! paleoWwind! and! Wstorm! conditions! related! to! large! storm! events! and! climate!cycles!that!affect!New!Zealand!and!elsewhere.! ( ( ( ( ( ( ( ( ( (
  • 6.
    ! vi! Table(of(contents( ! Acknowledgements………………………………………………………………………………………………! Abstract……………………………………………………………………………………………………………….! Preface…………………………………………………………………………………………………………………! ! Chapter(One…………………………………………………………………………………………...………….! 1! 1.0!Introduction!! 1.1#Objective…………………………………………………………………………………..………….!1! 1.2#Background……………………………………………………………………………….…………# 1! # 1.2.1#Speleothems#formation…………………………………………………………….# 1! # 1.2.2#Speleothem#geochemistry…………………………………………………………! 2# 1.2.3#δ18O#and#δ13C#stable#isotopes…………………………………………………….! 3# # 1.2.4#UraniumDseries#dating………………………………………………………..……! 4! # 1.2.5#Sodium………………………………………………………………….………………..! 5# # 1.2.6#Late#Holocene#climate#and#cycles#in#New#Zealand…..………………….! 5# # 1.2.7#Storm#Events……………………………………………………….………………….! 7# # 1.2.7.1#Historic#storm#events………………………………………………….! 7! # 1.2.7.2#Prehistoric#storm#events……………………………………….…….! 9 ! # # 1.2.8#Structure#of#thesis…………………………………………………..…….! 9! # Chapter(Two……………………………………………………………………………………………………..! 10! 2.0!Methodology…………………………………………………………………………………………………! 10! ! 2.1#Selection#of#speleothems#for#study………………………………………………………….! 10# # 2.2#Speleothem#GG5#(Waitomo)#………………………………………………………..………..! 11# # # 2.2.1#GG5#sample#preparation…………………………………………………………..! 11! # 2.3#Speleothem#DS#(Wairoa)#………………………………………………………………………! 12! ############### 2.3.1#DS#sample#preparation#(DS)……………………………………………..………! 12! # 2.4#Data#collection#techniques…………………………………………………….………………! 13! # # 2.4.1#Laser#ablation#inductively#coupled#plasma#mass#spectrometry……! 13# 2.5!Data!processing!techniques………………………………………………………………….! 15! ! ! 2.6.1!Iolite!data!processing……………………………………………….…………….! 15! ! Chapter(Three…………………………………………………………………………………………………...! 16! 3.0!Results…………………………………………………………………………………………………………..! 16! ! 3.1!Trace!element!data!normalised!to!Ca……………………………………………………! 16! ! 3.2!Trace!element!normalised!to!Mg……………………………………….………………….! 22! ! 3.3!Trace!element!correlations…………………………………………………………………..! 26! ! ! ! ! !
  • 7.
    ! vii! Chapter(Four……………………………………………………………………………………………………..! 30! 4.0!Discussion……………………………………………………………………………………………………..!30! ! 4.1!Similarities!and!differences!for!Mg/Ca,!Sr/Ca,!and!Ba/Ca…….………………..! 30! ! 4.2!PaleoWclimate!inferences!from!Mg/Ca,!Ba/Ca!and!Sr/Ca………………….….…! 35! ! 4.3!PaleoWclimate!inferences!from!Na/Ca………………………………………...…………! 37! ! Chapter(Five………………………………………………………………………………………………………! 44! 5.0!Conclusion……………………………………………………………………………………………………..! 44! ! List(of(figures…………………………………………………………………………………………………….! 1. Cave!environment…………………………………………………………………………………….! 2! 2. Uranium!decay!chain………………………………………………………………………………..! 4! 3. El!Niño!wind!anomalies…………………………………………………………………………….! 6! 4. La!Niña!wind!anomalies……………………………………………………………………………! 6! 5. Rainfall!for!New!Plymouth………………………………………………………………………..! 6! 6. Rainfall!for!Napier……………………………………………………………………………………! 7! 7. Landslide!and!soil!erosion!from!cyclone!Bola…………………………………………….! 8! 8. Location!of!DS!and!GG5…………………………………………………………………………….! 10! 9. Cross!section!of!GG5…………………………………………………………………………………! 11! 10. Cross!section!of!DS…………………………………………………………………………………...! 12! 11. ICPWMS!experimental!setup………………………………………………………………………! 14! 12. TimeWseries!of!Na/Ca………………………………………………………………………………..! 16! 13. TimeWseries!of!Mg/Ca………………………………………………………………………………..! 18! 14. TimeWseries!of!Sr/Ca…………………………………………………………………………………! 19! 15. TimeWseries!of!Ba/Ca………………………………………………………………………………..! 20! 16. TimeWseries!of!U/Ca………………………………………………………………………………….! 21! 17. TimeWseries!of!Na/Mg………………………………………………………………………………..! 22! 18. TimeWseries!of!Sr/Mg………………………………………………………………………………...! 23! 19. TimeWseries!of!Ba/Mg………………………………………………………………………………..! 24! 20. TimeWseries!of!U/Mg…………………………………………………………………………………! 25! 21. Mg/Ca!vs!Na/Ca………………………………………………………………………………………..! 27! 22. Sr/Ca!vs!Na/Ca…………………………………………………………………………………………! 28! 23. U/Ca!vs!Na/Ca………………………………………………………………………………………….! 29! 24. TimeWseries!of!Mg/Ca………………………………………………………………………………..! 30! 25. TimeWseries!of!Mg/Ca!for!GG5!&!DS!vs!Nettlebed……………………………………….! 33! 26. TimeWseries!of!Sr/Ca!for!GG5!&!DS!vs!Nettlebed…………………………………………! 34! 27. TimeWseries!of!Mg/Ca………………………………………………………………………………..! 36! 28. TimeWseries!of!Na/Ca………………………………………………………………………………..! 38! 29. Mg/Ca!vs!Na/Ca………………………………………………………………………………………..! 39! 30. Sr/Ca!vs!Na/Ca…………………………………………………………………………………………! 39! 31. U/Ca!vs!Na/Ca………………………………………………………………………………………….! 39! 32. TimeWseries!of!Na/Mg………………………………………………………………………………..! 41! 33. TimeWseries!of!Na/Mg!&!Mg/Ca………………………………………………………………….! 43!
  • 8.
    ! viii! ! List(of(tables……………………………………………………………………………………………...………! 1. Wind!patterns!record!cyclone!A)!Drena,!B)!Gisele,!C)!Bola!&!D)!Fergus……....!8! 2. Stormy!periods!from!deposits!in!Lake!Tutira……………………………………………..! 9! 3. Reference!values!for!NIST!SRM610……………………………………………………………! 13! 4. Reference!values!for!NIST!SRM612……………………………………………………………! 13! 5. Pearson!linear!correlation…………………………………………………………………………! 26! 6. Mg,!U,!Ba!&!Sr!concentrations!for!Nettlebed!speleothem…………………………….! 32! 7. Pearson!linear!correlation…………………………………………………………………………! 34! ( References……………………………………………………………………………………..…………………..! 46! ! Electronic(Appendix(One:(Analytical(Data……………………………………..…………………….!( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ! ! ! ! ! !
  • 9.
    ! 1! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!1! ! 1.0!Introduction!! ! 1.1#Objectives# Historic!climatic!records!in!New!Zealand!only!extend!back!for!the!last!ca.!100!years!(The! National!Climate!Database!(NIWA);!retrieved!15!August!2015).!In!order!to!improve!our! understanding!of!climatic!changes!and!events!beyond!this!timeframe,!it!is!necessary!to! use!quantitative!proxies!of!past!environmental!conditions!and!apply!them!to!dateable! archives! that!can! then! be! used! to! reconstruct! past! environmental! conditions.! Recent! studies! have! shown! that! speleothems! (secondary! cave! carbonate! deposits)! are! important!paleoclimate!archives,!due!to!the!fact!that!speleothems!can!be!reliably!dated,! and! the! composition! of! the! precipitated! carbonate! varies! according! to! external! parameters! and! during! their! systematic! growth.! Speleothems! have! the! potential! to! reconstruct! past! climatic! conditions! at! annual! to! subannual! resolution.! This! study! investigates!the!potential!to!use!speleothem!trace!element!chemistry,!with!a!focus!on! sodium!(Na)!contents,!to!track!wind!conditions!and!storm!events!for!a!period!of!800!yr.! Two!speleothems!have!been!studied!from!two!different!cave!systems!from!(near)!the! west!and!east!coasts!of!the!North!Island!of!New!Zealand!over!the!time!interval!of!0–800! AD.! ! 1.2#Background# # 1.2.1#Speleothem#formation# Speleothems!are!secondary!mineral!deposits!of!calcium!carbonate!formed!on!the!ceiling,! walls! and! floors! of! caves.! The! precipitation! of! speleothems! relies! on! meteoric! water! seeping!through!the!carbonatePrich!lithologies!(limestone)!found!above!caves!(Calaforra! et!al.,!2008).!As!the!water!enters!the!atmosphere!and!seeps!through!the!upper!soil!it! incorporates!carbon!dioxide!from!the!atmosphere!as!well!as!from!the!organic!material! trapped! within! the! soil,! which! makes! the! water! acidic.! The! acidic! water! continues! to! leach! downwards! and! partially! dissolves! carbonatePrich! rocks.! As! the! meteoric! water! enters! the! cave! system,! the! carbon! dioxide! is! lost! to! the! cave’s! atmosphere! and! previously! dissolved! minerals! precipitate! out! to! form! speleothems! (Figure! 1).!
  • 10.
    ! 2! Speleothems!can!take!various!forms,!depending!on!a!cave’s!internal!atmosphere.!The! water!can!drip,!seep,!condense!or!flow,!which!creates!different!secondary!formations.! The! four!major! formations! include! dripstones,! flowstones,! pore! deposits! and! pool! deposits!(Huang!et!al.,!2001).!The!two!speleothems!in!this!study!are!from!different!caves! with!varying!conditions!and!thus!illustrate!two!different!types!of!speleothems.!GG5!is!a! stalactite! and! grows! downwards! from! the! caves! roof,! whereas! DS! is! a! flowstone! and! grows!as!water!flows!and!leaves!a!film!of!calcite.!These!two!processes!are!illustrated!in! Figure!1.!!! ! # 1.2.2#Speleothem#geochemistry# Speleothems!are!regarded!as!valuable!archives!of!past!climatic!conditions!due!to!their! relatively!simple!geometry,!and!the!fact!that!they!can!be!precisely!dated!(Ma!et!al.,!2010;! Harms! et! al.,! 2008).! The! trace! element! chemistry! and! stable! isotopic! compositions! of! speleothems!can!be!used!to!infer!past!climate!(McDermott,!2004;!Harms!et!al.,!2008).! Study! of! the! youngest! parts! of! speleothems! can! be! used! to! calibrate! the! relationship! between! climate! and! speleothem! chemistry! by! crossPcomparison! with! historic! Figure!1:!Schematic!of!a!typical!cave!environment!illustrating!key!processes!in!the! precipitations!of!speleothems!(adopted!from!Fairchild!et!al.,!2012).! ! Stalagmite) Stalac+te) Soil) Decay)of)plant)li2er)producing)CO2)) Slow)drips)allow) for)degassing)of) CO2))at)the)roof)of) the)cave)to)form)a) stalac+te) Fast)drips))allow) for)degassing)of) CO2)at)the)floor) of)the)cave)to) form)a)stalagmite) Flowstone)) Carbonate)rich) Country)rock) Atmosphere) Plant)respira+on)producing)CO2)
  • 11.
    ! 3! meteorological!records!from!The!National!Climate!Database!(NIWA).!The!stable!isotopic! compositions! of!speleothems! can! provide! climatic! proxies! for! diverse! environments! including!low!latitude!and!elevation!(Bieniok!et!al.,!2011)!environments!to!high!latitudes! and!elevation!environments!(Cruz!et!al.,!2015:!Orland!et!al.,!2014).! Speleothems! incorporate! minor! and! trace! elements! into! their! calcite! matrix! during! growth.!Stable!oxygen!and!carbon!isotopes!are!common!proxies!that!have!been!applied! in!speleothem!paleoclimate!studies!(McDermott,!2004;!Cruz!et!al.,!2015;!Li!et!al.,!2014),! along! with! some! trace! element! studies! (e.g.,! Mg,! Sr,! Ba! and! U).! These! geochemical! variations!have!been!used!to!reconstruct!regional!changes!in!precipitation,!temperature! and! paleoPvegetation! (Ku! and! Li,! 1998;! McDermott,! 2004).! Mg,! Sr! and! Ba! have! previously!been!used!by,!for!example,!Fairchild!et!al.!(2012),!Orland!et!al.!(2014)!and! Huang!et!al.!(2001)!to!infer!hot–wet!and!cold–dry!periods.!Low!Mg/Ca!ratios!with!high! Sr/Ca!and!Ba/Ca!ratios!characterise!relatively!warmPwet!periods!whereas!the!inverse! signals!coldPdry!periods!(Cross!et!al.,!2015;!Cruz!et!al.,!2015).! ! ! 1.2.3##δ18O#and#δ13C#stable#isotopes# Oxygen!and!carbon!isotopes!have!been!extensively!studied!in!speleothems!in!order!to! interpret! past! climate! events.! For! example,! Frappier! et! al.! (2007)! identified! δ18O! excursions!in!a!stalagmite!extracted!from!a!cave!in!central!Belize.!The!variations!in!δ18O! are!associated!with!11!tropical!cyclone!events.!The!study!achieved!weekly!to!monthly! temporal!resolution!and!found!that!major!negative!δ18O!excursions!coincided!with!the! landfall!of!tropical!cyclones!near!Belize!during!the!period!1977–2000.!This!stalagmite! (ATM7)!was!collected!three!months!after!Hurricane!Keith,!but!the!fingerprint!of!this!was! not! observed! in! the! stalagmite,! suggesting! that! infiltration! rates! cause! a! lag! time! between!such!events!and!their!incorporation!into!speleothems.!This!implication!of!lags! in! the! isotopic! signals! in! speleothems! was! recognised! by! McDermott! (2004)! and! attempts!to!analyse!D/H!ratios!in!fluid!inclusions!trapped!in!speleothems.!A!speleothem! from!Devil’s!Hole!recorded!continuous!δ18O!variations!for!500,000!yr.!These!speleothem! variations! were! shown! to! be! consistent! with! the! Vostok! ice! core! record! and! broadly! delineated! interglacial! and! glacial! periods! using! stable! isotope! data! (Legrand! et! al.,! 1988;!Winograd!et!al.,!1992).! ! !
  • 12.
    ! 4! ! 1.2.4#UraniumDseries#dating# Speleothems! have!been! established! as! one! of! the! best! terrestrial! archives! for! paleoclimate! reconstruction! as! they! can! be! precisely! dated! by! UPseries! techniques.! UraniumPseries!dating!measures!the!equilibrium!between!238U!and!230Th.!238U!decays!to! 234Th! through! alpha! decay! at! a! rate! of! 4.5! x! 109! yr.! The! decay! continues! through! a! number!of!other!decay!steps!(234Pa;!1.2!min),!(234U;!2.5!x!105!yr)!and!then!further!decays! to! 230Th! (7.7! x! 104! yr)! (Figure! 2)! (Ulusoy! et! al.,! 2014).! UraniumPseries! age! determinations! allow! growth! intervals! and! rates! for! individual! speleothems! to! be! determined!with!exquisite!resolution!(years!to!centuries).#The!banding!in!speleothems! illustrates! variable! periods! of! growth,! with! the! surface! of! the! speleothem! being! the! youngest!age,!and!the!interior!getting!progressively!older!towards!the!centre.!Each!band! can!be!dated!by!measuring!how!much!uranium!has!decayed!into!thorium!(Maher!et!al.,! 2014;!Ulusoy!et!al.,!2014).!The!uranium!from!the!surrounding!bedrock!is!leached!into! the!subsurface!and!is!incorporated!into!the!speleothem!matrix!(Maher!et!al.,!2014).!It!is! presumed!that!there!is!no!initial!230Th.!The!concentration!of!the!daughter!isotope!230Th! is!directly!related!to!the!decay!of!the!parent!isotopes!238U!and!234U!(Ulusoy!et!al.,!2014).! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 238U! 4.5x109! years! 234Th! 24.1! days! 234Pa! 1.17! minutes! !!!234U! 2.4x105! years! !!!230Th! 7.7x104! years! !!!226Ra! 1600! years! Element!! UP!Uranium! ThP!Thorium! PaP!Protactinium! RaP!Radium! α" α"α" β" β" Figure!2:!Uranium!238!decay!chain!(adopted!from!Ulusoy!et!al.,! 2014).!
  • 13.
    ! 5! ! 1.2.5#Sodium#(Na)# New! Zealand!is! a! narrow! and! seaPsurrounded! landmass! and,! as! such,! atmospheric! particles!delivered!to!land!are!strongly!influenced!by!sea!salts!from!marine!aerosols.!The! soluble!Na!in!aerosols!comes!solely!from!sea!salts,!which!are!higher!in!summer!than!in! winter,!and!higher!at!coastal!regions!relative!to!inland!areas!(Wang!and!Shooter,!2001).! Aerosol!concentrations!of!Na!are!strongly!affected!by!wind!direction!and!mildly!affected! by!wind!speed!(Wang!and!Shooter,!2001).!!Atmospheric!Na!is!transported!by!wind!and! is!dissolved!in!precipitation!and!deposited!on!land.!Na!is!thought!to!be!leached!into!the! subsurface! and! groundwater! and! then! may! be! incorporated! in! speleothems! found! in! caves.!Other!possible!sources!of!Na!in!speleothems!could!come!from!rock!surrounding! the! cave! environment.! This! dissolved! Na! from! the! country! rock! would! be! a! constant! background!phenomenon!and!anomalous!concentrations!might!be!able!to!be!inferred! from!wind!and!storm!events!(Bieniok!et!al.,!2011)! ! 1.2.6#Late#Holocene#climate#and#cycles#in#New#Zealand## In! New! Zealand,! El! Niño! and! La! Niña! cycles! significantly! influence! wind! direction.! El! Niño!and!La!Niña!refer!to!opposite!ends!of!a!climate!spectrum!and!are!weather!patterns! that!occur!periodically!across!the!Pacific!Ocean!characterized!by!variable!levels!of!winds! and! rainfall! in! different! parts! of! New! Zealand! (NIWA).! During! an! El! Niño! event,! New! Zealand! summers! tends! to! experience! stronger/more! frequent! winds! from! the! west,! which!typically!leads!to!a!drought!on!the!east!coast!and!more!rain!on!the!west!coast.!In! winter,!southerly!winds!dominate,!bringing!colder!conditions!to!both!the!land!and!the! surrounding! ocean.! In! spring! and! autumn! southwesterly! winds! are! more! common! (Figure!3).!During!El!Niño!it!is!expected!that!summer!periods!will!result!in!higher!Na! aerosols!on!the!west!coast!and!lower!Na!on!the!east!coast.!Similar!inferences!apply!to! spring!and!autumn,!although!in!lower!concentrations.!Winter!periods!should!result!in! low!Na!aerosols!for!both!east!and!west!coasts.!La!Niña!events!have!contrasting!impacts! on! New! Zealand's! climate.! Northeasterly! winds! dominate,! which! tend! to! bring! rainy! conditions!to!the!northeast!of!the!North!Island,!and!reduced!rainfall!to!the!south!and! southwest!of!the!South!Island.!During!a!La!Niña!event!Na!aerosols!should!be!higher!on! the!east!coast!relative!to!the!west!coast!(Figure!4).!!
  • 14.
    ! 6! ! # # # # # # # # # ! In!1997–1998!there!was!a!strong!documented!El!Niño!event!that!caused!severe! droughts!and!floods!in!New!Zealand.!New!Plymouth!on!the!west!coast!of!the!North! Island!had!high!rainfall!events!with!some!days!reaching!a!maximum!rainfall!of!480!mm.! During!this!period,!Napier!on!the!east!coast!on!the!North!Island!had!relatively!very!little! rainfall!with!a!maximum!rainfall!for!a!given!day!of!28!mm.!(The!National!Climate! Database!(NIWA);!retrieved!15!August!2015)!(Figures!5!and!6).! # # Figure!3:!Typical!El!Niño!wind! anomalies!(adopted!from!NIWA).! Figure!4:!Typical!La!Niña!wind! anomalies!(adopted!from!NIWA).! Figure!5:!Rainfall!pattern!for!New!Plymouth!(west!coast)!during!the!1997–1998!El!Niño! event!(The!National!Climate!Database!(NIWA);!retrieved!15!August!2015).! 0" 100" 200" 300" 400" 500" 17/12/95" 4/07/96"20/01/97" 8/08/97" 24/02/98" 12/09/98" 31/03/99" 17/10/99" Precipita)on,(mm), Date,
  • 15.
    ! 7! # # 1.2.6#Storm#events# 1.2.6.1%Historic%storm%events%% Between! December!and! April,! storms! from! the! tropics! move! south! towards! New! Zealand.! As! these! storms! reach! New! Zealand! waters,! they! bring! damaging! winds! and! heavy!rain.!In!April!1968,!Tropical!Cyclone!Gisele!moved!over!New!Zealand,!producing! winds!gusting!to!75!m/s!in!Wellington!(Sinclair,!1993).!Cyclone!Bola!precipitated!over! 900! mm! of! rain! and! produced! hurricanePforce! winds! in! regions! of! northern! New! Zealand! in! March! 1988! (Sinclair,! 1993),! More! recently,! Cyclones! Fergus! and! Drena! brought!heavy!rain!and!stormPforce!winds!to!the!North!Island!in!December!1996.!New! Zealand’s! climatic! records! of! such! events! are! stored! on! a! National! Climate! Database! (CliFlo).!CliFlo!is!a!web!system!and!stores!climatic!records!from!as!early!as!1850.!CliFlo! generates! outputs! that! are! hourly! to! yearly! raw! data.! The! tropical! cyclones! (Drena,! Gisele,!Fergus!and!Bola)!are!recorded!in!CliFlo!as!shown!in!Table!1.! ! !10$ 0$ 10$ 20$ 30$ 40$ 50$ 60$ 70$ 80$ 90$ 100$ 1/01/95$ 20/07/95$ 5/02/96$ 23/08/96$ 11/03/97$ 27/09/97$ 15/04/98$ 1/11/98$ Precipita)on,(mm), Date, Figure!6:!Rainfall!pattern!for!Napier!(east!coast)!during!the!1997–1998!La!Niña!event!(The! National!Climate!Database!(NIWA);!retrieved!15!August!2015).!
  • 16.
    ! 8! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Table!1:!Cyclones!A)!Drena,!B)!Gisele,!C)!Bola,!and!D)!Fergus!recorded!by!NIWA!using! wind!speed!data!(The!National!Climate!Database!(NIWA);!retrieved!26!June!2015).! ! ! ! ! ! ! ! % % % % % % % % Station Date(NZST) Time(NZST) Speed(m/s) 26/12/96 8:00 0 27/12/96 8:00 3.1 28/12/96 8:00 0 29/12/96 8:00 2.6 30/12/96 8:00 4.6 31/12/96 8:00 6.7 1/01/97 8:00 3.1 2/01/97 8:00 3.6 3/01/97 8:00 0 Whakatane4Aero Station Date(NZST) Time(NZST) Speed(m/s) 1/01/97 8:00 2.6 2/01/97 8:00 2.6 3/01/97 8:00 2.6 4/01/97 8:00 2.6 5/01/97 8:00 6.7 6/01/97 8:00 2.6 7/01/97 8:00 2.6 8/01/97 8:00 2.6 9/01/97 8:00 2.6 10/01/97 8:00 2.6 11/01/97 8:00 15.4 12/01/97 8:00 2.6 13/01/97 8:00 1 14/01/97 8:00 0 Te0Kuiti0High0School Station Date(NZST) Time(NZST) Speed(m/s) 4/03/88 8:00 4.6 5/03/88 8:00 0 6/03/88 9:00 4.6 7/03/88 9:00 6.7 8/03/88 9:00 9.8 9/03/88 9:00 12.4 10/03/88 9:00 2.6 11/03/88 9:00 4.6 12/03/88 9:00 6.7 13/03/88 9:00 4.6 Napier4Nelson4Park Station Date(NZST) Time(NZST) Speed(m/s) 5/04/68 9:00 4.1 6/04/68 9:00 3.1 7/04/68 9:00 2.6 8/04/68 9:00 3.6 9/04/68 9:00 7.7 10/04/68 9:00 2.1 11/04/68 9:00 0.5 12/04/68 9:00 3.1 13/04/68 9:00 3.6 New1Plymouth1Aero A)"Drena"(09"January"1997)" " ! B)"Gisele"(9/10"April"1968)" ! C)"Bola"(4"March"1988)" " " ! D)"Fergus"(30"December"1996)" " " ! Figure,7:"Landslides"and"soil"erosion"on"the"east"coast"of"New" Zealand"after"Cyclone"Bola""(Manatū"Taonga"Ministry"for"Culture" and"Heritage)."
  • 17.
    ! 9! 1.2.6.2%Prehistoric%storm%events% It!is!difficult!to!identify!prehistoric!storm!events.!However,!storm!events!cause!massive! landslips! and!slides,! which! may! be! recorded! in! geomorphic! and! geological! features! (Figure! 7)! ! (Manatū! Taonga! Ministry! for! Culture! and! Heritage).! A! fraction! of! New! Zealand’s!prehistoric!storm!events!are!recorded!by!lake!sediments!on!the!eastern!side!of! the!North!Island!at!Lake!Tutira.!Lake!Tutira!terrigenous!deposits!are!a!direct!response! to! rainfall! induced! erosion! (Page! et! al.,! 2010).! Sedimentary! cores! were! analysed! and! dated!back!to!ca.!7200!a.!The!cores!contain!very!abrupt!sedimentary!packages!recording! storm! events.! Numerous! stormy! periods! were! recorded! as! listed! in! Table! 2.! This! prehistoric!record!provides!a!template!with!which!to!compare!the!results!of!this!thesis! research.! Storm!Periods!(AD)! Duration!(yr)! 1750–1650! 100! 1570–1540! 30! 1450–1270! 180! 830–680! 150! 550–470! 80! 120–0! 120! ! Table!2:!Storm!periods!identified!from!sedimentary!deposits!in!Lake!Tutira!(Page!et!al.,! 2010).! # # 1.3#Structure#of#thesis# This!thesis!is!structured!and!presented!as!follows:!! Chapter!1!introduces!this!thesis!by!presenting!the!main!objectives!of!this!research.!It! then!provides!a!synthesis!of!relevant!background!material.! Chapter!2!describes!the!samples!that!were!analysed!as!part!of!this!study,!justifies!the! sample! selection,! and! details! the! analytical! methods! that! were! used! to! collect! and! process!the!data.!! Chapter!3!presents!the!geochemical!results!obtained!on!the!two!speleothems.!! Chapter!4!discusses!the!results!in!terms!of!whether!it!is!possible!to!use!the!geochemistry! of!speleothems!to!track!paleoPwind!and!Pstorm!events.!
  • 18.
    ! 10! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!2!! ! 2.0!Methodology! ! 2.1!Selection!of!the!speleothems!for!study! Two!speleothems!were!selected!from!the!University!of!Auckland!speleothem!collection! according! to!their! geographical! locations! (Figure! 8)! and! age.! Two! speleothems! were! selected! from! the! (near)! west! (Waitomo)! and! east! coast! (Wairoa)! regions! of! North! Island,! New! Zealand,! which! had! previously! been! dated! by! uraniumGseries! techniques.! The! two! study! sites! are! both! warm,! temperate! regions! and! experience! high! average! rainfall,!but!different!wind!patterns.!The!Waitomo!region!experiences!an!average!annual! temperature!of!22.2°C!and!an!average!rainfall!of!1102!mm!per!year.!Wairoa!experiences! an!annual!temperature!of!22.5°C!and!a!slightly!higher!average!rainfall!of!1187!mm!per! year!(Metservice);!retrieved!17!September!2015).!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Figure!8:!Map!of!the!North!Island!showing!the!location!of! speleothem!samples!(grey)!and!major!cyclone!events!(blue).! ! ! 1968% Gisel e% %1988% Bola% ! 1996% Fergus% ! 1996% Dren a% GG5! DS! !!N! 200km!
  • 19.
    ! 11! 2.2!Speleothem!GG5!(Waitomo)! The!speleothem!GG5!was!collected!by!Prof.!Paul!Williams!in!2005!from!Gardeners!Gut! cave!in!Waitomo!near!the!west!coast!of!North!Island.!!Gardeners!Gut!cave!has!a!passage! length!of!12.2!km!and!is!120–180!m!above!sea!level.!The!cave!is!35!km!inland!and!is! developed!in!gently!dipping!Oligocene!limestones,!overlain!by!Miocene!siltstones!and! volcanic!ash!soils!(P.!Williams,!pers.!comm.).!GG5!was!actively!growing!at!the!time!of! collection!and!is!75!mm!in!length,!with!clear!growth!bands!(P.!Williams,!pers.!comm.).! U/Th!dating!of!the!speleothem!indicates!that!the!interior!dates!back!to!12200!±!300!yr! (Figure!9).!However,!there!is!a!significant!hiatus!in!growth!at!ca.!5000!yr,!marked!by!a! distinct!change!in!the!colour!of!the!growth!bands!at!a!depth!of!45!mm!(Figure!9).!The! outer!45!mm!of!the!speleothem!provides!a!highGresolution!record!from!2300!yr!BP!to! the!modern!day!as!it!was!actively!dripping!at!the!time!of!sampling.! ! 2.2.1!GG5!sample!preparation! GG5! was!prepared! by! cutting! through! the! sample! with! a! diamond! saw! perpendicular! to! the!growth!bands.!It!was!then!mounted!flat!on! a!glass!slide!and!the!surface!was!polished!and! cleaned.!The!smooth!surface!was!microGdrilled,! and! previously! dated! by! U/Th! series! techniques! using! a! thermal! ionisation! mass! spectrometer! (TIMS).! Prior! to! trace! element! analysis! the! surface! of! the! speleothem! was! cleaned! with! methanol! and! preGablated! to! remove! any! surficial! contamination.! The! preG ablated! surface! was! then! reGablated! and! analysed.! ! ! ! ! ! ! Figure!9:!HighGresolution!crossGsectional! view!of!GG5,!showing!clear!growth!bands! with!annotated!uraniumGseries!dates.!! 1.680%ka% 2.012%ka% 2.334%ka% 1.207%ka%
  • 20.
    ! 12! 2.3!Speleothem!DS!(Wairoa)! The!speleothem!DS!was!collected!by!Prof.!Paul!Williams!in! 1992!from!the!east!coast!of!New!Zealand!in!Disbelief!Cave.! Disbelief!Cave!is!located!in!the!Wairoa!River!catchment!ca.! 29! km!northeast! of! Wairoa! township! in! northern! Hawkes! Bay.!The!cave!is!approximately!120!m!long!and!600!m!above! sea!level!and!developed!in!Late!Pliocene!limestone,!which!is! overlain! by! early! Pleistocene! sediments! (P.! Williams,! pers.! comm.).! DS! is! a! flowstone/shawl! that! was! not! actively! growing!at!the!time!of!collection.!It!has!been!dated!by!TIMS! techniques! to! be! ca.! 7600! yr! BP! in! age! and! the! tip! of! the! speleothem!is!<1000!yr!BP!in!age!! (P.! Williams,! pers.! comm.).! Speleothem! DS! is! 150! mm! in! length! with! clear! growth! bands! throughout! the! sample! (Figure!10).!! ! 2.3.1!DS!sample!preparation! Due!to!this!speleothem!being!very!fragile,!it!was!embedded! in! epoxy! resin,! which! supported! its! structure! prior! to! cutting.! DS! was! then! prepared! by! cutting! through! the! sample! with! a! diamond! saw! perpendicular! to! the! growth! axis,!in!close!proximity!to!the!regions!microGmilled!for!U/Th! series!dating!(Figure!10).!The!sample!was!then!polished!and! cleaned.! DS! was! then! mounted! in! preparation! for! trace! element! analysis.! Prior! to! ablation,! the! surface! of! the! speleothem!was!once!again!cleaned!with!methanol!and!preG ablated!to!minimise!surficial!contamination.!! ! The!time!interval!chosen!for!analysis!in!both!speleothems!is! 0–800! AD,! given! that! both! samples! have! similar! growth! rates!over!this!time!period.!! ! ! Figure!10:!HighGresolution!crossG sectional!view!of!DS!with! annotated!uraniumGseries!dates.!
  • 21.
    ! 13! ! 2.4!Data!collection!techniques! ! 2.4.1!Laser!ablation!inductively!coupled!plasma!mass!spectrometry! Trace! element!analysis! was! undertaken! by! laser! ablation! inductively! coupled! plasma! mass! spectrometry! (LAGICPGMS)! at! Victoria! University! of! Wellington.! This! system! comprises!a!Resonetics!S155GSE,!193!nm!excimer!laser!ablation!system!coupled!to!an! Agilent!7500!series!ICPMS.!This!is!an!analytical!technique!with!excellent!sensitivity,!high! analytical! throughput! and! high! spatial! resolution.! Calibrated! standards! were! run! as! unknowns!to!monitor!instrumental!drift!and!the!precision!and!accuracy!of!the!ICPGMS! throughout!analytical!sessions.!The!reference!material!used!for!this!study!are!the!NIST! 610!standard,!NIST!612!standard!and!MACS3,!and!reference!data!for!these!standards! were! acquired! from! georem.mpchGmainz.gwdg.de.! Data! for! the! NIST! standards! are! summarized!in!Tables!3!and!4.!NIST!610!standard!was!used!as!the!primary!calibrating! standard,!whereas!NIST!612!was!used!to!confirm!the!accuracy!and!the!precision!of!the! data.! ! NIST!610! Element! Value! Uncertainty! Unit! Ba! 452! 9! µg/g! Mg! 432! 29! µg/g! Na2O! 13.4! 0.3! %m/m! Sr! 515.5! 1! µg/g! U! 461.5! 1! µg/g! ! ! Table!3:!Reference!values!for!NIST!SRM610!(GeoReM,!2015).!! ! NIST!612! Element! Value! Uncertainty! Unit! Ba! 39.3! 0.9! µg/g! Mg! 68! 5.1! µg/g! Na2O! 13.7! 0.3! %m/m! Sr! 78.4! 0.2! µg/g! U! 37.38! 1.2! µg/g! ! ! Table!4:!Reference!values!for!NIST!SRM612!(GeoReM,!2015).!!
  • 22.
    ! 14! Inductively! coupled!plasma! mass! spectrometry! (ICPGMS)! is! a! technique! capable! of! detecting!metals!and!several!nonGmetals!at!concentrations!as!low!as!one!part!in!1015! (ppq)!on!nonGinterfered!lowGbackground!isotopes.!This!can!be!achieved!by!firing!a!laser! beam!onto!the!surface!of!the!speleothem,!with!the!energy!of!the!laser!beam!transferred! to!the!speleothem!and!causing!material!to!be!removed/ablated.!The!ablated!material!is! transported! by! a! flow! of! helium! gas! passing! through! the! sample! chamber! and! transported!to!an!ICPGMS.!As!the!material!passes!into!the!plasma!of!the!ICPMS,!elements! are!ionized.!The!ions!are!separated!in!the!mass!spectrometer!according!to!their!massGtoG charge!ratio!and!then!detected!and!counted!on!an!electron!multiplier!detector.! ! ! ! ! ! ! ! ! ! ! ! ! Figure!11:!Schematic!of!an!ICPGMS!experimental!setup!(Latkoczy!and!Ghislain,!2006).! ! ! ! ! ! ! ! ! ! ! !
  • 23.
    ! 15! ! 2.5!Data!processing!techniques! ! 2.5.1!Iolite!data!processing! ! All! the!raw! LAGICPGMS! data! were! processed! using! Iolite! software.! Iolite! is! data! processing!software!used!for!large!mass!spectrometry!datasets!(Paton!et!al.,!2011).!The! data! processing! involves! a! background! correction! as! well! as! normalising! the! trace! element!ratios!from!the!speleothems!to!the!ratios!measured!in!the!NIST!610!standard! relative!to!their!known!values!(Table!3).! !
  • 24.
    ! 16! !!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!3!! ! 3.0!Results! This!chapter! presents! detailed! geochemical! data! for! the! Wairoa! and! Waitomo! speleothems.!The!data!was!collected!by!ICP=MS!methods!and!processed!using!Iolite!as! described!in!Chapter!Two.! !! 3.1!Trace!element!data!normalised!to!Ca! The!Wairoa!and!Waitomo!speleothems!are!largely!comprised!of!calcium!carbonate!and! thus!the!measured!trace!element!data!are!presented!normalised!to!calcium.!This! technique!is!a!conventional!method!used!in!speleothem!science!(Fairchild!et!al.,!2012;! Huang!et!al.,!2001).!! ! ! Figure!12:!Time=series!of!Na/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From!0–800!AD!Na/Ca!ratios!in!both!the!Wairoa!and!Waitomo!speleothems!have!almost! identical! average! values! (4.34! x! 10–5! and! 4.32! x! 10–5,! respectively).! The! Waitomo! speleothem! has! Na/Ca! ratios! that! vary! from! a! minimum! value! of! 1.59! x! 10=5! ! to! a! maximum!value!of!1.01!x!10–4!!and!there!appears!to!be!cyclical!changes!from!31–110!AD,! 110–142!AD,!142–182!AD!and!182–275!AD.!The!cyclical!variations!are!less!marked!in! 0.00E+00! 2.00E=05! 4.00E=05! 6.00E=05! 8.00E=05! 1.00E=04! 1.20E=04! 1.40E=04! 1.60E=04! 1.80E=04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Na/Ca! Age!(AD)! Waitomo! Na! Wairoa! Na!
  • 25.
    ! 17! the! period!275–714! AD.! There! are! distinct! peaks! in! Na/Ca! ratios! in! the! Waitomo! speleothem!at!110!AD,!142!AD,!182!AD,!275!AD!and!714!AD.!Na/Ca!ratios!in!the!Wairoa! speleothem!in!a!general!sense!behave!similarly!to!that!of!the!Waitomo!Speleothem!and! show!cyclical!variation!between!150–227!AD,!227–261!AD,!261–387!AD,!387–557!AD,! 557–750!AD!and!750–768!AD.!There!are!also!distinct!Na/Ca!peaks!at!150!AD,!227!AD,! 261!AD,!387!AD,!557!AD,!750!AD!and!786!AD!in!the!Wairoa!speleothem.!Na/Ca!ratios!in! the!Wairoa!speleothem!vary!from!a!minimum!value!of!2.14!x!10–5!to!a!maximum!value!of! 3.72!x!10–4.!The!Wairoa!speleothem!has!significantly!higher!Na/Ca!peaks!relative!to!the! Waitomo!speleothem.!In!general,!Na/Ca!peaks!in!the!two!speleothems!do!not!occur!at! the!same!time.!However,!there!are!intervals!where!smaller!scale!Na/Ca!peaks!in!the!two! speleothems!do!correlate!(142–153!AD,!173–210!AD,!239–272!AD,!319–341!AD,!511– 531!AD,!547–557!AD,!659–691!AD,!705–760!AD!and!775–800!AD),!and!there!are!also! intervals!where!the!Na/Ca!ratios!in!the!speleothems!appear!to!be!anti=correlated!(52–72! AD,! 76–101! AD,! 115–126! AD,! 153–157! AD,! 227–239! AD,! 269–289! AD,! 363–393! AD,! 479–491!AD,!534–548!AD,!617–647!AD!and!750–775!AD).! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
  • 26.
    ! 18! ! Figure!13:!Time=series!of!Mg/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From!0–800!AD,!Mg/Ca!ratios!in!both!the!Wairoa!and!the!Waitomo!speleothems!have! very!different!trends!and!values.!The!average!Mg/Ca!value!for!the!Wairoa!speleothem!is! 4.03!x!10–4!and!8.27!x!10–4!for!the!Waitomo!speleothem.!The!Waitomo!speleothem!has!a! minimum!value!of!3.71!x!10–5!and!a!maximum!value!of!1.12!x!10–3.!From!0–400!AD,! Mg/Ca!ratios!in!the!Waitomo!speleothem!increase!substantially!and!then!at!460!AD!the! Mg/Ca!ratios!drop!from!1.06!x!10–3!to!6.73!x!10–4.!!After!the!drop,!Mg/Ca!ratios!increase! back! to!1.03! x! 10–3! for! ~90! years! where! the! Mg/Ca! values! stabilise! and! show! less! variability!until!800!AD.!There!is!no!clear!evidence!for!cyclicity!in!the!Mg/Ca!ratios!of! the! Waitomo! speleothem.! However,! Mg/Ca! ratios! in! the! Wairoa! speleothem! show! clearer!cyclical!trends.!The!Wairoa!speleothem!has!a!minimum!Mg/Ca!value!of!3.09!x! 10–4!and!a!maximum!value!of!7.02!x!10–4!and!peaks!at!52!AD,!154!AD,!257!AD,!384!AD,! 518! AD,! 647! AD,! 693! AD! and! 774! AD.! The! two! Mg/Ca! trends! from! the! different! speleothems!are!not!well!correlated,!and!do!not!show!similar!trends!or!spikes.! ! 4.00E=04! 5.00E=04! 6.00E=04! 7.00E=04! 8.00E=04! 9.00E=04! 1.00E=03! 1.10E=03! 1.20E=03! 2.80E=04! 3.80E=04! 4.80E=04! 5.80E=04! 6.80E=04! 7.80E=04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Mg/Ca! Age!(AD)! Wairoa! Mg! Waitomo! Mg!
  • 27.
    ! 19! ! Figure!14:!Time=series!of!Sr/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From!0–800!AD,!Sr/Ca!ratios!in!both!the!Wairoa!and!the!Waitomo!speleothems!have! significantly! different!average! values! (3.42! x! 10–4! and! 1.04! x! 10–4,! respectively).! Waitomo!Sr/Ca!values!varies!from!a!minimum!value!of!3.77!x!10–5!to!a!maximum!value! of! 1.91! x! 10–4! and! there! are! no! clear! cyclical! changes.! In! the! Waitomo! speleothem! between! 0–350! AD! there! is! more! variation! in! Sr/Ca! ratios! over! shorter! timesclaes! relative! to! 350–800! AD! where! varations! tend! to! be! more! muted.! Sr/Ca! ratios! in! the! Wairoa!speleothem!vary!from!a!minimum!value!of!1.66!x!10–4!to!a!maximum!value!of! 4.73! x! 10–4.! The! Wairoa! speleothem! has! higher! Sr/Ca! ratios! relative! to! the! Waitomo! speleothem.! In! general,! the! trends! for! the! two! speleothems! show! some! degree! of! correlation.! There! appear! to! be! common! trends! for! the! two! speleothems,! with! the! exception!of!between!400–500!AD,!at!0–100!AD,!120–242!AD,!250–400!AD,!500–650!AD! and!650–800!AD.!! ! ! ! ! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 0.00E+00! 1.00E=04! 2.00E=04! 3.00E=04! 4.00E=04! 5.00E=04! 6.00E=04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Sr/Ca! Age!(AD)! Wairoa! Sr! Waitomo! Sr!
  • 28.
    ! 20! ! Figure!15:!Time=series!of!Ba/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! From! 0–800!AD,! Ba/Ca! ratios! in! both! the! Wairoa! and! Waitomo! speleothems! have! significantly! different! average! values! (9.49! x! 10–6! and! 2.82! x! 10–5,! respectively).! The! Waitomo! speleothem! shows! a! slight! trend! to! lower! Ba/Ca! ratios! with! time! that! vary! from!a!minimum!value!of!7.33!x!10–6!to!a!maximum!value!of!5.28!x!10–5.!The!Waitomo! speleothem!shows!slight!cyclical!variations!with!large!peaks!at!75!AD!and!250!AD,!and! smaller!peaks!at!417!AD,!507!AD,!580!AD,!640!AD!and!730!AD.!At!690!AD,!Ba/Ca!ratios! drop!from!2.4!x!10–5!to!7.33!x!10–6!and!steeply!increase!back!to!2.9!x!10–5.!The!Wairoa! speleothem! has! a! slight! increase! in! Ba/Ca! values! through! time! that! vary! from! a! minimum! value! of! 3.48! x! 10–6! to! a! maximum! value! of! 1.67! x! 10–5.! The! Wairoa! speleothem!has!stronger!cyclical!variations!than!that!of!the!Waitomo!speleothem,!with! peaks!in!Ba/Ca!at!90!AD,!180!AD,!265!AD,!310!AD,!357!AD,!435!AD,!547!AD,!622!AD,!684! AD,!714!AD!and!782!AD.!There!are!some!similarities!in!the!data!for!the!two!speleothems! whereby!some!peaks!and!lows!correlate!(e.g.,!67–157!AD!and!693–794!AD).! ! ! ! ! ! ! 0.00E+00! 1.00E=05! 2.00E=05! 3.00E=05! 4.00E=05! 5.00E=05! 6.00E=05! 0.00E+00! 5.00E=06! 1.00E=05! 1.50E=05! 2.00E=05! 0! 100! 200! 300! 400! 500! 600! 700! 800! Ba/Ca! Age!(AD)! Wairoa!Ba! Waitomo! Ba!
  • 29.
    ! 21! ! Figure!16:!Time=series!of!U/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).! ! Average!U/Ca!ratios!in!the!Waitomo!and!Wairoa!speleothems!are!very!different!(6.87!x! 10–8!versus!5.23!x!10–7).!The!Wairoa!speleothem!has!a!wider!range!of!U/Ca!ratios!with!a! minimum!value!of!1.15!x!10–7!and!a!maximum!value!of!8.76!x!10–7!and!exhibits!very! noisy!variations.!There!are!some!clear!U/Ca!peaks!(72!AD,!150!AD,!196!AD,!267!AD,!307! AD,!383!AD,!429!AD,!552!AD,!637!AD,!677!AD!and!753!AD)!and!lows!(109!AD,!149!AD,! 208! AD,!283! AD,! 328! AD,! 397! AD,! 518! AD,! 580! AD! and! 694! AD).! The! Waitomo! speleothem!has!lower!U/Ca!values!than!that!of!the!Wairoa!speleothem!with!a!smaller! range!in!values!from!1.51!x!10–4!to!22!x!10–7.!There!is!a!period!at!660!AD!where!U/Ca! values!in!the!Waitomo!speleothem!increase!significantly!to!4.22!x!10–7,!but!most!peak! U/Ca! values! are! ca.! 1! x! 10–7.! U/Ca! in! the! two! speleothems! do! not! appear! to! exhibit! similar!trends.! ! ! ! ! ! ! ! ! ! 0.00E+00! 5.00E=08! 1.00E=07! 1.50E=07! 2.00E=07! 2.50E=07! 0.00E+00! 2.00E=07! 4.00E=07! 6.00E=07! 8.00E=07! 1.00E=06! 0! 100! 200! 300! 400! 500! 600! 700! 800! U/Ca! Age!(AD)! Wairoa!U! Waitomo! U!
  • 30.
    ! 22! ! 3.2!Trace!elements!normalised!to!Mg! Trace!element!data!for!the!Wairoa!and!Waitomo!speleothems!were!also!normalised!to! Mg!to!examine!how!variations!with!respect!to!this!element!changed!over!time.!! ! ! Figure!17:!Time=series!of!Na/Mg!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).!! ! From!0–800!AD,!Na/Mg!ratios!in!the!Wairoa!speleothem!have!a!slightly!higher!average! value! than!the! Waitomo! speleothem! (1.05! x! 10–1! versus! 5.32! x! 10–2).! The! Waitomo! speleothem!varies!from!a!minimum!value!of!2.51!x!10–2!to!a!maximum!value!of!1.4!x!10–1! and!there!appears!to!be!cyclical!changes!between!31–105!AD,!105–134!AD,!134–142!AD,! 142–182!AD!and!182–275!AD.!The!cyclical!variations!are!less!marked!in!the!period!275– 720!AD.!There!are!distinct!peaks!in!Na/Mg!ratios!for!the!Waitomo!speleothem!at!110! AD,! 142! AD,! 182! AD,! 275! AD! and! 714! AD.! Na/Mg! ratios! in! the! Wairoa! speleothem! behave! similarly! to! the! Waitomo! speleothem,! in! that! it! shows! cyclical! variations! between!150–227!AD,!227–261!AD,!261–!325!AD,!325–387!AD,!387–557!AD,!557–750! AD!and!750–768!AD.!There!are!also!distinct!peaks!at!227!AD,!261!AD,!387!AD,!557!AD,! 750! AD! and! 786! AD.! The! Waitomo! speleothem! has! Na/Ca! ratios! that! vary! from! a! minimum!value!of!6.02!x!10–2!to!a!maximum!value!of!9.58!x!10–1!and!has!significantly! higher!Na/Ca!peaks!relative!to!the!Waitomo!speleothems.!In!general!the!timing!of!the! peaks!in!the!two!speleothems!do!not!correspond!with!each!other.! 0.00E+00! 2.00E=02! 4.00E=02! 6.00E=02! 8.00E=02! 1.00E=01! 1.20E=01! 1.40E=01! 1.60E=01! 0.00E+00! 2.00E=01! 4.00E=01! 6.00E=01! 8.00E=01! 1.00E+00! 1.20E+00! 0! 100! 200! 300! 400! 500! 600! 700! 800! (Na/Mg)! Age!(AD)! Wairoa! Na! Waitomo! Na!
  • 31.
    ! 23! ! Figure! 18:!Time=series!of!Sr/Mg!ratios!in!the!two!speleothems!GG5!(Waitomo;!blue)! and!DS!(Wairoa;!red).! ! From!0–800!AD,!Sr/Mg!ratios!in!both!the!Wairoa!and!the!Waitomo!speleothems!have! significantly! different! average! values! (8.65! x! 10–1! and! 1.27! x! 10–1,! respectively).! The! Waitomo!speleothem!has!Sr/Ca!ratios!that!vary!from!a!minimum!value!of!5.57!x!10–2!to! a! maximum! value! of! 3.12! x! 10–1! and! there! are! no! apparent! cyclical! changes.! In! the! Waitomo!speleothem!between!0–350!AD!there!is!more!variation!over!shorter!timescales! relative!to!350–800!AD!where!varations!tend!change!more!gradually.!Sr/Mg!ratios!in!the! Wairoa!speleothem!vary!from!a!minimum!value!of!3.85!x!10–1!to!a!maximum!value!of! 1.46.! Wairoa! has! higher! Sr/Mg! ratios! relative! to! that! of! the! Waitomo! speleothem.! In! general,! the! trends! of! the! two! speleothem! show! some! degree! of! correlation.! There! appear!to!be!common!trends!for!the!two!speleothems!with!the!exception!of!between!0– 100!AD,!120–242!AD!and!650–800!AD.!! ! ! ! ! ! ! 0.00E+00! 5.00E=02! 1.00E=01! 1.50E=01! 2.00E=01! 2.50E=01! 3.00E=01! 3.50E=01! 0.00E+00! 2.00E=01! 4.00E=01! 6.00E=01! 8.00E=01! 1.00E+00! 1.20E+00! 1.40E+00! 1.60E+00! 0! 100! 200! 300! 400! 500! 600! 700! 800! (Sr/Mg)! Age!(AD)! Wairoa!Sr! Waitomo! Sr!
  • 32.
    ! 24! ! Figure! 19:!Time=series!of!Ba/Mg!ratios!in!the!two!speleothems!GG5!(Waitomo;!blue)! and!DS!(Wairoa;!red).! ! From!0–800!AD,!Ba/Mg!ratios!in!both!the!Wairoa!and!Waitomo!speleothems!have!very! similar! average! values! (2.32! x! 10–2! and! 3.51! x! 10–2,! respectively).! The! Waitomo! speleothem! has! a! slight! negative! trend! in! Ba/Mg! ratios! with! time! that! vary! from! a! minimum!value!of!1.11!x!10–2!to!a!maximum!value!of!1.00!x!10–1.!Waitomo!shows!slight! cyclical!variations!with!large!Ba/Ca!peaks!at!75!AD,!200!AD,!250!AD!and!269!AD!and! smaller!peaks!at!450!AD,!507!AD,!580!AD,!640!AD!and!730!AD.!The!Wairoa!speleothem! has!a!slight!increase!in!Ba/Mg!values!through!time!that!vary!from!a!minimum!value!of! 8.14! x! 10–3! to! a! maximum! value! of! 5.20! x! 10–2.! The! Wairoa! speleothem! has! stronger! cyclical!variations!in!Ba/Ca!ratios!than!in!the!Waitomo!speleothem,!with!peaks!at!34!AD,! 108!AD,!117!AD,!180!AD,!276!AD,!310!AD,!357!AD,!435!AD,!547!AD,!615!AD,!680!AD,!714! AD!and!782!AD.!! ! ! ! ! ! ! ! ! ! 0.00E+00! 2.00E=02! 4.00E=02! 6.00E=02! 8.00E=02! 1.00E=01! 1.20E=01! 0! 100! 200! 300! 400! 500! 600! 700! 800! (Ba/Mg)! Age!(AD)! Waitomo! Ba! Wairoa! Ba!
  • 33.
    ! 25! ! Figure!20:!Time=series!of!U/Mg!ratios!in!the!two!speleothems!GG5!(Waitomo;!blue)!and! DS!(Wairoa;!red).!! ! Average!U/Mg!ratios!in!the!Waitomo!and!Wairoa!speleothems!are!very!different!(8.43!x! 10–5!versus!1.27!x!10–3).!Wairoa!has!a!wider!range!of!U/Ca!ratios!with!a!minimum!value! of!2.45!x!10–4!and!a!maximum!value!of!2.46!x!10–3!and!exhibits!very!noisy!variations.! There!are!some!clear!peaks!(96!AD,!129!AD,!189!AD,!267!AD,!307!AD,!356!AD,!460!AD,! 552!AD,!622!AD,!677!AD!and!753!AD)!and!lows!(37!AD,!109!AD,!159!AD,!220!AD,!283! AD,!328!AD,!391!AD,!518!AD,!554!AD,!694!AD!and!767!AD)!in!U/Ca!ratios.!The!Waitomo! speleothem!has!lower!U/Mg!ratios!than!the!Wairoa!speleothem!with!a!smaller!range!of! values!from!2.04!x!10–5!!!to!4.76!x!10–4.!There!is!a!period!at!660!AD!where!U/Mg!values! increase!significantly!to!4.76!x!10–4,!but!most!peak!U/Mg!values!are!ca.!1!x!10–4.!U/Mg! ratios!in!the!two!speleothems!do!not!appear!to!exhibit!similar!trends.! ! ! ! ! ! ! ! ! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 0.00E+00! 5.00E=04! 1.00E=03! 1.50E=03! 2.00E=03! 2.50E=03! 3.00E=03! 0! 100!200! 300! 400! 500! 600! 700! 800! (U/Mg)! Age!(AD)! Wairoa!U! Waitomo! U!
  • 34.
    ! 26! ! 3.3!Trace!element!correlations! The!following!section!presents!Pearson’s!linear!correlations!between!trace!element!data! in!the!speleothems.!The!Pearson’s!linear!correlation!coefficient!is!a!statistical!measure!of! the!strength!of!a!linear!relationship!between!paired!data.!The!closer!the!value!is!to!1!or!– 1,!the!stronger!the!correlation!between!two!elements.!!Pearson’s!linear!correlation!(R2)! defines!values!of!±0!to!±0.19!as!very!weak,!±0.20!to!±0.39!as!weak,!±0.40!to!±0.59!as! moderate,! ±0.60!to! ±0.79! as! strong! and! ! ±0.80! to! ±1! as! very! strong! correlations.!! Elements! with! strong! correlations! suggest! that! similar! processes! control! their! variability.!! ! !! Na/Ca! Mg/Ca! Sr/Ca! Ba/Ca! U/Ca! Na/Ca! 1! (VW)!!!!! 0.05132! (VW)!!!!! 0.03193! (VW)!!! 0.12207! (W)!!!!!!!! 0.23617! Mg/Ca! (VW)!!!!! 0.08311! 1! (VW)!!!= 0.11014! (W)!!!!= 0.33975! (VW)!!!!= 0.12718! Sr/Ca! (VW)!!!!= 0.00287! (VW)!!!!= 0.11608! 1! (VS)!!!!! 0.83152! (W)!!!!!!!! 0.33829! Ba/Ca! (VW)!!!!! 0.10882! (M)!!!!!!= 0.42067! (VS)!!!!!!! 0.85081! 1! (W)!!!!!!!! 0.35519! U/Ca! (W)!!!!!!!! 0.26525! (VW)!!!!!!!! 0.1521! (W)!!!!!!= 0.21277! (VW)!!= 0.02331! 1! Table! 5:! Pearson!linear!correlation!table!for!elemental!ratios!in!the!two!speleothems! (GG5!=!blue;!DS!=!red)!(VW!=!very!weak,!W!=!weak,!M!=!moderate!and!VS!=!strong).! ! None!of!the!elements!correlate!strongly!except!for!Sr/Ca!and!Ba/Ca!(Waitomo!–!0.85;! Wairoa!–!0.83).!A!weak!positive!correlation!is!observed!in!the!Wairoa!speleothem!for! U/Ca!with!Sr/Ca!and!Ba/Ca!(0.34!and!0.36)!and!a!weak!negative!correlation!for!Ba/Ca! with! Mg/Ca! (–0.34).! ! A! weak! negative! correlation! is! observed! in! the! Waitomo! speleothem!for!Ba/Ca!and!Mg/Ca!(–0.42).!There!are!no!element!ratios!that!have!a!strong! or!moderate!correlation!with!Na/Ca,!although!a!weak!correlation!is!exhibited!between! Na/Ca!and!U/Ca!in!both!speleothems.! ! !
  • 35.
    ! 27! ! Figure!21:!Mg/Ca!versus!Na/Ca!ratios!for!speleothem!DS!from!Wairoa.! ! The! R2!(0.05)! value! for! Mg/Ca! and! Na/Ca! illustrates! that! there! is! no! statistical! correlation!between!the!two!ratios.!However,!qualitatively!there!appears!to!be!a!cluster! of!values!for!Na/Ca!from!2.43!x!10–5!to!6.58!x!10–5!and!Mg/Ca!from!3.15!x!10–4!to!5.53!x! 10–4.!! ! ! ! ! ! ! ! 0.00E+00! 2.00E=04! 4.00E=04! 6.00E=04! 8.00E=04! 1.00E=03! 1.20E=03! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 3.50E=04! 4.00E=04! Mg/Ca! Na/Ca! Wairoa!
  • 36.
  • 37.
    ! 29! ! ! Figure!23:!U/Ca!versus!Na/Ca!ratios!for!speleothem!DS!from!Wairoa.! ! The!R2! (0.2)! value! for! U/Ca! and! Na/Ca! illustrates! that! there! is! statistically! a! weak! correlation!between!the!two!ratios,!which!is!also!evident!from!Fig.!25.!There!appears!to! be!a!cluster!of!values!for!Na/Ca!from!2.38!x!10–5!to!7.62!x!10–5!and!U/Ca!from!2.09!x!10–7! to!8.66!x!10–7.! 0.00E+00! 2.00E=07! 4.00E=07! 6.00E=07! 8.00E=07! 1.00E=06! 1.20E=06! 0.00E+00! 5.00E=05! 1.00E=04! 1.50E=04! 2.00E=04! 2.50E=04! 3.00E=04! 3.50E=04! 4.00E=04! U/Ca! Na/Ca! Wairoa!
  • 38.
    ! 30! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!4!! ! 4.0!Discussion! The! trace!elements! magnesium! (Mg),! strontium! (Sr)! and! barium! (Ba)! have! been! measured!routinely!in!speleothem!studies!worldwide!(Fairchild!et!al.,!2012;!Orland!et! al.,! 2014;! Huang! et! al.,! 2001).! The! chemistry! of! these! three! elements! is! quite! well! understood! and! much! is! known! about! what! controls! their! incorporation! into! speleothems.! As! such,! this! discussion! first! focuses! on! the! similarities! and! differences! observed!between!the!two!speleothems!with!regards!to!Mg,!Sr!and!Ba.!It!then!continues! by!focusing!on!paleoclimatic!interpretations!from!Mg,!Sr!and!Ba.!The!last!section!of!this! discussion!then!explores!the!main!focus!of!this!thesis!by!examining!if!Na!can!be!used!to! track!paleoNstorm!and!Nwind!events.! ! 4.1!Similarities!and!differences!in!Mg/Ca,!Sr/Ca,!and!Ba/Ca!values!in!Waitomo!and! Wairoa!speleothems! ! Figure!24:!TimeNseries!of!Mg/Ca!ratios!for!the!speleothems!GG5!(Waitomo;!blue)!and! DS!(Wairoa;!red).! ! ! ! ! 4.00EN04! 5.00EN04! 6.00EN04! 7.00EN04! 8.00EN04! 9.00EN04! 1.00EN03! 1.10EN03! 1.20EN03! 2.80EN04! 3.80EN04! 4.80EN04! 5.80EN04! 6.80EN04! 7.80EN04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Mg/Ca! Age!(AD)! Wairoa! Mg! Waitomo! Mg!
  • 39.
    ! 31! The! firstNorder!observation! for! the! Mg/Ca! record! in! the! two! speleothems! is! that! the! Waitomo!speleothem!has!significantly!higher!Mg!concentrations!as!compared!with!that! of!the!Wairoa!speleothem.!The!Waitomo!speleothem!has!a!higher!average!Mg/Ca!of!8.3!x! 10N4,! whereas! the! average! Mg/Ca! ratio! in! the! Wairoa! speleothem! is! 4.0! x! 10N4.! The! difference!in!this!ratio!could!be!due!to!differences!of!the!two!sites!in!terms!of:! 1. The!depth!of!the!cave!(hydrology).! 2. The!amount!of!precipitation!(climate).! As!meteoric!water!percolates!through!the!rocks!overlying!a!cave!it!incorporates!Mg.!If! there!is!less!precipitation!it!takes!longer!for!the!water!to!percolate!through!the!overlying! rocks!and!thus!higher!Mg/Ca!ratios!are!expected.!The!same!process!can!be!envisaged!to! occur! for! deeper! cave! systems,! as! the! meteoric! water! has! to! pass! through! a! greater! volume! of! overlying! rock! and,! therefore,! the! deeper! the! cave,! the! higher! the! Mg/Ca! values.!The!annual!rainfall!at!Waitomo!is!1102!mm/yr!and!Wairoa!has!a!similar!average! rainfall!of!1187!mm/yr!(Metservice);!retrieved!17!September!2015).!When!Prof.!Paul! Williams!collected!the!Waitomo!(GG5)!and!Wairoa!(DS)!speleothems!he!noted!that!the! Waitomo! cave! was! 50! m! below! the! surface,! whereas! the! Wairoa! cave! was! just! 10! m! below! the! surface.! The! annual! rainfalls! for! Waitomo! and! Wairoa! are! less! than! 10%! different!and!are!broadly!similar,!thus!the!different!average!Mg/Ca!ratios!for!Waitomo! (GG5)!and!Wairoa!(DS)!most!likely!reflects!cave!depth,!rather!than!regional!climate!(i.e.,! precipitation)!variations.!! !! A!secondNorder!observation!of!the!Mg/Ca!record!for!the!two!speleothems!is!that!there! are!cyclical!variations!superimposed!on!these!larger!scale!differences!in!Mg/Ca!values.! Mg/Ca! ratios! in! the! Wairoa! speleothem! show! clear! cyclical! variations! with! distinct! peaks,!whereas!the!Mg/Ca!ratios!in!the!Waitomo!speleothem!do!not!show!clear!cyclical! changes.!The!Mg/Ca!ratios!in!the!Wairao!speleothem!have!an!average!cyclical!time!of!ca.! 100!yr!between!the!peaks!(50–154!AD,!154–270!AD,!270–380!AD,!380–520!AD,!520– 660! AD,! 660–700! AD! and! 700–770! AD).! The! absence! of! cyclical! variations! in! Mg/Ca! ratios!in!the!Waitomo!speleothem!may!be!due!to:!! 1. A!more!stable!regional!climate!at!Waitomo!as!compared!with!Wairoa.! 2. The!sensitivity!of!the!cave’s!hydrological!system!to!overlying!changes!in!regional! climate!such!as!mean!annual!rainfall.!
  • 40.
    ! 32! The!Wairoa!and!Waitomo!regions!are!not!located!far!away!from!each!other!(Figure!8).! Events! that!affect! the! amount! of! precipitation! and! wind! such! as! El! Niño! and! La! Niña! events!should!be!recorded!in!both!speleothems.!With!prehistoric!storm!events!recorded! in!Lake!Tutira!(Page!et!al.,!2010)!and!historic!wind!anomalies!recorded!by!the!National! Climate!Database!it!is!clearly!evident!that!climate!varies!and!has!not!been!stable!over! the!course!of!the!period!0N800!AD.!Variations!in!Mg/Ca!for!each!speleothem!are!most! likely!responses!to!climate!variations.!However,!the!Wairoa!speleothem!appears!to!be!a! more! sensitive! archive! that! better! records! climatic! change! relative! to! the! Waitomo! speleothem.! Again,! this! sensitivity! may! be! a! reflection! of! the! Wairoa! cave! being! a! shallower!system!than!that!at!Waitomo.! ! Hellstrom! et! al.! (2000)! carried! out! an! ICPNMS! trace! element! study! of! a! speleothem,! which!was!a!flowstone!collected!from!a!deep!cave!system!200!m!below!the!surface!on! the! west! coast! of! the! South! Island,! New! Zealand! in! Nettlebed! cave.! The! speleothem! covered! 30,000! yr! of! growth! and! thus! showed! trace! element! (Mg,! Sr,! Ba! and! U)! variations!between!glacial!and!interglacial!periods.!Hellstrom!et!al.!(2000)!found!that! trace!element!chemistry!showed!glacial!conditions!rapidly!ended!around!15,000!yr!BP.! This!change!from!glacial!to!interglacial!conditions!is!marked!by!increases!and!decreases! in!different!trace!elements.!During!the!glacial!period!there!are!relatively!higher!Mg!and! U!concentrations!and!relatively!lower!Ba!and!Sr!concentrations.!! ! ! ! Glacial! ! Interglacial! Change!in!magnitude!from!glacial! to!interglacial!period! Concentration! Normalised! to!Ca! Concentratio n! Normalised! to!Ca! Concentratio n! Normalised! to!Ca! Percentage! Mg! 470!ppm!! 1.2!x!10N3! 340!ppm! 8.5!x!10N4! 130!ppm! 3.3!x!10J4! 38.8%! U! 125!ppb! 3.1!x!10N7! 55!ppb! 1.4!x!10N7! 70!ppb! 1.8!x!10J7! 128.6%! Ba! 1900!ppb! 4.8!x!10N6! 3000!ppb! 7.5!x!10N6! 1100!ppb! 2.8!x!10J6! 37.3%! Sr! 25!ppm! 6.3!x!10N5! 36!ppm! 9.0!x!10N5! 11!ppm! 2.8!x!10J5! 31.1%! Table! 6:! Mg,! U,! Ba! and! Sr! concentrations! and! element/Ca! ratios! in! a! South! Island! speleothem.!Highlighted!values!show!the!change!from!glacial!conditions!to!interglacial! conditions!for!this!relatively!deep!cave!system!(adopted!from!Hellstrom!et!al.,!2000).!!
  • 41.
    ! 33! ! Figure!25:!TimeNseries!of!Mg/Ca!ratios!for!the!speleothems!GG5!(Waitomo;!blue)!and! DS!(Wairoa;!red).!Also!shown!are!the!magnitude!of!the!glacial!and!interglacial!changes!in! Mg/Ca!values!from!a!South!Island!(Nettlebed)!speleothem!(Hellstrom!et!al.,!2000).! ! The! Nettlebed!speleothem! shows! significant! Mg/Ca! variations! associates! with! large! climate! variations! from! the! most! recent! glacial! to! interglacial! period.! The! Waitomo! speleothem!has!similar!average!Mg/Ca!values!to!the!Nettlebed!speleothem.!The!largest! change!in!Mg/Ca!values!for!the!Waitomo!speleothem!is!3.5!x!10N4!and!for!the!Wairoa! speleothem! is! 2.4! x! 10N4.! These! changes! are! broadly! similar! in! magnitude! to! those! observed! in! the! Nettlebed! speleothem,! despite! the! fact! that! both! the! Waitomo! and! Wairoa!speleothems!grew!wholly!within!the!Holocene!(0–800!AD).!For!some!reason,!the! chemistry! of! the! Waitomo! and! Wairoa! speleothems! are! more! sensitive! to! change! in! climate! than! the! Nettlebed! speleothem.! A! plausible! reason! for! the! large! variations! in! Mg/Ca! ratios! for! the! Waitomo! and! Wairoa! speleothems! is! that! they! reflect! more! sensitive!recorders!to!climate!variations!due!to!their!relative!shallow!cave!depth!relative! to! the! Nettlebed! speleothem.! Similar! size! magnitude! variations! are! observed! in! the! Nettlebed!speleothem,!which!is!known!to!cover!large!climate!variations!between!glacial! and!interglacial!periods!(Hellstrom.,!et!al,!2000).!!! ! ! ! ! 4.00EN04! 5.00EN04! 6.00EN04! 7.00EN04! 8.00EN04! 9.00EN04! 1.00EN03! 1.10EN03! 1.20EN03! 2.80EN04! 3.80EN04! 4.80EN04! 5.80EN04! 6.80EN04! 7.80EN04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Mg/Ca! Age!(AD)! Wairoa! Mg! Waitomo! Mg! 28.2%! 41.1%! Glacial!value:!1.2$x$10 '3$ !!! Interglacial!value:!8.5$x$10 '4$ Magnitude$change:$38.8%!
  • 42.
    ! 34! !! Na/Ca!Mg/Ca! Sr/Ca! Ba/Ca! U/Ca! Na/Ca! 1! 0.05! 0.03! 0.12! 0.24! Mg/Ca! 0.08! 1! –0.11! –0.34! N0.13! Sr/Ca! –0.00! N0.12! 1! 0.83! 0.34! Ba/Ca! 0.11! –0.42! 0.85! 1! 0.36! U/Ca! 0.27! 0.15! –0.21! –0.02! 1! Table! 7:! Pearson! linear! correlation! table! for! selected! element/Ca! ratios! in! the! two! studied!speleothems!(GG5!=!blue;!DS!=!red).! ! Sr/Ca! and! Ba/Ca! are! well! correlated! in! both! the! Waitomo! and! Wairoa! speleothems! (Table!7).!As!such,!discussion!of!Sr/Ca!ratios!can!be!combined!with!that!for!Ba/Ca!ratios.!! ! ! Figure!26:!TimeNseries!of!Sr/Ca!ratios!for!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).!! ! The!Waitomo!and!Wairoa!speleothems!have!very!different!Sr!concentrations!compared! with! the! Nettlebed! speleothem.! However,! the! Waitomo! speleothem! has! Sr/Ca! values! closer!to!the!Nettlebed!speleothem!relative!to!the!Wairoa!speleothem.!Cave!depth!could! be!a!plausible!factor!to!this!variation!as!the!Waitomo!cave!system!is!deeper!than!the! Wairoa!cave.!The!annual!rainfall!for!Nettlebed!is!812!mm/yr!(Metservice);!retrieved!17! September!2015).!!Therefore,!another!reason!for!the!Sr/Ca!variations!could!be!that!the! Waitomo!and!Wairoa!regions!experience!slightly!higher!average!rainfalls!as!mentioned! previously,!and!thus!have!a!warmer!and!wetter!climate!relative!to!the!Nettlebed!region.!! ! 0.00E+00! 5.00EN05! 1.00EN04! 1.50EN04! 2.00EN04! 2.50EN04! 0.00E+00! 1.00EN04! 2.00EN04! 3.00EN04! 4.00EN04! 5.00EN04! 6.00EN04! 0! 100! 200! 300! 400! 500! 600! 700! 800! Sr/Ca! Age!(AD)! Wairoa! Sr! Waitomo! Sr! 277.8%! 168.9%! Glacial!value:!6.3$x$10 '5 $ Interglacial!value:!9.0$x$10 '5$ Magnitude$change:$31.1%$ !
  • 43.
    ! 35! ! 4.2!Paleoclimate!inferences!from!Mg/Ca,!Ba/Ca!and!Sr/Ca!ratios! These! three!element/Ca! ratios! have! been! chosen! to! infer! paleoclimate! because! they! have!been!previously!well!studied!and!understood!(Fairchild!et!al.,!2012;!Orland!et!al.,! 2014;!Huang!et!al.,!2001),!and!are!now!conventionally!used!as!paleoclimate!indicators.! ! Huang! et! al.! (2001)! investigated! the! variations! in! trace! element! concentrations! in! speleothems!from!the!Ernesto!cave!(northeast!Italy).!The!results!showed!that!Mg!largely! has!a!negative!covariation!with!Sr!in!bandings!formed!in!the!1990s,!and!a!positive!coN variation! with! bandings! formed! in! the! 1960s.! These! were! in! response! to! changes! in! hydroNenvironmental!conditions!and!climate!variations.!Therefore,!it!has!been!proposed! that! during! cold–dry! periods,! speleothems! will! have! relatively! high! Mg/Ca! with! relatively! high! Sr/Ca! and! Ba/Ca! ratios.! On! short! timescales,! New! Zealand’s! warm! periods! are! associated! with! less! rainfall! (warm/dry),! whereas! cold! periods! are! associated!with!more!rainfall!(cold/wet).!The!resolution!of!the!dataset!presented!in!this! study!is!only!applicable!to!larger!timescales!and!therefore!the!assumption!of!warm/wet! periods!and!cold/dry!periods!are!applicable.! ! In! the! Waitomo! speleothem,! Mg/Ca! ratios! increase! between! 250–400! AD! and! Sr/Ca! ratios!decrease!between!250–400!AD!(Figures!25!&!26).!However,!Sr/Ca!ratios!do!not! drastically!decrease.!This!subdued!inverse!relationship!indicates!that!during!the!period! of! 250–400! AD,! Mg/Ca! ratios! changed! in! response! to! climate! change.! Therefore,! between! 250–400! AD! there! would! have! been! less! rainfall,! with! moderately! warmer! temperatures.!Between!700–710!AD!and!460–480!AD!Mg/Ca!ratios!increase,!whereas! Sr/Ca! ratios! are! relatively! low.! These! periods! represents! a! time! of! less! rainfall! and! relatively!warmer!conditions.!! ! For! the! Wairoa! speleothem,! periods! between! 60–140! AD,! 160–250! AD,! 260–370! AD,! 400–500! AD,! 540–630! AD! and! 700–780! AD! have! relatively! low! Mg/Ca! ratios! and! periods! between! 60–100! AD,! 260–360! AD,! 410N507! AD,! 540–620! AD! have! relatively! high!Sr/Ca!ratios.!!These!periods!reflect!warmer!and!wetter!conditions!(Figure!27).!
  • 44.
    ! 36! ! Figure!27:!TimeNseries!of!Mg/Ca!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;! red).!The! timeNseries! highlights! peaks! in! Mg! for! the! Wairoa! speleothem! showing!warm–wet!climatic!conditions!(red!triangles)!and!periods!noted!as!prehistoric! stormy!periods!recorded!in!lake!sediments!from!Lake!Tutira!(black!boxes).!Green!boxes! show!warm–wet!periods!(Low!Mg,!High!Sr).! ! Changes!in!the!sediment!character!of!cores!taken!from!Lake!Tutira!can!be!interpreted!to! represent! changing! climatic! conditions! such! as! the! occurrence! of! major! storms! and! droughts!(Page!et!al.,!2010).!These!events!recorded!in!the!sedimentary!layers!will!only! capture!or!record!paleoNstorms!that!were!associated!with!extreme!rainfall!events.!Such! storm!events!would!be!needed!to!have!large!amounts!of!precipitation!in!order!to!wash! and!erode!detritus!material!into!the!lake!from!the!surrounding!hills,!and!thus!not!all! storms!(in!terms!of!windiness)!are!likely!to!be!recorded.!Page!et!al.!(2010)!identified!0– 120!AD,!470–550!AD!and!680–830!AD!as!periods!of!major!storms.!These!time!periods! described!by!Page!et!al.!(2010)!correspond!to!a!decreasing!Mg!peak!between!0–120!AD,! after!a!low!Mg!trough!for!470–550!AD!and!at!a!trough!in!Mg!between!680–830!AD.!The! low! Mg! concentrations! in! the! Wairoa! speleothem! are! located! around! these! stormy! events,!however!the!storm!periods!vary!somewhere!around!the!low!Mg!concentrations! either! due! to! a! lag! in! time! from! the! event! or! because! the! storms! were! perhaps! not! always!large!enough!to!cause!detritus!material!to!be!eroded!from!near!by!hills.!Page!et! al.!(2010)’s!findings!as!well!as!low!Mg!concentrations!are!consistent!with!a!warm–wet! climate!between!60–140!AD,!470–500!AD!and!680–770!AD!(Figure!27).!! !
  • 45.
    ! 37! ! 4.3!Paleoclimate!inferences!from!Na/Ca!values!in!speleothems! As!described!in!section!4.1,!cave!depth!and!hydrology!provide!a!firstNorder!control!on! the!speleothem!Mg!concentration!and,!as!such,!the!effects!of!this!have!been!normalised! out!by!normalising!Na!to!Mg!concentrations.!! ! Using! this!approach,! it! is! evident! that! the! Wairoa! speleothem! has! higher! Na! concentrations! relative! to! the! Waitomo! speleothem.! The! Wairoa! speleothem! has! an! average!Na/Mg!ratio!of!1.1!x!10–1!and!the!Waitomo!speleothem!has!an!average!Na/Mg! ratio!of!5.3!x!10N2.!Intuitively,!this!might!be!expected!as!sea!salt!spray!will!be!higher!at! (nearN)! coastal! regions! (i.e.,! Wairoa)! relative! to! more! inland! regions! (i.e.,! Waitomo).! Thus,!the!different!Na/Mg!averages!for!the!two!speleothems!may!be!due!to!Wairoa!being! closer!to!the!coast!than!Waitomo!(Figure!8).!! ! A!secondNorder!observation!is!that!Wairoa!has!significantly!larger!Na/Mg!peaks!than!the! Waitomo!speleothem.!Wairoa!has!seven!significant!Na/Mg!peaks,!where!distinct!influxes! of!Na!entered!into!the!hydrological!system!and!were!ultimately!incorporated!into!the! speleothem.!The!peaks!for!Wairoa!are!observed!at!150!AD,!227!AD,!261!AD,!320!AD,!383! AD,!557!AD!and!752!AD.!In!contrast,!Waitomo!has!more!subdued!Na/Mg!peaks!that!are! less!defined!than!the!Wairoa!Na/Mg!peaks.!The!Na/Mg!peaks!for!Waitomo!are!observed! at!31!AD,!103!AD,!134!AD,!192!AD,!275!AD,!487!AD!and!714!AD.!Previous!discussion!of! variations!in!Mg/Ca!values!(section!4.1),!as!well!as!the!Na/Mg!variations!discussed!in! this! section,! illustrate! again! that! cave! depth! appears! to! control! the! sensitivity! of! the! speleothem!chemistry!to!environmental!factors.! !
  • 46.
    ! 38! ! Figure!28:!TimeNseries!of!Na/Mg!ratios!in!the!speleothems!GG5!(Waitomo;!blue)!and!DS! (Wairoa;!red).!The!timeNseries!highlights!peaks!in!Na!for!the!Wairoa!speleothem!(green! rectangles)! corresponding!to! prehistoric! stormy! periods! recorded! in! lake! sediments! from!nearby!Lake!Tutira!(grey!boxes)!and!antiNphase!correlations!for!Na!concentrations! in!the!Wairoa!and!Waitomo!speleothems!(black!dotted!lines).! ! The! grey! rectangles! mark! periods! where! major! prehistoric! storm! events! took! place.! Some!storms!may!be!associated!with!only!windy!or!wet!conditions,!whereas!others!may! be!associated!with!both!windy!and!wet!conditions.!Not!only!do!the!deposits!rely!on!the! type!of!storm!but!also!the!size!of!the!storms.!This!complexity!might!explain!why!not!all! Na!peaks!have!corresponding!storm!records!from!Lake!Tutira.!The!Na!peaks!in!Figure! 28! highlighted! in! green! do! have! correlated! stormy! periods! recorded! in! Lake! Tutira.! Thus,!the!storms!observed!in!the!records!had!both!windy!and!wet!conditions.!! ! ! ! ! ! ! !
  • 47.
    ! 39! ! Figure!29:!Mg/Ca!versus!Na/Ca!ratios!for! the!Wairoa!speleothem.!! The!R2!(0.05)!value!for!Mg/Ca!and!Na/Ca! illustrates! that!there! is! a! very! weak! correlation!between!the!two!ratios.!There! appears!to!be!a!cluster!of!values!for!Na/Ca! from!2.43!x!10N5!to!6.58!x!10N5!and!Mg/Ca! from!3.15!x!10N4!to!5.53!x!10N4.! ! ! ! ! ! ! Figure!30:!Sr/Ca!versus!Na/Ca!ratios!for! the!Wairoa!speleothem.!! The! R2! (0.03)! value! for! Sr/Ca! and! Na/Ca! illustrates! that! there! is! a! very! weak! correlation!between!the!two!ratios.!There! appears!to!be!a!cluster!of!values!for!Na/Ca! from!2.44!x!10N5!to!6.62!x!10N5!and!Sr/Ca! from!1.88!x!10N4!to!5.16!x!10N4.! ! ! ! ! ! Figure! 31:!U/Ca!versus!Na/Ca!ratios!for! the!Wairoa!speleothem.! The! R2! (0.2)! value! for! U/Ca! and! Na/Ca! illustrates!that!there!is!statistically!a!weak! correlation!between!the!two!ratios.!There! appears!to!be!a!cluster!of!values!for!Na/Ca! from!2.38!x!10N5!to!7.62!x!10N5!and!U/Ca! from!2.09!x!10N7!to!8.66!x!10N7.! ! ! ! Mg/Ca! ! 0.00E+00! 1.00EN04! 2.00EN04! 3.00EN04! 4.00EN04! 5.00EN04! 6.00EN04! Wairoa! 0.00E+00! 2.00EN04! 4.00EN04! 6.00EN04! 8.00EN04! 1.00EN03! 1.20EN03! Wairoa! 0.00E+00! 2.00EN07! 4.00EN07! 6.00EN07! 8.00EN07! 1.00EN06! 1.20EN06! Wairoa! Sr/Ca! ! U/Ca! ! Na/Ca! !
  • 48.
    ! 40! The!data!plotted!in!Figures!28–30!all!show!considerable!variations!in!Mg,!Sr!and!U,!but! these! are!only! weakly! (U)! or! not! correlated! at! all! with! Na! concentrations,! which! randomly!extend!to!high!values.!These!points!are!controlling!and!lowering!the!R2!values! in!these!plots.!The!clusters!can!be!interpreted!as!the!normal!climatic!conditions!and!the! points!that!deviate!away!from!the!trend!are!the!events!(i.e.,!storms)!that!are!anomalous! and!deliver!Na!to!the!land!surface!and!cave!hydrological!systems.!! ! Where!Na/Ca!is!high!(>2.4!x!10N5),!Mg/Ca!varies!from!3.5!x!10N4!to!1.0!x!10N3!and!Sr/Ca! varies!from!1.7!x!10N4!to!4.0!x!10N4.!The!(generally)!high!Mg/Ca!and!low!Sr/Ca!values! when! anomalous! Na! peaks! occur! are! diagnostic! of! warm–wet! conditions.! Warm–wet! conditions! are! historically! associated! with! stormy! periods! as! it! forces! surface! air! pressures!to!drop,!creating!extreme!air!pressure!differences!and!thus!windy!and!wet! conditions.! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
  • 49.
  • 50.
    ! 42! ! El!Niño!and!La!Niña!cycles!significantly!influence!wind!direction!and!climate!patterns!in! New!Zealand.!Historic!records!for!El!Niño!and!La!Niña!events!only!extend!back!to!the! late! 1970s/early!1880s! and! show! that! the! El! Niño! and! La! Niña! occurs! on! a! frequent! basis!between!every!ca.!5–15!yr!(Folland,!2002).!Figure!32!highlights!smaller!Na!peaks! to! occur! on! average! every! ca.! 10–20! yr,! with! larger! peaks! occurring! with! infrequent! intervals! of! 75,! 35,! 65,! 55,! 170! and! 200! yr.! The! frequency! of! the! smaller! Na! peaks! corresponds!with!the!frequency!of!the!El!Niño–!La!Niña!cycle.!As!historical!records!for!El! Niño!do!not!extend!back!to!the!period!between!0–800!AD,!a!plausible!explanation!for!the! larger!Na!peaks!is!extreme!El!Niño!events!or!nonNEl!Niño!tropical!storms.! La! Niña! events! lower! seaNsurface! temperatures! in! the! Pacific! Ocean! and! thus! New! Zealand!experiences!cooler!temperatures!during!a!La!Niña!on!the!west!coast!(NIWA);! retrieved! 13! August! 2015).! The! El! Niño! cycle! raises! seaNsurface! temperatures! in! the! Pacific! and! thus! New! Zealand! experiences! a! warmer! and! wetter! climate! on! the! west! coast.!During!a!La!Niña,!the!east!coast!experiences!northNeasterly!winds,!while!during!an! El!Niño!the!west!coast!experiences!southNwesterly!winds.!Due!to!the!dominating!wind! patterns!as!a!result!of!the!El!Niño!and!La!Niña!events,!it!is!observed!that!during!a!La! Niña! event,! the! Wairoa! speleothem! has! Na! peaks,! while! during! an! El! Niño! event,! Waitomo! has! Na! peaks.! This! is! seen! in! ! ! ! Figure! 28! where! the! small! scale! cyclicity! between!Wairoa!and!Waitomo!Na!concentrations!are!antiNphased!(dotted!black!lines!in! Figure! 28).! These! antiNphased! periods! are! seen! where:! Wairoa! has! increased! Na! concentrations!and!Waitomo!have!decreased!Na!concentrations!(20!AD,!84!AD,!170!AD,! 227!AD,!305!AD,!764!AD)!and!Wairoa!has!decreased!Na!concentrations!and!Waitomo! have!increased!Na!concentrations!(97!AD,!115!AD).! ! ! ! ! ! ! ! ! !
  • 51.
    ! 43! ! ! Figure!33:!TimeNseries!of!Mg/Ca!(purple)!and!Na/Mg!(green)!ratios!for!the!Wairoa! speleothem.!.!The!timeNseries!highlights!corresponding!Mg!peaks!and!troughs!for!peaks! in!Na.!The!correlations!between!Mg!and!Na!infer!climatic!conditions.! ! Figure! 33!compares! Mg! and! Na! concentrations! for! the! Wairoa! speleothem! to! infer! correlations!of!wet!periods!from!the!low!Mg!values!with!that!of!high!Na!values.!At!~80! AD,!~180!AD,!~320!AD,!~580!AD,!~610!AD,!~680!AD!there!are!small!peaks!in!Na!and! low!Mg!values.!These!periods!can!be!justified!as!little!storm!events!that!had!wet!and! relatively!little!wind.!At!~150!AD,!~220!AD,!~260!AD,!~390!AD!there!are!peaks!in!both! Na!and!Mg!values.!These!periods!can!be!thought!as!wind!events!with!no!rain.!At!~550! AD!and!~750!AD!there!are!massive!Na!peaks!with!low!Mg!values.!These!periods!are! thought!to!be!larger!storm!events,!which!were!both!rain!and!wind!events.!!
  • 52.
    ! ! 44! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Chapter!5!! ! 5.0$Conclusions$ $ A!trace!element!study!of!two!speleothems!from!the!Waitomo!and!Wairoa!regions!of!the! North!Island!of!New!Zealand!has!shown!that:! ! 1. The!Waitomo!speleothem!has!significantly!higher!Mg!concentrations!compared! with!that!of!the!Wairoa!speleothem,!and!that!the!different!average!Mg/Ca!ratios! for!the!two!speleothems!are!likely!to!be!primarily!due!to!cave!depth!at!each!site! rather!than!regional!climate!variations.!! 2.Mg/Ca!ratios!in!the!Wairoa!speleothem!show!clear!cyclical!variations!with! distinct!peaks,!which!are!most!likely!in!response!to!climate!variations.!The! Wairoa!speleothem!appears!to!be!a!more!sensitive!archive!that!better!records! climatic!change!relative!to!the!Waitomo!speleothem.! 3. A!previously!studied!speleothem!from!northwest!Nelson!(reference)!shows! changes!in!trace!element!chemistry!during!glacial!and!interglacial!periods.! Similar!sized!changes!are!observed!for!Mg!during!the!period!0–800!AD!in!both! the!Waitomo!and!the!Wairoa!speleothems,!but!not!for!Sr.!These!Mg/Ca!changes! support!the!conclusion!that!Mg!in!speleothems!is!partly!related!to!cave!depth.! The!cave!depth!also!alters!the!sensitivity!of!the!trace!element!chemistry!in!the! speleothems!to!changing!environmental!conditions.!The!deeper!the!cave,!the!less! sensitive!the!trace!element!chemistry!of!the!speleothems!is!to!changes!in! environmental!parameters.!!! 4. There!is!a!distinct!Na!difference!between!the!two!speleothems.!The!Wairoa! speleothem!has!higher!Na!concentrations!than!the!Watomo!speleothem.!This!is! due!to!Wairoa!being!a!more!(nearP)!coastal!region!than!that!of!Waitomo,!which!is! relatively!inland!as!compared!with!the!Wairoa!site.!! 5. Spikes!in!Na!concentrations!relate!to!either!windy!storm!events,!rainy!storm! events!or!both!wind!and!storm!events.!Rainy!storm!events!occur!when!Mg! concentrations!are!relatively!low!and!Na!concentrations!are!relatively!high.! Windy!storm!events!occur!when!Na!and!Mg!concentrations!are!relatively!high.!
  • 53.
  • 54.
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