G. Della Porta (2015) - Non marine carbonate build-ups: comparing depositional geometry, fabric types and geochemical signature

1. Non marine carbonate build-ups: comparing depositional
geometry, fabric types and geochemical signature
Giovanna Della Porta
University of Milan, Earth Sciences Department, Milan, Italy
Project funded by BG Group, Repsol & Statoil February 2015

2. Non-marine carbonate precipitates
• Wide range of carbonate precipitated geobody types, fabrics and flow unit
architectures with complex pore systems.
• occur in different depositional settings (lakes, spring related) and water
physico-chemical properties (high T, high alkalinity and salinity,
freshwater, ambient T)
• favoured by active tectonics and volcanisms
• various types coexist in the same basin (e.g., East African Rift lakes and
hydrothermal vents)
• all unique case studies..
• but share some common features depending on the scale of observation

3. Precipitated carbonates in different depositional settings
a) Endorheic alkaline and saline
lake shorelines (algal microbial
bioherms)
b) Sub-lacustrine springs where groundwater and/or thermal water
mix with lake water in alkaline lakes (spring mounds and pinnacles)
c) Subaerial springs: freshwater
ambient temperature fluvial
systems (calcareous tufa) and
hydrothermal (> 20°C) vents
(travertine).

4. Limited studies and confused terminology
Subaerial spring related non marine carbonates
• Travertine (Pedley 1990) or Thermogene travertine (Pentecost 2005): continental
carbonates precipitated from thermal water (T >20°C) supersaturated with CaCO3
degassing CO2 while out-flowing from subaerial vents. CO2 derived from deep
seated geothermal sources. They are scarce in macrophytes and dominated by
heat tolerant microbes.
• Calcareous Tufa (Pedley, 1990) or Meteogene travertine (Pentecost 2005):
continental carbonates precipitated from ambient temperature freshwater of
fluvial-marsh origin and karstic springs, rich in microphytic and macrophytic
growths, leaves and woody tissue.
Lacustrine carbonates
• Lacustrine tufa (Pedley, 1990); meteogene travertine and lake bioherms or build-
ups (Pentecost 2005)
• Sub-lacustrine spring related saline travertines and saline tufa (Capezzuoli et al.
2014)

5. Origin of the term “travertine”
Tivoli Pleistocene travertine
quarries, 20 km East of Rome
Latin name Lapis tiburtinus
What did the Romans do for us?

6. Non marine carbonates in extreme environments
and search of extraterrestrial life

7. Non marine carbonates in extreme depositional settings and
search for oil: the South Atlantic Presalt
South Atlantic sedimentary basins
Mello et al. 2012. Geol Soc London Sp. Publ

8. Pre-Salt explored sedimentary basins
Aslanian et al. (2009) Tectonophysics

9. South Atlantic Aptian hydrocarbon reservoirs pre-evaporites
http://www.cobaltintl.com/technology-innovation

10. Aptian non-marine carbonate reservoirs:
from active rift to sag phase
Chaboureau et al. (2013) Tectonophysics

11. Aptian non-marine carbonate reservoirs:
from active rift to sag phase
Chaboureau et al. (2013) Tectonophysics

12. What is the Brasilian Pre-Salt reservoir rock?
Barra Velha Fm., Lower Cretaceous, Santos Basin, Terra et al. (2010)

13. Are these hydrothermal travertines as those in Italy?
Or did they form in a shallow, several kms wide alkaline
or saline lake?
Are these abiotic or microbially mediated carbonates?
Is there anywhere an outcrop analogue?
Is there anything equivalent at present on the Earth
surface?

14. Non marine carbonate review
v 1. Depositional setting and geometry:
§ a) lacustrine shoreline buildups: form continuous belts for kms;
§ b) sub-lacustrine groundwater/hydrothermal spring mounds : 10s m thick, isolated or in clusters, kms
apart, aligned along faults;
§ c) subaerial travertine and tufa: ms to 10s of metres, wedges, mounds, fissure ridges, barrages,
cascades; fault and climate control.
v 2. Precipitated carbonate fabric types: not diagnostic of specific depositional setting, buildup
geometry and architecture.
v 3. Porosity : wide range of up to cm-size primary porosity and microporosity linked to fabric types.
v 4. Processes: continuum between abiotic and microbially mediated precipitation
§ water supersaturation driven by physico-chemical processes
§ almost ubiquitous microbial biofilms.
v 5. Geochemistry can partly help to differentiate the precipitating fluid: hydrothermal vs. freshwater
Della Porta (2015, Geol Soc
Spec Publ)

15. Non marine carbonate selected case studies
Lacustrine shoreline buildups
• a) hypersaline Holocene Great Salt
Lake,
• b) soda lake Miocene Ries Crater,
• c) schizohaline Eocene Green River Fm.
Sublacustrine springs – thermal or
groundwater mixing with lake water -
upper Pleistocene-Holocene
• a) mildly alkaline Pyramid Lake,
• b) saline alkaline Mono Lake.
Hydrothermal travertine rift lake (Miocene,
Tuscany, Central Italy).
Subaerial flowing-water systems :
• a) freshwater fluvial systems (tufa
Lombardy, Italy),
• b) hydrothermal (38-50°C) travertine,
Tuscany, Central Italy).
200 km
200 km
Pleistocene hot-spring
travertine
Miocene rift lake with
hydrothermal water,
Tuscany, Central Italy
Miocene algal bioherms,
Ries Crater, South
Germany
Eocene schizohaline lake caddis fly
larvae stromatolite bioherms
Green River Fm., Utah &
Wyoming
Holocene hypersaline lake
microbial bioherms,
Great Salt Lake, Utah
Late Pleistocene
mildly alkaline lake,
mounds,
Pyramid Lake,
Nevada
Pleistocene-Holocene
alkaline lake pinnacles,
Mono Lake, California
Google map images http://maps.google.com/
Fluvial freshwater tufa,
Holocene, Lombardy

16. Lake shoreline bioherms, Great Salt Lake, Utah
• Hypersaline (6-27%);
• Extensional, N-S and NE-SW oriented faults ;
• Holocene aragonitic laminated and clotted peloidal microbial
bioherms at high-energy shorelines associated with ooids;
• Buildup distribution controlled by stable substrate, water depth
(0.1-5 m depth) and faults;
• Buildup shapes: m-scale, dms thick, elongated perpendicular to
shoreline or sub-circular and coalesced.
Modified after Eardley (1938), Carozzi
(1962), Colman et al. (2002)
Della Porta (2015, Geol Soc
Spec Publ)

17. Lake shoreline bioherms
Holocene Great Salt
Lake
Eocene Green River Fm.
Miocene Ries Crater
0.5 m
WE
Great Salt Lake Utah
carbonate microbial bioherms
ooidal rippled sands
1.5 m
Green River Fm. Wyoming
2 m
Ries Crater Germany
1 m
Great Salt Lake Utah
§ Mounds, lenses,
inverted cone shapes
§ Associated with coated
green algae, insect larval
cases and biofilms
§ Coated grains and
skeletal peloidal sands
§ Cluster to form
continuous belts parallel
to shorelines
Della Porta (2015, Geol Soc
Spec Publ)

18. Lake shoreline bioherms
Great Salt Lake
laminated columnar stromatolite
boundstone
Clotted peloidal
micrite boundstone
3 cm
Eocene GRF encrusted
caddisfly larvae
Laminated
stromatolitic
boundstone
1.5 m
Green River Fm. WY
1 m
Great Salt Lake Bridger Bay Holocene Great Salt
Lake
Eocene Green River Fm.
Della Porta (2015, Geol Soc
Spec Publ)

19. Sublacustrine spring pinnacles, Mono Lake, CA
• alkaline (pH = 9.7-10) saline (50-90‰)
meromictic lake;
• volcanically active extensional structural
depression;
• Upper Pleistocene-Holocene pinnacle clusters
(1-8 m high, 1.5-15 m wide),
• kms apart at groundwater springs or thermal
springs;
• Fault controlled alignment;
• calcite, aragonite , ikaite (Bischoff et al. 1993).
2 m
Modified after Newton (1994) and California Geological map
http://www.quake.ca.gov/gmaps/FAM/faultactivitymap.html
Della Porta (2015, Geol Soc
Spec Publ)

20. Sublacustrine spring pinnacles, Mono Lake, CA
Holocene-upper
Pleistocene spring
pinnacles at
groundwater /
hydrothermal mixing
with alkaline lake
water
300 m 1 cm
1 m
§ Pinnacles up to 8 m
thick; central column,
cm-dm layering
§ isolated or in clusters
§ kms spacing
§ Fault alignment
Google Earth images
Della Porta (2015, Geol Soc
Spec Publ)

21. Sublacustrine spring mounds, Pyramid Lake, NV
• freshwater to mildly alkaline (pH 9);
• extensional tectonics Basin and Range Province;
• Upper Pleistocene-Holocene mounds (dm to 10s m, up to 60-100
m)
• isolated, kms spacing, at mixing of groundwater and/or thermal
sub-lacustrine springs with lake water;
• spatial control by N-S normal and strike-slip faults acting as fluid
conduits;
• ikaite CaCO3·6H2O, calcite, aragonite
60-100 m
Needles Rocks, Pyramid Lake
Modified
after Henry
et al.
(2007)
Della Porta (2015, Geol Soc
Spec Publ)

22. Sublacustrine spring mounds, Pyramid Lake, NV
Holocene-upper
Pleistocene spring
mounds at mixing
of groundwater or
thermal spring with
lake water
2 m
1 km
§ at spring location;
isolated mounds
(1-100 m thick) or in
clusters
§ kms spacing
§ Fault alignment
Della Porta (2015, Geol Soc
Spec Publ)

23. Sublacustrine spring mounds, Pyramid Lake, NV
1
2
3
4
40 cm
dm-thick layers of dendrites, laminites and ikaite
2 Ikaite crystals
10 cm
8 cm
3 Dendritic clotted micrite
4 Laminated crystal fans
1 columnar laminated
Holocene-upper
Pleistocene spring
mounds at mixing of
groundwater or
thermal spring with
lake water
40 cm
• Columnar to
spherical shapes
• Concentric
layering , cm to
dms thick
Della Porta (2015, Geol Soc
Spec Publ)

24. Non marine carbonate selected case studies
Lacustrine shoreline buildups
• a) hypersaline Holocene Great Salt
Lake,
• b) soda lake Miocene Ries Crater,
• c) schizohaline Eocene Green River Fm.
Sublacustrine springs – thermal or
groundwater mixing with lake water -
upper Pleistocene-Holocene
• a) mildly alkaline Pyramid Lake,
• b) saline alkaline Mono Lake.
Hydrothermal travertine rift lake (Miocene,
Tuscany, Central Italy).
Subaerial flowing-water systems :
• a) freshwater fluvial systems (tufa
Lombardy, Italy),
• b) hydrothermal (38-50°C) travertine,
Tuscany, Central Italy).
200 km
200 km
Pleistocene hot-spring
travertine
Miocene rift lake with
hydrothermal water,
Tuscany, Central Italy
Miocene algal bioherms,
Ries Crater, South
Germany
Eocene schizohaline lake caddis fly
larvae stromatolite bioherms
Green River Fm., Utah &
Wyoming
Holocene hypersaline lake
microbial bioherms,
Great Salt Lake, Utah
Late Pleistocene
mildly alkaline lake,
mounds,
Pyramid Lake,
Nevada
Pleistocene-Holocene
alkaline lake pinnacles,
Mono Lake, California
Google map images http://maps.google.com/
Fluvial freshwater tufa,
Holocene, Lombardy

25. Extensional tectonics, volcanism and hydrothermal travertines in Central Italy
Modified after Bigi et al. (1991), Minissale (2004) Carminati & Doglioni (2012)
Della Porta
(2015, Geol Soc
Spec Publ)

26. Subaerial spring related
carbonates: hydrothermal
travertines and
freshwater tufas
Della Porta (2015) Geol. Soc. SP

27. Hydrothermal travertine terraced slope geometry
§ Present-day and Pleistocene subaerial
hydrothermal travertine (T=38°) terraced
slope (Tuscany, Italy)
§ mm- to dm layering
§ fast-flowing slopes vs. stagnant pools
0
.
5
m
60 cm
W E N S
0.5 m
pisoids
pisoids
pisoids
Clotted
micrite
dendrites/
shrubs
laminated
Coated gas
bubbles
1 cm
Della Porta (2015, Geol Soc
Spec Publ)

28. Rift basin with hydrothermal travertine and alluvian fans
Miocene (Tuscany) rift
basin with
hydrothermal
travertine alternating
with detrital
siliciclastics (alluvial
plain and fans)
2 m
1 cm
Lithoclastic breccias
(alluvial fan)
Alluvial plain shales,
marls
and palustrine/
lacustrine carbonate
beds
with coated plants
Well bedded precipitated travertines
and peloidal grainstone
1 cm
§ 70 m thick wedge
shaped
§ Terraced travertine
slope
§ Palustrine coated
vegetation
Croci et
al. (2016,
Sed Geol)

29. Freshwater fluvial tufa
1 cm
§ Present-day and Pleistocene fluvial tufa
§ cm to 10s m barrages, cascades, terraced
slopes (Lombardy, North Italy)
§ Carbonate encrusted vegetation, bryophytes,
microbial biofilms (cyanobacteria)
3 m 1 m

30. Depositional setting and spatial distribution
1 Bioherms
- continuous belts
parallel to shorelines
- controlled by substrate
stability, water depth,
energy, sediment
disturbance
2 Sub-lacustrine spring
mounds
- isolated, kms apart or
aligned along faults
- controlled by fault,
hydrology, water
chemistry
3 Travertine rift
basin
- wedge shaped, well
bedded with
siliciclastic
- control by faults and
climate
1) Lake shoreline bioherms
Great Salt Lake
Green River Fm
Ries Crater
2) Sublacustrine spring mounds
Mono Lake
Pyramid Lake
3) Travertine rift basin,
Miocene, Tuscany
4) Hydrothermal travertine and freshwater
fluvial tufa
4 Hydrothermal
travertines and fluvial
tufa
- mounds, apron and
fissure ridges
- control by fault
antecedent
topography, climate
Della Porta (2015) Geol. Soc. SP

31. Classification of non marine carbonate lithotypes
Della Porta (2015) Geol. Soc. SP
Della Porta (2015, Geol Soc
Spec Publ)

32. Clotted peloidal micrite boundstone
with mm- to cm-size framework porosity and microporosity
microbially mediated texture analogous to marine microbialites
Pleistocene travertine Central Italy
Miocene Ries Crater bioherms
Miocene travertine rift lake Tuscany Pleistocene river tufa Tuscany
Great Salt Lake coatings on boulders Pyramid Lake spring mound
1 mm 2 mm
1.2 mm 1.5 mm

33. Microporosity in micrite/microsparite precipitates
associated with microbial biofilms
Eocene Green River Fm. Calcite micrite and
dolomite
Pyramid Lake spring mound clotted micrite
and diatoms
Miocene Ries Crater clotted micrite and
dolomite
Present-day hydrothermal travertine
clotted micrite in biofilm EPS
Great Salt Lake aragonite micrite and
needles in microbial biofilm EPS
Holocene river tufa micrite, EPS and
diatoms

34. Micritic/microsparitic laminae boundstone
from tight to inter-laminae porosity
Miocene Ries Crater micritic laminae
stromatolites
Miocene rift lake Tuscany micritic
laminae alternating with peloidal
grainstone
Eocene Green River Fm. (Wy)
stromatolites
Great Salt Lake micritic laminae
stromatolites
Holocene Mono Lake laminated
boundstone
1 mm 4 mm
Pleistocene travertine micrite laminae
1 mm

35. Clotted peloidal micrite dendrite boundstone
with mm- to cm- size inter-dendrite porosity
Hydrothermal travertine shrubs
(cf. Chafetz and Folk 1984)
Mono Lake pinnacle Mn-Fe dendrite
Mono Lake spring pinnacles micrite
coated branching filaments
Pyramid Lake spring mound clotted
micrite dendrites
River tufa coated cyanobacteria filaments
1 cm 2 mm
Pyramid lake spring mound clotted
micrite dendrites
dendritic
laminated

36. Pleistocene hydrothermal travertine
(feather dendrites)
Crystalline dendrite cementstone
with cm- to mm-size inter-dendrite porosity
(lack in lacustrine shoreline bioherms)
Pleistocene hydrothermal travertine
(feather dendrites)
Miocene travertine rift lake Tuscany
Pleistocene hydrothermal travertine
(feather dendrites)
Pyramid spring mound calcite pseudomorphs
after ikaite
Mono Lake spring pinnacle crystalline
dendrites
8 cm
3.5 mm

37. Crystalline fan cementstone
from tight crystalline crusts to inter-fan porosity
Eocene Green River Fm. (Wy) crystal
fan stromatolites
Pyramid Lake spring mound crystal
fan crusts
River tufa crystal fan alternating with
micrite crusts
3.5 mm
Pleistocene travertine smooth slope
1 mm
Miocene travertine rift lake Tuscany
Mono Lake spring pinnacles crystal
fans

38. What fabrics are diagnostic of a specific depositional setting and
spatial distribution?
• None…
• similar fabrics in different depositional settings with different spatial distribution.
• Clotted peloidal micrite fabrics (biologically induced/influenced) in all studied examples and
similar to marine microbialites.
• Crystalline dendrites and fans mostly present in hydrothermal travertine, sublacustrine spring
mounds and fluvial tufa where supersaturation is from physico-chemical processes
(evaporation, cooling, CO2 degassing, water mixing).
• Better understanding by combining fabric associations + buildup architecture:
• a) spring mounds: columnar and spherical structures with cm-dm concentric layering with
crystalline, clotted peloidal and laminated fabrics;
• b) hydrothermal travertines: evidence of water flow (terraced systems) and steep slopes.

39. Mm- to cm-scale analysis is not a reliable proxy for geometry
Great Salt Lake bioherms Mono Lake spring pinnacles
Della Porta
(2015, Geol Soc
Spec Publ)

40. Fabric association and architecture in spring mounds:
aggregated m-scale spheres with cm-thick concentric layers
Della Porta (2015) Geol. Soc. SP
Della Porta
(2015, Geol
Soc Spec
Publ)

41. Hydrothermal travertine: terraced geometry with cm-thick layering
Fast-flowing vs. slow-flowing fabric associations
Fast-flowing, steeply
dipping slopes and rims
(CO2 degassing):
Crystalline dendrites and
fans.
Slow-flowing, horizontal
pools and ponds:
Clotted peloidal micrite
dendrites, coated
bubbles, rafts, pisoids.
2 cm
10 cm
1 cm

42. Precipitation processes:
what is the role played by ubiquitous microbial biofilms?
Great
Salt Lake
Precipitation
below
biofilms
Surpassed
EPS
inhibition
during
degradation
Hydrothermal
travertines
Coated gas
bubbles from
microbial
metabolism
Pyramid
Lake
Ground
water
spring
1 cm
10 cm
3 cm 5 cm
Coated
filament
streamers
+
Uncalcified
biofilms

43. Crystal precipitation within/around biofilms
Pleistocene river tufa trigonal calcite
surrounded by organic biofilm
Great Salt Lake clotted peloidal micrite in
microbial EPS
Great Salt Lake micrite precipitates surrounded
by filaments and sub-micron size spheres
Pyramid Lake micrite with EPS and micron size
coccoid structures
Mono Lake micrite clots associated with
microbial EPS
Present-day travertine calcite and aragonite
associated with EPS

44. Microbial evidence also in crystalline fans and dendrites
Miocene travertine rift lake Tuscany
with branching filamentous structures
1 cm
Present-day river tufa crystal fan with
coated cyanobacteria? filaments
Pyramid lake tubular structures in
clotted micrite and microsparite
River tufa encrusted cyanobacteria?
filaments
Pyramid lake crystal fans with
encrusted filaments
Holocene Mono Lake with coated
filaments

45. Processes: abiotic vs. biologically mediated precipitation
Pyramid lake gastropod grainstone
Great Salt Lake, aragonite fibrous
cement
Great Salt Lake trapped ooids
Great Salt Lake, clotted peloidal micrite
Great Salt Lake, carbonate nano-spheres
and acicular aragonite in EPS

46. Processes: abiotic vs. biologically mediated precipitation
Pyramid lake clotted micrite dendrites
7 mm
Physico-chemical precipitation with
microbes and biofilms acting as low-
energy sites for mineral nucleation
Hydrothermal travertine clotted peloidal
dendrite (shrubs)
Pyramid Lake laminated crystal fans
Hydrothermal travertine (crystalline
dendrites in fast flowing slopes)
Present-day river tufa crystal fan
embedding filamentous structures River tufa coated filaments

47. Non marine
carbonate stable
isotopes
Della Porta (2015, Geol Soc
Spec Publ)

48. Non marine carbonate stable isotope signature
§ Fluvial calcareous tufa:
light δ13C and δ18O of
meteoric freshwater
§ Hydrothermal travertine:
light δ18O due to high T,
heavy δ13C DIC from
magmatic sources,
carbonate substrate rocks
and CO2 degassing
§ Closed lakes: positive
covariance of δ13C and δ18O
(cf. Talbot 1990)
§ Evaporative systems: heavy
δ18O, δ13C in equilibrium
with atmospheric CO2 in
long residence time
Della Porta (2015) Geol. Soc. SP

49. Non marine carbonate stable isotope signature
No clear evidence of fractionation related to microbial processes
Della Porta (2015, Geol Soc
Spec Publ)

50. Conclusions
§ 1. Geometry:
a) lake shoreline microbial algal bioherms: continuous belts parallel to shorelines for kms;
b) sub-lacustrine groundwater/hot springs: isolated mounds and pinnacles, kms apart, continuous along faults;
c) travertine and tufa: wedges, mounds, linear isolated structures.
§ Different buildup types can occur in the same basin
§ Spatial distribution controlled by substrate stability, water depth, spring location, faults, antecedent topography.
§ 2. Fabric types: lack of fabric types clearly diagnostic of specific settings and relative geometry.
Clotted peloidal micrite typical of marine to non marine microbialites.
Crystalline fans and dendrites predominate in hydrothermal in travertine, lake spring mounds and river tufa.
Fabric types associations must be combined with buildup architecture (e.g., columnar and spherical cm-scale
concentric structures in spring mounds; cm-scale layering and terraced morphology in hydrothermal travertines).
§ 3. Porosity: wide range of primary porosity linked to fabric types with mm- to cm- pores associated with
microporosity.
§ 4. A continuum between abiotic and biologically influenced and induced precipitation:
Ø Supersaturation driven by phisico-chemical mechanisms
Ø microbial biofilms ubiquitous in such extreme environments , acting as passive substrate for crystal nucleation.
§ 5. Geochemical signature allows distinguishing fluvial tufa and hydrothermal travertines; lakes show the linear
correlation of closed systems (Talbot 1990). Isotopes do not indicate fractionation related to microbial metabolism.

51. ,
Enrico Capezzuoli (Siena University)
Paiute Tribe, Pyramid Lake
California State Park, Mono Lake
Saturnia Travertine Quarry
Many thanks to:
the project sponsors BG Group, Repsol & Statoil

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