Sedimentary RocksSedimentary Rocks
and Environmentsand Environments
Chapters 4 and 5Chapters 4 and 5
Proportions ofProportions of
Rock Types on the EarthRock Types on the Earth
Sedimentary rocks cover about 75% of the world...
What Can Sedimentary Rocks Tell Us?What Can Sedimentary Rocks Tell Us?
• Paleoclimate ConditionsPaleoclimate Conditions
• ...
The Rock CycleThe Rock Cycle
• SedimentarySedimentary
Rocks areRocks are
formed fromformed from
sediments.sediments.
Sedimentary RocksSedimentary Rocks
• Composed ofComposed of sedimentsediment = loose particulate= loose particulate
materi...
Turning Sediment into RockTurning Sediment into Rock
• DiagenesisDiagenesis – all of the chemical,– all of the chemical,
p...
Turning Sediment into RockTurning Sediment into Rock
• Diagenesis Includes:Diagenesis Includes:
• RecrystallizationRecryst...
Turning Sediment into RockTurning Sediment into Rock
• Diagenesis IncludesDiagenesis Includes
• CompactionCompaction::
– S...
Diagenesis: LithificationDiagenesis: Lithification
SedimentSediment
RockRock
Compaction and LithificationCompaction and Lithification
Turning Sediment into RockTurning Sediment into Rock
• Diagenesis IncludesDiagenesis Includes
• CementationCementation::
–...
Diagenesis: LithificationDiagenesis: Lithification
SedimentSediment
RockRock
CementationCementation
Typical CementsTypical Cements::
• CalciteCalcite
• QuartzQuartz
• Iron OxideIron Oxide
Types of Sedimentary RocksTypes of Sedimentary Rocks
• Rock types are based on theRock types are based on the sourcesource...
Classification of Sedimentary RocksClassification of Sedimentary Rocks
• Sedimentary rocks are classified based onSediment...
• Two majorTwo major texturestextures are used in theare used in the
classification of sedimentary rocks.classification of...
Types of Sedimentary RocksTypes of Sedimentary Rocks
• DetritalDetrital Sedimentary RocksSedimentary Rocks
– Conglomerate ...
Identification of Sedimentary RocksIdentification of Sedimentary Rocks
STOP
Characteristics of DetritalCharacteristics of Detrital
Sedimentary RocksSedimentary Rocks
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• Detrial rocks have aDetrial rocks have a clasticclastic (broken or(...
Clast SupportedClast Supported
ConglomerateConglomerate
(River Deposits)(River Deposits)
Matrix Supported ConglomerateMatrix Supported Conglomerate
(Glacial/Landslide Deposits)(Glacial/Landslide Deposits)
““Mode...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
are Classified by Grain Sizeare Classified by Grain Size
Particle siz...
Grain SizeGrain Size
• Gravel ≥ 2 mmGravel ≥ 2 mm
• Sand – 2 mm to 1/16 mmSand – 2 mm to 1/16 mm
• Silt – 1/16 mm to 1/256...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
are Classified by Grain Sizeare Classified by Grain Size
Grain Size R...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
ShaleShale SandstoneSandstone
ConglomerateConglomerate BrecciaBreccia
What Does Grain Size Tell Us?What Does Grain Size Tell Us?
• The energy of the environment andThe energy of the environmen...
Grain Size InterpretationGrain Size Interpretation
• GravelGravel
• SandSand
• SiltSilt
• ClayClay
• River, BeachRiver, Be...
SortingSorting
• SortingSorting refers to the distribution ofrefers to the distribution of
grain sizes in a rock.grain siz...
Degrees of SortingDegrees of Sorting
What Does the Degree of Sorting TellWhat Does the Degree of Sorting Tell
Us?Us?
• The energy of the environment and media ...
What Does theWhat Does the
Degree of Sorting Tell Us?Degree of Sorting Tell Us?
• The energy of the environment andThe ene...
• Degree of sorting also indicatesDegree of sorting also indicates
distance from the sourcedistance from the source andand...
Grain ShapeGrain Shape
• Grain shapeGrain shape is described in terms ofis described in terms of roundingrounding ofof
gra...
Rounding & SphericityRounding & Sphericity
SphericalSpherical
OblongOblong
Figure 3-13 (p. 72)Figure 3-13 (p. 72)
Degree of rounding is expressed using the following scale:Degree of rounding is exp...
Gravel Sized Detrital RocksGravel Sized Detrital Rocks
(Subdivided Based on Grain Roundness)(Subdivided Based on Grain Rou...
Grain ShapeGrain Shape
• Degree of roundingDegree of rounding also indicatesalso indicates
distance from sourcedistance fr...
Interpretation:Interpretation:
Distance of TransportDistance of Transport
ShortShort FarFar STOP
Chemical WeatheringChemical Weathering
• Transport timeTransport time also affects thealso affects the
mineral composition...
Color of Sedimentary RocksColor of Sedimentary Rocks
• BlackBlack andand dark graydark gray coloration incoloration in
sed...
Color of Sedimentary RocksColor of Sedimentary Rocks
• RedRed coloration incoloration in
sedimentary rockssedimentary rock...
Color of Sedimentary RocksColor of Sedimentary Rocks
• GreenGreen andand graygray coloration incoloration in
sedimentary r...
Overview of DetritalOverview of Detrital
Sedimentary Rock TypesSedimentary Rock Types
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• Common Detrital Sedimentary RocksCommon Detrital Sedimentary Rocks
...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• MudstoneMudstone
• Composed ofComposed of mudmud – a mixture of sil...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• SiltstoneSiltstone
– Composed ofComposed of
largely oflargely of si...
Formation of Shales to SiltstonesFormation of Shales to Siltstones
• Due to their Fine Grain Size:Due to their Fine Grain ...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• SandstoneSandstone
– Composed of sand-sized particles.Composed of s...
Major Types of SandstoneMajor Types of Sandstone
• Quartz SandstoneQuartz Sandstone – Dominated by quartz; mature– Dominat...
Figure 5-24 (p. 95)Figure 5-24 (p. 95)
Four categories of sandstone as seen in thin sectionFour categories of sandstone as...
Quartz SandstoneQuartz Sandstone
Composed ofComposed of well-sortedwell-sorted,, roundedrounded quartzquartz
grains suggestsgrains suggests long-distance t...
ArkoseArkose
ArkoseArkose
• Composed of quartz, feldspars, and micas indicates
granitic source rocks. Typically poorly sorted, angular
...
Sandstone Close-UpsSandstone Close-Ups
• Quartz Sandstone (left)Quartz Sandstone (left)
• Arkose (Sandstone with >10% feld...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• Conglomerate and BrecciaConglomerate and Breccia
– Both are compose...
Detrital Sedimentary RocksDetrital Sedimentary Rocks
• Conglomerate and BrecciaConglomerate and Breccia
– Conglomerate con...
Conglomerate Deposits alongConglomerate Deposits along
the Coast of Washingtonthe Coast of Washington
Outcrop of ConglomerateOutcrop of Conglomerate
Composition of variable materials,Composition of variable materials, poorly...
Interbedded Sandstone andInterbedded Sandstone and
ConglomerateConglomerate
InterbeddedInterbedded
Sandstone andSandstone and
ConglomerateConglomerate
Suggests distinctiveSuggests distinctive
period...
BrecciaBreccia
BrecciaBreccia
Composition of variable materials,Composition of variable materials, poorly sortedpoorly sorted,,
andand an...
Chemical/BiochemicalChemical/Biochemical
Sedimentary RocksSedimentary Rocks
Chemical Sedimentary RocksChemical Sedimentary Rocks
• Consist of precipitated material thatConsist of precipitated materi...
Types of Chemical/BiochemicalTypes of Chemical/Biochemical
Sedimentary RocksSedimentary Rocks
1.1. Carbonate RocksCarbonat...
Carbonate RocksCarbonate Rocks
1.1. LimestonesLimestones
– Most abundant chemical rock.Most abundant chemical rock.
– Comp...
Formation of LimestonesFormation of Limestones
• Most limestones are theMost limestones are the direct or indirectdirect o...
Formation of LimestonesFormation of Limestones
• Most limestones are theMost limestones are the direct or indirectdirect o...
Characteristics of the EnvironmentCharacteristics of the Environment
of Marine Carbonate Formationof Marine Carbonate Form...
Organic Chemical Sedimentary RocksOrganic Chemical Sedimentary Rocks
• Fossiliferous LimestonesFossiliferous Limestones
– ...
ModernModern
CoralCoral
Reef atReef at
BoraBora
Bora inBora in
FrenchFrench
PolynesiaPolynesia
El CapitanEl Capitan
Peak inPeak in
GuadalupeGuadalupe
NationalNational
Park, Texas -Park, Texas -
ExposedExposed
Permian-...
• Micritic LimestonesMicritic Limestones
• Microcrystalline limestonesMicrocrystalline limestones composed of clay-compose...
• ChalkChalk
– ChalkChalk is a soft, porous rockis a soft, porous rock
composed of almost entirely of thecomposed of almos...
CoccolithophoridCoccolithophorid. Shells are composed. Shells are composed
of calcium carbonate. Image magnifiedof calcium...
Origin of Carbonate SedimentsOrigin of Carbonate Sediments
and Rocksand Rocks
MuchMuch lime mudlime mud
forms from theform...
MicroscopicMicroscopic
Hard PartsHard Parts
(Skeletons) of(Skeletons) of
RadiolariansRadiolarians
andand
ForaminiferaForam...
• CoquinaCoquina
– CoquinaCoquina is a coarse-grained rockis a coarse-grained rock
composed of poorly-cementedcomposed of ...
• Crystalline LimestoneCrystalline Limestone
– Crystalline limestone usually forms when theCrystalline limestone usually f...
• Oolitic LimestoneOolitic Limestone
– Oolitic limestoneOolitic limestone is composed of smallis composed of small
spheric...
Origin of Ooids inOrigin of Ooids in
Oolitic LimestonesOolitic Limestones
• OoidsOoids are tiny spheresare tiny spheres
co...
• TravertineTravertine
– TravertineTravertine forms informs in cavescaves (stalagtites,(stalagtites,
stalagmites, curtains...
Carbonates: DolomiteCarbonates: Dolomite
• Composed of dolomiteComposed of dolomite
CaMg(CaCOCaMg(CaCO33))22 – a– a calciu...
Siliceous Sedimentary RocksSiliceous Sedimentary Rocks
• ChertChert
– Made of microcrystalline quartz (silica).Made of mic...
• ChertChert
– ChertChert has various modes of origin:has various modes of origin:
• InorganicInorganic – Precipitated fro...
Modern Marine DiatomsModern Marine Diatoms
Diatom shells are composed of silicaDiatom shells are composed of silica
and ha...
Siliceous Sedimentary RocksSiliceous Sedimentary Rocks
• DiatomiteDiatomite
– Made of microscopicMade of microscopic
plank...
EvaporitesEvaporites
• EvaporationEvaporation triggers deposition of chemicaltriggers deposition of chemical
precipitates....
Rock Salt (Halite)Rock Salt (Halite)
Bonneville Salt Flats, UtahBonneville Salt Flats, Utah
Layered Rock GypsumLayered Rock Gypsum
Organic Sedimentary Rocks – CoalOrganic Sedimentary Rocks – Coal
• Composed ofComposed of organic matterorganic matter suc...
SuccessiveSuccessive
Stages inStages in
CoalCoal
FormationFormation
• Stages of Coal FormationStages of Coal Formation
1.1. Plant MaterialPlant Material – Accumulations of large– Accumulatio...
• Stages of Coal FormationStages of Coal Formation
2.2. PeatPeat – A soft brown material in which– A soft brown material i...
Successive Stages in Coal FormationSuccessive Stages in Coal Formation
• Stages of Coal FormationStages of Coal Formation
4.4. BituminousBituminous – Deeper burial– Deeper burial
transforms lig...
Successive Stages in Coal FormationSuccessive Stages in Coal Formation
STOP
Sedimentary EnvironmentsSedimentary Environments
of Depositionof Deposition
Sedimentary EnvironmentsSedimentary Environments
• A geographic setting where sediment isA geographic setting where sedime...
Sedimentary EnvironmentsSedimentary Environments
• Use characteristics such asUse characteristics such as grain sizegrain ...
The Characteristics of a SedimentaryThe Characteristics of a Sedimentary
Environment Depend on:Environment Depend on:
1.1....
Depositional EnvironmentsDepositional Environments
There are three broad categories ofThere are three broad categories of
...
Marine DepositionalMarine Depositional
EnvironmentsEnvironments
• Shallow (up to about 200 meters depth)Shallow (up to abo...
MarineMarine
DepositionalDepositional
EnvironmentsEnvironments
1.1. ContinentalContinental
ShelfShelf
2.2. ContinentalCont...
Types of Sea Floor SedimentsTypes of Sea Floor Sediments
• Terrigenous SedimentTerrigenous Sediment
– Mineral grains from ...
Marine Depositional EnvironmentsMarine Depositional Environments
Location Water Depth Slope Width Features Sediments Sedim...
Transitional DepositionalTransitional Depositional
EnvironmentsEnvironments
• Environments at or near the transitionEnviro...
TransitionalTransitional
DepositionalDepositional
EnvironmentsEnvironments
1.1. DeltasDeltas
2.2. BeachesBeaches
3.3. Barr...
Transitional Depositional EnvironmentsTransitional Depositional Environments
Description Location Features Sediments Sedim...
Fan Delta Bird-Foot Delta
• Subenvironments of a Barrier Island ComplexSubenvironments of a Barrier Island Complex
Barrier Island ComplexBarrier Isl...
TheThe
OuterOuter
Banks –Banks –
BarrierBarrier
IslandIsland
ComplexComplex
Tidal FlatsTidal Flats
EstuariesEstuaries
North Carolina's Neuse River EstuaryNorth Carolina's Neuse River Estuary
Continental DepositionalContinental Depositional
EnvironmentsEnvironments
• Continental environments are thoseContinental ...
ContinentalContinental
DepositionalDepositional
EnvironmentsEnvironments
1.1. Rivers or FluvialRivers or Fluvial
Environme...
Continental DepositionalContinental Depositional
EnvironmentsEnvironments
• Fluvial – dominated by erosion andFluvial – do...
Lacustrine Environments (Lakes)Lacustrine Environments (Lakes)
• May be large or small.May be large or small.
• May be sha...
Continental DepositionalContinental Depositional
EnvironmentsEnvironments
• Glacial – dominated by erosion andGlacial – do...
Continental DepositionalContinental Depositional
EnvironmentsEnvironments
• Eolian – dominated by erosion andEolian – domi...
Sedimentary StructuresSedimentary Structures
• Sedimentary Structures:Sedimentary Structures:
– Features visible at theFeatures visible at the scale of an outcropscale...
Sedimentary StructuresSedimentary Structures
• Stratification:Stratification:
– Layering or BeddingLayering or Bedding
– T...
• Sedimentary rocks generally haveSedimentary rocks generally have beddingbedding
oror stratificationstratification
Beddin...
• Some beds show an upward gradual decreaseSome beds show an upward gradual decrease
in grain size, known asin grain size,...
Graded BeddingGraded Bedding
InterbeddedInterbedded
Sandstone andSandstone and
ConglomerateConglomerate
(Sandstone(Sandstone
exhibits gradedexhibits gr...
• Cross-bedding forms when layers come toCross-bedding forms when layers come to
restrest
– at an angle to the surfaceat a...
Cross-Bedding orCross-Bedding or
Cross-StratificationCross-Stratification
Cross-BeddingCross-BeddingInsert Animation #17 – Cross BeddingInsert Animation #17 – Cross Bedding
Cross-Bedding orCross-B...
• Tabular cross-Tabular cross-
beddingbedding formsforms
by deposition onby deposition on
sand wavessand waves
Tabular Cro...
Tabular Cross-BeddingTabular Cross-Bedding
Trough Cross-Trough Cross-
BeddingBedding
• Trough cross-Trough cross-
beddingbedding formed byformed by
migrating dunesmi...
• Small-scale alternating ridges and troughsSmall-scale alternating ridges and troughs
– known asknown as ripple marksripp...
• Ripples with anRipples with an
asymmetricalasymmetrical
shapeshape
• In the close-up ofIn the close-up of
one ripple,one...
Current Ripple MarksCurrent Ripple Marks
• As the wavesAs the waves
wash backwash back
and forth,and forth,
– symmetricalsymmetrical
ripples formripples form
• The...
• When clay-rich sediments dry, they shrinkWhen clay-rich sediments dry, they shrink
– and crack into polygonal patternsan...
• Mud cracksMud cracks
typically fill intypically fill in
– with sedimentwith sediment
– when they arewhen they are
preser...
Mud CracksMud Cracks
A polygonal pattern of cracks producedA polygonal pattern of cracks produced
on the surface of mud as...
• Biogenic Sedimentary StructuresBiogenic Sedimentary Structures
include:include:
– TracksTracks
– BurrowsBurrows
– Trails...
• U-shaped BurrowsU-shaped Burrows
BioturbationBioturbation
• Vertical BurrowsVertical Burrows
BioturbationBioturbation
• Vertical, dark-colored areas in this rock areVertical, dark-colored areas in this rock are
sedi...
Determining “Up Direction"Determining “Up Direction"
• Because the rocks can be overturned by tectonic forces,Because the ...
Figure 5-23 (p. 94)Figure 5-23 (p. 94)
Various kinds of geopetal indicatorsVarious kinds of geopetal indicators
Fossils: Evidence of Past LifeFossils: Evidence of Past Life
• By definition, fossils are the traces orBy definition, foss...
• Geologically fossils are important forGeologically fossils are important for
many reasons:many reasons:
Fossils: Evidenc...
Sedimentary FaciesSedimentary Facies
• AA sedimentary faciessedimentary facies is a body ofis a body of
sedimentsediment
– withwith distinctivedistinctive
– ph...
Figure 5-33 (p. 101)Figure 5-33 (p. 101)
Sedimentary facies (lithofacies) developed in the seaSedimentary facies (lithofac...
Virtually all lithostratigraphic units are "Virtually all lithostratigraphic units are "timetime
transgressivetransgressiv...
Facies and Sea Level ChangesFacies and Sea Level Changes
• AA marine transgressionmarine transgression occurs when seaoccu...
Facies and Sea Level ChangesFacies and Sea Level Changes
• A transgression produces aA transgression produces a fining-fin...
• The rocks of each facies becomeThe rocks of each facies become youngeryounger
– in a landward directionin a landward dir...
Sedimentation During a TransgressionSedimentation During a Transgression
Produces an Onlap SequenceProduces an Onlap Seque...
• ThreeThree
formationsformations
depositeddeposited
– in ain a
widespreadwidespread
marinemarine
transgressiontransgressi...
Causes of TransgressionsCauses of Transgressions
1.1. MeltingMelting of polar ice caps.of polar ice caps.
2.2. Displacemen...
RegressionsRegressions
• AA marine regressionmarine regression occurs when sea leveloccurs when sea level
rises with respe...
• A marineA marine
regressionregression
– is the opposite of ais the opposite of a
marinemarine
transgressiontransgression...
Sedimentation During a RegressionSedimentation During a Regression
Produces an Offlap SequenceProduces an Offlap Sequence
Causes of RegressionsCauses of Regressions
1.1. Buildup of ice in theBuildup of ice in the polar ice capspolar ice caps..
...
Sea Level ChangesSea Level Changes
• Worldwide sea level change is known asWorldwide sea level change is known as eustatic...
Isostatic ReboundIsostatic Rebound
The Vail sea-levelThe Vail sea-level
curve of majorcurve of major
cycles of sea-levelcycles of sea-level
changes.changes.
...
Figure 5-37 (p. 103)Figure 5-37 (p. 103)
A rise in sea level will affect a far greater areaA rise in sea level will affect...
The ContinentalThe Continental
Shelf andShelf and
Coastal PlainCoastal Plain
Areas will beAreas will be
Most AffectedMost ...
What if the ice on Earth melted?What if the ice on Earth melted?
Recent Sea Level CurveRecent Sea Level Curve
Rock UnitsRock Units
Lithostratigraphic UnitLithostratigraphic Unit
• A body of sedimentary, extrusive igneous,A body of sedimentary, extrusive...
Lithostratigraphic UnitsLithostratigraphic Units
• GroupGroup – composed– composed
of 2 or more relatedof 2 or more relate...
• Lithologically homogeneousLithologically homogeneous – all beds are– all beds are
the same rock type or a distinctive se...
CorrelationCorrelation
• Correlation of rock units from one areaCorrelation of rock units from one area
to another is know...
Figure 5-44 (p. 108)Figure 5-44 (p. 108)
Correlation of lowerCorrelation of lower
Cambrian rock units inCambrian rock unit...
Figure 5-38 (p. 105)Figure 5-38 (p. 105)
If the lithology of a rock is not sufficiently distinctive to permit itsIf the li...
Geologic MapsGeologic Maps
Depicting the PastDepicting the Past
Various ways in which the distribution ofVarious ways in which the distribution of
ro...
Geologic ColumnsGeologic Columns
• Geologic ColumnsGeologic Columns
show the verticalshow the vertical
succession of rocks...
GeneralizedGeneralized
GeologicGeologic
Column forColumn for
Grand CanyonGrand Canyon
National ParkNational Park..
((From ...
Stratigraphic Cross-SectionsStratigraphic Cross-Sections
• StratigraphicStratigraphic
Cross-SectionsCross-Sections
correla...
Structural Cross-SectionsStructural Cross-Sections
• Structural Cross-SectionsStructural Cross-Sections show a slice throu...
GeologicGeologic
MapsMaps
• Geologic MapsGeologic Maps showshow
the distribution ofthe distribution of
various layers andv...
Figure 5-46 (p. 109)Figure 5-46 (p. 109)
Steps in the preparation of a geologic map.Steps in the preparation of a geologic...
Paleogeographic MapsPaleogeographic Maps
• PaleogeographicPaleogeographic
MapsMaps areare
interpretive mapsinterpretive ma...
PaleogeographicPaleogeographic
MapsMaps
• Figure 5-48 (p. 110)
• Constructing a Paleogeographic Map:
(1) For the selected ...
Isopach MapsIsopach Maps
• Isopach MapsIsopach Maps show the thickness ofshow the thickness of
formations or other units i...
Figure 5-49 (p.111)Figure 5-49 (p.111)
Isopach map ofIsopach map of
Upper OrdovicianUpper Ordovician
formations informatio...
Lithofacies MapsLithofacies Maps
• Lithofacies MapsLithofacies Maps show the distribution of lithofaciesshow the distribut...
Figure 5-52 (p. 112)Figure 5-52 (p. 112)
Lithofacies map of Lower Silurian rocks in the easternLithofacies map of Lower Si...
Ch07 sedimentary rocks
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Ch07 sedimentary rocks

  1. 1. Sedimentary RocksSedimentary Rocks and Environmentsand Environments Chapters 4 and 5Chapters 4 and 5
  2. 2. Proportions ofProportions of Rock Types on the EarthRock Types on the Earth Sedimentary rocks cover about 75% of the world's land areaSedimentary rocks cover about 75% of the world's land area
  3. 3. What Can Sedimentary Rocks Tell Us?What Can Sedimentary Rocks Tell Us? • Paleoclimate ConditionsPaleoclimate Conditions • Paleoenvironment – Arid and Tropical Belts (presence ofPaleoenvironment – Arid and Tropical Belts (presence of seas, deltas, beaches, rivers, lakes, glaciers, coral reefs,seas, deltas, beaches, rivers, lakes, glaciers, coral reefs, swamps, mountains, deserts, etc.)swamps, mountains, deserts, etc.) • Source MaterialSource Material • History of Transport and DepositionHistory of Transport and Deposition • ReliefRelief • Latitude – Climate BeltsLatitude – Climate Belts • Climate / TemperatureClimate / Temperature • Sea LevelSea Level • Changes in Atmospheric ChemistryChanges in Atmospheric Chemistry • Plate MovementsPlate Movements • Tectonic Setting – Evolution of EarthTectonic Setting – Evolution of Earth • Fossils – Evolution of OrganismsFossils – Evolution of Organisms • Relative and Absolute Age DatingRelative and Absolute Age Dating
  4. 4. The Rock CycleThe Rock Cycle • SedimentarySedimentary Rocks areRocks are formed fromformed from sediments.sediments.
  5. 5. Sedimentary RocksSedimentary Rocks • Composed ofComposed of sedimentsediment = loose particulate= loose particulate material –material – ChemicalChemical andand PhysicalPhysical – clayclay,, siltsilt,, sandsand,, gravelgravel, etc., etc. • Sediment derivation by weatheringSediment derivation by weathering – ChemicalChemical ((decompositiondecomposition)) – PhysicalPhysical ((disintegrationdisintegration)) • Sediment becomes sedimentary rockSediment becomes sedimentary rock throughthrough diagenesisdiagenesis, which involves:, which involves: – LithificationLithification • CompactionCompaction • CementationCementation – RecrystallizationRecrystallization (of carbonate sediment)(of carbonate sediment)
  6. 6. Turning Sediment into RockTurning Sediment into Rock • DiagenesisDiagenesis – all of the chemical,– all of the chemical, physical, and biological changes thatphysical, and biological changes that take place after sediments aretake place after sediments are deposited.deposited. • Occurs within the upper fewOccurs within the upper few kilometers of Earth’s crust atkilometers of Earth’s crust at temperatures generally less than 150temperatures generally less than 150 toto 200 ºC200 ºC (metamorphism occurs(metamorphism occurs beyond this threshold).beyond this threshold).
  7. 7. Turning Sediment into RockTurning Sediment into Rock • Diagenesis Includes:Diagenesis Includes: • RecrystallizationRecrystallization – development of more– development of more stable minerals from less stable ones.stable minerals from less stable ones. Example = CaCOExample = CaCO33 to CaMg(COto CaMg(CO33))22 • LithificationLithification – unconsolidated sediments– unconsolidated sediments are transformed into solid sedimentaryare transformed into solid sedimentary rock byrock by compactioncompaction andand cementationcementation..
  8. 8. Turning Sediment into RockTurning Sediment into Rock • Diagenesis IncludesDiagenesis Includes • CompactionCompaction:: – Sediment accumulates.Sediment accumulates. – Weight of overlying material compressesWeight of overlying material compresses deeper sediments.deeper sediments. – Deeper sediment is further buriedDeeper sediment is further buried becoming more compacted and firm.becoming more compacted and firm. – Grains are pressed increasingly closerGrains are pressed increasingly closer reducing pore space by as much as 40%reducing pore space by as much as 40% (clays).(clays). – Most significant lithification process inMost significant lithification process in fine-grained sedimentary rock (shales).fine-grained sedimentary rock (shales).
  9. 9. Diagenesis: LithificationDiagenesis: Lithification SedimentSediment RockRock
  10. 10. Compaction and LithificationCompaction and Lithification
  11. 11. Turning Sediment into RockTurning Sediment into Rock • Diagenesis IncludesDiagenesis Includes • CementationCementation:: – Most important process by whichMost important process by which sediments are transformed tosediments are transformed to sedimentary rocks.sedimentary rocks. – Chemical diagenesis that involved theChemical diagenesis that involved the precipitation of minerals carried inprecipitation of minerals carried in solution into the open pore spacessolution into the open pore spaces between individual grains.between individual grains. – Natural CementsNatural Cements includeinclude calcitecalcite,, silicasilica,, andand iron oxideiron oxide..
  12. 12. Diagenesis: LithificationDiagenesis: Lithification SedimentSediment RockRock
  13. 13. CementationCementation Typical CementsTypical Cements:: • CalciteCalcite • QuartzQuartz • Iron OxideIron Oxide
  14. 14. Types of Sedimentary RocksTypes of Sedimentary Rocks • Rock types are based on theRock types are based on the sourcesource ofof the material.the material. • Detrital RocksDetrital Rocks – Derived from both the– Derived from both the chemical and mechanical weathering ofchemical and mechanical weathering of pre-existing rock forming detritus that ispre-existing rock forming detritus that is then transported and deposited in anotherthen transported and deposited in another location.location. • Chemical RocksChemical Rocks – Sediment that was– Sediment that was once in solution and precipitated byonce in solution and precipitated by organic or inorganic processes.organic or inorganic processes.
  15. 15. Classification of Sedimentary RocksClassification of Sedimentary Rocks • Sedimentary rocks are classified based onSedimentary rocks are classified based on theirtheir texturetexture ((grain size and shapegrain size and shape) and) and compositioncomposition ((mineral contentmineral content).). • DetritalDetrital rocks are subdivided primarily based onrocks are subdivided primarily based on particle size and compositionparticle size and composition.. – The chief constituents of detrital rocks include:The chief constituents of detrital rocks include: – Clay mineralsClay minerals – FeldsparsFeldspars – QuartzQuartz – MicasMicas • ChemicalChemical rocks are subdivided primarily basedrocks are subdivided primarily based onon compositioncomposition.. – The chief constituents of chemical rocks include:The chief constituents of chemical rocks include: – CalciteCalcite – Microcrystalline QuartzMicrocrystalline Quartz – Gypsum, Halite, and SylviteGypsum, Halite, and Sylvite
  16. 16. • Two majorTwo major texturestextures are used in theare used in the classification of sedimentary rocks.classification of sedimentary rocks. • ClasticClastic – Discrete fragments and particles.Discrete fragments and particles. – All detrital rocks have a clastic texture.All detrital rocks have a clastic texture. – Some chemical rocks – coquina andSome chemical rocks – coquina and oolitic limestone – also posses clasticoolitic limestone – also posses clastic textures.textures. • Nonclastic (or Crystalline)Nonclastic (or Crystalline) – Pattern of interlocking crystals.Pattern of interlocking crystals. – May resemble an igneous rock.May resemble an igneous rock. Classification of Sedimentary RocksClassification of Sedimentary Rocks
  17. 17. Types of Sedimentary RocksTypes of Sedimentary Rocks • DetritalDetrital Sedimentary RocksSedimentary Rocks – Conglomerate or BrecciaConglomerate or Breccia – SandstoneSandstone – SiltstoneSiltstone – Shale or ClaystoneShale or Claystone • ChemicalChemical//BiochemicalBiochemical Sedimentary RocksSedimentary Rocks – EvaporitesEvaporites – Carbonate sedimentary rocks (limestones andCarbonate sedimentary rocks (limestones and dolostone)dolostone) – Siliceous sedimentary rocks (chert, diatomite)Siliceous sedimentary rocks (chert, diatomite) – Organic sedimentary rocks (Coals – peat, lignite,Organic sedimentary rocks (Coals – peat, lignite, bituminous, and anthracite)bituminous, and anthracite)
  18. 18. Identification of Sedimentary RocksIdentification of Sedimentary Rocks STOP
  19. 19. Characteristics of DetritalCharacteristics of Detrital Sedimentary RocksSedimentary Rocks
  20. 20. Detrital Sedimentary RocksDetrital Sedimentary Rocks • Detrial rocks have aDetrial rocks have a clasticclastic (broken or(broken or fragmental) texture that may consist of:fragmental) texture that may consist of: – ClastsClasts – larger pieces, such as sand or gravel.– larger pieces, such as sand or gravel. – MatrixMatrix – mud or fine-grained sediment– mud or fine-grained sediment surrounding the clasts.surrounding the clasts. – CementCement – the chemical– the chemical “glue” that holds it all“glue” that holds it all together.together. • Types of Cement:Types of Cement: – CalciteCalcite – Iron OxideIron Oxide – SilicaSilica
  21. 21. Clast SupportedClast Supported ConglomerateConglomerate (River Deposits)(River Deposits)
  22. 22. Matrix Supported ConglomerateMatrix Supported Conglomerate (Glacial/Landslide Deposits)(Glacial/Landslide Deposits) ““Modern”Modern” Glacial SedimentsGlacial Sediments 2.2 Gyr Conglomerate2.2 Gyr Conglomerate
  23. 23. Detrital Sedimentary RocksDetrital Sedimentary Rocks are Classified by Grain Sizeare Classified by Grain Size Particle size is used to distinguish amongParticle size is used to distinguish among the various types of detrital rocks.the various types of detrital rocks. • GravelGravel: Grain size greater than: Grain size greater than 2 mm2 mm.. – If rounded clasts =If rounded clasts = ConglomerateConglomerate – If angular clasts =If angular clasts = BrecciaBreccia • SandSand: Grain size: Grain size 1/16 to 2 mm1/16 to 2 mm –– SandstoneSandstone • SiltSilt: Grain size: Grain size 1/256 to 1/16 mm1/256 to 1/16 mm (gritty) –(gritty) – SiltstoneSiltstone • ClayClay: Grain size: Grain size less than 1/256 mmless than 1/256 mm (smooth)(smooth) – ShaleShale (if fissile)(if fissile) – MudstoneMudstone (if massive)(if massive)
  24. 24. Grain SizeGrain Size • Gravel ≥ 2 mmGravel ≥ 2 mm • Sand – 2 mm to 1/16 mmSand – 2 mm to 1/16 mm • Silt – 1/16 mm to 1/256 mmSilt – 1/16 mm to 1/256 mm • Clay ≤ 1/256 mmClay ≤ 1/256 mm
  25. 25. Detrital Sedimentary RocksDetrital Sedimentary Rocks are Classified by Grain Sizeare Classified by Grain Size Grain Size Rock Name Gravel Conglomerate = Rounded Clasts Breccia = Angular Clasts Sand Sandstone Silt Siltstone Clay Shale = Fissile Mudstone = Massive
  26. 26. Detrital Sedimentary RocksDetrital Sedimentary Rocks ShaleShale SandstoneSandstone ConglomerateConglomerate BrecciaBreccia
  27. 27. What Does Grain Size Tell Us?What Does Grain Size Tell Us? • The energy of the environment andThe energy of the environment and media of deposition.media of deposition. • Currents of water or air sort theCurrents of water or air sort the particles by sizeparticles by size – the stronger the– the stronger the current, the larger the particle sizecurrent, the larger the particle size carried.carried.
  28. 28. Grain Size InterpretationGrain Size Interpretation • GravelGravel • SandSand • SiltSilt • ClayClay • River, BeachRiver, Beach • River, Beach,River, Beach, DesertDesert • Delta, ShallowDelta, Shallow OceanOcean • Deep Ocean,Deep Ocean, Lake, SwampLake, Swamp • High EnergyHigh Energy • Low EnergyLow Energy STOP
  29. 29. SortingSorting • SortingSorting refers to the distribution ofrefers to the distribution of grain sizes in a rock.grain sizes in a rock. – Well SortedWell Sorted – All the grains are approximately– All the grains are approximately equal in size.equal in size. – Poorly SortedPoorly Sorted – Particles of variable size are– Particles of variable size are mixed together.mixed together.
  30. 30. Degrees of SortingDegrees of Sorting
  31. 31. What Does the Degree of Sorting TellWhat Does the Degree of Sorting Tell Us?Us? • The energy of the environment and media ofThe energy of the environment and media of depositiondeposition.. Interpretation:Interpretation: Poorly SortedPoorly Sorted Well SortedWell Sorted Transport AgentTransport Agent Gravity and Glaciers (and Rivers)Gravity and Glaciers (and Rivers) Water and WindWater and Wind
  32. 32. What Does theWhat Does the Degree of Sorting Tell Us?Degree of Sorting Tell Us? • The energy of the environment andThe energy of the environment and media of depositionmedia of deposition:: • WindblownWindblown sands are typically bettersands are typically better sorted thansorted than wave-washedwave-washed sediments.sediments. • Particles washed byParticles washed by waveswaves areare commonly better sorted than materialscommonly better sorted than materials deposited bydeposited by streamsstreams..
  33. 33. • Degree of sorting also indicatesDegree of sorting also indicates distance from the sourcedistance from the source andand deposition ratedeposition rate:: • Poor sortingPoor sorting indicates sediments wereindicates sediments were transported atransported a short distanceshort distance andand deposited rapidlydeposited rapidly.. – Examples: Alluvial Fans and Glacial TilliteExamples: Alluvial Fans and Glacial Tillite depositsdeposits • Well-sortedWell-sorted sediments indicate thesediments indicate the sediments were transported asediments were transported a longerlonger distancedistance andand deposited more graduallydeposited more gradually.. – Examples: Deep-ocean depositsExamples: Deep-ocean deposits STOP What Does theWhat Does the Degree of Sorting Tell Us?Degree of Sorting Tell Us?
  34. 34. Grain ShapeGrain Shape • Grain shapeGrain shape is described in terms ofis described in terms of roundingrounding ofof grain edges andgrain edges and sphericitysphericity (equal dimensions,(equal dimensions, or how close it is to a sphere).or how close it is to a sphere). • When currents transport sedimentary particles,When currents transport sedimentary particles, the particles collide together breaking off sharpthe particles collide together breaking off sharp edges.edges.
  35. 35. Rounding & SphericityRounding & Sphericity SphericalSpherical OblongOblong
  36. 36. Figure 3-13 (p. 72)Figure 3-13 (p. 72) Degree of rounding is expressed using the following scale:Degree of rounding is expressed using the following scale: highly angular –> angular –> subangular –> subrounded –> roundedhighly angular –> angular –> subangular –> subrounded –> rounded –> highly rounded–> highly rounded ((AA) An angular particle (all edges sharp).) An angular particle (all edges sharp). ((BB) A rounded grain that has little sphericity.) A rounded grain that has little sphericity. ((CC) A well-rounded, highly spherical grain.) A well-rounded, highly spherical grain.
  37. 37. Gravel Sized Detrital RocksGravel Sized Detrital Rocks (Subdivided Based on Grain Roundness)(Subdivided Based on Grain Roundness) BrecciaBreccia ConglomerateConglomerate
  38. 38. Grain ShapeGrain Shape • Degree of roundingDegree of rounding also indicatesalso indicates distance from sourcedistance from source and/orand/or transporttransport timetime:: • Very well rounded sandVery well rounded sand grainsgrains suggest that asuggest that a sand hassand has traveled a greattraveled a great distance from the sourcedistance from the source over a long time periodover a long time period.. • They also may haveThey also may have beenbeen recycled from olderrecycled from older sandstonessandstones.. STOP
  39. 39. Interpretation:Interpretation: Distance of TransportDistance of Transport ShortShort FarFar STOP
  40. 40. Chemical WeatheringChemical Weathering • Transport timeTransport time also affects thealso affects the mineral compositionmineral composition of aof a sedimentary deposit:sedimentary deposit: – Substantial weathering and longSubstantial weathering and long transporttransport leads to theleads to the – Gradual destruction of weaker and lessGradual destruction of weaker and less stable minerals such as feldspars andstable minerals such as feldspars and ferromagnesian minerals (Bowen’sferromagnesian minerals (Bowen’s Reaction Series).Reaction Series). – QuartzQuartz – the most stable mineral at the– the most stable mineral at the Earth’s surface survives.Earth’s surface survives.
  41. 41. Color of Sedimentary RocksColor of Sedimentary Rocks • BlackBlack andand dark graydark gray coloration incoloration in sedimentary rocks generally indicatessedimentary rocks generally indicates the presence ofthe presence of organic carbonorganic carbon and/orand/or ironiron.. • Organic carbon in sedimentaryOrganic carbon in sedimentary requiresrequires anoxic environmentalanoxic environmental conditionsconditions..
  42. 42. Color of Sedimentary RocksColor of Sedimentary Rocks • RedRed coloration incoloration in sedimentary rockssedimentary rocks indicates the presence ofindicates the presence of iron oxidesiron oxides (Ferric Iron –(Ferric Iron – FeFe+3+3 ) .) . • Red beds typicallyRed beds typically indicate deposition inindicate deposition in well-oxygenatedwell-oxygenated continental sedimentarycontinental sedimentary environmentsenvironments.. • May also be transitionalMay also be transitional or marine.or marine. Red siltstone w/ tracksRed siltstone w/ tracks Hematite-cementedHematite-cemented Sandstone (Clinton Fm.)Sandstone (Clinton Fm.)
  43. 43. Color of Sedimentary RocksColor of Sedimentary Rocks • GreenGreen andand graygray coloration incoloration in sedimentary rocks indicates thesedimentary rocks indicates the presence ofpresence of ironiron, but in a, but in a reducedreduced (rather than an oxidized) state.(rather than an oxidized) state. • Ferrous ironFerrous iron (Fe(Fe+2+2 ) generally occurs in) generally occurs in oxygen-deficient environmentsoxygen-deficient environments.. STOP
  44. 44. Overview of DetritalOverview of Detrital Sedimentary Rock TypesSedimentary Rock Types
  45. 45. Detrital Sedimentary RocksDetrital Sedimentary Rocks • Common Detrital Sedimentary RocksCommon Detrital Sedimentary Rocks ((in order of increasing particle sizein order of increasing particle size)) • ShaleShale – A very fine-grained rockA very fine-grained rock composed ofcomposed of clay-sizedclay-sized particlesparticles.. – Most common sedimentaryMost common sedimentary rock.rock. – Particles deposited in thinParticles deposited in thin layers commonly referred tolayers commonly referred to asas laminaelaminae.. – Shale isShale is fissilefissile –– splits readilysplits readily into thin, flat layersinto thin, flat layers..
  46. 46. Detrital Sedimentary RocksDetrital Sedimentary Rocks • MudstoneMudstone • Composed ofComposed of mudmud – a mixture of silt and clay.– a mixture of silt and clay. • May exhibit fissility.May exhibit fissility. • Breaks into chunks or blocks.Breaks into chunks or blocks.
  47. 47. Detrital Sedimentary RocksDetrital Sedimentary Rocks • SiltstoneSiltstone – Composed ofComposed of largely oflargely of siltsilt-- sized particlessized particles with lesser clay-with lesser clay- sized particles.sized particles. – Lacks fissilityLacks fissility.. – Breaks intoBreaks into chunks or blocks.chunks or blocks.
  48. 48. Formation of Shales to SiltstonesFormation of Shales to Siltstones • Due to their Fine Grain Size:Due to their Fine Grain Size: – Clay and silt-sized particles tends to remainClay and silt-sized particles tends to remain suspended in the water columnsuspended in the water column.. – Deposition occurs as the result ofDeposition occurs as the result of gradual settlinggradual settling from relativelyfrom relatively quietquiet,, non-turbulent currentsnon-turbulent currents.. – Lithified predominantly viaLithified predominantly via compactioncompaction.. – Clays and shales typically indicateClays and shales typically indicate low energylow energy environmentsenvironments,, sheltered from waves andsheltered from waves and currentscurrents.. – Such environments includeSuch environments include lakes (lacustrine),lakes (lacustrine), river floodplains, lagoons, and portions of deepriver floodplains, lagoons, and portions of deep ocean basinsocean basins.. – Composition and colorComposition and color can further indicate thecan further indicate the environment of deposition (e.g., coaly shales).environment of deposition (e.g., coaly shales).
  49. 49. Detrital Sedimentary RocksDetrital Sedimentary Rocks • SandstoneSandstone – Composed of sand-sized particles.Composed of sand-sized particles. – Lithified predominantly viaLithified predominantly via cementationcementation.. – Forms in aForms in a variety of environmentsvariety of environments.. – SortingSorting,, shapeshape, and, and compositioncomposition of theof the grains can be used to interpret the rock’sgrains can be used to interpret the rock’s origin and history.origin and history. – Compositional components include:Compositional components include: • QuartzQuartz – predominant mineral– predominant mineral • FeldsparFeldspar • Rock FragmentsRock Fragments
  50. 50. Major Types of SandstoneMajor Types of Sandstone • Quartz SandstoneQuartz Sandstone – Dominated by quartz; mature– Dominated by quartz; mature • ArkoseArkose – 25% or more feldspar; immature– 25% or more feldspar; immature • GraywackeGraywacke – About 30% dark fine-grained matrix;– About 30% dark fine-grained matrix; immatureimmature • Lithic SandstoneLithic Sandstone – Quartz, muscovite, chert, and– Quartz, muscovite, chert, and rock fragments. Less than 15% matrix. Immaturerock fragments. Less than 15% matrix. Immature
  51. 51. Figure 5-24 (p. 95)Figure 5-24 (p. 95) Four categories of sandstone as seen in thin sectionFour categories of sandstone as seen in thin section under the microscope.under the microscope. Diameter of field is about 4 mm.Diameter of field is about 4 mm.
  52. 52. Quartz SandstoneQuartz Sandstone
  53. 53. Composed ofComposed of well-sortedwell-sorted,, roundedrounded quartzquartz grains suggestsgrains suggests long-distance transportlong-distance transport,, highly weatheredhighly weathered, and, and moderate depositionmoderate deposition and burial ratesand burial rates.. Quartz SandstoneQuartz Sandstone
  54. 54. ArkoseArkose
  55. 55. ArkoseArkose • Composed of quartz, feldspars, and micas indicates granitic source rocks. Typically poorly sorted, angular particles with minimal chemical weathering (indicated by the presence of feldspar) suggests short-distance transport, minimal chemical weathering in an arid climate, and rapid deposition and burial.
  56. 56. Sandstone Close-UpsSandstone Close-Ups • Quartz Sandstone (left)Quartz Sandstone (left) • Arkose (Sandstone with >10% feldspar)Arkose (Sandstone with >10% feldspar)
  57. 57. Detrital Sedimentary RocksDetrital Sedimentary Rocks • Conglomerate and BrecciaConglomerate and Breccia – Both are composed ofBoth are composed of particles greater thanparticles greater than 2mm in diameter2mm in diameter (gravel) with sand, silt, and(gravel) with sand, silt, and clay particles between.clay particles between. – Particles are large enough to identify distinctiveParticles are large enough to identify distinctive rock types and thereforerock types and therefore source rockssource rocks.. – Gravels accumulate in a variety of environmentsGravels accumulate in a variety of environments and typically indicateand typically indicate steep slopes and/or verysteep slopes and/or very turbulent currentsturbulent currents.. – Examples:Examples: energetic mountain streams, strongenergetic mountain streams, strong wave activity along rapidly eroding coastline,wave activity along rapidly eroding coastline, and glacial and landslide environments.and glacial and landslide environments.
  58. 58. Detrital Sedimentary RocksDetrital Sedimentary Rocks • Conglomerate and BrecciaConglomerate and Breccia – Conglomerate consists largely ofConglomerate consists largely of roundedrounded gravels.gravels. – Breccia is composed mainly of largeBreccia is composed mainly of large angularangular particles.particles.
  59. 59. Conglomerate Deposits alongConglomerate Deposits along the Coast of Washingtonthe Coast of Washington
  60. 60. Outcrop of ConglomerateOutcrop of Conglomerate Composition of variable materials,Composition of variable materials, poorly sortedpoorly sorted, and, and roundedrounded particles suggests relativelyparticles suggests relatively short-distanceshort-distance transporttransport (but long enough to have high degree of(but long enough to have high degree of abrasion),abrasion), some mechanical and minimal chemicalsome mechanical and minimal chemical weatheringweathering, and, and rapid deposition and burialrapid deposition and burial..
  61. 61. Interbedded Sandstone andInterbedded Sandstone and ConglomerateConglomerate
  62. 62. InterbeddedInterbedded Sandstone andSandstone and ConglomerateConglomerate Suggests distinctiveSuggests distinctive periods of alternatingperiods of alternating depositional environmentsdepositional environments of high and low energy.of high and low energy.
  63. 63. BrecciaBreccia
  64. 64. BrecciaBreccia Composition of variable materials,Composition of variable materials, poorly sortedpoorly sorted,, andand angularangular particles suggestsparticles suggests short-distanceshort-distance transporttransport,, minimal mechanical and chemicalminimal mechanical and chemical weatheringweathering, and, and rapid deposition and burialrapid deposition and burial.. STOP
  65. 65. Chemical/BiochemicalChemical/Biochemical Sedimentary RocksSedimentary Rocks
  66. 66. Chemical Sedimentary RocksChemical Sedimentary Rocks • Consist of precipitated material thatConsist of precipitated material that was once in solution.was once in solution. • Precipitation of material occurs in twoPrecipitation of material occurs in two ways:ways: • Inorganic Processes:Inorganic Processes: – EvaporationEvaporation – HydrothermalHydrothermal – Chemical ActivityChemical Activity • Organic Processes:Organic Processes: – Biochemical OriginBiochemical Origin from water dwellingfrom water dwelling organismsorganisms
  67. 67. Types of Chemical/BiochemicalTypes of Chemical/Biochemical Sedimentary RocksSedimentary Rocks 1.1. Carbonate RocksCarbonate Rocks – Form by chemical– Form by chemical processes and biochemicalprocesses and biochemical processes (secreting shells).processes (secreting shells). 2.2. Siliceous RocksSiliceous Rocks – Form from– Form from chemical processes (silica replacingchemical processes (silica replacing limestone) or biochemical processeslimestone) or biochemical processes (silica-secreting organisms).(silica-secreting organisms). 3.3. EvaporitesEvaporites – Form from the– Form from the evaporation of seawater.evaporation of seawater. STOP
  68. 68. Carbonate RocksCarbonate Rocks 1.1. LimestonesLimestones – Most abundant chemical rock.Most abundant chemical rock. – Composed of predominantly ofComposed of predominantly of calcitecalcite (CaCO(CaCO33)) and secondarilyand secondarily aragonitearagonite (CaCO(CaCO33).). – MarineMarine biochemical limestonesbiochemical limestones form from pre-form from pre- existing organisms:existing organisms: • Fossiliferous LimestoneFossiliferous Limestone – coral reefs, shell fragments– coral reefs, shell fragments • CoquinaCoquina – shell fragments– shell fragments • ChalkChalk – microscopic organisms– microscopic organisms • MicriteMicrite (Microcrystalline Limestone) – microscopic organisms(Microcrystalline Limestone) – microscopic organisms – Inorganic limestones form by inorganicInorganic limestones form by inorganic processes (evaporation, chemical activity):processes (evaporation, chemical activity): • Oolitic LimestoneOolitic Limestone • TravertineTravertine • Crystalline LimestoneCrystalline Limestone • MicriteMicrite (Microcrystalline Limestone)(Microcrystalline Limestone) 2.2. DolostonesDolostones (or(or DolomitesDolomites)) – Composed of Dolomite (CaMg (COComposed of Dolomite (CaMg (CO33))22))
  69. 69. Formation of LimestonesFormation of Limestones • Most limestones are theMost limestones are the direct or indirectdirect or indirect result of biologic activityresult of biologic activity.. – Organic:Organic: • May contain shells or the remains of other marineMay contain shells or the remains of other marine organisms (microscopic or macroscopic).organisms (microscopic or macroscopic). MicroscopicMicroscopic Foraminifera (chalk)Foraminifera (chalk) Shell FragmentsShell Fragments (coquina)(coquina) Fossiliferous LimestoneFossiliferous Limestone
  70. 70. Formation of LimestonesFormation of Limestones • Most limestones are theMost limestones are the direct or indirectdirect or indirect result of biologic activityresult of biologic activity.. – Inorganic:Inorganic: • Inorganic limestones precipitate from CaCOInorganic limestones precipitate from CaCO33-bearing-bearing solutions.solutions. • Form inForm in cavescaves andand hotspringshotsprings whenwhen groundwatergroundwater encounters air and COencounters air and CO22 comes out of solution causingcomes out of solution causing CaCOCaCO33 to precipitate.to precipitate. • Precipitate from seawaterPrecipitate from seawater as a result of biologic activityas a result of biologic activity such as photosynthesis by microscopic marine plantssuch as photosynthesis by microscopic marine plants and algae removes COand algae removes CO22 from seawater leading to calciumfrom seawater leading to calcium carbonate precipitation.carbonate precipitation. • Precipitation occurs due to changes in water chemistry,Precipitation occurs due to changes in water chemistry, pressure, and/or temperature conditions.pressure, and/or temperature conditions.
  71. 71. Characteristics of the EnvironmentCharacteristics of the Environment of Marine Carbonate Formationof Marine Carbonate Formation • Some carbonate rocks form inSome carbonate rocks form in lakeslakes,, cavescaves,, andand hot springshot springs.. • Most carbonate rocks form in the shallowMost carbonate rocks form in the shallow marine environmentsmarine environments:: – MarineMarine – Warm WaterWarm Water – Shallow WaterShallow Water (less than 200 m deep)(less than 200 m deep) – Tropical ClimateTropical Climate (30 ° N - 30 ° S of equator)(30 ° N - 30 ° S of equator) – Clear WaterClear Water (low to no terrigenous input)(low to no terrigenous input) – Sunlight RequiredSunlight Required for photosynthesis by algaefor photosynthesis by algae
  72. 72. Organic Chemical Sedimentary RocksOrganic Chemical Sedimentary Rocks • Fossiliferous LimestonesFossiliferous Limestones – Limestones containing various sized shells and/orLimestones containing various sized shells and/or other fossil fragments cemented typically withother fossil fragments cemented typically with calcitecalcite.. – Coral ReefsCoral Reefs andand shell bedsshell beds create marine fossiliferouscreate marine fossiliferous limestones from the invertabrate animal’s secretion oflimestones from the invertabrate animal’s secretion of theirtheir external calcarenous skeletonsexternal calcarenous skeletons..
  73. 73. ModernModern CoralCoral Reef atReef at BoraBora Bora inBora in FrenchFrench PolynesiaPolynesia
  74. 74. El CapitanEl Capitan Peak inPeak in GuadalupeGuadalupe NationalNational Park, Texas -Park, Texas - ExposedExposed Permian-Permian- agedaged MassiveMassive Coral ReefCoral Reef ComplexComplex
  75. 75. • Micritic LimestonesMicritic Limestones • Microcrystalline limestonesMicrocrystalline limestones composed of clay-composed of clay- sized calcite particles (sized calcite particles (lime mudslime muds) of biological) of biological (organic) microscopic skeletons of(organic) microscopic skeletons of calcareouscalcareous algaealgae. Deposited in generally. Deposited in generally quiet watersquiet waters.. • Can also have chemical (inorganic) origin by theCan also have chemical (inorganic) origin by the precipitation of calcite from seawater.precipitation of calcite from seawater. Organic Chemical Sedimentary RocksOrganic Chemical Sedimentary Rocks
  76. 76. • ChalkChalk – ChalkChalk is a soft, porous rockis a soft, porous rock composed of almost entirely of thecomposed of almost entirely of the hard parts ofhard parts of microscopicmicroscopic calcareous marine organismscalcareous marine organisms.. Organic Chemical Sedimentary RocksOrganic Chemical Sedimentary Rocks
  77. 77. CoccolithophoridCoccolithophorid. Shells are composed. Shells are composed of calcium carbonate. Image magnifiedof calcium carbonate. Image magnified 7,000 times.7,000 times. LimancinaLimancina, a tiny swimming marine snail,, a tiny swimming marine snail, or pterapod.or pterapod. The foot is modified into a pair of winglike fins,The foot is modified into a pair of winglike fins, shown at left. At the right are two empty shellsshown at left. At the right are two empty shells Types of Sea Floor SedimentsTypes of Sea Floor Sediments • Biogenous (or Organic) SedimentBiogenous (or Organic) Sediment – Calcareous OozesCalcareous Oozes – Form chalk in waters less than– Form chalk in waters less than about 4,000-5,000 m – foraminifera, pteropods, andabout 4,000-5,000 m – foraminifera, pteropods, and coccolithophores.coccolithophores.
  78. 78. Origin of Carbonate SedimentsOrigin of Carbonate Sediments and Rocksand Rocks MuchMuch lime mudlime mud forms from theforms from the disintegration ofdisintegration of calcareous algaecalcareous algae (such as(such as HalimedaHalimeda andand PenicillusPenicillus).). When theWhen the calcareous algaecalcareous algae die, their skeletonsdie, their skeletons break down andbreak down and disintegratedisintegrate producingproducing aragonitearagonite needle mudsneedle muds.. TheseThese lime muds lithify tolime muds lithify to form fine-grainedform fine-grained limestone.limestone.
  79. 79. MicroscopicMicroscopic Hard PartsHard Parts (Skeletons) of(Skeletons) of RadiolariansRadiolarians andand ForaminiferaForaminifera
  80. 80. • CoquinaCoquina – CoquinaCoquina is a coarse-grained rockis a coarse-grained rock composed of poorly-cementedcomposed of poorly-cemented shells and shell fragments.shells and shell fragments. Organic Chemical Sedimentary RocksOrganic Chemical Sedimentary Rocks
  81. 81. • Crystalline LimestoneCrystalline Limestone – Crystalline limestone usually forms when theCrystalline limestone usually forms when the mineral calcite (CaCO3) precipitates frommineral calcite (CaCO3) precipitates from seawater.seawater. – Diagenesis recrystallizes calcite intoDiagenesis recrystallizes calcite into intergranular network of crystals.intergranular network of crystals. Inorganic Chemical Sedimentary RocksInorganic Chemical Sedimentary Rocks
  82. 82. • Oolitic LimestoneOolitic Limestone – Oolitic limestoneOolitic limestone is composed of smallis composed of small spherical grains of CaCO3 calledspherical grains of CaCO3 called ooids.ooids. Inorganic Chemical Sedimentary RocksInorganic Chemical Sedimentary Rocks
  83. 83. Origin of Ooids inOrigin of Ooids in Oolitic LimestonesOolitic Limestones • OoidsOoids are tiny spheresare tiny spheres composed of concentricallycomposed of concentrically laminated calcium carbonate.laminated calcium carbonate. • Ooids form in shallowOoids form in shallow marine waters and begin asmarine waters and begin as tiny “tiny “seedseed” particles” particles (commonly shell fragments)(commonly shell fragments) areare constantly agitated byconstantly agitated by currentscurrents.. • As the seeds are rolledAs the seeds are rolled around in the CaCO3around in the CaCO3 supersaturated warm waters,supersaturated warm waters, layers of CaCO3 arelayers of CaCO3 are concentrically precipitatedconcentrically precipitated around the seed.around the seed.
  84. 84. • TravertineTravertine – TravertineTravertine forms informs in cavescaves (stalagtites,(stalagtites, stalagmites, curtains, etc.)stalagmites, curtains, etc.) when groundwaterwhen groundwater encounters air, COencounters air, CO22 comes out of solution andcomes out of solution and causing CaCOcausing CaCO33 to precipitate.to precipitate. – Also forms from precipitation of calcite aroundAlso forms from precipitation of calcite around hot springshot springs.. Inorganic Chemical Sedimentary RocksInorganic Chemical Sedimentary Rocks
  85. 85. Carbonates: DolomiteCarbonates: Dolomite • Composed of dolomiteComposed of dolomite CaMg(CaCOCaMg(CaCO33))22 – a– a calcium-calcium- magnesium carbonatemagnesium carbonate mineral.mineral. • Dolomite (Dolostone) can formDolomite (Dolostone) can form by the direct precipitation ofby the direct precipitation of seawater in a few areas of theseawater in a few areas of the world whereworld where intenseintense evaporation of seawaterevaporation of seawater concentrates the magnesiumconcentrates the magnesium.. • Typically formed secondarilyTypically formed secondarily from limestone.from limestone. • Magnesium that has beenMagnesium that has been concentrated in sea waterconcentrated in sea water replacesreplaces some of the calcium insome of the calcium in the CaCOthe CaCO33 structurestructure ((diagenesisdiagenesis).). STOP
  86. 86. Siliceous Sedimentary RocksSiliceous Sedimentary Rocks • ChertChert – Made of microcrystalline quartz (silica).Made of microcrystalline quartz (silica). – Massive and hard.Massive and hard. – Often replaces limestone.Often replaces limestone. – Varieties include the following:Varieties include the following: • FlintFlint – dark in color due to organic matter– dark in color due to organic matter • JasperJasper – red in color due to iron oxide– red in color due to iron oxide • AgateAgate – banded form or chert– banded form or chert
  87. 87. • ChertChert – ChertChert has various modes of origin:has various modes of origin: • InorganicInorganic – Precipitated from groundwater– Precipitated from groundwater as nodules.as nodules. • InorganicInorganic – Precipitated from groundwater– Precipitated from groundwater associated with the decomposition of lavaassociated with the decomposition of lava flows and layers of volcanic ash (silica-rich).flows and layers of volcanic ash (silica-rich). • OrganicOrganic –– Biochemical SedimentBiochemical Sediment – Siliceous– Siliceous ooze (gel) derived from silica skeletons ofooze (gel) derived from silica skeletons of marine organisms (diatoms andmarine organisms (diatoms and radiolarians).radiolarians). Siliceous Sedimentary RocksSiliceous Sedimentary Rocks
  88. 88. Modern Marine DiatomsModern Marine Diatoms Diatom shells are composed of silicaDiatom shells are composed of silica and have two perforated structuresand have two perforated structures that overlap like the two parts of athat overlap like the two parts of a shallow round box for pills.shallow round box for pills. RadiolariaRadiolaria These protistans build their skeletons of silica.These protistans build their skeletons of silica. The structures tend to be modifications of either aThe structures tend to be modifications of either a spherical (A) or helmet (B) shape. Imagespherical (A) or helmet (B) shape. Image magnified 100 times.magnified 100 times. Types of Sea Floor SedimentsTypes of Sea Floor Sediments • Biogenous (or Organic)Biogenous (or Organic) SedimentSediment – Siliceous OozesSiliceous Oozes –– Radiolarians and DiatomsRadiolarians and Diatoms
  89. 89. Siliceous Sedimentary RocksSiliceous Sedimentary Rocks • DiatomiteDiatomite – Made of microscopicMade of microscopic planktonic organisms calledplanktonic organisms called diatomsdiatoms.. – Resembles chalk, but doesResembles chalk, but does not fizz in acid.not fizz in acid.
  90. 90. EvaporitesEvaporites • EvaporationEvaporation triggers deposition of chemicaltriggers deposition of chemical precipitates.precipitates. • Formed fromFormed from dried basin areasdried basin areas that werethat were submerged by shallow arms of sea withsubmerged by shallow arms of sea with littlelittle or no connection to open oceanor no connection to open ocean.. • When seawater evaporates, mineralsWhen seawater evaporates, minerals precipitate in sequence according to theirprecipitate in sequence according to their solubility formingsolubility forming salt flatssalt flats.. • GypsumGypsum precipitates beforeprecipitates before halitehalite, which, which precipitates beforeprecipitates before sylvitesylvite:: 1.1. Rock GypsumRock Gypsum – Composed of gypsum (CaSO– Composed of gypsum (CaSO44 . 2H. 2H22O)O) 2.2. Rock SaltRock Salt – Composed of halite (NaCl)– Composed of halite (NaCl) 3.3. SylviteSylvite – Composed of potassium chloride (KCl)– Composed of potassium chloride (KCl)
  91. 91. Rock Salt (Halite)Rock Salt (Halite)
  92. 92. Bonneville Salt Flats, UtahBonneville Salt Flats, Utah
  93. 93. Layered Rock GypsumLayered Rock Gypsum
  94. 94. Organic Sedimentary Rocks – CoalOrganic Sedimentary Rocks – Coal • Composed ofComposed of organic matterorganic matter such as trees,such as trees, bark, wood, leaves, etc. buried for millionsbark, wood, leaves, etc. buried for millions of years.of years. • Stages in coal formation (in order) as aStages in coal formation (in order) as a function of increasing depth of burialfunction of increasing depth of burial ((increase in temperature and pressureincrease in temperature and pressure):): • Plant MaterialPlant Material • PeatPeat • LigniteLignite • Bituminous CoalBituminous Coal • Anthracite CoalAnthracite Coal
  95. 95. SuccessiveSuccessive Stages inStages in CoalCoal FormationFormation
  96. 96. • Stages of Coal FormationStages of Coal Formation 1.1. Plant MaterialPlant Material – Accumulations of large– Accumulations of large amounts of plant remains in aamounts of plant remains in a stagnantstagnant,, oxygen-deficient environmentoxygen-deficient environment ((swampswamp),), where oxidation and thus completewhere oxidation and thus complete decomposition of the plant remains is notdecomposition of the plant remains is not possible.possible. Anaerobic bacteriaAnaerobic bacteria partially decompose plantpartially decompose plant remains releasing oxygen and hydrogen,remains releasing oxygen and hydrogen, thereby increasing the carbon percentagethereby increasing the carbon percentage and creating a layer ofand creating a layer of peat.peat. Organic Sedimentary Rocks – CoalOrganic Sedimentary Rocks – Coal
  97. 97. • Stages of Coal FormationStages of Coal Formation 2.2. PeatPeat – A soft brown material in which– A soft brown material in which plant structures are still easilyplant structures are still easily recognizablerecognizable 3.3. LigniteLignite – With shallow burial, peat– With shallow burial, peat slowly changes toslowly changes to lignitelignite – a soft– a soft brown coalbrown coal • Increase temperature and pressureIncrease temperature and pressure squeezes out the volatiles (water andsqueezes out the volatiles (water and organic gases) increasing the proportionorganic gases) increasing the proportion of fixed carbonof fixed carbon • The greater the carbon content, theThe greater the carbon content, the greater the coal’s energy rankinggreater the coal’s energy ranking Organic Sedimentary Rocks – CoalOrganic Sedimentary Rocks – Coal
  98. 98. Successive Stages in Coal FormationSuccessive Stages in Coal Formation
  99. 99. • Stages of Coal FormationStages of Coal Formation 4.4. BituminousBituminous – Deeper burial– Deeper burial transforms lignite to bituminoustransforms lignite to bituminous coal – a soft black coal.coal – a soft black coal. 5.5. AnthraciteAnthracite – Forms during– Forms during regional metamorphism underregional metamorphism under increased temperature andincreased temperature and pressure.pressure. • AnthraciteAnthracite is a very hard, black,is a very hard, black, shiny,shiny, metamorphic rock.metamorphic rock. Organic Sedimentary Rocks – CoalOrganic Sedimentary Rocks – Coal
  100. 100. Successive Stages in Coal FormationSuccessive Stages in Coal Formation STOP
  101. 101. Sedimentary EnvironmentsSedimentary Environments of Depositionof Deposition
  102. 102. Sedimentary EnvironmentsSedimentary Environments • A geographic setting where sediment isA geographic setting where sediment is accumulating.accumulating. • Includes all of the physical, chemical,Includes all of the physical, chemical, biological and geographicbiological and geographic conditionsconditions underunder which sediments are deposited.which sediments are deposited. • ByBy comparingcomparing modern sedimentary depositsmodern sedimentary deposits with ancient sedimentary rocks, thewith ancient sedimentary rocks, the depositional conditions can be interpreted.depositional conditions can be interpreted.
  103. 103. Sedimentary EnvironmentsSedimentary Environments • Use characteristics such asUse characteristics such as grain sizegrain size,, grain shapegrain shape,, compositioncomposition, etc. to, etc. to determine:determine: – OriginOrigin – HistoryHistory – Method and Length of TransportMethod and Length of Transport – Nature and Environment of DepositionNature and Environment of Deposition – Reconstruct Ancient Environments andReconstruct Ancient Environments and Geographical RelationshipsGeographical Relationships
  104. 104. The Characteristics of a SedimentaryThe Characteristics of a Sedimentary Environment Depend on:Environment Depend on: 1.1. Tectonic SettingTectonic Setting 2.2. Rocks in the Source Area from which theRocks in the Source Area from which the Sediment is DerivedSediment is Derived 3.3. Climate (and its effect on weathering)Climate (and its effect on weathering) 4.4. Method of Sediment TransportMethod of Sediment Transport 5.5. Location of Deposition/FormationLocation of Deposition/Formation 6.6. Physical, Chemical, and Biological ProcessesPhysical, Chemical, and Biological Processes in the Depositional Environmentin the Depositional Environment 7.7. Post-Depositional Processes of LithificationPost-Depositional Processes of Lithification (Cementation, Compaction, Recrystallization)(Cementation, Compaction, Recrystallization) 8.8. TimeTime
  105. 105. Depositional EnvironmentsDepositional Environments There are three broad categories ofThere are three broad categories of Depositional Environments:Depositional Environments: • Marine EnvironmentsMarine Environments – Ocean– Ocean • Transitional EnvironmentsTransitional Environments – Along contact between ocean and land– Along contact between ocean and land • Continental EnvironmentsContinental Environments – On land– On land
  106. 106. Marine DepositionalMarine Depositional EnvironmentsEnvironments • Shallow (up to about 200 meters depth)Shallow (up to about 200 meters depth) – Land-derived sediments deposited on theLand-derived sediments deposited on the continental shelf (coarser-grained – sands,continental shelf (coarser-grained – sands, silts, and clays).silts, and clays). – Coral reefsCoral reefs • Deep (seaward of continental shelves)Deep (seaward of continental shelves) – Deep-sea sediments – fine-grained sedimentsDeep-sea sediments – fine-grained sediments (silts and clays) that have remained entrained(silts and clays) that have remained entrained in water column for long periods of time andin water column for long periods of time and transported great distances. Originate attransported great distances. Originate at continental shelf as the result of turbiditycontinental shelf as the result of turbidity currents (deep-sea fans).currents (deep-sea fans).
  107. 107. MarineMarine DepositionalDepositional EnvironmentsEnvironments 1.1. ContinentalContinental ShelfShelf 2.2. ContinentalContinental SlopeSlope 3.3. ContinentalContinental RiseRise 4.4. Abyssal PlainAbyssal Plain
  108. 108. Types of Sea Floor SedimentsTypes of Sea Floor Sediments • Terrigenous SedimentTerrigenous Sediment – Mineral grains from weathered continentalMineral grains from weathered continental rocks.rocks. – Fine-grained sediment (clay, mud).Fine-grained sediment (clay, mud). – Accumulates slowly (5,000 to 50,000 years toAccumulates slowly (5,000 to 50,000 years to deposit 1 cm).deposit 1 cm). – Color may be black,Color may be black, redred, or, or brownbrown..
  109. 109. Marine Depositional EnvironmentsMarine Depositional Environments Location Water Depth Slope Width Features Sediments Sedimentary Rocks Continental Shelf ● Flooded edge of Continent. ● Flooding occurred when the glaciers melted about 10,000 years ago. Shallow water (less than 200 m deep) Relatively flat (slope < 0.1º) Up to 300 km wide (average s 80 km wide) ● Exposed to waves, tides, and currents. ● Locally cut by submarine canyons (eroded by rivers during Ice Age low sea level stand). ● Covered by land derived detrital sediments pebbles, sand, silt, and clay. ● Larger sedimentary grains are deposited closer to shore. ● Coral reefs and carbonate sediments in tropical areas. ● Pebble Conglomerates, Sandstones, Siltstones, Mudstones, and Shales ● Organic Limestones – Fossiliferous Limestones, Oolitic Limestones, Coral Reef Limestones, and Coquina ● Evaporites in enclosed seas Continental Slope Seaward of continental shelf. Steeper slope at edge of continent. Deeper water More steeply inclined. (slope 3 – 6º) ~20 km wide ● Boundary between continental and oceanic crust. ● Rapid sediment transport from continental shelf down slope by dense, muddy turbidity currents. ● Sediments pass seaward to the continental rise and abyssal plain. ● Turbidites – Fining-upward sequence with a base of pebble conglomerates in a sandy matrix that grade up through coarse to medium sandstones, followed by silty sandstones, and finally siltstones and shales. This vertical succession of changing lithology is representative of strong to waning flow regime currents and their corresponding sedimentation. Continental Rise Base of the continental slope. 1,400 to 3,200 m More gradual slope Up to 100s of km wide ● Submarine fans form off submarine canyons. ● Turbidity currents form submarine fans off submarine canyons. ● Sediments pass seaward into the abyssal plain. Abyssal Plain Deep ocean floor 3 to 5 km+ (2 - 3 miles+ ) Nearly flat NA ● Covered by very fine- grained detrital sediments and shells of microscopic organisms that have remained entrained in water column for long periods of time and transported great distances. ● Originate at continental shelf as the result of turbidity currents (deep-sea fans). ● Siltstones, Mudstones, and Shales ● Fine-grained Inorganic Limestones (Micritic and Crystalline) ● Fine-grained Organic Limestones – Foraminifera forming Chalk or Micritic Limestones ● Fine-grained Inorganic Siliceous Rocks – Diatoms forming Diatomite ● Chert (Radiolarians and Volcanic Ash)
  110. 110. Transitional DepositionalTransitional Depositional EnvironmentsEnvironments • Environments at or near the transitionEnvironments at or near the transition between the land and the sea.between the land and the sea. • Consist of land-derived sedimentsConsist of land-derived sediments deposited on the continental shelf (coarser-deposited on the continental shelf (coarser- grained – sands, silts, and clays).grained – sands, silts, and clays). • Forming pebble conglomerates,Forming pebble conglomerates, sandstones, siltstones, mudstones, andsandstones, siltstones, mudstones, and shales.shales. • CarbonatesCarbonates
  111. 111. TransitionalTransitional DepositionalDepositional EnvironmentsEnvironments 1.1. DeltasDeltas 2.2. BeachesBeaches 3.3. Barrier IslandsBarrier Islands 4.4. LagoonsLagoons 5.5. Tidal FlatsTidal Flats 6.6. EstuariesEstuaries
  112. 112. Transitional Depositional EnvironmentsTransitional Depositional Environments Description Location Features Sediments Sedimentary Rocks Deltas ● Fan-shaped accumulations of sediment. ● Forms where a river flows into a standing body of water, such as a lake or the sea. ● The delta builds seaward (or progrades) as sediment is deposited at the river mouth. ● Coarser sediment is deposited near the mouth of the river. ● Finer sediment is carried seaward and deposited in deeper water. ● Pebble Conglomerates, Sandstones, Siltstones, Mudstones, and Shales Beaches and Barrier Islands ● A long, relatively narrow island running parallel to the mainland. ● Served to protect the coast from erosion by surf and tidal surges. ● Barrier Islands are separated from the mainland by a lagoon (or salt marsh) ● Exposed to wave energy ● Marine fauna ● Dominated by sand ● Associated with lagoon (or salt marsh) deposits ● Associated with tidal flat deposits ● Beaches – Quartz Sandstones, other sandstones, Conglomerates ● Barrier Islands – Quartz Sandstones ● Lagoons and Tidal Flats – Siltstones, Mudstones, and Shales Lagoons ● Shallow bodies of water. ● Landward side of barrier islands. ● Also present behind reefs, or in the center of atolls. ● Protected from the pounding of the ocean waves by barrier islands. ● Contain finer sediment than the beaches and barrier islands (usually silt and clay) ● Siltstones, Mudstones, and Shales Tidal Flats ● Nearly flat, low relief areas. ● Border lagoons, shorelines, and estuaries ● Periodically flooded and exposed by tides (usually twice each day) ● May be marshy, muddy, sandy or mixed sediment types (terrigenous or carbonate) ● Sandy Siltstones, Mudstones, and Shales ● Carbonates ● Laminations and ripples are common. ● Sediments are intensely burrowed. ● Stromatolites may be present (if conditions are appropriate) Estuaries ● Mouth of a river drowned by the sea. ● Many estuaries formed due to sea level rise as glaciers melted at end of last Ice Age. ● Some formed due to tectonic subsidence. ● Forms where a river flows into a standing body of water, such as a lake or the sea. ● Brackish water (mixture of fresh and salt) ● May trap large volumes of sediment. ● Sand, silt, and clay may be deposited depending on energy level ● Sandstones, Siltstones, Mudstones, and Shales
  113. 113. Fan Delta Bird-Foot Delta
  114. 114. • Subenvironments of a Barrier Island ComplexSubenvironments of a Barrier Island Complex Barrier Island ComplexBarrier Island Complex
  115. 115. TheThe OuterOuter Banks –Banks – BarrierBarrier IslandIsland ComplexComplex
  116. 116. Tidal FlatsTidal Flats
  117. 117. EstuariesEstuaries North Carolina's Neuse River EstuaryNorth Carolina's Neuse River Estuary
  118. 118. Continental DepositionalContinental Depositional EnvironmentsEnvironments • Continental environments are thoseContinental environments are those environments which are present on theenvironments which are present on the continents (as opposed to in the oceans).continents (as opposed to in the oceans). • Consist of land-derived sediments deposited inConsist of land-derived sediments deposited in various sedimentary environments (boulders,various sedimentary environments (boulders, pebbles, sands, silts, and clays).pebbles, sands, silts, and clays). • Detrital sedimentary rocks – conglomerates,Detrital sedimentary rocks – conglomerates, brecias, sandstones, siltstones, mudstones, andbrecias, sandstones, siltstones, mudstones, and shales.shales. • Inorganic Carbonates – hotspring and caveInorganic Carbonates – hotspring and cave formationsformations • Evaporites in desert climatesEvaporites in desert climates
  119. 119. ContinentalContinental DepositionalDepositional EnvironmentsEnvironments 1.1. Rivers or FluvialRivers or Fluvial EnvironmentsEnvironments 2.2. Lacustrine (orLacustrine (or Lake)Lake) EnvironmentsEnvironments 3.3. GlacialGlacial EnvironmentsEnvironments 4.4. AeolianAeolian EnvironmentsEnvironments
  120. 120. Continental DepositionalContinental Depositional EnvironmentsEnvironments • Fluvial – dominated by erosion andFluvial – dominated by erosion and deposition associated with streams.deposition associated with streams. – Stream channel deposits, floodplains, terraceStream channel deposits, floodplains, terrace deposits, bars, alluvial fans, landslides/massdeposits, bars, alluvial fans, landslides/mass movement, swamps, meandermovement, swamps, meander scars, lakesscars, lakes Land-derived sediments variable grain sizes – gravel, sands, silts, and claysLand-derived sediments variable grain sizes – gravel, sands, silts, and clays
  121. 121. Lacustrine Environments (Lakes)Lacustrine Environments (Lakes) • May be large or small.May be large or small. • May be shallow or deep.May be shallow or deep. • Filled withFilled with terrigenous, carbonate, orterrigenous, carbonate, or evaporitic sedimentsevaporitic sediments.. • Sediments are typicallySediments are typically fine-grainedfine-grained butbut may be coarse near the edges.may be coarse near the edges. • Fine sediment and organic matter settlingFine sediment and organic matter settling in some lakes produced laminated oilin some lakes produced laminated oil shales.shales. • Playa lakesPlaya lakes are shallow, temporary lakesare shallow, temporary lakes that form in arid regions. They periodicallythat form in arid regions. They periodically dry up as a result of evaporation.dry up as a result of evaporation.
  122. 122. Continental DepositionalContinental Depositional EnvironmentsEnvironments • Glacial – dominated by erosion andGlacial – dominated by erosion and deposition associated with glaciers.deposition associated with glaciers. – Terminal, lateral, medial, ground,Terminal, lateral, medial, ground, recessional, and end moraines;recessional, and end moraines; outwash plains; drumlins; eskersoutwash plains; drumlins; eskers Land-derived sediments variable grain sizes – gravel, sands, silts, and claysLand-derived sediments variable grain sizes – gravel, sands, silts, and clays
  123. 123. Continental DepositionalContinental Depositional EnvironmentsEnvironments • Eolian – dominated by erosion andEolian – dominated by erosion and deposition associated with winddeposition associated with wind.. – Sand dunes, playa lakesSand dunes, playa lakes Land-derived sediments finer-grained –Land-derived sediments finer-grained – sands and siltssands and silts
  124. 124. Sedimentary StructuresSedimentary Structures
  125. 125. • Sedimentary Structures:Sedimentary Structures: – Features visible at theFeatures visible at the scale of an outcropscale of an outcrop.. – Formed at the time of deposition or shortlyFormed at the time of deposition or shortly thereafter, but before lithification.thereafter, but before lithification. – Manifestations of theManifestations of the physical and biologicalphysical and biological processesprocesses that operated in depositionalthat operated in depositional environments.environments. – May beMay be created during depositioncreated during deposition by the water orby the water or wind which moves the sediment.wind which moves the sediment. – MayMay form after depositionform after deposition – such as footprints,– such as footprints, worm trails, or mudcracks.worm trails, or mudcracks. – Provide information about theProvide information about the environmentalenvironmental conditionsconditions under which the sediment was deposited.under which the sediment was deposited. – Some structures form inSome structures form in quiet waterquiet water underunder lowlow energyenergy conditions, whereas others form inconditions, whereas others form in movingmoving waterwater oror high energyhigh energy conditions.conditions. Sedimentary StructuresSedimentary Structures
  126. 126. Sedimentary StructuresSedimentary Structures • Stratification:Stratification: – Layering or BeddingLayering or Bedding – The most obvious feature of sedimentaryThe most obvious feature of sedimentary rocks.rocks. – The layers (or beds or strata) are visibleThe layers (or beds or strata) are visible because of differences in the color,because of differences in the color, texture, or composition of adjacent beds.texture, or composition of adjacent beds.
  127. 127. • Sedimentary rocks generally haveSedimentary rocks generally have beddingbedding oror stratificationstratification BeddingBedding – Individual layers less than 1 cm thick are laminations • common in mudrocks – Beds are thicker than 1 cm • common in rocks with coarser grains
  128. 128. • Some beds show an upward gradual decreaseSome beds show an upward gradual decrease in grain size, known asin grain size, known as graded beddinggraded bedding Graded BeddingGraded Bedding • Graded beddingGraded bedding is common inis common in turbidity currentturbidity current depositsdeposits – which formwhich form when sediment-when sediment- water mixtureswater mixtures flow along theflow along the seafloorseafloor – As they slow,As they slow, – the largestthe largest particles settleparticles settle outout – then smallerthen smaller onesones
  129. 129. Graded BeddingGraded Bedding
  130. 130. InterbeddedInterbedded Sandstone andSandstone and ConglomerateConglomerate (Sandstone(Sandstone exhibits gradedexhibits graded bedding)bedding)
  131. 131. • Cross-bedding forms when layers come toCross-bedding forms when layers come to restrest – at an angle to the surfaceat an angle to the surface – upon which they accumulateupon which they accumulate – as on the downwind side of a sand duneas on the downwind side of a sand dune • Cross-beds result from transportCross-beds result from transport – by either water or windby either water or wind • The beds areThe beds are inclinedinclined or dip downwardor dip downward – in the direction of the prevailing currentin the direction of the prevailing current • They indicate ancient current directions,They indicate ancient current directions, – oror paleocurrentspaleocurrents • They are useful for relative datingThey are useful for relative dating – of deformed sedimentary rocksof deformed sedimentary rocks Cross-Bedding orCross-Bedding or Cross-StratificationCross-Stratification
  132. 132. Cross-Bedding orCross-Bedding or Cross-StratificationCross-Stratification
  133. 133. Cross-BeddingCross-BeddingInsert Animation #17 – Cross BeddingInsert Animation #17 – Cross Bedding Cross-Bedding orCross-Bedding or Cross-StratificationCross-Stratification
  134. 134. • Tabular cross-Tabular cross- beddingbedding formsforms by deposition onby deposition on sand wavessand waves Tabular Cross-BeddingTabular Cross-Bedding • Tabular cross-Tabular cross- beddingbedding in the Upperin the Upper Cretaceous TwoCretaceous Two Medicine FormationMedicine Formation in Montanain Montana
  135. 135. Tabular Cross-BeddingTabular Cross-Bedding
  136. 136. Trough Cross-Trough Cross- BeddingBedding • Trough cross-Trough cross- beddingbedding formed byformed by migrating dunesmigrating dunes • Trough cross-Trough cross- bedsbeds in thein the Pliocene Six MilePliocene Six Mile Creek Formation,Creek Formation, MontanaMontana
  137. 137. • Small-scale alternating ridges and troughsSmall-scale alternating ridges and troughs – known asknown as ripple marksripple marks are commonare common – on bedding planes, especially in sandstoneon bedding planes, especially in sandstone • Current Ripple MarksCurrent Ripple Marks – form in response to water or wind currentsform in response to water or wind currents – flowing in one directionflowing in one direction – and haveand have asymmetricasymmetric profiles allowing geologistsprofiles allowing geologists – to determineto determine paleocurrent directionspaleocurrent directions • Wave-Formed Ripple MarksWave-Formed Ripple Marks – result from theresult from the to-and-fro motion of wavesto-and-fro motion of waves – tend to betend to be symmetricalsymmetrical • Useful for relative dating of deformedUseful for relative dating of deformed sedimentary rocks.sedimentary rocks. Ripple MarksRipple Marks
  138. 138. • Ripples with anRipples with an asymmetricalasymmetrical shapeshape • In the close-up ofIn the close-up of one ripple,one ripple, – the internalthe internal structurestructure – shows small-scaleshows small-scale cross-beddingcross-bedding • The photo showsThe photo shows current ripplescurrent ripples – that formed in athat formed in a small streamsmall stream channelchannel – with flow from rightwith flow from right to leftto left Current Ripple MarksCurrent Ripple Marks
  139. 139. Current Ripple MarksCurrent Ripple Marks
  140. 140. • As the wavesAs the waves wash backwash back and forth,and forth, – symmetricalsymmetrical ripples formripples form • The photoThe photo shows wave-shows wave- formed rippleformed ripple marksmarks – in shallowin shallow seawaterseawater Wave-Formed RipplesWave-Formed Ripples
  141. 141. • When clay-rich sediments dry, they shrinkWhen clay-rich sediments dry, they shrink – and crack into polygonal patternsand crack into polygonal patterns – bounded by fractures calledbounded by fractures called mud cracksmud cracks • Mud cracks requireMud cracks require wetting and dryingwetting and drying to form,to form, Mud CracksMud Cracks – as along aas along a lakeshorelakeshore – or aor a river floodriver flood plainplain – or where mud isor where mud is exposed atexposed at lowlow tide along atide along a seashoreseashore
  142. 142. • Mud cracksMud cracks typically fill intypically fill in – with sedimentwith sediment – when they arewhen they are preservedpreserved – as seen hereas seen here Ancient Mud CracksAncient Mud Cracks • Mud cracks in ancient rocksMud cracks in ancient rocks
  143. 143. Mud CracksMud Cracks A polygonal pattern of cracks producedA polygonal pattern of cracks produced on the surface of mud as it drieson the surface of mud as it dries
  144. 144. • Biogenic Sedimentary StructuresBiogenic Sedimentary Structures include:include: – TracksTracks – BurrowsBurrows – TrailsTrails • CalledCalled Trace FossilsTrace Fossils • Extensive burrowing by organismsExtensive burrowing by organisms – is calledis called bioturbationbioturbation • It may alter sediments so thoroughlyIt may alter sediments so thoroughly – that other structures are disrupted orthat other structures are disrupted or destroyed.destroyed. Biogenic Sedimentary StructuresBiogenic Sedimentary Structures
  145. 145. • U-shaped BurrowsU-shaped Burrows BioturbationBioturbation • Vertical BurrowsVertical Burrows
  146. 146. BioturbationBioturbation • Vertical, dark-colored areas in this rock areVertical, dark-colored areas in this rock are sediment-filled burrowssediment-filled burrows – Could you use burrows such as these to relativelyCould you use burrows such as these to relatively date layers in deformed sedimentary rocks?date layers in deformed sedimentary rocks?
  147. 147. Determining “Up Direction"Determining “Up Direction" • Because the rocks can be overturned by tectonic forces,Because the rocks can be overturned by tectonic forces, what initially appears to be younger because it is on top,what initially appears to be younger because it is on top, may in fact turn out to be at the bottom of the section!may in fact turn out to be at the bottom of the section! • Sedimentary structures can be used to determine "Sedimentary structures can be used to determine "upup directiondirection"" – Graded BedsGraded Beds – Cross BedsCross Beds – MudcracksMudcracks – Flute MarksFlute Marks – Symmetrical (but not Asymmetrical) RipplesSymmetrical (but not Asymmetrical) Ripples – Scour Marks (Sole Marks)Scour Marks (Sole Marks) – StromatolitesStromatolites – BurrowsBurrows – TracksTracks • Features which can be used to determine "up direction"Features which can be used to determine "up direction" are calledare called geopetal structuresgeopetal structures
  148. 148. Figure 5-23 (p. 94)Figure 5-23 (p. 94) Various kinds of geopetal indicatorsVarious kinds of geopetal indicators
  149. 149. Fossils: Evidence of Past LifeFossils: Evidence of Past Life • By definition, fossils are the traces orBy definition, fossils are the traces or remains ofremains of prehistoric lifeprehistoric life nownow preserved in rock.preserved in rock. • Fossils are generally found in sedimentFossils are generally found in sediment oror sedimentary rocksedimentary rock.. – rarely in metamorphic –rarely in metamorphic – destroyeddestroyed – almost never in igneousalmost never in igneous rock – exception tracerock – exception trace fossils of trees infossils of trees in basaltic lava flowsbasaltic lava flows
  150. 150. • Geologically fossils are important forGeologically fossils are important for many reasons:many reasons: Fossils: Evidence of Past LifeFossils: Evidence of Past Life – Aid in interpretation ofAid in interpretation of the geologic past.the geologic past. – Serve as important timeServe as important time indicators.indicators. – Serve as importantServe as important indicators of pastindicators of past environmentalenvironmental conditions.conditions. – Allow for correlation ofAllow for correlation of rocks from differentrocks from different places.places.
  151. 151. Sedimentary FaciesSedimentary Facies
  152. 152. • AA sedimentary faciessedimentary facies is a body ofis a body of sedimentsediment – withwith distinctivedistinctive – physical, chemical, and biological attributesphysical, chemical, and biological attributes – deposited side-by-sidedeposited side-by-side – with other sedimentswith other sediments – inin different environmentsdifferent environments – can be used tocan be used to interpret the depositionalinterpret the depositional environmentenvironment • Every depositional environment puts aEvery depositional environment puts a distinctive imprint on the sediment,distinctive imprint on the sediment, making a particular facies.making a particular facies. Sedimentary FaciesSedimentary Facies
  153. 153. Figure 5-33 (p. 101)Figure 5-33 (p. 101) Sedimentary facies (lithofacies) developed in the seaSedimentary facies (lithofacies) developed in the sea adjacent to a land area.adjacent to a land area. The upper surface of the diagramThe upper surface of the diagram shows present-day facies, whereas the front face showsshows present-day facies, whereas the front face shows the shifting of facies through time. Notice that bottom-the shifting of facies through time. Notice that bottom- dwelling organisms also differ in environments havingdwelling organisms also differ in environments having different bottom sediment and water depth.different bottom sediment and water depth. Each depositional environment grades laterallyEach depositional environment grades laterally into other depositional environments.into other depositional environments.
  154. 154. Virtually all lithostratigraphic units are "Virtually all lithostratigraphic units are "timetime transgressivetransgressive" or" or diachronousdiachronous ((they, orthey, or their contacts,their contacts, cut across time linescut across time lines).). Red Lines G and O are Time LinesRed Lines G and O are Time Lines
  155. 155. Facies and Sea Level ChangesFacies and Sea Level Changes • AA marine transgressionmarine transgression occurs when seaoccurs when sea level rises with respect to the land.level rises with respect to the land. • During a marine transgression,During a marine transgression, – thethe shoreline migrates landwardshoreline migrates landward – and theand the environments paralleling the shorelineenvironments paralleling the shoreline migrate landwardmigrate landward as the sea progressively coversas the sea progressively covers more and more of a continent.more and more of a continent. • Each laterally adjacent depositionalEach laterally adjacent depositional environment produces a sedimentary facies.environment produces a sedimentary facies. • During a transgression, theDuring a transgression, the facies formingfacies forming offshore become superposed upon faciesoffshore become superposed upon facies deposited in nearshore environmentsdeposited in nearshore environments..
  156. 156. Facies and Sea Level ChangesFacies and Sea Level Changes • A transgression produces aA transgression produces a fining-fining- upwardupward ((deepening-upwarddeepening-upward) sequence) sequence of facies.of facies. • Finer-grained (deeper water) faciesFiner-grained (deeper water) facies overlie coarser-grained (shalloweroverlie coarser-grained (shallower water) facies.water) facies. • Sometimes called anSometimes called an onlap sequenceonlap sequence..
  157. 157. • The rocks of each facies becomeThe rocks of each facies become youngeryounger – in a landward directionin a landward direction during a marine transgressionduring a marine transgression • One body of rock with the same attributesOne body of rock with the same attributes – (a facies) was deposited gradually at different times(a facies) was deposited gradually at different times – in different places so it isin different places so it is time transgressivetime transgressive – meaning the ages vary from place to placemeaning the ages vary from place to place Marine TransgressionMarine Transgression OlderOlder ShaleShale YoungerYounger ShaleShale
  158. 158. Sedimentation During a TransgressionSedimentation During a Transgression Produces an Onlap SequenceProduces an Onlap Sequence
  159. 159. • ThreeThree formationsformations depositeddeposited – in ain a widespreadwidespread marinemarine transgressiontransgression – exposed in theexposed in the walls of thewalls of the Grand Canyon,Grand Canyon, ArizonaArizona A Marine Transgression inA Marine Transgression in the Grand Canyonthe Grand Canyon
  160. 160. Causes of TransgressionsCauses of Transgressions 1.1. MeltingMelting of polar ice caps.of polar ice caps. 2.2. DisplacementDisplacement of ocean water byof ocean water by undersea volcanism.undersea volcanism. 3.3. Localized sinking orLocalized sinking or subsidencesubsidence of the land in coastal areas.of the land in coastal areas.
  161. 161. RegressionsRegressions • AA marine regressionmarine regression occurs when sea leveloccurs when sea level rises with respect to the land.rises with respect to the land. • During a marine regression,During a marine regression, – thethe shoreline migrates seawardshoreline migrates seaward – and theand the environments paralleling the shorelineenvironments paralleling the shoreline migrate seawardmigrate seaward as the sea progressivelyas the sea progressively migrates off the continentmigrates off the continent • A regression produces aA regression produces a coarsening upwardcoarsening upward ((shallowing-upwardshallowing-upward) sequence of facies.) sequence of facies. • Coarser-grained (shallower water) faciesCoarser-grained (shallower water) facies overlie finer-grained (deeper water) facies.overlie finer-grained (deeper water) facies. • This is sometimes called anThis is sometimes called an offlap sequenceofflap sequence..
  162. 162. • A marineA marine regressionregression – is the opposite of ais the opposite of a marinemarine transgressiontransgression • It yields a verticalIt yields a vertical sequencesequence – with nearshorewith nearshore facies overlyingfacies overlying offshore faciesoffshore facies – and rock unitsand rock units becomebecome younger inyounger in the seawardthe seaward directiondirection Marine RegressionMarine Regression Younger ShaleYounger Shale OlderOlder ShaleShale
  163. 163. Sedimentation During a RegressionSedimentation During a Regression Produces an Offlap SequenceProduces an Offlap Sequence
  164. 164. Causes of RegressionsCauses of Regressions 1.1. Buildup of ice in theBuildup of ice in the polar ice capspolar ice caps.. 2.2. Formation ofFormation of glaciersglaciers.. 3.3. LocalizedLocalized upliftuplift of the land inof the land in coastal areas.coastal areas.
  165. 165. Sea Level ChangesSea Level Changes • Worldwide sea level change is known asWorldwide sea level change is known as eustaticeustatic seasea levellevel change.change. • Fluctuations in sea level are caused by things such as:Fluctuations in sea level are caused by things such as: • Changes in the size of the polar ice caps, due to climaticChanges in the size of the polar ice caps, due to climatic changes.changes. – Melting of ice caps leads to sea level rise (transgression).Melting of ice caps leads to sea level rise (transgression). – Growth of ice caps and glacier formation leads to drop in seaGrowth of ice caps and glacier formation leads to drop in sea level (regression).level (regression). • Rate of sea floor spreadingRate of sea floor spreading – during times of rapid sea– during times of rapid sea floor spreading and submarine volcanism, the oceanfloor spreading and submarine volcanism, the ocean ridge system is enlarged by the addition of lava,ridge system is enlarged by the addition of lava, displacing water onto the edges of the continentsdisplacing water onto the edges of the continents (transgression).(transgression). • Localized subsidence or uplift of the landLocalized subsidence or uplift of the land – In the 8000 –– In the 8000 – 10,000 years since the melting of the last glacial ice10,000 years since the melting of the last glacial ice sheet over North America, parts of Canada have risensheet over North America, parts of Canada have risen due todue to isostaticisostatic uplift by up to 300 meters.uplift by up to 300 meters.
  166. 166. Isostatic ReboundIsostatic Rebound
  167. 167. The Vail sea-levelThe Vail sea-level curve of majorcurve of major cycles of sea-levelcycles of sea-level changes.changes. The lettersThe letters EE,, MM,, andand LL refer to Early,refer to Early, Middle, and Late.Middle, and Late. ((After Vail, P. R., et al., 1977.After Vail, P. R., et al., 1977. American AssociationAmerican Association of Petroleum Geologistsof Petroleum Geologists Memoir 26Memoir 26.).)
  168. 168. Figure 5-37 (p. 103)Figure 5-37 (p. 103) A rise in sea level will affect a far greater areaA rise in sea level will affect a far greater area along low-lying coastlines than alongalong low-lying coastlines than along coastlines composed of highlands that risecoastlines composed of highlands that rise steeply adjacent to the sea.steeply adjacent to the sea.
  169. 169. The ContinentalThe Continental Shelf andShelf and Coastal PlainCoastal Plain Areas will beAreas will be Most AffectedMost Affected by Sea Levelby Sea Level Rise and FallRise and Fall
  170. 170. What if the ice on Earth melted?What if the ice on Earth melted?
  171. 171. Recent Sea Level CurveRecent Sea Level Curve
  172. 172. Rock UnitsRock Units
  173. 173. Lithostratigraphic UnitLithostratigraphic Unit • A body of sedimentary, extrusive igneous,A body of sedimentary, extrusive igneous, metasedimentary, or metavolcanic rockmetasedimentary, or metavolcanic rock distinguished on the basis of lithologicdistinguished on the basis of lithologic characteristics (texture, color, composition,characteristics (texture, color, composition, etc.) and stratigraphic position.etc.) and stratigraphic position. • GroupGroup – composed of 2 or more formations– composed of 2 or more formations • FormationFormation – composed of 2 or more members– composed of 2 or more members • MemberMember – composed of 2 or more beds– composed of 2 or more beds • BedBed – smallest lithostratigraphic rock unit– smallest lithostratigraphic rock unit
  174. 174. Lithostratigraphic UnitsLithostratigraphic Units • GroupGroup – composed– composed of 2 or more relatedof 2 or more related formationsformations • FormationFormation –– composed of 2 orcomposed of 2 or more membersmore members • MemberMember –– subdivisions withinsubdivisions within formationsformations composed of 2 orcomposed of 2 or more bedsmore beds • BedBed – smallest– smallest lithostratigraphiclithostratigraphic rock unitrock unit
  175. 175. • Lithologically homogeneousLithologically homogeneous – all beds are– all beds are the same rock type or a distinctive set ofthe same rock type or a distinctive set of interbedded rock types.interbedded rock types. • Distinct and different from adjacent rockDistinct and different from adjacent rock unitsunits above and below.above and below. • Traceable from exposure to exposureTraceable from exposure to exposure ((correlationcorrelation)), and of, and of sufficient thickness tosufficient thickness to be mappablebe mappable.. • Named for a geographic localityNamed for a geographic locality wherewhere particularly well exposed (This locality isparticularly well exposed (This locality is referred to as the type section.) If the bedsreferred to as the type section.) If the beds are dominated by a single rock type, thisare dominated by a single rock type, this may appear in the name.may appear in the name. Lithostratigraphic UnitsLithostratigraphic Units
  176. 176. CorrelationCorrelation • Correlation of rock units from one areaCorrelation of rock units from one area to another is known asto another is known as stratigraphystratigraphy.. – Lithostratigraphic CorrelationLithostratigraphic Correlation – Matching– Matching up rock units on the basis of lithology andup rock units on the basis of lithology and stratigraphic position.stratigraphic position. – Biostratigraphic CorrelationBiostratigraphic Correlation – Matching up– Matching up rock units on the basis of fossils theyrock units on the basis of fossils they contain.contain. – Chronostratigraphic CorrelationChronostratigraphic Correlation –– Matching up rock units on the basis of ageMatching up rock units on the basis of age equivalence, as determined by radioactiveequivalence, as determined by radioactive dating methods or fossils.dating methods or fossils.
  177. 177. Figure 5-44 (p. 108)Figure 5-44 (p. 108) Correlation of lowerCorrelation of lower Cambrian rock units inCambrian rock units in western Montana.western Montana. The lettersThe letters CC,, BB,, GG, and, and AA indicate the occurrences ofindicate the occurrences of trilobite index fossilstrilobite index fossils CedariaCedaria,, BathyuriscusBathyuriscus,, GlossopleuraGlossopleura, and, and AlbertellaAlbertella.. ((Modified from Schmidt et al. 1994. U.S.Modified from Schmidt et al. 1994. U.S. Geological Survey Bulletin 2045Geological Survey Bulletin 2045.).)
  178. 178. Figure 5-38 (p. 105)Figure 5-38 (p. 105) If the lithology of a rock is not sufficiently distinctive to permit itsIf the lithology of a rock is not sufficiently distinctive to permit its lithostratigraphic correlationlithostratigraphic correlation from one locality to another, its positionfrom one locality to another, its position in relation to distinctive rock units above and below may aid inin relation to distinctive rock units above and below may aid in correlation.correlation. In the sample shown here, the limestone unit at localityIn the sample shown here, the limestone unit at locality AA cancan be correlated with the lowest of the four limestone units at localitybe correlated with the lowest of the four limestone units at locality BB because of its position between the gray shale and the sandstone units.because of its position between the gray shale and the sandstone units.
  179. 179. Geologic MapsGeologic Maps
  180. 180. Depicting the PastDepicting the Past Various ways in which the distribution ofVarious ways in which the distribution of rocks can be depicted:rocks can be depicted: • Geologic columnsGeologic columns • Stratigraphic cross-sectionsStratigraphic cross-sections • Structural cross-sectionsStructural cross-sections • Geologic mapsGeologic maps • Paleogeographic mapsPaleogeographic maps • Isopach mapsIsopach maps • Lithofacies mapsLithofacies maps
  181. 181. Geologic ColumnsGeologic Columns • Geologic ColumnsGeologic Columns show the verticalshow the vertical succession of rocksuccession of rock units at a givenunits at a given location. They arelocation. They are used in correlationused in correlation and in theand in the construction of cross-construction of cross- sectionssections
  182. 182. GeneralizedGeneralized GeologicGeologic Column forColumn for Grand CanyonGrand Canyon National ParkNational Park.. ((From McKee, E. D.From McKee, E. D. 1982. The Supai Group1982. The Supai Group of the Grand Canyon,of the Grand Canyon, U.S. Geological SurveyU.S. Geological Survey Professional PaperProfessional Paper 11731173.).)
  183. 183. Stratigraphic Cross-SectionsStratigraphic Cross-Sections • StratigraphicStratigraphic Cross-SectionsCross-Sections correlatecorrelate geologicgeologic columns fromcolumns from differentdifferent locations tolocations to show how rockshow how rock units change inunits change in thickness,thickness, lithology, andlithology, and fossil contentfossil content in a given areain a given area
  184. 184. Structural Cross-SectionsStructural Cross-Sections • Structural Cross-SectionsStructural Cross-Sections show a slice through theshow a slice through the Earth's crust, and may be drawn to emphasize theEarth's crust, and may be drawn to emphasize the lithologic equivalence of the strata.lithologic equivalence of the strata. • They illustrate theThey illustrate the timing of tiltingtiming of tilting,, foldingfolding, and, and faultingfaulting of rock units. Tops and bottoms of rock unitsof rock units. Tops and bottoms of rock units are plotted by elevation. Folds and faults are depictedare plotted by elevation. Folds and faults are depicted clearly.clearly.
  185. 185. GeologicGeologic MapsMaps • Geologic MapsGeologic Maps showshow the distribution ofthe distribution of various layers andvarious layers and types of rocks in antypes of rocks in an area.area. • Geologic maps areGeologic maps are prepared by geologistsprepared by geologists who locate thewho locate the positions of contactspositions of contacts between formations inbetween formations in the field, and plot themthe field, and plot them on a map.on a map. • Map symbols indicateMap symbols indicate structural featuresstructural features (folds, faults, etc.) and(folds, faults, etc.) and formation names.formation names.
  186. 186. Figure 5-46 (p. 109)Figure 5-46 (p. 109) Steps in the preparation of a geologic map.Steps in the preparation of a geologic map. ((AA) A suitable base map is selected.) A suitable base map is selected. ((BB) The locations of rock exposures of the) The locations of rock exposures of the various formations are then plotted on the basevarious formations are then plotted on the base map. Special attention is given to exposuresmap. Special attention is given to exposures that include contacts between formations;that include contacts between formations; where they can be followed horizontally, theywhere they can be followed horizontally, they are traced onto the base map also. Strike (theare traced onto the base map also. Strike (the compass direction of a line formed by thecompass direction of a line formed by the intersection of the surface of a bed and aintersection of the surface of a bed and a horizontal plane) and dip (the angle an inclinedhorizontal plane) and dip (the angle an inclined stratum makes with the horizontal) arestratum makes with the horizontal) are measured wherever possible and added to themeasured wherever possible and added to the data on the base map. After careful field studydata on the base map. After careful field study and synthesis of all the available information,and synthesis of all the available information, formation boundaries are drawn to best fit theformation boundaries are drawn to best fit the data.data. ((CC) On the completed map, color patterns are) On the completed map, color patterns are used to show the areal pattern of rocksused to show the areal pattern of rocks beneath the cover of soil.beneath the cover of soil. ((DD) A cross-section is shown along line A-A9.) A cross-section is shown along line A-A9. ((EE) A block diagram illustrates strike and dip.) A block diagram illustrates strike and dip.
  187. 187. Paleogeographic MapsPaleogeographic Maps • PaleogeographicPaleogeographic MapsMaps areare interpretive mapsinterpretive maps which depict thewhich depict the geography of angeography of an area at some timearea at some time in the past, forin the past, for example, mapsexample, maps showing theshowing the distribution ofdistribution of land and sea inland and sea in the past.the past.
  188. 188. PaleogeographicPaleogeographic MapsMaps • Figure 5-48 (p. 110) • Constructing a Paleogeographic Map: (1) For the selected area, collect all available data that show the occurrence of the selected time-rock unit. Plot every point where rocks appear for that time period. (2) Plot the rock types observed on that time-rock unit. Determine whether the strata originated on land or in the sea. (3) Draw the paleogeographic map.
  189. 189. Isopach MapsIsopach Maps • Isopach MapsIsopach Maps show the thickness ofshow the thickness of formations or other units in an area.formations or other units in an area.
  190. 190. Figure 5-49 (p.111)Figure 5-49 (p.111) Isopach map ofIsopach map of Upper OrdovicianUpper Ordovician formations informations in Pennsylvania andPennsylvania and adjoining states.adjoining states. ((After Kay, M. 1951.After Kay, M. 1951. Geological Society ofGeological Society of America Memoir No.America Memoir No. 4848.).) IsopachIsopach MapsMaps
  191. 191. Lithofacies MapsLithofacies Maps • Lithofacies MapsLithofacies Maps show the distribution of lithofaciesshow the distribution of lithofacies that existed at a given time over an area, or show thethat existed at a given time over an area, or show the percentage of some lithologic component (such aspercentage of some lithologic component (such as clay), or show the ratio of one rock type to anotherclay), or show the ratio of one rock type to another within the unit.within the unit.
  192. 192. Figure 5-52 (p. 112)Figure 5-52 (p. 112) Lithofacies map of Lower Silurian rocks in the easternLithofacies map of Lower Silurian rocks in the eastern United States.United States. ((After Amsden, T. W. 1955. Bull Am Assoc Petrol Geol 39:60–74After Amsden, T. W. 1955. Bull Am Assoc Petrol Geol 39:60–74.).)

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