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. 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. The Rock CycleThe Rock Cycle
• SedimentarySedimentary
Rocks areRocks are
formed fromformed from
sediments.sediments.
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. 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. 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. 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).
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..
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. 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. • 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. 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)
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
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. 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. 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
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. 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. 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.
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. 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. • 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. 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.
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. Gravel Sized Detrital RocksGravel Sized Detrital Rocks
(Subdivided Based on Grain Roundness)(Subdivided Based on Grain Roundness)
BrecciaBreccia
ConglomerateConglomerate
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
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. 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. 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. 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
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. 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. 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. 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. 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. 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. 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.
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. Sandstone Close-UpsSandstone Close-Ups
• Quartz Sandstone (left)Quartz Sandstone (left)
• Arkose (Sandstone with >10% feldspar)Arkose (Sandstone with >10% feldspar)
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. 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.
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..
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
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. 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. 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. 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. 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. 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. 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..
74. El CapitanEl Capitan
Peak inPeak in
GuadalupeGuadalupe
NationalNational
Park, Texas -Park, Texas -
ExposedExposed
Permian-Permian-
agedaged
MassiveMassive
Coral ReefCoral Reef
ComplexComplex
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. • 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. 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. 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.
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. • 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. • 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. 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. • 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. 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. 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. • 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. 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. 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. 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)
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
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. • 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
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
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. 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. 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. 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. 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).
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. 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. 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
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
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
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.
123. 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
124. 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
126. • 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
127. 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.
128. • 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
129. • 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
132. • 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
135. • 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
137. 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
138. • 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
139. • 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
141. • 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
142. • 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
143. • 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
144. 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
145. • 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
147. 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?
148. 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
149. Figure 5-23 (p. 94)Figure 5-23 (p. 94)
Various kinds of geopetal indicatorsVarious kinds of geopetal indicators
150. 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
151. • 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.
153. • 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
154. 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.
155. 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
156. 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..
157. 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..
158. • 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
159. Sedimentation During a TransgressionSedimentation During a Transgression
Produces an Onlap SequenceProduces an Onlap Sequence
160. • 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
161. 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.
162. 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..
163. • 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
164. Sedimentation During a RegressionSedimentation During a Regression
Produces an Offlap SequenceProduces an Offlap Sequence
165. 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.
166. 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.
168. 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.).)
169. 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.
170. 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
171. What if the ice on Earth melted?What if the ice on Earth melted?
174. 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
175. 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
176. • 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
177. 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.
178. 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.).)
179. 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.
181. 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
182. 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
183. 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.).)
184. 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
185. 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.
186. 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.
187. 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.
188. 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.
189. 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.
190. 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.
191. 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
192. 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.
193. 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.).)
Editor's Notes
Have Students separate Detrital from Chemical Rocks.
Have Students determine Grain-Size.
Have Students determine Degree of Sorting.
Have Students determine Degree of Rounding.
Have Students determine Grain-Size, Degree of Sorting, Degree of Rounding, Distance from Source, Deposition Rate, Lithification Mechanism, and Degree of Chemical Weathering for fine-grained and course-grained rocks (shales, siltstones, conglomerates).
What sedimentary textures does this rock exhibit?
What is the composition of this rock?
What do these observations tell you about the formation of this rock?
What sedimentary textures does this rock exhibit?
What is the composition of this rock?
What do these observations tell you about the formation of this rock?
Have Students determine Detrital Sedimentary Rock Names, Distance from Source, Deposition Rate, Degree of Chemical Weathering of sandstones, Media of Deposition, and Environments of Deposition (as possible thus far).
Have Students separate Carbonates from other Chemical sedimentary rocks.
Have Students separate Clastic from Non-Clastic textures within each group.
Classes of limestone: one that forms from big bugs and the other from little bugs
Classes of limestone: one that forms from big bugs and the other from little bugs
Have Students determine Carbonate Sedimentary Rock Names, Source Material, Media of Deposition, and Environments of Deposition.
Why are the Salt Flats so flat?
Have Students determine non-carbonate Chemical Sedimentary Rock Names, Source Material, Media of Deposition, and Environments of Deposition.
Marine Depositional Environments
Shallow (up to about 200 meters depth)
Land-derived detrital sediments deposited on the continental shelf (coarser-grained – sands, silts, and clays forming pebble conglomerates, sandstones, siltstones, mudstones, and shales).
Organic Limestones – Fossiliferous Limestones, Oolitic Limestones, Coral Reef Limestones, and Coquina
Evaporites in enclosed seas
Deep (seaward of continental shelves)
Deep-sea sediments – fine-grained detrital sediments (silts and clays forming siltstones, musdtones, and shales) 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).
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)
Get Animation of Cross-Bedding Formation
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