[p.T] Stratigraphy Geologic Time
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Transcript of [p.T] Stratigraphy Geologic Time
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STRATIGRAPHY&GEOLOGICTIME
Stratigraphy:Studyofthelayersofsedimentaryrocks
Unconformities Correlation GeologicTime
Scale
Sedimentation inlake or sea
Sediments are deposited in horizontallayers and slowly change into rock.
StratigraphicPrincipalofOriginal
Horizontality
Sedimentarylayersareoriginallydepositedas.
Foldedortiltedbedsindicatessomethinghappenedtothemlater
TIME 1Beneath the sea, D
sedimentsaccumulated in beds. B
C
A
StratigraphicPrincipalof
Superposition
SedimentarylayersatthebottomofasequenceofbedsareOLDERthantheonesontop
Ifolderbedsareontop,thenthesequencehasbeenturnedupsidedown
Younger
Older
PrincipleofSuperposition
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Stratigraphic Principal ofCross-Cutting Relations
Any rock or structure that cutsacross another rock is younger thatthe rock it cuts across.
Unconformity=
surface
of
nondepositionorerosion
Tapeats Sandstone (ca.500 million years)
Angular Unconformity
Beds below the unconformitysurface are at an angle to the bedsoverlying the surface
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Angularunconformity Unconformitywherebedsbelowareatanangletobeds
above
Nonconformity
Unconformity wherebeds overliemetamorphic origneous rocks
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Angularunconformity Unconformitywherebedsbelowareatanangletobeds
above
TIME 1Beneath the sea,
sediments Daccumulated in beds.
B
C
A
TIME 2Tectonic forcescaused uplift,
C
D
to erosion.
B
A
Uplift
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TIME 3 C
Erosion strippedaway bed D andpart of C.
B
A
DisconformitySurface between horizontal strata wheremajor erosion or non-deposition occurred
Subsidenceallowed a newlayer, E, to bedeposited.
B
C
A
E
Subsidence
Unconformity
10 cm
TIME 1Beneath the seasedimentsaccumulated in beds.
Compression
TIME 2Tectonic forces causeduplift, folding, anddeformation.
Uplift
TIME 3Erosion stripped away
layers, leavingportions of severallayers exposed.
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TIME 4Subsidenceallowed new
sediments to bedeposited.
An ular
Subsidence
unconformity
Write down thesequence of events forthis location. There areat least 5.
1. Deposition of redsiltstone sediment
2. Lithification ofsediments
3.4.5.
1. Deposition ofsediment
2. Compaction/cement= sedimentary rock
3. Folding (syncline)4. Erosion -angular
unconformity
5. Deposition ofsediment on top
Plants grow on this
surface
StratigraphicPrincipalof
FaunalSuccession
Fossilspeciesappearanddisappearina
.
ThissequencecanbeusedtoCORRELATEbedsinoneareatoanotherarea.
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Outcrop A Outcrop B
III
II
III
Outcrop A Outcrop B
III
II
III
Outcrop A Outcrop B
III
II
III
Outcrop A Outcrop B
III
Some of the fossils found inoutcrop A are the same asfossils found in outcrop B,some distance away.
II
III
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Outcrop A Outcrop B
III
Some of the fossils found inoutcrop A are the same asfossils found in outcrop B,some distance away.
II
III
Layers with thesame fossils arethe same age.
Outcrop A Outcrop B
III
Some of the fossils found inoutcrop A are the same asfossils found in outcrop B,some distance away.
II
III
Layers with thesame fossils arethe same age.
Younger rocks
I
II
A composite of the tw o outcrops.
Older rocks
III
TheAgeoftheEarth
4,560,000,000 years
or 4.6 billion years
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GeologicTimeScale
Precambrian(4.6Gato540Ma)
Paleozoic(540Mato250Ma)
Triassic
Jurassic
Cretaceous
Cenozoic(65Matothepresent)
LIFEONEARTH
3.5billion
year
old
bacteria
andal ae
PaleozoicEra
Cambrianexplosionoflife:
540millionyearsago
TrilobitesPaleozoicarthropods
Today: 80% of species are arthropods
anotherTrilobite Crinoids
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First land
animals:365 Ma
Dimetrodon Permianreptile
EndofthePaleozoic
Major extinction event:96% of marine life was killed70% land vertebrates killed
EndofthePaleozoic
MesozoicEraAmmonites MesozoicEraAmmonites
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MesozoicEraTriceratops
MesozoicEra
CretaceousPeriod
Tyrannosaurus
Rex
EndoftheMesozoic
Ma or extinction event:85% of all species died.
CenozoicMammoth
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CenozoicSabretoothtiger
EndoftheCenozoic?
Supervolcano eruption
SupernovaMeteorite im act
Nuclear warEpidemic
Global warming...