11Mesozoic Earth History - CCSF€¦ · 9 Mesozoic History of North America {Early Triassic – Same as Permian – connected to Pangea zEast Appalacian Mountain Belt zWest Cordilleran
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Mesozoic Earth History
The Mesozoic Era 251-66 MYA
Breakup of PangeaChanges in air and oceanic currentsEvolution of new terrestrial and marine lifeOpening of the Atlantic Ocean BasinRocky MountainsSalt depositsBatholiths with ore deposits
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Breakup of Pangea
Rifting between Laurasia and Gondwanda – TriassicRifting of North America from South America – Late Triassic –JurassicAustralia/Antarctica separate from South America/Africa – Late Triassic-JurassicIndia separates from Gondwana –Late Triassic-Jurassic
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Breakup of Pangea - continued
South America separates from Africa – Jurassic - CretaceousAustralia and Antarctica split –CretaceousIndia travels to Equator -CretaceousGreenland becomes independent landmass – Cretaceous - Cenozoic
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Evaporite Deposits form in early Mesozoic
Narrow basins
Near Equator
High heat flow
Oceans and Seaways
Tethys Ocean begins to close in Jurassic – continues through CretaceousAtlantic Ocean opens - Cretaceous
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Effects of Pangea Breakup on Global Climate Patterns
Pangea was mostly aridLarge continental land massSurrounded by mountain rangesEvidence = evaporites, sand dunes and red beds
Some humid regions in Triassic;Evidence= coal deposits
High latitudes like Scottish peat bogsSome humid regions around Tethys seaway as it opened (warm, monsoons)
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Permian – Guadalupe Mountains
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Permian Guadalupe Mtns
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Triassic Marginal Marine
Coal
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Effects of Pangea Breakup on Global Climate Patterns and Ocean Circulation
Temperature gradientDifference in temperature between poles and tropicsAffects speed of atmospheric and oceanic circulation (steeper gradient, faster circulation)Oceans absorb 90% sun’s heat; continents only 50% or lessOcean dominated = warmer
Effects of Pangea Breakup on Global Climate Patterns and Ocean Circulation
Steeper thermal gradient as continents moved northwardOceans and atmosphere accelerated circulationSeasonality increases on landWarm water from Tethys circulation kept climate equable worldwide through CretaceousIn general, circulation patterns more complex as Mesozoic progressed.
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Mesozoic History of North America
Early Triassic – Same as Permian – connected to Pangea
East Appalacian Mountain BeltWest Cordilleran mobile beltSuturing of volcanic island arc –Sonoma orogeny
Late Triassic – JurassicN. America begins to separate from AfricaFault block and igneous activity in AppalaciansN. America separates from South AmericaGulf of Mexico fills with evaporitesMajor Mountain building resulting in Sierra Nevada and Rocky Mountains – Cordilleran orogeny
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Mesozoic History of North America
Cretaceous rise of sea levelMarine deposition over most of N. American CordilleranAbsaroka Sequence; Zuni Sequence
Regional Mesozoic History – Eastern North America
Early Triassic – Uplifted Appalacians erode to low hillsLate Triassic – uplift and fault block basins from rifting (breakup of Pangea)
Deposition in non-marine basins of Newark Group –many dinosaur footprintsIgneous activity – lava flows and intrusions
Palasades sill
Jurassic and Early Cretaceous – ErosionCretaceous –Re-elevation of Appalacians; creation of Atlantic Coastal plain sediments
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Association of Rifting with Normal Faults
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Palasades Sill
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Regional Mesozoic History – Gulf Coastal Region
Late Triassic-Early Jurassic Gulf began as N. America separated from S. America
Shallow, restricted basinFilled with evaporitesLater associated with petroleum accumulation
Late Jurassic – normal marineTransgression and regressionDeep sedimentary pile
Cretaceous seaway to Arctic OceanExtensive reefs composed of bivalve, rudists – became reservoirs for oil
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Regional Mesozoic History – Western Region
Permian-TriassicWestern island arc formedSubduction of oceanic plate beneath island arcThrusting of Island arc eastward against craton = Sonoma OrogenySuturing of island arc terrane to western edge of N. America
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Regional Mesozoic History – Western Region
Late TriassicSubduction Zone to the west where N. America overrides Farallon Plate
Middle to Late JurassicTwo subduction zones dipping in opposite directionsN. America overrides Farallon Plate eliminating the westward subductionzone
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Regional Mesozoic History – Western Region
Late Jurassic – CenozoicFranciscan Complex
Chaotic mixture of rock typesRepresent continental shelf, slope, deep-sea environment rocks all brought together in a trench, partly subducted, then squeezed against N. America
Great Valley GroupSedimentary rocks of the Continental shelf, slope collecting at same time as FranciscanNow in thrust fault relationship with Franciscan
Franciscan Formation/Group
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Great Valley Group
Thin turbidites of Great Valley Group
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Regional Mesozoic History – Western Region
Orogenies of the Western RegionNevadan
Granitic masses beneath N. America became the batholiths of the Sierra Nevada, Southern California, Idaho, and Coast RangeContemporaneous with Franciscan/Great ValleyChange from high angle to low angle subduction moved plutonism and volcanism to the east
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Orogenies of the Western Region
Sevier OrogenyNumerous overlapping thrust faultsMoved blocks of older strata over youngerMountains of Montana to Western Canada
Laramide OrogenyDeveloped east of the SevierRocky Mountains – mostly Cenozoic
Mesozoic Sedimentation
Triassic of the western continental shelf
Shallow marine sandstone, shale and limestoneRegression to erosion and red beds
Moenkopi Formation –tracks and fossil amphibians and reptilesShinarump conglomerateChinle Formation – petrified forest and fossil amphibians, phytosaurs, small dinosaurs
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Mesozoic Sedimentation
JurassicCross-bedded sandstones from dunesWingate SandstoneNavajo Sandstone – prominentSundance Sea produced Sundance FormationMountain building shed sediments eastward and Sundance Sea northwardMorrison Formation - Dinosaurs
Mesozoic Sedimentation
CretaceousEarly to mid-Cretaceous transgression led to mid continental seawayBlack ShalesSevier orogenic belt fed sediments to interiorAs regression took place coal bodies formed
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Accretion of Terranes
TerranesSmall accreted lithospheric blocks that are clearly of foreign originDiffer from surrounding blocks and cratons
Fossil contentStructural trendsStratigraphyPaleomagnetic properties
Almost certainly of foreign origin carried for many miles as continental or other plate fragments
Terranes
Composed of Volcanic island arcsOceanic ridge fragments (ophiolites)SeamountsHot spot tracksFragments of continents
ExamplesWrangellia terranes (continent)Klamath Mountains (island arc)
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Mesozoic Mineral Resources
Coal – Rocky Mtns.Petroleum of Persian Gulf and Gulf of MexicoUranium of Mid Continent N. AmericaDiamonds of S. AfricaGold of the Mother LodeCopper of N. and S. America
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