Mesozoic EraMesozoic Era

GeologyGeology

Phanerozoic EonPhanerozoic EonMesozoic EraMesozoic Era

• 3 periods3 periods• Age of ReptilesAge of Reptiles

– TriassicTriassic– JurassicJurassic– CretaceousCretaceous

MesozoicMesozoicOverviewOverview

• GlobalGlobal– Breakup of PangaeaBreakup of Pangaea

• North AmericaNorth America– CordilleranCordilleran

– Eastern Coastal RegionEastern Coastal Region

Subduction zone after N.A. Subduction zone after N.A. moves westmoves west

Cordilleran OrogenyCordilleran Orogeny

Fault block mountainsFault block mountains

MesozoicMesozoicPangaea BreakupPangaea Breakup

• Greatly influenced geology/biology/climateGreatly influenced geology/biology/climate

• Fracturing of continentsFracturing of continents

i.e. S. Africa Rifti.e. S. Africa Rift

– Associated with extensionAssociated with extension

– Triple junctionTriple junction

Mantle plume = bulgeMantle plume = bulge

2 arms join in fracturing2 arms join in fracturing

33rdrd failed arm = aulacogen failed arm = aulacogen

(Niger, Miss, Amazon)(Niger, Miss, Amazon)

Continental Drift Continental Drift Geographic FitGeographic Fit

• Continents seem to fit together like pieces of a puzzleContinents seem to fit together like pieces of a puzzle

Mesozoic PaleogeographyMesozoic PaleogeographyTriassicTriassic

• Laurasia and Gondwana Laurasia and Gondwana (L. Tr)(L. Tr)– N. America from S. America and Africa (L. Tr-E. Jr)N. America from S. America and Africa (L. Tr-E. Jr)– Tethys to AtlanticTethys to Atlantic

– Note location along equatorNote location along equator

Mesozoic PaleogeographyMesozoic PaleogeographyJurassicJurassic

• Fragmentation of Gondwana Fragmentation of Gondwana (L. Tr & Jr)(L. Tr & Jr)

– Antarctica and Australia break off (L. Tr)Antarctica and Australia break off (L. Tr)

– India splits and moves northIndia splits and moves north

Pangaea RiftingPangaea RiftingJurassicJurassic

• Thick evaporitesThick evaporites

Mesozoic PaleogeographyMesozoic PaleogeographyCretaceousCretaceous

• S. America from Africa S. America from Africa (begin L. Jr)(begin L. Jr)– E. Tethys closes; Mediterranean prototype formsE. Tethys closes; Mediterranean prototype forms

– Australia and Antarctica separate (end of K)Australia and Antarctica separate (end of K)

– India moves northwardIndia moves northward

– K transgressionK transgression

Mesozoic Ocean CirculationMesozoic Ocean CirculationTriassic to CretaceousTriassic to Cretaceous

• Evolution of oceanic circulationEvolution of oceanic circulation– Simple pattern in a single oceanSimple pattern in a single ocean– Complex in newly formed oceansComplex in newly formed oceans

N.A. PaleogeographyN.A. PaleogeographyContinental InteriorContinental Interior

• Mostly above water; no epeiric seasMostly above water; no epeiric seas• See only Zuni (E. Jr-Paleo) & Absaroka See only Zuni (E. Jr-Paleo) & Absaroka

sequencessequences

N.A. PaleogeographyN.A. PaleogeographyEastern Coastal RegionEastern Coastal Region

• Alleghenian orogeny uplifted Alleghenian orogeny uplifted AppalachiansAppalachians

• Erosion = coarse sedimentsErosion = coarse sediments

• Pangaea rifting = fault block Pangaea rifting = fault block basinsbasins

– Newark group (6000m), poorly Newark group (6000m), poorly sorted, non-marine (L. Tr-E. Jr)sorted, non-marine (L. Tr-E. Jr)

– Reptilian footprints Reptilian footprints no dinos no dinos

– Dikes & sills (Palisades)Dikes & sills (Palisades)– After rifting = passive marginAfter rifting = passive margin

Uplifted mtns. planed offUplifted mtns. planed off

– K = Appalachians upliftedK = Appalachians uplifted

N.AN.A. . PaleogeographyPaleogeographyGulf CoastGulf Coast

• N. America and S. America N. America and S. America get evaporites (L. Tr)get evaporites (L. Tr)

• Form salt domes; no Form salt domes; no evaporites (L. Jr)evaporites (L. Jr)

• Transgressive/regressive Transgressive/regressive sea, i.e. shale, LS, sea, i.e. shale, LS, sandstonesandstone

• End of K transgressionsEnd of K transgressions

• K reefs commonK reefs common

Western N.A. PaleographyWestern N.A. Paleography• Permian arc like Japanese arcPermian arc like Japanese arc

– Subduction, get arc and oceanic arc plastered to continentSubduction, get arc and oceanic arc plastered to continent

– Produce Sonoma OrogenyProduce Sonoma Orogeny

– Steep subduction (L. Tr)Steep subduction (L. Tr)

• Oc-Cont convergence, i.e. S. America after orogenyOc-Cont convergence, i.e. S. America after orogeny

– Oc-Cont convergence control Meso and Ceno tectonicsOc-Cont convergence control Meso and Ceno tectonics– Modern Circum-Pacific orogenic system bornModern Circum-Pacific orogenic system born

Western N.A. PaleographyWestern N.A. PaleographyTriassicTriassic

• Shallow – ss-sh-lsShallow – ss-sh-ls• Regression followedRegression followed

– Marginal marine & non-marineMarginal marine & non-marine Red beds (L. Tr)Red beds (L. Tr)

• Moenkopi Moenkopi (L. Tr)(L. Tr)

• ShinarumpShinarump

• Chinle Chinle (U. Tr)(U. Tr)

– MS, tracks-streams, flood plainsMS, tracks-streams, flood plains– Local marine = lsLocal marine = ls

– Unconformably overlies MoenkopiUnconformably overlies Moenkopi– Erosion of exposed AZ, CO, IDErosion of exposed AZ, CO, ID

– Sh, siltst, - petrified forestSh, siltst, - petrified forest– Ash provides silicaAsh provides silica– Amphibians, small dinosAmphibians, small dinos

Western North AmericaWestern North AmericaTectonic EvolutionTectonic Evolution

• 2 opposite-dipping SZ2 opposite-dipping SZ– Franciscan deposition – trench (M.–L. Jr)Franciscan deposition – trench (M.–L. Jr)

– Up to 7000 mUp to 7000 m

– Greywacke, chert, sh, brecciaGreywacke, chert, sh, breccia

– BlueschistBlueschist

Western North AmericaWestern North AmericaFranciscanFranciscan

• Reconstruction of the depositional environment of the Reconstruction of the depositional environment of the Franciscan GroupFranciscan Group

Western North AmericaWestern North AmericaTectonic EvolutionTectonic Evolution

• Great Valley GroupGreat Valley Group

– Shelf and slope depositionShelf and slope deposition

– Forearc basinForearc basin

Western North AmericaWestern North AmericaTectonic EvolutionTectonic Evolution

• Cordilleran OrogenyCordilleran Orogeny– Several phasesSeveral phases Nevada Orogeny – huge batholiths (L. Jr-K)Nevada Orogeny – huge batholiths (L. Jr-K) Sevier Orogeny – Pacific Plate subducted (K)Sevier Orogeny – Pacific Plate subducted (K) Laramid Orogeny – anticlines & dunes (L. K)Laramid Orogeny – anticlines & dunes (L. K)

Western N.AmericaWestern N.AmericaCause of MigrationCause of Migration

• As subducting plate moved at a lower angle, the As subducting plate moved at a lower angle, the depth of melting moved to eastdepth of melting moved to east

Western N.A. PaleogeographyWestern N.A. PaleogeographyJurassic &Jurassic & CretaceousCretaceous

Jurassic Navajo SS, ZionJurassic Navajo SS, Zion

• Clean, x-bedded SS Clean, x-bedded SS (M. Jr)(M. Jr)

• Nevadan orogenyNevadan orogeny

• Cretaceous interior Cretaceous interior seawayseaway

– Marine, Sundance Sea Marine, Sundance Sea

– Stream, lake depositsStream, lake deposits

– Ms, sh = MorrisonMs, sh = Morrison

– Dinos (Jr)Dinos (Jr)

– Big inland sea – Gulf to Arctic Big inland sea – Gulf to Arctic

– Accelerated spreading Accelerated spreading

Western North AmericaWestern North AmericaMicroplatesMicroplates

• >25% from accretion of microplates>25% from accretion of microplates

– Material added to continentsMaterial added to continents

– Different in fossils, stratigraphy, structure, Different in fossils, stratigraphy, structure, paleomagnetismpaleomagnetism

– Formed elsewhere, transported along faultsFormed elsewhere, transported along faults