Mesozoic Era Geology

Phanerozoic Eon Mesozoic Era 3 periods3 periods Age of ReptilesAge of Reptiles – Triassic – Jurassic – Cretaceous

Mesozoic Overview GlobalGlobal – Breakup of Pangaea North AmericaNorth America – Cordilleran – Eastern Coastal Region  Subduction zone after N.A. moves west  Cordilleran Orogeny  Fault block mountains

Mesozoic Pangaea Breakup Greatly influenced geology/biology/climateGreatly influenced geology/biology/climate Fracturing of continentsFracturing of continents i.e. S. Africa Rift – Associated with extension – Triple junction  Mantle plume = bulge  2 arms join in fracturing  3 rd failed arm = aulacogen (Niger, Miss, Amazon) (Niger, Miss, Amazon)

Continental Drift Geographic Fit Continents seem to fit together like pieces of a puzzle

Mesozoic Paleogeography Triassic Laurasia and Gondwana (L. Tr)Laurasia and Gondwana (L. Tr) – N. America from S. America and Africa (L. Tr-E. Jr) – Tethys to Atlantic – Note location along equator

Mesozoic Paleogeography Jurassic Fragmentation of Gondwana (L. Tr & Jr)Fragmentation of Gondwana (L. Tr & Jr) – Antarctica and Australia break off (L. Tr) – India splits and moves north

Pangaea Rifting Jurassic Thick evaporitesThick evaporites

Mesozoic Paleogeography Cretaceous S. America from Africa (begin L. Jr)S. America from Africa (begin L. Jr) – E. Tethys closes; Mediterranean prototype forms – Australia and Antarctica separate (end of K) – India moves northward – K transgression

Mesozoic Ocean Circulation Triassic to Cretaceous Evolution of oceanic circulationEvolution of oceanic circulation – Simple pattern in a single ocean – Complex in newly formed oceans

N.A. Paleogeography Continental Interior Mostly above water; no epeiric seasMostly above water; no epeiric seas See only Zuni (E. Jr-Paleo) & Absaroka sequencesSee only Zuni (E. Jr-Paleo) & Absaroka sequences

N.A. Paleogeography Eastern Coastal Region Alleghenian orogeny uplifted AppalachiansAlleghenian orogeny uplifted Appalachians Erosion = coarse sedimentsErosion = coarse sediments Pangaea rifting = fault block basinsPangaea rifting = fault block basins – Newark group (6000m), poorly sorted, non-marine (L. Tr-E. Jr) – Reptilian footprints  no dinos – Dikes & sills (Palisades) – After rifting = passive margin  Uplifted mtns. planed off – K = Appalachians uplifted

N.A. Paleogeography Gulf Coast N. America and S. America get evaporites (L. Tr)N. America and S. America get evaporites (L. Tr) Form salt domes; no evaporites (L. Jr)Form salt domes; no evaporites (L. Jr) Transgressive/regressive sea, i.e. shale, LS, sandstoneTransgressive/regressive sea, i.e. shale, LS, sandstone End of K transgressionsEnd of K transgressions K reefs commonK reefs common

Western N.A. Paleography Permian arc like Japanese arcPermian arc like Japanese arc – Subduction, get arc and oceanic arc plastered to continent – Produce Sonoma Orogeny – 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 tectonics – Modern Circum-Pacific orogenic system born

Western N.A. Paleography Triassic Shallow – ss-sh-lsShallow – ss-sh-ls Regression followedRegression followed – Marginal marine & non-marine  Red beds (L. Tr) Moenkopi (L. Tr)Moenkopi (L. Tr) ShinarumpShinarump Chinle (U. Tr)Chinle (U. Tr) – MS, tracks-streams, flood plains – Local marine = ls – Unconformably overlies Moenkopi – Erosion of exposed AZ, CO, ID – Sh, siltst, - petrified forest – Ash provides silica – Amphibians, small dinos

Western North America Tectonic Evolution 2 opposite-dipping SZ2 opposite-dipping SZ – Franciscan deposition – trench (M.–L. Jr) – Up to 7000 m – Greywacke, chert, sh, breccia – Blueschist

Western North America Franciscan Reconstruction of the depositional environment of the Franciscan GroupReconstruction of the depositional environment of the Franciscan Group

Western North America Tectonic Evolution Great Valley GroupGreat Valley Group – Shelf and slope deposition – Forearc basin

Western North America Tectonic Evolution Cordilleran OrogenyCordilleran Orogeny – Several phases  Nevada Orogeny – huge batholiths (L. Jr-K)  Sevier Orogeny – Pacific Plate subducted (K)  Laramid Orogeny – anticlines & dunes (L. K)

Western N.America Cause of Migration As subducting plate moved at a lower angle, the depth of melting moved to eastAs subducting plate moved at a lower angle, the depth of melting moved to east

Western N.A. Paleogeography Jurassic & Cretaceous Jurassic Navajo SS, Zion Clean, x-bedded SS (M. Jr)Clean, x-bedded SS (M. Jr) Nevadan orogenyNevadan orogeny Cretaceous interior seawayCretaceous interior seaway – Marine, Sundance Sea – Stream, lake deposits – Ms, sh = Morrison – Dinos (Jr) – Big inland sea – Gulf to Arctic – Accelerated spreading

Western North America Microplates >25% from accretion of microplates>25% from accretion of microplates – Material added to continents – Different in fossils, stratigraphy, structure, paleomagnetism – Formed elsewhere, transported along faults