The MesozoicThe Mesozoic

Periods of the MesozoicPeriods of the Mesozoic

►TriassicTriassic► JurassicJurassic►CretaceousCretaceous

Breakup of PangaeaBreakup of Pangaea

► Stage one (Triassic) Rifting and volcanism, normal faulting

Tensional stresses separate N. America from Gondwanaland

Similarly, Mexico from S. America

Sea floor generated during opening of ocean

Breakup of PangaeaBreakup of Pangaea

► Stage two (Triassic-Jurassic)Stage two (Triassic-Jurassic)

Rifting of narrow Oceans between S. Rifting of narrow Oceans between S. Africa and Antarctica, Africa and IndiaAfrica and Antarctica, Africa and India

Massive outpouring of basaltic lavas (7 Massive outpouring of basaltic lavas (7 million km2)million km2)

Breakup of PangaeaBreakup of Pangaea

► Stage three (Jurassic-Cretaceous)Stage three (Jurassic-Cretaceous) Atlantic Ocean rift extended northward Atlantic Ocean rift extended northward Clockwise rotation of EurasiaClockwise rotation of Eurasia Closing of eastern Tethys Sea Closing of eastern Tethys Sea

(Mediterranean) (Mediterranean) S. America-Africa split apartS. America-Africa split apart Australia-Antarctica remain intactAustralia-Antarctica remain intact Eastern N. America and Greenland Eastern N. America and Greenland

remain intactremain intact

Post Mesozoic BreakupPost Mesozoic Breakup

► Stage four Stage four

N. America and Eurasia split N. America and Eurasia split completelycompletely

Antarctica and Australia splitAntarctica and Australia split

Mesozoic history of N. Mesozoic history of N. AmericaAmerica

► Eastern and Southern areasEastern and Southern areas Triassic and JurassicTriassic and Jurassic

► Normal fault bounded basin develop Normal fault bounded basin develop due to rifting (Nova Scotia to North due to rifting (Nova Scotia to North Carolina)Carolina) Troughs filled with terrestrial sediments Troughs filled with terrestrial sediments

and volcanicsand volcanics Newark Group (upper Triassic-lower Newark Group (upper Triassic-lower

Jurassic)Jurassic) Palisades Sill of NJ and NY (190mya)Palisades Sill of NJ and NY (190mya)

Triassic and JurassicTriassic and Jurassic

► Development of Gulf of MexicoDevelopment of Gulf of Mexico

Occupied areas opening south of Occupied areas opening south of Appalachian-Ouachita folded mountainsAppalachian-Ouachita folded mountains

Filled with Upper Triassic-Lower Jurassic Filled with Upper Triassic-Lower Jurassic salts and evaporates (indicating previous salts and evaporates (indicating previous arid condition); over 1000m deposited arid condition); over 1000m deposited (origin of Gulf Coast salt domes)(origin of Gulf Coast salt domes)

CretaceousCretaceous

► Flooding of coastal lowlands due to high Flooding of coastal lowlands due to high sea levelssea levels► Atlantic and Gulf Coast plains inundated as they Atlantic and Gulf Coast plains inundated as they

acted as subsiding shelvesacted as subsiding shelves► Thick delta, barrier island, shelf and reef Thick delta, barrier island, shelf and reef

depositsdeposits► Florida: Shallow submarine bank for limestonesFlorida: Shallow submarine bank for limestones► Reefs made of Rudistid bivalves rimmed Reefs made of Rudistid bivalves rimmed

Gulf Coastal areaGulf Coastal area► Extensive chalk deposits due to massive Extensive chalk deposits due to massive

production of calcerous planktonproduction of calcerous plankton Rifting and ocean opening on eastern side Rifting and ocean opening on eastern side

leads to closure and compression on leads to closure and compression on western sidewestern side

Western AreasWestern Areas

► TriassicTriassic Accretionary tectonics- Characteristic of Accretionary tectonics- Characteristic of

west coast subductionwest coast subduction► Steeply dipping subduction zoneSteeply dipping subduction zone► Volcanic Arcs and micro-continents carried Volcanic Arcs and micro-continents carried

to western marginto western margin► Massive accretion by subduction (including Massive accretion by subduction (including

volcanics)volcanics)► Tectonic collage of displaced terrain 70% of Tectonic collage of displaced terrain 70% of

total western accretiontotal western accretion

Cordilleran RegionCordilleran Region

► Western belt- Volcanics and siliceous Western belt- Volcanics and siliceous depositsdeposits

► Eastern belt- stable interior sedimentsEastern belt- stable interior sediments

Sonoma Orogeny Sonoma Orogeny (Permian- Triassic, (Permian- Triassic,

Nevada)Nevada)

► Island arc collided with western Island arc collided with western marginmargin

► Then a west dipping subduction zoneThen a west dipping subduction zone► Added 300km new area to westAdded 300km new area to west► Massive thrust faultingMassive thrust faulting

Eastern Belt depositionEastern Belt deposition

► Sandstones and limestones Sandstones and limestones (shallow marine, 1000m in Idaho)(shallow marine, 1000m in Idaho)

► Lower Triassic red bed facies Lower Triassic red bed facies farther eastfarther east

► Upper Triassic sediments mostly Upper Triassic sediments mostly from rivers (flowed west over area)from rivers (flowed west over area)

Upper Triassic- Jurassic Stratigraphy: Moenkopi Upper Triassic- Jurassic Stratigraphy: Moenkopi fm, Shinarup Fm., Navajo Sandstone, Wingate fm, Shinarup Fm., Navajo Sandstone, Wingate SandstoneSandstone

Jurassic-Early TertiaryJurassic-Early Tertiary

► Nevadan OrogenyNevadan Orogeny (eastward shift (eastward shift in orogenic effect)in orogenic effect)

Formation of Convergent Formation of Convergent mélangemélange depositsdeposits

Franciscan belt of California (classic Franciscan belt of California (classic mélange) mélange)

Great volumes of granodiorite intruded: Great volumes of granodiorite intruded: Sierra Nevada, Idaho, and coastal range Sierra Nevada, Idaho, and coastal range batholithsbatholiths

Sevier Orogeny Sevier Orogeny (middle Jurassic- earliest (middle Jurassic- earliest

Tertiary)Tertiary)

► Precedes batholith intrusionPrecedes batholith intrusion► basement-involved tectonics: basement-involved tectonics:

multiple imbricated thrust faults (low multiple imbricated thrust faults (low angle)angle)

► Mainly seen in NV, UT and MTMainly seen in NV, UT and MT Most famous thrust fault: Lewis Thrust Most famous thrust fault: Lewis Thrust

(65km displacement)(65km displacement)

Jurassic and Cretaceous Jurassic and Cretaceous SedimentationSedimentation

Navajo SandstoneNavajo Sandstone (Lower Jurassic): Clean recycled eolian (Lower Jurassic): Clean recycled eolian sands deposited in coastal dune and shoreline sands deposited in coastal dune and shoreline environmentsenvironments

Sundance FormationSundance Formation (Middle Jurassic) Famous for fossil (Middle Jurassic) Famous for fossil reptiles deposits of the Sundance Seareptiles deposits of the Sundance Sea

Morris FormationMorris Formation (Upper Jurassic) Swampy plain deposits (Upper Jurassic) Swampy plain deposits formed as Sundance Sea retreated upon rising formed as Sundance Sea retreated upon rising CordilleranCordilleran

Early Cretaceous SeawayEarly Cretaceous Seaway: marine intrusion leaving : marine intrusion leaving deposits south from Arctic ocean to Gulf of Mexicodeposits south from Arctic ocean to Gulf of Mexico

End of the MesozoicEnd of the Mesozoic► K/T BoundaryK/T Boundary

Marks the border between the Cretaceous Marks the border between the Cretaceous (K) and the Tertiary (beginning of current (K) and the Tertiary (beginning of current era-Cenozoic)era-Cenozoic)