The Mesozoic
Periods of the Mesozoic Triassic- First period of the Mesozoic era Jurassic Cretaceous- Last period of the Mesozoic era
Breakup 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 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 Pangaea Stage two (Triassic-Jurassic) Rifting of narrow Oceans between S. Africa and Antarctica, Africa and India Massive outpouring of basaltic lavas (7 million km2)
Breakup of Pangaea Stage two (Triassic-Jurassic) Rifting of narrow Oceans between S. Africa and Antarctica, Africa and India Massive outpouring of basaltic lavas (7 million km2)
Breakup of Pangaea Stage three (Jurassic-Cretaceous) Atlantic Ocean rift extended northward Clockwise rotation of Eurasia Closing of eastern Tethys Sea (Mediterranean) S. America-Africa split apart Australia-Antarctica remain intact Eastern N. America and Greenland remain intact
Breakup of Pangaea Stage three (Jurassic-Cretaceous) Atlantic Ocean rift extended northward Clockwise rotation of Eurasia Closing of eastern Tethys Sea (Mediterranean) S. America-Africa split apart Australia-Antarctica remain intact Eastern N. America and Greenland remain intact
Post Mesozoic Breakup Stage four N. America and Eurasia split completely Antarctica and Australia split
Post Mesozoic Breakup Stage four N. America and Eurasia split completely Antarctica and Australia split
Mesozoic history of N. America Eastern and Southern areas Triassic and Jurassic Normal fault bounded basin develop due to rifting (Nova Scotia to North Carolina) Troughs filled with terrestrial sediments and volcanics Newark Group (upper Triassic-lower Jurassic) Palisades Sill of NJ and NY (190mya)
Triassic and Jurassic Development of Gulf of Mexico Occupied areas opening south of Appalachian- Ouachita folded mountains Filled with Upper Triassic-Lower Jurassic salts and evaporates (indicating previous arid condition); over 1000m deposited (origin of Gulf Coast salt domes)
Cretaceous Flooding of coastal lowlands due to high sea levels Atlantic and Gulf Coast plains inundated as they acted as subsiding shelves Thick delta, barrier island, shelf and reef deposits Florida: Shallow submarine bank for limestones Reefs made of Rudistid bivalves rimmed Gulf Coastal area Extensive chalk deposits due to massive production of calcerous plankton Rifting and ocean opening on eastern side leads to closure and compression on western side
Western Areas Triassic Accretionary tectonics- Characteristic of west coast subduction Steeply dipping subduction zone Volcanic Arcs and micro-continents carried to western margin Massive accretion by subduction (including volcanics) Tectonic collage of displaced terrain 70% of total western accretion
Cordilleran Region Western belt- Volcanics and siliceous deposits Eastern belt- stable interior sediments
Sonoma Orogeny (Permian- Triassic, Nevada) Island arc collided with western margin Then a west dipping subduction zone Added 300km new area to west Massive thrust faulting
Sonoma Orogeny (Permian- Triassic, Nevada) Island arc collided with western margin Then a west dipping subduction zone Added 300km new area to west Massive thrust faulting
Eastern Belt deposition Sandstones and limestones (shallow marine, 1000m in Idaho) Lower Triassic red bed facies farther east Upper Triassic sediments mostly from rivers (flowed west over area) Upper Triassic- Jurassic Stratigraphy: Moenkopi fm, Shinarup Fm., Navajo Sandstone, Wingate Sandstone
Jurassic-Early Tertiary Nevadan Orogeny (eastward shift in orogenic effect) Formation of Convergent mélange deposits Franciscan belt of California (classic mélange) Great volumes of granodiorite intruded: Sierra Nevada, Idaho, and coastal range batholiths
Sevier Orogeny middle Jurassic- early Tertiary Precedes batholith intrusion basement-involved tectonics: multiple imbricated thrust faults (low angle) Mainly seen in NV, UT and MT Most famous thrust fault: Lewis Thrust (65km displacement)
Jurassic and Cretaceous Sedimentation Navajo Sandstone (Lower Jurassic): Clean recycled eolian sands deposited in coastal dune and shoreline environments Sundance Formation (Middle Jurassic) Famous for fossil reptiles deposits of the Sundance Sea Morris Formation (Upper Jurassic) Swampy plain deposits formed as Sundance Sea retreated upon rising Cordilleran Early Cretaceous Seaway: marine intrusion leaving deposits south from Arctic ocean to Gulf of Mexico
End of the Mesozoic K/T Boundary Marks the border between the Cretaceous (K) and the Tertiary (beginning of current era-cenozoic)
Composition of the KT Boundary Tektites and shock quartz
Composition of the KT Boundary In 1980 a team of researches published an elemental analysis of the K/T boundary that showed high levels of the element iridium. Since then these same results have been shown in multiple locations around the world
What Caused the K/T boundary? All the evidence points to a meteorite impact. The problem is where is the crater Meteor Crater Arizona
What Caused the K/T boundary? All the evidence points to a meteorite impact. The problem is where is the crater Meteor Crater Arizona
Locating the Crater
Locating the Crater