The Mesozoic Era Tectonic and Geologic History In North America Earth History GEOL 2110 The Mesozoic Era Tectonic and Geologic History In North America

Major Concepts The geologic history of North America during the Mesozoic Era was dominated by two contrasting tectonic processes : On the east, continental rift of Pangea was creating the present- day Atlantic margin On the west, compressional tectonics accreted exotic terranes in the early Mesozoic (Triassic and early Jurassic periods) and then became Andean-type volcanic arc in the mid- to late Mesozoic (Jurassic and Cretaceous periods). Sedimentation in the Mesozoic was largely in western NA and was dominantly non-marine with sediment supplied by the erosion of the Appalachians and the emerging Cordilleran Orogen. A major transgression in the Cretaceous created a Great Interior Seaway where great accumulation of marine and non-marine sediment were deposited in the Great Plains

Events of the Mesozoic Era

Un-Making Pangea Superplume disassembles the Supercontinent Late Triassic (215Ma) Now Pangea Late Cretaceous (95Ma)

Continental Rifting Rift grabens and aulocogens bounded by normal faults

Mesozoic Rift Basins Non-marine-type Marine-type

Graded Alluvial Fan Deposits along Graben Fault Scarps

Triassic Red-bed Sedimentation in the West Painted Desert Upper Triassic Chinle Formation 2013 SEG Field Trip Petrified Forest

Petrified Wood Replacement by Silica That the wood does not rot, indicates reducing environments with rapid deposition (floodplains, lagoons, ). The petrifaction process preserves the original cellular structure of the wood Groundwater picks up silica from sediment that is rich in siliceous volcanic ash that is altered to clay (bentonite)

Early Jurassic Regression Eolian SS Mark the End of the Absaroka Sequence Navajo Desert Navajo Sandstone Canyon de Chelley 2013 SEG Field Trip Canyon de Chelley

Navajo Sandstone at Zion NP, Utah

Dinos on the Dunes Dilophosaurus Coprolite?? Dino-pie Dilophosaurus Footprints in the Jursassic Kayenta Formation near Tuba City, AZ

Middle Jurassic Transgression Brings on the Zuni Sequence

Morrison Formation Upper Jurassic Dinosaur Graveyard Non-marine mudstone, sandstone, siltstone and limestone that is variegated light grey, greenish gray, or red; represents floodplains deposits Zuni Sequence Transgressive Regressive Unconformity Absaroka Sequence near Green River, UT Dinosaur National Monument, CO

Zuni Sequence Clastic Wedge Deposit in the Foreland Basin of the Cordilleran Orogen.

Tectonic History of the North American Cordilleran Next Lecture Tectonic History of the North American Cordilleran Quiz on Chapter 14 (p. 351-381)