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

2. 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

3. Events of the Mesozoic Era

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

5. Continental Rifting Rift grabens and aulocogens bounded by normal faults

6. Mesozoic Rift Basins
Non-marine-type
Marine-type

7. Graded Alluvial Fan Deposits along Graben Fault Scarps

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

9. 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)

10. 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

11. Navajo Sandstone at Zion NP, Utah

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

13. Middle Jurassic Transgression Brings on the Zuni Sequence

14. 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

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

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