Earth History
GEOL 2110
The Mesozoic Era
Geology of 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 presentday 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
Non-marine-type
Mesozoic Rift Basins
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
Groundwater picks up silica from
sediment that is rich in siliceous
volcanic ash that is altered to clay
(bentonite)
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
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
Unconformity
Transgressive
Regressive
Absaroka Sequence
near Green River, UT
Dinosaur National Monument, CO
Zuni Sequence
Clastic Wedge Deposit in the Cretaceous
Foreland Basin of the Cordilleran Orogen.
Next Lecture
Tectonic History of the North
American Cordilleran