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Uplands
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Epeiric sea
Deep ocean
Pal eoeq uat or
Figure 22.4 Triassic Paleogeography of North America
to the Gulf of Mexico (Figure 22.6). Sediments deposited in
the Gulf Coastal region during the Cretaceous formed a sea-
ward-thickening wedge.
Reefs were also widespread in the Gulf Coast region
during the Cretaceous. Because of their high porosity and
permeability, reefs make excellent petroleum reservoirs. The
facies patterns of these Cretaceous reefs are as complex as
those in the major barrier-reef systems of the Paleozoic Era.
this oceanic-continental convergent plate boundary resulted
in an eastward movement of deformation. This orogenic ac-
tivity progressively affected the trench and continental slope,
the continental shelf, and the cratonic margin, causing a
thickening of the continental crust. In addition, the accre-
tion of terranes and microplates along the western margin of
North America also played a signifi cant role in the Mesozoic
tectonic history of this area.
Except for the Late Devonian-Early Mississippian Antler
orogeny (see Figure 20.27), the Cordilleran region of North
America experienced little tectonism during the Paleozoic.
However, an island arc and ocean basin formed off the west-
ern North American craton during the Permian (Figure 22.4),
followed by subduction of an oceanic plate beneath the island
arc and the thrusting of oceanic and island arc rocks eastward
Western Region
Mesozoic Tectonics The Mesozoic geologic history of the
North American Cordilleran mobile belt is very complex, in-
volving the eastward subduction of the oceanic Farallon plate
under the continental North American plate. Activity along
 
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