Geology Reference
In-Depth Information
and Eastern Continental
Margins
In a previous section, we mentioned that
much of the Interior Lowlands eroded
during the Cenozoic. Even in the Great
Plains, where vast deposits of Cenozoic
rocks are present, sediment was carried
across the region and into the drainage
systems that emptied into the Gulf of
Mexico. Likewise, sediment eroded from
the western margin of the Appalachian
Mountains ended up in the Gulf, but
these mountains also shed huge quanti-
ties of sediment eastward that was de-
posited along the Atlantic Coastal Plain.
Notice in Figure 23.4 that the Atlantic
Coastal Plain and the
Gulf Coastal Plain
form a continuous belt extending from
the northeastern United States to Texas.
◗
Figure 23.12
Cenozoic Deposition Along the Gulf and East Coasts
Quaternary
Neogene
Paleogene
Cretaceous
Detrital shelf sediments
Carbonate shelf sediments
Deeper water sediments of
continental slope and
Sigsbee Deep
Gulf of Mexico
After the withdrawal of the Creta-
ceous to Early Paleogene Zuni Sea,
the Cenozoic
Tejas epeiric sea
made
a brief appearance on the continent.
But even at its maximum extent, it was
largely restricted to the Atlantic and
Gulf Coastal plains and parts of coastal
California. It did, however, extend up
the Mississippi River Valley, where
it reached as far north as southern
Illinois.
The overall Gulf Coast sedimenta-
tion pattern was established during
the Jurassic and persisted through-
out the Cenozoic. Sediments derived
from the Cordillera, western Appa-
lachians, and the Interior Lowlands
were transported toward the Gulf of
Mexico, where they were deposited in
terrestrial, transitional, and marine en-
vironments. The sediments form sea-
ward-thickening wedges, grading from
terrestrial facies in the north to marine
facies in the south (
Sigsbee Deep
Cuba
Yucatán
0
500 km
a
Depositional provinces and the surface geology of the Gulf and Atlantic coasts. Note the
carbonate shelf deposits near Florida and the Yucatán Peninsula of Mexico.
WEST
EAST
Shelf
break
New Jersey
Shore
Atlantic Ocean
Continental slope
and rise
Coastal
plain
Abyssal
plain
Continental shelf
fans
Cenozoic
reefs
Cretaceous
Triassic
basin
Jurassic
3050 meters
salt
80 km
CONTINENTAL CRUST
(Precambrian and Paleozoic sedimentary and
metamorphic rocks and intrusive igneous rocks)
Figure 23.12a).
Sedimentary facies development
was controlled mostly by regression
of the Tejas epeiric sea. After its maxi-
mum extent onto the continent during
the Paleogene, this sea began its long
withdrawal toward the Gulf of Mexico. Its regression, how-
ever, was periodically reversed by minor transgressions—eight
transgressive-regressive episodes are recorded in Gulf Coastal
Plain sedimentary rocks, accounting for the intertonguing
among the various facies.
◗
OCEANIC CRUST
(Early Mesozoic mafic
rocks & serpentinite)
b
The coastal plain and continental margin of New Jersey are covered mostly
by Cenozoic sandstones and shales.
think that each surface represents a differential response
to weathering and erosion. According to this view, a low-
elevation erosion surface developed on softer strata that
eroded more or less uniformly, whereas higher surfaces
represent weathering and erosion of more resistant rocks.
Search WWH ::
Custom Search