HISTORICAL GEOLOGY
EARLY CENOZOIC I.
EARLY CENOZOIC:
(65-1.8 MYBP):
Introduction: Much of
the landscape as it
appears today resulted
from a number of
"land-forming" events
of the early Cenozoic.
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Paleogene
Paleogeography.
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Appalachians and
Coastal Plains
Rockies and Great Plains
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Gulf Coast Main area of marine transgressions and regressions
during Cenozoic, this, combined with pronounced subsidence,
resulted in about 10 000 m of Paleogene/Neogene sediments
underlying the Gulf Coast
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East Coast
Relatively quite
during the Cenozoic. The
erosion of the Appalachians
continued, producing
subdued, rounded mountains
(characteristic of ancient
mountains). The coastal plain
and continental shelf
continued to be built from
clastics in the northeast and
carbonates in the southeast
(Florida).
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Low, rounded,
vegetated
mountain ridges
in the
Appalachians.
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East coast coastal
plain – dominated by
coastal processes and
landforms e.g. spits,
barriers, beaches,
marshes, etc.
Cape
Fear
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Barrier Island
Mississippi delta
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Bahama Banks
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Rockies Continuing uplift and erosion shaped the Rockies into
rugged, sharp peaks (characteristic of youthful mountains). In some
areas, large fault blocks were pushed up to form mountain ranges,
such as the Tetons of Wyoming. Clastics from the erosion spread
eastward, forming the Great Plains.
Tetons.
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West Coast Tectonics
Subduction down much of the
west coast stopped in the
Cenozoic, as the Farallon
Plate* and the east Pacific
Rise* were “swallowed” by
the subduction zone. Instead,
a transform fault developed
about 10 million years ago.
Subduction continued to the
north (Juan de Fuca plate)
and the south (Cocos plate). A
number of features are related
to these plate movements…
* 1st time we’ve covered these.
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San Andreas Fault
Cascades
Columbia Plateau
Basin and Range
Colorado Plateau
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San Andreas Fault
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Mt. St. Helens, 1980.
The Cascades - volcanic arc.
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Columbia Plateau - flood
basalts resulting from a
hot spot.
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Basin And Range Province Tensional forces developed in large
areas of Nevada, Arizona, New Mexico and South California
during the Cenozoic, probably resulting from the change from
subduction to transform fault along the craton margin and heat
flow from subduction. The result was basin and range topography,
characterized by normal faults, tilted fault blocks, grabens and
horsts:
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Range
Basin
Death Valley, California.
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Graben and horst.
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Tilted fault blocks.
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Colorado Plateau
A large block of crust in
the southwest remained
relatively undeformed, but
was uplifted during the
Cenozoic (5 -10 mybp),
forming the Colorado
Plateau. Streams cut down
into the plateau as it was
lifted up, forming deep
canyons, including the
Grand Canyon (2600 m
deep). Magma was
released from faults
surrounding the uplifted
plateau.
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Grand Canyon.
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Plateaus, mesas, buttes and pinnacles formed by stream erosion of
uplifted strata.
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Tethys Seaway
Closure of the Tethys Seaway was completed during the
Cenozoic. Africa collided with Europe about 40 million years
ago forming the PYRENEES, between France and Spain, and
the ATLAS MOUNTAINS of northwest Africa. As Africa swung
around, the collision spread eastward, forming the ALPS of
southern Europe. Areas of the Alps are still undergoing periodic
uplift today (the collision continues). Further east, India
collided with Asia about 10 million years ago, forming the
HIMALAYAS (the top of Mt. Everest is marine limestone);
these mountains are also continuing to rise – frequent
earthquakes in India/China attest to the continuing movement.
These orogenies created a long linear zone of mountains
running east – west across Europe and Asia.
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