historical geology early cenozoic i

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HISTORICAL GEOLOGYEARLY 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 andCoastal PlainsRockies 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 CoastRelatively 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 TectonicsSubduction 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 the Farallon Plate.

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San Andreas FaultCascadesColumbia PlateauBasin and RangeColorado Plateau

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San Andreas Fault

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The Cascades - volcanic arc.

Mt. St. Helens, 1980.

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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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Death Valley, California.

Basin

Range

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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 SeawayClosure 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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