West Virginia

* * * West Virginia * * *

Geology of West Virginia
West Virginia Geological Map
Bedrock Geology of West Virginia

The majority of bedrock exposed at the surface in West Virginia is sedimentary in origin, deposited during the Paleozoic "Ancient Life Era" (545 to 230 million years ago); very few igneous or metamorphic rocks are exposed at the surface due to deep burial beneath the thick Paleozoic cover. The geologic history of West Virginia prior to the Paleozoic "Ancient Life Era" is poorly understood. The oldest exposed rock in the State, in the tip of the eastern panhandle, is the Precambrian Catoctin Greenstone, a metamorphosed lava which erupted 800 million years ago. During the Cambrian (541 to 485 million years ago) and Ordovician periods (485 to 443 million years ago), the State was covered by a sea that deposited limestone, shales, siltstones, and minor sandstones. These rocks are now exposed at the surface in the eastern panhandle.

Motion of the earth's tectonic plates reshape and deform preexisting rock units; subsequent erosion and deposition of the sediments produces new rock layers. The first well-known tectonic event to affect the State, the Ordovician Taconic Orogeny, formed a mountain chain to the north and east of West Virginia that became the source of clastic sediment during the latest Ordovician (485 to 443 million years ago), Silurian (443 to 419 million years ago), and early Devonian (410 to 358 million years ago). Marine carbonates were deposited in south and central West Virginia during this time; the north and west were dominated by non-marine clastics and evaporites, especially during the late Silurian (443 to 419 million years ago) .

The next tectonic event, the Devonian Acadian Orogeny, formed a new set of mountains to the northeast. Erosion of these mountains produced sediment deposited across the State from the late Devonian (410 to 358 million years ago) into the Pennsylvanian (323 to 298 million years ago). Regression of the Devonian sea led to the deposition of continental red beds over much of the State at the end of the Devonian (410 to 358 million years ago) . The sea returned in the Mississippian (358 to 323 million years ago) and thick limestones of

the commercially important Greenbrier Group were deposited.

During the Late Mississippian (358 to 323 million years ago), the sea regressed from West Virginia leaving a low-lying, swampy Pennsylvanian terrain (323 to 298 million years ago) which produced thousands of feet of mainly non-marine sandstone, shale,

and coal, the State's economic mainstay.

During the latest Mississippian (358 to 323 million years ago) and into the Permian (298 to 252 million years ago), the Appalachian Orogeny (325 to 260 million years ago) produced the Appalachian Mountains we know today. Even as these Mountains were being formed from existing rock layers, erosion began to wear them down providing a new source

of sediment for streams flowing to the west.

After end of the Appalachian Orogeny (325 to 260 million years ago) in the early Mesozoic "Middle Life Era" (252 to 66 million years ago) also called the "Age of Reptiles", the Atlantic Ocean began opening to the east. Although erosion of the Appalachians produced clastic sediment throughout the Mesozoic (252 to 66 million years ago) and into the present day, no sedimentary rock layers remain from these time periods. However, the extensive deformation of bedrock allowed the intrusion of numerous Mesozoic "Middle life Era" (252 to 66 million years ago) and Cenozoic "New Life Era" (66 million years ago to present) igneous rocks

in east-central West Virginia, especially Pendleton County.

Glaciers of the Pleistocene Ice Age (2.58 million years ago to present) never reached West Virginia. However, two large, ice-dammed lakes formed in the present Monongahela and Teays valleys, forming lake deposits, changes to the State's drainage, and alluvial deposits in the major river valleys, notably the newly-formed Ohio River. These are the only Cenozoic

(younger than 70 million years) sedimentary deposits in the state.

Geologically Tectonics, the Cenozoic is the "New Life Era" (66 million years ago to present) when the continents moved into their current positions. Australia-New Guinea, having split from Pangea during the early Cretaceous, drifted north and, eventually, collided with South-east Asia; Antarctica moved into its current position over the South Pole; the Atlantic Ocean widened and, later in the era, South America became attached to North America. India collided with Asia

(55 to 45 million years ago) ; Arabia collided with Eurasia,

closing the Tethys Ocean around 35 million years ago.

The New River ( Kanawha River - 300 million years ) in West Virginia is considered one of the oldest rivers in the world, if not the oldest and the Appalachian Mountains there where once higher than the Himalayan's and are considered by many scientist to be one of the oldest mountain ranges in the world, comparing the Grand Canyon

that is estimated, to be 5 to 10 million years old.

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