The

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Catskill Formation or the Catskill Clastic Wedge is a unit of mostly terrestrial

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

rock found in

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

and New York. Minor marine layers exist in this thick rock unit (up to ). It is equivalent to the Hampshire Formation of

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...

West Virginia West Virginia is a mountainous U.S. state, state in the Southern United States, Southern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States.The United States Census Bureau, Census Bureau and the Association of American ...

, and

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

. The Catskill is the largest bedrock unit of the Upper Devonian in northeast Pennsylvania and the Catskill region of New York, from which its name is derived. The Pocono Mountains of Pennsylvania are largely underlain by this unit as well. The rocks of the Catskill are a clastic wedge of predominantly red sandstone, indicating a large-scale terrestrial deposition during the Acadian orogeny. Many beds are cyclical in nature, preserving the record of a dynamic environment during its approximately 20 million years of deposition. The Catskill Formation preserves a highly diverse paleobiota, including many early sarcopterygians (especially tetrapodomorphs), providing important evidence about the evolution of terrestrial vertebrates. The formation also provides important fossils about the evolution of

land plants The embryophytes () are a clade of plants, also known as Embryophyta (Plantae ''sensu strictissimo'') () or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth's dry lands and wetlands. Embryophy ...

Geology

Depositional environment

During the Devonian period, the Catskill Delta was formed by a series of river deltas and otherwise marshy terrain. This terrain was sandwiched between the epicontinental Kaskaskia Sea in central

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

and the now-vanished Acadian Mountains. Erosion brought sediment from the mountain westwards into the sea, forming the deltas. Eventually, the Delta formation was buried and transformed into sandstone, which was then revealed in places when the Catskill and

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

were formed at a later date. This transformation and uncovering is the primary reason why the Catskill Delta is notable in the present. Western Pennsylvania's

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

was formed as a consequence. This was the first major oil region to be developed. The Catskill was once considered to be related to the Old Red Sandstone, but in actuality, the two are only coincidentally similar. Both formed at approximately the same time, and under similar conditions: to the north of the Acadian Mountains were the Caledonian Mountains, and a similar region of marsh and river delta formed there.

Glacial erosion

Though both mountain ranges were formed during the Acadian orogeny, the Catskill Mountains, unlike the Appalachian Mountains underwent glacial erosion. Much of what formed the Catskills as they stand today is a result of the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

which ended only about 12,000 years ago. There are many signs of the Glacial period event which carved the current day

Catskill Mountains The Catskill Mountains, also known as the Catskills, are a physiographic province and subrange of the larger Appalachian Mountains, located in southeastern New York. As a cultural and geographic region, the Catskills are generally defined a ...

. These markers include: * Glacial Erratics such as the Devils Tombstone * Striations * "Dance Floors" such as Pratt Rock * Terminal moraines

Members

Eastern Pennsylvania

Towamensing, Walcksville, Beaverdam Run, Long Run, Packerton, Poplar Gap, Sawmill Run, Berry Run, Clarks Ferry, and Duncannon.

Central Pennsylvania

Irish Valley, Sherman Creek, Buddys Run, Clarks Ferry, and Duncannon.

Paleobiota

Placoderms

Acanthodians

Chondrichthyans

Actinopterygians

Sarcopterygians

References

External links

Depositional environments in the Catskill Clastic Wedge
*

' Website summarize about Red Hill Shale in Catskill Formation {{Portal bar, Devonian Geologic formations of New York (state) Geologic formations of Pennsylvania Devonian Pennsylvania Devonian System of North America Devonian geology of Pennsylvania Devonian geology of New York (state) Devonian southern paleotemperate deposits Sandstone formations of the United States Shale formations of the United States Siltstone formations of the United States Deltaic deposits