The
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
Catskill Formation or the Catskill
Clastic wedge
In geology, clastic wedge usually refers to a thick assemblage of sediments--often lens-shaped in profile--eroded and deposited landward of a mountain chain; they begin at the mountain front, thicken considerably landwards of it to a peak depth, an ...
is a unit of mostly terrestrial
sedimentary
Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...
rock found in
Pennsylvania
Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
and
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
. Minor marine layers exist in this thick rock unit (up to ). It is equivalent to the
Hampshire Formation of
Maryland
Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...
,
West Virginia
West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...
, and
Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
.
The Catskill is the largest bedrock unit of the
Upper Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...
in northeast Pennsylvania and the
Catskill region of New York, from which its name is derived. The
Pocono Mountains
The Pocono Mountains, commonly referred to as the Poconos , are a geographical, geological, and cultural region in Northeastern Pennsylvania. They overlook the Delaware River and Delaware Water Gap to the east, Lake Wallenpaupack to the north, ...
of Pennsylvania are largely underlain by this unit as well. The rocks of the Catskill are predominantly
red sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) b ...
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.
Depositional environment
![Catskill-slab-new](https://upload.wikimedia.org/wikipedia/commons/b/b4/Catskill-slab-new.jpg)
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 and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
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, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
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 mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
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
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...
, 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 Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cor ...
which ended only about 12,000 years ago.
Signs of Glaciation
There are many signs of the
Glacial period
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...
event which carved the current day
Catskill Mountains
The Catskill Mountains, also known as the Catskills, are a physiographic province of the larger Appalachian Mountains, located in southeastern New York. As a cultural and geographic region, the Catskills are generally defined as those areas c ...
.
These markers include:
* Glacial Erratics such as the
Devils Tombstone
* Striations
* "Dance Floors" such as
Pratt Rock
Pratt Rock, also known as Pratt's Rock, is a rockface or other landform that includes a series of stone carvings in Prattsville, New York depicting the life of Zadock Pratt. Pratt was supposed to be buried in a tomb carved into the stone, but work ...
*
Terminal moraine
A terminal moraine, also called end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge ...
s
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.
References
External links
Depositional environments in the Catskill Clastic Wedge
{{Chronostratigraphy of Pennsylvania
Geologic formations of New York (state)
Geologic formations of 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
Deltaic deposits