Shawangunk Formation

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Hand sample of the Shawangunk conglomerate from Blue Mountain, near New Tripoli, Pennsylvania.
Hand sample of the Shawangunk conglomerate from Blue Mountain, near New Tripoli, Pennsylvania.

The Silurian Shawangunk Formation (Ss) is a mapped bedrock unit in eastern Pennsylvania, New Jersey, and New York. It is named for the Shawangunk Ridge for which it is the dominant rock type.

Contents

[edit] Description

The Shanwangunk is defined as a light to dark-gray, fine to very coarsed grained sandstone and conglomerate, containing a few shale interbeds.[1] There are also four members of this formation: Tammany, Lizard Creek, Minsi, and Weiders. The Tammany and Lizard Creek members are equivalent to the Clinton Formation and the Minsi and Weiders members are equivalent to the Tuscarora Formation in the central and western part of Pennsylvania.[1]

[edit] Depositional Environment

The Shawangunk has always been interpreted as molasse resulting from the Taconic orogeny. The numerous coarse-grained beds, especially in the lower part, suggest a relatively close orogenic source with very high to high energy fluvial systems depositing the sediments. Shale interbeds may indicate a slowing or shifting of these ancient river systems.

[edit] Fossils

Very few fossils exist in the Shawangunk, however, Eurypterids can be found in the middle portions of the formation roughly 420–750 feet from the base in some locations in New York State. [2]

[edit] Age

Relative age dating of the Shawangunk places it in the Lower Silurian period, being deposited between 440 to 417 (±10) million years ago. It rests unconformably a top the Martinsburg Formation and conformably below the Bloomsburg Formation.[3]

[edit] Economic Uses

[edit] References

  1. ^ a b Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.
  2. ^ Epstein, J.B., (1993) Stratigraphy of Silurian Rocks in Shawangunk Mountain, Southeastern New York, Including a Historical Review of Nomenclature. United States Geological Survey Publication L14.
  3. ^ Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.

[edit] See also


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