Bloomsburg Formation

Shale, sandstone; Guymard Quartzite; Otisville Shale; Shawangunk Conglomerate-sandstone, conglomerate.
State New York
Name Bloomsburg Formation
Geologic age Upper Silurian
Lithologic constituents
Sedimentary > Clastic > Sandstone
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > ConglomerateShawangunk Conglomerate-sandstone, conglomerate
Metamorphic > Metasedimentary > Metaclastic > QuartziteGuymard Quartzite
Comments part of Undifferentiated Silurian Rocks II, 0-1800 ft. (0-550 m). Secondary unit descriptions from USGS Lexicon website (ref. NY046) and reference NY044: The Bloomsburg Red Beds in southeastern NY is revised to include two intervening tongues, the lower Wurtsboro Tongue and the upper Basher Kill Tongue. These two tongues are separated by the Ellenville Tongue of the Shawangunk Formation. The Wurtsboro Tongue at its type section consists of 115 ft of interbedded red, green, and gray, cross bedded polymictic conglomerate, sandstone, siltstone, and shale. These lithologies occur in fining-upward cycles as much as 12 ft thick. The thickness of the Wurtsboro ranges from 300 ft north of Port Jervis, NY, to 75 ft at Accord, NY. The Wurtsboro Tongue grades upward into the Ellenville Tongue of the Shawangunk Formation. The Basher Kill Tongue overlies the Ellenville Tongue and its type section consists of 33 ft of olive-gray, brownish-gray, very fine-grained to granular, thin- to medium-bedded quartzite, and grayish-red to red-purple shaly siltstone. Near Port Jervis the Basher Kill is 330 ft thick. The Bloomsburg overlies the Shawangunk Formation and underlies either the Poxono Island Formation or the High View Tongue of the Shawangunk Formation. The Bloomsburg Red Beds is of Late Silurian age (Epstein, 1993). Rocks previously called Guymard Quartzite are considered to be the contact interval between the Shawangunk Formation and the Wurtsboro Tongue of the Bloomsburg Red Beds. The red bed within this interval is placed in the Shawangunk. Since these rocks can bed placed within the Shawangunk and Bloomsburg, the Guymard is abandoned (Epstein, 1993). Shales previously regarded as Otisville Shale vary considerably in abundance and stratigraphic position within short distances, and therefore, cannot be defined as a mappable unit. For these reasons, the Otisville is abandoned. Since these shales occur as part of the Shawangunk Formation, the shales formerly called Otisville are informally designated as the middle unit of the Shawangunk Formation (Epstein, 1993).

Fisher, D.W., Isachsen, Y.W., and Rickard, L.V., 1970, Geologic Map of New York State, consisting of 5 sheets: Niagara, Finger Lakes, Hudson-Mohawk, Adirondack, and Lower Hudson, New York State Museum and Science Service, Map and Chart Series No. 15, scale 1:250,000.

Epstein, J.B., 1993, Stratigraphy of Silurian rocks in Shawangunk Mountain, southeastern New York, including a historical review of nomenclature, IN Evolution of sedimentary basins; Appalachian basin: U.S. Geological Survey Bulletin, 1839-L, p. L1-L40.

USGS Geologic Names lexicon found at:

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