Shriver chert, Allegany County, Maryland.
Shriver chert comes from the lower portion of the Shriver Member of the Oriskany Formation. Shriver chert is often used as the stratigraphic marker for the Oriskany/Helderberg contact. Sample collected at road cut near Spring Gap, Allegany County, Maryland.
Shriver Chert is blue-black nodular and bedded. Numerous planes in the bedded variety can limit utility. Chert beds are often separated by thin bands of dark shale. It can be fossiliferous and calcareous and weathers to a lighter patina. Cherty siltstone from this formation was also exploited prehistorically.
Prepared By Ebright 1999