The Geology of Delaware

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Sinepuxent Formation

Geologic Time Period: 
late Pleistocene
Coastal Plain - Primarily Surficial Unit

The following description was published in RI76 Stratigraphy, Correlation, and Depositional Environments of the Middle to Late Pleistocene Interglacial Deposits of Southern Delaware, Ramsey, K.W., 2010:

Owens and Denny (1979) described the Sinepuxent Formation in Maryland as dark, poorly sorted, silty fine to medium sand with the lower part of the unit being fine grained with thin beds of black clay. The Sinepuxent Formation is described as being lithically distinct from the Omar and Ironshire Formations due to the presence gray, laminated, silty very fine to fine, quartzose, micaceous, sand to sandy silt. The base of the unit is typically a bluishgray to dark-gray clayey silt to silty clay. There are a few shelly zones within the Sinepuxent Formation in the vicinity of Bethany Beach (McDonald, 1981; McLaughlin et al., 2008). The Sinepuxent Formation is up to 40 feet thick.


Owens, J.P., and Denny, C.S., 1979, Upper Cenozoic deposits of the Central Delmarva Peninsula, Maryland and Delaware: U.S. Geological Survey Professional Paper 1067-A, 28 p.

McDonald, K.A., 1981, Three-dimensional analysis of Pleistocene and Holocene coastal sedimentary units at Bethany Beach, Delaware: unpublished M.S. Thesis, University of Delaware, Newark, 205 p.

McLaughlin, P.P., Miller, K.M., Browning, J.V., Ramsey, K.W., et al., 2008, Stratigraphy and Correlation of the Oligocene to Pleistocene Section at Bethany Beach, Delaware: Delaware Geological Survey Report of Investigations No. 75, 41 p.