The Geology of Delaware

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Kent Island Formation

Qki
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) named the Kent Island Formation for deposits bordering the Chesapeake Bay found underneath lowlands that ranged in elevation from 0 to 25 feet in elevation but most of the land surface area is less than 10 feet in elevation. These lowlands are bordered by a scarp with at toe at approximately 25 feet. In its type area, the Kent Island Formation was described as consisting of thick beds of loose, light colored, cross-stratified sand overlying dark-colored massive to thinly laminated clay-silt. Pebbles as much as 10 cm (4 in.) in diameter occur in thin beds with the sand or as scattered clasts in both the sand and clay-silt. Locally, large tree stumps in growth position are encased in the clay-silt. Maximum thickness of the Kent Island was about 12 m (40 feet).

The Kent Island Formation in Delaware consists of a lower, light-gray to reddish-brown, coarse sand to pebble gravel with scattered organic silty clay lenses; a middle, gray, clayey silt to silty clay; and an upper fine to medium, brownish-yellow sand with scattered clay laminae. Rare lenses of shell, most commonly the oyster Crassostrea, are found where the middle clay is at its thickest. The thickness of the Kent Island Formation in Delaware ranges from 0 to 25 feet.

Reference(s): 

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.