Boston Cliffs Member of Choptank Formation here named in Talbot Co., MD. Extends across Chesapeake Bay to VA. Described as 4.6 m of fossiliferous brown sand at Boston Cliffs along Choptank River. Gradationally overlies St. Leonard Member and underlies Conoy Member (both new names) of Choptank Formation. Age is middle Miocene.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Though elevated to formal member status by Gernant (1970), this author retains informal usage "to avoid name proliferation." Unconformably underlies St. Marys Formation; unconformably overlies Drumcliff shell bed. Thickness ranges from 0.6 to 3.6 m. Covers an area of 3,000 square km. Age is late Miocene. [See also Kidwell, 1989, Jour. Geol., v. 97, no. 1, p. 1-24.]

Source: GNU records (USGS DDS-6; Reston GNULEX).

Dominant sediment type of the Boston Cliffs Member of the Choptank Formation varies from reddish-brown to moderate brown, muddy to slightly muddy, fine sand. The most distinguishing characteristic is the prolific accumulation of shells. Thickness is approximately 13 ft at type section; elsewhere thicknesses vary between 3 and more than 15 ft. Lower contact with St. Leonard Member is gradational; upper contact with Conoy Member is sharp and distinct with an oxidized indurated sequence below and the nonresistant dusky-blue, fine sand of the Conoy above.

Source: GNU records (USGS DDS-6; Reston GNULEX).