Advance copy (1978). Popes Creek Sand Member of Calvert Formation. Name applied to the basal transgressive beds of the Fairhaven Member (restricted) of Calvert Formation in the Salisbury embayment; beds are lithologically distinct from the rest of the Fairhaven. Exposures found west of the Chesapeake Bay, from near Fairhaven south to Popes Creek, Maryland, and into Virginia. Traced into subsurface of Delaware. Consists of olive-brown and green to greenish-white glauconitic quartz sand with a basal layer of quartz and phosphate pebbles and phosphatized mollusk shells. Thickness at type section 10.5 feet (3.3 m). Unconformably overlies Nanjemoy Formation; along the Patuxent River in Maryland, overlies an older cycle of sand and diatomaceous clay beds (Dunkirk beds of Calvert Formation). Underlies Fairhaven Member of Calvert. Age is early Miocene.
Type section: outcrop on the north bank of the Potomac River, 300 ft (91 m) southeast of the mouth of Popes Creek, Charles Co., MD.

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

Name Popes Creek Sand Member for bed at the base of the Calvert Formation is discarded, and these strata reassigned to the Fairhaven Member. Though a phosphate pebble lag indicates an unconformity, diatomaceous clays on either side of that contact are so similar that they cannot be separated lithologically.

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