Londonbridge and Sand Bridge Formations are here reduced in rank and assigned as Members to the newly named Powells Crossroads Formation. Together these members represent a single transgressive-regressive depositional event similar to that of the newly named Acredale Formation. Silty clays of the Londonbridge are marsh and estuarine deposits of a warm transgressing sea. Gray silty sands in the lower part of the Sand Bridge indicate an open marine environment and grade upward into coarser cross-bedded sands of an intertidal and very nearshore environment. Unit unconformably overlies the Kempsville Member or, where absent, the Norfolk Member, of the Acredale Formation. Unit is 5.6 m thick at the type section. Age is late Pleistocene based on fauna.

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