The Barhamsville unit represents a major phase of deposition in the southern Salisbury embayment during the late Pliocene. Deposition was dominantly intertidal to nonmarine. On the York-James Peninsula and south of the James River, the unit unconformably overlies the marine Yorktown Formation or, to the west, older Tertiary units and is cut into and overlain by the Windsor Formation.

The Barhamsville unit is the major surficial unit of the region and ranges in thickness from near 0 m at its westernmost exposure to 20 m in paleochannels. The unit contains an eastern tidal flat complex consisting of mixed flat, lower flat, and tidal channel deposits and a western fluvial and reworked fluvial complex consisting of coarse-grained, gravelly, nearshore(?) and fluvial channel deposits. These coarse-grained deposits are overlain by fine-grained marsh(?) and estuarine(?) deposits.

Antecedent topography may have had an influence on deposition of the unit. Structure contours on its base show a gently seaward-dipping surface, which is channeled along its western margin near the present James River. This surface has a distinct break in slope coincident with the tidal-flat nearshore/fluvial boundary. The break in slope is considered to be an erosional rather than a structural feature. Direct dating of the Barhamsville unit is not available due to a lack of body fossils and pollen. It's age is considered to be late Pliocene based on stratigraphic position.

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