Reports
Pleistocene stratigraphy of the Salisbury area, Maryland and its relationship to the lower Eastern Shore: A subsurface approach
1966, Hansen, H.J.
Report of Investigations 2
Abstract
The Salisbury, Maryland, water resources investigation afforded the opportunity for a detailed subsurface study of the Pleistocene Series beneath a 90-square-mile area surrounding the city. Twenty-four core holes and 15 test holes were drilled to provide the ground-water phase of the program with a geologic framework. From these new data emerged a clarification of the stratigraphic sequence which, in turn, resulted in a reasonable definition of Pleistocene history.
North of Salisbury a deep Pleistocene paleochannel was discovered. It is inferred that this ancient river, the Naylor Mill paleochannel, was incised during a low sea stand correlative with the Illinoian (?) Glaciation. Filling in and overlying this paleochannel is the “red gravelly” facies of the Salisbury Formation, a fluvial sand deposited by an aggrading river during a period of rising base-level conditions, possibly coincident with the Sangamon Interglaciation. The estuarine (?) equivalent of the “red gravelly” facies is the Beaverdam facies, a gray-white, fine to coarse-grained sand. The “red gravelly” facies is thickest north and west of Salisbury; it wedges out easterly toward Parsonsburg and southerly toward Princess Anne. Complementing this is an easterly and southerly thickening of the Beaverdam facies.
Overlying the Salisbury Formation is the Walston Formation, an extensively developed fine-grained sediment. The Walston Formation is a time transgressive unit deposited from late Sangamon (?) through early Wisconsin (?) time in a series of fringing tidal marshes. As sea level fell, these swampy areas formed west of Parsonsburg divide at progressively lower elevations. The Parsonsburg Sand, a coastal dune deposit, overlies the Walston Formation in the divide area. The Parsonsburg Sand was deposited during the high sea stand marking the transition between the Sangamon (?) Interglaciation and the early Wisconsin (?) Glaciation. The stratigraphic relationship between the Parsonsburg sand and the Walston Formation reflects the transgressive advance of dune sand over a surrounding tidal marsh facies.
By the end of late Wisconsin time the present-day drainage network was incised into the terrane. As sea level rose during the subsequent Holocene marine transgression, intercalated fluvial gravels and marsh muds were deposited in and adjacent to present-day rivers, such as the Wicomico and Nanticoke.
Although the above sediments lack the commonly sought minerals and fuels, they appear to have more value than generally appreciated. For example, the Salisbury Formation is an excellent source of ground water. In addition, the Walston Formation may serve as a source material for clay products and the Holocene sands and gravels for building and road aggregate.
