Qa
Alluvium (Holocene); Unconsolidated mud, clay, silt, sand, gravel, and cobbles underlying flood plains
Alluvium (Holocene)
Ttu
Upper level upland terrace deposits (Miocene); Sandy gravel & gravelly quartz sand, w large pebbles & cobbles of vein quartz/quartzite; fluvial deposit. Lower part marine sand & sandy/clayey silt
As much as 10 m (35 ft) thick as much as 300 ft asl
Highest level upland terrace deposits (Tertiary)
Kp
Potomac Formation (Lower/Upper Cretaceous); Pebbly quartzofeldspathic sand, trough-crossbedded, grades laterally/upward to silty sand, clayey silt & silty clay w rare coalified/silicified plant stems
fluvial channel, bar, and  flood plain deposits; thickness ranges from a veneer on the west to about 40 ft ft , and as much as 250 ft asl
Potomac Formation (Upper and Lower Cretaceous)
Qd
Debris (Holocene and Pleistocene); Unsorted mixture of both fine and coarse material in hillslope depressions transported by gravity, water, and debris flow processes
Debris (Holocene and Pleistocene)
Qt
Terrace deposit, low level (Holocene and Pleistocene); Sand, gravel, and boulders on flat benches as much as __m (__ft) above drainages
Terrace deposit, low level (Holocene and Pleistocene)
Qte
Low level fluvial/estuarine deposits (mid & upper Pleistocene); Basal sand interbedded w silt & clay beds; wood fragments, sandy clay w pebbles & cobbles & limonite-filled rootzone; sand-capped
As much as 8 m (31 ft) thick and as much as 50 ft asl. Correlated with the Shirley Formation of Mixon and Southwick (1972), and the Maryland Point Formation (Davis and others, 2002)
Low level fluvial and estuarine deposits (Pleistocene)
QTt
Terrace deposit, high level (Pleistocene); Sand, gravel and boulders on flat benches as much as __m (__ft) above drainages
Terrace deposits, upper level (Pleistocene and Tertiary)
Qfe
Upper level fluvial and estuarine deposits (lower Pleistocene); Boulder and gravel beds at base, feldspathic quartz sand locally includes thin clay beds and thin to thick beds of clayey sand
Upper level fluvial and estuarine deposits (Pleistocene)