Unit | Description |
---|---|
Mining Fill | Mine spoils placed into old abandoned mine excavation. Commonly 4.6–7.6 m thick, beneath sediment disposal site. Mixed member: poorly sorted mixture of gravel, sand, silt, and clay;deposited by dumping; mostly under north half of refilled mine sites. Stratified member: stratified sands and mud deposited in a lake fromwest to east; mostly under the south end of refilled mine site. |
Kennon Formation | Fining upward stream deposit (gravelly sand to silty clay) dominatedby thick clay-rich beds; 1.5–4.6 m thick; fills small recentvalleys carved into Tabb Formation beds. |
Tabb Formation | Fining upward stream deposit (cobble beds to silty clay) dominatedby cobbles and gravelly sand; 3.7–6.7 m thick; carpets largevalley carved by the James River; forms broad terrace surface 4.6–6.1 m elevation. |
Shirley Formation | Sand and gravel deposit (6.1 m thick) with silty clay cap (1.5 m thick); forms broad terrace at approximately 9.1–12.2 melevation, and terrace remnant beneath Shirley Plantation manorhouse |
Nanj emoy-Marlborounit | Sandy silt-clay confining bed; glauconitic; compact; encounteredbeneath Tabb Formation and Mining Fill |
Aquia-Potomac units | Layered gravelly aquifers and confining beds (42.7+ m thick) |