|SREL Reprint #2412|
Descriptive Ecology of the Shenandoah Valley Sinkhole Pond System in Virginia
Kurt A. Buhlmam
Joseph C. Mitchell
Lawrence R. Smith
Sinkhole ponds in the Shenandoah Valley Sinkhole Pond (SVSP) system are found along the bases of western-facing slopes of the Blue Ridge Mountains in Virginia, and extend from Augusta County north to Page County, a distance of approximately 89 km. These ponds exist in colluvial and alluvial terrace deposits that consist of poorly sorted Antietam quartzite cobbles and boulders in a loosely compacted matrix of sand, silt, and clay that have been eroded from the slopes of the mountains (Duffy, 1991; Kochel, 1987; 1992; Whittecar & Duffy, 1992). These deposits can be from 100 to 500 feet thick (Hack, 1965) and lie over a thick section of relatively weak, westward-dipping carbonate limestone strata of Cambro-Ordovician age. Solution of the valley floor limestone underneath results in the formation of sinkholes; accumulated clay layers and the alluvial deposits sometimes form impermeable layers that enable the sinkholes to retain water. Age estimates for the alluvial fan deposits based on soil profiles support an early to late Pleistocene age (Whittecar & Duffy, 1992). Pollen profiles from the bottom sediments of one of the ponds (Spring Pond) indicate that the ponds have existed for over 15,000 years (Craig, 1969). Due to different hydrologies, some of the sinkhole ponds may have ground water connections, while others fill from surface runoff. The range in hydroperiod includes permanent to highly ephemeral ponds.
SREL Reprint #2412
Buhlmann, K.A., J.C. Mitchell, and L.R. Smith. 1999. Descriptive ecology of the Shenandoah Valley sinkhole pond system in Virginia. Banisteria 13:23-51.