SEDIMENTARY RECORD OF AN ABANDONED UNDERGROUND LAKE, SCOTT HOLLOW CAVE, MONROE COUNTY, WEST VIRGINIA

Scott Hollow Cave is a >50 km conduit system developed in Mississippian age limestones of the Appalachian Plateau, southeastern West Virginia. The cave has a modified dendritic pattern, and conducts water from a extensive karst upland to springs on the Greenbrier River. Recharge occurs through sinkholes and swallets. One of the major branches of the cave, Chris's Trunk, terminates upstream at a sediment choked blind valley. Known parts of the Trunk no longer carry substantial water, but do hold numerous deposits of alluvial clastic sediment. At one location, an abandoned lake deposit with an area of ~300 square meters is found. We investigated this deposit in order to understand the processes that led to formation and abandonment of the lake, and to reveal the processes responsible for filling the cave. Analysis included mapping of the deposit, construction of stratigraphic columns (5 profiles in cave & 2 profiles on the surface), and collection of layer samples (35 in cave & 12 on the surface) for magnetic, grains size, and mineralogical examination. Magnetic studies include paleomagnetic (directional) and environmental magnetic (ARM, IRM, SIRM, etc.) parameters

The lake sediments terminate downstream against a deposit of massive ceiling breakdown, and it appears that this breakdown created a dam that was responsible for the lake. The sediments form two flat-topped terraces, with a difference in elevation of ~1 m. Depositional relationships show this sequence of events: Growth of the cave passage in bedrock, massive breakdown causing damming of drainage, filling of the lake with sediment forming the upper terrace, breaching of the breakdown dam, fluvial erosion of the upper terrace, reoccurrence of damming, filling of the lake and formation of the lower terrace, breaching of the dam (below), fluvial incision of the lower terrace (and additional erosion of the upper terrace). Sediment sizes vary from clay to cobble. Bedding is relatively continuous and horizontal, though some channel structures are seen. Mineralogy of pebble and larger size clasts appear to reflect both the surface drainage basin and upstream erosion within the cave. Many of the larger clasts are chert derived from residual soils. The deposit reveals a complex history of infill and cutting caused by local and possibly regional conditions.