CLASTIC CAVE SEDIMENT ANALYSIS IN AN URBAN KARST SYSTEM

Sediment deposition in caves has focused on chemically deposited features with extensive climatic records. Less research has been done to study clastic sediments, which may contain evidence for Holocene environmental changes. Such changes may be indicated by the physical and chemical nature of the sediments. Clastic cave sediments consist of sediment derived from outside the cave (allochthonous) or sediment derived from breakdown material within the cave (autochthonous). This study investigates clastic sediments in Capshaw Cave, which is formed in Mississippian limestone on the East Highland Rim of Tennessee. The Capshaw Cave system drains the urban watershed of Cookeville, Tennessee, making it an ideal cave for studying human impacts on cave sediments. Sediments were collected from small fluvial terraces 1 to 2 m above the modern cave stream, and examined for particle size, mineralogy, and heavy metals. Results show that fluvial terraces throughout the cave consist of rhythmic sand and clay layers, probably the result of varying flood levels. Clay layers ranged in thickness from 2 to 10 cm, while sand layers averaged less than 2 cm. Grain size analysis of sand layers show normal distributions with mean sizes ranging from 2.25 phi to 3.25 phi. Chemical signatures in clay layers provide indicators for anthropogenic activity in the watershed, especially urbanization. Damage to cave ecosystems will be long lasting, and management of affected sediments will be difficult.