THE MORPHOLOGY, SPELEOGENESIS, AND CLASSIFICATION OF CAVE TURNIPS IN LEHMAN CAVES, GREAT BASIN NATIONAL PARK, NEVADA

Lehman Caves is a two-mile-long cave system in the northern portion of Great Basin National Park. Formed ~10-2 Ma within the Middle Cambrian Pole Canyon Limestone, Lehman Caves exhibits a ramiform pattern because of its hypogenic speleogenesis and prolific fracture sets. The cave contains numerous rooms and a variety of identified speleothems. This research focuses on cave turnips, a globally rare speleothem that occurs in abundance in Lehman Caves, and works to determine their overall morphology, speleogenesis, and relationship to other cave features.

Cave turnips were investigated through spatial mapping and morphologic measuring in each room studied. In situ photographs of turnips and their relationship to other features were documented. Two cave turnips, on loan from the National Park Service, were uranium-thorium age-dated. This work proposes a new size classification system based on four morphologic measurements taken on over 500 in situ turnips. The length, width at base, width at center, and width at tip were summed for each turnip, and this designates its size classification: micro-turnip (<200 mm), meso-turnip (200-349 mm), or macro-turnip (≥350 mm). In addition, the presence/absence of condensation corrosion and the proximity of the basal attachment to ceiling, fractures, or cave shields were noted for each turnip.

Results show that 42% are micro-turnips, 45% are meso-turnips, and 13% are macro-turnips. Approximately 40% of all turnips are corroded, and micro-turnips dominate this fraction (50%). About 65% of meso-turnips and 76% of macro-turnips are not corroded. The majority of micro-turnips (57%) form along fractures; the majority of meso-(59%) and macro-turnips (68%) form along the ceiling. From this data, we infer that condensation corrosion is more likely to occur in smaller turnips. Because micro-turnips most likely form along fractures, we interpret the fractures have more condensation formation, causing increased corrosion during micro-turnip speleogenesis.

Documenting cave turnips in Lehman Caves is important, as the cave system preserves these globally rare speleothems. Lehman’s abundant turnips allow for a new size classification based on morphological characteristics, in addition to advancing the preservation, education, and inspiration mission of the National Park Service.