CONTROLS ON SHELFSTONE DISTRIBUTION, LOWER CAVE, CARLSBAD CAVERN, NEW MEXICO: PRELIMINARY RESULTS

Cave pools are a common feature on the floor of Carlsbad Cavern, Carlsbad Caverns National Park, New Mexico. A total of seventeen pool areas (21 individual pools) were described in Lower Cave, an area of the cave that sits under the better-known Big Room. The pools studied are primarily fossil pools that are now dry or have water levels too low for active addition to their shelfstone. Shelfstone is a speleothem that grows from the edge of a cave pool out over the pool surface at the air-water interface, thus marking paleo-pool levels for fossil pools. Although shelfstone is fairly common, few studies specifically address its origin or distribution.

Of the 21 pools described, 13 have some form of shelfstone. The most common form is the basic, continuous shelf, usually with a scalloped leading edge. Upturned lips sometimes occur facing upstream at the spill point of the pool. Less commonly, the shelfstone was discontinuous lily pads or irregular bowl shapes, both of which have strongly upturned edges.

The limited data set hinders efforts to determine the controlling factors on shelfstone precipitation. However, we observed several possibly significant relationships. First, shelfstone only occurred where the edge of the pool was steep. Second, an average depth of at least 20 cm seemed necessary to form shelfstone. Third, pool crust knobs with crystal sizes >1 mm are associated with shelfstone. Lastly, our data indicate that deeper waters support longer shelfstone even when the pool area is relatively small. This study will help focus our continuing effort to understand shelfstone.