PRELIMINARY ASSESSMENT OF WATERFALL TRAVERTINE AND CALCITE OVERGROWTHS ON PLANTS AND TERRESTRIAL AQUATIC SNAILS FROM STREAMS NEAR CHECHEM HA CAVE, BELIZE, CENTRAL AMERICA

The geology of the Chechem Ha Cave region of the Maya Mountains (Cayo District, Western Belize) consists of Late Paleozoic steeply inclined metasedimentary shale, siltstone, slate, and phyllite (Santa Rosa Group) unconformably overlain by Late Cretaceous massive carbonates with well-developed karst. Streams that eventually empty into the Rio Mopan differentially erode through the carbonates, becoming supersaturated with carbonate, and produce temporary base levels on the underlying Paleozoic units resulting in an escarpment with waterfalls that drop over 60 meters. Thick accumulations of laminated travertine mark positions along the escarpment where past and present streams occur. Rate of travertine crystallization is extremely rapid and often encases plants, including large living trees, resulting in accumulations over one meter thick. Living aquatic snails of an as yet unidentified species become thickly encrusted with layered calcite that is often 3 to 5 times as thick as the shell itself. Carbonate growth usually completely envelops the shell up to the aperture. The snails appear to be unaffected by the excess shell weight and thrive in the streams. The waterfall travertine can be explained by turbulence driving off CO2 facilitating travertine crystallization around the waterfall; however, many of the snails live above the waterfall in quiet stream pools. Shell overgrowths may enhance snail survival by strengthening the shell, providing camouflage, or reducing risk of predation birds. The mechanism of carbonate overgrowth on living snails remains unknown.