Caves as sources of biotic remains in arid western North America

Abstract

Caves have been a valuable source of paleoenvironmental information since the eighteenth century. In arid portions of western North America, caves have replaced small lakes as the primary source of biotic remains of Quaternary age. Packrat middens, dung of extinct animals, pollen, and archeological artifacts are excellently preserved. Aridity of the sediment, which is influenced by the cave's topographic position, internal morphology, and the regional climate, is the primary cause of good preservation. For stratigraphic pollen analysis, the best sites are those without internal moisture sources and without extensive bioturbation. Pollen samples should be taken near the center of the chamber, where eolian deposition is most rapid. Pollen concentrations in cave sediment are lower (2000–355,000 grains g −1) than in lake sediment, and pollen percentages in cave sediment differ from those in packrat middens due to additional transport mechanisms (on plant tissue and on the packrats themselves) for middens. Pollen diagrams for Bechan Cave, Utah, and Organ Pipe Cactus National Monument, Arizona are presented as examples of cave sediment and packrat midden analysis.