PLUNGE POOLS AND PALEOPRECIPITATION

Sedimentary sequences in the form of ridges or terraces surrounding pl unge pools at the base of waterfalls can provide records of past disch arge and as a consequence an indirect measure of rainfall variations o ver many thousands of years. Waves generated by the waterfall deposit sands and pebbles as a beach at the perimeter of the plunge pool. As c limatic conditions change, plunge pools expand and contract, leaving t hese beaches as relic sedimentary deposits. The first sedimentary sequ ence of this kind to be analyzed for records of Quaternary climate cha nges is in Kakadu National Park, Northern Territory, Australia. Tempor ally, this record correlates closely with other paleoclimate proxies o n both the Australian and African continents as well as the Indian sub continent. The stratigraphic data indicate that this part of northern Australia was much wetter during the early to mid-Holocene (approximat ely 10-5 ka) and also during the last glacial maximum (approximately 2 2-18 ka). These pluvial periods are attributed to a strengthening of t he northwest monsoon despite a considerably lower sea level during the last glacial maximum.