Abstract

Sedimentary sequences in the form of ridges or terraces surrounding plunge pools at the base of waterfalls can provide records of past discharge and as a consequence an indirect measure of rainfall variations over many thousands of years. Waves generated by the waterfall deposit sands and pebbles as a beach at the perimeter of the plunge pool. As climatic conditions change, plunge pools expand and contract, leaving these beaches as relic sedimentary deposits. The first sedimentary sequence of this kind to be analyzed for records of Quaternary climate changes is in Kakadu National Park, Northern Territory, Australia. Temporally, this record correlates closely with other paleoclimate proxies on both the Australian and African continents as well as the Indian subcontinent. The stratigraphic data indicate that this part of northern Australia was much wetter during the early to mid-Holocene (∼10-5 ka) and also during the last glacial maximum (∼22-18 ka). These pluvial periods are attributed to a strengthening of the northwest monsoon despite a considerably lower sea level during the last glacial maximum.

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