Late Quaternary Alluviation Along Intermittent Streams in Kakadu National Park, Northern Territory
Abstract:Sedimentation along small, intermittent streams on Kapalga Research Station in Kakadu National Park may have responded to increased base levels following post-glacial flooding of the valleys of the Alligator Rivers. Alternatively, regional climate changes may have controlled sedimentation. Using thermoluminescence dating, we determined that sediments from two streams at Kapalga date from 21.5 ± 4.0 ka. On a third stream, sediments dated from 7.6 ± 1.1 ka, with younger sediments occurring downstream. We interpreted the pre-Holocene dates and the lack of evidence of upstream progradation to indicate that climate variation was more important to sedimentation than base levels. Predicted increases in rainfall variability and in the frequency of high-intensity rainfall under enhanced greenhouse conditions may cause renewed sediment mobilisation. At the outflow of one stream on to the South Alligator flood plain, we found 15 m of sandy alluvia underlying 3-5 m of estuarine muds deposited as a result of sea-level rise. These sandy alluvia dated from about 77 ka at 4 m to more than 300 ka at 19 m depth. These ages are consistent with those recorded on the Magela Creek system, 50 km to the east.
Document Type: Research Article
Affiliations: CSIRO Tropical Ecosystems Research Centre, Australia; University of Wollongong, Australia
Publication date: July 1, 2000