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Type: Journal article
Title: A terminal Last Glacial Maximum (LGM) loess-derived palaeoflood record from South Australia?
Author: Haberlah, D.
Williams, M.
Hill, S.
Halverson, G.
Glasby, P.
Citation: Quaternary International, 2007; 150:167-167
Publisher: Pergamon-Elsevier Science Ltd
Publisher Place: United Kingdom
Issue Date: 2007
ISSN: 1040-6182
Conference Name: Inqua Congress (17th : 2007 : Cairns, Australia)
Editor: Catto, N.
Statement of
Stanley H Ambrose, Martin A Williams, Umesh Chattopadhyaya, Jaganath N Pal, Parth Chauhan
Abstract: Late Pleistocene fine-grained valley-fill formations have been reported in the uplands of present-day desert margins, including the Great Escarpment of Namibia, the Sinai Peninsula of Egypt, the Matmata Hills of Tunisia, and the Flinders Ranges of South Australia. The valley-fills or Silts mantled the underlying irregular bedrock topography and now form gently sloping terraces incised by ephemeral traction-load streams. Their homogeneous silty texture and massive to crude horizontal bedding, with occasional fine laminations that can be traced laterally for tens of metres, have prompted a number of conflicting depositional models (Haberlah 2006, Reworked desert loess has been invoked as a source for these homogeneous Silts at all locations (Coudé-Gaussen et al., 1984 SGB 37:1050; Eitel et al., 2001 QI 76/77:57; Rögner et al., 2004 LNES 102:79; Williams and Nitschke, 2005 SAGJ 104:25). This realisation has major implications for their palaeoenvironmental interpretation. While most recent sedimentological studies suggest that the Silts represent loess-derived alluvium (Rögner et al., 2004, Srivastava et al., 2006 QR 65:478), their ages are still contested and for example range at the Homeb Silts stratigraphic type section in Namibia from LGM (Vogel, 1982 Palaeoecol Afr 15:201; Eitel and Zöller, 1996 MÖGG 137:245) to mid-Holocene (Bourke et al., 2003 QSR 22:1099). However, a chronostratigraphy based on 37 AMS 14C-ages and 7 OSL dates, exists for Silts in the Flinders Ranges (Williams et al., 2001 QI 83-85:129). New results from a continuous monolith 8m long obtained from the dated stratigraphic type locality of the Brachina Creek are presented. Hyperspectral mineralogical logging at 1cm intervals targeting alternating light- and dark-coloured bands are linked with results of Coulter Multisizer particle size and XRF/XRD analyses, suggesting slackwater deposition due to backflooding of a tributary mouth upstream of the loess-choked Brachina Gorge. Stable isotope and mollusc assemblage studies on carbonate shells are consistent with this model of palaeoflood deposition. Calibrated ¹⁴C-ages indicate three episodes of rapid aggradation at ~20.2 ka, ~19.4 ka and ~18.2 ka which, when compared with independent regional palaeoenvironmental proxy data, suggest early deglacial orographically enhanced frontal precipitation events causing rapid erosion of LGM loess slope mantles. Other occurrences of Silts can now be compared with these fine-resolution sedimentological studies and palaeoenvironmental data embedded in a well-established chronostratigraphy. The loess-derived palaeoflood record also sheds new light on palaeoclimatic processes operating in southern Australia during one of the most complex intervals of the late Pleistocene.
DOI: 10.1016/j.quaint.2007.04.001
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