Morphometric analyses, sedimentology and geochronology of the discontinuous reaches of the Macquarie River indicate that the trunk stream was characterised by lateral migration in the mid-Holocene, with meanders and cut-offs developing until at least ~4.8 ka. More recently (since ~1 ka), low levees have developed over lateral migration features (e.g. scroll bars), reflecting a shift in the dominant style of channel adjustment from lateral to vertical accretion, with periodic avulsion. An upward-fining sediment sequence in a modern point bar also shows a transition to a lower-energy environment in the last ~0.8 ka. Avulsion appears to have increased the degree of longitudinal connectivity in the system by short-circuiting some reaches that were previously separated by channel breakdown and unchannelised wetlands. A pilot study using Uranium-series disequilibrium methods suggests a significant reduction in sediment residence time in the modern channel (58 ± 2 ka) compared with a meander cut-off (153 ± 5 ka) abandoned next to the trunk stream ~4.8 ka. These changes in channel morphology and processes of fluvial adjustment may be caused by a combination of local channel change and catchment-scale change in sediment dynamics and hydrology, and may be reflected in other rivers in the Murray-Darling Basin.
|Title of host publication||AQUA biennial meeting|
|Subtitle of host publication||program and abstracts|
|Publisher||Australasian Quaternary Association|
|Number of pages||1|
|Publication status||Published - 29 Jun 2014|
|Event||Australasian Quaternary Association (AQUA) biennial meeting 2014 - Mildura, Australia|
Duration: 29 Jun 2014 → 4 Jul 2014
|Conference||Australasian Quaternary Association (AQUA) biennial meeting 2014|
|Abbreviated title||AQUA 2014|
|Period||29/06/14 → 4/07/14|
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Wetlands in Drylands: conservation through environmental research, citizen science and global engagement
Tim Ralph (Participant)
Impact: Science impacts, Environment impacts, Policy impacts, Society impacts