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Pool-fills: a window to palaeoflood history and response in bedrock-confined rivers.
- Source :
-
Sedimentology . Oct2004, Vol. 51 Issue 5, p901-925. 25p. - Publication Year :
- 2004
-
Abstract
- Channel-scale sedimentary units associated with bedrock-controlled riffle-pool morphology are examined in detail along Sandy Creek gorge, an ephemeral stream in arid south-eastern central Australia. Pool-fills comprise cut-and-fill assemblages of poorly sorted sediments ranging in texture from muds to boulders. Five unit types are defined based on particle size, sedimentary structures, geometry and bounding surface character: (1) coarse-grained bar platform; (2) fine-grained bar supraplatform; (3) fine-grained pool-fill; (4) fine-grained bench; and (5) modern pool-fill. The last coarse-grained unit currently lining the pools suggests an altered sedimentation style over the post-settlement period (post-ad 1860s). Situated at bedrock valley constrictions, pool-fills are compared with other sedimentary units associated with recirculating currents: eddy bars and slackwater deposits. But only the fine-grained bench units reflect eddy recirculation; the pool-fills are principally forced-bars associated with bedrock-controlled or‘forced’ riffle-pool morphology. A late Holocene palaeoflood history is proposed based on radiocarbon ages from the pool-fills: multiple phases of cut-and-fill activity were preceded by a superflood 3400–1900 years ago that eroded the pool-fills to bedrock. The resilience of the pool-fills was illustrated by the passage of a 1-in-100-year flood in 1992, which caused only minor erosion. The presence of pool-fills may provide a window to past phases of river activity that cannot be extracted from either historical records/observations or palaeoflood slackwater sediment analyses. The formation and sedimentary preservation potential of these landforms reflect a combination of hydraulic and structural influences, but the occurrence of high-magnitude floods exerts the dominant control. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00370746
- Volume :
- 51
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- Sedimentology
- Publication Type :
- Academic Journal
- Accession number :
- 14454258
- Full Text :
- https://doi.org/10.1111/j.1365-3091.2004.00643.x