%0 Journal Article
%A Benito, Gerardo
%A Sánchez Moya, Yolanda
%A Sopeña, Alfonso
%T Sedimentology of high-stage flood deposits of the Tagus River, Central Spain
%D 2003
%@ 0037-0738
%U https://hdl.handle.net/20.500.14352/112592
%X This paper details the sedimentology of high-stage flood deposits, with the definition of sedimentary environments and theircharacteristic sequences, along two bedrock reaches of the Tagus River (Central Spain). High-stage flood deposits accumulatedin bedrock canyons include slackwater flood deposits (SWD) and other types of deposits located at flow separation zones andassociated with slow-moving flow (<1 m s 1). These flood deposits are common indirect indicators of flood stages used inpalaeoflood studies for estimating the discharges associated with Quaternary floods. Depositional environments of flooddeposits include (1) channel widening, (2) canyon expansion, (3) bedrock obstacles, and (4) backflooded areas along tributarystreams. These flood deposits can be found associated with other non-fluvial environments, namely aeolian reworked and slopewashflow facies. Channel widening, due to flood stage variations, comprises internal and external zones of the channel margins,and their characteristic sequences contain similar facies to those of alluvial floodplains. Canyon expansion environments favourvertical accretion of slackwater units and the development of flood deposit benches, which contain four sequences related tobench elevation and distance from the channel’s main thread of flow. At the lee side of bedrock obstacles, characteristicsedimentary sequences are dominated by reverse flow structures (e.g. climbing ripples migrating upstream) due to eddies with ahigh sand concentration. Flood deposits located within tributary mouths contain typical sequences of reworked floodplaindeposits. Backflooding of tributaries during flood stages produces deposition from suspension of sand, silt and clay within threesequences characterised by non-structure or parallel lamination and intense bioturbation. A better understanding of the flooddeposit sequences may contribute to the characterisation of flood magnitudes and flood hydraulics and can also be applied tosome ancient depositional environments.
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