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Bedrock structural control on catchment-scale connectivity and alluvial fan processes, High Atlas Mountains, Morocco

By
Anne E. Mather
Anne E. Mather
School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, Devon PL4 8AA, UK
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Martin Stokes
Martin Stokes
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Published:
January 01, 2018

Abstract

Lithology is acknowledged to be an important internal catchment control on flow processes to adjacent alluvial fans. However, the role of inherited structural configurations (e.g. bedrock attitude) in catchment connectivity and sediment transport is rarely considered. We examine four young (<100-year-old) active tributary junction alluvial fan systems from the Dadès Valley in the High Atlas of Morocco in terms of their catchment-scale connectivity, sediment transfer and resulting alluvial fan processes. The catchments occur on the same lithologies (limestones and interbedded mudstones), but experience different passive structural configurations (tilted and structurally thickened beds). The fan systems react differently to historical peak discharges (20–172 m3 s−1). Catchments containing tectonically thickened limestone units develop slot canyons, which compartmentalize the catchment by acting as barriers to sediment transfer, encouraging lower sediment to water flows on the fans. Syn-dip catchments boost connectivity and sediment delivery from translational bedrock landslides as a result of steep channel gradients, encouraging higher sediment to water flows. By contrast, translational landslides in strike-oriented drainages disrupt longitudinal connectivity by constricting the valley width, while the gradients of the main channels are supressed by the attitude of the limestone beds, encouraging localized backfilling. This diminishes the sediment to water content of the resulting flows.

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Contents

Geological Society, London, Special Publications

Geology and Geomorphology of Alluvial and Fluvial Fans: Terrestrial and Planetary Perspectives
CONTAINS OPEN ACCESS

D. Ventra
D. Ventra
Utrecht University, the Netherlands
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L. E. Clarke
L. E. Clarke
University of Gloucestershire, UK
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Geological Society of London
Volume
440
ISBN electronic:
9781786203809
Publication date:
January 01, 2018

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