Monday, August 19, 2013

Highlights—Alluvial Dryland Systems: Listen to Modder

Alluvial deposits have provided valuable insights into hydroclimatic variability and paleoenvironments, yet, in dryland settings, the roles of allogenic and autogenic processes are poorly constrained.  Tooth et al. investigate the controls on the genesis, sedimentary architecture and preservation potential of the alluvial succession along the modern incising Modder River, located in the tectonically stable South African interior far beyond the range of sea level influence.  The results show that whereas allogenic factors may be the primary driver of river activity in inland valleys, resistant rock barriers can exert additional complicating influences—stable barriers control the depth of cutting during climatically-driven incisional phases, but once partial or complete barrier breaching occurs, deep channel incision into bedrock will take place in reaches upstream, thus forming prominent valley-base erosion surfaces and possibly promoting the formation of incised gully networks. These findings are interpreted to provide insights that can be applied to improved interpretation of comparable dry, inland alluvial valleys preserved in the geological record.

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