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.
Controls on the genesis, sedimentaryarchitecture, and preservation potential of alluvial successions instable continental interiors: insights from the incising Modder River, SouthAfrica by Stephen
Tooth, P. John Hancox, Dion Brandt, Terence S. McCarthy, Zenobia Jacobs, and
Stephan Woodborne
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