Ruth E. Gilpin1, Nancye H. Dawers2
(1) University of Edinburgh, Edinburgh, Scotland
(2) Tulane University, New Orleans, LA
ABSTRACT: Interactions between Normal Fault Growth and Drainage Development: Insights from the Volcanic Tableland, Owen's Valley, California
Field study of a series of channels through a normal fault array on the surface of the Volcanic Tableland, eastern California, shows abundant evidence of interaction between fault growth and channel development. The channels (0.5 - 12 m wide) incise up to 15 m into the surface of the Late Pleistocene Bishop Tuff. Detailed field mapping, using a GPS with centimetre accuracy, a high resolution DEM and 1:10 000 topographic maps, was combined with a previous fault displacement survey (Dawers and Anders 1995).
Many features of normal fault development - footwall uplift, lateral propagation, interaction between faults, ramp deformation and segment linkage - are all clearly recorded in the drainage patterns and in the channel morphologies themselves. We show field examples highlighting the responses of both lateral and axial drainage systems to normal fault growth: through channel deflection, splitting, bedrock incision and knickpoint migration.
Sediment input to the evolving hangingwall basin is seen to vary drastically in both amount and location as faults evolve. Importantly, some sediment supply pathways fail to follow the predictions of current tectonic models.
The variations in morphology and sediment supply also demonstrate that the channel systems have been influenced by other controls, in particular glacial climate cycles and lithological features of the Bishop Tuff. A clearer picture of the interaction between all these factors, and the processes by which the fluvial system responds, is central to the understanding of drainage development and sediment supply both here and in other extensional basins.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado