Deirdre C Commins1, Sanjeev Gupta1, Joseph A. Cartwright2
(1) Imperial College, London, United Kingdom
(2) Cardiff University, Cardiff, United Kingdom
ABSTRACT: Fluvial Response to Faulting: Insights into the Growth History of Normal Fault
Arrays using Geomorphic Criteria
Late Quaternary-Holocene fluvial systems in the Canyonlands Grabens, Utah, have been dramatically altered by the growth of normal fault
segments that formed as a result of gravity gliding above a ductile salt layer. Analysis of
fault
displacement variations and geomorphic features (e.g., windgaps, waterfalls) permit reconstruction of the growth history of multi-segment
fault
arrays.
We present data from a fault
array that comprises two linked paleo-segments. The presence of an abandoned ('breached') relay ramp in the hangingwall of the linked faults indicates the position of a paleo-
fault
tip prior to hard linkage taking place.
The displacement profile of the fault
is characterised by linear tip gradients, with zero displacement at the tips increasing uniformly to a maximum of 27m near the centre of the
fault
. The displacement profile approximates that of an ideal isolated
fault
. The presence of ~11m of post breaching displacement suggests that the
fault
accrued a significant amount of displacement for its new length, in order to attain this ideal profile.
A stream that traverses the footwall of the fault
exhibits a waterfall at the
fault
trace that separates two graded sections. The height of the waterfall corresponds to the post-breaching displacement of the
fault
. We propose that the waterfall formed as a result of rapid displacement addition following hard linkage. The formation of the waterfall indicates that post-linkage displacement accumulation is relatively rapid. Analysis of stream profiles in conjunction with
fault
displacement data thus enables reconstruction of the evolution of
fault
arrays and the relative timing of displacement accumulation.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado