Coupled 3D
Landscape and Sedimentary Numerical Modelling of Along-Strike Variability in
Hangingwall Stratigraphy Caused by Fault Displacement and Sea-Level Cycles
Finch, Emma1, Rob Gawthorpe1
(1)
We apply a three-dimensional model of
landscape evolution and clastic sedimentation to investigate the effect of
normal fault displacement and cyclic sea-level change on the along-strike
variability of depositional sequences in rift basins. Sediment is eroded from the
hinterland through a stream-power incision law and deposited in the basin using
a modified diffusion algorithm. During the initial stages, erosion of the
hinterland is driven purely by fault displacement, resulting in streams with
the greatest incision and headward erosion being observed at the location of
maximum fault displacement with less noted at the fault tips. Accommodation
space is greatest at the centre of fault, however, so the progradation of
deltas into the basin is generally greater towards the tips. A cyclic sea-level
change is then introduced using a sinusoid with varying amplitude and
wavelength, permitting investigation of the effects of relative ‘fast' and
‘slow' changes in accommodation space. In most cases, the initial sea-level
fall results in incision across existing deltas, more rapid incision in the
footwall is noted with greater rates of displacement and sea-level change.
During sea-level fall, capture of existing channel networks from previously
isolated streams is not uncommon. The stratigraphy developed during sea-level
rise is strongly influenced by the incised valley system developed during the
preceding fall. These models show that important controls on the along-strike
variability of stratigraphy associated with displacement on normal faults can
be caused by both the rate and amplitude of relative sea-level change and
sediment supply from evolving drainage networks.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California