Print this pageThe Development of Incised Valleys in a Three-Dimensional 
Numerical
Model
of Deltaic Deposition
Emma Finch1, Stuart Hardy2, and Rob
Gawthorpe2
1 Manchester University, Manchester, United Kingdom
2 Universitat de Barcelona, 08028 Barcelona, Spain
We apply a three-dimensional model
of clastic sedimentation and erosion
to investigate the effect of sea level change and sediment supply on the
development of incised valleys in a deltaic environment. Sediment is introduced
at a point source and allowed to deposit into the basin while a constant sea
level is maintained, developing a major incised channel. Sea level is then
varied according to a sinusoid with varying amplitudes. As sea level falls,
incision occurs, resulting in a three-dimensional incised valley network
developing across the delta front. Results generally illustrate two stages of
network development, i) a proto-incised valley stage where many small valley
networks distribute sediment relatively uniformly along the delta front and ii)
a main incised valley stage where one or more valleys develop by headward
erosion and capture most of the sediment supply. Sediment supplied from the main
channel is continually deposited during this stage, but can be captured by the
headward erosion of neighbouring channels causing avulsion, and redirection of
sediment in the basin. There can therefore be a large along strike variability
in the spatial distribution of these valleys and the associated amount of
sediment deposited. 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 nature of incised valleys are
i) the initial dimension of the delta, ii) the rate of sediment supply and iii)
the nature of relative sea level change.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005