Remobilisation Processes on
the Submarine Slope: is the Degree of Deformation a Reliable Criteria for
Transport Distance
Van der Merwe, Willem C.1, David M. Hodgson2,
Steve Flint1 (1) Liverpool University,
Mass transport deposits (MTDs) are often identified in subsurface and seabed
datasets, which can provide useful information on deposit bulk volume and
spatial distribution. However, limited information on internal facies, architecture and transport distances exists. A rare
example of deepwater kilometre-scale MTDs at outcrop is the Vischkuil
Formation,
Detailed analysis of a single 50 m thick
MTD, which is continuously exposed for 2 km down-dip at the Rietfontein
locality was undertaken to understand the internal architecture and emplacement
processes. In proximal localities the stratigraphic
interval is undeformed. However, down-dip clastic dykes and low-angle shear surfaces are common
indicating extensional movement where associated sediments have undergone
ductile deformation at different scales. Further down-dip the
orientation of the extensional shear surfaces spoon round and ramp-up under a compressional regime (mimicking ramp faulting).
Above, and associated with the major compressional
planes are large (10's metres amplitude) folds. The
whole stratigraphic exposure at Rietfontein
is unique in preserving the evolution of a slump from undeformed,
through extensional (evacuating zone) to a compressional
toe zone. This study also highlights that an intense zone of soft sediment
deformation can develop over a short displacement distance.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California