Cannibalisation
of a Submarine Channel-Levee System by an Entrenched Submarine Channel System
in the Laingsburg Depocentre,
Hodgson, David M.1,
Rufus L. Brunt2, Claudio Di Celma1, Stephen Flint1,
John.
P. Kavanagh1 (1) University of Liverpool, Liverpool, United Kingdom
(2) Liverpool University, Liverpool, United Kingdom
Kilometres-wide submarine slope channel
systems are commonly imaged on seismic and modern datasets. Exposure quality
commonly precludes the identification and detailed facies analysis of systems
of this scale at outcrop. In the Laingsburg
At the axis of the Unit C channel system
there is >30m of incision into mudstones. Adjacent thin-bedded and
fine-grained deposits thin and fine away from the axis of the channel system,
and are interpreted as 8km-wide constructional levees. Mapping and logging
demonstrates that the Unit C system is cannibalised by the Unit D system. The
fill of the >80m deep, asymmetric composite incision surface is dominated by
thin-bedded low net:gross turbidites.
In both channel systems, older channel-
and channel complex-fills contain slumps and basal mudstone clast
conglomerates, whereas younger channel-fills are sand-prone and tabular. The
majority of remnant erosion surfaces identified in Unit C and D display a
westward stepping trend, such that the westernmost channel complexes represent
the last phase of cut-and-fill. This study has led to the detailed assessment
of the erosional and depositional history of two different but juxtaposed
channel systems. The distribution of channel-fill facies will help to reduce
uncertainties in slope channel reservoir exploration and production.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California