Martinsen, Ole1, Trond Lien2
(1) Norsk Hydro Research Centre, N-5020 Bergen, Norway
(2) Norsk Hydro ASA, Bergen, Norway
ABSTRACT: Slope Facies Models Revisited: Is There A Unique Classification Scheme?
Deep-water slopes are key elements of subaqueous depositional profiles because they link shallow-water source and staging areas to deep-water sediment sinks. Still, slopes are to date not characterized by representative facies models and vary significantly in depositional style from basin to basin. If a general classification is searched, one based on cross-sectional dip architecture may be favourable because it captures highly different facies variability rather than focusing on few, only locally important processes.
Slopes can broadly be characterized as either (i) progradational, (ii) aggradational or (iii) degradational, depending on sediment supply, tectonic activity and sea level history. These three different types can vary both in time and space and have different dominant facies and lithologies. Progradational slopes tend to be more mud prone because they imply deposition dominated by suspension, while aggradational slopes in many cases are sand prone because they imply bypass of upslope areas, lowered sea level and deposition from gravity flows in lower slope areas. Degradational slopes include those with canyons and where there are actively mobile substrata such as salt and clays. They are commonly dominated by erosion and mass wasting such as debris flows, slumping and sliding and can have mixed lithologies. However, turbidity current deposits can be trapped in canyons and in local topography with locally high sand potential. A number of examples are shown from several Atlantic margin basins to illustrate processes, facies and architectural variability of various deep-water slopes.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.