Controls from the Dimensions and Architecture of Late Pleitocene Submarine Lobes off East Corsica
Mark Deptuck1, David
Piper2, Bruno Savoye3, and Anne Gervais4
1Canada_Nova Scotia Offshore Petroleum Board, Halifax, NS, Canada
2Geological Survey of Canada Atlantic, Dartmouth, NS, Canada
3Ifremer, Plouzané, France
4DGO, Bordeaux 1 University, Bordeaux, France
Sandy lobes on submarine fans are sensitive recorders of the types of sediment gravity flows supplied to a basin and are economically important as hydrocarbon reservoirs. Off East Corsica, a wide range of lobe bodies were mapped and measured using a tightly spaced grid of ultra-high resolution boomer profiles. Repeated crossings of lobe bodies were used to measure spatial changes in thickness, width, cross-sectional area, and stratigraphic architecture. Most lobes increase abruptly down-slope to a peak thickness of 8 to 42 m, beyond which they typically show a more gradual decrease in thickness, thinning below seismic resolution or passing into drape on the basin plain. Lobe areas range from 3 to 70 km2 and total lengths from 2 to 14 km, with the locus of maximum sediment accumulation from 3 to 28 km from the shelf-break. Lobes vary from small, simple single-storey bodies to large complex multi-storey bodies. What accounts for this range in lobe location, dimensions and complexity? Flume tank experiments and numerical models show that variations in flow properties (e.g. volume, duration, grain size, sediment concentration, and velocity) influence the length, width, thickness and composition of lobe-building beds. Knowledge of sea level position, triggering mechanisms for flows, and sediment source character may help constrain flow properties. The final architecture of lobes constructed by multiple flows, however, also reflects several other interrelated factors including: a) the number/frequency of flows, and their variation through time, b) gradient change and seafloor morphology, c) lobe lifespan prior to avulsion or abandonment, and d) feeder channel geometry and stability. This talk will explore the factors important in controlling lobe location, dimensions and architecture, and the challenges in determining which factors are most important.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas