Abstract

There is a need for better tools in the interpretation of depositional sub-environments of deep-marine facies. Using seismic-scale outcrops of Eocene shelf-margin clinoforms in Spitsbergen, we have statistically characterized the turbidite beds in terms of grain size, bed thickness, and dominant sedimentary structure at four different lowstand sites in individual, mappable clinoforms. These sub-environments include: (1) upper-slope canyon and gully fill, (2) upper to middle-slope late prograding wedge, (3) lower-slope channel–levee complex, and (4) basin-floor fan.

The falling-stage basin-floor fan and slope canyon/gully deposits are generally coarser grained than the rising-stage sub-environments. They also have far fewer siltstone and mudstone beds and have significantly more beds of upper-medium to very coarse grain size compared to the rising-stage channel–levee and prograding-wedge deposits. Thin beds are particularly voluminous in the late prograding-wedge and channel–levee systems, whereas only the basin-floor fans and canyon fill have large numbers of beds thicker than 10 cm.

Turbidity currents deposit sediment at distinctly different sites between shelf edge and basin floor at different times during the development of the base-level cycle. Differences between these sub-environments are both qualitative and quantitative and are demonstrable using statistical analysis. The results of this statistical analysis from well-exposed, easily identifiable architectural elements can be used to reconstruct the shelf margins of analogous basins, where only sparse outcrop or well data are available.

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