Using small scale sediment remobilisation features for determining subtle changes in palaeoslope evolution

Adriana del Pino Sanchez

University of Leeds

adriana@earth.leeds.ac.uk

Slumping and sliding of thick sediment packages has been recognised in seismic and outcrop data sets and sea floor surveys of continental margins. However, small-scale deformation such as development of asymmetry in dewatering structures, slump folding, and bed dissagregation alters both the grain scale and bed scale structure of sands, and indicate subtle changes in slope. These slope changes may precede larger scale development of heterogeneity through slope failure and subsequent emplacement of this failed material into basin lows. The consequent changes in bathymetry may also influence subsequent sediment distribution patterns. In subsurface scenarios this heterogeneity has implications for reservoir quality. Better understanding of these processes should offer reduced risk in hydrocarbon reservoir appraisal.

Mapped onlap relations and analysis of palaeocurrent indicators may be used to infer the position and gross orientation of a palaeoslope. However, the measurement of kinematic shear indicators acquired from measurement of slump folds, faults, and sand injection features which deformed on the slope may be more useful for inferring the detailed history of palaeoslope evolution. The Grès du Champsaur turbidite sequence forms part of the fill of the Tertiary foreland basin of SE France. The sediments were deposited in a deformed and deforming basin defined by thrusts and folds.

This poster reports preliminary findings in which quantitative field measurements are used to illustrate slope steepening.

Data has been acquired from small-scale soft sediment features (asymmetric dewatering and slumping) and related to estimations of palaeoslope both regionally and from palaeocurrent data sets acquired from the basin.