In Situ Soft Sediment Deformation Structures in the Tanqua Depocentre, Karoo Basin, South Africa: A Statistical Approach to Understanding Processes and Products

Oliveira, Carlos M. M.¹, David M. Hodgson², Stephen S. Flint² (1) University of Liverpool, Liverpool, United Kingdom (2) University of Liverpool,

Intense deformation of sediments can occur without significant down-slope remobilisation. Morphological criteria for identification of in situ deformation styles across different length scales can help to improve interpretation of "chaotic deposits", commonly identified on seismic datasets. The products of intense in situ deformation processes (dewatering) are well preserved in Permian slope deposits of the Tanqua Depocentre, Karoo Basin, South Africa, which have been the focus of statistical analysis to identify relationships between different morphological parameters that occur over several orders of magnitude.

Methodology included the measurement of geometrical aspects (e. g. width:height, orientation, distance between adjacent structures) from  200 dewatering features at 8 specific intervals in lower to upper slope deposits. Simple statistical analyses were undertaken to verify the level of correlation, the scale factor and the linearity among the discrete parameters.

The results indicate a strong correlation between pairs of certain attributes, including the vertical extension of one structure and the distance to the adjacent one and the internal relations between the horizontal and vertical dimensions inside each single feature. These correlations hold for deformation features from 0.05 to 5m in amplitude, in a depositional environment from lower to upper slope. The orientation of the elongated "break through flame" structures, perpendicular to the local palaeo-slope, suggests a genetic relationship with the filling of adjacent channel complexes. From this study we can conclude that some styles of soft sediment deformation are predictable at different scales, which will aid subsurface prediction.