Lateral variability in strain along the toewall of a mass transport deposit: a case study from the Makassar Strait, offshore Indonesia

Contractional features characterize the toe domain of mass transport deposits. Their frontal geometry is typically classified as frontally confined or frontally emergent. However, it remains unclear how the style of frontal emplacement and contractional strain within a mass transport deposit vary along-strike. We use bathymetry and 3D seismic reflection data to investigate the lateral variability of frontal emplacement and strain within the toe domain of the Haya Slide in the Makassar Strait, offshore Indonesia. The slide originated from an anticline flank collapse and the toe domain is characterized by a radial fold-thrust belt that reflects southwestwards emplacement. The frontal geometry of the slide changes laterally. It is frontally confined in the south and is associated with a deep, c. 200m b.s.f. planar basal shear surface. The frontal geometry gradually changes to frontally emergent in the west, associated with a shallow, c. 120m b.s.f., c. 3 degrees NE-dipping basal shear surface. Strain analysis shows c. 8-14% shortening, with the cumulative throw of the thrusts increasing along-strike westwards from c. 20-40 to c. 40-80m. We show that even minor horizontal translation of mass transport deposits (c. 1km) can result in marked lateral variability in the frontal geometry and strain within the failed body, which may influence their seal potential in petroleum systems.