Abstract - We describe the structure and kinematics of a listric growth fault from SE Asia, using high-resolution, 3-D seismic data. The hangingwall rollover shows systematic changes in geometry that are sympathetic with along-strike changes in the nature of the basal detachment fault. Where the basal detachment maintained a constant, listric geometry throughout extension, the hangingwall rollover and associated growth faults show limited, progressive migration towards the bounding detachment fault. Along strike, however, we recognise three phases of footwall collapse caused by backstepping of the basal detachment into the footwall block. The available data are consistent with footwall collapse having been controlled by either (a) segment linkage and breaching within a major relay zone and / or (b) the rise and narrowing of a mobile shale diapir in the footwall block. Deformation above the backstepping detachment was characterised by punctuated migration of the rollover axis and associated growth faults towards the footwall, arising from each phase of footwall collapse. Since the migration of hangingwall structures is similar to that predicted by simple analogue models with fixed detachment surfaces, care should be taken in defining kinematic models in areas where the geometry of the bounding fault is either poorly defined or unknown.
Abstract of talk given to:
Irish Geological Research Meeting, Coleraine, February 2001