Abstract

Subsidence patterns resulting from differential sediment loading on a mobile substrate (e.g., salt) are an important process for the development of accommodation and stratigraphic architectures in intraslope minibasins. Numerous studies of minibasin systems have focused on either the tectonic processes involved in salt deformation or the stratigraphic interpretation of the sedimentary fill of minibasins. This study focuses on the coevolution of depositional and tectonic processes to investigate the response of substrate movement to minibasin sedimentation. Using a silicone polymer to model a viscous mobile substrate, a series of 2D experiments were conducted to explore the effects of variation in 1) sediment supply rate, 2) depositional style (intermittent sediment supply), and 3) the thickness of the deformable substrate on subsidence patterns and minibasin stratigraphic development. Experimental results indicate that larger initial thickness of salt substrate as well as lower sedimentation rates result in greater amounts of subsidence for a given amount of deposit. Furthermore, in the experiments with intermittent sediment supply, increasing subsidence rate was observed as sedimentation continued, while decreasing subsidence rate occurred once sedimentation ceased. These accelerations and decelerations in subsidence were attenuated as the total thickness of the minibasin deposit increased and the thickness of the remaining salt decreased. Lower sediment supply rate led to a narrower but deeper minibasin formation. The increase in overall time allowed the salt substrate to have a greater response to the overburden. In contrast, the linked depositional and tectonic processes caused higher sediment supply rate to increase the planform size of the minibasin. Based on the experimental results, a new model of autostratigraphic minibasin evolution is suggested: 1) differential loading causes initial subsidence, 2) ponded (basin infilling) architecture occurs during a period of acceleration in subsidence, and 3) perched (spilling) architecture occurs over the duration of final subsidence deceleration.