(16) Coevolution of minibasin subsidence and sedimentation: Experiments

From Stratodynamics

Author

Wonsuck Kim1

1Department of Geological Sciences and Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78712, USA

delta@jsg.utexas.edu

Abstract

Differential loading induced deformation of a mobile substrate (e.g., salt tectonics) is an important process for the development of accommodation space and stratigraphic architectures in intra-slope minibasins. Numerous studies of minibasin systems have focused on either the tectonic processes involved in salt body deformation or the stratigraphic interpretation of the sediment deposits filled in minibasins. However, this study focuses on coevolution of depositional and tectonic processes to investigate the link between tectonic evolution and the stratigraphic patterns. 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) sedimentation rate, 2) depositional style (intermittent sediment supply), and 3) the thickness of the deformable salt substrate on subsidence patterns and minibasin stratigraphic development. Experimental results indicated that larger initial thickness of salt substrate as well as lower sedimentation rate caused greater amounts of subsidence for a given amount of deposit. Furthermore, increase in subsidence rate was observed as sedimentation continued, while decrease in subsidence rate occurred once sedimentation ceased. These acceleration and deceleration of subsidence were attenuated even with sediment supply event cycles of the same magnitude. Due to these linked depositional and tectonic processes, higher sediment supply resulted in relatively slower subsidence of the depositional center for given sedimentation and thus increased the planform size of minibasin, whereas lower sediment supply sedimentation led to a narrow minibasin formation because relatively longer time allowed for salt substrate to respond to the overburdened minibasin deposit.