Stratigraphic Response of Variable Mini-Basin Subsidence Patterns Due to Autogenic Effects

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 mini-basin settings. While previous studies of mini-basin development have focused mainly on examining changes to the system arising from external forces (allogeneic processes), this study focuses on the relationship between stratigraphic architecture and internal dynamics of the system (autogenic processes). Using a silicone polymer to simulate a viscous mobile substrate, a series of simple two-dimensional experiments were conducted to explore the effects of variation in 1) sedimentation rate, 2) depositional style, and 3) changes in the thickness of the deformable layers on salt deformation. These experiments serve as an analogue model for mini-basin formation and sought to capture the internal dynamics of the system. Autogenic processes were isolated by maintaining constant sediment feed rates, as well as using a specified total amount of sediment for each run regardless of the runtime. Quantification of results has allowed greater understanding of the mini-basin development associated with internal dynamics in salt deformation.

Experimental results have shown a lag time in the response of the salt material to sediment load. This lag is the time in which the salt responds to each pulse of sedimentation. During phases of constant sedimentation the rate of subsidence of the mini-basin approaches steady state. However, once sedimentation stops, subsidence of the basin undergoes a deceleration until a new steady state subsidence pattern is reached. Likewise, when sedimentation restarts, the mini-basin undergoes a phase of accelerating subsidence rate until the salt substrate re-equilibrates to the increasing load and steady state subsidence is again reached. The autogenic acceleration and deceleration of the substrate to the changing load likely plays a significant role in the stratigraphic architecture of the associated basin infill. Interpretation of mini-basin fill stratigraphy is re-evaluated based on new understanding of these variable subsidence patterns.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California