Physical Modeling of a Prograding Delta on a Mobile Substrate

Abstract

Subsurface architecture of a delta that progrades on a mobile substrate (e.g., salt) is a product of complex interplay between depositional process and subsidence. Previous studies mostly focused on structural deformation of a salt layer in response to tectonic forcing, and left the dynamic feedback between sedimentation and subsidence unexplored. We present results from physical experiments of delta progradation on a mobile substrate. Five carefully designed experiments were performed to understand the effects of delta progradation rate on the shape and dimension of salt deformation and associated stratal architecture. All of the runs had constant sediment and water discharge, but the mobile substrate thickness and water depth varied from 2 cm to 4 cm and from 1 cm to 3 cm, respectively. The results showed that the deeper the water depth, the slower the shoreline progradation rate, while the thinner the salt thickness, the faster the delta progradation. The experimental results also provided data over a wide range of shoreline advance and subsidence rates enough to indicate changes in shape and dimension of salt deformation structure. Runs with fast shoreline progradation showed isolated salt domes developed internally into the delta plain and a rough planform pattern in the shoreline due to lobes built by channels flow between upwelled salt structures. However, runs with slow shoreline progradation developed connected long salt ridges around the toe of the delta, limiting sediment to transport beyond the ridges. This overall pattern in salt structures is time dependent. As a delta surface grows larger and the shoreline progradational rate autogenically decreases with time, chances to develop isolated salt domes decrease but more connected long salt ridges occur. The insight from the physical modeling of a delta on a mobile substrate is important to predict the mechanism for large-scale salt basin stratigraphy under a high sediment supply that interact with the substrate actively.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016