Tectonic and climatic controls on asymmetric half-graben sedimentation: Inferences from 3-D numerical modeling

Abstract

The tectono-sedimentary evolution of asymmetric extensional systems driven by the activity of major normal faults or detachments associated with footwall exhumation is often characterized by a sequence of slower, faster, and ultimately again slower subsidence rates in the center of hanging wall half-grabens during their synkinematic and postkinematic evolution. We have studied this specific evolution by the means of 3-D stratigraphic numerical modeling that accounts for the variability of the sediment and water flux combined with climatic and sea level variations, and sediment compaction. The model setup is constrained by observations from the Pannonian back-arc basin of central Europe. Our modeling predicts the formation of low-order tectonic and higher-order sea level and climate-driven transgressive-regressive sedimentary cycles. Furthermore, we model and analyze the autocyclic nature of the depositional systems. Retrograding-prograding cycles are visible on the proximal flank of the half-grabens by their different spatial and temporal expressions, while depocenters record large water depth variations linked to the specific and episodic activity of normal faults and their migration with time. The application to a system of multiple half-grabens in the Pannonian Basin, which are activated in different locations, at different times and with different kinematics, demonstrates a complex interplay between direct sediment sourcing and the sediments' ability to bypass trapping subbasins and paleo-reliefs created by eroded footwalls.