DEEP LACUSTRINE SEDIMENTARY FILLS IN MULTI-SEGMENT RIFT BASINS: INSIGHTS FROM 3D FORWARD MODELING

The development of deep lacustrine facies and associated sedimentary fills in rift basins is subject to various factors, including tectonics, climate, lake-level fluctuations, and sediment supply. However the effects of these factors are nonlinear and not simply superposed. Although conceptual stratigraphic models of rift basins provide useful insights into basin stratigraphy and facies architecture, this approach may not address the full range of possible controls and the uncertainties in the quantification of controlling processes. Stratigraphic forward modeling provides a practical and effective method of addressing this problem by (1) exploring and including more of the variables that may control rift-basin sedimentation and (2) considering multiple scenarios to determine the influence of uncertainty and parameter values. Nevertheless, previous stratigraphic forward models rarely integrate the basin and extrabasinal sources holistically, and accordingly may underestimate the complexity of real-world processes. In this study, state-of-the-art commercial stratigraphic modeling software, Dionisos, was utilized to carry out modeling tests on sedimentary fills in oblique, multi-segment rift basins. What is distinct in our approach is that it is a deterministic, nonlinear-diffusion based sediment transportation model, and connects the basin fill with the erosion of the extrabasinal catchment area. We consider a range of parameters that affect basin infilling, from the site of erosion in the source area to deposition deep in the basin, and compare a series of models to help determine how sensitive the fills of deep lacustrine facies are to some of the variables, such as precipitation, erosion rate of source area, and tectonic subsidence of the rift. Among other results, the model shows how (1) both extremely arid and humid conditions are not favorable for the development of deep lacustrine facies in rift basins, and (2) an increase of basin subsidence rate or a decrease of erosion rate at the source area increases the proportional volume of deep-lacustrine sediment contained in the total lacustrine sediment volume. Use of such forward models can enhance the prediction of economic resources in rift basins.