--> Climatically Controlled Lacustrine Clinoforms: Theoretical and Modeling Results

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Climatically Controlled Lacustrine Clinoforms: Theoretical and Modeling Results

Abstract

Lake basins and their deposits, common throughout earth history, are good paleoclimate recorders and contain rich hydrocarbon resources. Shelf-slope clinoforms, better known for the stratigraphy of deep marine basins, are also present in deep lake basins but they evolve differently from those in the marine basins due to a strong correlation between the river-derived sediment supply (sediment and water discharge) and lake level. We use empirical relationships to calculate the sediment and water discharge from the rivers as well as the time-equivalent lake level during wet-dry cycles at 10s Ky time scale. We then input the calculated values of sediment discharge and lake level into stratigraphic forward models to understand how the lacustrine clinoform develops under different conditions. The results show that during the dry period with decreasing sediment supply and falling lake level, the shelf margin trajectory is flat, but that there is limited deep-water sediment transport to the basin floor. During the wet period, the increasing sediment supply from rivers is coeval with rising lake level, and creates highly aggradational shelf, progradational shelf-edge margin, and also thick bottomset deposits. This resulting clinoform model is very different from that of marine basins where the flat shelf-margin trajectory is commonly associated with strong shelf by-pass and the presence of thick, sandy deep-water fan deposits. The climatically controlled lacustrine clinoform model documented by numerical model is also observed in ancient lakes such as Neogene Lake Pannon in Pannonian Basin. Because the numerical model can be run under different parameter conditions, the clinoform geometries modelled can be employed for inverse analysis to estimate the paleo-climate conditions for a given basin.