The role of base level, watershed attribute and sediment accumulation in the landscape and tectonic evolution of the Circum-Tibetan Plateau Basin and Orogen System

Abstract

The India-Asia collision produces the outstanding Circum-Tibetan Plateau Basin and Orogen System. In this study, we systemically analyze and discuss the relationship between isostasy, base level and sedimentary process in the landscape and tectonic evolution of the Circum-Tibetan Plateau Basin and Orogen System. Considering of isostatic effects, the basin-filling processes can individually lead to the subsidence of the sedimentary floor, bringing numerous geological implications. On the conditions of ideal geological models and isostatic equilibrium, the sedimentary surface of the exorheic basins with strong hydrodynamic condition is constrained by sea level through the river longitudinal profile, and crustal thinning processes of the non-flexural exorheic basins can be sculpted by sedimentary records when the source supply keeps sufficient. Long-term and large-scale rising and dropping of the sea level can influence the subsidence rate of the extensional exorheic basins. On the other hand, the endorheic basins are of individual base levels, and isostatic effects of the sedimentary loading can lead to the uplift of the sedimentary surface. In this situation, the uplift process of the endorheic basins can be estimated by sedimentary records. Regional reorganization of river watersheds can lead to a series of geological impacts, such as the changing of base level, the redistribution of loose deposits, beginning or end of depositional discontinuity and fluctuation of the sedimentary floor. Thus, the geological implications for the changing of the sedimentary rates and the depositional discontinuity should be carefully identified in the landscape and tectonic evolution of the Circum-Tibetan Plateau Basin and Orogen System.