Responses of Gravity Flow Deposits to Base-Level Variation in Rift Basin using a case study of Lower Teng1 formation in South Wuliyasitai Sag

Abstract: In gravity depositional area although the sediment grain-size cycle cannot reflect the base-level changes, the flow condition characteristic and type of gravity flow have an apparent response to the landform. Based... [ view full abstract ]

Abstract: In gravity depositional area although the sediment grain-size cycle cannot reflect the base-level changes, the flow condition characteristic and type of gravity flow have an apparent response to the landform. Based on this response, our study discusses how to investigate the base level variation in gravity depositional area. An increase of dip slip rate of the syn-sedimentary fault that made slope breaks of Teng 1 formation, southern Wuliyast sag, was investigated by pale geomorphic reconstruction and analysis of strata thickness. Because of the increase of dip slip rate, the landform of study area switched from flat to steep, and the base level rises. Within the process, the flow condition characteristic and deposition location of gravity flow show a regular changes observed by core observation and 3-D seismic inversion: turbidity current developed and deposited on the bottom part of slope break, as well as weak cohesive debris during the dip slip rate of the syn-sedimentary faults was high, which led to a steep landform and high creation rate of accommodation; while in the phase of low dip slip rate which results in flat landform and low creation rate of accommodation, debris developed and deposited wildly on the flat slope. Consequently, our research suggests that the landform variation can be confirmed by the changes of flow regime and type of gravity deposition, and then the situation of base level variation can be investigated in rift basin.