Computer Simulation on the Formation of Depositional Sequences in Tectonic Active Basin: Case study on rift and foreland basins

Key words: 
• sequence simulation

Abstract: Using twodimensional sequence stratigraphy modeling system (SSMS), we carried out a research on simulation of the formation of depositional sequences in tectonic active basins, and has revealed the control of the interplay of syndepositional fault activity, lake level change and sediment supply on the formation of the depositional sequences. The simulation shows that fast tectonic subsidence rate, relatively high lake level and abundant sediment are the necessary condition for the formation of relatively deep water fan delta, and when the sediment supply decreases or the tectonic subsidence rate increases will generate favorably the near sublacustrine fans in a rift lacustrine basin. The paleogeomorphic slopebreak zone resulting from the syndepositional faulting along the steep basin margin of a rift basin, controls obviously the distribution of the lowstand turbidite fans and the depocenter of the delta front in TST and HST. The structural slopebreak is the key control factor on variation of accommodation space. In the edge of intracontinental foreland thrusting, the alluvial fan and fluvial deposits develop in the early stage and stack back as the result of rapid tectonic subsidence rate. Later the clastic systems move into the basin and form the widely distributed river delta deposits as subsidence rate decrease in the late period of a regional depositional cycle. The simulation shows that in this sequence the distribution of the lowstand systems tracts are mainly controlled by the structural slopebreak zones resulting from the hidden thrust faults. These LST sand bodies capped with TST mudstones many form significant lithostratigraphic traps. 