Application Of Markov Chain Simulation In The Jiyang Depression

Jiyang Depression is a Mesozoic-Cenozoic superimposed basin that based on Pre-Mesozoic basement, Thus, the Cenozoic tectonic setting and evolution becomes a hot topic in the research on the Bohai Bay Basins.Strong cyclic strata (field data from flysch rhythmic sequences of middle Triassic in the Nanpanjiang Basin) and weak cyclic strata (data from five wells in the north slope of Dongying Sag) were used in the simulation in this paper. The Markov chain simulation method is mainly used to create transition probability matrices, limit probability matrices, circulation matrices and replacement analysis. The author found and named the cyclic chain and the secondary cyclic chain. State cycle mode charts were gained by the computer simulation, modes of different locations and different cycles were established as well.According to sedimentary structures, as to the strong cycle strata, the relationship between rhythmic structures and sedimentary environments was established. While as to the weak cycle strata, according to the lithological column, the relationship between the mode of the cycles and the sedimentary enviroments was compared. It is confirmed that the water-body alternated from shallow to deep and then shallow during the Eogene, the sediment facies could be divided into two cycles upward,ie the group of fan-delta plain, fan delta front and frontal fan delta subfacies to the group of near shore subequeos fan facies, lacustrine facies and slump turbidite facies, then the former to the near shore subequeos fan facies, delta front and fan plain subfacies. The basin was expanding and the depocenter was moving to southward all the time. Jiyang Depression was stretching, with the regime of"faults in the north, overlap in the south", in the whole Paleogene.There is a close relationship between the changes of the provenance and the tectonic setting evolution in Jiyang Depression, because tectonic setting always control the provenance of sedimentary basins.Apart from markov chain simulation on the sedimentary strata, QFL (Q-quartz, F-feldspar, L-lithics) diagrams were used to aid the analyis of the different provenances and tectonic settings of Jiyang Depression, As a part of North China Basin, Jiyang Depression also evolved from part of a flat area in the Late Paleozoic to a continental depression with uneven surfaces.