Study On Sequence Lithofacies Palaeogeography Of Ediacaran In Sichuan Basin And Its Adjacent Areas

Ediacaran stratum in Sichuan Basin is one of deep carbonate reservoir explorationfocus. With the oil-gas exploration and development, wealth of new drilling data andseismic data, early knowledge about lithofacies palaeogeography of Ediacaran inSichuan Basin and its adjacent areas urgent need to improve.So this thesis focuses onEdiacaran stratum system, depositiona system characteristic, sequence stratigraphy,characteristic and evolution of sequence lithofacies paleogeographic and reservoircharacteristic within sequence framework in Sichuan Basin and its adjacent areas,which can provide some exploration proofs. Several achievements have gained asfollow:Guided by the theories of sedimentology and the work methods of lithofaciespaleog-eographic, and based on measurement of main field geologicalsections,observation of su-pplementary field geological sections and data of drilling,according to types of rock, co-mbination of rock, section character and sedimentarystructure, four depositional systems are distinguished in Ediacaran of study area, theyare coastal depositional system, carbonate platform depositional system, platformBasin depositional system and shelf de-positional system, meanwhile the depositionalfacies, subfacies and microfacies were divided.After detailedly study on Ediacaran sequence boundary characteristic and genesistypes in Sichuan Basin and its surrounding, the sequence boundaries, paleocrust ofweathering, atmospheric water effect surface, lithology and lithofacies transitionalsurface and maximum flooding surface, were identified. Based on the sequenceboundary identify cation, Carboniferous can be divided into2super sequence and8third-order sequence, the system tracts and sequence characteristic of each supersequence and third-order sequence were carefully discussed, and the third-ordersequence was contrasted in study area,then establishment of a full-basin sequence stratigraphic framework in Ediacaran.Taking system tracts of super sequence as compilation unit, Ediacaran tectonic-Sequence lithofacies paleogeographic in Sichuan Basin and its adjacent areas weredrew. SS1supersequences corresponding to Doushantuoian of the early Ediacaran.After Nantuoian, paleoclimate in from the cold into a warm phase of degelaciation.Inthe Sichuan Basin and its adjacent areas, due to the formation of transgression typeclastic sedimentary transgressive, dolomite and phosphate rock, etc., paleogeographicpattern with high and low-lying areas west of the eastern region, the shallow water inthe western region and the eastern region of distribution of deep. SS2supersequencescorresponding to Dengyingian of the late Ediacaran. Because of the relative sea levelrise, to further expand the scope of waters, land area of narrow, Luding ancient landhave been inundated. Middle of Yunnan, Motian and other ancient land is not onlynarrow, but is no longer available terrigenous sediment. Dolomite of restrictedplatform is the main sediment in study areas. Paleogeographic studies has been takingby Deng1+2section, Deng3section and Deng4section shows deep-water deep-watershelf sediment of nearly north-south.On the basis of the above research，prototype basin of Dengyingian wasrerstored, the results showed that: Dengying formation was most serious denuded innorthwestern Sichuan Basin, Deng4and Deng3were almost completely denuded andThe northwest margin of the basin to become uplift. Meanwhile in the central basin,forming a ancient highlands at Well Moshen-1to chongqing. As a center, thesurroundding terrain in order to reduce, resulting in Well Woshen-1, Well Gongshen-1at Southwestern basin became the lowest-lying place and Palaeogeomorphologydepression.