The Cambrian-ordovician Sequence Stratigraphic Framework And Sedimentary Model In The Middle-upper Yangtze Area

Based on the theory of sequence stratigraphy,this article systematically analyzes the lithology and sedimentary sequence development characteristics of typical outcrop profiles on the premise of fully investigating related research results of previous people.Oxygen isotopes,rock flake analysis,and comprehensive sequence analysis of typical drilling,logging,and earthquakes.Perform isochronous comparison and sequence division of Cambrian-Ordovician outcrop-logging-seismic sedimentary strata in the middle-upper Yangtze region to establish The sequence stratigraphic framework provides an important basis for restoring the paleogeographic climate environment.Under the established sequence stratigraphic framework,the characteristics and main controlling factors of the sedimentary facies of the Cambrian-Ordovician in different periods in the study area are analyzed,and their depositional models are studied.The Cambrian in the middle-upper Yangtze region is divided into 6 regionally comparable tertiary sequences,and the Ordovician is divided into 8 regionally comparable tertiary sequences.By comparing the all-rock carbon isotope cycle that reflects the relative change in global sea level with the sedimentary cycle that reflects the relative change in sedimentary paleo-water depth,the analysis reveals that in the background of paleoclimate and sedimentary filling rate,the sequence is cold in the middle-upper Yangtze region.The development of the Armenian sequence CSQ1—CSQ4 and the sequence CSQ6 is controlled by global sea level changes,and the development of the sequence CSQ5 is controlled by regional tectonic movements;the development of the lower Ordovician sequence OSQ1 is mainly controlled by global sea level changes.The development of sequence OSQ2—sequence OSQ8 is mainly controlled by regional tectonic movement,that is,the squeezing tectonic effect produced by the subduction and convergence of the Yangtze plate to the Huaxia plate,which belongs to the more typical foreland compression sequence.The study proposes that the type of the Cambrian-Ordovician carbonate platforms in the Middle-Upper Yangtze area evolved into: carbonates with gentle slopes(early and early Cambrian)-carbonate borders(late Early Cambrian-early Early Pottery)—carbonate gentle slope platform(early and middle Middle Ordovician)—submerged platform(late Middle Ordovician—late Ordovician).