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Evolution Of Sequence-filling And Tectono-lithofacies Paleogeography From Late Jurassic Through Neogene In Sichuan Basin

Posted on:2011-04-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:G C YangFull Text:PDF
GTID:1220360302993028Subject:Mineral prospecting and exploration
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In the framework of lithostratigraphy, biostratigraphy and chronostratigraphy, based on the theories and methods of sedimentology, High-resolution sequence stratigraphy, sequence-filling dynamics, lithofacies palaeogeography and geochemistry, and the tectono-sequence analysis method, the depositional system and sedimentary models, the sequence stratigraphy and isochronous stratigraphic framework, palaeocurrent characteristics and provenance attributes were researched systematically from Upper Jurassic through Neogene in the Sichuan basin. Furthermore, the evolution of palaeogeography and sequence-filling, and the basin-mountain coupling relationships and basin evolution in this period were deeply discussed. To sum up, the main achievements obtained are as follows.1. Through analyzing the previous data, and on the basis of field geological surveys in Sichuan basin and its surrounding, the stratigraphic division scheme of lithostratigraphy and biostratigraphy from Late Jurassic through Neogene were put forward, and at the same time the stratigraphic regionalization and strata correlation relationship were redefined.2. Based on the sedimentological and high-resolution sequence stratigraphic study of field outcrop sections, drilling/well logging and seismic data, the strata from Upper Jurassic through Neogene in Sichuan basin were mainly divided into nine types of depositional systems and seven sedimentation models, and were subdivided into three first-order ( tectonic ) sequences, five ( second-order ) tectonic sequences, nine super sequences and fifteen ( third-order ) sequences in accordance with the genetic types of different-level sequence boundaries. And then the high-resolution sequence stratigraphic frameworks of different sections in the basin were established in which sequences were taken as correlation units and super sequences or tectonic sequences as correlation thickness.3. The properties and tectonic settings of provenances, and the characteristics of sedimentary environments from Late late-Jurassic through Cretaceous in the basin were discussed on element geochemical analysis of argillaceous rocks and carbon-oxygen isotopic analysis of carbonate gravels. And the element geochemical analysis results of argillaceous rocks show that during that time, it totally had a freshwater environment with low-level salinization and warm-wet climatic conditions in Sichuan basin, a sedimentary environmental model characterized by overall oxidation and local deoxidation was suggested for the argillaceous rocks, source rocks are mainly sedimentary rocks and granitic rocks, and the tectonic setting of provenances for argillaceous rocks is mainly continental island arc and partly passive continental margin.4. According to a great deal of data of measured palaeocurrents, statistical conglomerate gravels and clastic compositions of sandstones, the basin paleogeographic migrations and evolution of provenance from Late Jurassic through Neogene were analyzed in detail. The Lower Cretaceous palaeocurrent changes indicate that there had a continuous course of palaeocurrent inversion in central Sichuan basin during Early Cretaceous, which characteristics were that in time it happened earlier in the north than in the south, and with regards to the impact strength on the basin sedimentation, it was stronger in the north than in the south.5. On the basis of comprehensive subdivision of lithofacies and sequence stratigraphy, combined with related documentary achievements, and with tectonic sequences or super sequences being taken as mapping units, the basin palaeogeography in the frameworks of different tectonic cycles was constructed, which revealed the transpositions of depocenters, the time-space distribution and evolution of depositional systems in Sichuan basin from Late Jurassic through Neogene.6. On the basis of systematical studies on the sedimentary facies, sequence stratigraphy and regionally tectonic geology, and guided by related theories and methods of basin-filling dynamics, the macro modes of basinal sequence-filling for different sections were built up. Afterwards in conjunction with the regionally tectonic evolution, with supersequences and tectonic sequences being regarded as the analytical units, the tectono-sequence analysis method was used to probe deeply into the characteristics of basinal lithofacies-filling, basin-mountain coupling and basin evolution in nature from Late Jurassic through Neogene as for Sichuan basin.
Keywords/Search Tags:sedimentary facies, sequence stratigraphy, basin evolution, Sichuan basin, Upper Jurassic through Neogene
PDF Full Text Request
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