| To corresponding, International Commission proposed new division scheme on Stratigraphy Precambrian, Late Precambrian and related working groups of experts re-divide the late Proterozoic Department in December1999the formation of the Third National Conference preparatory meeting. Under the original Aurora system contains a set of moraine rock formations to build another new series, suggested that it be named "South lines", this resolution is adopted in the Third National Conference preparatory meeting Formation.At present, the definition Presinian Nanhua System has become unified,but each region’s older Nanhua strata, buried deep, outcrop distribution limitations, low level of research, lithological composition of complex,a series of formation group name,lateral variation in lithology and thickness,so research in stratigraphic division and stratigraphic distribution is still not mature enough. In addition, since the1960s Weiyuan gas field discovery, experts in various branches of oil and gas, oil universities and research institutes carried out fruitful research on Sinian strata in terms of natural gas exploration, the trend which is oil and gas exploration to expand more ancient formations makes research on Nanhua strata more important.On the basis of previous research investigation, according to the South China strata outcropping, studied33South sectional in each cell of the study area, Nanhua strata outcropping is found in the periphery of the Sichuan Basin multi-zone.In different region,choosed10profiles which are geological outcropping complete, outcrop good, simple structure, stratigraphic boundaries clear,strong signs, comparability are actually measured.On the basis of field data obtained, the stratigraphic distribution of the entire study area Nanhua system is identified by researching, analyzing, contrasting region, selecting the most suitable area, establishing stereotype. The various stratigraphic units and structural features which is obtained by observation and measurement analyzes sedimentary strata phase and lithofacies paleogeography. The distribution of dark mudstone, holes around the layer and fracture cases are initially proved in the formation of the study area. The main access to the following understanding:l)According to the international stratigraphic division programs, geological age of the Nanhua System is780～635Ma, stratigraphic division should use the three-point plan.Nanhua system is divided into Nantuo (on glacial deposition), Fu Lu group (interglacial deposition) and Changan group (under glacial deposition) in the light of the practice of stratigraphic division scheme.,Sichuan Basin periphery of the missing strata can be compared with Chang’an Group under glacial’s. 2) The junction of Hunan, Guangxi, Guizhou is the most complete record of the region in Sichuan Basin periphery of the Nanhua System,division scheme of which is applied to establishing standard profile of the Sichuan Basin periphery of the Nanhua System, the bottom-up into Liantuo segment, the ancient city section, Datangpo Section South Da group, equivalent to only international stratigraphic division on glacial and interglacial program. Recommend selecting Guizhou Zunyi six urns An Duoding sectional complemented well profile Nantuo segment is a standard profile of the Sichuan Basin periphery of the Nanhua System.3)The study area is divided into four facies association and distinguished eight categories facies types on the basis of ancient tectonic setting and sedimentary filling special analysis.Identified the distribution of lithofacies paleogeography in the various stratigraphic units of the Sichuan Basin periphery of the Nanhua System bases on analusis of the sedimentary environment in the sub-district.4) Datangpo segment Nanhua System Nanhua System is the only possible source rocks, and Nantuo, Liantuo segment and volcanic rocks of western Sichuan can be used as reservoirs bed. |
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