The Division And Comparison And Study On Sedimentary Characteristics Of The Lower Carboniferous Heishantou Formation In The Balikun Area, Xinjiang

The Carboniferous strata exposed widely, with lots of folds and fractures tectonic in theBalikun area of Xingjiang; this dissertation is object on the sedimentary stratum of EarlyCarboniferous in this area, which is occurred between the north of Balikuntage southern faultmargin and the southwest of Baidunzi fault. In this area, Early Carboniferous volcanic rockshave complex lithology, various lithofacies types and changing environment, following morestratigraphic system unit for a long time, so the Lower Carboniferous stratigraphic division inthe Balikun area is not uniform. Via regional rock and biostratigraphy stratigraphiccorrelations, combining the rock assemblages, biological fossils, primary structure, grain sizeanalysis, and basic stratigraphy sequence, we gained the achievements as follows:1.On the basis of the previous stratigraphic division history， by makinggeological-section and the main route, as well as regional rock and biostratigraphystratigraphic correlations, we adopt the Heishantou Formation of stratigraphic area of northernXinjiang as the lithostratigraphic units of this strata and divided it into two sections.2. There is slight dispute of the Heishantou Formation, some of the formation has beenclassified as the Early-Middle Devonian strata. This dissertation collected previous data andcombined with the acquisition of a lot of fossils, which were consisted of brachiopoda,bivalve, foraminifera, bryozoan, gastropoda, coral, dragonflie, ostracode, cephalopod andntrilobite, atactotoechu, sporopollen and other fossils Brachiopoda includes Syringothyris sp.,Mucrospirifer sp., S.subgrandis Rotai, Spirifer sp., Gigantoproductus sp., Toryniferpseudolineatus asiaficus, Fusella sp., Echinoconchus elegans(McCoy), Nekhorsheviaheishatouensis F.M.Zhang; bivalve includes Parallelodon theciformis Koninck andPosidoniella vetusta (Sowerby); coral, includes Koninckophyllum chingshipuexse Fan,Yuanophyllum longiseptatum Yuetal. Fenestella cf.perelegans Meek, C.leiosomlla(Sardeson)and other fossils. the geologic period of this fossils all belong to the Early Carboniferous.Besides, the K-Ar isotopic age of volcanic rocks(andesite) in the Heishantou Formation is341.7Ma and324.4Ma, which is in accordance with stratigraphic contact relationship. So, thestratigraphic age can be defined as the Early Carboniferous.3. According to characteristics such as lithology, rock assemblages, biological assembly,basic stratigraphy analysis and primary structure, we know that it presented characters of frequent change and water unrest on the whole, when the Heishantou Formation deposited,and of coarse clastic sediments, such as conglomerate and coarse sandstone affected by wavesand floods in local regions. The carbonatite are exposed small in thickness, sometimes asntercalated bed or lenses status.The overall sedimentary environment of the HeishantouFormation is the littoral-neritic.