Depositional Filling Characteristics Of Paleogene In Lanping Basin

Based on the depositional characteristics of paleogene in Lanping basin of the weatern Yunnan as the research object,use of theoretical knowledge in petrology, sedimentology,sedimentary geochemistry,integrated the geological research results of predecessors,through to the basin in different section sandstone on paleogene clastic composition characteristics,geochemical characteristics and particle size distribution characteristics were analyzed,studying on the filling charcaterisitcs and depositional environment of paleogene in Lanping basin.Mainly has the following understanding and conclusion:(1)Sandstone in paleogene clastic constituents analysis in the study area for the single crystal quartz types are mainly in quartz, mainly the stability of the potassium feldspar in feldspar tyre,the cutting type has sedimentary rocks+metamorphic rocks +(occasional)igneous rock cuttings, give priority to sedimentary rocks cuttings;the characteristics of the index will decrease in Yunlong formation�'Guolang formation�'Baoxiangsi formation sandstone;according to the Qt-F-L、Qm-F-Lt and QmP-K triangular diagram,source in the study area are derived mainly from continental sedimentary rock area; Qp-Lv-Ls triangular diagram shows the debris source components in the study area mainly on the Craton frontal collision suture and fold in the overthrust belt provenance.(2)Constant element characteristics points out that in the study area, clastic sediments in paleogene maturity in the study area is higher, rock samples is given priority to with feldspar sandstone; sandstone provenance is presented by the neutral igneous rocks provenance to mainland quartzose provenance evolution trend;the provenance of Yunlong formation is mainly from the east edge of the basin(continental island arc), stage to Guolang formation andBaoxiangsi formation has joined a basin west margin(passive continental margin) source,while the source of Baoxiangsi formation is mainly come from the west margin basin(passive continental margin).(3)Trace element characteristics show provenance material in the study area are mainly composed of felsic rocks quality, the depositional environment is the continental oxidizing environment, the source rocks is given priority to with sedimentary rocks, parent rock debris on the earth’s crust mainly comes from the mainland; the source has the characteristics of multiple period stage, early phase(Yunlong formation)is given priority to with continental island arc tectonic setting, late(Guolang formation)gradually transition to continental island arc + passive continental margin tectonic setting, especially by Baoxiangsi formation that temple period is mainly composed of passive continental margin tectonic regions provide source.(4)Sandstone probability cumulative grain size curves in paleogene in the study area mainly includes:”one bouncing population-lsuspension population-transitional zone”,”bisegment”;the size distribution of Paleogene sandstone indicates that sandstone in the study area of skewness values are between partial-very slant range, kurtosis is medium- sharp sharp category,sorting is good to very good;using structural parameters of scatter plot points and discriminant function to calculate determine the sandstone of Yunlong formation and Guolang formation representative fluvial facies,delta facies,lacustrine facies,Baoxiangsi formation sandstone is alluvial fan facies sedimentary.