Provenance Analysis Of The Paleogene Jidula Formation In Southern Tibet And Its Implication For Paleogeography

Gamba-Tingri is located in the South Asian belt of the Tethys Himalayas in southern Tibet.The whole distribution is at the same latitude,and the tectonic activity is single.The stratum is continuously integrated and contacted,which has less influence on the original horizon of the stratum,and The Zongpu Formation on the upper part is obviously denuded,but its contact relationship with the base blockage group is clear,which makes the formation of the base blockage group complete and continuous,and it is considered that the group represents the front delta to shoreline sediment.Although the predecessors have a general analysis of their sedimentary facies and provenance regions,they are not sufficient to reflect the local features of the northern coast of the Indian mainland and the overall horizontal distribution.The two measured sections used in this time are located in the section of the blockage of the Dingpupu thermal mountain base in Tibet and 2 km of the west of Gangba County.Pull group profile,on the basis of sedimentary facies analysis,sandstone petrography,paleocurrent,heavy mineral combination and U-Pb The geological chronology method of detrital zircons analyzes the location of the source-blocking zone of each location and its sedimentary environment at the same time,and determines the trend of its source change by comparing the lithological changes of the upper and lower groups,in order to finally understand the northern margin of India.The evolutionary history and the closure process of the entire Neo-Tethys ocean provide evidence of sedimentology.From the results of sedimentary facies analysis,the plate belonging to the early Guxingangba area is the passive continental margin of India,and the latitude of the area is similar.It is on the same coastline of the Neo-Tethys Ocean.The shore phase is dominant and the same sedimentary response to the sea retreat.Shows a change from a shallow sea to a continental shelf.From the results of sandstone petrography,in the Paleocene,the terrigenous clastics of the base block were mainly quartz sandstones with very high maturity,and considering the direction of the ancient water flow nearNNE-SSW,it can be considered as the base plugging.The group of basalt volcanic rock fragments can only come from the Deccan Plateau.The sandstone characteristics of Tingri and Gamba are inconsistent.The purity of Gamba quartz is higher,and it is mainly supported by particles.The purity of Tingri quartz is lower,and the support of heterogeneous base is the main.From the analysis results of the detrital zircon chronology data,it can be seen that the two have the same source,which is consistent with the Degan basalt eruption of the early Cretaceous.During the Early Paleocene,the deposition of the Jidula Formation did not involve Asian sources.Therefore,it is speculated that the New Tethys Ocean has not completely disappeared at the time,and the northern edge of India has not exchanged with Asian sources.