The Paleogene And Neogene Strata In The Northern Margin Area Of Tengger Desert

The thesis studys on the Paleogene and Neogene strata which distribute in AlxaLeft Banner and Alxa Right Banner of Inner Mongolian Autonomous Region, and alittle southwest zone belongs in Minqin County, Gansu Province in administrativedivisions, and belongs to Alxa stratigraphic area in tectonic units.Based on the detailed study of former research achievements, this paper uses thetheory of Lithostratigraphy, Biostratigraphy and Sedimentology as a guide, and relyon modern analysis and testing techniques to analyze the results of field geologicalsurvey, measured section, animal and pollen fossils which are eventually serve tostudy the strata of Paleogene and Neogene in the study area. The distribution of thePaleogene and Neogene strata are as follows: apart from the Paleocene, the Eocene,Oligocene, Miocene and Pliocene strata are development, but with distributedscattered, and outcrop is poor, mainly concentrated in southern Alxa stratigraphicdivision. This thesis also studies facies of the strata from lithologic characters andsedimentary constructions that they are widely developed rift lake basins at that time,and mainly lacustrine and fluvio-lacustrine deposits. Finally, confirming thelithostratigraphic units and geological age of each section by contradistinction anddivision of each section’s lithostratigraphic and paleontological strata, and thenestablish the stratigraphic sequence of the Paleogene and Neogene strata of the studyarea: Sikouzi Formation,Eocene（E₂s）, Qingshuiying Formation, Oligocene（E₃q）,Hongliugou Formation, Miocene（N₁h）, Kuquan Formation, Pliocene（N₂k）. Amongthese, there exist an angular unconformity between Sikouzi Formation and itsunderlying the Cretaceous or older strata. And the contact relationship betweenHongliugou Formation and Qingshuiying Formation is parallel unconformity, KuquanFormation, unconformably cover Hongliugou Formation, overlying the Quaternarystrata.