Stratigraphic Characteristics And Sedimentary Evolution Of Late Cretaceous And Paleogene In North Junggar Basin

Jungger Basin is a very important petroliferous basin of our country. There are controversies about stratigraphic classification and sedimentary characteristics of late Cretaceous and Paleogene in north Junggar Basin for a long time, which influces the further exploration of this area. This article is based on sedimentology, palaeobiology and lithofacies paleogeography. Stratigraphy classification, identification and characteristics of sedimentary facies, evolution of sedimentary environment and paleoclimate has been made by the process of field geological investigation and measuring profile, analysis and identification of microfossil samples, grading analysis samples and geochemical samples.Based on extensive strata tracking, microfossil samples identification, stable carbon and oxygen isotopes samples analysising, we have divided the strata of late Cretaceous and Paleogene in north Junggar Basin into four formations, including Ailikehu formation(K2a), Honglishan formation(K2h), Wulunguhe formation(E1-3w), Suosuoquan formation(E3-N1s).Through integrated study of sedimentary facies indicators, thin-section identification and grain size analysis, four kinds of sedimentary facies were identified: alluvial fan facies, river facies, lake facies and aeolian facies. River facies were the main sedimentary facies of Ailikehu formation and Wulunguhe formation, lake facies and lake facies were the main facies of Honglishan formation. Meanwhile, alluvial fan facies and Aeolian facies were the main types of Suosuoquan formation.Paleoenvironment and paleoclimate analysis show that climate were heat and drought during the depositional period of Ailikehu formation and Honglishan formation. The weather became wet and the amount of runoff increased during the depositional period of Wulunguhe formation and lower part of Suosuoquan formation. It became cold and drought owing to the uplifts of the Qinghai-Tibet Plateau, atmosphere circulation evolutions, retreating westward of Tethys during the depositional period of upper part of Suosuoquan formation.