Study On Jurassic-cretaceous Sedimentary Facies And Paleogeography In Henan Province

During the Jurassic-Cretaceous period, effected by the later stage of Indosinian orogeny and Yanshan movement, there are more than 30 of small intermountain depressions (fault) basins in Henan Province; it laid the foundation for fully studying the Jurassic-Cretaceous sedimentary facies and paleogeography. This paper has collected 25 drilling data of deposits in Jurassic-Cretaceous strata of concealed areas in the eastern Henan, measured 7 sections including outcrops of Jurassic in Jiyuan Basin, Upper Jurassic-Lower Cretaceous in mashiping Basin, Upper Cretaceous in Xixia Basin. Lots of first-hand field information has been collected in detail, including a large number of rock and fossil samples, especially trace fossils.After the rock samples observation under a microscope and particle size analysis in laboratory,and combined with knowledges of sedimentology and ichnology, it is clear that there mainly were continental sedimentary system,locally construction of the volcanic rock in Jurassic-Cretaceous period in Henan Province. Continental deposits in the study area have 4 kinds of sedimentary facies including alluvial fan, braided stream, meandering stream, shallow lake;and 4 kinds of sedimentary sub-facies including flood lakes, lake delta, deep lake turbidite and fan delta, and establish a depositional model of alluvial fan -fluvial -lacustrine system.14 genera and 21 species of trace fossils are described and identified in detail in the Early Jurassic strata in Jiyuan basin and Late Cretaceous strata in Xixia Basin. According to the occurrence features of trace fossils, and its relationship with sediments and sedimentary environment, the Anyao ichnocoenosis represented lake turbidite environment is established in Jiyuan basin; and the Beaconites-Palaeophycus ichnofabric generated in the fluvial environment and the Beaconites-Taenidium ichnofabric occurred in of lake environment are established in Xixia basin.With the thought of Structure-controlled Basin Evolution as the guide, follow the "Point - Line - Area" map compilation principle, a more comprehensive study to restore the tectonic, lithofacies palaeogeography has been finished in the area.During the Early - Middle Jurassic period, take Xichuan - Tongbai - XinXian - Shangcheng for the sector, the mountains in the South, highlands or plains in the north, mainly were fluvial and lacustrine facies; During the Late Jurassic - Early Cretaceous, the basin was a shape of narrow strip distribution, showing characteristics of significant strike-slip pull-apart basin, and the volcanic deposits began to appear; During the Late Cretaceous period, the basin, dominated by the alluvial deposits, was located in southwest Henan, mainly controlled by faults, and had the characteristics of fault and strike-slip.This study reflects the characteristics of space-time evolution of sedimentary systems in the study area, and provide a more reliable theoretical basis for the exploration of oil and gas, coal and other mineral resources.