The Analysis Of Sedimentary Characteristics And Palaeogeography Of The Paleogene In Guanzhong Basin

Guanzhong Basin, which is located between Ordos platform and Qinling orogenic belt,is an extensional and faulted basin which formed on Yanshanian regional uplift. Basin Guanzhong has been in a special tectonic stress field since the Meso-Cenozoic era, where its geological structure is complicated, faults are developed, and because the basin has been in a kind of imbalanced subsidence for a long time, the stratigraphic sediment is thicker and the difference between north and south of the area is clear, the change of depositional environment and lithologic composition is complexed.On the basis of field geological investigation and geochemical analyses, utilized theories of sedimentology, paleogeography, tectonics and petroleum. The paper deeply and systematically analyses the paleogeography characteristics, sedimentary characteristics and tectonic characteristics of the Paleogene in Guanzhong basin, combined with the achievement of predecessors and the existing seismic data, well log data. The main research results are as follows:The Paleogene system formation is near source, distribution in different position of filling deposit belong to the multi provenance sedimentary system: alluvial fan of Qinling Mountains piedmont in the Guanzhong Basin is mainly filled with coarse clastic sediments.Particle cumulative probability curve are mainly two-phase, the porosity are well developed and the separation of particles are mediocre; sediments of northern uplift are consisted of fluvial facies and alluvial fan, the detrital grain is relatively fine.The characteristics of sedimentary facies, paleogeographic characteristics of Guanzhong basin is changing with the evolution of the basin. Based on thegeophysical signs, combined with signs of petrology and sedimentary structure, controlled by the structural sedimentary setting, the Paleogene of study area are classified into 2 main depositional systems. In the early Paleogene, alluvial fan are well developed in Honghe group because of the strong hydrodynamic turbulent conditions; Until the early Oligocene, fluvial and lacustrine facies are well developed in Bailuyuan group, the lithology is mainly gray-white sandstoneinterbedded with palm red mudstone; the basin began to uplift again in the end of Paleogene,and the stratigraphic unconformity is formed.