Wuerxun Depression Fan Delta Depositional System Research of Nantun Formation in Wubei Sub-depression

摘要

Fan delta facies deposition are developed in the steep slope of faulted lake basin and have features, such as the rapid accumulation, from near provenance, clastic coarse granularity and poor sorting. By means of core, logging, well logging and seismic data, based on the sedimentary characteristics of Nantun formation of Wuerxun depression, the conclusions are as followings: Faulted basin steep slope belts are developed fan delta depositional system with volcano facies in Wubei sub-depression of Wuerxun depression; The fan delta system are divided into plain, front and front fan delta etc, three subfacies, seven microfacies; In distributary channel microfacies, sand conglomerate, gravel sandstone, middle-grit are main lithology, low maturity, poor sorting to medium, vertical sequence, visible bottom gravel and erosion surface, large scale cross-bedding are developed, partial visible horizontal bedding; channel mouth bar microfacies relatively rudimentary, lithology with sorting relatively good powder-middle sandstone, development of small cross-bedding, horizontal bedding.