Abstract
The Dananhu coalfield, at the southern margin of Turpan-Hami Basin, Xinjiang, has good coal-forming geological conditions. Due to the low research level on the depositional environment and coal accumulation, the comprehensive coal mining is restricted. Based on drilling and sectioning outcrop data, the depositional characteristics, lithofacies, paleogeography, and coal accumulation of the coal-bearing formations in western Dananhu coalfield are analyzed. The middle member of the Xishanyao Formation is the major coal-bearing strata of the Dananhu coalfield, composed of conglomerate, sandstone, siltstone, mudstone, and combustible organic rock, which can be further subdivided into 14 lithofacies according to substance composition, sediment texture, and structure. During the early Middle Jurassic coal-accumulating period, alluvial fan, fluvial plain, fluvial delta, and shallow lacustrine deposits were developed from northeast to southwest in the western Dananhu mining area. Coal accumulation was most developed in the center regions of the study area extending from northeast to southwest, which were primarily concentrated in margin fans, floodplains, interdeltaic bays, and lakeshore environments, especially the transitional zone between the fluvial plain and the delta plain in the west of No. 1 mining area. This coal accumulation was mainly controlled by synsedimentary tectonic subsidence and clastic sediments supply or sedimentary environment, where tectonic subsidence was the primary controlling factor and the source supply was the secondary controlling factor for coal accumulation, which provided theoretical support for the coal prediction and geological exploration in western Dananhu coalfield.
Highlights
With the discovery of thick coa1 seams formed in Jurassic continental basins in northwestern China, special attention has been paid to the application of sequence stratigraphy and sedimentary characteristics and coal accumulation to continental coal measures [1,2,3,4,5,6,7,8]
Based on drilling and sectioning outcrop data in western Dananhu coalfield, 5 rock types: conglomerates, sandstones, siltstones, mudstones, and coals, were recognized in the middle member of Xishanyao Formation, which can be further divided into 14 lithofacies types
During the Xishanyao Formation period, depositional facies including alluvial fans, fluvial plains, deltas, and lacustrine facies were developed in the research area from northeast to southwest
Summary
With the discovery of thick coa seams formed in Jurassic continental basins in northwestern China, special attention has been paid to the application of sequence stratigraphy and sedimentary characteristics and coal accumulation to continental coal measures [1,2,3,4,5,6,7,8]. In this paper, based on the drillings and logging data from the No 1, 2, and 3 mining areas in the west of the Dananhu coalfield (Figure 1(c)), the sedimentological characteristics of the terrestrial coal measures from the middle member of the Xishanyao Formation are presented and sedimentary environment and the paleogeography during the coal accumulation period are reestablished. From these data, a coal accumulation model as well as the factors controlling the coal seams development is proposed. It is anticipated that this work will facilitate coal prediction and geological exploration, but it will provide theoretical support for the development and utilization of coal resources
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