SEDIMENTARY CHARACTERISTICS AND PALAEOGEOGRAPHIC SIGNIFICANCE OF THE LOOSE SEDIMENTS AT THE LOWERMOST PART OF THE CENOZOIC STRATA IN THE SOUTHERN HUAIBEI COALFIELD

There are large discrepancies in sedimentary textures and structures and mineral com-positions of the sediments from the Xuxian and Linhuan mining districts although in the same coalfield,as revealed by sedimentary characteristics of the loose sediments at the low-ermost part of the Cenozoic strata in southern Huaibei coalfield.The authors owe these dif-ferences to different provenances,lithology and palaeogeographic environments in respec-tive mining districts.For instance,the sediments in the Linhuan mining district consist mainly of quartz,feldspar and carbonate minerals plus the heavy mineral assemblages dom-inated by zircon and tourmaline vindicating that the detritus were derived from the weather-ing products of the neutral diorite massifs in the north of the mining district,while in the Xixian mining district,the sediments are characteristic of a large amount of limestone grav-els plus subordinate quartz and chert,suggesting that the principal sources of detritus lay to the Ordovician strata and intensely weathered coal measures in the east and north of the mining district. The complex textures and structures and mineral compositions of the sediments show higher bedrock topography in the north of the mining districts,intense physical weathering of the source rocks,short-distance and faster transport,and polyphyletic origins.