FACIES BELTS AND DEPOSITIONAL 1VIODEL OF LATEPERMIAN HESIHAN FORIWIATION IN HESHAN，CENTRALGUANGXI, SOUTIHERN CFIINA

The Late Permian Heshan Formation in central Guangxi is well known for its coal-bear-ing carbonate sequences. It mainly consists of limestones and contains 6 coal seams. Detailedstudies in Heshan coalfield reveal that Ieshan Formation:was formed in the shallow watercarbonate platform environments under the warm and humid climate. The following faciesbelts and microfacies have been recognized in this sequence: Shallow sea basin fades: (1) Lime mudstone and wackestone and wackestone with the whole body stenohaline organisms; (2) Bioturbated bioclastic wackstone; (3) Bioclastic packstones (tempestites). Platform marginal organic reef facies: Sponge bafflestene and bindstone.Open platform fades:(1)Algal debris packstone with fecal pellets;(2)Forarr:-bioclastic packstone; (3) Fusulinid-organism packstone; (4) Mottling bioturbat-ed recrystallized limestone and dolomitic limestone. Tidal flat facies:(1)1.,am.nated algal debris packstone;(2).Rip- up'intraciasticrudstone;(3) Chera with siliceous gummy sheaths of blue-green algae and the siliciliedbiociasts. Peat flat fades: This fades is represented by the coal seams and the carbonaceousmudstone. Coastal lagoon facies: It is the products of the initial transgression and represented by the alumina claystone. The above facies belts and !nicrofacies are comparable to Wilson .s(1957) carbonateplatform model. 3ut the marginal area of the platform was a ramp which is characterized bythe reef recording middle to stronger wave activity and the gentle slope. Therefore, thedepositionai model of Heshan Formation can be outlined as the carbonate plafforrn with theramp margin. The coal-forming environment is believed to be the peat flat developed on the tidal flat.The Goal-forming materials were the mangrove-like plats which could grow in the brackishand sea water in the tide-influenced swamps which were similar to modern'intertidal m;tn-grove swamps in the southern Florida shelf in the United States and the Hain