摘要
陆表海碳酸盐岩型含煤岩系是我国含煤岩系的一个重要类型,以广西晚二叠世合山组为代表。文中对该煤系中的碳酸盐岩进行了详细的微相分析,认为合山组沉积时期合山地区为温暖潮湿气候下的浅水环境,提出了包括浅海盆地、生物礁、开阔台地、潮坪和泥炭坪在内的陆表海碳酸盐台地沉积模式,并指出合山组碳酸盐台地边缘是以生物礁为代表的缓坡,最后对合山组的旋回层序进行分析,认为合山组沉积过程中,地壳沉降作用和海平面变化起了主导作用。
The Late Permian Heshan Formation in central Guangxi is well known for its coal-bearing carbonate sequences. It mainly consists of limestones and contains 6 coal seams. Detailed studies in Heshan coalfield reveal that Heshan Formation ,was formed in the shallow water carbonate platform environments under the warm and humid climate. The following facies belts and microfacies have been recognized in this sequence:
Shallow sea basin facies: (1) Lime mudstone 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 facies: (1) Algal debris packstone with fecal pellets; ( 2) Foram-bioclastic packstone; (3) Fusulinid-organism packstone; (4) Mottling bioturbat-ed recrystallized limestone and dolomitic limestone.
Tidal flat facies: (1) Laminated algal debris packstone; (2) 'Rip-up' intraciastic rudstone; (3) Chert with siliceous gummy sheaths of blue-green algae and the silicified bioclasts.
Peat flat facies: This facies is represented by the coal seams and the carbonaceous mudstone.
Coastal lagoon facies: It is the products of the initial transgression and represented by the alumina ciaystone.
The above facies belts and microfacies are comparable to Wilson' s (1957) carbonate platform model. But the marginal area of the platform was a ramp which is characterized by the reef recording middle to stronger wave activity and the gentle slope. Therefore, the depositional model of Heshan Formation can be outlined as the carbonate platform with the ramp margin.
The coal-forming environment is believed to be the peat flat developed on the tidal flat. The coal-forming materials were the mangrove-like plats which could grow in the brackish and sea water in the tide-influenced swamps which were similar to modern intertidal mangrove swamps in the southern Florida shelf in the United States and the Hainan Island in China. These ideas are evidenced by the higher organic sulphur contents in the coal, marine fossils in the claystone and chert partings of the coal seams, and the tidalflat laminated algal debris limestone and cherts underlying and overlying the coal seams. Vertical distributions of the facies and microfacies suggested the possibilities of the cycle analysis for their depth significance. It is considered that the regional subsidence and the periodic sea level changes played important roles in the forming of the Heshan coal-bearing se-quence.
出处
《沉积学报》
CAS
CSCD
北大核心
1990年第4期13-21,共9页
Acta Sedimentologica Sinica
