华南中泥盆世棋梓桥组碳酸盐岩潮汐沉积及其微相类型

TIDAL DEPOSITS OF CARBONATE FACIES AND THEIR MICROFACIES TYPES IN THE QIZIQIAO FORMATION OF MIDDLE DEVONIAN, SOUTH CHINA

Tidal-flat and shoal deposits of carbonate facies in the Qiziqiao Formation are widely distributed over the vastareas of Guangxi,Guangdong and Hunan provinces,constituting an important stratigraphie unit where stratabound and sttatigorm ore deposits (galenite-sphalerite-pyrite) are. found,Thede types of ore deposits seem to have close relations to the tidal deposits. R ecognition of tho tidal sediments is based upon rock fabric, texture, strueture, fossil assemblage, and particular sedimentary cycles. The typical sequence of tidal-flat deposits consists mainly of three units: Amphipora limestone, laminated limestone and dalostone (from the bottom to the top).This sequence represents a complete process of sedimentation from low-tidal-flat through intertidal to high-tidal-flat or supratidah The sequence of shoal deposits of carbonate facies consists chiefly of grainstone and algal ooelsparite. Two major types of tidal deposits (open and restricted marine facies) can be distinguished, with eleven microfacies as follows: 1) grainatone with sparite (MF-1)[2) algal ooelsparite (MF-2); 3) onclite (algae-, or stromatoporoid-coated particles)(MF-3) ; 4) bioclastic grainstone or rudstone with sparite (MF-4); 5) Amphipora limestone (MF-5) ; 6) clark fossil-poor mierite (MF-6) ; 7) pelsparite or peloldal grainstone with sparite(MF-7);8)laminated pelleted mudstone-wackstone(MF-8);9)micrite with onkoids(MF-9);10)rudstone or floatstone(MF-10);and 11)bedding dolomite,gypsum-dolomite(MF-11).

Tidal-flat and shoal deposits of carbonate facies in the Qiziqiao Formation are widely distributed over the vast areas of Guangxi, Guangdong and Hunan provinces, constituting an important stratigraphic unit where stratabound and stratiform ore deposits (galenite-sphalerite-pyrite) are found. These types of ore deposits seem to have close relations to the tidal deposits. Kecognition of the tidal sediments is based upon rock fabric, texture, structure, fossil assemblage, and particular sedimentary cycles. The typical sequence of tidal-flat deposits consists mainly of three units: Am-phipora limestone, laminated limestone and dolostone (from the bottom to the top). This sequence represents a complete process of sedimentation from low-tidal-flat through intertidal to high-tidal-flat or supratidal. The sequence of shoal deposits of carbonate facies consists chiefly of grainstone and algal oolsparite.Two major types of tidal deposits (op en and restricted marine facies) can be distinguished, with eleven microfacies as follows: 1) grainstone with sparite (MF-1); 2) algal oolsparite (MF-2); 3) onclite (algae, or stromatoporoid-coated particles) (MF-3); 4) bioclastic grainstone or rudstone with sparite (MF-4) ; 5) Amphipora limestome (MF-5); 6) dark fossil-poor micrite (MF-6); 7) pelsparite or peloidal grainstone with sparite (MF-7); 8) laminated pelleted mudstone-wackstone (MF-8); 9) micrite with onkoids (MF-9); 10) rudstone or floatstone (MF-10); and 11) bedding dolomite, gypsum-dolomite (MF-11).