SKELETAL GIRVANELLA OOLITES AND ITS PETROLOGICAL SIGNIFICANCE IN LOWER CAMBREAN OF XIUSHAN, SICHUAN PROVINCE
四川秀山下寒武统清虚洞组的骨骼葛万藻藻鲕及岩石学意义

Stromatolites ore dividcd into skeletal stromatolites and nonskeletal stromatolites. On the basis of the relationship between girvanella and stromatolites, the skeletal stromatolites is divided into skeletal girvanella stromatolites, skeletal girvanella on colites, skeletal girvaaella oolites and sreletal girvanella thrombolites. Skeletal girvanella oolites is discussed in this paper. The skeletal girvanella oolites is constructed by girvanella and its products recrystallized, the oolites is consist of three part: (1) girvanella and material that captured by itself and cohered on it, (2) structure remains of girvanella recrystallized, and (3) calcite crystals recrystallized. The difference of skeletal girvanella from the general oolites is in the prese vation of girvanella fossils and structure recrystallized remains in the oolites, and in formation of concentric and radial-concentric laminaes in the oolites. The skeletal girvanella oolites deposited on the subtidal and interstitial zones and provided the evidance for organic origin of oolites.