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

叠层石有正常叠层石和骨骼叠层石之分。与葛万藻有关的骨骼叠层石分为骨骼葛万藻叠层石、骨骼葛万藻核形石、骨骼葛万藻藻鲕和骨骼葛万藻凝块石等四类。骨骼葛万藻藻鲕是由葛万藻藻球经过重结晶作用而变成的。镜下观察,这种鲕由葛万藻及其捕获粘结的碎屑颗粒、葛万藻重结晶残余结构和重结晶方解石晶体三部分构成。骨骼葛万藻藻球是潮间和潮下低能环境中形成的,它为鲕的生物成因提供了有力的证据。

SKELETAL GIRVANELLA OOLITES AND ITS PETROLOGICAL SIGNIFICANCE IN LOWER CAMBREAN OF XIUSHAN, SICHUAN PROVINCE

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.