浙江桐庐二叠纪海绵生物丘的沉积环境和成岩环境

浙江桐庐二叠纪茅口期海绵丘发育于碎屑陆棚上，呈透镜状，无礁前和礁后相。由于当时相对频繁的海进海退，使该丘在生长过程中出现三次成礁期，海进成礁，海退消亡。其主要的礁岩类型为海绵（或水螅）障积岩，在上部出现纹层藻和古石孔藻粘结岩，最后为潮坪相叠层石灰泥岩所覆盖。该丘经历了早期海底、海水潜流带、混合水和大气淡水成岩环境。早期成岩作用以灰泥淀积作用为主，大部分孔隙都为灰泥所充填，少量残余孔隙中可见形成于早期海底成岩环境的纤状和针状方解石胶结物。

The sedimentary and diagenesis environments of Permian sponge mound in Tonglu, Zhejiang

The Tonglu sponge mound, outcropping in the Lengwu village, was developed on a elastic shelf, and formed in the lenticular limestone of the upper Maokou Formation without deposits of fore and back reef factes. With the relatively frequent transgression and regression, there occured three reef-building periods, with the reefs formed in the transgression but consumed in the regression. The reef rocks thus formed are mainly sponge (or hydrozoa) bafflestone, grading upwards into laminated algae and Archaeolithoporella bindstone, and eventually covered by stromatolitic lime mudstone of tidal flat factes. This sponge mound has experienced the early submarine, marine phreatic water, mixed water and meteoric freshwater environments. The diagenesis of the early stage was most developed in the micrtic calcite comentation, with most primary pores aggraded by lime mud. In some pores appeared fibrous and acicular calcite formed in the early submarine environment.