Carbonatites, such as bioclastic packstone, sponge spicules wackstone and radiolarian mudstone, dominate in carboniferous sediments of Sanglang, They form rhythmic deposits, in which there are intercalated beds of tuffite(?)，silicalite and dolomitite. In the normal deep－water sediments there exist radiolaria，siliceous sponge spicules and plankton foraminitera, but there is no Shelly fauna. The fragments of shallow－water fossils can only be seen in turbidite. The remains with aragonite shells are absent in all rocks, On the basis of the data on modern abysmal and bathyal sea, it is inferred that the depth of Sanglang carboniferous deposit should be over the carbonate compensation on depth，near or below aragonite compensation on depth, and below -500—-600 meters, where the deposit environment is an anaerobic zone.
