摘要
Field observation and microscopic study on thin sections reveal that special sedimentary structures,such as miarolitic structure,tepee-like structure,layer jointed structure and convolute structure,barites and pyrite are widely developed and δ(13C)values were generally significant negative(the average value was-4.73×10-3 and-4.52×10-3 in each study section).The"methane seep"hypothesis can be used to give a good explanation to part of geological characteristics and geochemical characteristics of the cap carbonates so the conclusion is reached that the cap carbonates is formed by"methane seep".