摘要
Limestone-marl alternations, including the entire spectrum from nodular alternations to well- bedded sequences, widely distributed from shallow shelf to pelagic realm, are usually interpreted to reflect palaeoenvironmental signals in a high resolution. Some scholars believe that the diagenetic process only enhances the differences of primary signals, while others propose that pure diagenesis can not only alter the original records but also produce the same phenomenon as primary deposits. This paper reviews the environment and the process of differential diagenesis, and discusses the related question, including the source of the cements and the role of organic matter during early diagenesis. At last, the Qixia Formation is selected as an example to explain the origin of those alternations.