Up to 1000 m thick reefs according to ref. 662.
Abstract ref. 1648:
The section between 0 and 400 m of well Xichen-1 was completely cored, which has provided rich data for various laboratory analyses on its reef succession. A complete and systematic review has been made on its diagenetic environment, processes and characteristics by means of thin section observations, electron probe analysis, C and O stable isotopic determinations of gastropod tests of individual genera at different well depths and different sediments at the same depth and the analysis of Mg/Ca and Mg/Sr. Non-algal boring of the micrite suite and the non-mixed water genesis of dolomitic have been proposed. 