关键词: 大地构造, 控制, 同位素, 演化, 生物礁, 志留纪, 四川盆地

Abstract: According to the tectonic unit characteristics of Upper Yangtze plate and the ⁸⁷Sr/⁸⁶Sr, δC¹³ & δ¹⁸O analyses from the Silurian of North & South margins of Sichuan Basin,the following conclusions can be drawn:(1) During the Early Silurian,the North & South margins of the Sichuan Basin were located at the siliciclastic-carbonate ramp environments which were controlled by the in-plate old land. Near the old land,reefs developed because of the shallow water,and far away from the old land,reefs undeveloped because of the deep water;(2)At the south margin of the Basin,the ⁸⁷Sr/⁸⁶Sr value decreased from Longmaxi formation to Shiniulan formation indicating that the sea-level increased gradually.At the bottom of Hanjiadian formation along with the ⁸⁷Sr/⁸⁶Sr value increased,the regressive event occurred;(3)At the south margin of the Basin,δ¹³C value in Shiniulan formation increased from bottom to top,and the average value is 1.2‰ (PDB). At the Basin north margin,the δ¹³C value increased obviously from Wangjiawan formation to Ningqian formation. The δ¹³C evolution indicated that the transgressive event occurred from Llandovery to Early Wenlock,and after that the regressive event took place. The systmatic changes of δ¹⁸O value induces the similar onclusions, although the δ¹⁸O affected by diagenesis;(4) The local sea-level change can be compared with the global transgressive-regressive events in the Early Silurian and all the reefs developed at the transgressive period and high sea-level period.During the high sea-level period,the environment was best for reef development.The topographic characteristies and sea-level changes has strong influence on the reefs development.

Key words: tectonic, control, isotope, evolution, reef, Silurian, Sichuan Basin