The Pre-Sturtian negative δ13C excursion of the Dajiangbian formation deposited on the western margin of Cathaysia Block in South China
The Pre-Sturtian negative δ13C excursion of the Dajiangbian formation deposited on the western margin of Cathaysia Block in South China
复制标题
DOI：
10.1007/s12583-016-0665-9
复制
发表时间：
2016-04
影响因子：
3.3
通讯作者：
Lianjun Feng;Qirui Zhang
中科院分区：
文献类型：
--
作者：
Lianjun Feng;Qirui Zhang
中国南段大江边组为华夏地块西缘低级变质硅质碎屑岩为主的沉积序列，盖层为冰生二长花岗岩(四舟山组)。四舟山冰川成因地层与中国南部的江口冰川地层在地层和岩性上具有相似性，可归属于江口冰期(斯特尔斯蒂安冰期)事件。对大江边组上部的碳酸盐、硅质岩和页岩单元进行了碳酸盐碳同位素(δ13Ccarb)和有机碳同位素(δ13Corg)分析。氧同位素(δ~(18)O)和锰/锶(Fe/Sr)比值等一系列地球化学指标表明，大江边组上部保存了原始碳同位素。大江边组上部为δ~(13)C~(-0.1)‰，向上向下递减至-5.4‰。我们认为，四舟山英云闪长岩下的δ~(13)C负漂移与前斯图尔特岛的δ~(13)C碳同位素组成有关，并与全球新元古代同位素地层学相对比。我们发现大江边组上部碳酸盐和有机碳同位素数据是耦合的，与在多个大陆上观察到的δ13Ccarb-δ13Corg模式一致。
The Dajiangbian Formation in South China is a siliciclastic-dominated sedimentary succession with low-grade metamorphism deposited on the western margin of the Cathaysia Block, and is capped by a glaciogenic diamictite (the Sizhoushan Formation). The Sizhoushan glaciogenic strata can be attributed to the Jiangkou glacial (Sturtian glacial) episode as they share stratigraphic and lithological similarities with Jiangkou strata in South China. Some carbonate, chert and shale units throughout the upper part of the Dajiangbian Formation were sampled for carbonate carbon isotope (δ13Ccarb) and organic carbon isotope (δ13Corg) analyses. A range of geochemical indices including oxygen isotopes (δ18O) and Mn/Sr (Fe/Sr) ratios suggest that primary carbon isotope values were preserved in the upper Dajiangbian Formation. The upper Dajiangbian Formation shows δ13Ccarbof -0.1‰, upward decreasing towards to -5.4‰. We suggest that the negative δ13C excursion beneath the Sizhoushan diamictite is correlative with the Pre-Sturtian Islay δ13Ccarbanomaly and allows correlation with the global Neoproterozoic isotope stratigraphy. We find that carbonate and organic carbon isotope data of the upper Dajiangbian Formation are coupled, consistent with the δ13Ccarb-δ13Corgpattern observed on multiple continents.