地质学报（英文版）2007，Vol.81Issue(3)：463-469,7.
Burial Records of Reactive Iron in Cretaceous Black Shales and Oceanic Red Beds from Southern Tibet
Burial Records of Reactive Iron in Cretaceous Black Shales and Oceanic Red Beds from Southern Tibet
摘要
Abstract
One of the new directions in the field of Cretaceous research is to elucidate the mechanism of the sedimentary transition from the Cretaceous black shales to oceanic red beds. A chemical sequential extraction method was applied to these two types of rocks from southern Tibet to investigate the burial records of reactive iron. Results indicate that carbonate-associated iron and pyrite are relatively enriched in the black shales, but depleted or absent in red beds. The main feature of the reactive iron in the red beds is relative enrichment of iron oxides (largely hematite), which occurred during syn-depostion or early diagenesis. The ratio between iron oxides and the total iron indicates an oxygen-enriched environment for red bed deposition. A comparison between the reactive iron burial records and proxies of paleo-productivity suggests that paleo-productivity decreases when the ratio between iron oxides and the total iron increases in the red beds. This phenomenon could imply that the relationship between marine redox and productivity might be one of the reasons for the sedimentary transition from Cretaceous black shale to oceanic red bed deposition.关键词
reactive iron/black shales/oceanic red beds/Cretaceous/southern TibetKey words
reactive iron/black shales/oceanic red beds/Cretaceous/southern Tibet分类
天文与地球科学引用本文复制引用
HUANG Yongjian,WANG Chengshan,HU Xiumian,CHEN Xi..Burial Records of Reactive Iron in Cretaceous Black Shales and Oceanic Red Beds from Southern Tibet[J].地质学报（英文版）,2007,81(3):463-469,7.基金项目
This work is supported by the National Key Basic Research Program (2006CB701406), Natural Science Foundation of China for Youth (40403003) and Key Project of the Natural Science Foundation of China (40332020), and is a contribution to IGCP 463. （2006CB701406）
