Marine incursion events in the Late Cretaceous Songliao Basin: Constraints from sulfur geochemistry records

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• 作者：Yongjian Huang ; Gansheng Yang ; Jian Gu ; Pingkang Wang ; Qinghua Huang ; Zihui Feng ; Lianjun Feng
• 关键词：Marine incursion events ; Songliao Basin ; Cretaceous ; Sulfur geochemistry
• 刊名：Palaeogeography, Palaeoclimatology, Palaeoecology
• 出版年：2013
• 出版时间：1 September, 2013
• 年：2013
• 卷：385
• 期：Complete
• 页码：152-161
• 全文大小：892 K

文摘

Songliao Basin in NE China developed the most productive oilfield in the world sourced from terrestrial rocks. The main source rock of the basin includes member 1 of the Qingshankou (K₂qn¹) and members 1 and 2 of the Nenjiang Formation (K₂nj^1-2). However the exact reasons for the formation of the source rock, especially the K₂qn¹ are still controversial. Former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of K₂qn¹ but further geochemical evidence is needed. This paper explores the distinct sulfate levels that distinguish marine from fresh waters of the Songliao paleo-lake. We undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the Quantou Formation (K₁q⁴) to top of member 1 of the Qingshankou (K₂qn¹). The ratio of organic carbon to the pyrite sulfur (TOC/PYS) proved the previously suggested saline conditions during the deposition of K₂qn¹; and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for K₂qn¹, but also for top of K₁q⁴. The exact time for the beginning of marine incursion is to be determined. The marine incursion within K₂qn¹ is not strong and partially controlled by the fluctuation of paleo-lake level. The present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the Songliao paleo-lake, although further studies are still needed.