Carbon-isotope record and paleoceanographic changes prior to the OAE 1a in the Eastern Tethys: Implication for the accumulation of organic-rich sediments. (March 2020)

• Record Type: Journal Article
• Authors: Fu, Xiugen; Wang, Jian; Wen, Huaguo; Wang, Zhongwei; Zeng, Shengqiang; Song, Chunyan; Wang, Dong; Nie, Ying
• Is Part Of: Marine and petroleum geology. Volume 113(2020)
• Publication Date: 2020-03
• Subjects: Late Barremian -- Paleoclimate -- Sedimentation rate -- Primary productivity -- Redox condition; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2019.104049
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: The Barremian and Aptian correspond to periods of marked changes in the atmosphere-ocean system, and offer valuable information about global tectonic events. Here, we present integrated high-resolution carbonate carbon-isotope (δ 13 Ccarb ) and geochemical data that precede the Early Aptian oceanic anoxic event (OAE 1 a) in the Qiangtang Basin (Eastern Tethys). We identified a characteristic and well-correlatable Barremian-Lower Aptian carbon-isotope pattern that can be categorized into 10 Segments. The most notable features of the δ 13 Ccarb record are multiple negative carbon-isotope excursions in the Barremian-Aptian, and each is possibly linked to environmental changes. Two carbon isotopic plateaus are observed in the Upper Barremian, which are generally related to increased primary productivity, and to the concomitant development of dys-to anaerobic conditions. Our data indicate the development of anoxic conditions during shale deposition, which occurred under the conditions of a semi-enclosed lagoon environment. Such conditions, were likely localized, and not the primary mechanism responsible for the deposition of organic-rich sediments within the Shenglihe succession. The deposition of organic-rich shales was very likely due to global/regional warming. Rising temperatures and hydrological cycle strengthening during shale deposition are believed to have increased primary productivity, and thus resulted in the expansion of the local oxygen minimum zone within the water column. Highlights: Barremian was a time of marked changes in the atmosphere-ocean system. δ 13 C record is subdivided into 10 δ 13 C segments prior to the OAE 1a. Positive carbon isotope excursion is prominent in the Upper Barremian. Global warming would raise surface productivity.