Geochemical Record of the Cenomanian-Turonian Anoxic Event in Tunisia:Is it Correlative and Isochronous to the Biotic Signal?

作     者：Mohamed SOUA Dalila ZAGHBIB-TURKI Hela BEN JEMIA Jalel SMAOUI Amel BOUKADI 

作者机构：Exploration and Studies Department Entreprise Tunisienne d'Activités Pétrolières(ETAP)Charguia Ⅱ2035 Tunisia Département of Geology Faculty of sciences of TunisUniversity of Tunis El Manar1068 Tunisia Petroleum Research and Development Center(CRDP-ETAP) Charguia Ⅱ2035 Tunisia 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2011年第85卷第6期

页      面：1310-1335页

核心收录：

学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学] 

基　　金：Professor Missoum Herkat (Université Boumedien Algeria) and anonymous reviewer for providing constructive comments and Nigel Collins (Terrasciences Ltd.) for improving the English 

主　　题：Bahloul Formation Foraminifera chemostratigraphy OAE-2 

摘      要：In Tunisia, five Bahloul spaced sections, Bargou, Jerisa, Guern Halfaya, Kherij and Gafsa were analyzed for biostratigraphy （foraminifera and radiolarians） and major and trace elements. This high-resolution biostratigraphic and chemostratigraphic integrated analyses for the Late Cenomanian-Early Turonian Bahloul Formation provide new insight into the palaeoceanographic evolution of the southern Tethyan margin. Relative low abundance of related terrigenous Ti/Ai and K/ Al ratios and enrichment of some productivity proxies such as Ba, Cu, and Ni （organic matter related trace elements） suggests that the Bahloul, deposited during a relatively short period （0.5 Ma）, was of relatively elevated primary productivity and minimal detrital input. While higher D＊ values concurrent with lower Ti/AI ratios are interpreted as caused by enhanced fluvial material contribution, due to more humid climate during the OAE-2. Enhanced humidity triggered probably fluvial influxes, resulted in a sluggish water circulation and consequent anoxic/euxinic conditions favoring the preservation of organic matter at the bottom. Enrichments in redox-sensitive trace metals U, V, and Mo in the Bahloul Formation deposits and redox indices, such as V/（V＋Ni）, U/Th, V/Cr, and Ni/Co, indicate that oxygen-restricted conditions prevailed during the Late Cenomanian to earliest Turonian times and correlate well with relative abundances of some foraminiferal and radiolarian paleo- environmental relevant indicators. High Ba~ values and Uauth may indicate anoxic conditions at least at the water-sediment interface during the Bahloul Formation deposition and provide information about low to moderate sulfate-reduction reactions.