Numerous locations in Eastern Arabia contain organic-rich Cenomanian-Turonian(C/T)sediments,including Qatar,UAE,and Oman.The contrast between organicrich and organic-lean anoxic facies,as well as the local to regional...Numerous locations in Eastern Arabia contain organic-rich Cenomanian-Turonian(C/T)sediments,including Qatar,UAE,and Oman.The contrast between organicrich and organic-lean anoxic facies,as well as the local to regional distribution of the C/T facies,is shown here.These regions are confi rmed to be rich in organic material using bore-hole data,and our study has precisely identifi ed their limits.The inorganic geochemical investigations focus on the Cenomanian-Turonian Mishrif Member of the upper Wasia Formation.This elemental chemostratigraphy approach is investigated as a timely and cost-eff ective substitution for carbon isotope determination during hydrocarbon exploration and development phases.The study reveals information about how the palaeoceanography of intrashelf basin changed throughout the Cenomanian-Turonian time.The use of discrete redox-sensitive and primary productivity along with sensitive trace element data and detrital-related elements is demonstrated as one of the best methods to emphasise the reducing conditions that reigned during the OAE-2 in the area.The redox-sensitive proxies show three broad pulses of anoxic to euxinic conditions associated with the bottom water,separated by dysoxic to oxic conditions in the Cenomanian-Turonian Mishrif Member.Either the basin geometry or the expansion of an oxygen minimum zone(OMZ)is the main factor that controlled the bottom redox condition distribution during the deposition of the Mishrif Member.Elemental chemostratigraphy has been utilised to identify and characterise the OAE-2 phases in the study area in the absence of carbon isotope perturbation data.展开更多
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 biostrat...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.展开更多
文摘Numerous locations in Eastern Arabia contain organic-rich Cenomanian-Turonian(C/T)sediments,including Qatar,UAE,and Oman.The contrast between organicrich and organic-lean anoxic facies,as well as the local to regional distribution of the C/T facies,is shown here.These regions are confi rmed to be rich in organic material using bore-hole data,and our study has precisely identifi ed their limits.The inorganic geochemical investigations focus on the Cenomanian-Turonian Mishrif Member of the upper Wasia Formation.This elemental chemostratigraphy approach is investigated as a timely and cost-eff ective substitution for carbon isotope determination during hydrocarbon exploration and development phases.The study reveals information about how the palaeoceanography of intrashelf basin changed throughout the Cenomanian-Turonian time.The use of discrete redox-sensitive and primary productivity along with sensitive trace element data and detrital-related elements is demonstrated as one of the best methods to emphasise the reducing conditions that reigned during the OAE-2 in the area.The redox-sensitive proxies show three broad pulses of anoxic to euxinic conditions associated with the bottom water,separated by dysoxic to oxic conditions in the Cenomanian-Turonian Mishrif Member.Either the basin geometry or the expansion of an oxygen minimum zone(OMZ)is the main factor that controlled the bottom redox condition distribution during the deposition of the Mishrif Member.Elemental chemostratigraphy has been utilised to identify and characterise the OAE-2 phases in the study area in the absence of carbon isotope perturbation data.
文摘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.
