Using Sr isotopes and Rare Earth Elements to correlate sequences in regions with complex facies distributions: Example from the Late Cretaceous of the South-Central Pyrenees

16th Bathurst Meeting Abstracts Volume Posters Theme 2: Diagenesis and Geochemical Markers Carbonate Precipitation/Dissolution, Diagenetic Processes and Products Dolomitization Soils and Karst Geochemical Markers and Dating P-59 to P-130 Using&Sr&isotopes&and&Rare&Earth&Elements&to&correlate&sequences&in®ions& with&complex&facies&distributions:&Example&from&the&Late&Cretaceous&of&the& South-Central&Pyrenees& & Enric&Pascual-Cebrian1;&Mar&Moragas1;&Arnaud&Gallois1;&Jorge&Belenguer-Oliver1;&Ylenia&Almar1;&Ander&MartínezDoñate1;&Peter&Drzewiecki2;&Wayne&R.&Wright3;&David&W.&Hunt3;&Jaume&Vergés1& 1Group&of&Dynamic&of&the&Lithosphere&(GDL),&Institute&of&Earth&Sciences&Jaume&Almera,&ICTJA-CSIC,&Lluís&Solé&i& Sabarís&s/n,&08028&Barcelona&Spain&Barcelona& 2Department&of&Environmental&Earth&Science,&Eastern&Connecticut&State&University& 3Equinor&ASA,&Exploration&Research,&Fornebu,&Norway& [email protected]sic.es& Key&words:&Strontium&Isotopes;&Rare&Earth&Elements;&Late&Cretaceous;&Pyrenees& Understanding&the&distribution&of&carbonate&facies&in&areas&with&complex&structural&histories& can&be&challenging.&The&Upper&Cretaceous&deposits&of&the&Sant&Corneli&and&Boixols&anticlines& in&the&Pyrenees&are&controlled&by&extensional&inherited&structures&and&subsequent&inversion.& The&aim&of&the&present&study&is&to&understand&the&timing&of&the&structures&and&correlate&the& facies&across&the&anticlines.&The&dating&of&the&Coniacian-Santonian&postrift&and&CampanianMaastrichtian& syn-growth& sequences& is& based& on& numerical& ages& derived& from& 87Sr/86Sr& ratios.& Additionally,& elemental& analysis& and& rare& earth& elements& have& been& used& to& characterise&seawater&signatures,&environments&and&diagenetic&overprints.& A& total& amount& of& 162& samples& were& collected& across& the& two& anticlines.& Geochemical& analysis& by& using& ICP-MS& permitted& an& evaluation& of& the& elemental& concentrations& of& the& samples&in&order&to&discriminate&the&suitable&ones&for&strontium&isotopes.&Numerical&ages& derived& from& strontium& isotopes& show& that& the& Santonian& carbonate& systems& were& coetaneous&across&the&Sant&Corneli&anticline.&Rudist-rich&facies&in&the&northern&flank&of&the& Sant& Corneli& anticline& correlate& with& the& carbonate& platforms& in& the& southern& flank.& The& uppermost&Santonian&shallow&marine&carbonates&sampled&in&the&southern&flank&in&Collades& de& Basturs& might& correlate& with& the& silty& clays& and& marls& of& l’Aubagueta& Member& in& the& northern&flank.& The& obtained& numerical& ages& derived& from& strontium& isotopes& together& with& magnetostratigraphic,&and&biostratigraphic&data&have&been&used&to&constrain&the&timing&of& growth& of& the& anticlines.& The&syn-growth& succession& shows& ages& ranging& from& middle& Campanian& in& the& uppermost& Herbasavina& Formation& to& early& Maastrichtian& in& the& Castell& d’Orcau&Unit.&Those&results&point&to&older&ages&than&previously&published&works.&& The&analysis&of&rare&earth&elements&and&Yttrium&(REEY)&has&shown&flat&shaped&REEY&profiles& that& are& typical& for& the& Late& Cretaceous;& and& may& indicate& low& diagenetic& alteration.& Preliminary&results&based&on&the&Y/Ho&ratio&has&revealed&changes&on&paleobathymetries&and& environments.&Therefore,&the&use&of&rare&earth&elements&could&be&used&as&a&proxy&to&support& sedimentological&observations.& Bathurst Meeting Mallorca 2019 16th International Meeting of Carbonate Sedimentologists Theme 2: Diagenesis and Geochemical Markers P-117