Postglacial trace-fossil assemblages of western Gondwana and their implications: An example from Pennsylvanian deposits of the Paganzo and Calingasta-Uspallata basins of western Argentina.

PABLO JOAQUIN ALONSO MURUAGA; LUIS A. BUATOIS; CARLOS O. LIMARINO

Idanha a Nova

Congreso; 4th International Congress on Ichnology; 2016

INTERNATIONAL ICHNOLOGICAL ASSOCIATION

Postglacial trace-fossil assemblages of western Gondwana and their implications: An example from Pennsylvanian deposits of the Paganzo and Calingasta-Uspallata basins of western Argentina.Pablo Joaquin Alonso-Muruagaa^*, Luis Buatoisb and Carlos Oscar LimarinoaaDepartamento de Cs. Geologicas, FCEN, Universidad de Buenos Aires, Intendente Güiraldes 2160 - Ciudad Universitaria - C1428EGA, IGEBA-CONICET, Argentina. (* corresponding author; pablojoaquin3@yahoo.com.ar ) (^ presenting author)bDepartment of Geological Sciences, University of Saskatchewan, 114 Science Place,Saskatoon, Saskatchewan, Canada.Keywords: Pennsylvanian, postglacial, ichnofauna, ichnofacies, calibration.Pennsylvanian deposits of the Paganzo and Calingasta-Uspallata basinsof western Argentina provide an opportunity to document and comparepostglacialichnofaunas forming under contrasting depositional settings.Progradational deposits above the maximum flooding interval that marks the culmination of the postglacial transgression contain distinctive trace-fossil assemblages whichprovide valuable evidence for reconstructing the environmental conditions that operated after the final glacial retreat. The postglacial facies ofthe PaganzoBasin document deltaic sedimentation in lacustrine to transitional settings (fjords), hosting freshwaterichnofossilassemblages . Thisichnofauna iscomposed of simple forms,especiallyMermiacarickensis,Gordia marina,Treptichnusbifurcus,T.pollardi,Helminthopsis tenuis and Helminthoidichnites tenuis,representing the MermiaIchnofacies.Coeval units in theCalingasta-UspallataBasin record deposition in amarginal marine environment affected by deltaic discharge, containing brackish tracefossil assemblages. This ichnofauna is dominated by typical marine ichnotaxasuch as Psammichnitesplummeri,P.implexus,Protovirgulariaisp.,Ptychoplasmavagans,Lingulichnusverticalis,together with local occurrences of Treptichnusbifurcus, Lockeiaisp.anda few arthropod trackways,characterizingthe depauperateCruzianaIchnofacies.Ichnologic data allow reconstruction of paleosalinity levels within the same postglacial unit,refining the calibration of ichnofacies models in glacial-related settings