CENOZOIC MICROBIOTAS FROM THE EASTERN SECTOR OF THE JAMES ROSS ISLAND GROUP, ANTARCTIC PENINSULA

CONCHEYRO, ANDREA; AMENÁBAR, CECILIA R; CARAMÉS, ANDREA; ADAMONIS, SUSANA; LIRIO, JUAN M.; BALLENT, SARA; DI PASQUO, MERCEDES; MACKERN, ALAN

Ciudad Autónoma de Buenos Aires

Conferencia; Scientific Comité on Antarctic Research XXX1 SCAR and Open Science Conference; 2010

CENOZOIC MICROBIOTAS FROM THE EASTERN SECTOR OF THE JAMESROSS ISLAND GROUP, ANTARCTIC PENINSULAConcheyro, A.1,2,3, Caramés, A.2, Amenábar, C.R.1,2,3, Adamonis, S.3, Lirio, J.M.1, Ballent,S.2,4, di Pasquo, M.2 and Mackern, A1.1Instituto Antártico Argentino - Dirección Nacional del Antártico2Consejo Nacional de Investigaciones Científicas y Técnicas3Departamento de Ciencias Geológicas - Universidad de Buenos Aires4División Paleontología de Invertebrados - Museo de Ciencias Naturales de La Plataandrea@gl.fcen.uba.arKeywords: diamictites, microfossils, CenozoicCenozoic fossiliferous deposits are analyzed in several localities of Vega and JamesRoss islands, focusing on their micropaleontological content. Sandwich Bluff diamictite (VegaIsland) is a basal till deposited by a eastward flowing glacier, older than 5.42 Ma. It containsrare foraminifera and autochthonous dinoflagellates. Reworked nannoflora and palynomorphs from the Lower Cretaceous are recovered. Leal Bluff diamictite (Vega Island) ranges from 5,42 to 2.09 Ma in age. The collected macrofauna is composed by articulated bivalves, pectinids, and mussels. Microbiota is composed by Cretaceous reworked agglutinated foraminifera, abundant  microforaminiferal linings, marine diatoms, dinoflagellates and scarce continental palynomorphs. These are assigned to the Late Miocene-Pliocene. The finding of an opportunistic microforaminifera test linings suggest dysaerobic environments with a high organic matter input. Cape Lamb diamictite (Vega Island) is younger than 2.09 Ma. Its well preserved macrofauna suggests a short distance of transport, and include Adammusium colbecki, brachiopods, gastropods, serpulids, spirorbids, echinoderm spines and bryozoa. A diversified foraminifers assemblage, dominated by Elphidiidae, indicates a myxohaline shelf environment, similar to the Terrapin Formation. Scarce ostracods and Cassulinidae foraminifera suggest cold antarctic waters. Frequent dinoflagellates include Spiniferites ramosus, common in shelf environments. Ekelöf diamictite (James Ross Island) is correlated with Gage Formation (3 to 3.1 Ma). Well preservedmacrofauna includes articulated bivalves, pectinids, brachiopods, serpulids, balanids,gastropods, and bryozoa. Close to the diamictite´s base, foraminifera include Upper Cretaceous reworked species. Topwards, robust shell foraminifera, dominated by Ammoelphidiella antarctica, suggest a littoral environment. Ekelöf biota resembles that of Cockburn Island Formation.