Cenozoic Microbiotas from the eastern sector of the James Ross Island Group, Antactic Pninsula

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

Conferencia; 4th Open Science Conference, XXXI SCAR; 2010

Cenozoic fossiliferous deposits are analyzed in several localities of Vega and James Ross islands, focusing on their micropaleontological content. Sandwich Bluff diamictite (Vega Island) is a basal till deposited by a eastward flowing glacier, older than 5.42 Ma. It contains rare 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 preserved macrofauna 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.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 preserved macrofauna 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.