Taxonomy and climatic zonation of the Late Quaternary bathyal ostracods from the Campos Basin, Brazil

Abstract

This work represents a new contribution to the knowledge on deep-sea ostracods from the western South Atlantic Ocean based on the core GL77 drilled in the Campos Basin (40°02′50″W; 21°12′22″S), 1287m water depth. Radiocarbon dating and oxygen isotopic analyses in planktonic foraminifera indicate that the 275cm interval studied of this core comprises the marine isotope stages 1, 2 and 3 (approximately 45kyr). Forty ostracode species were identified, yet 19 of them are kept in open nomenclature due to either the absence of adult individuals or poor preservation. Thirteen of those species have been recorded previously in the Brazilian continental margin: Bythocypris kyamos, B. affinis, Cytheropteron inornatum, C. perlaria, K. coimbrai, K. morkhoveni, K. sinuosa, K. trinidadensis, Macrocypris adrecta, Microcythere dubia, M. cronini, Poseidonamicus pintoi and Saida ionia. A new Trachyleberididae species, Ambocythere circumporus nov. sp. is proposed, and Cobanocythere? dubia is reassigned to the genus Microcythere. The stratigraphic distribution of the species in the core GL77 was compared to other studies on deep-sea assemblages carried out in the western Atlantic Ocean. The general species diversity pattern is a significant reduction during the Last Glacial Maximum (LGM) followed by conspicuous changes in Holocene assemblages caused by the appearance of species absent in the Pleistocene. The species Bythocypris kyamos, Cytheropteron perlaria and Saida ionia are restricted to the Marine Isotope Stage (MIS) 1. Poseidonamicus pintoi and Australoecia sp. are predominant and almost exclusive to the MIS 2 and 3. These data indicate the possibility of elaboration of an ostracod-based paleoclimatic zonation for the Quaternary of the south/southeast Brazilian margin.