Pleistocene marine calcareous macro-and-microfossils of Navarino Island (Chile) as environmental proxies during the last interglacial in southern South America

Macro-and-microfossils, including molluscs, cirripeds, echinoids. foraminifers and ostracods are a significant component of a Pleistocene marine unit located along the southern coast of the Beagle Channel, on Navarino Island, Chile. This paleontological record represents the richest and most diverse macro-and-micro assemblage recovered from Pleistocene southern South America. In total, 97 taxa were identified: 34 molluscs, 57 foraminifers, and 6 ostracods. They comprise a mixture of specimens inhabiting shallow marine environments characterized by strong bottom currents and belonging to different local communities associated with the spatial heterogeneity in this basin. The taxonomic composition of this paleofauna shows remarkable similarities with present-day fauna, indicating that both groups developed under similar environmental conditions. However, slight different climatic conditions at the age of deposition cannot be ruled out. As well, an ecosystem transition towards a truly marine environment with high number of taxa was recognized. Finally, a Hiatella-cirriped assemblage deserves special attention since the polymorphic shell of fossil and living Hiatella is used as a paleo-environmental tool. In this regard, the small size of Hiatella in the studied marine unit is best related to its mode of life as a nestler within empty tests of barnacles, which apparently served as microenvironments for this species. Nevertheless, more geochemical data on living and fossil Hiatella shells from the Beagle Channel will be necessary to test the suitability of using this species to evaluate paleo-temperatures and other sea water variations during the Quaternary. (C) 2009 Elsevier Ltd and INQUA. All rights reserved.