Pleistocene calcareous macro-and-microfossils from the southernmost tip of South America as environmental proxies during the last interglacial period

Abstract

Macro-and-microfossils, including molluscs, cirripeds, echinoids, foraminifers and ostracods area significant component of a Pleistocene marine unit located along the southern coast of the BeagleChannel, on Navarino Island, Chile. This paleontological record represents the richest and most diversemacro-and-micro assemblage recovered from Pleistocene southern South America. In total, 97 taxa wereidentified: 34 molluscs, 57 foraminifers, and 6 ostracods. They comprise a mixture of specimensinhabiting shallow marine environments characterized by strong bottom currents and belonging todifferent local communities associated with the spatial heterogeneity in this basin. The taxonomiccomposition of this paleofauna shows remarkable similarities with present-day fauna, indicating thatboth groups developed under similar environmental conditions. However, slight different climaticconditions at the age of deposition cannot be ruled out. As well, an ecosystem transition towards a trulymarine environment with high number of taxa was recognized. Finally, a Hiatella-cirriped assemblagedeserves 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 toits mode of life as a nestler within empty tests of barnacles, which apparently served as microenvi-ronments for this species. Nevertheless, more geochemical data on living and fossil Hiatella shells fromthe 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.