Late Quaternary nearshore molluscan patterns from Patagonia: Windows to southern southwestern Atlantic-Southern Ocean palaeoclimate and biodiversity changes?

Abstract

Varied approaches (palaeobiodiversity, palaeobiogeography, bioerosion, geochemistry) to unique Patagonian late Quaternary molluscan assemblages in the southwestern Atlantic, with ages especially from interglacial Marine Isotope Stage (MIS) 5e and MIS 1, provide large-scale and long-temporal palaeoenvironmental data for the southern SWA. Together with new patterns of δ 18 O and δ 13 C variations in modern, mid-Holocene, and Late to Middle Pleistocene shells of Protothaca antiqua (Bivalvia) and the coeval Pleistocene Tegula atra (Gastropoda), the overall sources of evidence illustrate possible responses to recent palaeoclimate and sea-ice changes around the southernmost SWA-western Antarctica, leading to modern conditions. For the mid-Holocene, the influence of the Hypsithermal is confirmed. In the northern Golfo San Matías, the highest δ 18 O and δ 13 C values support higher salinity and sea surface temperatures (SST), and a Golfo San Matías Front stronger than today. Lower δ 18 O values in the northern Golfo San Jorge (GSJ) compared to the Late to Middle Pleistocene suggest warmer mid-Holocene waters, independently supported by thermally anomalous molluscan taxa, geographical shifts of areas of endemism and absence of T. atra (cold water proxy); overall higher δ 13 C values compared to present suggest higher productivity. For the Late to Middle Pleistocene (particularly MIS 5e), highest δ 13 C values (relative to modern and mid-Holocene trends) match with the location of tidal fronts and areas of maximum chlorophyll-a concentrations today. Accordingly, these fronts may have been already active and significantly intensified due to the prevailing climate conditions that included colder waters and stronger upwelling from the southern GSJ southwards. This is independently supported by palaeobiogeographical and bioerosion trends and the dominance of the cold water species T. atra during the Pleistocene, which is dispersed from the SE Pacific

Bioerosion ichnodiversity in barnacles from the Ross Sea, Antarctica

“…Few studies were conducted in the cold-temperate region Patagonia (e.g. Ituarte et al 2005;Malumián et al 2006;Richiano et al 2017;Aguirre et al 2019) and in the polar region Antarctica. Bioeroded traces were observed on Seymour Island, Antarctica (Casadío et al 2001(Casadío et al , 2007, and bioerosive activities were recorded in the Ross Sea in scallops and molluscs (Alexander and DeLaca 1987;Cerrano et al 2001;Hancock et al 2015), and sub-fossil skeletal material (Frank et al 2014(Frank et al , 2020.…”

Late Quaternary climatic variability in northern Patagonia, Argentina, based on δ18O of modern and fossil shells of Amiantis purpurata (Bivalvia, Veneridae)

“…This is partially evidenced by the steady stream of special issues on the subject (Schöne and Surge, 2005;Gröcke and Gillikin, 2008;Oschmann, 2009;Wanamaker et al, 2011;Schöne and Gillikin, 2013;Black et al, 2017;Butler and Schöne, 2017;Prendergast et al, 2017;Butler et al, 2019;Gillikin et al, 2019 and that issue). However, only a few studies were performed in the Southern Hemisphere and in South America in particular (Carre et al, 2005;Yan et al, 2012;Gordillo et al, 2011Gordillo et al, , 2015Rubo et al, 2018;Aguirre et al, 2019).…”

Stable Oxygen and Carbon Isotope Composition of Holocene Mytilidae from the Camarones Coast (Chubut, Argentina): Palaeoceanographic Implications

“…Such efforts have been strongly influenced by the local mixture between continental and marine waters, overprinting possible isotopic effects related to regional changes in the oceanic circulation [15][16][17][18][19][20][21]. Recent data from Patagonia have been focussed on isotopic sclerochronology [22,23], which gives information on annual variability, whereas no clear interpretation has emerged from the study of bulk samples [23]. In this paper, we discuss the stable oxygen and carbon isotope geochemistry of living and of Holocene shells of Mytilidae collected in sections situated near the Camarones village (Chubut, Argentina; Figure 1a-c).…”