Stable oxygen isotope analysis in Amiantis purpurata shells (BivalviaI, Veneridae): First indications for Late Holocene climate variability in northern Patagonia, Argentina

BAYER, M.S.; BEIERLEIN, L.; BREY, T.; FARÍAS, L.; GARCÍA G.; MORSAN, E.; GORDILLO , S.

Puerto Madryn

Otro; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2018

Asociación Paleontológica Argentina

The shells of several mollusks can provide environmental and climatic information on a seasonal scale. This variability is recorded within the stableoxygen isotope (δ18Oshell) composition of the biogenic shell carbonate. The δ18Oshell values depend on the composition of the sea water(δ18Owater) and changes in water temperature. The bivalve Amiantis purpurata Lamarck has a well-preserved fossil record from the late Holoceneto the present times in the San Matías Gulf (SMG). The goal of this study is to detect the seasonal (δ18Oshell) signals of A. purpurata in order toreconstruct the seasonal water temperatures within the SMG during the late Holocene. Seven shells were radiocarbon dated (14CAMS), eachrepresenting a different time horizon throughout the late Holocene, up to the present. The intra-annual variability of δ18Oshell values was largest in themodern shell (Δδ18Oshell = 2.23?), while the fossil shells (3844-3555 yrs BP) provided the smallest intra-annual amplitude (Δδ18Oshell =1.39?). δ18Oshell values in modern and fossil shells were used to calculate water temperatures based on modern δ18Owater measurements, whichhave not been reported in SMG so far. In general, the reconstructed temperatures fit well into the general assumptions for the coldest and warmestphases throughout the Holocene in SMG. However, we are aware that this study represents a first step towards the calibration of A. purpurata asa new palaeo archive for the Southern Hemisphere and into the climatic history of SMG and Northern Patagonia.