A PROVISIONAL AMINOSTRATIGRAPHICAL FRAMEWORK FOR LATE QUATERNARY MARINE DEPOSITS IN BUENOS-AIRES PROVINCE, ARGENTINA

Amino acid analysis was carried out on 5 bivalve taxa (Mactra isabelleana, Corbula patagonica, Tagelus plebeius, Macoma uruguayensis and Noetia bisulcata). Data from the two most common (Mactra isabelleana and Corbula patagonica) are reported in detail. Samples were collected from Holocene shorelines (ca. 2000-6890 C-14 yr B.P) along ca. 350km of the Buenos Aires Province, Argentina. The aminostratigraphy is in general agreement with the palaeoecological evidence and radiocarbon ages. The deposits of the area of Punta Indio-Punta Piedras in the north, which show the highest D/L ratios, have a different geometry and a molluscan fauna of warmer water affinity than the remaining beach ridges, and must be older. They could correspond with the climatic optimum ('Hypsithermal'). The deposits of Samborombon and Mar Chiquita probably started accumulating immediately after deposition of the Punta Indio-Punta Piedras deposits. Deposition at Mar Chiquita appears to have continued longer than at Samborombon. Older D/L ratios from pre-Holocene marine deposits are difficult to interpret without geochronological calibration.