Continental Vertebrates During the Marine Isotope Stage 3 (MIS 3) in Argentina

Abstract

Paleontological sites in Argentina with continental vertebrates corresponding to the Marine Isotope Stage 3 (MIS 3) interval are scarce or poorly known. This situation is mainly due to the lack of absolute ages for Pleistocene fossil remains or their bearing sediments that would allow the verification of the chronology established for this interval. However, a few isolated evidences show that continental vertebrates responded to the abrupt temperature changes that characterized the MIS 3 (Heinrich colder events and Dansgaard-Oeschger warmer events). Up to date, continental vertebrate remains of this age have been found mainly in Buenos Aires province, but also in a few sites of northeastern Argentina (such as Entre Rios, Corrientes, Formosa and Chaco provinces). In Buenos Aires province: (1) Paso Otero, in the Rio Quequen Grande valley, evidence of warmer and more humid conditions were found in sediments dated in 37,800 +/- 2300 radiocarbon years before present (RCYBP); (2) Mar del Sur, General Alvarado County, coastal marine sediments with continental mammals were dated in 25,700 +/- 800 and 33,780 +/- 1200 RCYBP; (3) Balneario Saldungaray, in the Rio Sauce Grande valley, Tornquist County, gastropods associated with mammal remains were dated in 32,300 +/- 1800 and 27,500 +/- 670 RCYBP; (4) Los Pozos, Marcos Paz County, sediments dated between 29,000 and 33,000 RCYBP are associated with remains of mammals, birds, reptiles and amphibians; (5) San Pedro, San Pedro County, sediments bearing vertebrate fauna have two OSL datings of 37,626 +/- 4198 and 41,554 +/- 3756 years B.P. (YBP). In Entre Rios province, Rio Ensenada valley, Diamante Department, some levels of the Tezanos Pinto Formation with OSL datings between 9000 and 35,000 YBP yielded remains of grazer megamammals and other taxa characteristic of the modern Patagonian Domain. In the province of Corrientes, Arroyo Toropi, Bella Vista, vertebrate remains dated with OSL from 36,000 to 52,000 YBP show a clear taxonomic change in response to climatic fluctuations. In Formosa province, Rio Bermejo, Villa Escolar sediments of the Fortin Tres Pozos Formation, bearing vertebrate fauna have an OSL age of 58,160 +/- 4390 YBP. In the province of Chaco, Charata locality, gastropods associated with mammal remains were dated between 22,000 and 27,000 RCYBP. A larger amount of absolute datings of the bearing sediments and especially taxon dates are needed to determine more accurately the response of the fauna to the climate changes characteristic of MIS 3.