Palaeomagnetic and Palaeontological records in loess-like Pleistocene-Holocene sediments in the Estadio Ciudad de La Plata , Buenos Aires Province, República Argentina

Abstract

Quaternary sediment layers exposed in a cave in the Estadio Ciudad de La Plata S 34^o 57´ 00´´ W 57^o 57´ 40´´, were studied by applying conventional palaeomagnetic methodology. Vertebrate fossils found at the base of the sedimentary sequence correspond to Scelidotheriinae ind., Doedicurus sp. and Panochthus intermedius . the last being the largest Glyptodontidae found in the area. Palaeomagnetic measurements carried out on the profile indicate that the mammal fossils occur within the Matuyama Reverse Polarity Chronozone (>0,78 Ma). The Brunhes/Matuyama boundary was identifed at 4,6 m below the surface of the present soil, so this record of the Brunhes Zone is the shortest normal polarity record obtained in the area of La Plata. Just like in other studied localities, the Upper Matuyama Polarity Zone coincides with development of soils (humidity) and the lower Brunhes is represented by loess and loess-like deposits corresponding to drier climate associated with a glacial stage in the Cordillera and Patagonia.