Characterization of a loess-paleosols section including a new record of the Last Interglacial Stage in Pampean Plain, Argentina

TÓFALO, OFELIA; ORGEIRA. MARÍA JULIA; COMPAGNUCCI, ROSA; ALONSO, MARÍA SUSANA; RAMOS, ADRIANA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010

0895-9811

  A new record of the Marine Isotopic Stage 5, the last Interglacial Stage before present is presented in this paper. Sedimentological, micromorphological, trace elements analyses (Rb-Sr) and magnetic polarity determination were performed on Buenos Aires and Ensenada Formations (Late Cenozoic) deposits in the southern Chaco-Pampean Basin (Argentina). This work aims to unravel paleoclimatic and paleoenvironmental information from achieved data. The studied deposits encompass a complex and cyclic 8m-thick sedimentary-pedogenetic sequence formed by loessic sediments and paleosols with volcano-pyroclastic provenance. Four tabular units, with net base and top, were defined regarding erosion surfaces. An OSL age >126 kyr was obtained from upper middle part of unit B, which suggests that this unit as well as unit C, could have developed during the latest interglacial stage, equivalent to the MIS 5. The occurrence of calcretes indicates periods of little clastic supply and seasonal arid or semiarid climate while iron oxides, smectites and illite-bearing pedogenetic calcretes point to annual rain rates between 100 and 500 mm. No calcretes of any origin occur at present soils of the same zone. According to the suggested interpretation of the available data, climate during MIS 5 could be drier than today. From a climatological point of view, this could be related to lower temperatures during summer.