Environmental changes in the Pampean area of Argentina at the Matuyama-Brunhes (C1r-C1n) Chrons boundary

The so-called Pampean sediments an the uppermost sedimentary levels of the Chacopampean basin. They record the sequence of geologic changes that occur red during the late Cenozoic. In the Pampean area, the most important envir onmental and faunistic changes occurred close to the end of the Matuyama Ch ron and beginning of the Brunhes Chron. The relatively wet climate recorded in the region at the end of Matuyama Chron turned to drier and colder cond itions during the beginning of the Brunhes Chron, which also seems to be ch aracterized by an important volcanic activity in the Cordillera de los Ande s. An important faunistic turnover (between Tolypeutes pampaeus and Megathe rium americanum biozones) coincides with lithostratigraphic changes (betwee n the Ensenada and Buenos Aires formations). The change of polarity Matuyam a-Brunhes is observed below this boundary. (C) 2000 Elsevier Science B.V. A ll rights reserved.