LOS ESTRATOTIPOS DE LOS PISOS MONTEHERMOSENSE y CHAPADMALALENSE (PLIOCENO) DEL ESQUEMA CRONOLÓGICO SUDAMERICANO

Abstract

The stratigraphic section at the Baliza Monte Hermoso (near Punta Tejada, 17 km to the west of Pehuen-có, provincia de Buenos Aires, Argentina) has been known since Darwin 's voyage. The section is remarkable because the typic Montehermosan and the lower par! of Chapadmalalan crop out there and abundant mammals are recorded. Recently, Zavala (1993) and Zavala and Navarro (1993) revised the geology of the area. We disagree in several points with the conclusions of those authors: 1) we accept the biostratigraphy as a base for chronostratigraphic units, and 2) we found a clear biostratigraphic pattern at the section of Baliza Monte Hermoso with two Pliocene zones. These biostratigraphic units are the material basis for the Montehennosan and possibly for the lower Chapadmalalan. We also discuss the correlation of the Monte Hermoso Formation with other units in Buenos Aires province.