FLYNN, JOHN J., Department of Geology, Field Museum of Natural History, Chicago, IL; and CARL C. SWISHER, III, Institute of Human Origins, Berkeley, CA

ABSTRACT: Cenozoic South American Land Mammal Ages: Correlation to Global Geochronologies

Remarkable strides have been made in integrating Land Mammal Ages into geochronologic studies since Evernden et al. (1964) published their landmark paper. However, understanding of the temporal sequence and range of geographic applicability (intracontinental, or only regional) of South American Land Mammal Ages (SALMA's) has lagged well behind that available for North America and Europe. Extensive recent work in classical sequences in Argentina, as well as fossiliferous sequences in other South American countries (esp. Chile, Bolivia, Colombia, Brazil), is resulting in a much better understanding of the temporal correlation of South American Land Mammal Ages to global geochronologies.

We will discuss our recent studies integrating high-precision radioisotopic dates (40Ar-39Ar; on high-temperature igneous minerals), mammalian biochronology, magnetic polarity stratigraphies, and tie-ins with intertonguing sequences containing marine biochronologic information, and we will present a new, more accurate, and finely resolved correlation of the SALMA sequence to standard global geochronologies. Integrative studies provide increased precision of numerical dating of horizons within individual sequences, resolution of temporal patterns of stratigraphic and evolutionary changes within sequences, better temporal correlation of local biostratigraphies (within and between biogeographic subregions of South America), revision of the standard sequence of SALMA's, and calibration of SALMA's relative to global geochronologies. Events in the South American terrestrial stratigraphic record have profound implications for understanding the nature and scope of geologic, environmental and climatic changes across the Earth during the Cenozoic.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.