THE SIWALIKS OF PAKISTAN - TIME AND FAUNAS IN A MIOCENE TERRESTRIAL SETTING

New correlations are presented for two long sections in the lower Siwaliks showing the value of magnetostratigraphic correlation within the Siwalik depositional setting. Correlation of Potwar fossil localities to those of an East African section, also dated paleomagnetically, are established. The composite biostratigraphy enables definition of sequential biochronologic units without gaps. The history of the Siwalik fauna shows turnover episodes, but they differ in intensity, diversity of groups affected, and coincidence of first and last occurrences, probably reflecting different causes. Studies on the evolution of lineages are rendered more powerful by magnetostratigraphy: temporal control tests patterns of speciation, yields confident estimates on true temporal ranges of fossil taxa, and shows that rodent species longevities exceeded 2 m.y. on average. -from Authors