FIVE DECADES OF COMPLEMENTARY VERTEBRATE PALEONTOLOGY AND RADIO-ISOTOPIC GEOCHRONOLOGY RESEARCH IN MEXICO: RESULTS AND PERSPECTIVES

The advent of radio-isotopic dating at accessible prices occurred in the early 60’s induced an extensive cooperative effort to date key sequences that bear fossils, which allowed to place biotic events into the every-day time frame, and to make more precise long-range correlation, thus catapulting a qualitative leap in Earth Sciences. Paleontology of terrestrial vertebrates benefited much from it, having the chance to calibrate bioevents, establish “quantitative” taxon-ranges, and make more dependable inter-regional/continental/global correlations. Here we want to review the Geochronology-Vertebrate Paleontology endeavor in Mexico, highlighting results, their importance, and possible future venues.

The late J.W. Wilson and the senior author, then his student, started this effort in the late 60’s, dating the potentially mammal-bearing, Yanhuitlán Formation [Southeastern Mexico = SEM], which much later yielded the southernmost Eocene fauna of North America. The systematic endeavor to date Tertiary mammal-bearing units was pioneered too by the senior author, with the cooperation of F. McDowell [Univ. Texas], thus dating Miocene sequences/faunas [= s/f] in Oaxaca and Chiapas [SEM]. A parallel endeavor to date Late Miocene-Pliocene s/f from basins across the Trans-Mexican Volcanic Belt [= TMVB] was developed by O. Carranza [former student] and his associates from Utah.

Other efforts to date s/f gave these data: one Late Pliensbachian [Sierra Madre Oriental = SMO], one Late Campanian [Peninsula de Baja California], one early Eocene [Central Plateau = CP], one Late Miocene [SMO], and ~20 Pleistocene scattered across the country [Northwestern Plains and Sierras, CP, TMVB (most), Sierras Madres del Sur and de Chiapas]. The results of the s/f datings have improved understanding of tectonic evolution [e.g. central-eastern Pangea (Jurassic), Baja California (Cretaceous), north-central Mexico (Laramide Orogeny), SEM (Eocene-Miocene)], of key paleobiotic events [e.g. Great American Biotic Interchange, Cenozoic evolution of the mammal fauna in southern North America]; and the Pleistocene/Holocene environmental change. Yet, much has to be done on these and other subjects e.g intensive s/f dating in other morphotectonic provinces, Pleistocene dating outside the TMVB, humans-direct dating.