Calibration of the great american interchange.

  title={Calibration of the great american interchange.},
  author={L G Marshall and Robert F. Butler and Robert E. Drake and Garniss H. Curtis and R H Tedford},
  volume={204 4390},
From radioisotopic (potassium-argon) age determinations of tuffs and magnetostratigraphy of Late Tertiary mammal-bearing beds in Catamarca Province, northwest Argentina, refined estimates have been obtained for the durations and boundaries of beds of Chasicoan (Middle Miocene) through Chapadmalalan (Pliocene) age. An age of 9.0 million years is tentatively accepted for the Chasicoan-Huayquerian boundary, 5.0 million years for the Huayquerian-Montehermosan boundary, and 3.0 million years for the… CONTINUE READING