FISSION-TRACK AGES FROM ROCKS OF THE CIRCUM-MARACAIBO REGION OF WESTERN VENEZUELA AND EASTERN COLOMBIA AND THEIR TECTONIC IMPLICATIONS.

Abstract

A total of 101 fission-track ages have been determined on 43 apatite, 40 zircon and 4 sphene concentrates from 47 rock samples collected from the Andes, Toas Island and the Sierra de Perija, all of western Venezuela and the Santander Massif of eastern Colombia. Apatite ages range from ca. 1. 4-27 Myr and all are interpreted as cooling ages related to uplift and erosion of cover rocks. Zircon ages range from ca. 50-172 Myr. Sphene dates are also interpreted as mixed ages. The regions sampled in this study are among the principal tectonic elements of a triangular continental block with apex in Santa Marta, Colombia and the Oca and Santa Marta-Bucaramanga faults as sides. It is suggested that T..