TECTONIC IMPLICATIONS OF CRETACEOUS-PLIOCENE FISSION-TRACK AGES FROM ROCKS OF THE CIRCUM MARACAIBO BASIN REGION OF WESTERN VENEZUELA AND EASTERN COLOMBIA
R SHAGAM, PO BANKS, BP KOHN, LE DASCH, R VARGAS, GI RODRIGUEZ, N PIMENTEL
GEOLOGICAL SOCIETY OF AMERICA MEMOIRS | GEOLOGICAL SOC AMERICA | Published : 1984
A total of 56 fission-track ages are reported for 21 apatite, 19 zircon and 2 sphene concentrates from 24 rock samples collected from Toas Island (3) and the Sierra de Perija (9), western Venezuela, and from the Santander Massif (12), eastern Columbia. All apatite ages, set by cooling on uplift, date points on uplift curves. Ages range 3-27 m.y. When combined with apatite data for the Venezuelan Andes, it is concluded that Tertiary uplift became progressively greater and occurred at faster rates but through shorter time spans. Zircon ages range approx 50-126 m.y. Two zircon dates from Toas and the Perijas may give original crystallization ages of felsic volcanics as 120-122 m.y.-V.N.F.