Results and preliminary implications of sixteen fission-track ages from rocks of the western Caribbean Mountains, Venezuela
Published:January 01, 1984
B. P. Kohn, R. Shagam, T. Subieta, 1984. "Results and preliminary implications of sixteen fission-track ages from rocks of the western Caribbean Mountains, Venezuela", The Caribbean-South American Plate Boundary and Regional Tectonics, William E. Bonini, Robert B. Hargraves, Reginald Shagam
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Two rocks of the Tinaco Complex (one here so postulated on lithologic grounds) give zircon ages of 49 ± 6 m.y. and 42.7 ± 5.3 m.y. (mean of two ages). Eleven samples of Peña de Mora gneiss (Caracas Group) and Choroní-Tovar “granite” (gneiss) give zircon ages that cluster closely about a mean of 19.7 ± 2.1 m.y. The bimodal zircon ages are explained by a speculative model involving obduction of the Tinaco Complex over the Caracas Group followed by isostatic rebound after southward passage of the Villa de Cura klippe, which set the older ages. In turn, further block uplift during eastward translation of the Caribbean relative to the South American plate led to the setting of the younger group of zircon ages.
A single sphene age of 126 ± 15 m.y. on Choroní “granite” (gneiss) is best viewed as a partially annealed remnant of a Paleozoic(?) clock in Sebastopol gneiss component of the “granite.” One apatite separate from Tinaco Complex trondhjemite yields an age of 6.1 ± 1.3 m.y., reflecting a phase of uplift also prominent in the circum-Maracaibo Basin ranges to the west.