Abstract

Fission-track ages indicate that zircon in Jamaican bauxite and terra rossa comes from multiple sources ranging in age from Late Cretaceous to late Miocene. Miocene-age zircons in the plateau bauxites of northern and central Jamaica were deposited by direct airfall with volcanic ash. Zircons older than Miocene have been recycled principally from Late Cretaceous to middle Eocene igneous and metamorphic rocks. The time of deposition of the principal bauxite parent material is inferred to be between 25 and 8.5 m.y. using the youngest age frequency mode of zircon in bauxite as the older limit and the isotopic age of a nearby bentonitic bed as the younger limit. Fission track data support the theory that the principal parent material of bauxite was Miocene volcanic ash. While this conclusion appears generally valid for the higher grade plateau bauxites, some of the lower grade graben bauxites and nonore-grade terra rossa soils are apparently lateritically altered alluvial deposits recycled from Late Cretaceous to middle Eocene primary rocks now exposed in several inliers.

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