Results of fission track dating of detrital zircons from the Scotland sandstones, Barbados, yield a mixture of ages with several strong groupings from 20-80 Ma, 200-350 Ma, and greater than 500 Ma. Metamict grains were assumed to fall into the greater than 500 Ma population.
The youngest population indicates that the Scotland beds, previously dated by paleontologic methods as Eocene, may actually be as young as late Oligocene. These ages better constrain the timing of deposition for these sediments and support the proposal that the late middle Eocene - early Oligocene Oceanic Fm has overthrust the Scotland beds. This population (20-80 Ma) may reflect material derived from the adjacent arc, the Netherland-Venezuelan Antilles arc, and the Caribbean Mountains of Venezuela. The 200-350 Ma population may reflect partially annealed cratonic material, an Andean component, and/or material associated with a Triassic rifting event. The oldest population (>500 Ma) and metamict zircons were very likely derived from the South American craton. 40Ar/39Ar age spectrum analysis of detrital feldspar from sample 22 provides additional evidence of a cratonic source for these sediments.
Based on results from this study, distribution of glaucophane, and paleogeographical constraints it is proposed that the source area for the Scotland sediments of Barbados was an area of the Guayana shield which was drained by the Unare (proto-Orinoco?) river system and deposited in a submarine fan north of the Unare depression.
Baldwin, S.L., 1984. Fission track dating of detrital zircons
from the Scotland Sandstones, Barbados, West Indies. Unpublished
MSc. thesis, State University of New York at Albany. 97 pp.,
+viii; 1 folded plate (map)
University at Albany Science Library call number: SCIENCE Oversize (*) QE 40 Z899 1984 B35
text) - 6.5MB pdf file
Plate 1 - Geology of the Scotland area, Barbados, and sample localities
(uncoloured geological map, 1:20,000 scale) 1.5MB pdf file [map position Google Earth kmz pin; kmz linked polygon]
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Geological Sciences Program, University at Albany