Date of Award
Master of Science (MS)
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, Suzanne Louise, "Fission track dating of detrital zircons from the Scotland Sandstones, Barbados, West Indies" (1984). Geology Theses and Dissertations. 8.