PETROLOGY AND TECTONIC INTERPRETATION OF THE LOWER SCOTLAND FORMATION (EOCENE), BARBADOS

Petrographic and geochemical studies have been conducted on selected samples from the Lower Scotland Formation (Eocene) of northeastern Barbados, in order to interpret the depositional environment and the tectonic history of the source area. The Lower Scotland Formation is, for the most part, a fine-grained clastic-dominated sequence with occasional thin intercalations of gypsum, ironstone, and kaolinite. Distinctive deep-water-facies have been well-documented in dark gray shale units containing load cast, flutes, grooves and prods. In addition, turbiditic brown sandstone with a sharp erosive base and pelagic caps also characterize the base of the formation. Notable marine faunas include Nummulites, Orbitoids, and occasionally Discocyclina sp. The Lower Scotland Formation has been intensely folded and faulted and, in many places, shows a thrust contact with the Upper Scotland Formation. Petrological studies involved both light and heavy mineral separation, as well as thin section studies. Detrital minerals in the formation include quartz (both monocrystalline and polycrystalline), feldspar (mostly altered), zircon, monazite, tourmaline, rutile, kyanite, augite, and lithic fragments of varied source rocks. Bulk chemical and trace element investigation of the selected samples suggests an overall trend of immobile traces increasing up-section. The Northwestern Venezuelan Shield, located to the south of the study area, acted as the primary source of detritus for the Lower Scotland Formation., Extensive deformation of the Lower Scotland Formation, due to the Andean Orogenic event (Cenozoic), is well-documented in the studied area.