SEDIMENTOLOGY OF THE LOWER SCOTLAND FORMATION (EOCENE), BARBADOS

Representative samples collected from the Lower Scotland Formation (Eocene) outcropping in northeastern Barbados were investigated in conjunction with overall facies distribution and stratigraphic and sedimentological characteristics to interpret depositional environment and provenance of the fine-grained clastics. 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 fauna observed 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. Preliminary compositional 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 microcline), and altered biotite. Heavy minerals include zircon, monazite, tourmaline, rutile, kyanite, and augite. Lithic fragment of varied source rocks are also observed. Bulk chemical and trace element investigation of the selected samples suggests an overall trend of immobile traces including Sr, Ba, and Rb increasing up-section and an overall decreasing silica content 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, the later being subjected to pronounced structural deformation in response to the Cenozoic Andean Orogenic episode.