Paper No. 15
Presentation Time: 1:30 PM-5:30 PM
PROVENANCE OF THE COASTAL SAND, GUYANA
Representative sand samples were collected from the coastline located along the downstream section of the Mahaica River. Geographically, sample locations are in close proximity to the town of Bartica, eastern Guyana. Sand samples were analyzed for compositional studies with primary focus on the distribution of heavy minerals and utilization of heavy mineral data for provenance interpretation. Geologically, the sand samples are located within the Guyana Shield and the bedrocks belong to the Proterozoic Bartica Formation consisting mainly of gneiss and granulites. The Bartica Formation is bordered with the Proterozoic greenstone belts to the west and southwest and Trans-Amazonian felsic to intermediate igneous intrusive to the west and south. A prominent east-west trending outcrop of Proterozoic felsic volcanic rocks and granites marks the southern boundary of the Bartica Formation. Preliminary heavy mineral study indicates the presence of two distinctive heavy mineral suites. Samples located close to the downstream section of the Mahaica River are characterized by epidote, zircon, hornblende, augite, and minor hypersthene; whereas, samples located in the south of the Mahaica River are typified by garnet, reddish brown basaltic hornblende, augite, zircon, and hypersthene. The typical reddish brown hornblende has been well-documented by many researchers as a petrological signature tool for northern Brazil provenance. The overall composition and provenance of the sands may in part, have been controlled by the low sealevel stand associated with the last glacial episode when local streams incised deeply into the Proterozoic bedrocks and supplied detritus to the surficial coastal deposits.