Bandy, Betsy; Jackson, Trevor A.; Scott, Peter W.
Author Affiliation, Ana.
Department of Geography and Geology
Mineralogy of the sand-sized sediments in the Rio Minho drainage basin, Jamaica
Jackson, Trevor A.
Caribbean geology into the third millennium: Transactions of the fifteenth Caribbean Geological Conference
Place of Publication
The University of the West Indies Press
Date of Publication
Series Editor Role
Series Volume Identification
Series Issue Identification
The Rio Minho flows from the modern section of the Parish of Clarendon, Central Jamaica, southwards across the Vere Plains. It drains an area of about 1600 km2 and is composed primarily of Cretaceous igneous, volcaniclastic and siliciclastic rocks, and Tertiary carbonates. From the mouth of the river a westerly longshore current along the south coast transports the sediments. The river sediments contain boulders, cobbles, sand-and silt-sized particles, whereas the beach sediments are mainly of sand. This study examines the mineralogy of the sand-sized sediments in the river and coastal sediments as far west as Alligator Pond. The results are compared with the mineralogy of rocks that were collected in the Rio Minho drainage basin in order to determine the provenance of the sands. Samples were collected from the river and along the coast by the grab sampling method. These samples were subsequently wet sieved and the sand-sized fractions were examined using transmitted light microscopy, reflected light microscopy, X-ray diffractometry (XRD) and scanning electron microscopy (SEM) with X-ray analysis. The results obtained on sand and rock samples from this drainage basin show a number of similarities in mineralogy and mineral chemistry. The opaque minerals plot largely along the ulvospinel-magnetite tieline, the pyroxenes plot as augites and the amphiboles, although variable, are mainly calcic. The similarity in mineral composition of the heavy minerals both within and outside of the Rio Minho drainage basin indicates that the Central Inlier was the dominant source of the mineral sands along the south coast of Jamaica and west of the mouth of the Rio Minho. The majority of the minerals appear to have been derived from Cretaceous volcanic arc rocks that crop out in the Central Inlier.....