Progressive vadose diagnosis in quaternary reef tracts, Barbados, West Indies

The role of time on the diagenetic alteration of reef facies, within the vadose zone on Barbados, has been investigated in this thesis. This study was carried out in Barbados, where coral reef deposits have been extensively dated radiometrically and eight discrete sea level stands ranging in age from 80ka to 640 ka have been identified.;Within this study the following reef zones were identified: the fore reef, the coral head zone, the reef crest, the rubble zone and back reef sands. Sediments were grouped together according to their position within the reef tract to give a greater understanding of the variability which exists within and between deposits.;Petrological analyses of 750 samples in thin section, supplemented by SEM and cathodoluminescence studies have identified a number of diagenetic alteration products. These include the dissolution and replacement of original grains, changes in porosity and cement formation. ICP, XRD, XRF and microprobe studies have also been employed to determine any chemical differences within selected coral samples over time. The research indicates that simplistic models, which are restricted to aeolianites and calcarenites, cannot be directly applied to Barbados.;Reef deposits displayed diagenetic variability at differing scales between coral species and reef sediments within single reef tracts (as well as between different reef tracts). Therefore the role of rock fabric between the coral zones is an important consideration in the identification of sequential changes, and it complicates the application of simple time control models, developed for carbonate sands, that have been developed by others