Sediments and Diagenesis
A facies analysis of 200 samples of Holocene carbonate sediments from the waters around Barbuda was based on their constituents and proportions of fine-grained sediments. Cluster analytical techniques were used to define the facies.
Three major facies are coralgal (A), pelletoidal (B), and mixed mollusk (C), each with several subfacies. The coralgal facies is restricted to the reef and backreef environments; the pelletoidal facies occurs predominantly in shallow-water localities with moving substrates; and the mixed-mollusk facies is mainly confined to the lagoon, with minor development in low-energy offshore areas.
Forty-five samples of Barbudan limestone of Pleistocene to possibly Eocene age were introduced into a modified classification framework derived from the Holocene sediments. For this analysis, the proportions of fine-grained sediments were removed from the classification because of the difficulty of differentiating depositional from diagenetic micrite in the limestones. The limestones, for the most part, fitted into the classification. The Pleistocene limestones (Codrington Limestone) occurred predominantly within the pelletoidal and mixed-mollusk facies, whereas the Tertiary (?) limestones (Highland Limestone) were classified as mainly coralgal facies. However, an entirely separate subfacies (A3) in the Highland Limestone is considered to be, in part, a diagenet-ically modified subfacies.
Figures & Tables
Reefs and Related Carbonates—Ecology and Sedimentology
Studies in Geology 4: Reefs and Related Carbonates–Ecology and Sedimentology