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Antigua is a small island at the northern end of the Lesser Antilles chain. Its geology is largely limited to the Upper Oligocene and it records with unusual fidelity the transition from island arc volcanism to quiescence and limestone deposition. Despite the apparent limitation of a rock record confined to a short stratigraphical interval, Antigua has a geodiversity that ranges from thick andesites through silicified logs and freshwater snails in cherts to limestones that include both shallow and deeper water facies, and fine karstic features. [ABSTRACT FROM AUTHOR]

Carriacou, a small island in the Grenadines, Lesser Antilles, has a Cenozoic rock record that has been important in interpreting the geologic history of the Southern Lesser Antilles Arc Platform. The Lower-Middle Miocene sedimentary succession of the southeast and east coasts, consisting of the Belmont, Kendeace, Carriacou and Grand Bay formations, has been interpreted as a shallowing-upward sequence from turbidite basin to nearshore?/beach? palaeoenvironments. An earlier interpretation of the Belmont Formation as having been deposited in shallow water is at variance with the turbiditic nature of the succession; the included fossils are considered allochthonous. However, an interpretation of the Grand Bay Formation as deep water is supported by multiple lines of evidence, including sedimentology (turbidites), ichnology (autochthonous association of burrows typical of deep-water environments) and palaeontology (terrestrial, planktic, and shallow and deep water benthic species mixed together). The minimum depth of deposition of the Grand Bay Formation was 150-200 m. This suggests that the (unseen) contact between the Carriacou and Grand Bay formations is either an unconformity, formed following rapid deepening of the basin, or a fault, the Grand Bay Formation being deposited in a separate basin from the shallowing-upwards Belmont-Kendeace-Carriacou formations, against which it is now juxtaposed [ABSTRACT FROM AUTHOR]