A late Cenozoic ‘root bed’, an unconformity and the tectonic history of Carriacou, The Grenadines, Lesser Antilles

Abstract

The Carriacou root beds are rhizolith-bearing deposits of late Cenozoic age; such terrestrial units are rare in the Antilleanrock record. Marine shells within this unit are derived from older deposits. These beds rest with marked angular unconformity on the Middle Miocene Grand Bay Formation. Available evidence indicates that the root beds are post-Pliocene in age, indicating a considerable difference in age to the Grand Bay Formation. This is in marked contrast with Lower-Middle Miocene unconformities of Carriacou, which occurred when the island was an active depositional basin in a tectonically dynamic region. The unconformity between the Carriacou root beds and the Grand Bay Formation supports previous determinations of tectonic quiescence in the Carriacou region since the mid Miocene.