Vacillatory turbidites, Barbados

A vacillatory turbidite is one containing Bouma sequence divisions that repeat within a bed; it presumably results from a single flow event or several closely-related events (for example, retrogressive slope failure). The most common vacillations or repetitions in such turbidites on Barbados are between T b and T c intervals (T bcbc, for example). Many vacillations are accompanied by gradual to abrupt changes in the content of detrital organic matter. Other vacillations are clearly associated with flow surges, as indicated by intra-bed scours which die out laterally and separate divisions. Vacillatory turbidites may results from: (1) multiple-surging flows, or (2) periodic deposition of concentrations of entrained detrital organic matter which modifies turbulent flow characteristics. Other features associated with vacillatory turbidites on Barbados are fluidized beds, syndepositional deformation features and hummocky cross-beds. Vacillatory turbidites and related features on Barbados occur principally in facies composed of fine-grained sandstone beds with bedding thicknesses greater than 20 cm; mostly in outer fan deposits but rarely in midfan deposits.