Fine-grained Paleogene terrigenous turbidites in Barbados

Abstract Over 1,000 muddy beds were analyzed to determine variations in sequences of sedimentary structures between various fan facies associations in the Paleogene terrigenous turbidites exposed on Barbados. Terrigenous muds of the study area exhibit textural and compositional similarities to fine-grained turbidites accumulating in the deep sea today. A coding scheme was developed in the field in order to tabulate common and recurring sedimentary subunits of Bouma Tcde intervals. Markov chain analyses were performed on 100 vertically successive beds per facies association to determine the significance of various transitions of sedimentary subunits in the Tcde intervals. Although variation in sequences of sedimentary structures within associations is great, discriminating differences are observed. Key variations are 1) presence of starved ripples in mud-rich sections of the middle fan and rarity elsewhere, and 2) variation in thickness of green hemipelagic muds, whose thickness is greatest in the inner-fan and basin-plain environments and thinnest in the middle fan. Enigmatic thinning-upward microcycles of four or more muddy turbidite beds occur commonly in outer-fan and basin-plain associations on Barbados.