The role of turbidites on compaction and dewatering of underthrust sediments at the toe of the northern Barbados accretionary prism: new evidence from Logging While Drilling, ODP Leg 171A

Recently obtained Logging While Drilling data sets from ODP Leg 171A enable a detailed correlation of sediments among drill sites and an estimate of the change of bulk densities among them. In this analysis, three different lithologies from the underthrust sediments of the Barbados accretionary prism were picked up and volumetric strains were calculated by comparing bulk densities of correlated intervals. Results showed that the interbedded mudstones in turbidites have experienced larger volumetric strain while massive claystones have not. The mudstone beds, sandwiched both above and below by relatively highly permeable sandstones, are interpreted to have undergone dewatering because laterally continuous sandstones have acted as effective drains for dewatering. The existence of the turbidite sandstones in the underthrust package and the migration of warm fluid along the sandstones might explain why high heat flow is observed at the ocean floor at Site 672, where turbidite sandstones exist, but not at Site 543, where turbidites were not deposited.