Tectonic control on sedimentary processes in the southern termination of the Barbados Prism

Abstract

The purpose of this paper is to evaluate the tectonic control on the origin, nature, distribution and reworking of sediments on an active margin. The study is based on Kullenberg cores, 3.5-kHz seismic profiles and Side-scan Sonar imagery collected on the South Barbados Accretionary Prism, together with observations from submersibles. The most abundant surficial sediment in this area was derived from the South American continent and from hemipelagic particles. This sediment is transported in great quantity through canyons that exemplify the regional tectonic trend and is trapped in basins located between the active accretionary ridges and the other elevated structures, as shown by on-lap geometry and progressive discordances. A second type of sediment consists of clayey diapiric material that originates from Miocene beds. This material is extruded to the surface through mud volcanoes, mud domes and diapiric ridges. The vertical migration of clays was partly initiated by tectonic deformation and guided by major faults. The supply of this diapiric material to the sedimentation in adjacent basins is quite substantial. The last type of sediment consists of diagenetic crusts formed on the sea-floor along faults, where fluids are expelled from the prism. Patterns of reworked sediments are strongly controlled by recent tectonic deformation. Sedimentary features such as bulges, sliding masses, continuous or discontinuous scarps and other erosional lineations are directed parallel to the active tectonic trends (N10–30 °, N50 °, N100–110 °, N140 °). Sliding and other gravity flows are triggered by tectonic activity, mainly where accretion and shear structures interplay and where the ascent of diapiric structures is responsible for steep slopes. The breakup of diagenetic crusts is caused by faulting. Erosive cascading deep currents are enhanced by the high relief afforded by an active ridge.