Effects of Subducting Bathymetric Highs on Variations in the Wedge Taper Angles of the Barbados Accretionary Prism.

Abstract:

Variation in the critical taper of an accretionary prism is a function of the wedge properties, pore fluid pressure, slab dip, strength of the fault, incoming sediment thickness, and bathymetric highs. This study focuses on changes on the critical taper of the Barbados accretionary prism, the world’s largest submarine prism, in response to the oblique subduction of three, elongate, basement highs formed along Central Atlantic, oceanic fracture zones: the Tiburon Rise, the Barracuda Ridge, and the St. Lucie Rise. We map the effects of the subducting basement highs on the critical taper as defined by the acute angle created by the bathymetric slope of the prism (measured from GEBCO 2020 data and the dip angle of the base of the prism (measured from a grid of seismic reflection data to a depth of 10 km from the sea surface). The resulting wedge taper measurements at a spacing of 200 km over an along-strike distance of 1000 km along the deformation front of the prism provide reveal the effects of bathymetric highs on wedge taper angles that include: 1) closer spaced and imbricated thrust faults and associated folds along the deformation front that internally deform the prism (critical wedge angle from 1°-1.5°); 2) damming of the sediment supply along the southward slopes of the fracture zone ridges produce abrupt increases frontal accretion that in turn increases the wedge taper over short distances (critical wedge angle from 1°-0°). Areas The constant, sweeping migration of multiple oceanic fracture ridges along the Barbados deformation front means that the prism rarely, if ever, attains a critical state of equilibrium.