Neotectonics and subsidence of the northern Puerto Rico–Virgin Islands margin in response to the oblique subduction of high-standing ridges

Abstract

High-resolution single-channel seismic refl ection profi les, bathymetry and sidescan sonar imagery from the Puerto Rico trench document the present-day and postcollisional effects of the obliquely subducting southeastern extension of the Bahama Province and the Main Ridge fracture zone on the northern Puerto Rico-Virgin Islands margin. In contrast to an orthogonal system, where it is unlikely that two high-standing ridges will impact the same section of margin, along the Puerto Rico trench convergence is highly oblique and the deformational effects of the two ridges are superimposed and often diffi cult to isolate. A middle-upper Miocene margin-wide unconformity in the Oligocene-lower Pliocene shallow-water carbonate platform of the Virgin Islands, Puerto Rico, and eastern Hispaniola provides an excellent horizontal reference frame for the timing and impact of the high-standing ridges on the margin. During the past 10 m.y., trenchward tilting (4-6°) of the carbonate platform including the margin-wide erosional surface to >5000 m water depths provides evidence that the margin has experienced signifi cant subsidence. In this paper we present a model of accelerated subduction erosion and diachronous margin subsidence triggered by the ridges sweeping from east to west beneath the Puerto Rico forearc. Evidence for ongoing and past subduction erosion include zones of enhanced seismicity, oversteepening and mass wasting of the forearc slope, and landward migration of the inner trench-slope break. We document over 3 km of Neogene subsidence presumed to be the result of rapid crustal thinning associated with the tunneling of the

Geomorphic and stratigraphic evidence for an unusual tsunami or storm a few centuries ago at Anegada, British Virgin Islands

“…Anegada adjoins the edge of a submarine slope that descends nearly 8 km to the floor of the Puerto Rico Trench, 125 km to the north (ten Brink et al 2004;Grindlay et al 2005).…”

“…This platform was largely subaerial during glacial-age lowstands of the sea (Dunne and Brown 1979). North of Puerto Rico the platform is composed of Oligocene and Miocene carbonate strata that tilt toward the trench, perhaps in response to a tear in the subducting plate (ten Brink 2005) or in response to subduction erosion (Grindlay et al 2005). …”

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

“…[87] Mann et al [2002] and Grindlay et al [2005] describe the pattern of deformation in Puerto Rico subduction-collision transition area using GPS data, geologic information and a previously published paleomagnetic study by Reid et al [1991] ( Figure A19). Oblique collision of the bathymetric high of the southeastern Bahama carbonate platform with the Caribbean plate occurs in Hispaniola (to the west of Puerto Rico) while normal subduction occurs adjacent to Puerto Rico and the Virgin Islands.…”

From incipient island arc to doubly‐vergent orogen: A review of geodynamic models and sedimentary basin‐fills of southern Central America

“…However, data from the northeastern Caribbean region and sandbox models imply that a backarc fold‐and‐thrust belt can be regarded as retrowedge and a reversal of the subduction polarity or a mantle‐driven trenchward motion of the overriding plate is not required to produce this structure (ten Brink et al, ). Grindlay, Mann, Dolan, and van Gestel () show a comparable situation with a doubly‐vergent arc structure at the Puerto Rico‐Virgin Islands margin. Here, this doubly‐vergent structure is produced by the thick Bahamas platform that entered the subduction zone, analogous to the situation at the Solomon Islands.…”