Evidence for Quaternary convergence across the North America–South America plate boundary zone, east of the Lesser Antilles

Abstract

New seismic and bathymetric data reveal that the plate boundary zone between the North American and South American plates, east of the Caribbean, has occupied a >200-km-wide zone of localized basement uplift and folding, and of faulting of the sedimentary cover, during the early Pleistocene to Holocene. This zone, which includes the Barracuda Ridge and Tiburon Rise, exhibits north-south compressional structures and continues eastward up to 500 km from the boundary of the Caribbean plate. A sequence of young turbiditedominated sediments fi lls the basin between these two ridges and shows synsedimentary deformation; the base of the sequence is of early Pleistocene age, dated by biostratigraphic correlation with Deep Sea Drilling Project Site 27. Recent deformation in the turbidite-fi lled trough north of the Barracuda Ridge is shown by uplift of the seafl oor at the crests of anticlines, across which the shallowest sediment layers thin or pinch out.

Current block motions and strain accumulation on active faults in the Caribbean

“…This indicates that the South America‐North America relative motion has not varied significantly over the past∼10 Ma. Our model predicts about 1 mm/yr of present‐day N‐S shortening across the Barracuda and Tiburon ridges to the west, consistent with offshore geological data showing thrusting and thrust‐related folding affecting Quaternary sediments along both ridges indicative of north‐south compression [ Patriat et al , ]. This prediction is in closer agreement with geological observations there than other recent estimates [ DeMets et al , ; Argus et al , ] that predict a significant amount of strike‐slip motion that does not appear in the offshore geological data [ Pichot et al , ].…”

“…The Caribbean domain and Central America form a small lithospheric plate inserted between North and South America (Figure ). While the North and South American plates show little relative motion [ Patriat et al , ], the Caribbean plate moves eastward relative to them at 18–20 mm/yr [ DeMets et al , ]. This displacement is accommodated by two major east‐north‐east strike‐slip fault systems along its northern boundary on either sides of the Cayman trough and at its southern boundary along the Oca‐El Pilar fault system.…”

Tectonic and sedimentary architecture of the Karukéra spur: A record of the Lesser Antilles fore-arc deformations since the Neogene

“…Such a process is suggested to explain the large and fast subsidence at the Porto-Rico trench (ten Brink, 2005) whereas, first, McCann and Sykes (1984) proposed margin erosion. A mechanism for a steepening of the slab dip responsible for the Karukéra long term subsidence could be the slow convergence between South and North Americas in the vicinity of the Karukéra margin and that would force the two lithospheres to flex downward (Müller and Smith, 1993;Patriat et al, 2011;Pichot et al, 2012). However such a steepening of the downgoing lithosphere would rather drive the volcanic arc seaward than landward.…”

“…1). They correspond to reliefs of Atlantic Ocean fracture zones that are reactivated in a compressive way as a result of a slow convergence between the North and South America plates at this latitude (Patriat et al, 2011;Pichot et al, 2012). As they subduct westward but trend oblique to the subduction front, the two ridges sweep the subduction zone southward at a rate of 20 km/Ma.…”

How wide is the seismogenic zone of the Lesser Antilles forearc?

“…1. The aseismic ridges appear to mark a diffuse plate boundary between the North and South American plates Patriat et al, 2011]. The sampling boxes for the seismicity cross-sections the co-located thermal models from figure 6 are indicated (black lines), as well as the position of the seismic profiles shown in figure 3 (magenta lines) used to constrain the deep structure.…”