The polyphased tectonic evolution of the Anegada Passage in the northern Lesser Antilles subduction zone

Abstract

The influence of the highly oblique plate convergence at the northern Lesser Antilles onto the margin strain partitioning and deformation pattern, although frequently invoked, has never been clearly imaged. The Anegada Passage is a set of basins and deep valleys, regularly related to the southern boundary of the Puerto Rico‐Virgin Islands (PRVI) microplate. Despite the publications of various tectonic models mostly based on bathymetric data, the tectonic origin and deformation of this Passage remains unconstrained in the absence of deep structure imaging. During cruises Antithesis 1 and 3 (2013–2016), we recorded the first deep multichannel seismic images and new multibeam data in the northern Lesser Antilles margin segment in order to shed a new light on the structure and tectonic pattern of the Anegada Passage. We image the northeastern extent of the Anegada Passage, from the Sombrero Basin to the Lesser Antilles margin front. Our results reveal that this northeastern segment is an EW trending left‐stepping en échelon strike‐slip system that consists of the Sombrero and Malliwana pull‐apart basins, the Malliwana and Anguilla left‐lateral faults, and the NE‐SW compressional restraining bend at the Malliwana Hill. Reviewing the structure of the Anegada Passage, from the south of Puerto Rico to the Lesser Antilles margin front, reveals a polyphased tectonic history. The Anegada Passage is formed by a NW‐SE extension, possibly related to the rotation or escape of PRVI block due to collision of the Bahamas Bank. Currently, it is deformed by an active WNW‐ESE strike‐slip deformation associated to the shear component of the strain partitioning resulting from the subduction obliquity.

The Bunce Fault and Strain Partitioning in the Northern Lesser Antilles

“…During the Miocene, the Anegada Passage possibly accommodated transtensive relative motion between Caribbean and PRVI block in response to this collision (e.g., Jany et al, ; Mann et al, ). Later on, this transtensive extension was stopped and the structures are recently reactivated by a left‐laterally partitioning system (Figure ; Laurencin et al, ) as also substantiated by GPS data interpretation (Jansma & Mattioli, ). To the north of the Anegada Passage, the strike‐slip Bowin Fault extends eastward the Septentrional Fault of Hispaniola and connects with the left‐lateral strike‐slip Bunce Fault (Grindlay et al, ).…”

“…(b) Bathymetric map showing location of multichannel seismic data (black lines) and wide‐angle seismic data (colored circles at ocean‐bottom seismometer location) recorded during cruises ANTITHESIS 1 and 3. Structures at the Anegada Passage (thin gray lines) are from Laurencin et al () and the Bunce Fault (thick red line) from this study and ten Brink et al (). Close‐up in Figure are located along thick black lines.…”

Trench Bending Initiation: Upper Plate Strain Pattern and Volcanism. Insights From the Lesser Antilles Arc, St. Barthelemy Island, French West Indies

“…Moreover, we show here that in St. Barthelemy, at least, the late Oligocene is a hinge period during which a switch from pure to radial extension accompanied the inland migration of the Lesser Antilles volcanic arc. This evolution reflects the introduction of a component of trench parallel extension and was followed by a Miocene dextral transtensive opening of the Anegada Trough (Jany et al, 1990;Laurencin et al, 2017) and the subsequent 25°counterclockwise rotation of the PRVI block (north of the Anegada Trough; Figure 8c). Our restoration with these boundary conditions gives a 15°clockwise rotation of the Anguilla Bank that should be tested further using paleomagnetic data, which are unfortunately not yet available south of the Anegada Trough.…”

“…The red lines and letters indicate the seismic lines we restored in section 5.2. (c) Structural map of the Lesser Antilles subduction zone after Feuillet et al (, ) and Laurencin et al (). The gray arrows indicate the convergence rates (DeMets et al, ).…”

“…As the trench is convex, its obliquity increases from a minimum value of 5° at the latitude of Guadeloupe to an obliquity of 77° at the latitude of the Anegada Trough and to nearly pure strike‐slip offshore western Hispaniola (Figure c). Oblique subduction is accommodated by strain partitioning in the Caribbean Plate, which shows a large‐scale sinistral strike‐slip fault along the Greater Antilles, and the Anegada Trough sinistral strike‐slip system links up with the Lesser Antilles (DeMets et al, ; Deng & Sykes, ; Feuillet et al, ; Laurencin et al, ; Stein et al, ). Along the northern Lesser Antilles, the strain partitioning is accommodated by parallel‐to‐the‐trench en echelon faults along the arc and perpendicular‐to‐the‐trench grabens in the forearc (Figure b; Feuillet et al, , , ; Lopez et al, ; Manaker et al, ).…”