Deep Structure of the Grenada Basin From Wide‐Angle Seismic, Bathymetric and Gravity Data

Abstract

The Grenada back-arc basin is located between the Aves Ridge, which hosted the remnant Early Paleogene "Great Caribbean Arc," and the Eocene to Present Lesser Antilles Arc. Several earlier studies have proposed different modes of back-arc opening for this basin, including N-S and E-W directions. The main aim of this study is to constrain the circumstances leading to the opening of the basin. Three combined wide-angle and reflection seismic profiles were acquired in the Grenada basin. The final velocity models from forward travel time and gravity modeling image variations in thickness and velocity structure of the sedimentary and crustal layers. The sedimentary cover has a variable thickness between 1 km on top of the ridges to ∼10 km in the basin. North of Guadeloupe Island, the crust is ∼20 km thick without significant changes between Aves Ridge, the Grenada basin, and the Eocene and present Lesser Antilles arc. South of Guadeloupe Island the Grenada basin is underlain by a oceanic crust of mainly magmatic origin over a width of ∼80 km. Here, the western flank of the Lesser Antilles Arc, the crust is 17.5-km thick. The velocity structure of the Lesser Antilles Arc is typical of volcanic arcs or oceanic plateaus. West of the basin, the crust thickens to 25 km at Aves Ridge in an 80-100 km wide arc-ocean transition zone. The narrowness of this transition zone suggests that opening might have proceeded in a direction oblique to the main convergence. Opening probably was accompanied by moderate volcanism.

Genetic Relations Between the Aves Ridge and the Grenada Back‐Arc Basin, East Caribbean Sea

“…Wide-angle seismic (WAS) data along line GA02 reveal a 6.5-7 km-thick crust with a typical oceanic velocity structure underlying the Grenada Basin, over a width of 80 km (Padron et al, 2021). Christeson et al (2008) and Allen et al (2019) also propose a basement of oceanic origin in the southeastern Grenada Basin, based on WAS data along lines BOL30 and VOILA-4, respectively.…”

“…Wide-angle seismic (WAS) data were also recorded along three lines, two of which are shown in Figure 2: one trending E-W across the basin and its margins (GA02) and the other along-strike in the axis of the basin (GA01). The processing and interpretation of the GARANTI WAS data are the subject of a companion paper (Padron et al, 2021).…”

“…VE = 7. (f) Close-up view of line GA02 with a superimposition of the velocity model derived from WAS data (Padron et al, 2021).…”

“…Line GA04 (the latitude of Dominica) roughly marks the boundary between the deep Grenada Basin to the south and a region of shallower, rougher bathymetry to the north (Figure 2). At crustal scale, the boundary is more diffuse, as the crust gradually thickens northwards (Padron et al, 2021). For this reason, we include this area in the transitional domain ( Figure 10).…”

Shedding New Light on an Enigmatic End Member of Back‐Arc Spreading: The Structure of the Grenada Basin in the Lesser Antilles

“…One of the biggest shortcomings in our understanding of the region is how the Grenada Basin, which sits behind the main volcanic arc, formed. In their new paper Padron et al (2021) present new seismic profiles from the region, which reveal very clear changes in the structure of the crust from north to south within the basin. The structure of the crust in the southern basin is similar to that of oceanic crust, suggesting it formed through spreading processes similar to those observed at oceanic ridges.…”