Sedimentary, volcanic, and tectonic processes of the central Mariana Arc: Mariana Trough back‐arc basin formation and the West Mariana Ridge

Abstract

[1] We present new multichannel seismic profiles and bathymetric data from the central Marianas that image the West Mariana Ridge (WMR) remnant arc, both margins of the Mariana Trough back-arc basin, the modern arc, and Eocene frontal-arc high. These data reveal structure and stratigraphy related to three periods of arc volcanism and two periods of arc rifting. We interpret the boundary between accreted backarc basin and rifted arc crust along the Mariana Trough and support these findings with drilling results and recent seismic refraction and gravity studies. We show that with the exception of a few volcanoes behind the volcanic front that straddle the boundary between crustal types, the modern Mariana Arc is built entirely on rifted arc crust between 14 and 19°N. Our data indicate that there is more accreted back-arc seafloor to the west of the Mariana Trough spreading axis than to the east, confirming previous evidence for an asymmetric basin. The rifted margin of the WMR remnant arc forms a stepped pattern along the western boundary of the Mariana Trough, between 15°30 0 and 19°N. In this region, linear volcanic cross chains behind the WMR are aligned with the trend of Mariana Trough spreading segments, and the WMR ridges extend into the back-arc basin along the same strike. These ridges are magmatic accommodation zones which, to the north along the Izu-Bonin Arc, punctuate tectonic extension. For the WMR we hypothesize that rift basins are more commonly the sites where spreading segment offsets nucleate, whereas magmatic centers of spreading segments are sites where magmatism continues from arc volcanism, through rifting to back-arc spreading. The Mariana Trough is opening nonrigidly and is characterized by two predominant abyssal hill trends, NNW-SSE in the north and N-S in the south. Between the only two basin-crossing fracture zones at 15.5 and 17.5°, N-S axes propagated north at the expense of NNW axes.

Upper Plate Stress Controls the Distribution of Mariana Arc Volcanoes

“…Rose diagrams show that fault orientations are perpendicular to the backarc spreading direction (Figure ). This is consistent with the interpretation of Oakley et al () that the faults are associated with spreading. The arc‐segment azimuths are subparallel to the fault orientations.…”

“…The backarc spreading rates are 15.9 ± 6.6 mm/year with an azimuth of 57.8° ± 19.9° near Agrigan at the center of the arc, with a maximum rate of 44.6 ± 2.7 mm/year directed toward 97.1° ± 4.1° near Guam in the south (Kato et al, ). This study also showed lateral, N‐S motion in the residual data, which aligned with the model of spreading developing in the center of the trough propagating to the north and south (Martínez et al, ; Oakley et al, ).…”

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

“…10 Ma) of the arc compared to the more complex, longer-lived Tonga-Kermadec, Mariana and Izu-Bonin intra-oceanic arcs (Ishizuka et al, 2003; I.J. Oakley et al, 2009;Wysoczanski et al, 2010). Most of the volcanic front volcanoes have summits 3.0-3.5 km above base levels, which are deeper in the north (2500-3000 m) than in the south (2000-2500 m).…”

Classifying Pacific islands

“…In the southwest Pacific, the three types are geographically separated in Solomon Islands and Vanuatu (Greene and Wong 1988;Petterson et al 1999). More common are en echelon lines of limestone (forearc) and volcanic islands running parallel to an adjacent trench axis, such as are found in Tonga and the Marianas islands (Nunn 1998b;Oakley et al 2009). In their simplest expression, usually where subduction began only comparatively recently, a single line of young volcanic islands is found; examples are found in the Aleutian and Kurile groups in the northernmost Pacific as well as parts of Papua New Guinea (Prueher and Rea 2001;Silver et al 2009).…”