Rapid forearc uplift and subsidence caused by impinging bathymetric features: Examples from the New Hebrides and Solomon arcs

Abstract

Isotopically dated corals from the central New Hebrides and New Georgia Island Group, Solomon Islands, indicate that both forearcs underwent rapid late Quaternary subsidence that was abruptly replaced by hundreds of meters of uplift at rates up to ∼8 mm/yr, while total plate convergence was only a few kilometers. Two mechanisms that might account for these rapid reversals in vertical motion include (1) a “displacement” mechanism in which the forearc is displaced upward by the volume of an object passing beneath on the subducting plate (as the object moves deeper and vacates the base of the forearc, the forearc subsides to near its original position) and (2) a “crustal shortening” mechanism in which the forearc thickens and uplifts because of horizontal shortening when a large object impinges on the forearc and abruptly increases interplate coupling on the shallow end of the main thrust zone. Rapid subsidence follows when the impinging object is broken or otherwise decoupled, shallow interplate coupling becomes weak, and the uplifted forearc extends and subsides. The displacement mechanism surely plays a role on timescales over which plates converge tens of kilometers, but it fails to explain the geographic pattern, short time frame, and abruptness of the change from subsidence to uplift that we observe. The crustal shortening mechanism is preferred because it allows the observed abrupt uplift when an object impinges on a forearc and causes locking of a shallow segment of the interplate thrust zone.

3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments

“…Theoretically, it is also possible to monitor the vertical displacement of the model surface using 2 cameras providing a stereoscopic view of the model surface (Adam et al, 2005;Riller et al, 2010). This new advance in monitoring technology would be very advantageous because the vertical motion of the model surface can be linked to the distribution of stresses along the plate boundary (Shemenda, 1992), compared with numerical modeling results (Hassani et al, 1997;Bonnardot et al, 2008a,b) or compared with natural data such as long-term uplift/subsidence derived from sedimentary record (Matsu'ura et al, 2008(Matsu'ura et al, , 2009Stefer et al, 2009;Hartley and Evenstar, 2010), short-term uplift/subsidence derived from GPS/Coral reefs dating (Taylor et al, 2005;Matsu'ura et al, 2008Matsu'ura et al, , 2009 or gravity anomalies (Shemenda, 1992;Song and Simons, 2003). However, the produced topography is very small (∼ 1-2 mm) and the distribution of passive markers is not sufficiently large to permit reliable stereoscopic imaging and therefore vertical motions.…”

Outer-rise normal fault development and influence on near-trench décollement propagation along the Japan Trench, off Tohoku

“…When large bathymetric features, such as seamounts, fracture zones, ridges, and oceanic plateaus, are subducted at convergent margins, they strongly deform the landward trench slopes (e.g., McCann and Sykes 1984;Lallemand and Le Pichon 1987;Dominguez et al 1998;Taylor et al 2005). Smaller features, such as subducting horst and graben structures, were once considered to play a role in sediment subduction and upper plate abrasion by horst blocks (Hilde 1983), but better imaging of the subducting plate suggested the subduction plane was well above the top of such features (von Huene and Culotta 1989).…”

The complex 3-D transition from continental crust to backarc magmatism and exhumed mantle in the Central Tyrrhenian basin

“…The two main tectonic erosion processes in a subduction zone are frontal erosion of the overriding plate, and basal erosion, whereby structures on the subducting plate or high pressure fluids released during subduction erode the forearc crust from beneath (Clift & Vannucchi 2004;Stern 2011). Rapid rotation and uplift followed by subsidence of the forearc are attributed to subduction of topographic edifices at a number of subduction systems-for example New Hebrides and Solomon (Taylor et al 2005), Banda Arc (Fleury et al 2009), Costa Rica (Sak et al 2009), Peru (Clift & Pecher 2003) and Cascadia (Trehu et al 2012). These deformation processes may be transient but are recorded in uplifted marine terraces and as differential offsets of forearc blocks on faults at high angles to the trench (Fisher et al 1998).…”

“…Once the seamount passes beneath the plate boundary interface, the forearc subsides and undergoes gravitational collapse (Ballance et al 1989;Wright et al 2000;Laursen et al 2002;Taylor et al 2005), with forearc erosion occurring until the pre-seamount subduction forearc taper is re-established (Lallemand et al 1992). Evidence of seamount subduction may be recorded by the rotation of sediment layers in the forearc (Clift et al 1998), as irregularities or indentations in the trench in the wake of seamount subduction (Trehu et al 2012), or as an overall offset in the plate boundary (Lallemand et al 1992;Wright et al 2000;Ruellan et al 2003).…”