Mantle upwelling after Gondwana subduction death explains anomalous topography and subsidence histories of eastern New Zealand and West Antarctica

Abstract

West Antarctica and adjacent seafl oor have topographic elevations 0.5-1.2 km greater than expected from models of lithospheric age and crustal structure. Ocean crust near New Zealand has no equivalent depth anomaly, but tectonic subsidence histories from Campbell Plateau petroleum wells show anomalously high subsidence rates during the Paleogene, and total subsidence 0.5-0.9 km greater than expected from rift basin models. Geophysical and geochemical anomalies suggest that upward mantle fl ow supports the anomalous topography beneath Antarctica, and the Campbell Plateau subsidence history indicates that topographic support mechanisms were long lived (>80 Ma) and recoverable over a period of ~30 m.y. as plate motions moved New Zealand from Antarctica. We construct models of Late Cretaceous and Cenozoic mantle fl ow with a slab graveyard and upwelling above that is initially rooted at 1000-1500 km depth. Our models match topography and subsidence history anomalies, and are consistent with mantle seismic wave speed anomalies and the geoid. We suggest that when thermally driven slab downwelling ceased ca. 100 Ma, low-density material that was fertilized within a broad zone in the lower mantle during the previous ~400 m.y. of Gondwana subduction was released and able to rise. Mantle upwelling from depths of 700-1500 km, lasting for periods of ~100-200 m.y., with enriched chemistry related to the prior subduction history may be a general process that follows subduction death, and has not previously been recognized.

A global horizontal shear velocity model of the upper mantle from multimode Love wave measurements

“…The low wave-speed feature spatially associated with the South Pacific Superswell extends through the upper-mantle transition zone but is more restricted in area as suggested by Niu et al (2002), rather than a feature of broad lateral extent as postulated at shallower depths (McNutt & Judge 1990). There is a broad low wave-speed feature within the transition zone which closely coincides with the geoid low between New Zealand and Antarctica (Sutherland et al 2010). The other notable transition zone feature is the large low wave-speed region south of India coinciding with the Indian Ocean geoid low, the most prominent negative geoid feature on Earth.…”

Seamounts off the West Antarctic margin: A case for non-hotspot driven intraplate volcanism

“…This magmatism has been related to large-scale mantle upwelling in conjunction with extensioninduced rifting (Finn et al, 2005). Others assume an active mantle plume in the area of the Bellingshausen-Amundsen Sea or beneath East Gondwana (Hole and LeMasurier, 1994;Weaver et al, 1994;Rocholl et al, 1995;Hart et al, 1995Hart et al, , 1997Panter et al, 2000;Hoernle et al, 2010;Sutherland et al, 2010), which may have caused the final break-up of Zealandia from Antarctica (e.g., Weaver et al, 1994;Storey et al, 1999;Hoernle et al, 2010). As the region underwent further plate reorganization, a second phase of volcanism occurred (Rocchi et al, 2002a,b;Nardini et al, 2009 andreferences therein, LeMasurier et al, 1990).…”

Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences

“…Extension north of the Ross Sea may have been partly accommodated by counterclockwise rotations of the Central Basin and Iselin Bank sector [Cande and Stock, 2004a]. During the same time interval (late Mesozoic), termination of subduction underneath Gondwanaland initiated a broad upwelling flow of mantle material that resulted in a region of anomalous shallow bathymetry adjacent to the Ross Sea [Sutherland et al, 2010]. [6] Additional middle Cenozoic opening and subsidence was focused in the western Ross Sea (Northern Basin and Victoria Land Basin [Cooper and Davey, 1985;Davey and Brancolini, 1995]) (Figure 1).…”