Crustal thickness in Antarctica from CHAMP gravimetry

Abstract

CHAMP, flying at an altitude of about 400 km, is the first of a new generation of satellites dedicated to Earth gravity field observation. The high-quality data have generated new gravity field models: EIGEN-1S in 2001, and EIGEN-2S more recently. The gravitational potential is decomposed into spherical harmonic coefficients and in this study we use the free air gravity anomalies reconstituted up to degree 60, at zero altitude. The anomalies for the Antarctic continent range from 357 to 65 mGal. We have modeled the gravity effect from the ice, the ocean and the bedrock, using a 666 km cut-off filter to simulate the resolution obtained by CHAMP. Computing the differences between this terrain effect and the CHAMP map provides a map of the Bouguer anomalies. Because of the dominant influence of the crust, we first used a crustal thickness model from seismology. This gives a map of the mantle Bouguer anomalies, the range of which is still large (between 3255 and 216 mGal) indicating imperfections in the crust model. By appealing to isostasy we then imposed the condition that this mantle Bouguer anomaly should vanish and therefore solve for a new resulting crustal thickness. This gravity-based crust model gives thicknesses from 8.5 to 42.6 km in the zone of interest. There is a good general agreement with seismological models, but our models shows more detail, particularly in the western part of the continent. These details are in agreement with geological studies. ß

Combined Gravimetric–Seismic Crustal Model for Antarctica

“…In existing studies investigating the Moho interface under Antarctica, isostatic 146 models were applied based on assuming a local compensation mechanism and adopting a 147 planar approximation. Llubes et al (2003), for instance, estimated the crustal thickness in 148 Antarctica based on applying a simple linear relation between the crustal thickness and the 149 planar Bouguer gravity reduction. Block et al (2009) derived the crustal thickness from 150 gravity data based on applying Parker-Oldenburg's method, and O'Donnell and Nyblade 151 (2014) derived the Antarctic crustal thickness from the gravity and topographic models 152 according to Airy's theory.…”

Apatite single‐grain (U‐Th)/He data from Heimefrontfjella, East Antarctica: Indications for differential exhumation related to glacial loading?

“…Seismic studies suggest that the Heimefrontfjella is the boundary between unaffected thick (∼50 km) and thinned (∼35 km) continental crust [from Jacobs and Lisker , 1999]. This assumption is confirmed by a gravity based crust model which indicates crustal thinning from >40 km in the hinterland of the Heimefrontfjella to ∼20 km along the eastern continental margin [ Llubes et al , 2003, Figure 6]. Dolerite dyke distributions east of the Muren gabbro indicate 14% of crustal stretching during the Middle Jurassic [from Vuori and Luttinen , 2003].…”

Post Middle Miocene Tectonomagmatic and Stratigraphic Evolution of the Victoria Land Basin, West Antarctica

“…Gravity modeling, seismic refraction surveys, and body and surface wave studies show that the crust thickness varies from 10–21 km in the basins up to 24 km beneath the basement highs (Bannister et al, 2003; Behrendt, 1999; Danesi & Morelli, 2000; Davey, 1981; Davey & Brancolini, 1995; Guterch et al, 1985; Llubes et al, 2003; Ritzwoller et al, 2001; Trey et al, 1999). The crust is thicker on the flanks of the rift, ranging from 25–30 km in Marie Byrd Land on the east and from 35–40 km beneath the Transantarctic Mountains on the west (An et al, 2015; Bannister et al, 2000; Busetti et al, 1999; Chaput et al, 2014; Finotello et al, 2011; Graw et al, 2016; Hansen et al, 2009, 2016; Lawrence et al, 2006; Llubes et al, 2003; O'Donnell & Nyblade, 2014; Pyle et al, 2010; Studinger et al, 2006; Winberry & Anandakrishnan, 2004). Comparison of the modern crust thickness in the Ross Sea basins with estimated prerift thickness, as well as plate reconstructions, suggests that the region has widened by 25% to 50% (250–500 km) since the Late Cretaceous Period (Behrendt, 1999; Davey & Brancolini, 1995; Decesari, Wilson, et al, 2007; D. S. Wilson & Luyendyk, 2009).…”