3-D density structure of the Ross Sea basins, West Antarctica from constrained gravity inversion and their tectonic implications. Issue 2 (23rd August 2018)

• Record Type: Journal Article
• Authors: Ji, Fei; Li, Fei; Gao, Jin-Yao; Zhang, Qiao; Hao, Wei-Feng
• Is Part Of: Geophysical journal international. Volume 215:Issue 2(2018:Nov.)
• Page Start: 1241
• Page End: 1256
• Publication Date: 2018-08-23
• Subjects: Joint inversion -- Crustal structure -- Dynamics:gravity and tectocnis -- Rheology: crust and lithosphere -- Antarctica; Geophysics -- Periodicals; 550
• DOI: 10.1093/gji/ggy343
• Languages: English
• ISSNs: 0956-540X

Abstract

SUMMARY: Crustal structure provides critical information for understanding the rifting and extensional history (i.e. the regional tectonic evolution) of the Ross Sea basins. Although this area has been investigated using large numbers of 2-D seismic reflection profiles collected during different cruises over the past several decades, its crustal-scale geological structure is still poorly known. This paper reports new information on the 3-D density structure of the Ross Sea obtained using gravity inversion performed with the GRAV3D algorithm and other forms of geophysical data, including free-air gravity anomaly, bathymetry and sediment thickness measurements. Combined with the published wide-angle refraction seismic results from the Antarctic Crustal Profile project, Moho depths and upper and lower crustal thicknesses are inferred. Our results show that the inverted Moho depths and the boundaries of the upper and lower crust are largely consistent with the results of seismic studies. Under the sedimentary basins of the Ross Sea, the Moho generally occurs at depths of 13–18 km, corresponding to crustal thicknesses of 7–12 km; on the other hand, under basement highs, the Moho occurs at much greater depths of up to approximately 24–30 km in the northern part of the Coulman High, the Central High and Iselin Bank. Further, the stretching factors of the crust as a whole and the upper and lower crust ( β w, β u and β l, respectively) are investigated by assuming the corresponding initial thickness. Depth-dependent stretching, in which crustal thinning increases with depth (i.e. the values of β l exceeds those of β w and β u ), is observed under the Ross Sea basins. These discrepancies between the values of β for different parts of the crust suggest that the crust in the Ross Sea basins has experienced nonuniform crustal thinning. Together with published Curie point depth data, our results indicate that the Curie point lies beneath the Moho under the Victoria Land Basin and Central High, suggesting that the uppermost mantle is magnetized. We speculate that this magnetism is the result of serpentinization.