Variations of the effective elastic thickness over the Ross Sea and Transantarctic Mountains and implications for their structure and tectonics

Abstract

The effective elastic thickness (Te) is a proxy for lithospheric strength, and it depends primarily on the thermal gradient and composition of the lithosphere. Accordingly, spatial variations in Te reflect changes in lithospheric properties and can be used to better understand the structure and tectonics of particular regions. In this paper, we investigate the Ross Sea and Transantarctic Mountains in terms of Te using gravity and topographic data and the fan wavelet transform technique. The results reveal that relatively high Te values dominate in the extensional basins of the Ross Sea and the hinterland of Transantarctic Mountains, whereas very low Te values occur along the Transantarctic Mountain Front and in the deep ocean basin, with the lowest Te values are found the vicinity of Ross Island and onshore in northern Victoria Land. In addition, the spatial variations in Te correlate well with lithospheric structure at the regional scale. By combining these findings with published seismic and heat flow data, we conclude that the presence of a zone of anomalously lowTe values parallel to the coast indicates that the lithosphere beneath the Transantarctic Mountain Front is extremely weak due to Cenozoic volcanism and extension. The Te values increase from the Transantarctic Mountain Front (7km) toward the center of the continent (~80km), which indicates that the continental lithosphere underlying East Antarctica belongs to the classic Gondwanan craton. The increase in Te indicates that the Transantarctic Mountain Front marks the continent-continent boundary between East Antarctica and West Antarctica. The Te values in the other extensional basins of the Ross Sea exhibit little variation and average approximately 35km. The relatively high Te values are interpreted to indicate that the lithosphere cooled and became mechanically stronger between late Cretaceous extension and Eocene-Neogene deposition.