Rift-Related Sedimentary Basin and Deeper-Seated Mafic Intrusions Modeled Beneath Thwaites Glacier, West Antarctica: Influence on Glacier Dynamics

Abstract

Thwaites Glacier in West Antarctica has been identified as a route to destabilization of the whole West Antarctic Ice Sheet, potentially leading to several meters of sea-level rise. However, future evolution of Thwaites Glacier remains uncertain due to a lack of detailed knowledge about its basal boundary that will affect how its retreat proceeds. Here we aim to improve understanding of the basal boundary in the lower part of Thwaites Glacier by modeling the crustal structures that are related to the bed-type distribution and therefore influence the basal slip. We combine long-offset seismic, and gravity- and magnetic-anomaly data to model the crustal structures along two $\sim$120 km lines roughly parallel to ice flow. We find a sedimentary basin $\sim$40 km in length in the along-flow direction, with a maximum thickness of 1.7 $\pm$ 0.2 km, and two mafic intrusions at 5–10 km depth that vary in maximum thickness between 3.8 and 8.6 km. The sedimentary basin and major mafic intrusions we modeled are likely related to the multi-stage tectonic evolution of the West Antarctic Rift System. Thwaites Glacier flows across a tectonic boundary within our study site, indicating it flows across tectonically formed structures. The varying geology and resulting variations in bed types demonstrate the influence of tectonics on Thwaites Glacier dynamics.