Weakened Lithosphere Beneath Greenland Inferred From Effective Elastic Thickness: A Hot Spot Effect?

Abstract

AbstractThe effective elastic thickness (Te) of the lithosphere provides geophysical information about long‐term flexural strength and can be used to constrain thermorheological properties of the lithosphere. Te is typically calculated from the spectral analysis of gravity and topography data; variations in Te are, however, not well resolved in Greenland due to poor constraints on crustal structure (including crustal thickness) and complications due to ice loading. In addition, geological and geophysical constraints on the tectonic history of Greenland are sparse due to the thick ice cover. Here we use the global gravity model EIGEN‐6C4 together with a new model of the crust‐mantle boundary to obtain a high‐resolution Te map of Greenland. The distribution of Te indicates reduced strength in the lower crust and lithospheric mantle beneath southern and central Greenland, which may be due to the passage of the Iceland hot spot during the last 100 Ma. In contrast, the northern part of Greenland shows a large Te, implying mechanical coupling between crust and uppermost mantle and suggesting the existence of a cold and strong tectonic unit. In a relative sense, the distribution of Te values is consistent with estimates of lithospheric thickness based on seismic velocity models, indicating a dominantly thermal control on lithospheric structure and evolution.