Variations of the effective elastic thickness reveal tectonic fragmentation of the Antarctic lithosphere

Abstract

To this day, little is known about thermal and rheological properties of the Antarctic lithosphere. We derive the effective elastic thickness Te as a proxy for these parameters by using ice thickness, bedrock topography and a combination of new satellite and high resolution terrestrial gravity data. Cross-spectral analysis based on the fan wavelet technique was employed to calculate Te variations by means of admittance and coherence techniques. Our results confirm a clear tectonic division of Antarctica with predominantly high values in East Antarctica (EANT) (Te~60–80km) and low values in West Antarctica (WANT) (Te~5–20km). For the Transantarctic Mountains separating these provinces, we found Te to be around 10km along the whole chain which is comparable to WANT. Apart from this general division, we found fragmentation of the lithosphere within these provinces. Especially EANT doesn't represent a single lithospheric block but shows strong variations of Te. The highest values are found around the Aurora Subglacial Basin (Te~90km) and in Dronning Maud Land (Te~80km). The minimum value of Te within EANT (~15km) is found in the Lambert Graben. Such a low value can be associated with active rifting in the Permian-Triassic, strong localized erosion or possibly the effect of a Cenozoic mantle plume. According to the coherence calculations, the weak zone extends to the Gamburtsev Subglacial Mountains (GSM), showing a distinct decrease of Te to 25–30km. Thus, this weak channel divides the previously mentioned strong blocks. However, the admittance analysis gives relatively high values (Te~70km) for the GSM. Based on the analysis of the wavelength-dependent admittance and coherence results and misfits for several principal locations, we give some preference to the coherence based values.