How Gondwana break-up influences East Antarctic ice flow and regional ice load tectonics – insights from the Knox Coast, East Antarctica

Large-scale tectonic fault structures shape many flow paths of modern ice sheets at high-latitude ice dominated continental margins. However, the influence of these structures on glacial pathways on the East Antarctic continental margin, as well as the impact of glacially induced tectonic movements, are under-investigated. Here we present the first results of tectonic analysis of fault structures in seismic reflection data from Vincennes Bay off Knox Coast, East Antarctica. The Vincennes Bay continental shelf exhibits four distinct phases of faulting since Gondwana break-up between Australia and Antarctica. The first and second phases are expressed as positive flower structures oriented roughly northwest to southeast. These align with the offshore Vincennes Fracture Zone and magnetics data indicate a dextral strike-slip fault zone with a local transpressive character. There are at least four distinct similarly oriented flower structures occurring at different times, three prior to Cretaceous continental break-up and at least one after Australia fully separated from East Antarctica. The orientation of flower structures on the continental shelf suggests a continuation through the Vanderford Glacial Trough, indicating that this fault zone provided an easily erodible pathway for pre-glacial fluvial activity followed by glacial ice flow. Faults produced by later tectonic phases are oriented roughly east to west showing signs of flexural stresses, indicating a different stress regime than previous tectonic events. These later phases were induced by glacial loading and unloading of an advancing and retreating East Antarctic Ice Sheet (EAIS) during its early establishment in the region (about 27-14 Ma) and during grounding line oscillations under full glacial conditions (later than 14 Ma). The relationship between fault zones and glacial troughs illustrates how pre-glacial tectonic processes influence past and modern ice flow configurations. Ice loading and unloading on the continental shelf due to the establishment of the EAIS and its grounding line oscillations aid the reconstructions  of EAIS ice streams during the Cenozoic.