Elongate summit calderas as Neogene paleostress indicators in Antarctica

The orientations and ages of elongate summit calderas on major polygenetic volcanoes were compiled to
document Miocene to Pleistocene Sh (minimum horizontal stress) directions on the western and northern flanks of the
West Antarctic rift system. Miocene to Pleistocene summit calderas along the western Ross Sea show relatively
consistent ENE long axis trends, which are at a high angle to the Transantarctic Mountain Front and parallel to the
N77ºE Sh direction at Cape Roberts. The elongation directions of many Miocene to Pleistocene summit calderas in
Marie Byrd Land parallel the alignment of polygenetic volcanoes in which they occur, except several Pleistocene
calderas with consistent NNE to NE trends. The overall pattern of elongate calderas in Marie Byrd Land is probably due
to a combination of structurally controlled orientations and regional stress fields in which Sh is oriented NNE to NE at a
moderate to high angle to the trace of the West Antarctic rift system.