Mapping of the relationship among country rock, non-explosive intrusive rocks and deposits of explosive eruptions of the Mawson Formation in the Allan Hills as an indication of phreatomagmatic eruption processes

Phreatomagmatic eruptions are common and dangerous worldwide. How large explosive event complexes evolve during eruptions, the processes that drive the evolution and what is in the rock record was studied in the Mawson Formation in Allan Hills, Victoria Land. The Mawson Formation is a unit of fragmented volcanic rock comprising debris from the Beacon Supergroup mixed with fragments from Ferrar Group magmas. It represents part of a regional province dominated by debris from eruptions with extensive exposure. Standard geological mapping techniques, observations, photographs and sketches were used to map the relationship among country rock, non-explosive intrusive rocks and deposits of explosive eruptions preserved in both volcanic craters and areas surrounding the craters. One aspect of the study area revealed an extensive zone of broken country rock and associated chaotic deposits that are inferred to represent extensive landsliding toward the main outcrop area of the Mawson Formation on Allan Hills. This area was investigated in detail.