SUPERVOLCANOES IN THE ARABIA TERRA REGION OF MARS AND THEIR RELATIONSHIP TO LAYERED SEDIMENTARY UNITS

Several large (10s km in diameter) and irregularly shaped depressions within Arabia Terra, Mars represent an explosive type of highland volcanic construct. As a group these volcanoes constitute a previously unrecognized martian volcanic province. These low-relief volcanoes, or paterae, display a range of geomorphic features related to structural collapse, effusive volcanism, and explosive eruptions. Extruded lavas contributed to the formation of enigmatic highland ridged plains in Arabia Terra. Outgassed sulfur and erupted fine-grained pyroclastics from these calderas likely fed the formation of currently altered, layered sedimentary rocks and fretted terrain found throughout the equatorial region of Mars. Discovery of a new type of volcanic construct in the Arabia volcanic province fundamentally changes the picture of ancient volcanism and climate evolution on Mars. Other eroded topographic basins in the ancient Martian highlands that have been dismissed as degraded impact craters should be reconsidered as possible volcanic constructs formed in an early phase of widespread, disseminated magmatism on Mars.