LAVA FLOW EMPLACEMENT PROCESSES ON MARS: INSIGHTS FROM MAPPING MARTIAN LAVA FLOW FIELDS

High-resolution imaging and topographic datasets now allow the styles, distribution, and timing of volcanic processes that occur within a single lava flow field on Mars to be determined. Geologic mapping of flow fields associated with Tyrrhenus Mons, Alba Mons, and Arsia Mons reveals numerous individual lava flows and their surface morphologies and textures, as well as characterizes distributary pathways in the form of lava tubes and channels. Tyrrhenus Mons exhibits a lava flow field (Hesperian in age) that extends for 1000+ km to the southwest. It consists of volcanic channels and a series of lava flow lobes with typical lengths of >50 km. Discontinuous segments of a prominent sinuous rille from the summit caldera are both buried by and source flow lobes within the flow field. The western flanks of Alba Mons (Early Amazonian in age) are characterized by interspersed tabular lava flows and lava tubes systems, with many individual feature lengths of 100+ km. The discontinuous chains of collapse depressions that define lava tubes often occur on prominent sinuous ridges with lateral flow texture. Tabular lava flows commonly embay lava tube systems but local flow field stratigraphy is complex. Mapping of Daedalia Planum, south of Arsia Mons, reveals three main sequences of geologically recent volcanism, including broad sheet-like flow units (Middle Amazonian) covered by intermingled smooth and rough elongate flow types (Middle to Late Amazonian). The rough flows commonly have medial channel/levee systems and many have exposed lengths of 100+ km. Smooth flows extend from distributary systems that may include channels, lava tubes, and sinuous ridges and plateaus; associated flows show pahoehoe-like forms and evidence for inflation. These three Martian flow fields represent different geologic settings, eruptive centers, and ages of volcanism. Mapping shows that each flow field contains different scales and diverse types of volcanic features emplaced coevally, suggesting time variable eruption conditions during flow field emplacement. Further analyses of volcanic morphology and local superposition and embayment relationships within flow fields should provide additional constraints on Martian volcanism.