FLOW FIELD STRATIGRAPHY IN NORTH MAHUEA THOLUS QUADRANGLE (V-49), VENUS

The northern third of the Mahuea Tholus quadrangle of Venus (V-49; 25-50°S, 150-180°E) hosts Diana-Dali Chasma – a significant ~NE-SW-trending zone of extension. Emanating from this zone are multiple lava flows that appear to be sourced from both coronae and individual fractures. Flow materials have traveled both north and south of this zone, creating an extensive flow field that encompasses an area of 1.2 x 10⁶ km² across the northern and central portions of V-49. As part of an effort to constrain the geologic history of the V-49 quadrangle, we have been unraveling the stratigraphy of the flow field associated with this rift zone. In the surrounding quadrangles, the Diana-Dali Chasma has been divided by major corona-associated flow fields that continue into V-49. These flows are identified as the central points of volcanism within the rift zone and were used to help in determining stratigraphy. Specifically, we have utilized NASA Magellan SAR imagery (~100 m/pxl) and altimetry data (~5 km/pxl) to geologically map individual flow units and their associated features. Following the methodology of Hansen (2000), we first identified tectonic structures, which allowed us to elucidate flow materials. Flow field stratigraphy was subsequently constrained using relative dating principles. There are four coronae present within the Diana-Dali Chasma in the Mahuea Tholus quadrangle: Agraulos, Annapuma, Colijnsplaat, and Mayauel. With these coronae flow fields are also Atahensik, Ceres, Bona, Miralaidji and Flidais coronae flows that originate from outside the quadrangle. Timing of fracture formation appears non-uniform with NE-trending suites of fractures cross-cutting E-W trending fracture suites; this, suggests different parts of the rift zone were active at different times with the youngest episodes of rift-associated volcanism likely having occurred before and during formation of the NE-trending fractures. The total area of the Mahuea Tholus quadrangle is roughly 6.5 million km² and, within that area, the major coronae flow fields (Agraulos, Annapuma, Colijnsplaat and Mayauel) resurface ~25% of the quadrangle. Though they emanate predominantly from the northern part of V-49, coronae and rift-sourced lavas appear to have been the dominant source of volcanic resurfacing in this map area.