Flow field stratigraphy surrounding Sekmet Mons Volcano, Kawelu Planitia, Venus

[1] Detailed mapping has revealed several stratigraphic components among lobate plains in the vicinity of Sekmet Mons volcano (44.5 N. lat., 240.5 long.), located on the northern lowland plains of Kawelu Planitia on Venus. Volcanic effusion events produced discrete lobate plains throughout the area. Superposition of flow margins between adjacent lobate plains components indicate that the effusive activity generally progressed from southwest to northeast across the Sekmet Mons area, leading to a cumulative total of 1.5 million km covered by adjacent lobate plains components. Source areas for the effusion responsible for the lobate plains components occur primarily along fracture zones or from concentrations of low volcanic domes (‘‘shield fields’’) instead of from single constructs. Magellan radar backscatter values from a mixture of both radar bright and radar dark flow components within the flow fields are well below values typical of clinkery a0a lava flows on Earth, but they are consistent with values from terrestrial pahoehoe flows. Detailed mapping of Strenia Fluctus (centered on 41.5 N. lat., 251.0 long.), one of the latest lobate plains units in the area, does not show a systematic trend among effusive centers that contributed to the generation of this flow field. Instead, the Strenia Fluctus flow field is a complex mixture of flows that emanated from a shield field along Mist Chasma and that flowed down a very gentle (>0.1 ) regional slope to the east. A 4-km-diameter cone north of Strenia Fluctus was the source of a flow complex traceable for more than 200 km over a slope of only 0.03 . Individual flows within Strenia Fluctus are composed of intermixed lobes, similar to relationships observed on the distal portion of the 75-km-long Carrizozo basalt flow in New Mexico, which also displays abundant inflation features and a predominant pahoehoe surface texture. If the Venusian lobate plains consist of pahoehoe flows comparable to the Carrizozo flow, they were most likely emplaced at modest effusion rates ( 50 to 500 m/s), and even with inflation the flows are likely 15 m in thickness. Under these conditions all of the lobate plains surrounding Sekmet Mons could have been emplaced in 14,000 to 1400 Earth years, assuming continuous effusion with only one source vent active at a time. At similar rates all of the lowland plains in the northern hemisphere of Venus could have been resurfaced by 15-m-thick flows through continuous single-vent effusion in 1.4 million to 140 thousand Earth years.