Charting the southern seas - The evolution of the lunar Mare Australe

Mare Australe has been subjected to at least four major episodes of basalt eruption ranging in age from early Imbrian to Eratosthenian. The basalts were emplaced largely in flood eruptions from at least 197 vents located on post-basin impact crater floors. The youngest basalts occur in an annulus near the outer edge of the basin. The fill thickness apparently reflects a multiring structure for the post-impact morphology of the Australe basin; the thin basaltic fill was not sufficient a load to produce tectonic rilles, but mare ridges are present and exhibit a prominent north-south alignment.