The oldest basalt found in the Meserve drainage is the 3.4m.y. basalt in the Alpine II moraine. Available age determination now suggest that the major axial valley-cutting glaciation occurred over 4.2m.y. ago. Alpine glaciation probably began more recently than 3.4-3.5m.y. ago, although the water-eroded channel west of the Meserve Glacier may be related to subglacial eruption of the 3.4m.y. basalt. Volcanism occurred at the western margin of the Merserve accumulation basin approximately 2.5. m.y. ago, and both older and possibly younger volcanics were later reworked during the Alpine II Glaciations, being incorporated in moraines on both sides of the glacier.