Volcanic Rocks from the Ross Island, Marguerite Bay, andMt.Weaver Areas, Antarctica

During the last several years volcanic rocks from the Ross Island, Marguerite Bay, and Mt. Weaver areas have been studied. Field data and some laboratory work indicate that the portions of the Ross Island area already studied consist of an older olivine basalt-trachyte sequence and a younger olivine basalt-basalt sequence. A K/Ar date determined from anorthoclase indicates an age of 0.68 (±0.14) m. y. for the Antarctic kenyte of the Cape Royds area. Chemical, isotopic, and petrographic analyses of the rocks from the Ross Island area continue. Future investigations will be concerned with the geology of the high peaks and the character of the volcanic activity and products of Mt. Erebus. The Terra Firma volcanic rocks occur in the Marguerite Bay area and in other parts of the Antarctic Peninsula. They constitute a unit that may be a few thousand or more feet thick (NICHOLS, 1955) and consist, primarily, of andesite, dacite and rhyolite. Tuffs, breccias, and agglomerates are also common. The rocks may be Mesozoic or Cenozoic in age. In the Mt. Weaver area volcanic rocks occur on the flanks of Mt. Saltonstall and constitute Mt. Early, which is apparently a partially dissected cone (DOUMANI and MINSHEW, 1965). Mt. Saltonstall consists of olivine basalt, basalt, tuff, and volcanic breccia