 The top member consists of a fine-grained, typically reddish lava flow and another lithic tuff unit.It can be found exposed in a limited region, encompassing the flank of the Hoyt Station basalt, colored light yellow in the diagram at right; it also peeks out closer to the volcano twice.The next layer, the South Oromocto Andesite formation, is composed of at least three flow units, with basalt flows being the most extensive.