Geologic maps of the French Butte and Greenhorn Buttes quadrangles, Washington

Afi 121°30' 121names have been used, sometimes in modified form, by most later workers (Hammond, 198O, Swanson and Clayton, 1983; Vance and others, 1987) in areas near Mount Rainier and haVe been tentatively extended throughout the southern Washington Cascades during reconnaissance work with little intervening detailed mapping (Wise, 1970;Hammond, 1980).For example, Hammond (1980) assigned most of the bedrock in the French Butte and Greenhorn Buttes quadrangles to the Ohanapecosh and Stevens Ridge Formations on the basis of reconnaissance mapping.One of the objects of my work is to place the stratigraphy of Fiske and others (1963) into a well-controlled regional context that will result from pooling the work by Evarts and Ashley with that of the current study to provide a geologic transect across the southern Washington Cascades.It is too early in the study to assess the regional stratigraphic relations, although it is clear that the rocks in the French Butte and Greenhorn Buttes quadrangles are considerably younger that those assigned to the Ohanapecosh Formation near Mount Rainier (Vance and others, 1987).