Description:
Remapping of the intramontane depression south of Kearny drained by Hackberry Wash and Indian Camp Wash between the Ripsey Hill and Crozier Peak spurs of the Tortilla Mountains was undertaken to reconcile differences in previous mapping, and to resolve questions raised or left open by the previous mapping (Schmidt, 1971, 1989; Krieger, 1974a, 1974b; Cornwall and Krieger, 1975; Banks and Krieger, 1977; Keith, 1983; Dickinson, 1987). The map area includes parts of the Kearny, Hayden, Winkelman, and Crozier Peak 7-1/2 minute quadrangles (in clockwise order from their common join). The improved mapping leads to revision of previous interpretations (Dickinson, 1991, p. 67-76) of the stratigraphic and structural relationships of tilted mid-Tertiary strata. Further paleocurrent study of clast imbrication (Dickinson, 1991 , fig. 39) and more rigorous clast counts in conglomerates are needed, however, to define more closely the mid-Tertiary pattern of sediment dispersal into and within the map area now that overall structural morphology and internal stratigraphy are better understood. Text that accompanies the map includes brief discussion of mid-Tertiary stratigraphy, an overview of key structural features, and a reappraisal of the distribution and origin of rock-avalanche megabreccias (Krieger, 1977) within the map area.