Figure 11. Geologic map of part of the Eocene paleovalley in the Windermere Hills (modified from Mueller, 1993, with ⁴⁰Ar/³⁹Ar dates from Mueller et al., 1999). Imbricated clasts in cobble conglomerate (Tdc) indicate eastward flow (Mueller, 1992). Mueller (1993) and Mueller et al. (1999) interpreted major normal faults repeating the ash-flow tuffs along the west side of this map. I reinterpret these as megabreccia (Tx) composed of blocks of the plagioclase-biotite tuff and tuff of Big Cottonwood Canyon. That they are blocks is confirmed by petrography, chemical analysis, discordant compaction foliations, and by scattered magnetization directions (Palmer and MacDonald, 2002). Therefore, their stratigraphic position and the amount of repetition by faulting are uncertain.