Figure 15. Geologic map of the northeastern caldera margin (Cortez and Cortez Canyon 7-' quadrangles). East-dipping intracaldera Caetano Tuff is at least 3400 m thick in this area. Intracaldera breccia varies from scattered lenses of mesobreccia containing clasts up to 2 m in diameter in the western, stratigraphically and structurally lowest part of the caldera to abundant megabreccia composed of individual blocks up to 50 m in diameter and composite areas of blocks up to 1 km across in the eastern, highest part of the caldera. The caldera margin in the western part of the figure is a fault that constitutes the structural margin. The eastern part of the caldera margin is eroded, topographic wall from which the exposed megabreccia slumped into the caldera. Locations A, B, and C are discussed in the text.