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Fig. 6. Photomosaic and projected vertical fault map for the Crucifix site. (A) Exposure of west-dipping normal fault that offsets thinly bedded, highly porous and nonwelded, pumice-rich hybrid to streaky fallout tephra deposits (Wilson and Hildreth, 1998) interbedded with minor thin ignimbrite sequences pf the Crucifix site. Conjugate normal faults and numerous centimeter-scale displacement faults occur within the footwall damage zone. Ferrill et al. (2000) suggested these faults formed by sequential rather than simultaneous slip. (B) We estimated a minimum offset of 8 m from measurements along the Crucifix fault. The hanging wall damage zone extends about 5 m to the west, whereas the footwall damage zone extends about 10 m to the east. Fault core is heterogeneous and is filled with calcite and/or coated with clay, or consists of a comminuted gouge material with abundant pumice clasts (Fig. 8). Vertical fractures are closely spaced in the hanging wall and typically get deflected as they intersect less-welded and/or coarser pumice-rich layers. Subsidiary fractures are open or have millimeter to 1-cm-thick calcite and silica coatings. Numbers indicate sample locations for X-ray diffraction and thin-section analyses.
