Figure F7. Close-up photograph of brecciated subunits from Unit 2 (pillow lava) (Section 336-U1382A-5R-1). A. Hyaloclastite with poorly sorted angular clasts of highly altered glass. Larger clasts develop red to light brown concentric alteration halos representing more smectitic or iddingsitic mineral replacement. The reddish-brown microcrystalline matrix is enriched in Fe oxyhydroxides and clay filling (Section 5R-1, 114–119 cm [Piece 21]). B. Close-up showing reddish-brown matrix and various degrees of glass alteration (binocular microscope ×0.6; wet surface). C. Close-up showing freshest dark gray cryptocrystalline basalt within hyaloclastite, with branching anastomosing veins composed of Fe-rich smectite and white zeolite (binocular microscope ×0.8; wet surface).
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