Figure F4. Some volcanic fragments in Unit 4 show perlitic groundmass texture. In thin section, arcuate, intersecting perlitic cracks are well-preserved. Perlitic groundmass domains are separated by linear to irregular fractures and arranged in a jigsaw-fit pattern (Sample 193-1189A-2R-1 [Piece 15, 113-115 cm]; width of view = 2.75 mm. Photomicrograph ID# 1189A

Figure F4. Some volcanic fragments in Unit 4 show perlitic groundmass texture. In thin section, arcuate, intersecting perlitic cracks are well-preserved. Perlitic groundmass domains are separated by linear to irregular fractures and arranged in a jigsaw-fit pattern (Sample 193-1189A-2R-1 [Piece 15, 113-115 cm]; width of view = 2.75 mm. Photomicrograph ID# 1189A_13; thin section 33).