Plate 4. Thin-section photomicrographs of structures in clay-rich matrix cataclastic breccias. 1. Sample 161-976B-80R-2, 1-8 cm. Breccia formed of splintered quartzite porphyroclasts (Q) in clayey dolomite-rich matrix (DM). Note widespread displacive-dolomite filling internal cracks (arrows) in porphyroclasts. Plane light. Scale bar = 1 mm.