Plate 3. Thin-section photomicrographs of dolomite-cemented to clay-rich matrix cataclastic breccias from Holes 976B and 976E. 1. Sample 161-976B-75R-1, 52-56 cm. Broken quartzite porphyroclast (Q) surrounded by vague cataclastic foliation (S). All of the finer matrix is replacive dolomite "cement." Note open crack in the clast filled by matrix. Plane light. Scale bar = 1 mm. 2. Sample 161-976B-75R-1, 52-56 cm. Close-up of matrix in (1) showing planar (euhedral) to nonplanar dolomite (D). Dolomite rhombus growth over "cloudy" nonplanar dolomite. Note replacement of quartz grains (Q) by dolomite crystals (arrows). Crossed polars. Scale bar = 100 µm. 3. Sample 161-976B-78R-1, 106-110 cm. Saddle dolomite cement (SD) and detrital dolomite filling a void in dolomite breccia. Note a fragment of saddle dolomite (FD) within the dolomite matrix filling the void and several zones of saddle dolomite growth. Crossed polars. Scale bar = 500 µm. 4. Sample 161-976B-80R-1, 103-107 cm. Dolomite-matrix breccia. Note dolospar cement at the contact of quartzite clast (Q) and dolomitic matrix (DM). Note large euhedral crystal coarsening inward at the matrix/clast boundary (arrow). Plane light. Scale bar = 500 µm. 5. Sample 161-976B-86R-2, 80-83 cm. Clay-matrix cataclastic breccias. Note cataclastic lineation and cataclastic flow (S) marked by alienation of smaller and elongated clasts. Plane light. Scale bar = 1 mm. 6. Sample 161-976E-21R-2, 75-80 cm. Clay-matrix, cataclastic breccias. Note two generations of breccias (B1 and B2), corresponding to light and dark color in matrix, and broken quartzite porphyroclast (Q). Plane light. Scale bar = 1 mm. Click on image for enlargement.

Plate 3. Thin-section photomicrographs of dolomite-cemented to clay-rich matrix cataclastic breccias from Holes 976B and 976E. 4. Sample 161-976B-80R-1, 103-107 cm. Dolomite-matrix breccia. Note dolospar cement at the contact of quartzite clast (Q) and dolomitic matrix (DM). Note large euhedral crystal coarsening inward at the matrix/clast boundary (arrow). Plane light. Scale bar = 500 µm.