Figure 3. SEM photomicrographs show sediments from three different diagenetic zones. A. Sample 164-995A-2H-3, 69-71 cm (6 mbsf), illustrates typical hemipelagic sediment in the upper 20 mbsf lacking obvious authigenic crystals. B. Sample 164-995A-6H-6, 83-85 cm (48 mbsf), shows microcrystalline euhedral dolomite rhombs, ~2 µm in size, typical of the sediments recovered between 20 and 80 mbsf. The euhedral shape of the crystals implies an authigenic origin. C. Sample 164-997A-26X-2, 51-52 cm (205 mbsf), from the top of the gas hydrate zone, exhibits clusters of euhedral siderite rhombs, ~2 µm in size. D. Sample 164-997B-33X-2, 110-111cm, 638 mbsf; exhibits euhedral siderite rhombs.