Figure F22. A. Close-up photograph of chalk (interval 202-1238A-42X-1, 0-34 cm). B. Diffractogram from XRD measurement of a chalk sample (Sample 202-1238B-42X-1, 23-24 cm). The major peaks correspond to calcite, biogenic opal, and quartz.

Figure F22. A. Close-up photograph of chalk (interval 202-1238A-42X-1, 0-34 cm). B. Diffractogram from XRD measurement of a chalk sample (Sample 202-1238B-42X-1, 23-24 cm). The major peaks correspond to calcite, biogenic opal, and quartz.