Figure F4. Photomicrographs of Porcupine Basin sediments. A. Smear slide of Core 307-U1317A-1H. Mud mound matrix is composed largely of coccoliths with a framework of coldwater coral. Note angular quartz silt grains and a dolomite rhomb in the lower left. B. Dolomite in a lithified interval in the Miocene near the bottom of Core 307-U1318B-24H. Note the dominance of dolomite rhombs in this field of view. Also present are silt-sized quartz, micritic calcite (coccoliths), and glauconite. Bulk X-ray diffraction analysis of this sample indicates that it actually contains only ~20% dolomite. C. Thin section from a lithified zone in Core 307-U1316C-11H. Groundmass is primarily nannoplankton and clay minerals. Note the abundance of silt-sized detrital quartz and glauconite. D. Close-up of C with dolomite rhombs visible. This sample contains >30% dolomite based on X-ray analysis.
Previous | Close | Next | Top of page