Plate P2. Photomicrographs illustrating mineral grains present within the sands and sandstones of Woodlark rift. 2. Detrital biotite grain with authigenic calcite growths along cleavage planes surrounded by detrital grains of feldspar and colorless vitric, brown vitric, and felsitic volcanic lithic fragments. This was interpreted by previous workers as a calc-schist fragment (Sample 180-1116A-11R-1, 16-19 cm [81.96 mbsf]) (plane-polarized light).