| Text Description: |
NIN2 is from a 100 to 150 cm thick coal unit. The tephra layer is about 8 cm thick, coarse-grained, crystal-rich, dirty-brown orange in color and weathers light beige. The uppermost part of the coal unit has some thin shale and siltstone partings and a sharp contact with overlying yellow, cross-bedded sandstone. The coal unit as a whole contains from the top: 20 cm of blocky, carbonaceous siltstone with iron stain, 11 cm of coal, 26 cm of blocky, gray siltstone, 15 cm of coal, 21 cm of clayey siltstone with disseminated pumice fragments, 8 cm of coal, 8 cm crystal rich tephra (NIN2), and 34 cm of coal. The coal grades downward into blocky siltstone with plant fragments. NIN2 has 40-50% feldspar, 7-10% hornblende, and 5% opaques. The feldspar is twinned and zoned with rare glass fringes. Many grains are altered to sericite, especially along cleavages. The hornblende shows faint pleochroism in blue-green to yellow-green. The smallest hornblende grains are splintery while the larger ones are stubby, some with rounded edges. Trace amounts of quartz, Kspar, altered glass, volcanic rock fragments, biotite, epidote, sphene, pyrite, and biotite. |