| Text Description: |
This sample was collected from a fine-grained, beige-pink, 2-cm thick tephra layer, about 45 cm from the top of a 3 m coal unit that has several interbedded shale partings and shaly coal layers. All layers, including the tephra layer, are affected by differential compaction by the coal. NIN4 contains about 20-25% of mostly altered pumice fragments, and about 15-20% plagioclase that may be twinned and zoned and is mostly angular or appear fragmented. Some larger grains are subrounded. About four to 5% K-spar and trace volcanic rock fragments, angular quartz, zircon, hornblende, biotite, opaques, chert, brown organic material, and chlorite. |