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Sample ID is the core number_cruise-and-sample-number_length (cm) from Table 1 in Nayudu (1964), which contains the list of the cores containing volcanic ash, their position, depth and length. Depth of 200 fathoms. A middle basic ash is present from 28-30 cm, and is brownish-black with a clearly defined base and poorly marked upper limit. Predominantly grayish-brown glass shards that are irregular and splintery with inclusions of gas bubbles and minerals, the most common being plagioclase, feldspar, and pyroxene. Shards show little to no alteration. Mechanical analysis (24-25.5 cm) has the following size fractions: 47% fine sand and 45% silt. The median diameter is 57 microns and the sorting coefficient is 2.40. Glass content varies from 70-80% and the mineral and crystal fragments make up the rest. Hypersthene is the dominant mineral and some of the other important mineral constituents are basaltic hornblende, augite, magnetite and plagioclase (andesine and labradorite). The average refractive index of the glass is 1.562 +/- 0.002. Inferred to be 12,000-15,000 years old. |