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Text Description: Only present at Site C of Chester Bluff. The Biederman tephra (BT) is up to 2 cm thick at Site C, forms pods up to 10 cm long, is continuous over 8m and has a salt and pepper appearance. It either rests directly on the surface of or is reworked into the upper-most organic unit of this exposure. At the upstream end of the exposure the organic unit is over-thickened and locally draped into an ice wedge cast about 1.7m deep. The ice wedge cast fill includes 1m of reworked organic-rich loess, indicating the ice wedge melted out when organic material was accumulating on the surface and accumulation continued after the cast was filled. BT forms rare pods in the loess that fills the cast. At the downstream end of the exposure, BT can be traced at the same elevation until it is truncated by a modern gully. Generally has highly inflated pumice and is particularly rich in phenocrysts, which are overwhelmingly green amphibole. References:  An extensive middle to late Pleistocene tephrochronologic record from east-central Alaska Tephrochronology of middle to late Pleistocene loess in east-central Alaska |
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