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Sample ID:UT250
Station ID:UT250
Sample Type 1:Tephra Fall
Text Description:
Unit 5 at this location contains angular fragments of tephra believed to have been "eroded, transported, and redeposited in a frozen state’" (Weber et al., 1981). This tephra is SCt, here named SCt-CC. In their 1981 paper, Weber et al. stated that this tephra was identified by Westgate as the Dome Ash Bed, but further work showed this identification to be incorrect. The tephra pods show plastic deformation in places, and elsewhere are preserved as thin beds up to 10 cm long that are parallel to bedding. See Westgate et al. (2007) for a discussion of the context of this tephra. A strongly pleochroic hypersthene with fluid and opaque inclusions is abundant as are hornblende and plagioclase. Ilmenite and magnetite are conspicuous and trace amounts of basaltic hornblende, augite, and quartz are present. Many of the minerals do not have attached glass and are slightly rounded, but otherwise look the same as those with attached glass. A white frothy pumice is the dominant phase, and occurs together with a small amount of brown glass that is not observed in SCt in the Fairbanks area.

Changing ideas on the identity and stratigraphic significance of the Sheep Creek tephra beds in Alaska and the Yukon Territory, northwestern North America

StationIDLatitudeLongitudeGeologistDateVisitedAge InfoVolcanoEruptionLocation DescriptionText DescriptionSample IDSample Type 1Sample Type 2Final UnitMaterialCoeffSiO2TiO2Al2O3FeOTMnOMgOCaONa2OK2OP2O5Total-majorsREF majorsMETH majorsFe2O3/Fe203T origFeO/FeOT origVolatiles csvMETH volatilesCsRbBaSrLaCePrNdSmEuGdTbDyHoErTmYbLuYZrNbHfTaPbThUScVCrFeCoNiCuZnGaMoAsNaKRef trace1METH trace1RbBaSrLaCeNdSmEuGdDyErYbLuYZrNbPbThUScTiVCrNiCuZnGaRef trace2METH trace2Light csvHalogen csvother major csvother lile csvother ree csvother hfse csvother hpe csvother tm csvother misc csv
UT25064.3-146.517Unknown, Unknown< 140000 stratigraphy; 4365; The geomorphic and stratigraphic setting of SCt-CC suggest an age older than Old Crow tephra, which is 140 ka, but this conflicts with a U-series age of 80 ka on bones just beneath SCt-CC and the chemical characteristics of its glass shards which resemble the younger group of SCt beds (from Westgate and others 2007).-188050--Canyon Creek exposure. Roadcut along the Richardson Highway, about 85 km southeast of Fairbanks, Alaska. Datum not specified, assumed to be Nad83.UT250Tephra FallCumulateGlass 76.18 0.17 14.04 1.1 0.03 0.33 1.53 3.61 2.97 4365EMP1.1Cl=0.04; H2O=5.44EMP 0.98 56 906 412 13.4 22.3 2.4 9.2 1.27 0.43 1.66 0.15 0.78 0.14 0.61 0.42 0.66 0.08 5.3 106 3.69 2.94 0.3 4.98 2.06 4365LA-ICP


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