Mt Churchill MTR-146 Tephra
Start: 6300 yBP [1]
Event Type: Explosive
Description: From Preece and others (2014): "...cores in southeastern Alaska contain two other tephra beds with compositions similar to WRA. These are the ca. 300 yr B.P. (ca. A.D. 1650) Lena ash preserved at sites A and B (Fig. 1 [in original text]) and the ca. 6330 cal yr B.P. MTR-146 ash preserved at site B (Fig. 1 [in original text]) (Payne and others, 2008)."
From Payne and others (2008): "There is also similarity in the composition of CHP 184, MTR 146, and LNA 100 tephras, although considerable differences in their probable age. Similarity coefficients of these tephras with WRA reference data are also high; SCs exceed 0.95 with at least one of the established data sets (Table 4 [in original text]). Similarity coefficients are most convincing with the LNA 100 tephra, with five of the values exceeding 0.95, and least convincing with the CHP 184 tephra, with only one of the SCs exceeding 0.95. A ternary diagram comparing CHP 184, MTR 146, LNA 100, SPM 26, LNA 39, and ECR 32 with the White River Ash reference data shows a convincing overlap (Fig. 3 [in original text]), providing evidence that these tephras are the WRA or have the same source. By contrast, SCs with many other tephras compared do not exceed 0.95."
"The ECR 162 tephra has been dated to 5030-5300 cal yr BP (SUERC-5917; Table 6). ECR 100, MTR 146, and MTR 190 tephras were not directly dated. Age-depth interpolation suggests that the ECR 100 tephra was deposited ca. 2840 cal yr BP, the MTR 146 tephra ca. 6300 cal yr BP, and the MTR 190 tephra ca. 8660 cal yr BP."
From Payne and others (2008): "There is also similarity in the composition of CHP 184, MTR 146, and LNA 100 tephras, although considerable differences in their probable age. Similarity coefficients of these tephras with WRA reference data are also high; SCs exceed 0.95 with at least one of the established data sets (Table 4 [in original text]). Similarity coefficients are most convincing with the LNA 100 tephra, with five of the values exceeding 0.95, and least convincing with the CHP 184 tephra, with only one of the SCs exceeding 0.95. A ternary diagram comparing CHP 184, MTR 146, LNA 100, SPM 26, LNA 39, and ECR 32 with the White River Ash reference data shows a convincing overlap (Fig. 3 [in original text]), providing evidence that these tephras are the WRA or have the same source. By contrast, SCs with many other tephras compared do not exceed 0.95."
"The ECR 162 tephra has been dated to 5030-5300 cal yr BP (SUERC-5917; Table 6). ECR 100, MTR 146, and MTR 190 tephras were not directly dated. Age-depth interpolation suggests that the ECR 100 tephra was deposited ca. 2840 cal yr BP, the MTR 146 tephra ca. 6300 cal yr BP, and the MTR 190 tephra ca. 8660 cal yr BP."
References Cited
[1] Using cryptotephras to extend regional tephrochronologies: an example from southeast Alaska and implications for hazard assessment, 2008
Payne, Richard, Blackford, Jeffrey, and van der Plicht, Johannes, 2008, Using cryptotephras to extend regional tephrochronologies: an example from southeast Alaska and implications for hazard assessment: Quaternary Research, v. 69, n. 1, p. 42-55.[2] Chemical complexity and source of the White River Ash, Alaska and Yukon, 2014
Preece, S.J., McGimsey, R.G., Westgate, J.A., Pearce, N.J.G., Hart, W.K., and Perkins, W.T., 2014, Chemical complexity and source of the White River Ash, Alaska and Yukon: Geosphere, v. 10, n.5., p. 1020-1042, doi: 10.1130/GES00953.1Complete Eruption References
Using cryptotephras to extend regional tephrochronologies: an example from southeast Alaska and implications for hazard assessment, 2008
Payne, Richard, Blackford, Jeffrey, and van der Plicht, Johannes, 2008, Using cryptotephras to extend regional tephrochronologies: an example from southeast Alaska and implications for hazard assessment: Quaternary Research, v. 69, n. 1, p. 42-55.
Chemical complexity and source of the White River Ash, Alaska and Yukon, 2014
Preece, S.J., McGimsey, R.G., Westgate, J.A., Pearce, N.J.G., Hart, W.K., and Perkins, W.T., 2014, Chemical complexity and source of the White River Ash, Alaska and Yukon: Geosphere, v. 10, n.5., p. 1020-1042, doi: 10.1130/GES00953.1
