Temporal dissection of the Huckleberry Ridge Tuff using the 40Ar/39Ar dating technique

Ellis, Ben; Mark, Darren; Pritchard, Chad; Wolf, John

New high-precision single crystal sanidine 40Ar/39Ar ages for theHuckleberry Ridge Tuff (HRT), Yellowstone volcanic field, show that the three HRT members (A, B, and C) represent at least two different eruptions. The new 40Ar/39Ar ages (all ages calculated relative to the optimisation model ofRenne et al., 2011) are: 2.135 [plus or minus] 0.006 Ma, 2.131 [plus or minus] 0.008 Ma, and 2.113 [plus or minus] 0.004 Ma (2[delta], full uncertainty propagation), for members A, B and C, respectively. Members A and B are within uncertainty of one another and both are more precise than, but in agreement with, previously published ages. Member C was erupted later than members A and B. HRT members A and B were deposited during the Reunion Normal Polarity Subchron (C2r.1n). Member C was deposited during Subchron C2r.1r. Previously published radiogenic and stable isotope data show that member C was sourced from an isotopically discrete magma with a higher fraction of crustal material than members A and B. The volume ofthe first HRT eruption is reduced by c. 12% from previous estimates and explosive eruptions from the Yellowstone volcanic field occurred more frequently, producing more homogeneous magma than was previously believed. High-precision 40Ar/39Ar dating is key for resolving the eruptive history of Yellowstone, temporaldissectionof voluminous ignimbrites, and rigorous investigation of what constitutes a "super-eruption".

Temporal dissection of the Huckleberry Ridge Tuff using the 40Ar/39Ar dating technique

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