Volcanic ash bands in the Frontier Mountain and Lichen Hills blue-ice fields, northern Victoria Land

摘要

Dust bands in the blue-ice of the Frontier Mountain meteorite trap (northern Victoria Land, Antarctica) were previously reported as upthrust basal debris. Four of them have now been sampled at Frontier Mountain and Lichen Hills. The absence of local rocks and sedimentary fragments, the ubiquitous abundant volcanic glass with no evidence for abrasion, the igneous minerals, the chemical compositions of glass and minerals and the bulk chemical compositions indicate that they are volcanic ash bands (tephra) and not glacial debris. Although hardly distinguishable in the field, the different volcanic ash bands are discriminated using mineralogical and chemical data, as well as particle size, abundance and vesicularity of glass. Chronological constraints, particle size and chemical compositions localize the source for the Frontier Mountain and Lichen Hills tephra within the recent activity of the Mount Melbourne Volcanic Province in northern Victoria Land; possible emission centres are the Pleiades (40 ± 50 ka to 3 ± 14 ka) and/or Mount Rittmann (3.97 Ma to present).