Tephrochronology and Provenance of an Early Pleistocene (Calabrian) Tephra From IODP Expedition 374 Site U1524, Ross Sea (Antarctica)

Abstract

We present a full characterization of a 20 cm-thick tephra layer found intercalated in the marine sediments recovered at Site U1524 during International Ocean Discovery Program (IODP) Expedition 374, in the Ross Sea, Antarctica. Tephra bedforms, mineral paragenesis, and major- and trace-element composition on individual glass shards were investigated and the tephra age was constrained by 40Ar-39Ar on sanidine crystals. The 40Ar-39Ar data indicate that sanidine grains are variably contaminated by excess Ar, with the best age estimate of 1.282 ± 0.012 Ma, based on both single-grain total fusion analyses and step-heating experiments on multi-grain aliquots. The tephra is characterized by a very homogeneous rhyolitic composition and a peculiar mineral assemblage, dominated by sanidine, quartz, and minor aenigmatite and arfvedsonite-riebeckite amphiboles. The tephra from Site U1524 compositionally matches with a ca. 1.3 Ma, rhyolitic pumice fall deposit on the rim of the Chang Peak volcano summit caldera, in the Marie Byrd Land, located ca. 1,300 km from Site U1524. This contribution offers important volcanological data on the eruptive history of Chang Peak volcano and adds a new tephrochronologic marker for the dating, correlation, and synchronization of marine and continental early Pleistocene records of West Antarctica.