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

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. Plain Language Summary We report important information on the history and character of eruptions of Antarctic volcanoes. The study examines products from past explosive volcanic eruptions (tephra) preserved in marine sediments in the Southern Ocean that surrounds Antarctica. Tephra are invaluable markers for dating and correlating geological units, and can be used for the synchronization of climate proxy records. We present the full characterization of a 20 cm‐thick tephra recovered in deep‐sea marine sediments at Site U1524 during the International Ocean Discovery Program (IODP) Expedition 374, in the Ross Sea, Antarctica. The morphology of volcanic particles, their mineralogy, and chemical composition of volcanic glasses were assessed and the tephra age was constrained by the 40Ar‐39Ar method. Results allow to correlate the studied tephra with the deposits of a large explosive (Plinian) eruption from Chang Peak volcano, in the Marie Byrd Land, located c. 1,300 km from the Site U1524. The study of the marine tephra provides glimpses of the history of explosive volcanism from the Marie Byrd Land and constitutes a new, very important chronostr