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.

中文翻译：

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来自 IODP Expedition 374 Site U1524，罗斯海（南极洲）的早期更新世（卡拉布里亚）火山岩的年代学和出处

我们展示了在南极洲罗斯海的国际海洋发现计划 (IODP) 远征 374 期间发现的 20 厘米厚的火山灰层的完整表征，该火山灰层插入在 U1524 站点回收的海洋沉积物中。研究了单个玻璃碎片上的火山灰床形态、矿物共生以及主要和微量元素组成，并且火山灰的年龄受到sanidine 晶体上⁴⁰ Ar- ³⁹ Ar 的限制。在⁴⁰ AR- ³⁹Ar 数据表明，sanidine 晶粒不同程度地受到过量 Ar 的污染，基于单晶粒全融合分析和多晶粒等分试样的步进加热实验，最佳年龄估计为 1.282 ± 0.012 Ma。火山灰的特点是非常均匀的流纹岩成分和奇特的矿物组合，主要是闪石、石英和少量的黑云母和阿弗德森石-里贝克闪石。来自 Site U1524 的火山灰在成分上与大约相匹配。1.3 Ma，流纹质浮石沉积在Chang Peak 火山顶火山口的边缘，位于Marie Byrd Land，位于ca. 距站点 U1524 1,300 公里。这一贡献提供了有关长峰火山喷发历史的重要火山学数据，并为年代学、相关性、