Early Holocene M~6 explosive eruption from Plosky volcanic massif (Kamchatka) and its tephra as a link between terrestrial and marine paleoenvironmental records

• Published in: International Journal of Earth Sciences
• Main Authors: Ponomareva Vera, Portnyagin Maxim, Derkachev Alexander, Pendea I. Florin, Bourgeois Joanne, Reimer Paula J., Garbe-Schönberg Dieter, Krasheninnikov Stepan, Nürnberg Dirk
• Format: Text
• Language: English
• Published: 2013
• Subjects: 38.37.25 Вулканология; Крестовский; Безымянный; Острый Толбачик; Плоский Толбачик; Средний; Ушковский; Ключевской; Bering Sea; Kamchatka Peninsula; Kamchatka
• Online Access: http://repo.kscnet.ru/1047/; http://repo.kscnet.ru/1047/1/Ponomareva%202013.pdf; https://doi.org/10.1007/s00531-013-0898-0

We report tephrochronological and geochemical data on early Holocene activity from Plosky volcanic massif in the Kliuchevskoi volcanic group, Kamchatka Peninsula. Explosive activity of this volcano lasted for ~1.5 kyr, produced a series of widely dispersed tephra layers, and was followed by profuse low-viscosity lava flows. This eruptive episode started a major reorganization of the volcanic structures in the western part of the Kliuchevskoi volcanic group. An explosive eruption from Plosky (M~6), previously unstudied, produced tephra (coded PL2) of a volume of 10–12 km3 (11–13 Gt), being one of the largest Holocene explosive eruptions in Kamchatka. Characteristic diagnostic features of the PL2 tephra are predominantly vitric sponge-shaped fragments with rare phenocrysts and microlites of plagioclase, olivine and pyroxenes, medium- to high-K basaltic andesitic bulk composition, high-K, high-Al and high-P trachyandesitic glass composition with SiO2 = 57.5–59.5 wt%, K2O = 2.3–2.7 wt%, Al2O3 = 15.8–16.5 wt%, and P2O5 = 0.5–0.7 wt%. Other diagnostic features include a typical subduction-related pattern of incompatible elements, high concentrations of all REE (>10× mantle values), moderate enrichment in LREE (La/Yb ~ 5.3), and non-fractionated mantle-like pattern of LILE. Geochemical fingerprinting of the PL2 tephra with the help of EMP and LA-ICP-MS analyses allowed us to map its occurrence in terrestrial sections across Kamchatka and to identify this layer in Bering Sea sediment cores at a distance of >600 km from the source. New high-precision 14C dates suggest that the PL2 eruption occurred ~10,200 cal BP, which makes it a valuable isochrone for early Holocene climate fluctuations and permits direct links between terrestrial and marine paleoenvironmental records. The terrestrial and marine 14C dates related to the PL2 tephra have allowed us to estimate an early Holocene reservoir age for the western Bering Sea at 1,410 ± 64 14C years. Another important tephra from the early Holocene eruptive episode of ...