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Bayesian age modeling of a MIS 9 to 8 tephra sequence on the Kamchatka Peninsula (NW Pacific)

Vera Ponomareva1, Egor Zelenin 2, Natalia Bubenshchikova3, Maxim Portnyagin4, Sergei Gorbarenko5, Alexander Derkachev5, Florin Pendea6, Maria Pevzner2, Galina Malakhova7, Dieter Garbe-Schönberg8, 9

  • Affiliations: 1Institute of Volcanology and Seismology, Petropavlovsk-Kamchatsky, Russia; 2Geological Institute, Moscow, Russia; 3Shirshov Institute of Oceanology RAS, Moscow, Russia; 4GEOMAR Helmholtz Center for Ocean Research, Kiel, Germany; 5V.I. Il'ichev Pacific Oceanological Institute,Vladivostok, Russia; 6Sustainability Sciences Department, Lakehead University, Orillia, Canada; 7North-East Interdisciplinary Scientific Research Institute n.a. N.A. Shilo, Magadan, Russia; 8Kiel University, Kiel, Germany; 9Department of Physics and Earth Sciences, Jacobs University Bremen, Bremen, Germany 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 147

  • Programme No: 3.13.16

  • Theme 3 > Session 13

Abstract

Tephra layers provide a unique tool for correlating paleoenvironmental archives. One of the challenges, however, is obtaining robust age control for each tephra, which is often hampered by a lack of datable material. Here we discuss the dating of a tephra sequence buried in the "blue clays" lacustrine package -- the oldest outcropping sedimentary unit in the Central Kamchatka Depression (CKD), whose age estimates vary widely from early to late Pleistocene. Geochemical fingerprinting of the "blue clays" tephra layers using electron microprobe and LA-ICP-MS allowed tephra correlations among several CKD outcrops and the compilation of a composite tephra framework recording twenty-seven explosive eruptions. Seven of these tephras were correlated with their counterparts in marine sediment cores off Kamchatka, and thus their oxygen-isotope and paleomagnetic chronologies provided tie-points for the "blue clays" age model. The obtained sequence offers an ideal opportunity for the Bayesian modelling approach, as it has no directly dated tephra layers but combines in a single stratigraphy a number of tephras dated elsewhere. Our "blue clays" tephrochronological model spans 335-250 ka, or marine isotope stages 9 and 8, i.e. Penultimate Interglacial and the following cooling. Correlations of tephra layers revealed that independent source chronologies strongly support each other, yielding a uncertainty ≤10 ka. Correlations of precisely dated tephra layers provide direct links between marine and terrestrial paleoenvironmental archives from the Okhotsk Sea to Kamchatka and, farther east, across the NW Pacific. The research was supported by the Russian Science Foundation grant #22-17-00074.