Problems of Developing the Pleistocene Radiocarbon Chronology within high Mountain Terranes by the Example of Russian Altai. Issue 6 (22nd July 2019)

• Record Type: Journal Article
• Authors: Agatova, Anna; Nepop, Roman; Zazovskaya, Elya; Ovchinnikov, Ivan; Moska, Piotr
• Editors: Nadeau, Marie-Josée
• Is Part Of: Radiocarbon. Volume 61:Issue 6(2019)
• Page Start: 2019
• Page End: 2028
• Publication Date: 2019-07-22
• Subjects: apparent 14C ages, -- paleogeographical reconstructions, -- radiocarbon dating, -- Russian Altai; Radiocarbon dating -- Periodicals; 930.1028505
• DOI: 10.1017/RDC.2019.83
• Languages: English
• ISSNs: 0033-8222

Abstract

ABSTRACT: The paper presents a discussion of 24 radiocarbon ( 14 C) dates of organic material from deposits of various genesis within the intermountain depressions and valleys of the Russian Altai. These apparent 14 C ages (sometimes near the upper time limit of the 14 C dating method) contradict to other proxy data and optically stimulated luminescence (OSL) dates. Rejuvenation of ancient deposits by 14 C dating encountered two problems: (1) wrong interpretation of previously unknown near-surface location of Tertiary deposits as being of the Pleistocene ones with the redeposited ancient flora; and (2) wrong age estimation of the Pleistocene-Holocene deposits with redeposited Carboniferous, Jurassic, and Neogene organic material, which is represented as inclusions. Significant scattering of 14 C ages, their inversion within a section, and discrepancy with other proxy data indicate penetrating of the "young" carbon into ancient organic material, and its presence in a unique (for each sample) ratio. Today such contamination cannot be eliminated utilizing standard pre-treatment techniques. The influx of "young" carbon is related to post-sedimentation tectonic and exogenous processes, which are common for tectonically active mountain provinces including Altai. The reported problem is not a new one, although methodological studies in the Russian Altai have not yet been carried out earlier.