Geochemical characterization, correlation, and optical dating of tephra in alluvial sequences of central western Argentina

Toms, Phillip S and King, Matthew and Zárate, Marcelo A and Kemp, Rob A and Foit, Franklin F (2004) Geochemical characterization, correlation, and optical dating of tephra in alluvial sequences of central western Argentina. Quaternary Research, 62 (1). pp. 60-75. ISSN 00335894

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Abstract

The synthesis of paleoclimatic archives provided by loess and alluvial sequences of central Argentina has been hindered by the lack of a cohesive lithostratigraphic framework extending across the Chaco–Pampean plains and catchments of the Rios Desaguadero, Colorado, and Negro. This condition originates in part from the dearth of absolute chronological controls. The occurrence of discrete tephra layers across this region may provide an opportunity to address this deficiency if a tephrochronological framework can be established. The potential of such a project is assessed within the context of a pilot study constrained within alluvial sequences of central western Argentina proximal to potential source vents in the Southern Volcanic Zone. The intersite discrimination and correlation of tephra layers on a geochemical basis is examined, with indirect chronological control for the eruption of each generated by optical dating. Alluvial sediments on either side of each of five tephra units at a type site were dated using the optically stimulated luminescence of fine-silt-sized quartz, thus providing an age control on each tephra (ca. 24,000, 30,000, 32,000, 39,000, and 48,000 yr). The geochemical composition of each tephra was derived. Using these data, tephra layers at other sites in the study area were geochemically analyzed and, in instances of statistical concordance in major oxide structure, correlated to the type site and therefore ascribed ages. This methodology identified a further sixth volcanic event between ca. 24,000 and 30,000 yr not registered by type-site tephras. The extension of this initial tephrochronological framework beyond the alluvial sequences of central western Argentina is encouraged by the occurrence of geochemically distinct tephra verified and dated in this study.

Item Type: Article
Article Type: Article
Subjects: G Geography. Anthropology. Recreation > GB Physical geography
Divisions: Schools and Research Institutes > School of Natural & Social Sciences > Environmental Sciences
Research Priority Areas: Environmental Dynamics & Governance
Depositing User: Phillip Toms
Date Deposited: 13 Nov 2015 09:38
Last Modified: 13 Nov 2015 09:38
URI: http://eprints.glos.ac.uk/id/eprint/2815

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