Expanding the tephrostratigraphical framework for the South Shetland Islands, Antarctica, by combining compositional and textural tephra characterisation

• Published in: Sedimentary Geology
• Main Authors: Liu, E. J., Oliva, M., Antoniades, D., Giralt, Santiago, Granados, I., Pla-Rabes, S., Toro, M., Geyer, Adelina
• Other Authors: Ministerio de Educación y Cultura (España), Ministerio de Ciencia e Innovación (España)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2016
• Subjects: Tephrostratigraphy; Volcanology; Antarctica; Livingston Island; Deception Island; Lake sediments; Byers; Byers peninsula; Cierva; Island Lake; Limnopolar Lake; South Shetland Islands; Antarc*; International Polar Year
• Online Access: http://hdl.handle.net/10261/139633; https://doi.org/10.1016/j.sedgeo.2015.08.002; https://doi.org/10.13039/501100004837

Tephra layers preserved in lake sedimentary sequences provide valuable isochrons with which to synchronise palaeoclimatic records. However, in regions where tephra inputs are dominated by a single volcanic source, overlapping chemical compositions can preclude unambiguous correlation of tephra layers. In this study, we characterise multiple visible (macrotephra) layers within sedimentary sequences from three lakes in Byers Peninsula, Antarctica. By combining compositional analyses with additional constraints from textural componentry, we identify three distinct tephra isochrons—T1, T2, and T3—each with distinct textural properties. The relative proportion of glassy compared to crystal-rich grains varies from ~ 50% (T3) to ~ 3% (T1) of the total sample. Although the proportion of dense to vesicular grains differs only slightly between all sampled tephra layers, the dominant vesicle shape varies from spherical (T3) to irregular and polylobate (T1/T2). These textural differences can be related to variations in the eruptive processes occurring at the Deception Island source volcano. This study highlights the efficacy of a correlative approach based on both chemical and physical tephra properties for deconvolving the tephra stratigraphy in regions where chemical compositions are non-unique. Field work in Limnopolar Lake was supported by grant POL2006-06635/CGL from the Education and Culture Ministry (Spain) in the framework of the International Polar Year 2007-09 activities. AG is grateful for her Juan de la Cierva Grant (JCI-2010-06092) and Ramón y Cajal contract (RYC-2012-11024). Part of this research was supported by the MICINN grant CTM2011-13578-E. Peer Reviewed