Detection of tephra layers in antarctic sediment cores with hyperspectral imaging

• Published in: PLOS ONE
• Main Authors: Aymerich, Ismael F., Oliva, Marc, Giralt, Santiago, Martín-Herrero, Julio
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science 2016
• Subjects: EMTREE medical terms; Antarctica; imaging; lake; sediment; spatial analysis; volcanic ash; Antarctic; Antarc*; permafrost
• Online Access: http://hdl.handle.net/10261/129869; https://doi.org/10.1371/journal.pone.0146578

Tephrochronology uses recognizable volcanic ash layers (from airborne pyroclastic deposits, or tephras) in geological strata to set unique time references for paleoenvironmental events across wide geographic areas. This involves the detection of tephra layers which sometimes are not evident to the naked eye, including the so-called cryptotephras. Tests that are expensive, time-consuming, and/or destructive are often required. Destructive testing for tephra layers of cores from difficult regions, such as Antarctica, which are useful sources of other kinds of information beyond tephras, is always undesirable. Here we propose hyperspectral imaging of cores, Self-Organizing Map (SOM) clustering of the preprocessed spectral signatures, and spatial analysis of the classified images as a convenient, fast, non-destructive method for tephra detection. We test the method in five sediment cores from three Antarctic lakes, and show its potential for detection of tephras and cryptotephras. Core extraction and analyses were funded by the Portuguese Science Foundation through the HOLOANTAR (Holocene environmental change in the Maritime Antarctic: Interactions Between permafrost and the lacustrine environment) project and the Portuguese Polar Program (PROPOLAR).The AXA Research Fund sponsored M. Oliva’s research activities in Antarctica. Peer reviewed