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Section Contents
Press Release : Aims : Methods : Background : Key Conclusions : Wider Implications : Related Publications
Approach and Methods
The work is based on combined evidence from geomorphic mapping, dating of mapped landforms, and ice sheet modelling.
We study a transect of sites through southern South America, as shown to the left.
1. Strait of Magellan - Bahia Inutil
2. Torres del Paine
3. Lago Buenos Aires and NPI-SPI 'gap'
< Map of Southernmost South America showing tectonic plate margins, present day icefields, former glacier limits and mean annual temperatures. After Caldenius (1932), Clapperton (1993), McCulloch et al. (2000) and Hollin & Schilling (1981).
Geomorphological Mapping
Geomorphological mapping forms the basis for interpreting the observed glacial chronology. our work builds on early Scandinavian work in the area, which identified the main features of the glaciation of southernmost Patagonia (e.g. Nordenskjold (1899), Caldenius (1932)). Landforms indicative of glacial activity are initially mapped using aerial photography. This work is followed up by more detailed assessment of the landforms in the field. When this evidence is incorporated into a dated chronology (see below), this enables conclusions to be drawn as to the processes occurring in landform generation, and thus the possible climatic implications. Ice limits derived from the geomorphological evidence and dated are shown in the Figures below.
(a.)The ice-dammed lake and ice limit during glacial stage E, co-inciding with the Antarctic Cold Reversal. After McCulloch et al.(2004).
(b.)Moraine limits of the last glaciation in the Strait of Magellan and Bahia Inutil. We argue that the outer moraines formed around 23-25ka, and the innermost ridge by 12.2ka, based on radiocarbon and cosmogenic isotope analyses.
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Dating the Landforms
Dating methods allow us to asign ages to the mapped landforms, and thuscreate a dated chronology of glacial events.
1. Tephrochronology & Radiocarbon
Radiocarbon dating is used in combination with tephrochronology to achieve dating control on the mapped moraines. We use exposed sections and cores to record sedimentology.
2. Cosmogenics
Cosmogenic dating provides further dating control. Boulders on moraine crests (as shown to the right) are dated to provide ages for moraine deposition, and thus glacial stages.
Collecting samples from boulders for cosmogenic isotope analysis. Twenty cosmogenic isotope exposure ages have been aquired to date varous ice margins. >
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