An alternative method for dating unknown tephras based on a segmented regression model
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In CoDaWork’05, we presented an application of discriminant function analysis (DFA) to 4 different
compositional datasets and modelled the first canonical variable using a segmented regression model
solely based on an observation about the scatter plots. In this paper, multiple linear regressions are
applied to different datasets to confirm the validity of our proposed model. In addition to dating the
unknown tephras by calibration as discussed previously, another method of mapping the unknown tephras
into samples of the reference set or missing samples in between consecutive reference samples is
proposed. The application of these methodologies is demonstrated with both simulated and real datasets.
This new proposed methodology provides an alternative, more acceptable approach for geologists as their
focus is on mapping the unknown tephra with relevant eruptive events rather than estimating the age of
unknown tephra.
Kew words: Tephrochronology; Segmented regression
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