Revised calibration of the MBT-CBT paleothermometer based on branched tetraether membrane lipids of soil bacteria (original) (raw)

Abstract

The recently developed MBT-CBT proxy for the reconstruction of continental air temperature and past soil pH is based on the distribution of branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in soils. The Methylation of Branched Tetraether (MBT) and the Cyclisation of Branched Tetraether (CBT) indices were developed to quantify these distributions and significant empirical relations between these indices and annual mean air temperature (MAT) and/or soil pH were found in a large data set of soils. In this study, we extended the soil dataset to 278 globally distributed surface soils. Of these soils, 26% contains all nine branched GDGTs, while in 63% of the soils the seven most common branched GDGTs were detected, which were selected for calibration purposes. This resulted in new transfer functions for the reconstruction of pH based on the CBT index, as well as for MAT based on the CBT index and adjusted MBT index (MBT'). The new transfer function for MAT has a su...

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