A new method for loess chronology by microcodium δ18O and its application to the Mangshan section

Abstract

Mangshan section is a scarce and valuable high-sedimentation deposit at the southeastern margin of the Chinese Loess Plateau for high-resolution paleoclimate reconstructions. Although the chronology of the deposit above the paleosol layer S2 has been pinned down on the glacial-interglacial timescale, it still needs to be refined at orbital timescale, especially at the boundary from loess layer L2 to paleosol layer S1. In the age model by correlation of loess grain size with the benthic oxygen isotope (δ¹⁸O) records, the lack of paleosol and low magnetic susceptibility during the marine isotope stage 5e are substantially different from the observations in other loess-paleosol sequences on the Chinese Loess Plateau. Here, we analyzed the oxygen isotope composition of microcodium from the upper loess layer L2 and paleosol layer S1 of the Mangshan section to reconstruct the oxygen isotopic stratigraphy. Comparing it with the absolute-dating speleothem δ¹⁸O record, we suggest corresponding the paleosol layer S1 to the last interglacial, which is consistent with other loess-paleosol sequences on the Chinese Loess Plateau. Our study provides a new method for the loess chronology by tuning the microcodium δ¹⁸O record to the absolute-dating speleothem δ¹⁸O record.