Branched GDGT in the Hupo Trough (Southwestern East Sea) as a Record of the Terrestrial Climate Change in East Asia Since the Last Glacial Maximum

Branched glycerol dialkyl glycerol tetraether (brGDGT) is a ubiquitous biomarker in peat and soil used widely to reconstruct terrestrial paleoclimate change. On the other hand, it has rarely been reported in paleoclimatic studies on the Korean Peninsula. The present study analyzed the brGDGT of core sediments (ES14-GC02) collected from the Hupo Trough (southwestern East Sea) to test whether the brGDGT proxies reflect the terrestrial environmental conditions of East Asia including the Korean Peninsula. At the core-top sediments, the brGDGT-derived mean annual air temperature (MAAT, ca. 13.7 degrees C) concurred with the modern annual mean of measured atmospheric temperature (ca. 13.3 degrees C). Core ES14-GC02 is characterized by two lithologic units: a high MAAT and pH in the upper Unit A and a low MAAT and pH in the lower Unit B. In particular, a bi-plot of CBT (cyclization ratio of branched tetraethers) and MBT ' (methylation index of branched tetraethers) shows the distinct difference between the last glacial maximum (LGM) and the Holocene. These results indicate that the sources of brGDGT in the Hupo Trough are complex (in situ production, terrestrial source, and unknown source). Thus, great care should be taken when interpreting the absolute value of MAAT in the Hupo Trough. Nevertheless, despite this caveat, the downcore variation of the brGDGT proxies reflects changes in the terrestrial environment in the Korean Peninsula since the LGM. This study suggests that branched GDGTs of neritic marine sediments can be used to improve terrestrial paleoclimatic studies on the Korean Peninsula.

Automated summary

The present study analyzed core sediments from the Hupo Trough in the Korean Peninsula to test whether brGDGT proxies can reflect terrestrial environmental conditions. The results showed distinct differences in MAAT and pH between two lithologic units, indicating changes in the terrestrial environment since the last glacial maximum. The study suggests that branched GDGTs of neritic marine sediments can improve terrestrial paleoclimatic studies on the Korean Peninsula.