A 15 ka pH record from an alpine lake in north China derived from the cyclization ratio index of aquatic brGDGTs and its paleoclimatic significance

摘要: Abstract A well-dated sediment core from an alpine lake in north China (Gonghai Lake) was used for analysis of branched glycerol dialkyl tetraether lipids (brGDGTs). Based on the cyclization ratio index (CBT) brGDGTs, and using different terrestrial lacustrine CBT-pH empirical relationships, reconstructed pH records over past ca. 15 ka exhibited similar trends variation, although absolute values were different. In order to better understand record, samples surface soils dust source area catchment Gonghai Lake, as well sediments lake, collected instrumental measurements modern brGDGT analysis. The results demonstrated that alkaline, while those Lake acidic. addition, slightly alkaline corresponding intermediate between two soil groups. This may reflect effect input material sources sedimentary record. However, brGDGTs some demonstrate are predominantly aquatic origin. Therefore, CBT-derived record can be interpreted a water history, which is consistent with carbonate content parallel same lake. calibration, Further comparison indicates controlled mainly by degree humidity local climate, closely related intensity East Asian summer monsoon (EASM); therefore, indicator EASM intensity. Our that, basis careful its origins, CBT reconstruction subsequent paleoclimate reconstruction, China, climate.