Inter-relationship and environmental significance of stalagmite δ¹³C and δ¹⁸O records from Zhenzhu Cave, north China, over the last 130 ka

There is a vigorous and ongoing debate about the interpretation of the stalagmite δ¹⁸O record from east China as an indicator of East Asian summer monsoon (EASM) intensity. This is mainly because of the inconsistent spatial variation of precipitation amount in east China, but the generally consistent variation of precipitation δ¹⁸O, on various timescales. However, a direct comparison of a proxy record of precipitation amount with the δ¹⁸O record from the same stalagmite has rarely been reported, especially in north China. Here, we present precisely-dated high-resolution stalagmite δ¹³C and δ¹⁸O records for the past 130 ka (1 ka =1000 years) from Zhenzhu (ZZ) Cave in north China. On multi-millennial to orbital timescales, the δ¹³C and δ¹⁸O records exhibit a high degree of in-phase co-variation; however, there are differences in the trend and amplitude of change between various marine isotopic stages (MIS): specifically, MIS5e, MIS5c, MIS5a, MIS3 and MIS1. Modern monitoring results of two years from ZZ Cave, together with a comparison of the δ¹³C record from the cave with a pedogenic carbonate δ¹³C record from the western Chinese Loess Plateau (CLP), demonstrate that the δ¹³C record is a sensitive and reliable indicator of EASM rainfall amount. Considering that variations in both the amount and δ¹⁸O of precipitation can be modulated by the atmospheric circulation system, we conclude that the amplitude and trend of the stalagmite δ¹⁸O variations from north China are not an absolute indicator of EASM intensity, but rather an indicator of changes in the phase of the EASM. We suggest that stalagmite δ¹⁸O records combined with other unambiguous proxy indicators from stalagmites can provide a more comprehensive history of changes of the EASM.