Double-plunging structure of the Bond 4 event evidenced in new mid-Holocene stalagmite records from northern China

The Holocene epoch is characterized by a series of centennial-scale abrupt climate events. However, the temporal framework and internal structure of the Bond 4 event remain poorly constrained owing to the limited availability of precisely dated, high-resolution proxy records. Here, we present multi-proxy (δ¹³C, δ¹⁸O, and Mg/Ca) records from two precisely ²³⁰Th-dated stalagmites (XS4 and XS5) from Xingshan Cave in northern China, spanning the mid-Holocene (∼7.01–5.22 ka BP). Covariations in δ¹⁸O, δ¹³C, and Mg/Ca suggest a coupling between East Asian Summer Monsoon (EASM) intensity (indicated by δ¹⁸O) and hydrological changes (indicated by δ¹³C and Mg/Ca) in our study region, supported by regional paleoclimate comparisons. Our analysis reveals a pronounced double-plunging structure during the Bond 4 event (∼6.21–5.82 ka BP), with two major plunges centered at ∼6.14 ka BP and ∼5.90 ka BP. The new evidence presented here suggests that solar activity paced the timing and structure of the event, while internal variabilities (e.g., Atlantic Multidecadal Oscillation and El Niño–Southern Oscillation) and volcanic eruptions potentially amplified EASM weakening and drought severity. These findings highlight the complex interplay between external and internal forcing in shaping Holocene monsoon variability.