High-resolution radiocarbon dating of the Luochuan loess and millennial-scale sedimentary hiatuses

Loess serves as an excellent archive for studying paleoclimate change. However, the existence of depositional hiatuses on the Loess Plateau, as well as their timing and mechanisms, remain unclear. In this study, a total of 58 samples were collected from a 4.75 m depth section at Luochuan(35.72° N, 109.42° E) in the central Chinese Loess Plateau. Based on 58 radiocarbon dates, a high-resolution and robust chronological framework has been established for the Luochuan section, covering the period during ca. 31.5~3.7 ka. The sedimentation rate during the Last Glacial Period was higher than that during the Holocene. However, within both the Last Glacial Period and the Holocene, periods of high sedimentation rates corresponded to intervals characterized by relatively warm and humid conditions, indicated by high magnetic susceptibility and low carbonate and dolomite content. During the Younger Dryas and Heinrich events, sedimentation rates decreased rapidly, and even depositional hiatuses occurred, suggesting that the sedimentation process was influenced by multiple factors, with dominant controls varying across different timescales. Depositional hiatuses were identified in the Luochuan section during ca. 20.3~16.7 ka and ca. 12.6~10.6 ka. Integrating previous high-resolution chronological results, we identified clear evidence for sedimentary hiatuses in at least eleven sections across the Chinese Loess Plateau region. Among these, hiatuses on the ten-thousand-year scale occurred in the desert-loess transitional zone in the northern part of the Loess Plateau, primarily influenced by desert expand/retreat and the alternation of dust accumulation areas into dust source regions. Millennial-scale sedimentary hiatuses occurred throughout the whole Chinese Loess Plateau. The timing of these hiatuses falls within ca. 20.6~8.7 ka and ca. 5.1~1.3 ka, with the highest probability of occurrence during ca. 13.6~10.3 ka. These periods include phases characterized by rapid climate shifts from warm-humid to cold-dry conditions. The abruptly weakened East Asian Summer Monsoon led to reduced precipitation and decreased vegetation cover, while concurrently strong East Asian winter winds collectively enhanced wind erosion and caused sedimentary hiatuses. Additionally, vegetation feedback processes and increased wildfire activity during these rapid climate transitions may have further promoted the occurrence of sedimentary hiatuses.