Detection of Strong Precession Cycles from the Late Pliocene Sedimentary Records of Northeastern Tibetan Plateau

Recent studies demonstrate that aridification is sensitive to eccentricity forcing based on the northeastern Tibetan Plateau Cenozoic fluvio-lacustrine stratigraphic records. However, it is unknown whether this is a bias associated with the fact that higher frequency periods normally have larger age model uncertainties, which tend to decrease spectral power of higher frequency orbital cycles (precession and obliquity) and enlarge lower frequency ones (eccentricity). Here we detect strong and well-resolved (similar to 23 and similar to 19 kyr) precession cycles in the magnetic susceptibility record of late Pliocene fluvio-lacustrine sediments from the Qaidam Basin, northwestern China. We interpret the magnetic susceptibility as a proxy for the degree of chemical weathering in this region, based on the positive correlation between low-frequency magnetic susceptibility and frequency-dependent magnetic susceptibility. The different responses of magnetic susceptibility and a halite content proxy to orbital forcing suggest that aridification is more sensitive to eccentricity forcing than precipitation, but precipitation is more sensitive to precession forcing. This study indicates that different climatic aspects have different sensitivity to orbital forcing. Furthermore, a comparison of the magnetic susceptibility variations in the western Qaidam Basin and global ice volume proxy records suggests ice volume control of Qaidam Basin precipitation and chemical weathering at million-year timescales. Plain Language Summary The cyclicity of Earth's climate is driven by changes in solar insolation associated with variations in Earth's orbital parameters (precession, obliquity, and eccentricity). It remains unclear how different climate processes respond to different orbital forcing. Here, proxy records of aridification and precipitation from the northeastern Tibetan Plateau suggest that variations in aridification were sensitive to eccentricity forcing, while the precipitation changes were sensitive to precession forcing during the late Pliocene. This study indicates that different climatic systems have different sensitivity to orbital forcing.