MIS3 climate changes based on loess records in the Hanzhong Basin, south of the Qinling Mountains, China

ABSTRACT Marine Isotope Stage 3 (MIS3) was a relatively warm and humid, although variable, time in the last glacial period in the northern hemisphere. This climate phase is well‐recorded in various archives (e.g., ice cores, speleothems, and loess) from many parts of the world, including China, although its expression (e.g., warm–humid vs. cool–dry) differed between the hemispheres. However, despite its location in a critical climatic boundary zone and high sensitivity to climate changes, few studies have investigated the MIS3 climate based on the loess records in the Hanzhong Basin (China). In this study, we performed systematic sampling of a loess−paleosol sediment sequence and performed physicochemical analyses and optically stimulated luminescence dating after detailed field observations and descriptions. The results indicated that the time of formation of the lower part of the Malan loess ( L 1 − 2 ) occurred between 55.0–25.6 ka BP, corresponding to MIS3. The magnetic susceptibility, clay content (<5 μm), a *, a */ b *, and contents of Fe 2 O 3 , Al 2 O 3 , Chemical Index of Alteration, and eluvial coefficient were all significantly higher, while the sand content (>50 μm), L *, ba , a , and the contents of Na 2 O, CaO, and Na/K were lower than those in the loess L 1 − 1 (corresponding to MIS2). These findings indicate that the degree of weathering of the loess in MIS3 was higher than that in MIS2, suggesting that the change to a warm–humid climate during MIS3 is reflected in the sediment of the Hanzhong Basin. However, the climate was not as warm or as humid as that during the mid‐Holocene, as indicated by the weaker degree of weathering of the paleosol S 0 . The climate fluctuated obviously during MIS3, including three warm–humid intervals and three dry–cold intervals. Although the relatively warm–humid and unstable characteristics of the late MIS3 in the Hanzhong Basin are similar to the climate records in other parts of the world, they are considered to be regionally specific responses of the Hanzhong Basin to global climate change.