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Although the Matuyama-Brunhes boundary (MBB) in the Chinese Loess Plateau (CLP) is very important in reliably correlating Quaternary loess with other sediments in the world, particularly with marine and polar ice cores, its exact stratigraphic position remains controversial. Previous investigations usually placed the MBB between paleosol unit S8 and loess unit L8 in various locations. To better understand the spatial differences in the MBB position, a high-resolution paleomagnetic study was conducted in a loess section of the Lantian Basin at the southern margin of the CLP. The results show that the MBB is situated in the middle of the relatively weak paleosol unit S7, consistent with a recent report on the MBB based on a 10Be study from the Xifeng and Luochuan loess sections of the central CLP. However, the regional anomalously low magnetic susceptibility in paleosols S7 and S8 indicates that it is more reliable to determine the paleoclimate boundaries between loess and paleosol horizons of this segment with median grain size. Then, the MBB in the Yushan section can be correlated with the bottom of paleosol S7, corresponding to the older part of interglacial marine isotope stage 19. This result temporally reconciles the striking discrepancy of the position of the MBB recorded in between loess and other typical sedimentary sequences, and further confirms that the stratigraphic position of the MBB could spatially vary to a certain extent due to regional sedimentary or paleoclimatic conditions in the marginal areas of the CLP. In the Yushan section, the high-frequency variations of paleomagnetic directions during a long period of ~31 ka before the MBB, however, could not be attributed to a genuine response to the true geomagnetic behaviour. Moreover, the climate offset defined by the magnetic susceptibility and median grain size of the section can be preliminarily attributed to the regional geology and paleoenvironment background. A multiproxy-based stratigraphic division is considered very necessary when paleomagnetic and climatic boundaries are defined exactly in a specific area of the southern CLP. [ABSTRACT FROM AUTHOR]

On the Chinese Loess Plateau, stable carbon isotope values for total organic matter (δ 13 C TOC ) from more than 10 loess/paleosol sequences since the last glacial/interglacial show generally consistent variations, with enriched values normally occurring in paleosol layers. The only exceptions are records from the westernmost and northwestern Chinese Loess Plateau. However, both Asian summer monsoon intensity and temperature have been suggested as the principal factor affecting these consistently similar δ 13 C TOC variations. Until now, δ 13 C TOC records covering the whole Quaternary have been relatively rare, with problems including low resolution and conflicts in both the C 4 expansion history and with related climatic interpretations. In this paper, we report on high resolution, late Early Pleistocene low-frequency magnetic susceptibility ( χ lf ) and δ 13 C TOC data from Yushan section on the southern margins of the Chinese Loess Plateau. Our δ 13 C TOC data present an abstruse relation with the glacial/interglacial cycles represented by loess/paleosol sequences, with δ 13 C-enriched excursions in some paleosol layers and δ 13 C-depleted excursions in others. Furthermore, our δ 13 C TOC data shows negative and positive correlations with χ lf data, using a threshold χ lf value of 70 × 10 −8 m 3 /kg. If the χ lf data are taken as an indicator of pedogenetic intensity, and therefore an indicator of Asian summer monsoon intensity, there are two possible relations between Chinese loess δ 13 C TOC and Asian summer monsoon intensity, i.e. the Chinese loess δ 13 C TOC cannot simply be adopted as the sole indicator of Asian summer monsoon intensity, at least during the late Early Pleistocene on the southern margins of the Chinese Loess Plateau. Our results demonstrate that C 4 plants became a significant proportion of local vegetation cover only when Asian summer monsoon intensity exceeded a certain degree, for example, in the surface vegetation for the S15 and S16 paleosol layers of the Yushan section. The relation between climate and Chinese loess δ 13 C TOC requires further, detailed study. [ABSTRACT FROM AUTHOR]

The aeolian loess blanketing the Chinese Loess Plateau (CLP) is sensitive to climate change in monsoonal East Asia. Here, we present a multi-proxy climatic record from a Pleistocene loess-paleosol sequence from the Lantian Basin on the southern margin of the CLP. The measurements include magnetic susceptibility and related magnetic properties, bulk median grain-size, color reflectance, and the color-inferred hematite versus goethite ratio (Hm/Gt). A long-term aridification and cooling trend during the interval from ca 2.22–0.43 Ma is indicated by two magnetic grain-size proxies, corresponding to the global climatic cooling of the late Cenozoic. In addition, at least four intervals of climatic extremes are evident in the record of Hm/Gt ratio: at 1.71–1.65 Ma, 1.26–1.24 Ma, 0.94–0.86 Ma, and 0.62–0.48 Ma. These intervals are characterized by distinct regional climates, which contrast with the global climatic conditions represented in marine sediments. For example, a relatively arid climate is documented from 1.71 to 1.65 Ma, which was rapidly succeeded by a relatively humid climate which is associated with the earliest hominin (with an age of ca 1.63 Ma) in the Lantian Basin. [ABSTRACT FROM AUTHOR]