Loess deposits in the arid Central Asia contain valuable information on the evolution of local aridification and dust sources in the Northern Hemisphere. Xinjiang is located in the eastern part of Central Asia and previous researches have revealed the complex enhancement of magnetic susceptibility in loess–paleosol sequences. However, systematic magnetic archives of loess deposit in this arid Asian interior are still far from adequate. In this study, magnetic parameters combined with nonmagnetic properties (granulometry and chromaticity) were analysed on a loess section in Shawan (SW), northwestern China. The section shares a similar magnetic composition with those in the Chinese Loess Plateau (CLP) as well as other sites in Xinjiang. Ferrimagnetic components (magnetite and maghemite) dominate the magnetic signal while the contribution of antiferromagnetic phases (like hematite and goethite) and paramagnetic portions are relatively low. There is no specific correlation between magnetic concentration and pedogenic intensity in the SW section. In general, magnetic enhancement was largely influenced by the paleowind intensity. However, a positive correlation between magnetic susceptibility and pedogenesis is observed in the upper part (0–3.5 m depths), which is characterized by a moderate wind intensity. Moreover, pedogenesis might be responsible for the enhancement of fine magnetic particles in paleosols. Magnetic properties are controlled by coarse magnetic particles in the pseudo-single domain state, but a coarse stable single domain phase was found in certain paleosol samples. The input of detrital fractions from a nearby dust source probably controlled the magnetic properties while a superparamagnetic fraction, which has been deemed as a product of pedogenesis in the CLP, is limited in the SW section. Caution is needed to employ magnetic susceptibility directly for paleoclimatic assessment because of its uncertainty in the Xinjiang loess. However, the χARM/SIRM ratio enhanced in paleosols and has more potential as an alternative index for the weakly pedogenic degree in this area.
Geomagnetic excursions during Brunhes epoch have been brought to the forefront topic in paleomagnetic study, as they provide key information about Earth’s interior dynamics and could serve as another tool for stratigraphic correlation among different lithology. Loess–paleosol sequences provide good archives for decoding geomagnetic excursions. However, the detailed pattern of these excursions was not sufficiently clarified due to pedogenic influence. In this study, paleomagnetic analysis was performed in loess–paleosol sequences on the northern piedmont of the Tianshan Mountains (northwestern China). By radiocarbon and luminance dating, the loess section was chronologically constrained to mainly the last c.130 ka, a period when several distinct geomagnetic excursions were involved. The rock magnetic properties in this loess section are dominated by magnetite and maghemite in a pseudo-single-domain state. The rock magnetic properties and magnetic anisotropy indicate weakly pedogenic influence for magnetic record. The stable component of remanent magnetization derived from thermal demagnetization revealed the presence of two intervals of directional anomalies with corresponding intensity lows in the Brunhes epoch. The age control in the key layers indicates these anomalies are likely associated with the Laschamp and Blake excursions, respectively. In addition, relative paleointensity in the loess section is basically compatible with other regional and global relative paleointensity records and indicates two low-paleointensity zones, possibly corresponding to the Blake and Laschamp excursions, respectively. As a result, this study suggests that the loess section may have the potential to record short-lived excursions, which largely reflect the variation of dipole components in the global archives.
Over the past four decades, urban expansions driven by rapid economic development and climate change have exerted profound impacts on land-use dynamics in the Guangdong–Hong Kong–Macao Greater Bay Area. However, our understanding of the interplay of different urban landscape patterns in this rapid urbanization zone remains limited. This study examines remote sensing data from 1999, 2009, and 2019 to analyze the spatial heterogeneity of the urbanization impact on landscape patterns, as well as driving forces, in Zhuhai City, in the western part of the Great Bay. The findings reveal that land-use changes in Zhuhai City are primarily characterized by the conversion of cultivated land and water areas into construction land and forest land, particularly in the western part of the city. These changes may result from rapid urbanization, leading to increased fragmentation and spatial aggregation of landscape patterns. Landscape pattern changes in Zhuhai City were related to both socio-economic development and natural environment change. The urbanization has promoted the agricultural transformation with a loss of cultivated land and water areas. Additionally, this study suggests that the coordination of land use along with the protection and construction of the ecological environment is urgently needed to achieve sustainable development in the region.
The impact of human-induced fires on the surrounding environment has been particularly significant during the Anthropocene epoch. Neolithic burnt clay, which is widely distributed in the archaeological relics of ancient civilizations across the Eurasian continent, provides pivotal information about the ancient firing stories. However, understanding of the paleoenvironmental imprints of fire in burnt clay has been largely limited by the lack of sufficient analytical data on comprehensive knowledge of ancient firing conditions. In this study, a detailed magnetic analysis was conducted on burnt clay materials from a Neolithic site in Fujian, southeastern China, which presented a burnt clay-based record of the Neolithic firing temperature in relation to paleoenvironmental conditions. Based on magnetic analysis, the ancient firing temperature was determined to be approximately 620 °C, which is comparable with other records from Eurasian Neolithic sites. Frequency-dependent magnetic susceptibility provides alternative indicative information for ancient firing conditions in addition to conventional magnetic susceptibility. Furthermore, magnetic properties of burnt clay may decode the in-situ source characteristics with respect to geological background. In addition, a potential link between temporal variations in ancient firing temperatures in burnt clay and surrounding paleoenvironmental changes is tentatively interpreted by local environmental feedback of temperature-moisture conditions and anthropogenic activity. This study further confirms the archaeological potential of thermomagnetic properties as useful indicators in paleoenvironmental studies. More work combining paleoenvironmental and archaeological archives is critically essential to understand ancient firing history in the context of environmental conditions.