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Sinters in the rift valleys of southern Tibet, including silica sinter and travertine deposits, are the products of hydrothermal activity under regional tectonic movement. Their formation age is significant for studying hydrothermal activity history in this region. Electron spin resonance (ESR) dating is a practical dating method for determining the age of silica sinter and travertine deposits. However, silica sinter's ESR signals vary due to the complex composition. Meanwhile, these ESR signals are mixed, superimposed, and interfere with each other, affecting the ESR signal's measurement. Furthermore, ESR dating has been applied less in travertine samples in southern Tibet, which is not conducive to a comprehensive understanding of the hydrothermal activity history in southern Tibet. Studying the applicability of ESR dating of southern Tibetan silica sinter and travertine deposits helps obtain accurate ESR ages. It lays the chronologic foundation for researching tectonic activities in these rift valleys. This research applied ESR dating to the silica sinter and travertine deposits collected separately from the Targejia thermal field area and the Xiakangjian hot spring area, located in the Ngri-Xigaze area in southern Tibet. We performed ESR dating tests, including how to choose ESR signals, the effect of additional doses, and the thermal stability of ESR signals in travertine. Based on these tests, relatively accurate, reliable ESR ages of silica sinter and travertine were obtained. The results show that: According to the ESR dating results, the silica sinter samples collected from the fourth and third terrace of the Targejia geothermal field were formed at 177±20 and 81±16 ka, respectively, and the travertine deposits collected from the floodplain and first terrace of the Xiakangjian hot spring were formed at 106±32 ka and 264±26 ka, respectively. In terms of irradiation dose, sinter samples collected from southern Tibet respond well to irradiation dose in the range of 0~7680 Gy; In terms of temperature, silica sinter samples are less affected by closure temperature, and the thermal behavior of the ESR signal at g=2.0034 of travertine in southern Tibet is stable in the range of 20 ℃~250 ℃ that is suitable for ESR dating. Regarding mineral structure, The travertine in southern Tibet has better mineral purity and crystallinity; thus, the ESR age results are relatively accurate.

We present a new reconstruction of summer sea-surface salinity ( SSS) over the past 15 000 years based on a diatom record from piston core 17940, located on the northern slope of the South China Sea ( SCS). The reconstructed diatom-based summer SSS values for the modern period are in accord with instrumental observations of summer SSS in the area. Here, the modern summer SSS is primarily controlled by river runoff, in particular from the Pearl River. The reconstruction presented in this study shows that the summer SSS varied between 33.3 and 34.2 psu over the past 15 000 years. The long-term summer SSS trend closely followed the trend of the orbitally controlled solar insolation at 20° N, suggesting that orbital forcing was the dominant driver of changes in summer SSS in this area. Comparisons to speleothem δ 18O data and studies of surface hydrography in the region suggest that changes in solar insolation affected the summer SSS through changes in the East Asian Monsoon and sea-level changes associated with the last deglaciation. Univariate spectral analyses indicate that centennial-scale oscillatory variations in summer SSS were superimposed on the long-term trend. During the deglacial period ( c. 12 000-9000 cal. a BP), the dominant periodicity was centred around 230-250 years, whereas a ∼350-year oscillation dominated in the period 2200-4500 cal. a BP. The balance of evidence suggests that these centennial-scale changes in summer SSS may have been driven by solar-induced changes in the East Asian Monsoon, but further evidence is needed to firmly establish this relationship. [ABSTRACT FROM AUTHOR]

Diatom assemblages from Holsteinsborg Dyb on the West Greenland shelf were analysed with high temporal resolution for the last 1200 years. A high degree of consistency between changes in frequency of selected diatom species and instrumental data from the same area during the last 70 years confirms the reliability of diatoms (particularly sea-ice species and warm-water species) for the study of palaeoceanographic changes in this area. A general cooling trend with some fluctuations is marked by an increase in sea-ice species throughout the last 1200 years. A relatively warm period with increased influence of Atlantic water masses of the Irminger Current (IC) is found at ad 750–1330, although with some oceanographic variability after ad 1000. A pronounced oceanographic shift occurred at ad 1330, corresponding in time to the transition from the so-called ‘Medieval Warm Period’ (MWP) to the ‘Little Ice Age’ (LIA). The LIA cold episode is characterized by three intervals with particularly cold sea-surface conditions at ad 1330–1350, ad 1400–1575 and ad 1660–1710 as a result of variable influence of Polar waters in the area. During the last 70 years, two relatively warm periods and one cold period (the early 1960s to mid-1990s) are indicated by changes in the diatom components. Our study demonstrates that sedimentary records on the West Greenland shelf provide valuable palaeoenvironment data that confirm a linkage between local and large-scale North Atlantic oceanographic and atmospheric oscillations. [ABSTRACT FROM AUTHOR]