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Asian marginal seas play an important role in moderating material and energy flux linkages between Asia and the Northwest Pacific, and thus have profound climatic and environmental effects. In this study, by combining paleomagnetic study with sediment grain-size analysis on the Lz908 borehole sedimentary sequence from the southern Bohai Sea, new insights into regional geomorphological process since the late early Pleistocene are obtained. The main results are as follows. (1) Paleomagnetic findings suggest that the sequence recorded the Brunhes normal chron and the late Matuyama reverse chron, including the Jaramillo normal subchron. (2) The sedimentary processes in the study area since 1327 ka show a three-stage pattern, with depositional rates of 4.3, 17 and 107 cm/ka during 1327–260 ka (later part of the early and middle Pleistocene), 260–10 ka (late middle and late Pleistocene), and the Holocene, respectively. (3) The sedimentary basin was a part of the Bohai Paleolakes (BHPL) prior to 260 ka, whose water levels were consistently higher than 3 m above the present-day level. After 260 ka, seawater entered the Bohai basin, and relative sea level cyclically fluctuated with global sea-level changes. We therefore infer that the Miaodao Islands, which were the natural barrier of the BHPL blocking seawater entry, had partially subsided before 260 ka, only allowing seawater to enter the basin during a global sea-level maximum. The BHPL terminated around 260 ka, and the “barrier” subsided completely around ~ 130 ka, causing the Bohai basin to become an inner shelf sea. [ABSTRACT FROM AUTHOR]

It has been suggested that the standardized growth curve (SGC) method can be used to accurately determinate equivalent dose (D) and reduce measurement time. However, different opinions regarding the applicability of the SGC method exist. In this paper, we evaluated quartz OSL SGCs of marine and coastal sediments of different grain sizes and different cores in the south Bohai Sea in China, and tested their applicability to the determination of D values. Our results suggested as follows: (1) The SGC method is applicable to both multiple- and single-aliquot regenerative-dose (MAR and SAR) protocols of OSL dating and efficiently provides reliable estimates of D. (2) Finesand quartz of different palaeodoses showed highly similar dose-response curves and an SGC was developed, but old samples using the SGC method have large uncertainties. (3) For coarse-silt quartz, two different types of dose-response curves were recorded: low-dose (≤60Gy) and high-dose (≥100Gy). The growth curves of low-dose quartz were similar to each other, facilitating the use of SGC in D estimations, but errors tended to be larger than those obtained in the SAR method. For high-dose (100-300Gy) quartz, the SGC was also found to be reliable, but there was large uncertainty in D (>300Gy) estimation. We suggest that SGC could be employed for the dating of marine and coastal sediments dating using either MAR or SAR OSL protocol and either fine-silt, coarse-silt or fine-sand quartz. [ABSTRACT FROM AUTHOR]

Abstract: Future anthropogenic sea-level rise and its impact on coastal regions is an important issue facing human civilizations. Due to the short nature of the instrumental record of sea-level change, development of proxies for sea-level change prior to the advent of instrumental records is essential to reconstruct long-term background sea-level changes on local, regional and global scales. Here, we employ numerical methods to partition sediment grain size using a combined database of marine surface and core samples, and to quantitatively reconstruct sea-level variation since the late Pleistocene in the south Bohai Sea, China. Our sea-level reconstruction indicates that relative sea-level changes in the southern Bohai Sea track global sea-level variation for the duration of the record. The results also indicate substantial regression from 70 to 30calkyrBP, and potentially subarial exposure from 38 to 20calkyrBP. Our results document the feasibility of reconstructing relative sea-level change by numerical partitioning of sediment grain size data, demonstrating the potential for future applications. [Copyright &y& Elsevier]

Abstract: The Bohai Sea was formed by subsidence during the Cenozoic. Some 2000–3000m of fluvial, lacustrine and marine sediments has been deposited in this basin. Previous studies focused mainly on the transgression history, with little examination of orbital variation in relation to other areas within the Asian monsoon domain. Here, we present the late Quaternary results of a new borehole in the south Bohai Sea. Optically stimulated luminescence and radiocarbon dating, which provide concordant age estimates, were employed to generate an initial chronology for the borehole. After refining the chronology through astronomical tuning, the results showed that: (1) the grain size variation represents Asian monsoon intensity which was dominated by both solar insolation (major) and global ice volume (minor) forcing; (2) the magnetic susceptibility indicates river incision processes which were sensitive to orbital tilt with influence from solar insolation; (3) the vegetation coverage responded to global ice volume coupled obliquity changes; and that (4) neither external nor internal factors could dominate the paleoenvironmental evolution on orbital timescales in an independent way, and they are both integrated in a complex pattern. We conclude that three different astronomical rhythms have affected coastal evolution, and that the sedimentary records in the south Bohai Sea, China, result from the nonlinear interaction and the complex response to driving processes. [Copyright &y& Elsevier]