现代环境研究室知识库

The alternation of terrestrial and marine deposits is an indicator of past environmental and sea-level changes. The age of deposition is usually dated by means of radiocarbon. However, radiocarbon dates of molluscan shells from coastal areas may be complicated by various sources of carbon, and problematic for deposits of 4050ka or older. Herein, we apply the Optically Stimulated Luminescence (OSL) dating method to date samples from terrestrial and marine/coastal sediments extracted from three cores in the south Bohai Sea, China. Multiple- and single-aliquot regenerative-dose procedures using OSL signals from fine-silt (411m), coarse-silt (3863m) and fine-sand (6390 or 90125m) quartz were employed to determine the equivalent dose (D e). The results showed that: (i) OSL ages from quartz of different grain sizes and different protocols are consistent with each other; (ii) for Holocene samples, most of the radiocarbon dates agree well with OSL ages; (iii) for pre-Holocene samples, radiocarbon dates cluster at 4050 14 C ka BP, whereas OSL ages are in stratigraphic order from 11ka to 176ka. Because of the self-consistency of the quartz OSL ages, the stratigraphic agreement in the three cores, and the clustering of the radiocarbon dates, we suggest that the quartz OSL ages are more reliable with respect to dating the samples from the south Bohai Sea. Finally, the four marine strata identified in the south Bohai Sea are likely to have formed during the Holocene, Marine Isotopic Stage (MIS) 35, MIS 6 and probably MIS 7, respectively.