AMS^(14)C测年揭示的渤海湾沿海低地第Ⅱ海相层年龄(Ⅱ)

The age of the second marine layer in coastal lowland of Bohai Bay revealed by AMS^(14)C dating method(Ⅱ)

在初步获得渤海湾海河南部沿海低地第Ⅱ海相层年龄大于43.5ka BP的基础上,在沧州北部和海河北部的沿海低地又利用6个新的机械钻孔岩心,建立了2条垂直于现代岸线的长剖面。根据沉积物岩性和有孔虫查明了第Ⅱ海侵层在剖面中的空间分布,并获得一组新的AMS^(14)C年龄数据。结果显示,在第Ⅱ海相层中新获得的9个AMS^(14)C年龄同样均大于43.5ka BP。至此,渤海湾3条垂直现代岸线剖面10个钻孔的第Ⅱ海相层的21个AMS^(14)C年龄均大于43.5ka BP,进一步证实了普遍发育于渤海湾沿海低地的第Ⅱ海相层形成于MIS 3阶段早期或MIS 5阶段,而不是前人认为的23~39ka BP。

Preliminary result has indicated that the age of the second marine layer in the southern coastal lowland of Bohai Bay is 〉 43.5ka BP. Recently’ six boreholes have been drilled in the coastal lowlands north of Cangzhou and north of the Haihe River’ and two new profiles perpendicular to the moder^i shoreline were then established. Combined with the lithostratigraphy’ foraminiferal as-semblages and AMS 14C dating results’ the second marine layer in these cores has been identified spatio-temporarily. The dating re-sults of 9 samples collected from the second marine layer show that the ages are all older than 43.5ka BP. Up till now’ 21 AMS 14C ag-es collected from the second marine layer in 10 boreholes’ given by the authors’ indicate that the widely distributed second marine layer was formed in the early MIS 3 or MIS 5 stages rather than 23？ 39ka BP as previously believed.