大兴安岭中段晚更新世炭质层的发现及地质意义

大兴安岭中段莫克河地区发现一层位于玄武岩下部烘烤成因的炭质层,经加速器质谱测年技术(AMS)14C测定,该炭质层的年龄为(41 925±340)a BP,表明其形成时代为晚更新世。由此可以确定此期火山喷发为晚更新世,而非前人认为的渐新世;依据炭质层所在地质剖面,反演莫克河地区晚更新世后的火山活动过程,将大兴安岭地区新生代火山活动分为新近纪中期和第四纪晚期2期。该炭质层年龄的确定为大兴安岭中段晚更新世以来气候、环境变迁、大兴安岭隆升史等科学研究提供了直接证据。

Discovery and Geological Significance of Late Pleistocene Carbonaceous Layer in the Central Daxing’an Mountains

A carbonaceous layer of baked origin was found recently to underlie the basalt of Moke River region in the central Daxing’an Mountains.By the measurement of accelerator mass spectrometry techniques(AMS)14C,the age of the carbonaceous layer is(41 925±340) a BP.It shows that its formation time was Late Pleistocene.Therefore,we can put a limit to the eruption time of volcanic breccia and basalt.It must be after the Late Pleistocene,rather than Oligocene.Based on the geological profile hosting the carbonaceous layer,the Cenozoic volcanism of the Daxing’an Mountains region can be divided into two periods,the Middle Neogene and the Late Quaternary.The age of the carbonaceous layer provides direct evidence for understanding the volcanic eruption,regional uplift,climate change and so on in the area.