撞击事件对古环境的影响——来自ODP1144站A孔样品的证据

本文通过对ODP1144站A孔BM界线附近样品中微玻璃陨石的挑选和研究,确定在中更新世曾发生过地外物体撞击地球的灾变事件。样品中浮游有孔虫壳体碳氧同位素的对比研究表明,在微玻璃陨石事件发生的后期,曾发生了浮游有孔虫壳体碳氧同位素组成的变化,表现为^δ13 C值的降低和^δ18 O值的增加。文中还探讨了其形成的原因。

IMPACT EVENTS AND ITS EFFECTS ON PALAEOENVIRONMENT: EVIDENCE FROM ODP SITE 1144 CORE A

The study on microtektites of Ocean Drilling Project(ODP) site 1144 core A around Brunhes/Matuyama boundary indicated the impact event had happened in mid Pleistocene. In this paper we use shell of foraminifera G.sacculifer to determine their C and O isotope compositions. The results indicate that C and O isotope components had changed( ^δ13 C reduced and ^δ18 O ascend) in the late stage of microtektite event. The main reason of changes of C and O isotope components is because a part of target rock can be melted and boil away by huge energy when exterrestrial object shocked the Earth so the oxygen( ^δ18 O) and carbon( ^δ13 C) isotope composition of atmosphere can be transferred and in the mean time a large of clastic debris and shocking dust can be displaced into stratosphere and diffused to the seven seas. These clastic debris and shocking dust can reduce radialization of the sun and result in the temperature and photosynthesis reduced, so biologic acts weakened and amount of CO₂ decreased. In relative to carbon( ^δ13 C) isotope composition,the oxygen( ^δ18 O) isotope composition is ascend.