据孢粉分析黑龙江嘉荫地区晚白垩世气候变化对恐龙绝灭的影响

黑龙江省嘉荫地区是中国境内发现恐龙最早的地区,自恐龙化石被发现以来在该区进行过大量的发掘,但对恐龙生活环境和灭绝原因一直没有解释。本研究将产恐龙的晚白垩世地层由下而上划分为永安村组、太平林场组、渔亮子组和富饶组,其中产恐龙化石和大量孢粉化石。孢粉化石由下而上可识别为Polypodiaceaesporites-M onosulcites-Beau-preaidites、Cyathidites-Taxodiaceaepollenites-Aguilapollenites和C lassopollis-Ephedripites-Sphagnum sporites组合。根据含恐龙地层中的孢粉化石组合变化和沉积物特征分析,认为晚白垩世本区总体属湿暖的亚热带气候环境。孢粉化石组合的变化显示当时出现暖湿至干热气候条件的演变。嘉荫群上部渔亮子组中膏岩层和耐高温、抗盐碱的克拉梭粉(C lassopollis)麻黄粉(Ephedripites)组合在短时间内的大量出现,说明晚白垩世末期出现有短暂的干热气候,这种气候的突然转变以及伴随的生态系统的紊乱可能是嘉荫地区恐龙大量死亡的重要原因,但不排除诸如天外星体碰撞地球、大规模火山喷发等引发白垩纪末恐龙全球灭绝的因素,后者更可能是引起气候变化的直接因素。

Influence of Late Cretaceous Climate Change to Extinction of Dinosaurs in Jiayin Area of Heilongjiang, Analyzed by Spore and Pollen

The Jiayin area of Heilongjiang Province is the first fossil dinosaur locality in China.Many fossils have been found from this area but lacking reasonable explanation to the living environment and extinction causes of the dinosaurs.The Late Cretaceous dinosaur-bearing strata have been divided in ascending order as the Yong'an,Taipinglinchang,Yuliangzi and Furao formations.The strata contain abundant dinosaurs and sporopollen fossils,and the Polypodiaceaesporites-Monosulcites-Beaupreaidites,Cyathidites-Taxodiaceaepollenites-Aguilapollenites and Classopollis-Ephedripites-Sphagnumsporites assemblages have been recognized.The fossil assemblages and sedimentary records show that the Jiayin area was generally in subtropical climate during Late Cretaceous.The assemblage variation of spore and pollen indicates a change from warm humid to dry hot climates.Abundance of salt-alkaline megatherm Classopollis-Ephedripites assemblage in a limited time illustrates a short duration of dry hot climate by latest Cretaceous.Such extreme climatic change and ecologic overturn are possible causes of the dinosaur extinction in the study area.Other factors,such as asteroid impact and large(volcanic)(eruption) triggering global mass extinction caused the regional climate change.