冀北—辽西地区侏罗—白垩纪之交期的孢粉植物群演替与古气候变化

The Palynoflora Alternation and the Paleoclimate Change at the Turning Time between Late Jurassic and Early Cretaceous in Northern Hebei and Western Liaoning

本文根据冀北—辽西地区侏罗—白垩纪之交期孢粉植物群的地层分布,划分了9个孢粉植物群组合带(自下而上):"桫椤孢-苏铁粉-克拉梭粉"组合带、"克拉梭粉"组合带、"无突肋纹孢-滦平孢-纵肋单沟粉"组合带、"云杉粉-层环孢-无突肋纹孢-膜环弱缝孢"组合带、"云杉粉-无突肋纹孢-凹边瘤面孢"组合带、"辽西孢-刺毛孢-克拉梭粉"组合带、"刺毛孢-有突肋纹孢-无突肋纹孢-三孔孢"组合带、"三角孢-无突肋纹孢-有突肋纹孢"组合带和"无突肋纹孢-克拉梭粉-希指蕨孢-麻黄粉"组合带;重建了该区当时的古气候和古环境,认为中侏罗世时期该区处于温暖湿润气候下的低山丘陵环境,晚侏罗世时期处于干旱气候下的荒原环境,早白垩世早期处于温凉湿润气候下的低山环境,早白垩世中期处于温凉湿润气候下的高山环境,早白垩世晚期处于温暖湿润气候下的低地沼泽环境,早白垩世最晚期处于干热气候下的低地环境。此外,本文还根据该区侏罗—白垩纪之交期生物群演化和更替的特征,提出了"避难所"理论模式。

According to the stratigraphic distribution of the palynoflora at the turning time of the Jurassic-Cretaceous in northern Hebei and western Liaoning, nine sporopollen assemblage zones can be recognized, which are in ascending order of ＂Cyathidites-Cycadopites-Classopollis＂ Assemblage Zone, ＂Classopollis＂ Assemblage Zone, ＂Piceites-Podocarpidites-Schizaeoisporites＂ Assemblage Zone, ＂Cicatricosisporites-Luanpingspora-Jugella＂ Assemblage Zone, ＂Piceaepollenites-Densoisporites -Cicatricosisporites -Aeguitriradites＂ Assemblage Zone, ＂Piceaepollenites-Cicatricosisporites -Concavissimisporites＂ Assemblage Zone, ＂Liaoxisporites-Pilosisporites -Clasopollis＂ Assemblage Zone, ＂Pilosisporites-Appendicisporites-Cicatricosisporites-Triporoletes＂ Assemblage Zone, ＂Deltoidospora _Cicatricosisporites-Appendicisporites＂ Assemblage Zone and ＂Cicatricosisporites-Classopollis -Schizaeoisporites-Ephedripites＂ Assemblage Zone. Based on the sporopollen assemblages, the authors reconstructed the paleoclimate and paleoenvironment of the study area： warm and humid low mountains and hills in Middle Jurassic, arid wastelands in Late Jurassic, cool and damp low mountains in the early stage of Early Cretaceous, cool and damp high mountains in the middle stage of Early Cretaceous, warm and humid low lands and fenlands in the late stage of Early Cretaceous and xerothermic low lands in the latest stage of Early Cretaceous. In addition, this paper proposes a ＂sanctuary＂ model for the biota alternation at the turning time between Late Jurassic and Early Cretaceous.