陕西彬县地区中侏罗世延安组孢粉植物群及其意义

报道了采自陕西彬县地区中侏罗世延安组的孢粉化石６０属，８３种。经研究表明，陕西彬县地区延安组的孢粉组合是以裸子植物花粉为主，蕨类植物孢子次之。银杏、苏铁类和松柏类花粉在组合中占优势；桫椤科孢子在蕨类中具有较高的含量。根据孢粉组合特征及其对比，延安组的时代应属中侏罗世早期。陕西彬县地区当时的植被是以银杏、苏铁类和松柏类等乔木为主，并伴有桫椤科为主体的树蕨植物及草本植物，古气候应属大陆性亚热带气候。

Middle Jurassic Sporopollen Assemblage from the Yan'an Formation in Binxian County, Shaanxi Province and Its Significance

Abundant spores and pollen grains including 60 genera and 83 species were collected from the Yan'an Formation in Binxian County, Shaanxi Province. In this assemblage gymnospermous pollen grains amounted to 51.2%, among which Cycadopites made up 27.2% and Quadraeculina 7.2%, also including a certain amount of other genera such as Monosulcites, Eucommiidites, Cerebropollenites, Chasmatosporites, Pinuspollenites, Piceaepoltenites, Piceites Podocarpidites, Psophosphaera, Araucaracites, Classopollis, Callialasporites, etc. Pteridophyte spores amounted to 48.8%, among which Cyathidites made up 21.4%; Deltoidospora 9.1% and Duplexisporites 3.1% . Osmundacidites,Granulatisporites, Lycopodiumsporites,Neoraistrickia,Densoisporites, Microreticulatisporites, Undulatisporites, Cibotiumsporites, Gleicheniidites, Concavissimisporites, Cyclogranisporites, etc, each constituted less than 3%. Based on stratigraphical ranges of certain important known species and comparison with those from other regions in China and Western Canada, the sporopollen assemblage of the Yan'an Formation under study may be assigned to Middle Jurassic in age. Its palaeovegetation and palaeoclimatic conditions are also discussed.