辽西义县组孢粉植物群指示的古气候条件

迄今为止，在辽西北票义县地区的下白垩统义县组二段沉积层中，已发现孢粉化石62属，82种，藻类化石3种。本文对产于不同地点沉积层中的孢粉化石进行了系统研究和总结。根据孢粉母体植物形态和生态特征、生长的气候环境和干湿度环境，对义县组二段的孢粉植物群进行了植被类型、气候带类型和干湿度类型的统计和划分，认为义县组二段沉积时期，其孢粉植被类型为针叶林，所处的气候环境为湿润的亚热带一暖温带。由于植被成分中存在落叶阔叶植物和旱生植物，推测气候环境存在季节性变化，间有干旱一半干旱气候条件。

SPORE-POLLEN FLORA AS THE INDICATOR OF PALEOCLIMATE CONDITION IN THE YIXIAN FORMATION, WESTERN LIAONING PROVINCE

The spore-pollen flora consisting of 82 species in 62 genera and 3 species of fossil algae from the Member 2 of the Early Cretaceous Yixian Formation shows the following characteristics. The coniferous bisaccate pollen ( 76.42? ?4.12%) is the dominant group in this assemblage. The pteridophytic spore ( 3.34? ?4.42%) is lower in frequency. The angiosperm pollen (0-14.74%) are quite few in amount. Bryophytes spore(0-2.88%)has only 2 species, 1 genus. The average percentages of main elements are as follows. The spores of pteridophyta (7.86%)is lower in content, including 24 species, 20 genus. Among them, Lygodiaceae genus Cicatricosisporites (3.59%)is common. Secondly, Osmundacidites( 1.16%), Deltoidospora ( 0.76%), Klukisporites( 0.59%)are frequent. Todisporites, Lycopodiumsporites, Aequitrir -adites, Lygodiumsporites cf. subsimplex, Concavissim -isporites and Leptolepidites are few and rare. The gymnospermous pollen (69.5%) include 32 genus. Among them, the dominant group is palaeoconiferous types of pollen (27.13%) such as Protoconiferus(5.22%), Protopinus(9.45%), Pseud- opicea(12.36%), Piceites(4.65%)and so on. A lot of new types of pollen (20.98%) including Pinuspolleni- tes(6.88%), Picepaepollenites(5.43%), Abietineaep- ollenites(4.5%), Podocarpidites(2.36%), Cedripites(1.92%) are present in this group. The monocolpate types (including Bennettita and Ginkgoaceae) ( 7.43%)include Ginkgoites, Cycadopites, Ginkgocyca -dophytus and Monosulciles. Cheirolepidiaceae genus Classopolliss(2.6%)are common. The other types of pollen associated with arid climate are Ephedripites( 0.41%), Gnetaceae(0.53%) and Jugella(0.84%). Besides, Perinopollenites(6.77%), Psophosphaera( 3.45%), Taxodiaceaepollenites, Jiaohepollis, Quadraculina are low in number. Early angiosperms pollen (1.83%) occur but quite rarely. They are main noncolporate types. The second are anaulcerate types and a few original tricolpape. Based on ecological characteristic, climate and humidity condition for the vegetation type of the sporo-pollen from the Yixian Fm.(Member 2), the palaeovegetation types have been reconstructed. The result shows that needle leaf element is totally about 68.75%, evergreen latifoliate element is 2.07%, defoliate latifoliate element is 7.15%, scrub are 1.47%, herbage is 7.11%. The aciculisilvae possess a highest percentage in the vegetation type. The tropic type is 9.56%, sub-tropic-warm-temperate type is 8.65%, temperate type is 71.06%, eurythermy type is 4.82%. The xerophylous element is 5.04%, mesophyta element is 86.73%, hygrophilous element is 7.72%. According to above characteristics, it is suggested that the spore-pollen flora of Yixian Fm. Member 2 lived under a humid subtropical to warm-temperate climate condition with typical aciculisilvae. Due to the defoliate latifoliate plants and xerophylous plants occuring with a certain amount in this flora, it is probable that climate condition is seasonal, xeric or semi-arid.