新疆准噶尔盆地西北缘三叠纪孢粉组合

TRIASSIC SPOROPOLLEN ASSEMBLAGES FROM NORTHWESTERN MARGIN OF JUNGGAR BASIN, XINJIANG

本文对新疆准噶尔盆地西北缘红山咀区拐114井和百口泉区38井的下克拉玛依组、上克拉玛依组、下白碱滩组层段13块样品中所含的孢子花粉进行了系统的分析研究,共获得孢粉77属170种,描述了31种.其中包括1新属21新种。根据孢粉组合特征,详细地讨论了上述地层的时代,认为下克拉玛依组属中三叠世,上克拉玛依组及下白碱滩组属晚三叠世。

The spores and pollen grains under study were discovered from Bai-38 and Guai--114 Wells along the northwestern margin of the Junggar Basin in Xinjiang, stratigraphically ofthe Lower Karamay Formation,Upper Karamay Formation and Lower Baijiantan Formation.Abundant spores and pollen grains have been found,including 170 species in 77 genera amongwhich 31 species(including 21 new species) and 1 new genus are described herein. 1. Sporopollen Assemblage of the Lower Karamay Formation This assemblage consists of 36 genera and 61 species, among which gymnospermouspollen grains amount to 53.6% and pteridophytic spores to 45.8% of the total, with rareReticulatisporites sp. (acritarchs). The spores and pollen grains mainly include Cycadopites(11.2%), Vitreisporites (9.6%),Pityosporites (5.7%), Psophosphaera (5.1%), Inaperturopollenites (7.5%), Aratrisporites (2.5%), Punctatisporites (8%), and Apiculatisporis (4.2%), with small amounts of Chas-matosporites, Prorohaploxypinus, Chordasporites, Striatites, Alispoes, Podocarpidites, Concavisporites, Retusotriletes, Limatulasporites, Osmundacidites, Asseretospora, etc., but with no Lundbladispora and Zebrasporites observed,probably indicating a Middle Triatssic age. 2. Sporopollen Assemblage of the Upper Karamay Formation In Well Bai-38 this assemblage contains 112 species assigned to 58 genera,with pterido-phytic spores amounting to 78% and gymnospermous pollen grains to 22% of the total. InWell Guai-114, approximately 92 species of 50 genera have been found, with more gym-nospermous pollen grains (61.7%) than pteridophytic spores (38.3%). This formation mainly contains such pollen grains and spores as Concavisporites, Dic-tyophyllidites, Asseretospora, Conbaculatisporites, Punctatisporites, Granulatisporites, Todis-porites, Calamospora, Centrifugisporites gen. nov., Osmundacidites, Marattisporites, Ara-trisporites, Cycadopites, Bharadwajapollenites, Chasmstosporites and Vitreisporites, with someimportant elements in its sporopollen assemblage such as Zebrasporites iterscriptus (Thiergart) Klaus, Z. cf. fimbritus Klaus, Verrucosisporites morulae Klaus, Lunzisporites lunzensisBharadwaj et Singh, Lycopodiacidites rudis (Leschik) Li et Shang, Aratrisporites granulatus(Klaus) Playford et Dettmann, A. fischeri (Klaus) Playford et Dettmann, A. parvispinosusLeschik, together with Taeniasporites, Protohaplexyinus, Lueckisporties, Striatopodocarpites,Striapollenites,etc.,and therefore can be regarded as Late Triassic in age. 3. Sporopollen assemblage of the Lower Baijiantan Formation This assemblage contains approximately 35 species in 29 genera,with more gymnosper-mous pollen grains (57.6%) than pteridophytic spores(42.4%). In this assemblage the gymnospermous pollen grains are mainly Cycadopites (16.6%),Vitreisporites, Pityosporites, Pinuspollenites, Piceites latens, Protopicea, Platysaccus, Podocar-pidites, Psophosphaera, etc., the pteridophytic spores are mainly Concavisporites, Deltoidospo-ra, Punctatisporites, Retusotriletes, Osmundacidites, Neoraitrickia, Labrorugaspora, Aeretospora, Aratrisporites, Polycingulatisporites,etc.,all of which (exclusive of Piceites latens, Pinuspollenites cf. tricomposites and Polycingulatisporites sp.) have been found in the Upper Karamay Formation. Because this formation conformably overlies the Upper Karamay Formation and due to the existence of the genus Aratrisporites which is usually taken as an index fossil for the Triassic,particularly for the Upper Triassic in many places over the world, thisformation is assigned to the Late Triassic.