青海省中西部洪水川群孢粉组合及其时代

EARLY TRIASSIC SPORE-POLLEN ASSEMBLAGES FROM THE HONGSHUICHUAN GROUP OF CENTRAL-WESTERN QINGHAI

命名剖面位于青海省中东部(玛多、都蓝)的"洪水川群",实际上可延伸到西部格尔木以西、昆仑山以北地区,本文从此地原划归二叠纪与侏罗纪的两套不同时代的地层单元中,首次发现孢粉化石组合,皆以Calamospora,Limatulasporites,Lundbladispora,Aratrisporites,Taeniaesporites,Tubermonocolpites等广泛分布为主要特征;共计孢粉88属105种(型),其中包括12新种;疑源类14属16种,包括3新种。组合中蕨类植物孢子占总组合的平均含量43.98%,裸子植物花粉占45.81%,疑源类占10.04%。丰富多彩的面貌,显示出与国内外不同相区早三叠世(Induan-Olenekian)孢粉组合类似,当出自相同的地质时代。

The Hongshuichuan Group typically crops out in the Maduo and Dulan counties of central Qinghai,consisting mainly of volcano-clastics and limestones with thick basal conglomerates,it is dated as Early Triassic based on faunal evidence（e.g.from cephalopods）.However,the group actually extends far to the western area of the province and includes two sets of strata,lithologically represented mainly by dark grey muddy siltstones and dark grey sandy shales,previously assigned respectively to the Permian and Jurassic.The present paper deals with abundant and diverse fossil spores and pollen recovered for the first time from these two sets of stratigraphic units,represented by two sections（Fig.1）in a depopulated area far West of the Geermu City,located at ca.36.00—36.40°N×93.00°—93.4°E,to the North of the Deep-Big Fracture—F3.The assemblages are all characte-rized by the constant presence of Calamospora,Li-matulasporites,Lundbladispora,Aratrisporites,Taeniaesporites（=Lunatisporites）and Tubermonocolpites（=Sulcusicystis）,etc..They totally about 106 species（forms）in 89 genera of spores and pollen,including 9 new species;and 15 species in 15 genera of acritarchs,including 3 new species.All are listed and mostly of them illustrated here.As a whole the assemblages contain an average contents of 43.98% cryptogam spores,45.81% gymnospermous pollen and 10.04% acritarchs.