山西柳林孙家沟组孢粉植物群

PALYNOFLORA FROM THE SUNJIAGOU FORMATION IN LIULIN COUNTY, SHANXI PROVINCE

记述山西晚二叠世晚期孙家沟组的丰富孢粉植物群 ,计有 5 7属 10 9种 (包括相似种和未定种 ) ,讨论孢粉植物群的性质 :以西欧镁灰岩组分子为主体 ,并有相当数量的安加拉 亚安加拉 (如新疆北部 )成分参与 ,还有少量华夏植物群的残留分子。

The Shihchienfeng Group with a maximum thickness more than 1 000 m dominated by “barren” red beds of basically terrestrial origin is widely cropping out in North China and consists of three formations, namely the Sunjiagou, Liujiagou and Heshanggou formations in ascending order (Liu and Liu, 1984). The age of this group had been a subject in much dispute before seventies (Li, 1963). Mainly based on palaeobotanical and palynological studies made in seventies to eighties, Chinese geologists have generally been in agreement with the opinion that the Sunjiagou Formation is late Late Permian and the Liujiaggou and Heshanggou formations are Early Triassic (Induan and Olenic) in age, and the former Shihchienfeng “Series” (or Formation s.s.) with the stratotype at Xishan of Taiyuan in Shanxi is largely equivalent to the Sunjiaggou Formation. In addition to the important discoveries of macrofossil plants from the Lower Triassic published in a series of papers from 1978 to 1990 by Wang Zhi qian and his co workers, marked progress has also been made in regard to macrofossil plants from the Sunjiagou Formation by Wang Zhi qian and Wang Li xin (1987). The spore pollen assemblage of the Sunjiagou Formation was first reported from the locality Lishi, Shanxi by Qu Li fan (1980) who dated it as late Late Permian. This conclusion was strengthened subsequently from palynological studies made by Ouyang Shu and Wang Rennong (1985), Wu Jian zhuan (1995), and Wang Rong (1987) from the same formation in Henan and Anhui provinces. In this study, 33 samples collected from the Sunjiagou Formation in different localities of Shanxi Province were selected for maceration and it has proven that only 6 samples from the Liulin County are palyniferous. Well preserved and highly diverse spores and pollen are mainly found in dark grey mudstones of the middle upper part of the Sunjiagou Formation, a section exposed from Liulin in Shanxi to Zhangjiayang in Shaanxi with a thickness of 197 m (see Wang and Wang, 1987). Totally about 109 species referred to 57 genera have been identified (see that listed in Chinese) and partly illustrated (pl. I-III). The spore pollen assemblage is characterized by the low percentage (8.3%—14% of the total) of pteridophytic spores such as Calamospora pallida, Cyclogranisporites micaceus, Apiculatisporis parvispinosus, Apiculatasporites perirugosus, Verrucosisporites sinensis, Neoraistrickia cf. irregularis, Polycingulatisporites sp. and Punctatosporites minutus, and by the dominance of gymnospermous pollen (about 84.3%—89% of the total) , with high percentages of bisaccate and non saccate Striatiti ( 43.6% —60.1%) including a number of stratigraphically important species such as Lueckisporites virkkiae, Scutasporites xinjiangensis, Protohaploxypinus microcorpus, P. dvinensis, P. samoilovichiae, Striatoabieites brickii, S. duivenii, Vittatina striata, V. vittifera, Crustaesporites globosus , and bisaccate non Striatiti (23%—40.5%) such as Gardenasporites heisseli, Falcisporites zapfei, Jugasporites schaubergeroides, Klausipollenites schaubergeri, Platysaccus papilionis, P. radialis , and Alisporites parvus. Monosaccites are only represented by a few species of Potonieisporites, Florinites and Cordaitina. It deserves of mention that among the spores, individuals of Paleophytic lycopods (including lepidophytes), viz. Lycospora, Densosporites and Crassispora occur as relics; and on the other hand, a few morphologically with an aspect of the Mesophyte appeared ( Dictyophillidites, Lundbladispora, Kraeuselisporites and Discisporites ). The characteristics of the assemblage are quite comparable to those known from the Sunjiagou Formation s.s. in Henan and Anhui provinces (see Table Ⅰ in Chinese text). However, in the latter assemblages occur such species as Punctatisporites palmipedites, Gulisporites cf. cochlearius, Waltzispora sp., Knoxisporites cf. instarrotulae, Patellisporites cf. meishanensis, Tripartites cristatus a