四川綦江观音桥志留纪微体古植物

SILURIAN MICROFLORA FROM GUANYINQIAO, QIJIANG, SICHUAN

本文所研究的微古植物产于四川綦江观音桥志留纪剖面中的龙马溪组、桥沟组,石牛栏组、韩家店组,共有26属79种。本文只描述其中1个新种Unellium hanjiadianense。通过对微古植物的组合特征分析,揭示出该剖面各组所含藻类繁衍的特点,并根据微古植物组合特征,将龙马溪组、桥沟组、石牛栏组划归Llandoverian(兰多维列阶),韩家店组定为Wenlockian(温洛克阶)。

The microflora described in this paper was collected from the Lower—Middle Silurian rocks at Guanyinqiao, Qijiang, Sichuan. Exposed on the Yangtze Platform, the Guanyinqiao section is located on the Sichuan—Guizhou Highway in Sichuan, 90 km from Qijiang county in Sichuan and 15 km from Tongzi county in Guizhou. In this section, the stratigraphic sequences from old to new, are the Lungmachi, Qiaogou, Shiniulan and Hanchiatien Formations, from which 79 species in 26 genera of microflora have been found. A study on these fossil plants shows that the Lungmachi, Qiaogou and Shiniulan Formations are equivalent to the Llandoverian stage, and the Hanchiatien Formation seems to be of the Wenlockian stage.The Lungmachi Formation contains 23 species of microflora, which belong to 11 genera, namely, Baltisphaeridium, Goniosphaeridium, Leiofusa, Leiosphaeridia, Lophosphaeridium, Micrhystridium, Moyeria, Multiplicicisphaerium, Peteinosphaeridium, Polygonium and Solita. This microfloral assemblage is dominated by the largesized Acanthomorphitae with abundant Sphaeromorphitae and some Netromorphitae.There are 14 species in 10 genera of the microflora in the Qiaogou Formation, namely, Baltisphaeridium, Comasphaeridium, Dactylofusa, Eupoikilofusa, Gorgonisphaeridium, Leiofusa, Leiosphaeridia, Multiplicisphaeridium, Pterospermella and Solita (with some of them extending into the formations mentioned below ). This assemblage is characterized by the abundance of Baltisphaeridium, Multiplicisphaeridium, Dactylofusa, Leiofusa, Pterospermella, etc.In the Shiniulan Formation were found 25 species in 10 genera, namely, Acanthodiacrodium, Baltisphaeridium, Cymatiosphaera, Gorgonisphaeridium, Leiosphaeridfum, Lophospnaerfdium, Micrhystridium, Multiplicisphaeridium and Synsphaeriaium, among which Baltisphaeridium and Cymatiosphaera are dominant, with a small number of Micrhystridium. Present in the Hanchiatien Formation were 39 species in 13 genera, namely, Baltisphaeridium, Cymatiosphaera, Deunffia Elektoriskos, Leiofusa, Leiosphaeridia, Lophosphaeridium, Micrhystridium, Moyeria, Tylotopalla, Unellium and Veryhachium, among which the small-sized Veryhachium and Micrhystridium are prevailing, with quite a few characteristic elements of Baltisphaeridium, Leiosphaeridia, etc.Description of New SpeciesUnellium hanjiadianense sp. nov. (P1. Ⅲ, figs. 5—7)Diagnosis Vesicle pyriform in outline; central body 18×14μ; wall thin, laevigate; 2 orders of processes, one major process tapering, 8—11 μm long and 2.5 μm wide at base, hollow, laevigate, opening into and communicating with vesicle interior; 4—6 minor processes simple, laevigate, tapering off to a sharp point, 3.5—7μm long, and 1.2—2.3μm wide at base, opening into and communicate with vesicle interior.