山西柳林石炭一二叠系孢粉的发现——兼论炭化孢粉的研究

DISCOVERY OF PERMO-CARBONIFEROUS MIOSPORESIN LIULIN COUNTY OF SHANXI, CHINA WITH DISCUSSION ON STUDIES OF CARBONIZED MIOSPORES

以山西柳林两块有机质已炭化的孢粉样品为例,讨论了该类型样品从浸解提取、鉴定到时代确定的全部过程.

Nonmarine Late Paleozoic coal-bearing strata are well developed in Shanxi. The study on Permo-Carboniferous biostratigraphy in this classic area is of significance to the study of relevant strata in North China proper. For a long time, however, palynologically little has been known in South Shanxi, especially in the area below 38°north latitude due to poor preservation. Fortunately, some palynomorphs described in this paper have been separated from two carbonized samples collected from the Sanchuanhe Valley, southwestern Shanxi (about 37°30′north latitude) through the following maceration procedure (without using oxides): heavy liquid→slide. Among the taxa recognized were 26 species assigned to 18 genera (including 13 known species, 11 spp. and 1 new combination) from sample Lxin-32B (Pl. I, figs. 1-37b; Pl. II, figs. 1-13) and 10 species ascribed to 5 genera (including 6 known species, 3 spp. and 1 new species) from sample Lb-P_(1X)28 (Pl. II, figs. 14a 37). The former palynological record indicates an age of Late Carboniferous (Taiyuan Formation), and the latter of late Early Permian (Lower Shihhotse Formation) as com pared with those known from other areas of North China. This conclusion is also supported by associated faunal and floral evidence. Besides, this paper also makes a discussion on how to distinguish genuine features from false ones which occur on the surface of carbonized palynomorphs as secondary characters. These secondary features may be briefly summarized as follows: 1) Pseudo-fovea, loosely distributed, and tran ular or rhombic transparent in form in or on the exine of miospore due to mineralization; 2) Pseu (o-reticulation, closely distributed, and polygonal (mainly tetragonal and hexagonal) transparent in form due to mineralization,appearing as a reticulate pattern under light microscope. The lumina are actually transparent minerals or their impression, and the rest of exine shows muri-like ornamentation (Text-fig. 3, pl. I, figs. 24, 28). The false features may be recognized by its characteristica outline of lumina. 3). Pseudo-projections, which may be subdivided into two types according to their origin: a. uneven surface resulting from sedimentary process or maceration, usually with occurlence of darker punctae or grana and even verrucae; b. irregular projections formed by outer residual materials sticking to the surface of palynomorphs. 4) Concentration, with the miospores often appearing in smaller size than they should be after the process of carbonization. However, we have to get as much reliable information as possible, so that a precise conclusion could be made. Description of miospore species Genus Vesiculatisporites Gao, 1984 Vesiculatisporites triangularis sp. nov. (Pl. II, figs. 18-20) Holotype; Pl. II, fig. 18. Description: Amb triangular, with sides traight to slightly convex, and apices truncated to pointed, 41-55 μm in size; holotype 41μm×51μm; Exine moderately thick, slightly thickened equatorially as an incomplete narrow flange with nodulate outline, punctate to laevigate. Trilete rays distinct, with developed ridge or blade-like labra, 3-4 μm high (or wide), extending to equatorial margin. Discussion: The present species is assign d to the genus Vesiculatisporites based on its nodulate flange, and can be distinguished from the species of Gulisporites by its characteristic thickening Occurrence: Lower Shihhotse Formation (Lower Permian), N. China. Genus Gulisporites Imgrund, 1960 Gulisporites graneus (Ishchenko) comb. nov. (Pl. I, fig. 13) Description: Amb triangular, with sides sraight or slightly concave to convex, and apices pointed 37.5 μm×45 μm in size. Trilete rays distinct, with developed thin and ribbon-like labra, extending to equatorial margin. Exine thin, about 1 μm thick, closely covered with microconi and grana. Discussion: Based on its thin and ribbon-like labra, the species is assigned to Gulisporites. The species G. graneus distinguishes itself from other species of Gulisporites by its more or less straight equatorial equilateral triangular outline. Occurrence: Lower Carboniferous, Donets Basin, Russia; Taiyuan Formation (Upper Carboniferous), N. China.