江西清江盆地临江组非海相腹足类化石及时代讨论

NONMARINE GASTROPOD FOSSILS FROM LINJIANG FORMATION (EOCENE) OF QINGJIANG BASIN, JIANGXI, CHINA

一、概述华南地区始新世陆相地层发育,腹足类化石极其丰富,搞清其分布、性质、组合特点及古生态对了解整个华南地区中、新生代区域地质发展、构造运动、沉积环境的演替以及寻找沉积矿产等都有很大意义。笔者对江西清江盆地临江组进行了生物地层和岩石学的工作。初步描述了腹足类化石24属、29种,其中包括1新属、7新种。按照腹足类化石产出层位和分布规律,初步建立了1个腹足类组合和3个亚组合,根据腹足类动物群的性质和组合特点,进行了一些生物地层的对比工作。综合介形类、轮藻、孢粉、鱼、植物的研究。

The gastropod fossils described in this paper were collected from the Linjiang Formation in .Jiangxi, with 29 species belonging to 24 genera (including 1 new genus and 7 new species). In lithological characters and faunal assemblages, the Linjiang Formation may be divided into four members, with only three members, actually occurring on the surface section. The lower metuber is mainly composed of purplish-red massive mudstone and greyish white fine-grained calcareous conglomerates, the middle member comprises yellow sandstone, greyish green calcareous mudstone and dark grey shale containing pyrites, while the upper member consists of grey sandstone and siltstone, dark grey and greyish green mudstone, and shale. The fossil gastropods are well-preserved and quite abundant, mostly found in Members 2—3 of the Linjiang Formation. Among them, some genera and species are widely distributed in many parts of China,also with some native forms. Based on sedimentary characters and faunal assemblages, the fossil gastropods of the Linjiang Formation belong to 1 assemblage including 3subassemblages. In:comparison with the fossils of other regions, the writer has come to the conclusion that the Linjiang Formation might belong to the earlymiddle Eocene in age. Description of new genus and species Genus Amnicola Could et Haldeman, 1841 Amnicola zhangshuensis sp. nov. (Pl. Ⅰ, figs. 1—3) Shell small, round-ovate, with 4—5 whorls. Spire low, conical. Body whorl nearly round. Umbilicus with fissure. Aperture pyriform, ornamented with 1—2 growth lines proximally. Discussion This ,mew species resembles Amnicola xigangensis Yu et Zhang from the Baoyue Formation of Eocene, Sanshui Basin, Guangdong, in having round-ovate shell, low spire with roundovate last whorl, pyriform aperture, etc. but can be distinguished from the latter by the round and oblique aperture, and the higher spire. Genus Gangetia Ancey, 1890 Gangetia gibba sp, nov. (Pl.Ⅰ, figs. 4, 5) Shell small, ovate-conical, with 4—5 whorls. Spire about 1/3 as high as shell. All whorls increasing slowly and regularly. Suture depr.essed. Last whorl inflated. Aperture ovate; umbilicus with fissure. Ventral sides of the shell ornamented with fine growth lines. Genus Stenothyra Benson, 1856 Stenothyra qingjiangensis sp. nov. (Pl.Ⅰ, figs. 6, 7) Shell small, conical-ovate in shape, composed of 4 whorls. Spire conical and medially elevated. Apex small and sharp; suture clearly shown. Body whorl inflated and high. Umbilicus absent. Aperture small and subround. Genus Bithynia Leach, 1818 Bithynia yuanshuiensis sp. nov. (Pl.Ⅰ, figs. 8—10) Shell small, conical or long-ovate, with 3 to 4.5 whorls. Spire low, wide-conical. Apical angle 70°—75°All whorls increasing regularly and slowly, with surface round and smooth. Suture deep and narrow. Body whorl extremely inflatedUmbilicus small or with fissure. Aperture ovateround or pyriform. Discussion This new species resembles Bithynia nysti Boissy (Deshayes, 1864, p. 498, p1.35, fig. 31—33) in the feature of apertural view, but the latter differs from the former in the round aperture and the low spire. Genus Physa Draparnaud, 1801 Physa renaria sp. nov. (Pl.Ⅱ, figs. 4—6) Shell small, ovate, sinistral. Spire low. Whorls increasing slowly and regularly, Apex obtuse. Suture deep and oblique. Body whorl appearing extremely inflated. Aperture in nephaoid form, more than half as high as shell. Umbilicus absent. Shell surface smooth, with only fine growth lines on the last whorl. Genus Succinea Draparnaud, 1801 Succinea obliquovata sp. nov. (Pl. Ⅰ, figs. 12—15) Shell large, long oblique-ovate in shape, composed of 3.5 whorls. Aperture small and sharp. Spire very low. Protoconch small and smooth. Suture slightly depressed. Body whorl increasing rapidly, about 9/10 as high as Shell. Aperture showing a long-ovate form, very large. Umbilical area depressed. Shell surface ornamented with spiral lines. Subclass Pulmonata Order Stylommatophora Family Pupilidae Genus Linfiangella gen. nov. Type species Linjiangella peregrina genet sp. nov. Diagnosis, Shell small in size, cylindric orovate-cylindric. Spire low, slightly elevated. Whorls more than 4 in number, increasing slowly and regularly. Apical whorl being protoconch, smooth and small. Two whorls in early stage growing slowly and regularly. Upper side of the last whorl but one with flat periphery. Last Whorl increasing quickly, more than half as the shell. Umbilicus absent. Aperture small, ovately rounded, without teeth. Surface ornamented with fine and spiral lines. Remarks The new genus is similar to Pupoides L. Pgeigger (1854) in the overall shell shape, but it can be distinguished by the cylindric or subcylindric shell, apical depression and cylindric last whole. Distribution Eocene, China. Linjiangella peregrina sp. nov. (Pl. Ⅱ, figs. 7—15) Shell very small in size, cylindric or ovately cylindric, with 4 whorls. Apex obtuse conical. Suture depressed and slightly inclined. Body whorl uninflated. Aperture ovate-round, about 1/3 as high as shell, without teeth. Umbilicus absent.