江苏北部新元古界贾园组和赵圩组的微古植物群及其地层意义

Micropalaeoflora and Their Stratigraphic Significance in Jiayuan and Zhaowei Formation of North Jiangsu from Neoproterozoic Erathem

对采自江苏北部铜山县新元古界贾园组上部的灰色中厚层砂泥质灰岩、粉砂质灰岩和赵圩组下部的青灰色厚层灰岩中的微古植物群样品 ,进行了以浸解法为主 ,辅以磨片法的研究 ,共发现 14属、19种 ,其中有 1新属、2个新种。研究结果表明 ,贾园组和赵圩组的微古植物群虽属、种较少 ,但化石体的纹饰较复杂、结构明显。就其微古植物组合特征看 ,它与我国北方新元古界的化石组合有较大差别 ,而更近似于我国南方前震旦系的南华系 (扬子系 )上部的微古植物组合 ,地质时限为距今 74 0Ma～ 70 0Ma之间。

The micropalaeoflora collected from the grey middle thick bedded sandy argillaceous limestone and siltaceous limestone which belong to the middle upper portion of the Jiayuan Fm. and the green grey thick bedded limestone which belong to the lower portion of the Zhaowei Fm. of Neoproterozoic in Tongshan county, North Jiangsu are dealt with in the paper. The samples dealt with are mainly collected by the maceration method and assisted by thin section. The micropalaeoflora found are 14 genera, 19 species including 1 new genus, 2 new species, 1 conformis and uncertain species are found in the micropalaeoflora. It is concluded that the micropalaeoflora in Jiayuan and Zhaowei formations are fairly abundant with varied forms, complex in ornament and clear structure. In terms of the characters of micropaleaoflora assemblage, they are different from those of the Neoproterozoic strata in North China, seem to be similar to those of the upper series of the Nanhua(Yangtze) System whose geological time for Jiayuan and Zhaowei formations are 740Ma～700Ma. Descripotion of new genera and new species are briefly given below: Monilinema Yan (gen. Nov.) The name of the genus is derived from Latin monil and Greek nema meaning beads and silk ribbon, respectively. Type species: Monilinema quadratucella Yan(gen. et sp. nov.) Diagnosis:Catenulate filament of algae with is composed of a quantity of the cell. Monostichous, or straight, or slight croaked, unbranching, any one cell body is square, or subsquare, cell wall fairly thick, smooth or slight rough, length of diagonal line of the cell small than 10, brownish yellow to yellowish brown. Comparison:This new genus is similar to Nostocomorpha Sin et Liu in the link way, but it is easily differentiated from the latter cell is the spherical or subspherical in shape. Occurrence:Jiayuan Fm. and Zhaowei Fm. at Tongshan county, Jiangsu province. Monilinema quadratucella Yan (gen. et sp. nov.) (P1.1, fig. 23 25, 28 30) Etymology:From quadrate and cell Latin, referring to the shape of the monocell. Holotype:P1.1, fig.23. Description:Catenulate filament of algae, which is composed of a quantity of the cell. Monostichous, or straight, or slight croaked, unbranching, a cell body is square, or subsquare, cell wall 0 5 1μm in thick. Smooth or slight rough, diagonal line of the cell in square is 3 7 7 5μm. Brownish yellow to yellowish brown. Occurrence:Jiayuan Fm. and Zhouwei Fm. at Tongshan county, Jiangsu province. Margominuscula (Naumova,1960) emend. Sin et Liu,1973 Margominuscula jianyuanensis Yan(sp. nov.) (P1.1, fig.2 4) Holotype:P1.1, Fig.3 Description:Theca rounded or subrounded in outline with diameter 7 5 8 8μm; theca is dense without wrinkles; theca margin thicken similar to thick margin, which is vary in width is 0 5 2 5μm; surface smooth or slightly rough. Brownish yellow to yellowish brown. Occurrence:Zhaowei Fm. at Tongshan county, Jiangsu province.