【摘要】 本文研究的材料采自辽河油田兴253井,华北任丘油田任102井和中原油田卫51井下第三系沙河街组一段。经分析处理观察,发现沙河街组一段含有较多的颗石藻类化石,但属种单调,仅见有1新种Reticulofenestra bohaiensis sp.nov.和1未定种Coccolithus? sp.。颗石藻化石在沙河街组一段的出现,意味着当时沉积盆地曾经同海水沟通。本文对化石颗石藻类的研究方法,尤其供光学显微镜和扫描电子显微镜观察的同一标本的制备技术作了较详细的介绍。更多还原

【Abstract】 Although abundant Tertiary fossils were reported from the Bohai Basin, only a few papers have been written on nannofossils. This paper deals with the nannofossils found from the Oligocene Shahejie-Ⅰ Member of the boreholes situated in the Liaohe, Renqiu and Zhongyuan Oil Fields, where the sediments are characterized by fine laminated calcareous shale with alternating white and dark layers. The white layers are extremely rich in nannofossils with a monospecific assemblage of Reticulofenestra bohaiensis sp. nov. and Coccolithus? sp. which indicate an abnormal marine condition. The discovery of nannofossils in these sediments has provided reliable data indicative of the ingression of the sea water in the Bohai Basin. Dissolution effects on calcite crystals and on coccoliths by epidiagenesis have been observed in some samples from the Renqiu Oil Field.Order Coccolithales Rood et al., 1971Family Prinsiaceae Hay et Mohler, 1967Genus Reticulofenestra Hay, Mohler et Wade, 1966Type species Reticulofenestra caucasica Hay, Mohler et Wade, 1966Reticulofenestra bohaiensis sp. nov.(P1. Ⅰ, figs. 1—9 P1.Ⅱ figs. 1—3, 5—18)Description Elliptical placoliths small, consisting of two closely spaced shields with serrate margins. Distal shield slightly larger than proximal one; both shields with the same number of nearly radial or slightly dextrogyrate imbricately arranged elements. Sutures between elements apparently radial. Elliptical centre area about one-third of the whole placolith; central opening occupied by grille-plates formed by elements of proximal shield elongated toward centre; one suture distinctly aligned with elliptical major axis in the grille-plate structure. Collar-rim of central opening with serrated margin, distally about 1/3—1/2 as wide as distal shield. Distal shield under cross-polarized light as bright as proximal one. Extincted cross lines strngly dextrogyrate in distal view; major axis of elliptical placolith forming an angle of 45° with the polarization directions.Measurements length 3.6—5.5μm; width 2.6—4.4μm.Remarks The new species differs from Reticulofenestra minuta Roth in having a smaller number of shield elements and in the sutures being radial in arrangement.Distribution Oligocene Shahejie-Ⅰ Member in Bohai Basin, China.Holotype P1. Ⅰ, fig. 1; length 5μm, width 3.7μm; w51-6.Paratype P1. Ⅰ, fig. 2; P1. Ⅱ, figs. 5—8.Depositary of specimens Scientific Research Institute of Petroleum Explora tion and Development, Beijing, China.更多还原