【摘要】 <正> 延庆盆地位于北京西北部山区,举世闻名的八达岭北麓,海拔约500米,为一北东向延伸的狭长小盆地,长约40公里,宽约10—15公里;西南端与怀来盆地相连,为桑干河、洋河、妫水河的汇合处,永定河的上游流经此处.解放后兴建的第一座大型水库——官厅水库也座落这里.更多还原

【Abstract】 This paper gives a description of the microfossils (Foraminifera and Ostrac-oda) and the strata from Zhenpin-1 hole (1002.02m. in depth) in the Yanqing Basin, Beijing, as well as their comparison to the neighbouring area (Beijing Plain, Nihewan Basin of Hebei province). The strata are divided into seven mem-bers in ascending order in the present paper:I . 1002.02-724.00m.: The lower part is composed of red clay, yellowish-brown clayey sand with gravel; the upper part is grey-green, brown, brown-grey sandy clay with thin-bedded silt and silty-fine sand. Their ages are considered as Pliocene and they are generally analogous to the lower part of the Nihewen Formation in the Yangyuan-Yuxian Basin, Hebei province.II.724.00-521.26m: Grey-green sandy clay with thin-bedded silty-fine sand and brown clay in the lower part, and with thin-bedded peat in the raiddle part_ The foraminifera fossils Evohtononion shanxiensis Wang were found in the middle-upper part of this member (578.49-582.20m.).III. 521.26-342.65m.: Grey silt and grey sandy clay, interlayered with middl-ing sand, middling fine sand and clay.IV. 342.65-230.11m.: Grey-green sandy clay with grey silty fine sand and small amount of silt.In general, II-IV members correspond to the middle part of the Nihewan Formation of the Yangyuan-Yuxian Basin, Hebei province. Their ages are considered as Early Pleistocene.V. 230.11-42.20m.: Grey, grey-green, yellow-white sandy clay with thin-bedded silt. It belongs to Late Early Pleistocene-Middle Pleistocene.VI. 42.20-14.00m.: Brown sandy clay with peat at the bottom. The age is Late Pleistocene.VII.14.00-0.00m.: Yellow, grey sandy clay and brown clayey sand. lts age is Holocene.The Foraminifera fossils were only found in member II, 578.49-582.20m. in the hole, and they have only one genus and one species, and were temporarily determined as Evolutononion shanxiensis Wang. This species was also found in the Nihewan Formation from Dongyaozitou of Yuxian, Haojiatai of Yangyuan county, Hebei province. At the same time, this strata corresponds to the foraminifera-be-aring strata in the Beijing plain. They are all considered as Early Pleistocene. The lithofacies-paleogeography and the transgression in the Yanqing Basin are also discussed in this paper, and we consider that the Forarainifera discovered in the Yanqing Basin was related to the transgression in Early Pleistocene in Beijing plain. Furthermore, the deposit of the Nihewan Formation in Yangyuan-Yuxian Basin, northwest Hebei province was also influenced by this transgression.更多还原