| 关于间歇性涨缩湖盆沉积作用的几点认识(主要以柴达木盆地早第三纪沉积为例) |
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| 引用本文： | 邓宏文,钱凯.关于间歇性涨缩湖盆沉积作用的几点认识(主要以柴达木盆地早第三纪沉积为例)[J].沉积学报,1987,5(2):91-102. |
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| 作者姓名： | 邓宏文 钱凯 |
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| 作者单位： | 1.武汉地质学院北京研究生部; |
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| 摘 要： | 以柴达木盆地第三系为例,介绍了形成间歇性涨缩湖盆的构造、地形和气候条件。论述了盆地的沉积作用和沉积体系,着重指出陡坡以交互进积作用和洪积-潮积体系为特征,次陡坡以过速加积作用和非常规三角洲为特征,也简述了缓坡正常侧向加积作用及常规三角洲体系。笔者认为,陡坡洪积-湖积体系中的砂砾岩和次陡坡非常规三角洲相砂岩体是油气勘探的主要目标。
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| 关 键 词： | 涨缩湖盆 沉积作用 沉积体系 油气勘探 |
| 收稿时间： | 1985-02-24 |
SOME KNOWLEDGE ON THE SEDIMENTATION OF INTERMITTENTLY-EXPANDING-AND-SHRINKING LAKE BASIN-TAKING OLIGOCENE SEDIMENTS OF QAIDAM BASIN AS EXAMPLE |
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| Institution: | 1.Beijing graduate school of Wuhan Geology Institute;2.Geological Research Institute of Shengli Oilfield |
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| Abstract: | In early Oligocene, the depositional environment of Qaidam Basin had its own features. The basin was in a semiarid climatic zone and surrounded by mountains. On the northwest it was bounded by the Aerjing mountain with a steeper slope; on the northweast by the Qilian mountain with a gentle slope; on the south by The Kunlun mountain, where the basin slope was between the two above. within the basin, Sub-basinal fault and trough with different depth developed on the base- ment of gentle-slope depression Basically, the basin was a closed drainage basin, in which the lacustrine waterbody had a relatively high salinity and the lake boundary changed greatly, the expanding and shrinking of the water body was obvious. During the period of the lowest water level; The lake covered an area in accordance with that of the deep part of the subbasinal fault, while during the period of lake water expanding, water could submerge not only the other part of the subbasinal fault but also the gentle slope region, especially in the gentle-slope depression water body would cover a much larger area with slightly rising of water level.So in the area between maximal and minimal extents of the lake water, an expanding lake basin, lacking waterbody at intervals, was finally formed. Studying the strata formed in such environments ( mainly the lower part of Lower Gan Caigou Formation of Oligocene but its upper part involved occasionally in the marginal area ) , we find that the sedimentation of this kind of lake basins has the following characteristics: In steep slope area, the gradient is high, the peak period of water input and expansion is in accordance with that of sediment input, the progradation of both shorewards lacustrine deposits and lakewards terrigenous sediments is vertically great, sediments is thickening more quickly than those in other areas at the same time, so alternate-progradation is very active. Diluvial-lacustrine depositional system is well developed. Clastic rock bodies can be divided into two kinds of assemblages: diluvial fan-lacustrine beach and diluvial fan-sudaquatic diluvial fan. The latter may be easily mistaken for the Gilbert delta, the distinction is that the topset of subaquatic fan is lacustrine deposits and the alternate-progradation structures are well developed. In sub-steep slops, affeced by overfast velocity and aggradation of flow as well as intermittently expanding and shrinking of the lake area, hidden-bedding sandstones and conglomerates which are mainly deposited in the expanding lake area are well-developed. The framework of sedimentary system mainly consists of conglomerate and sandstone bodies of diluvial fans, mainstream channel of river and unconventional deltaic facies. According to the change of lake water body, unconventional delta can be devided into three types, i. e. drying up, expanding and interactive. In the extensive gentle slope area, meander stream channels develop very well in the fluvial deltaic system. Since streams are far away from their sources, well-sorted thick sandstone bodies can be formed. Among the above mentioned sandstone and conglomeratic bodies, those of steep slopes and sub-steep slopes are near the source area of oil and gas generation so they are the preferable targets for oil and gas exploration. Sandstone bodies of unconventional delta are easily sealed and often filled with pore fluids with abnormal high pressure, which is favourable for preserving primary pores and forming secondary pores. Even burried in great depth, they still have enough spaces for preserving oil and gas, So they are more important for petroleum exploration. |
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