Full
JIANG Chunwei,born in 2001,postgraduate,is engaged in deep-water sedimentology. E-mail: jcw2209266011@163.com.
Outline
For the problem of unclear evolutionary process of deep-water gravity flow deposition in the first member of Ordovician Lashizhong Formation in northwestern margin of Ordos Basin,the characteristics and evolution are studied on the basis of outcrop data,microscopic observation and grain size analysis,and finally the sedimentary modles are established. The results show that: (1)five lithofacies are developed in the study area,corresponding to horizontal bedding shale facies(F1),massive bedding calcirudite facies(F2),graded bedding fine sandstone facies(F3),parallel bedding fine sandstone to siltstone facies(F4)and small-scale cross-bedding siltstone facies(F5);(2)four deep-water depositional types are identified according to the shapes and stacking styles of sandstones: complex channels deposition,migrating channels depositon,proximal lobes deposition and distal lobes deposition;(3)complex channels,lobes,migrating channels and lobes are developed vertically in sequence;and(4)gravity flow deposition can be divided into two stages. In the first stage,the energy of gravity flow is high,forming the complex channel;With energy attenuation,small-scale lobes are developed. When in the second stage,the gravity flow erupts,which the energy is lower than the gravity flow in the first stage,and migrating channel is developed. As the energy of gravity flow continues to wane,deposition becomes dominant,resulting in a vertical transition form channels to lobes,with proximal lobes and distal lobes sequentially are developing in the depositional system. This study can improve the understanding of the sedimentary evolution law of gravity flow and is helpful to deep-water oil and gas exploration.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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