Features and origin of deep-water debris flow deposits in the Triassic Chang 7 Member, Ordos Basin

被引：0
|
作者：
Zhou X. [1 ,2 ]
He Q. [3 ,4 ]
Liu J. [1 ,2 ]
Li S. [1 ,2 ]
Yang T. [3 ,4 ]
机构：
[1] National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields, Xi'an
[2] Exploration and Development Research Institute of Changqing Oilfield Branch Company Ltd., PetroChina, Xi'an
[3] State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu
[4] Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu
来源：
Oil and Gas Geology | 2021年 / 42卷 / 05期
关键词：
Deepwater gravity flow; Flow transformation; Genesis; Muddy debris flow; Muddy flow; Ordos Basin; Sandy debris flow; Sedimentary characteristics;
D O I：
10.11743/ogg20210505
中图分类号：
学科分类号：
摘要：
The deep-water gravity flow deposits in the 7th member of the Triassic Yanchang Formation (Chang 7 Member), Ordos Basin, are taken as the main research object to investigate the sedimentary characteristics and genesis of different types of subaqueous debris flow deposits. An integration of log data, core observation and analysis, thin section analysis and quantitative statistics, is applied to discuss the features, sedimentary sequences and genetic mechanisms of debris flow deposits. The results show that the deep-water debris flows in the study area mainly consists of 3 types, that is sandy debris flow, muddy debris flow and muddy flow. Deposits of the first type feature massive sandstone with floating argillaceous debris and a single layer thickness of 0.24 m to 1.10 m, averaging 0.55 m. Those of the second type occur either in isolated massive deposition or in massive argillaceous deposition paired with the underlying massive sandstone: the former is rich in floating mudstone tearing debris and deformation structures of soft sediments, while the latter is rich in floating muddy debris and sandy agglomerates with a single layer thickness ranging from 0.21 m to 1.29 m, averaging 0.60 m. The occurrence of the third type resembles the first type, while its former is composed of sandy mudstone or argillaceous sandstone, and its latter has floating argillaceous chips of millimeter scale in laminar, with a single layer thickness ranging from 0.20 m to 0.60 m, averaging 0.30 m. The flow transformation caused by the involvement of environmental water body in the process of high-concentration sandy or muddy sediment transport, is the main reason for the formation of sandy debris flow deposits, isolated massive muddy debris flow deposits, and mud flow deposits. The muddy debris flow deposits paired with the underlying massive sandstone is mainly caused by flow erosion or sand body liquefaction; and the mud flow deposits paired with the underlying massive sandstone may be caused by flow transformation resulted from deceleration and expansion, and differential settlement of clastic particles. © 2021, OIL & GAS GEOLOGY Editorial Board. All right reserved.
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页码：1063 / 1077
页数：14
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