Abstract A special soft-sediment deformation structure(SSDS),which looks very similar to the disk structure,was discovered in the Lower Cretaceous in the northern Ordos Basin. It mainly occurs in the roadside outcrops along the National Highway G109 from the Ordos City to Hangjinqi(over 100,km). It is a set of yellow-brown or gray-white medium-thick layered conglomerate or sandy conglomerate.Due to the concave-down shape in the vertical section,it is called “dish-like structure”here. Generally,it has the following features: (1)The scale is usually large. A small dish-like structure is about 1-3,m wide,and 0.5~1.5,m high;while a large one is about 5~6,m wide,with a maximum of nearly 10,m wide,and mostly 1~1.5,m high,some can be even 2,m high; (2)The edge tilting angle differs among 45°~90°,even reverses;(3)Laterally,the space among different dish-like structures is filled with liquefied sediments caused by escape water discharge,and shows a funnel or an inverse triangle shape in a vertical section;(4)The long axes of gravels along a dish-like structure edge tend to beparallelto the flow direction;(5)It is often associated with sandstone vein,liquefied vein,soft-deformation bedding,or soft-deformation fold,etc.;(6)Its bottom is mostly deposited with a lacustrine brownish red mudstone or sandy mudstone,which is normally massive and fragile due to liquefaction and flow activity.Based on the above-mentioned features,it is thought that the dish-like structure was formed by escape water,which was caused by intensive earthquake of magnitude of 8 or even 9-10. This earthquake is possibly related to the strong tectonic movements during the Mesozoic in the northern Ordos Basin.
Fund:Financially supported by the National Science Foundation of China(No.41572088)
About author: About the first author Zhong Jianhua,born in 1957,is a professor and Ph.D. supervisor of China University of Petroleum(East China). He is engaged in sedimentary structure. E-mail: 957576033@qq.com.About the corresponding author Ni Liangtian,born in 1985,is a Ph.D. candidate of China University of Petroleum(East China). He is engaged in and unconventional oil and gas. E-mail: 382938098@qq.com.
Cite this article:
. Discovery of large-scale dish-like structures of the Lower Cretaceous in Ordos Basin and its geological significance[J]. JOPC, 2017, 19(1): 73-88.
. Discovery of large-scale dish-like structures of the Lower Cretaceous in Ordos Basin and its geological significance[J]. JOPC, 2017, 19(1): 73-88.
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