Olistostromes Discovered in the Halahuogete Formation, Bayan Obo Group and Its Geological Significance
详细信息
- 责任者：Zhang Xing (School of Geosciences ; China University of Petroleum ; Qingdao 266580 ; China) ; Lü Hongbo
- 刊名：Geological Review
- 出版年：2013
- 卷期：59(6)
- 关键词：滑塌构造 ; slump structure ; 堆积体 ; accumulation body ; 内蒙古 ; Inner Mongolia
- 页码：p.1199-1206
- 图表：4 illus., 37 refs.
- 分类号：0803
- issnNo：ISSN0371-5736
- isbnNo：CN11-1952/P
摘要
The carbonate olistostromes found in the Upper Member of the Halahuogete Formation in the Bayan Obo Group were recognized in the field to the northwest of Bayan Obo Deposit,Inner Mongolia. We focus on the research of the two olistostrome outcrops in the field belong to the same horizon. The lithology of the entire olistostrome is monomictic,with chaotic internal structures,without showing the original sedimentary beddings.According to the data collecting in the field and thin sections,there are two major rock types: the dark-gray laminated carbonaceous micrite,which represents the autochthonous deposition,and sallow dolostone olistolith.There are a lot of sallow dolostone blocks with different shapes and sizes distributed in the dark-gray laminated carbonaceous micrite. The largest lenticular dolostone slump block is 27m in length,and 5. 8m in width. The attitude of the dark-gray laminated carbonaceous micrite layers is basically stable,north-dipping with steep angle.We have recognized some soft-sediment deformation structures from the outcrop near the contact interface of the autochthonous limestone and the olistostrome. The dolostone slump blocks do not show the sharp corners,and both ends of the large olistolith are obviously necking,indicating a soft or semi-solidified state during transportation and deposition. The olistoliths in different autochthonous sedimentary beds reveal at least several slump events in this outcrop. We believe that the olistostrome should be deposited at the bottom of a hemipelagic-pelagic ocean basin adjacent to the margin of carbonate platform where the dolostone was formed first in the shallow water and then cut and moved away by slumps. Seismic activities may be the major trigger factor. In addition,the olistostromes discovered in Bayan Obo Group suggest that when Bayan Obo Group and Sailinhudong Group deposited,they had similar tectonic environment and paleogeography,It provides new evidence that Bayan Obo Group is equal to Sailinhudong Group( both early Paleozoic).
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