Tectonic unconformity boundary between upper Cambrian and lower-middle Devonian sedimentary rocks in Quang Han commune
- Wednesday - 29/08/2018 12:15
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![Tectonic unconformity boundary between upper Cambrian and lower-middle Devonian sedimentary rocks in Quang Han commune](http://caobanggeopark.com/uploads/news/2018_08/quang-han/quang-han-1.jpg)
The tectonic boundary between thin-bedded yellow grey aleuritic clayish shale at a 220Ð45 bedding to the southwest of Than Sa formation (∈3ts) and thin-bedded dark grey limestone at a 330Ð55 bedding to the northwest of Na Quan formation (D1-D2nq).
The site shows a tectonic boundary – a NW-SE fault more than 100m wide – between shale of Than Sa formation (∈3ts) and limestone of Na Quan formation (D1-D2nq). In addition, there is a gradual upward transition to limestone of Na Dang formation (D2gv-D3frnd), followed by that of Lung Nam formation (C1ln). Again, the contrast between the young to old karst landforms and the denudation-erosion hilly landform on the terrigenous rocks is also of interest. In addition to the significance similar to that of the previous site, this site shows further upward stratigraphic succession.
![quang han 1](http://caobanggeopark.com/cvdc/uploads/news/2018_08/quang-han/quang-han-1.jpg)
Abrupt moderately-bedded dark grey limestone of Na Quan formation
![quang han 2](http://caobanggeopark.com/cvdc/uploads/news/2018_08/quang-han/quang-han-2.jpg)
Kink folds in dark grey thin-bedded limestone of Na Dang formation