As a workshop was celebrating the legacy of Paul Tapponnier in Singapore few days ago (on 2018 July 11th), I found interesting to compare our respective 1988 field books. In March 1988 we explored the highly sheared metamorphic rocks of the Ailao-Shan in Yunnan, China. This mountain range hosts the major shear zone that allowed the extrusion of Sundaland (also named Indochina) in the Cenozoic in response to India-Asia collision. Left lateral displacement has been of several hundreds of kilometers along this zone, essentially by ductile shear in the metamorphic rocks.
The two following field-book scans show the same section across a part of the Ailao Shan – Red River shear zone. The first one was drawn by Paul, the second one, in two parts thus little more detailed, is mine. There are some differences in drawing and reporting style, but you'll easily recognize several units and details of the structure. Can we see this as a test of reproducibility while making field observations ?
Below is another section of the shear-zone, several tens of kilometers to the south-east, as also drawn by Paul. Note location of samples (YS nn, YU nn) whose dating was further reported in papers.
I also post an example of field mapping notes over the same area, as drawn by Paul in 1988. The section just above is the one along the road on the left part of the map; it only displays the high-grade metamorphic part of the shear zone which is drawn with orange tones on the map. Note also the traces of the active Red River fault, in red, with oblique motion partitioned on two fault strands: a normal fault bounds the metamorphic core, while a parallel right-lateral strike-slip fault offsets the drainage.
Some related papers, among many others:
- Tapponnier, P., R. Lacassin, P. H. Leloup, U. Schärer, Zhong Dalai, Liu Xiaohan, Ji Shaocheng, Zhang Lianshang, and Zhong Jiayou, The Ailao Shan/red River metamorphic belt: Tertiary left-lateral shear between Indochina and South China, Nature, 343, 431-437, 1990
- Schärer, U., P. Tapponnier, R. Lacassin, P. H. Leloup, Zhong Dalai, and Ji Shaocheng, Intraplate tectonics in Asia: a precise age for large-scale Miocene movement along the Ailao Shan-Red River shear zone, China, Earth Planet. Sci. Lett., 97, 65-77, 1990.
- Lacassin, R., P. H. Leloup, and P. Tapponnier, Bounds on strain in large Tertiary shear zones of SE Asia from boudinage restoration, J. Struct. Geol., 15, 677-692, 1993.
- Leloup, P.H., R. Lacassin, P. Tapponnier, Zhong Dalai, Liu Xiaohan, Zhang Lianshang, Ji Shaocheng, and Phan Trong Trinh, The Ailao Shan-Red River shear zone (Yunnan, China), Tertiary transform boundary of Indochina, Tectonophysics, 251, 3-84, 1995.
