SUMMARY

Activity recording of Mường La - Bắc Yên fault zone in Ít Ong, Mường La, Sơn La

based on determination of the shifted Quaternary sediments

Nguyễn Đại Trung, Phạm Thị Thủy, Trần Tân Văn

 

Mường La - Băc Yên fault zone is a zone between Tú Lệ and Sông Đà structural zones, it belongs to the Late Paleozoic - Cenozoic inland basin in the North Việt Nam. Along this zone, in It Ong area (Mường La, Son La), there were expressions of active faults such as hotspring outcrops and earthquakes. By applied geological and geomorphological survey methods for quaternary sediments, it was showed that three terraces exist in this area: The first terrace (gravel, pebbles, grit... consist of polyminerals) is 2-3 m in thickness, 3-7 m in height above Pi Tong stream, and has alluvial origin in the Late Holocene (aQ23); The second terrace (gravel, pebbles, grit, grit... consist of polyminerals) is 3-5 m in thickness, 7-10 m height above Pi Tong and Nậm Păm streams, and has alluvial origin in the Early-Middle Holocene (aQ21-2); The third terrace step (gravel, pebbles, grit... consist of polyminerals) is 5-7 m in thickness, 10-15 m in height above Pi Tong and Nậm Păm streams, and has alluvial and proluvial origin in the Late Pleistocene (apQi3). Two samples of the Pi Tong stream at the second terrace and four samples at the third terrace of the Nậm Păm stream were sampled in 2014, they are silt-sand sediments shifted by fault activities. Using thermoluminescence method, analysis results of age determination showed that Mường La - Băc Yên fault zone has expressions of modem activities from 3,000 to 6,000 years.

Người biên tập: TS. Phan Đông Pha.