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.