Re-evaluation of the activity of the Thoen Fault in the Lampang Basin, northern Thailand, based on geomorphology and geochronology

• Published in: Earth, planets, and space Vol. 63; no. 9; pp. 975 - 990
• Main Authors: Wiwegwin, Weerachat, Sugiyama, Yuichi, Hisada, Ken-ichiro, Charusiri, Punya
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.01.2011; Terra; Springer Nature B.V
• Subjects: Basins; Cosmochemistry. Extraterrestrial geology; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Exact sciences and technology; Faults; Geology; Geomorphology; Geophysics/Geodesy; Mountains; Movement; Segments; Trenches; Valleys; Far East; Thailand; Asia; Thoen Fault; AMS radiocarbon dating; geomorphic index analysis; Lampang Basin; morphotectonic landforms; normal faulting; Northern Thailand; OSL dating; geomorphology; mountains; dip; slopes; mass spectroscopy; fault scarps; displacements; dating; Height; tectonics; trenches; geochronology; streams; remote sensing; normal faults; landforms; C-14; sinuosity; luminescence; slip; valleys; age; canyons
• ISSN: 1343-8832; 1880-5981
• DOI: 10.5047/eps.2011.06.018

We applied remote sensing techniques and geomorphic index analysis to a study of the NE-SW-striking Thoen Fault, Lampang Basin, northern Thailand. Morphotectonic landforms, formed by normal faulting in the basin, include fault scarps, triangular facets, wine-glass canyons, and a linear mountain front. Along the Thoen Fault, the stream length gradient index records steeper slopes near the mountain front; the index values are possibly related to a normal fault system. Moreover, we obtained low values of the ratio of the valley floor width to valley height (0.44–2.75), and of mountain-front sinuosity (1.11–1.82) along various segments of the fault. These geomorphic indices suggest tectonic activity involving dip-slip displacement on faults. Although the geomorphology and geomorphic indices in the study area indicate active normal faulting, sedimentary units exposed in a trench at Ban Don Fai show no evidence of recent fault movement. In Ban Don Fai trench No. 2, accelerator mass spectrometry radiocarbon (AMS) ages and optically stimulated luminescence (OSL) ages indicate that deposition of the lowest exposed sedimentary unit occurred between 960 and 910 years ago. Therefore, the most recent movement upon the Ban Don Fai segment of the Thoen Fault occurred more than 960 years ago.