Late Holocene Uplift of the Chihshang segment of the Longitudinal Valley Fault at Fuli, Eastern Taiwan
Brian Thomas Gray
August 2007
Abstract
Uplifted Holocene strath terraces of the Bieh River drainage, eastern Taiwan,
were analyzed in order to determine millennial-scale uplift and horizontal
shortening rates of the Longitudinal Valley fault. Detrital charcoal fragments
collected from three terraces within the Bieh River drainage yield ages between
1395 and 555 cal. yr B.P, suggesting an average uplift rate of 11.3±3.6 mm/yr
for the last 1400 cal. yr B.P. The average horizontal shortening rate of
19.7±9.5 mm/yr was within error of present-day conventional geodetic
measurements, but near the lower limit of the geodetic measurements. This
suggests that present-day horizontal shortening may not reflect the millennial-
scale nature of horizontal shortening across the Chihshang segment of the
Longitudinal Valley fault. Based on the longitudinal profile and several
distinct regional geomorphic features, the Bieh River may be experiencing
differential deformation outside of the main Longitudinal Valley fault zone,
possibly on the Yungfong fault, or unrecognized structures within the Lich
Mélange.
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