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Holocene internal shortening within the northwest Sub‐Himalaya: Out‐of‐sequence faulting of the Jwalamukhi Thrust, India
Author(s) -
Dey Saptarshi,
Thiede Rasmus C.,
Schildgen Taylor F.,
Wittmann Hella,
Bookhagen Bodo,
Scherler Dirk,
Strecker Manfred R.
Publication year - 2016
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2015tc004002
Subject(s) - geology , holocene , aggradation , pleistocene , fluvial , river terraces , geomorphology , terrace (agriculture) , paleontology , structural basin , archaeology , history
The southernmost thrust of the Himalayan orogenic wedge that separates the foreland from the orogen, the Main Frontal Thrust, is thought to accommodate most of the ongoing crustal shortening in the Sub‐Himalaya. Steepened longitudinal river profile segments, terrace offsets, and back‐tilted fluvial terraces within the Kangra reentrant of the NW Sub‐Himalaya suggest Holocene activity of the Jwalamukhi Thrust (JMT) and other thrust faults that may be associated with strain partitioning along the toe of the Himalayan wedge. To assess the shortening accommodated by the JMT, we combine morphometric terrain analyses with in situ 10 Be‐based surface‐exposure dating of the deformed terraces. Incision into upper Pleistocene sediments within the Kangra Basin created two late Pleistocene terrace levels (T1 and T2). Subsequent early Holocene aggradation shortly before ~10 ka was followed by episodic reincision, which created four cut‐and‐fill terrace levels, the oldest of which (T3) was formed at 10.1 ± 0.9 ka. A vertical offset of 44 ± 5 m of terrace T3 across the JMT indicates a shortening rate of 5.6 ± 0.8 to 7.5 ± 1.1 mm a −1 over the last ~10 ka. This result suggests that thrusting along the JMT accommodates 40–60% of the total Sub‐Himalayan shortening in the Kangra reentrant over the Holocene. We speculate that this out‐of‐sequence shortening may have been triggered or at least enhanced by late Pleistocene and Holocene erosion of sediments from the Kangra Basin.