Spatial variation in exhumation rates across Ladakh and the Karakoram: New apatite fission track data from the Eastern Karakoram, NW India

Abstract

Characterization of low-temperature cooling histories and associated exhumation rates is critical for deciphering the recent evolution of orogenic regions. However, these may vary significantly over relatively short distances within orogens. It is pertinent therefore to constrain cooling histories and hence exhumation rates across major tectonic boundaries. We report the first apatite fission track ages from the Karakoram Fault Zone in the Eastern Karakoram range, which forms part of the western margin of the Tibetan Plateau. Ten samples, from elevations of 3477-4875 m, have apatite fission track dates from 3.3 ± 0.3 Ma to 7.4 ± 1.1 Ma. The ages correspond to modeled average erosional exhumation rates of 0.67 + 0.27/À0.18 mm/yr across the Eastern Karakoram. The results are consistent with a trend northward from the Indus suture zone, across the Ladakh terrane and into the Karakoram, in which tectonic uplift associated with crustal thickening increases toward the north, raising elevation and promoting glaciation and generation of extreme relief. As a result, erosion and exhumation rates increase south to north. Present-day precipitation on the other hand varies little within the study area and on a larger scale decreases southwest to northeast across this portion of the orogen. The Eastern Karakoram results highlight the diverse patterns of exhumation driven by regional variations in tectonic response to collision along the western margin of Tibet.

Climatic and glacial impact on erosion patterns and sediment provenance in the Himalayan rain shadow, Zanskar River, NW India

“…Structurally below the Tethyan Himalaya and forming the core of the High Himalaya in Zanskar are the exhumed high-grade equivalents of the Neoproterozoic-Ordovician Tethyan Himalaya and late Paleozoic granitic intrusions, collectively referred to as the Greater Himalaya (Dèzes et al, 1999;Honegger, 1983;Horton and Leech, 2013;Pognante et al, 1990;Pognante and Lombardo, 1989;Schlup et al, 2003;Schlup et al, 2011;Searle et al, 1992;Walker et al, 2001). The Greater Himalaya in Zanskar consists of amphibolite to lower granulite facies Neoproterozoic-early Cambrian paragneiss and metapelite (Herren, 1987), Cambro-Ordovician orthogneiss (Frank et al, 1977;Horton et al, 2015;Mehta, 1977;Noble and Searle, 1995;Pognante et al, 1990;Stutz and Thöni, 1987;Walker et al, 1999) and Mississippian-Permian orthogneiss (Honegger et al, 1982;Horton and Leech, 2013;Noble et al, 2001;Spring et al, 1993).…”

“…How erosion is facilitated by climatic processes is less clear farther north in the Himalayan rain shadow, where high topography impedes northward advection of monsoonal moisture onto the Tibetan Plateau. Arid regions north of the Indus River in Ladakh and the Karakorum show exhumation rates scale with tectonically generated topography and glacial cover rather than with precipitation as found along the Himalayan front (Dortch et al, 2011a;Munack et al, 2014;Wallis et al, 2016). Despite this apparent lack of correlation between precipitation and erosion, some observations suggest the Himalayan rain shadow may be especially sensitive to climatic perturbations.…”

“…How the magnitude of these forces and their resultant erosion shape orogens is debated. Many studies argue for strongly linked climate-precipitation and focused erosion (e.g., Beaumont et al, 2001;Clift et al, 2008;Hodges et al, 2004;Kirby and Ouimet, 2011;Thiede et al, 2004) while others favor a decisive solid Earth control (Burbank et al, 2003;Wallis et al, 2016). Constraining the roles of these processes is crucial in quantifying how sedimentation reflects tectonic and climatic conditions.…”

Millennial and centennial variations in zircon U‐Pb ages in the quaternary indus submarine canyon

“…At the largest scale, the uplift and erosion of the different ranges that comprise the source regions of the Indus River began earlier in the north and later towards the south (Wallis, Carter, Phillips, Parsons, & Searle, 2016). The Karakoram represents the ancient active margin of Eurasia prior to collision with the Kohistan island arc and/or India (Krol, Zeitler, Poupeau, & Pecher, 1996;Searle & Tirrul, 1991).…”

The role of strain hardening in the transition from dislocation-mediated to frictional deformation of marbles within the Karakoram Fault Zone, NW India

“…on geothermobarometry of migmatites formed at ~17 Ma. Time constraints are derived from Ar/ 39 Ar and apatite fission track thermochronology (Boutonnet et al, 2012;Wallis et al, 2016b).…”