TY - JOUR A1 - Thiede, Rasmus Christoph A1 - Bookhagen, Bodo A1 - Arrowsmith, J. Ramón A1 - Sobel, Edward A1 - Strecker, Manfred T1 - Climatic control on rapid exhumation along the Southern Himalayan Front N2 - Along the Southern Himalayan Front (SHF), areas with concentrated precipitation coincide with rapid exhumation, as indicated by young mineral cooling ages. Twenty new, young ( < 1-5 Ma) apatite fission track (AFT) ages have been obtained from the Himalayan Crystalline Core along the Sutlej Valley, NW India. The AFT ages correlate with elevation, but show no spatial relationship to tectonic structures, such as the Main Central Thrust or the Southern Tibetan Fault System. Monsoonal precipitation in this region exerts a strong influence on erosional surface processes. Fluvial erosional unloading along the SHF is focused on high mountainous areas, where the orographic barrier forces out > 80% of the annual precipitation. AFT cooling ages reveal a coincidence between rapid erosion and exhumation that is focused in a similar to 50-70-km-wide sector of the Himalaya, rather than encompassing the entire orogen. Assuming simplified constant exhumation rates, the rocks of two age vs. elevation transects were exhumed at similar to 1.4 +/- 0.2 and similar to 1.1 +/- 0.4 mm/a with an average cooling rate of similar to 40-50degreesC/Ma during Pliocene-Quarternary time. Following other recently published hypotheses regarding the relation between tectonics and climate in the Himalaya, we suggest that this concentrated loss of material was accommodated by motion along a back-stepping thrust to the south and a normal fault zone to the north as part of an extruding wedge. Climatically controlled erosional processes focus on this wedge and suggest that climatically controlled surface processes determine tectonic deformation in the internal part of the Himalaya. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0012-821X ER - TY - JOUR A1 - Thiede, Rasmus Christoph A1 - Arrowsmith, J. Ramón A1 - Bookhagen, Bodo A1 - McWilliams, Michael O. A1 - Sobel, Edward A1 - Strecker, Manfred T1 - From tectonically to erosionally controlled development of the Himalayan orogen N2 - Whether variations in the spatial distribution of erosion influence the location, style, and magnitude of deformation within the Himalayan orogen is a matter of debate. We report new Ar-40/Ar-39 white mica and apatite fission- track (AFT) ages that measure the vertical component of exhumation rates along an similar to 120-km-wide NE-SW transect spanning the greater Sutlej region of northwest India. The Ar-40/Ar-39 data indicate that first the High Himalayan Crystalline units cooled below their closing temperature during the early to middle Miocene. Subsequently, Lesser Himalayan Crystalline nappes cooled rapidly, indicating southward propagation of the orogen during late Miocene to Pliocene time. The AFT data, in contrast, imply synchronous exhumation of a NE-SW-oriented similar to 80 x 40 km region spanning both crystalline nappes during the Pliocene-Quaternary. The locus of pronounced exhumation defined by the AFT data correlates with a region of high precipitation, discharge, and sediment flux rates during the Holocene. This correlation suggests that although tectonic processes exerted the dominant control on the denudation pattern before and until the middle Miocene; erosion may have been the most important factor since the Pliocene Y1 - 2005 SN - 0091-7613 ER - TY - JOUR A1 - Bookhagen, Bodo A1 - Thiede, Rasmus Christoph A1 - Strecker, Manfred T1 - Abnormal monsoon years and their control on erosion and sediment flux in the high, and northwest Himalaya N2 - The interplay between topography and Indian summer monsoon circulation profoundly controls precipitation distribution, sediment transport, and river discharge along the Southern Himalayan Mountain Front (SHF). The Higher Himalayas form a major orographic barrier that separates humid sectors to the south and and regions to the north. During the Indian summer monsoon, vortices transport moisture from the Bay of Bengal, swirl along the SHF to the northwest, and cause heavy rainfall when colliding with the mountain front. In the eastern and central parts of the Himalaya, precipitation measurements derived from passive microwave analysis (SSM/I) show a strong gradient, with high values at medium elevations and extensive penetration of moisture along major river valleys into the orogen. The end of the monsoonal conveyer belt is near the Sutlej Valley in the NW Himalaya, where precipitation is lower and rainfall maxima move to lower elevations. This region thus comprises a climatic transition zone that is very sensitive to changes in Indian summer monsoon strength. To constrain magnitude, temporal, and spatial distribution of precipitation, we analyzed high-resolution passive microwave data from the last decade and identified an abnormal monsoon year (AMY) in 2002. During the 2002 AMY, violent rainstorms conquered orographic barriers and penetrated far into otherwise and regions in the northwest Himalaya at elevations in excess of 3 km asl. While precipitation in these regions was significantly increased and triggered extensive erosional processes (i.e., debris flows) on sparsely vegetated, steep hillslopes, mean rainfall along the low to medium elevations was not significantly greater in magnitude. This shift may thus play an important role in the overall sediment flux toward the Himalayan foreland. Using extended precipitation and sediment flux records for the last century, we show that these events have a decadal recurrence interval during the present-day monsoon circulation. Hence, episodically occurring AMYs control geomorphic processes primarily in the high-elevation and sectors of the orogen, while annual recurring monsoonal rainfall distribution dominates erosion in the low- to medium- elevation parts along the SHF. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Bookhagen, Bodo A1 - Thiede, Rasmus Christoph A1 - Strecker, Manfred T1 - Late Quaternary intensified monsoon phases control landscape evolution in the northwest Himalaya N2 - The intensity of the Asian summer-monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes, terrestrial environments, and marine sediment records. However, the mechanisms of long-lived (2-5 k.y.) intensified monsoon phases, the related changes in precipitation distribution, and their effect on landscape evolution and sedimentation rates are not yet well understood. The and high-elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal (i.e., strengthened) monsoon seasons. Analogous to present-day rainfall anomalies, enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure. We associate landslide triggering during intensified monsoon phases with enhanced precipitation, discharge, and sediment flux leading to an increase in pore-water pressure, lateral scouring of rivers, and over- steepening of hillslopes, eventually resulting in failure of slopes and exceptionally large mass movements. Here we use lacustrine deposits related to spatially and temporally clustered large landslides (>0.5 km(3)) in the Sutlej Valley region of the northwest Himalaya to calculate sedimentation rates and to infer rainfall patterns during late Pleistocene (29-24 ka) and Holocene (10-4 ka) intensified monsoon phases. Compared to present-day sediment-flux measurements, a fivefold increase in sediment-transport rates recorded by sediments in landslide-dammed lakes characterized these episodes of high climatic variability. These changes thus emphasize the pronounced imprint of millennial-scale climate change on surface processes and landscape evolution Y1 - 2005 SN - 0091-7613 ER - TY - JOUR A1 - Thiede, Rasmus Christoph A1 - Arrowsmith, J. Ramón A1 - Bookhagen, Bodo A1 - McWilliams, Michael O. A1 - Sobel, Edward A1 - Strecker, Manfred T1 - Dome formation and extension in the Tethyan Himalaya, Leo Pargil, northwest India N2 - Metamorphic dome complexes occur within the internal structures of the northern Himalaya and southern Tibet. Their origin, deformation, and fault displacement patterns are poorly constrained. We report new field mapping, structural data, and cooling ages from the western flank of the Leo Pargil dome in the northwestern Himalaya in an attempt to characterize its post-middle Miocene structural development. The western flank of the dome is characterized by shallow, west-dipping pervasive foliation and WNW-ESE mineral lineation. Shear-sense indicators demonstrate that it is affected by east-west normal faulting that facilitated exhumation of high-grade metamorphic rocks in a contractional setting. Sustained top-to-northwest normal faulting during exhumation is observed in a progressive transition from ductile to brittle deformation. Garnet and kyanite indicate that the Leo Pargil dome was exhumed from the mid-crust. Ar- 40/Ar-39 mica and apatite fission track (AFT) ages constrain cooling and exhumation pathways front 350 to 60 degrees C and suggest that the dome cooled in three stages since the middle Miocene. Ar-40/Ar-39 white mica ages of 16-14 Ma suggest a first phase of rapid cooling and provide minimum estimates for the onset of dome exhumation. AFT ages between 10 and 8 Ma suggest that ductile fault displacement had ceased by then, and AFT track-length data from high-elevation samples indicate that the rate of cooling had decreased significantly. We interpret this to indicate decreased fault displacement along the Leo Pargil shear zone and possibly a transition to the Kaurik-Chango normal fault system between 10 and 6 Ma. AFT ages from lower elevations indicate accelerated cooling since the Pliocene that cannot be related to pure fault displacement, and therefore may reflect more pronounced regionally distributed and erosion-driven exhumation Y1 - 2006 U6 - https://doi.org/10.1130/B25872.1 ER - TY - JOUR A1 - Bookhagen, Bodo A1 - Fleitmann, Dominik A1 - Nishiizumi, Kunihiko A1 - Strecker, Manfred A1 - Thiede, Rasmus Christoph T1 - Holocene monsoonal dynamics and fluvial terrace formation in the northwest Himalaya, India N2 - Aluminum-26 and beryllium-10 surface exposure dating on cut-and-fill river-terrace surfaces from the lower Sutlej Valley (northwest Himalaya) documents the close link between Indian Summer Monsoon (ISM) oscillations and intervals of enhanced fluvial incision. During the early Holocene ISM optimum, precipitation was enhanced and reached far into the internal parts of the orogen. The amplified sediment flux from these usually dry but glaciated areas caused alluviation of downstream valleys up to 120 m above present grade at ca. 9.9 k.y. B.P. Terrace formation (i.e., incision) in the coarse deposits occurred during century-long weak ISM phases that resulted in reduced moisture availability and most likely in lower sediment flux. Here, we suggest that the lower sediment flux during weak ISM phases allowed rivers to incise episodically into the alluvial fill Y1 - 2006 UR - http://geology.gsapubs.org/ U6 - https://doi.org/10.1130/G22698.1 SN - 0091-7613 ER - TY - JOUR A1 - Thiede, Rasmus Christoph A1 - Ehlers, Todd A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Erosional variability along the northwest Himalaya N2 - Erosional exhumation and topography in mountain belts are temporally and spatially variable over million year timescales because of changes in both the location of deformation and climate. We investigate spatiotemporal variations in exhumation across a 150 x 250 km compartment of the NW Himalaya, India. Twenty-four new and 241 previously published apatite and zircon fission track and white mica Ar-40/Ar-39 ages are integrated with a 1-D numerical model to quantify rates and timing of exhumation alongstrike of several major structures in the Lesser, High, and Tethyan Himalaya. Analysis of thermochronometer data suggests major temporal variations in exhumation occurred in the early middle Miocene and at the Plio-Pleistocene transition. (1) Most notably, exhumation rates for the northern High Himalayan compartments were high (2-3 mm a(-1)) between similar to 23-19 and similar to 3-0 Ma and low (0.5-0.7 mm a(-1)) in between similar to 19-3 Ma. (2) Along the southern High Himalayan slopes, however, high exhumation rates of 1-2 mm a(-1) existed since 11 Ma. (3) Our thermochronology data sets are poorly correlated with present-day rainfall, local relief, and specific stream power which may likely result from (1) a lack of sensitivity of changes in crustal cooling to spatial variations in erosion at high exhumation rates (>similar to 1 mm a(-1)), (2) spatiotemporal variation in erosion not mimicking the present-day topographic or climatic conditions, or (3) the thermochronometer samples in this region having cooled under topography that only weakly resembled the modern-day topography. Y1 - 2009 UR - http://www.agu.org/journals/jf/ U6 - https://doi.org/10.1029/2008jf001010 SN - 0148-0227 ER - TY - JOUR A1 - Dey, Saptarshi A1 - Thiede, Rasmus Christoph A1 - Schildgen, Taylor F. A1 - Wittmann, Hella A1 - Bookhagen, Bodo A1 - Scherler, Dirk A1 - Jain, Vikrant A1 - Strecker, Manfred T1 - Climate-driven sediment aggradation and incision since the late Pleistocene in the NW Himalaya, India JF - Earth & planetary science letters N2 - Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 10(3) to 10(5) yr. To evaluate the potential influence of climate change on these fluctuations, we compare the timing of aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives. New surface-exposure dating of six terrace levels with in-situ cosmogenic Be-10 indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4 +/- 3.2 ka and 43.0 +/- 2.7 ka (1 sigma). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6 +/- 1.2 ka and 15.3 +/- 0.9 ka, while terraces sculpted into the upper Pleistocene-Holocene fan (AF2) provide ages of 9.3 +/- 0.4 ka (T3), 7.1 +/- 0.4 ka (T4), 5.2 +/- 0.4 ka (T5) and 3.6 +/- 0.2 ka (T6). Together with previously published OSL ages yielding the timing of aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision. (C) 2016 Elsevier B.V. All rights reserved. KW - alluvial-fan sedimentation KW - terrestrial cosmogenic nuclides KW - Indian Summer Monsoon KW - Last Glacial Maximum KW - paleo-erosion rate Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.05.050 SN - 0012-821X SN - 1385-013X VL - 449 SP - 321 EP - 331 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Dey, Saptarshi A1 - Thiede, Rasmus Christoph A1 - Schildgen, Taylor F. A1 - Wittmann, Hella A1 - Bookhagen, Bodo A1 - Scherler, Dirk A1 - Strecker, Manfred T1 - Holocene internal shortening within the northwest Sub-Himalaya: Out-of-sequence faulting of the Jwalamukhi Thrust, India JF - Tectonics N2 - 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 Be-10-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 similar to 10ka was followed by episodic reincision, which created four cut-and-fill terrace levels, the oldest of which (T3) was formed at 10.10.9ka. A vertical offset of 445m of terrace T3 across the JMT indicates a shortening rate of 5.60.8 to 7.51.1mma(-1) over the last similar to 10ka. 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. KW - fluvial terrace KW - cosmogenic nuclides KW - steepness index KW - Jwalamukhi Thrust KW - shortening KW - orogenic wedge Y1 - 2016 U6 - https://doi.org/10.1002/2015TC004002 SN - 0278-7407 SN - 1944-9194 VL - 35 SP - 2677 EP - 2697 PB - American Geophysical Union CY - Washington ER -