TY - JOUR A1 - Pingel, Heiko A1 - Mulch, Andreas A1 - Alonso, Ricardo N. A1 - Cottle, John A1 - Hynek, Scott A. A1 - Poletti, Jacob A1 - Rohrmann, Alexander A1 - Schmitt, Axel K. A1 - Stockli, Daniel F. A1 - Strecker, Manfred T1 - Surface uplift and convective rainfall along the southern Central Andes (Angastaco Basin, NW Argentina) JF - Earth & planetary science letters N2 - Stable-isotopic and sedimentary records from the orogenic Puna Plateau of NW Argentina and adjacent intermontane basins to the east furnish a unique late Cenozoic record of range uplift and ensuing paleoenvironmental change in the south-central Andes. Today, focused precipitation in this region occurs along the eastern, windward flanks of the Eastern Cordillera and Sierras Pampeanas ranges, while the orogen interior constitutes high-elevation regions with increasingly arid conditions in a westward direction. As in many mountain belts, such hydrologic and topographic gradients are commonly mirrored by a systematic relationship between the oxygen and hydrogen stable isotope ratios of meteoric water and elevation. The glass fraction of isotopically datable volcanic ash intercalated in sedimentary sequences constitutes an environmental proxy that retains a signal of the hydrogen-isotopic composition of ancient precipitation. This isotopic composition thus helps to elucidate the combined climatic and tectonic processes associated with topographic growth, which ultimately controls the spatial patterns of precipitation in mountain belts. However, between 25.5 and 27 degrees S present-day river-based hydrogen isotope lapse rates are very low, possibly due to deep-convective seasonal storms that dominate runoff. If not accounted for, the effects of such conditions on moisture availability in the past may lead to misinterpretations of proxy-records of rainfall. Here, we present hydrogen-isotope data of volcanic glass (delta Dg), extracted from 34 volcanic ash layers in different sedimentary basins of the Eastern Cordillera and the Sierras Pampeanas. Combined with previously published delta Dg records and our refined U-Pb and (U-Th)/He zircon geochronology on 17 tuff samples, we demonstrate hydrogen-isotope variations associated with paleoenvironmental change in the Angastaco Basin, which evolved from a contiguous foreland to a fault-bounded intermontane basin during the late Mio-Pliocene. We unravel the environmental impact of Mio-Pliocene topographic growth and associated orographic effects on long-term hydrogen-isotope records of rainfall in the south-central Andes, and potentially identify temporal variations in regional isotopic lapse rates that may also apply to other regions with similar topographic boundary conditions. (C) 2016 Elsevier B.V. All rights reserved. KW - hydrogen stable isotopes KW - volcanic glass KW - paleoaltimetry KW - NW-Argentine Andes KW - orographic barrier uplift KW - convective rainfall Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.02.009 SN - 0012-821X SN - 1385-013X VL - 440 SP - 33 EP - 42 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Landgraf, Angela A1 - Schildgen, Taylor F. A1 - Stockli, Daniel F. A1 - Fox, Matthew A1 - Ghassemi, Mohammad R. A1 - Kirby, Eric A1 - Strecker, Manfred T1 - The growth of a mountain belt forced by base-level fall: Tectonics and surface processes during the evolution of the Alborz Mountains, N Iran JF - Earth & planetary science letters N2 - The idea that climatically modulated erosion may impact orogenic processes has challenged geoscientists for decades. Although modeling studies and physical calculations have provided a solid theoretical basis supporting this interaction, to date, field-based work has produced inconclusive results. The central-western Alborz Mountains in the northern sectors of the Arabia-Eurasia collision zone constitute a promising area to explore these potential feedbacks. This region is characterized by asymmetric precipitation superimposed on an orogen with a history of spatiotemporal changes in exhumation rates, deformation patterns, and prolonged, km-scale base-level changes. Our analysis suggests that despite the existence of a strong climatic gradient at least since 17.5 Ma, the early orogenic evolution (from similar to 36 to 9-6 Ma) was characterized by decoupled orographic precipitation and tectonics. In particular, faster exhumation and sedimentation along the more arid southern orogenic flank point to a north-directed accretionary flux and underthrusting of Central Iran. Conversely, from 6 to 3 Ma, erosion rates along the northern orogenic flank became higher than those in the south, where they dropped to minimum values. This change occurred during a similar to 3-Myr-long, km-scale base-level lowering event in the Caspian Sea. We speculate that mass redistribution processes along the northern flank of the Alborz and presumably across all mountain belts adjacent to the South Caspian Basin and more stable areas of the Eurasian plate increased the sediment load in the basin and ultimately led to the underthrusting of the Caspian Basin beneath the Alborz Mountains. This underthrusting in turn triggered a new phase of northward orogenic expansion, transformed the wetter northern flank into a new pro-wedge, and led to the establishment of apparent steady-state conditions along the northern orogenic flank (i.e., rock uplift equal to erosion rates). Conversely, the southern mountain front became the retro-wedge and experienced limited tectonic activity. These observations overall raise the possibility that mass-distribution processes during a pronounced erosion phase driven by base-level changes may have contributed to the inferred regional plate-tectonic reorganization of the northern Arabia-Eurasia collision during the last similar to 5 Ma. (C) 2015 Elsevier B.V. All rights reserved. KW - orogenic processes KW - surface processes KW - base-level fall KW - erosion KW - rock uplift KW - knickpoints Y1 - 2015 U6 - https://doi.org/10.1016/j.epsl.2015.05.051 SN - 0012-821X SN - 1385-013X VL - 425 SP - 204 EP - 218 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Uba, Cornelius Eji A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Sudo, Masafumi A1 - Stockli, Daniel F. A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Arabia-Eurasia continental collision insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran JF - Geological Society of America bulletin N2 - A poorly understood lag time of 15-20 m.y. exists between the initial Arabia-Eurasia continental collision in late Eocene to early Oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late Miocene. The late Eocene to Miocene-Pliocene clastic and shallow-marine sedimentary rocks of the Kond, Eyvanekey, and Semnan Basins in the Alborz Mountains (northern Iran) offer the possibility to track the evolution of this orogen in the framework of collision processes. A transition from volcaniclastic submarine deposits to shallow-marine evaporites and terrestrial sediments occurred shortly after 36 Ma in association with reversals in sediment provenance, strata tilting, and erosional unroofing. These events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched Arabian lithosphere. This early stage of collision produced topographic relief associated with shallow foreland basins, suggesting that shortening and tectonic loading occurred at low rates. Starting from the early Miocene (17.5 Ma), flexural subsidence in response to foreland basin initiation occurred. Fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early Miocene. We suggest that the lag time between the initiation of continental collision (36 Ma) and the acceleration of regional deformation (20-17.5 Ma) reflects a two-stage collision process, involving the "soft" collision of stretched lithosphere at first and "hard" collision following the arrival of unstretched Arabian continental litho sphere in the subduction zone. Y1 - 2011 U6 - https://doi.org/10.1130/B30091.1 SN - 0016-7606 VL - 123 IS - 1-2 SP - 106 EP - 131 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Sobel, Edward A1 - Schoenbohm, Lindsay M. A1 - Chen, Jie A1 - Thiede, Rasmus Christoph A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Late Miocene-Pliocene deceleration of dextral slip between Pamir and Tarim: Implications for Pamir orogenesis JF - EARTH AND PLANETARY SCIENCE LETTERS N2 - The timing of the late Cenozoic collision between the Pamir salient and the Tien Shan as well as changes in the relative motion between the Pamir and Tarim are poorly constrained. The northern margin of the Pamir salient indented northward by similar to 300 km during the late Cenozoic, accommodated by south-dipping intracontinental subduction along the Main Pamir Thrust (MPT) coupled to strike-slip faults on the eastern flank of the orogen and both strike-slip and thrust faults on the western margin. The Kashgar-Yecheng transfer system (KYTS) is the main dextral slip shear zone separating Tarim from the Eastern Pamir, with an estimated cumulative offset of similar to 280 km at an average late Cenozoic dextral slip rate of 11-15 mm/a (Cowgill, 2010). In order to better constrain the slip history of the KYTS, we collected thermochronologic samples along the eastward-flowing, deeply incised, antecedent Tashkorgan-Yarkand River, which crosses the fault system on the eastern flank of the orogen. We present 29 new biotite (40)Ar/(39)Ar ages, apatite and zircon (U-Th-Sm)/He ages, and apatite fission track (AFT) analysis, combined with published muscovite and biotite (40)Ar/(39)Ar and AFT data, to create a unique thermochronologic dataset in this poorly studied and remote region. We constrain the timing of four major N-trending faults: the latter three are strands of the KYTS. The westernmost, the Kuke fault, experienced significant dip-slip, west-side-up displacement between > 12 and 6 Ma. To the east, within the KYTS, our new thermochronologic data and geomorphic observations suggest that the Kumtag and Kusilaf dextral slip faults have been inactive since at least 3-5 Ma. Long-term incision rates across the Aertashi dextral slip fault, the easternmost strand of the KYTS, are compatible with slow horizontal slip rates of 1.7-5.3 mm/a over the past 3 to 5 Ma. In summary, these data show that the slip rate of the KYTS decreased substantially during the late Miocene or Pliocene. Furthermore, Miocene-present regional kinematic reconstructions suggest that this deceleration reflects the substantial increase of northward motion of Tarim rather than a significant decrease of the northward velocity of the Pamir. (C) 2011 Elsevier B.V. All rights reserved. KW - thermochronology KW - neotectonics KW - Pamir KW - Tien Shan KW - strike-slip fault KW - intracontinental subduction Y1 - 2011 U6 - https://doi.org/10.1016/j.epsl.2011.02.012 SN - 0012-821X VL - 304 IS - 3-4 SP - 369 EP - 378 PB - ELSEVIER SCIENCE BV CY - AMSTERDAM ER - TY - JOUR A1 - Bande, Alejandro A1 - Horton, Brian K. A1 - Ramirez, Juan C. A1 - Mora, Andres A1 - Parra, Mauricio A1 - Stockli, Daniel F. T1 - Clastic deposition, provenance, and sequence of Andean thrusting in the frontal Eastern Cordillera and Llanos foreland basin of Colombia JF - Geological Society of America bulletin N2 - Sedimentological, provenance, and detrital thermochronological results for basin fill at the modern deformation front of the northern Andes (6 degrees N latitude) provide a long-term, Eocene to Pliocene record of foreland-basin sedimentation along the Eastern Cordillera !Janos basin boundary in Colombia. Lithofacies assemblages and paleocurrent orientations in the upward-coarsening, 5-km-thick succession of the Nunchia syncline reveal a systematic shift from craton-derived, shallow-marine distal foreland (back-bulge) accumulation in the Mirador Formation, to orogen-sourced, deltaic, and coastalinfluenced sedimentation of the distal to medial foreland (foredeep) in the Carbonera and Leon Formations, to anastomosing fluvial and distributive braided fluvial megafan systems of the proximal foreland (foredeep to wedge-top) basin in the lower and upper Guayabo Formation. These changes in depositional processes and sediment dispersal are supported by up-section variations in detrital zircon U-Pb and (U-Th)/He ages that record exhumation of evolving, compartmentalized sediment source areas in the Eastern Cordillera. The data are interpreted in terms of a progressive eastward advance in foldand-thrust deformation, with late Eocene Oligocene deformation in the axial zone of the Eastern Cordillera along the western edge of Floresta basin (Soapaga thrust), early Miocene reactivation (inversion) of the eastern margin of the Mesozoic rift system (Pajarito and Guaicaramo thrusts), and middle late Miocene propagation of a footwall shortcut fault (Vopal thrust) that created the Nunchia syncline in a wedge-top (piggyback) setting of the eastern foothills along the transition from the Eastern Cordillera to Harms foreland basin. Collectively, the data presented here for the frontal Eastern Cordillera define a general in-sequence pattern of eastwardadvancing fold-and-thrust deformation during Cenozoic east-west shortening in the Colombian Andes. Y1 - 2012 U6 - https://doi.org/10.1130/B30412.1 SN - 0016-7606 VL - 124 IS - 1-2 SP - 59 EP - 76 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Wilke, Franziska Daniela Helena A1 - Sobel, Edward A1 - O'Brien, Patrick J. A1 - Stockli, Daniel F. T1 - Apatite fission track and (U-Th)/He ages from the Higher Himalayan Crystallines, Kaghan Valley, Pakistan: Implications for an Eocene Plateau and Oligocene to Pliocene exhumation JF - Journal of Asian earth sciences N2 - Apatite fission track and apatite and zircon (U-Th)/He ages were obtained from high- and ultra high-pressure rocks from the Kaghan Valley, Pakistan. Four samples from the high altitude northern parts of the valley yielded apatite fission track ages between 24.5 +/- 3.7 and 15.6 +/- 2.1 Ma and apatite (U-Th)/He ages between 21.0 +/- 0.6 and 5.3 +/- 0.2 Ma. These data record cooling of the formerly deeply-subducted high-grade metamorphic rocks induced by denudation and exhumation consistent with extension and back sliding along the reactivated, normal-acting Main Mantle Thrust. Overlap at around 10 Ma between fission track and (U-Th)/He ages is recognised at one location (Besal) showing that fast cooling occurred due to brittle reactivation of a former thrust fault. Widespread Miocene cooling is also evident in adjacent areas to the west (Deosai Plateau, Tso Moran), most likely related to uplift and unroofing linked to continued underplating of the Indian lower crust beneath Ladakh and Kohistan in the Late Eocene to Oligocene. In the southernmost part of the study area, near Naran, two significantly younger Late Miocene to Pliocene apatite fission track ages of 7.6 +/- 2.1 to 4.0 +/- 0.5 Ma suggest a spatial and temporal separation of exhumation processes. These younger ages are best explained by enhanced Late Miocene uplift and erosion driven by thrusting along the Main Boundary Thrust. KW - NW Himalaya KW - Kaghan Valley KW - Thermochronology KW - AFT KW - (U-Th)/He KW - Cooling rates Y1 - 2012 U6 - https://doi.org/10.1016/j.jseaes.2012.06.014 SN - 1367-9120 VL - 59 IS - 3 SP - 14 EP - 23 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ballato, Paolo A1 - Stockli, Daniel F. A1 - Ghassemi, Mohammad R. A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Hassanzadeh, Jamshid A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Accommodation of transpressional strain in the Arabia-Eurasia collision zone new constraints from (U-Th)/He thermochronology in the Alborz mountains, north Iran JF - Tectonics N2 - The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia-Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW-striking frontal ramps that are kinematically linked to inherited E-W-striking, right-stepping lateral to obliquely oriented ramps. New zircon and apatite (U-Th)/He data provide a high-resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW-directed thrusting across the frontal ramps at similar to 18-14 and 9.5-7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U-shaped geometry. Uniform cooling ages of similar to 7-6 Ma along the southernmost E-W striking oblique ramp and across its associated NW-striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N-dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike-slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that similar to 7-6-m.y.-old S-directed thrusting predated inception of the westward motion of the South Caspian Basin. Citation: Ballato, P., D. F. Stockli, M. R. Ghassemi, A. Landgraf, M. R. Strecker, J. Hassanzadeh, A. Friedrich, and S. H. Tabatabaei (2012), Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains. Y1 - 2013 U6 - https://doi.org/10.1029/2012TC003159 SN - 0278-7407 VL - 32 IS - 1 SP - 1 EP - 18 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Sobel, Edward A1 - Chen, Jie A1 - Schoenbohm, Lindsay M. A1 - Thiede, Rasmus Christoph A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Oceanic-style subduction controls late Cenozoic deformation of the Northern Pamir orogen JF - Earth & planetary science letters N2 - The northern part of the Pamir orogen is the preeminent example of an active intracontinental subduction zone in the early stages of continent-continent collision. Such zones are the least understood type of plate boundaries because modern examples are few and of limited access, and ancient analogs have been extensively overprinted by subsequent tectonic and erosion processes. In the Pamir, it has been assumed that most of the plate convergence was accommodated by overthrusting along the plate-bounding Main Pamir Thrust (MPT), which forms the principal northern mountain and deformation front of the Pamir. However, the synopsis of our new and previously published thermochronologic data from this region shows that the hanging wall of the MPT experienced relatively minor amounts of late Cenozoic exhumation. The Pamir orogen as a whole is an integral part of the overriding plate in a subduction system, while the remnant basin to the north constitutes the downgoing plate, with the bulk of the convergence accommodated by underthrusting. Herein, we demonstrate that the observed deformation of the upper and lower plates within the Pamir-Alai convergence zone resembles highly arcuate oceanic subduction systems characterized by slab rollback, subduction erosion, subduction accretion, and marginal slab-tear faults. We suggest that the curvature of the North Pamir is genetically linked to the short width and rollback of the south-dipping Alai slab; northward motion (indentation) of the Pamir is accommodated by crustal processes related to this rollback. The onset of south-dipping subduction is tentatively linked to intense Pamir contraction following break-off of the north-dipping Indian slab beneath the Karakoram. KW - subduction accretion KW - subduction erosion KW - exhumation KW - thermochronology KW - intracontinental deformation KW - Pamir Y1 - 2013 U6 - https://doi.org/10.1016/j.epsl.2012.12.009 SN - 0012-821X VL - 363 IS - 1 SP - 204 EP - 218 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Thiede, Rasmus Christoph A1 - Sobel, Edward A1 - Chen, Jie A1 - Schoenbohm, Lindsay M. A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Late Cenozoic extension and crustal doming in the India-Eurasia collision zone new thermochronologic constraints from the NE Chinese Pamir JF - Tectonics N2 - The northward motion of the Pamir indenter with respect to Eurasia has resulted in coeval thrusting, strike-slip faulting, and normal faulting. The eastern Pamir is currently deformed by east-west oriented extension, accompanied by uplift and exhumation of the Kongur Shan (7719m) and Muztagh Ata (7546m) gneiss domes. Both domes are an integral part of the footwall of the Kongur Shan extensional fault system (KES), a 250 km long, north-south oriented graben. Why active normal faulting within the Pamir is primarily localized along the KES and not distributed more widely throughout the orogen has remained unclear. In addition, relatively little is known about how deformation has evolved throughout the Cenozoic, despite refined estimates on present-day crustal deformation rates and microseismicity, which indicate where crustal deformation is presently being accommodated. To better constrain the spatiotemporal evolution of faulting along the KES, we present 39 new apatite fission track, zircon U-Th-Sm/He, and Ar-40/Ar-39 cooling ages from a series of footwall transects along the KES graben shoulder. Combining these data with present-day topographic relief, 1-D thermokinematic and exhumational modeling documents successive stages, rather than synchronous deformation and gneiss dome exhumation. While the exhumation of the Kongur Shan commenced during the late Miocene, extensional processes in the Muztagh Ata massif began earlier and have slowed down since the late Miocene. We present a new model of synorogenic extension suggesting that thermal and density effects associated with a lithospheric tear fault along the eastern margin of the subducting Alai slab localize extensional upper plate deformation along the KES and decouple crustal motion between the central/western Pamir and eastern Pamir/Tarim basin. KW - Pamir KW - gneiss domes KW - collision KW - extension KW - thermochronology KW - exhumation Y1 - 2013 U6 - https://doi.org/10.1002/tect.20050 SN - 0278-7407 VL - 32 IS - 3 SP - 763 EP - 779 PB - American Geophysical Union CY - Washington ER -