TY - JOUR A1 - Zhuang, Guangsheng A1 - Johnstone, Samuel A. A1 - Hourigan, Jeremy A1 - Ritts, Bradley A1 - Robinson, Alexander A1 - Sobel, Edward T1 - Understanding the geologic evolution of Northern Tibetan Plateau with multiple thermochronometers JF - Gondwana research : international geoscience journal ; official journal of the International Association for Gondwana Research N2 - The early onset of deformation following the India-Asia collision, Neogene expanse of uplift, and complex systems that comprise strike-slip faults, thrust faults, and intermontane basins characterize the Cenozoic tectonism of Northern Tibetan Plateau and raise two prominent questions in orogenic geodynamics: 1) What mechanism(s) control(s) the transfer of stress related to the India-Asia collision across the distance of >2000 km; and 2) Why the development of high topography was delayed in the Northern Tibetan Plateau and what does it reveal about how the internal forces and external boundary conditions evolved. To address these two questions, we reconstruct a holistic spatial-temporal deformation history of the Northern Tibetan Plateau by using a range of thermochronometers, with closure temperature spanning from 350 degrees C to-60-70 degrees C. This multi-thermochronometer study reveals three stages of faulting related cooling, in the early Cretaceous, in Paleocene-Eocene and in middle-late Miocene. We observe that Paleocene-Eocene deformation was spatially restricted and mostly occurred on reactivated Cretaceous structures, indicating a control of pre-existing weakness on early Cenozoic deformation. Extensive Neogene deformation contrasts with restricted Paleocene-Eocene deformation and relatively quiescent shortening during the Oligocene-early Miocene, which implies a change in the regional tectonics regime. Global plate reconstructions show that this tectonic reorganization is coeval with an increase in Pacific-Asia plate convergence rates. We argue that this change in regional tectonics is a result of increasing constrictive environment of the eastern plate boundary, which changed the behavior of the Altyn Tagh fault the boundary fault of Northern Tibetan Plateau, causing it to change from feeding slip into structures out of the plateau to feeding slip into structures at plateau margins. KW - Northern Tibetan Plateau KW - Thermochronology KW - Altyn Tagh Fault KW - Pacific-Asia convergence KW - Gravitational potential energy Y1 - 2018 U6 - https://doi.org/10.1016/j.gr.2018.02.014 SN - 1342-937X SN - 1878-0571 VL - 58 SP - 195 EP - 210 PB - Elsevier CY - Amsterdam 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 - Macaulay, Euan A. A1 - Sobel, Edward A1 - Mikolaichuk, Alexander A1 - Landgraf, Angela A1 - Kohn, Barry A1 - Stuart, Finlay T1 - Thermochronologic insight into late Cenozoic deformation in the basement-cored Terskey Range, Kyrgyz Tien Shan JF - Tectonics N2 - Basement-cored ranges formed by reverse faulting within intracontinental mountain belts are often composed of poly-deformed lithologies. Geological data capable of constraining the timing, magnitude, and distribution of the most recent deformational phase are usually missing in such ranges. In this paper, we present new low temperature thermochronological and geological data from a transect through the basement-cored Terskey Range, located in the Kyrgyz Tien Shan. Using these data, we are able to investigate the range's late Cenozoic deformation for the first time. Displacements on reactivated faults are constrained and deformation of thermochronologically derived structural markers is assessed. These structural markers postdate the earlier deformational phases, providing the only record of Cenozoic deformation and of the reactivation of structures within the Terskey Range. Overall, these structural markers have a southern inclination, interpreted to reflect the decreasing inclination of the reverse fault bounding the Terskey Range. Our thermochronological data are also used to investigate spatial and temporal variations in the exhumation of the Terskey Range, identifying a three-stage Cenozoic exhumation history: (1) virtually no exhumation in the Paleogene, (2) increase to slightly higher exhumation rates at similar to 26-20Ma, and (3) significant increase in exhumation starting at similar to 10Ma. KW - Thermochronology KW - Basement-cored ranges KW - Tien Shan KW - Structural geology Y1 - 2013 U6 - https://doi.org/10.1002/tect.20040 SN - 0278-7407 VL - 32 IS - 3 SP - 487 EP - 500 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Loebens, Stefan A1 - Sobel, Edward A1 - Bense, Frithjof A. A1 - Wemmer, Klaus A1 - Dunkl, Istvan A1 - Siegesmund, Siegfried T1 - Refined exhumation history of the northern Sierras Pampeanas, Argentina JF - Tectonics N2 - The Sierra de Aconquija and Cumbres Calchaquies in the thick-skinned northern Sierras Pampeanas, NW Argentina present an ideal setting to investigate the tectonically and erosionally controlled exhumation and uplift history of mountain ranges using thermochronological methods. Although these ranges are located along strike of one another, their spatiotemporal evolution varies significantly. Integrating modeled cooling histories constrained by K-Ar ages of muscovite and biotite, apatite fission track data as well as (U-Th)/He measurement of zircon and apatite reveal the structural evolution of these ranges beginning in the late stage of the Paleozoic Famatinian Orogeny. Following localized rift-related exhumation in the central part of the study area and slow erosion elsewhere, growth of the modern topography commenced in the Cenozoic during Andean deformation. The main activity occurred during the late Miocene, with varying magnitudes of rock uplift, surface uplift, and exhumation in the two mountain ranges. The Cumbres Calchaquies is characterized by a total of 5-7km of vertical rock uplift, around 3km of crestal surface uplift, and a maximum exhumation of 2-4km since that time. The Sierra de Aconquija experienced 10-13km of vertical rock uplift, similar to 4-5km of peak surface uplift, and 6-8km of exhumation since around 9Ma. Much of this exhumation occurred along a previously poorly recognized fault. Miocene reactivation of Cretaceous rift structures may explain along-strike variations within these ranges. Dating of sedimentary samples from adjacent basins supports the evolutionary model developed for the mountain ranges. KW - Thermochronology KW - Sierras Pampeanas KW - thermal modeling KW - exhumation and uplift Y1 - 2013 U6 - https://doi.org/10.1002/tect.20038 SN - 0278-7407 VL - 32 IS - 3 SP - 453 EP - 472 PB - American Geophysical Union CY - Washington ER -