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 - Macaulay, Euan A. A1 - Sobel, Edward A1 - Mikolaichuk, Alexander A1 - Kohn, Barry A1 - Stuart, Finlay M. T1 - Cenozoic deformation and exhumation history of the Central Kyrgyz Tien Shan JF - Tectonics N2 - New low-temperature thermochronological data from 80 samples in eastern Kyrgyzstan are combined with previously published data from 61 samples to constrain exhumation in a number of mountain ranges in the Central Kyrgyz Tien Shan. All sampled ranges are found to have a broadly consistent Cenozoic exhumation history, characterized by initially low cooling rates (<1 degrees C/Myr) followed by a series of increases in exhumation that occurred diachronously across the region in the late Cenozoic that are interpreted to record the onset of deformation in different mountain ranges. Combined with geological estimates for the onset of proximal deformation, our data suggest that the Central Kyrgyz Tien Shan started deforming in the late Oligocene-early Miocene, leading to the development of several, widely spaced mountain ranges separated by large intermontane basins. Subsequently, more ranges have been constructed in response to significant shortening increases across the Central Kyrgyz Tien Shan, notably in the late Miocene. The order of range construction is interpreted to reflect variations in the susceptibility of inherited structures to reactivation. Reactivated structures are also shown to have significance along strike variations in fault vergence and displacement, which have influenced the development and growth of individual mountain ranges. Moreover, the timing of deformation allows the former extent of many intermontane basins that have since been partitioned to be inferred; this can be linked to the highly time-transgressive onset of late Cenozoic coarse clastic sedimentation. KW - thermochronology KW - Tien Shan KW - out-of-sequence deformation Y1 - 2014 U6 - https://doi.org/10.1002/2013TC003376 SN - 0278-7407 SN - 1944-9194 VL - 33 IS - 2 SP - 135 EP - 165 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mortimer, Estelle A1 - Kirstein, Linda A. A1 - Stuart, Finlay M. A1 - Strecker, Manfred T1 - Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System JF - Earth & planetary science letters N2 - The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes. lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U-Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations. (C) 2016 Elsevier B.V. All rights reserved. KW - apatite helium thermochronology KW - normal-fault evolution KW - fault linkage KW - East African Rift System Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.08.040 SN - 0012-821X SN - 1385-013X VL - 455 SP - 62 EP - 72 PB - Elsevier CY - Amsterdam ER -