TY - JOUR A1 - Carrapa, Barbara A1 - DeCelles, Peter G. A1 - Reiners, Peter W. A1 - Gehrels, George E. A1 - Sudo, Masafumi T1 - Apatite triple dating and white mica Ar-40/Ar-39 thermochronology of syntectonic detritus in the Central Andes : a multiphase tectonothermal history N2 - We applied apatite U-Pb, fission track, and (U-Th)/He triple dating and white mica Ar-40/Ar-39 thermochronology to syntectonic sedimentary rocks from the central Andean Puna plateau in order to determine the source-area geochronology and source sedimentary basin thermal histories, and ultimately the timing of multiple tectonothermal events in the Central Andes. Apatite triple dating of samples from the Eocene Geste Formation in the Salar de Pastos Grandes basin shows late Precambrian-Devonian apatite U-Pb crystallization ages, Eocene apatite fission track (AFT), and Eocene-Miocene (U-Th)/He (ca. 8-47 Ma) cooling ages. Double dating of cobbles from equivalent strata in the Arizaro basin documents early Eocene (46.2 +/- 3.9 Ma) and Cretaceous (107.6 +/- 7.6, 109.5 +/- 7.7 Ma) AFT and Eocene-Oligocene (ca. 55-30 Ma) (U-Th)/He ages. Thermal modeling suggests relatively rapid cooling between ca. 80 and 50 Ma and reheating and subsequent diachronous basin exhumation between ca. 30 Ma and 5 Ma. The Ar-40/Ar-39 white mica ages from the same samples in the Salar de Pastos Grandes area are mainly 400-350 Ma, younger than apatite U-Pb ages, suggesting source- terrane cooling and exhumation during the Devonian-early Carboniferous. Together these data reveal multiple phases of mountain building in the Paleozoic and Cenozoic. Basin burial temperatures within the plateau were limited to <80 degrees C and incision occurred diachronously during the Cenozoic. Y1 - 2009 UR - http://geology.gsapubs.org/ U6 - https://doi.org/10.1130/G25698a.1 SN - 0091-7613 ER - TY - JOUR A1 - Carrapa, Barbara A1 - Reyes-Bywater, Sharon A1 - Safipour, Roxana A1 - Sobel, Edward A1 - Schoenbohm, Lindsay M. A1 - DeCelles, Peter G. A1 - Reiners, Peter W. A1 - Stockli, Daniel T1 - The effect of inherited paleotopography on exhumation of the Central Andes of NW Argentina JF - Geological Society of America bulletin N2 - Differential exhumation in the Puna Plateau and Eastern Cordillera of NW Argentina is controlled by inherited paleostructures and resulting paleotopography related to the Cretaceous Salta Rift paleomargins. The Ceno zoic deformation front related to the development of the Andean retro-arc orogenic system is generally associated with >4 km of exhumation, which is recorded by Cenozoic apatite fi ssion-track (AFT) and (U-Th-[Sm])/He ages (He ages) in the Eastern Cordillera of NW Argentina. New AFT ages from the top of the Nevado de Cachi document Oligocene (ca. 28 Ma) cooling, which, combined with existing data, indicates exhumation of this range between ca. 28 Ma and ca. 14 Ma. However, some of the highest ranges in the Eastern Cordillera preserve Cretaceous ages indicative of limited Cenozoic exhumation. Samples collected from an similar to 3-km-elevation transect along the northern part of the Sierra de Quilmes paleorift fl ank (Laguna Brava) show AFT ages between ca. 80 and ca. 50 Ma and He ages between ca. 45 and ca. 10 Ma. Another set of samples from an similar to 1-km-elevation transect farther to the southwest (La Quebrada) shows Cretaceous AFT ages between ca. 116 Ma and ca. 76 Ma, and mainly Cretaceous He ages, in agreement with AFT data. Analysis of existing AFT and He ages from the area once occupied by the Salta Rift reveals a pattern characterized by Cretaceous ages along paleorift highs and Cenozoic ages within paleorift hanging-wall basins and later foreland basin depocenters. This pattern is interrupted by the Sierras Pampeanas at similar to 28 degrees S, which record mid-Cenozoic ages. Our data are consistent with a complex inherited pattern of pre-Andean paleostructures, likely associated with paleotopography, which was beveled by the Cenozoic regional foreland basin and reactivated during the late Neogene (ca. <10 Ma), strongly controlling the magnitude of Cenozoic uplift and exhumation and thus cooling age distribution. This, combined with variable lithologic erodibility, resulted in an irregular distribution of themochronological ages. Y1 - 2014 U6 - https://doi.org/10.1130/B30844.1 SN - 0016-7606 SN - 1943-2674 VL - 126 IS - 1-2 SP - 66 EP - 77 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Murray, Kendra E. A1 - Braun, Jean A1 - Reiners, Peter W. T1 - Toward Robust Interpretation of Low-Temperature Thermochronometers in Magmatic Terranes JF - Geochemistry, geophysics, geosystems N2 - Many regions central to our understanding of tectonics and landscape evolution are active or ancient magmatic terranes, and robust interpretation of low-temperature thermochronologic ages in these settings requires careful attention to the drivers of rock heating and cooling, including magmatism. However, we currently lack a quantitative framework for evaluating the potential role of magmatic coolingthat is, post-magmatic thermal relaxationin shaping cooling age patterns in regions with a history of intrusive magmatism. Here we use analytical approximations and numerical models to characterize how low-temperature thermochronometers document cooling inside and around plutons in steadily exhuming environments. Our models predict that the thermal field a pluton intrudes into, specifically the ambient temperatures relative to the closure temperature of a given thermochronometer, is as important as the pluton size and temperature in controlling the pattern and extent of thermochronometer resetting in the country rocks around a pluton. We identify one advective and several conductive timescales that govern the relationship between the crystallization and cooling ages inside a pluton. In synthetic vertical age-elevation relationships (AERs), resetting next to plutons results in changes in AER slope that could be misinterpreted as past changes in exhumation rate if the history of magmatism is not accounted for. Finally, we find that large midcrustal plutons, such as those emplaced at similar to 10-15-km depth, can reset the low-temperature thermochronometers far above them in the upper crusta result with considerable consequences for thermochronology in arcs and regions with a history of magmatic activity that may not have a surface expression. KW - He thermochronology KW - Peclet number KW - age-elevation relationships Y1 - 2018 U6 - https://doi.org/10.1029/2018GC007595 SN - 1525-2027 VL - 19 IS - 10 SP - 3739 EP - 3763 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Rohrmann, Alexander A1 - Kapp, Paul A1 - Carrapa, Barbara A1 - Reiners, Peter W. A1 - Guynn, Jerome A1 - Ding, Lin A1 - Heizler, Matthew T1 - Thermochronologic evidence for plateau formation in central Tibet by 45 Ma JF - Geology N2 - The timing of Tibetan plateau development remains elusive, despite its importance for evaluating models of continental lithosphere deformation and associated changes in surface elevation and climate. We present new thermochronologic data [biotite and K-feldspar Ar-40/Ar-39, apatite fission track, and apatite (U-Th)/He] from the central Tibetan plateau (Lhasa and Qiangtang terranes). The data indicate that over large regions, rocks underwent rapid to moderate cooling and exhumation during Cretaceous to Eocene time. This was coeval with >50% upper crustal shortening, suggesting substantial crustal thickening and surface elevation gain. Thermal modeling of combined thermochronometers requires exhumation of most samples to depths of <3 km between 85 and 45 Ma, followed by a decrease in erosional exhumation rate to low values of <0.05 mm/yr. The thermochronological results, when interpreted in the context of the deformation and paleoaltimetric history, are best explained by a scenario of plateau growth that began locally in central Tibet during the Late Cretaceous and expanded to encompass most of central Tibet by 45 Ma. Y1 - 2012 U6 - https://doi.org/10.1130/G32530.1 SN - 0091-7613 VL - 40 IS - 2 SP - 187 EP - 190 PB - American Institute of Physics CY - Boulder ER -