TY - JOUR A1 - Grujic, Djordje A1 - Govin, Gwladys A1 - Barrier, Laurie A1 - Bookhagen, Bodo A1 - Coutand, Isabelle A1 - Cowan, Beth A1 - Hren, Michael T. A1 - Najman, Yani T1 - Formation of a Rain Shadow BT - O and H Stable Isotope Records in Authigenic Clays From the Siwalik Group in Eastern Bhutan JF - Geochemistry, geophysics, geosystems N2 - We measure the oxygen and hydrogen stable isotope composition of authigenic clays from Himalayan foreland sediments (Siwalik Group), and from present day small stream waters in eastern Bhutan to explore the impact of uplift of the Shillong Plateau on rain shadow formation over the Himalayan foothills. Stable isotope data from authigenic clay minerals (<2 μm) suggest the presence of three paleoclimatic periods during deposition of the Siwalik Group, between ∼7 and ∼1 Ma. The mean δ18O value in paleometeoric waters, which were in equilibrium with clay minerals, is ∼2.5‰ lower than in modern meteoric and stream waters at the elevation of the foreland basin. We discuss the factors that could have changed the isotopic composition of water over time and we conclude that (a) the most likely and significant cause for the increase in meteoric water δ18O values over time is the “amount effect,” specifically, a decrease in mean annual precipitation. (b) The change in mean annual precipitation over the foreland basin and foothills of the Himalaya is the result of orographic effect caused by the Shillong Plateau's uplift. The critical elevation of the Shillong Plateau required to induce significant orographic precipitation was attained after ∼1.2 Ma. (c) By applying scale analysis, we estimate that the mean annual precipitation over the foreland basin of the eastern Bhutan Himalayas has decreased by a factor of 1.7–2.5 over the last 1–3 million years. KW - authigenic clay KW - stable isotope KW - orographic precipitation KW - Siwaliks KW - Himalaya KW - foreland basin Y1 - 2018 U6 - https://doi.org/10.1029/2017GC007254 SN - 1525-2027 VL - 19 IS - 9 SP - 3430 EP - 3447 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Coutand, Isabelle A1 - Carrapa, Barbara A1 - Deeken, Anke A1 - Schmitt, Axel K. A1 - Sobel, Edward A1 - Strecker, Manfred T1 - Propagation of orographic barriers along an active range front : insights from sandstone petrography and detrital apatite fission-track thermochronology in the intramontane Angastaco basin, NW Argentina N2 - The arid Puna plateau of the southern Central Andes is characterized by Cenozoic distributed shortening forming intramontane basins that are disconnected from the humid foreland because of the defeat of orogen-traversing channels. Thick Tertiary and Quaternary sedimentary fills in Puna basins have reduced topographic contrasts between the compressional basins and ranges, leading to a typical low-relief plateau morphology. Structurally identical basins that are still externally drained straddle the eastern border of the Puna and document the eastward propagation of orographic barriers and ensuing aridification. One of them, the Angastaco basin, is transitional between the highly compartmentalized Puna highlands and the undeformed Andean foreland. Sandstone petrography, structural and stratigraphic analysis, combined with detrital apatite fission-track thermochronology from a similar to 6200-m-thick Miocene to Pliocene stratigraphic section in the Angastaco basin, document the late Eocene to late Pliocene exhumation history of source regions along the eastern border of the Puna (Eastern Cordillera (EC)) as well as the construction of orographic barriers along the southeastern flank of the Central Andes. Onset of exhumation of a source in the EC in late Eocene time as well as a rapid exhumation of the Sierra de Luracatao (in the EC) at about 20 Ma are recorded in the detrital sediments of the Angastaco basin. Sediment accumulation in the basin began similar to 15 Ma, a time at which the EC had already built sufficient topography to prevent Puna sourced detritus from reaching the basin. After similar to 13 Ma, shortening shifted eastward, exhuming ranges that preserve an apatite fission-track partial annealing zone recording cooling during the late Cretaceous rifting event. Facies changes and fossil content suggest that after 9 Ma, the EC constituted an effective orographic barrier that prevented moisture penetration into the plateau. Between 3.4 and 2.4 Ma, another orographic barrier was uplifted to the east, leading to further aridification and pronounced precipitation gradients along the mountain front. This study emphasizes the important role of tectonics in the evolution of climate in this part of the Andes Y1 - 2006 UR - http://www3.interscience.wiley.com/cgi-bin/issn?DESCRIPTOR=PRINTISSN&VALUE=0950-091X U6 - https://doi.org/10.1111/j.1365-2117.2006.00283.x SN - 0950-091X ER - TY - JOUR A1 - Alonso, Ricardo N. A1 - Bookhagen, Bodo A1 - Carrapa, Barbara A1 - Coutand, Isabelle A1 - Haschke, Michael A1 - Hilley, George E. A1 - Schoenbohm, Lindsay M. A1 - Sobel, Edward A1 - Strecker, Manfred A1 - Trauth, Martin H. A1 - Villanueva, Arturo T1 - Tectonics, climate and landscape evolution of the Southern Central Andes : the Argentine Puna Plateau and adjacent regions between 22 and 30°S Y1 - 2006 SN - 978-3-540- 24329-8 ER - TY - JOUR A1 - Strecker, Manfred A1 - Alonso, Ricardo N. A1 - Bookhagen, Bodo A1 - Carrapa, Barbara A1 - Coutand, Isabelle A1 - Hain, Mathis P. A1 - Hilley, George E. A1 - Mortimer, Estelle A1 - Schoenbohm, Lindsay M. A1 - Sobel, Edward T1 - Does the topographic distribution of the central Andean Puna Plateau result from climatic or geodynamic processes? N2 - Orogenic plateaus are extensive, high-elevation areas with low internal relief that have been attributed to deep-seated and/or climate-driven surface processes. In the latter case, models predict that lateral plateau growth results from increasing aridity along the margins as range uplift shields the orogen interior from precipitation. We analyze the spatiotemporal progression of basin isolation and filling at the eastern margin of the Puna Plateau of the Argentine Andes to determine if the topography predicted by such models is observed. We find that the timing of basin filling and reexcavation is variable, suggesting nonsystematic plateau growth. Instead, the Airy isostatically compensated component of topography constitutes the majority of the mean elevation gain between the foreland and the plateau. This indicates that deep-seated phenomena, such as changes in crustal thickness and/or lateral density, are required to produce high plateau elevations. In contrast, the frequency of the uncompensated topography within the plateau and in the adjacent foreland that is interrupted by ranges appears similar, although the amplitude of this topographic component increases east of the plateau. Combined with sedimentologic observations, we infer that the low internal relief of the plateau likely results from increased aridity and sediment storage within the plateau and along its eastern margin. Y1 - 2009 UR - http://geology.gsapubs.org/ U6 - https://doi.org/10.1130/G25545a.1 SN - 0091-7613 ER - TY - JOUR A1 - Deeken, Anke A1 - Sobel, Edward A1 - Coutand, Isabelle A1 - Haschke, Michael A1 - Riller, Ulrich A1 - Strecker, Manfred T1 - Development of the southern Eastern Cordillera, NW Argentina, constrained by apatite fission track thermochronology: From early Cretaceous extension to middle Miocene shortening JF - Tectonics N2 - [ 1] For the Puna Plateau and Eastern Cordillera of NW Argentina, the temporal and spatial pattern of deformation and surface uplift remain poorly constrained. Analysis of completely and partially reset apatite fission track samples collected from vertical profiles along an ESE trending transect extending from the plateau interior across the southern Eastern Cordillera at similar to 25 degrees S reveals important constraints on the deformation and exhumation history of this part of the Andes. The data constrain the Neogene Andean development of the Eastern Cordillera as well as rift-related exhumation for some of the sampled locations in the Late Jurassic/Early Cretaceous. An intervening Eocene-Oligocene exhumation episode in the southern Eastern Cordillera was probably related to crustal shortening. Subsequent reburial of the area by Andean foreland basin strata commenced between 30 and 25 Myr. Magnitude and duration of sedimentation, revealed by thermal modeling, differ between the sample locations, pointing to an eastward propagating basin system. In the southern Eastern Cordillera, Andean deformation commenced at 22.5 - 21 Myr, predating both the inferred formation of significant topography by 5 - 7.5 Myr and preservation of sediments in the adjacent Cenozoic basins by 6.5 - 8 Myr. Comparing the calculated structural depth of partially reset samples suggests that newly formed west dipping reverse faults along the former Salta Rift margin accommodated most of the Neogene tectonic movement. Late Cenozoic deformation at the southern Eastern Cordillera began earlier in the west and subsequently propagated eastward. The lateral growth of the orogen is coupled with a foreland basin system developing in front of the range and then becomes subsequently compartmentalized by later emergent topography. Y1 - 2006 U6 - https://doi.org/10.1029/2005TC001894 SN - 0278-7407 VL - 25 IS - 6 PB - Union CY - Washington ER -