TY - JOUR A1 - Macaulay, Euan A. A1 - Sobel, Edward A1 - Mikolaichuk, Alexander A1 - Wack, Michael A1 - Gilder, Stuart A. A1 - Mulch, Andreas A1 - Fortuna, Alla B. A1 - Hynek, Scott A1 - Apayarov, Farid T1 - The sedimentary record of the Issyk Kul basin, Kyrgyzstan: climatic and tectonic inferences JF - Basin research N2 - A broad array of new provenance and stable isotope data are presented from two magnetostratigraphically dated sections in the south-eastern Issyk Kul basin of the Central Kyrgyz Tien Shan. The results presented here are discussed and interpreted for two plausible magnetostratigraphic age models. A combination of zircon U-Pb provenance, paleocurrent and conglomerate clast count analyses is used to determine sediment provenance. This analysis reveals that the first coarse-grained, syntectonic sediments (Dzhety Oguz formation) were sourced from the nearby Terskey Range, supporting previous thermochronology-based estimates of a ca. 25-20 Ma onset of deformation in the range. Climate variations are inferred using carbonate stable isotope (delta O-18 and delta C-13) data from 53 samples collected in the two sections and are compared with the oxygen isotope compositions of modern water from 128 samples. Two key features are identified in the stable isotope data set derived from the sediments: (1) isotope values, in particular delta C-13, decrease between ca. 26.0 and 23.6 or 25.6 and 21.0 Ma, and (2) the scatter of delta O-18 values increased significantly after ca. 22.6 or 16.9 Ma. The first feature is interpreted to reflect progressively wetter conditions. Because this feature slightly post-dates the onset of deformation in the Terskey Range, we suggest that it has been caused by orographically enhanced precipitation, implying that surface uplift accompanied late Cenozoic deformation and rock uplift in the Terskey Range. The increased scatter could reflect variable moisture source or availability caused by global climate change following the onset of Miocene glaciations at ca. 22.6 Ma, or enhanced evaporation during the Mid-Miocene climatic optimum at ca. 17-15 Ma. Y1 - 2016 U6 - https://doi.org/10.1111/bre.12098 SN - 0950-091X SN - 1365-2117 VL - 28 SP - 57 EP - 80 PB - Wiley-Blackwell CY - Hoboken ER - 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 -