@article{PageLichtDupontNivetetal.2019, author = {Page, M. and Licht, A. and Dupont-Nivet, Guillaume and Meijer, Niels and Barbolini, Natasha and Hoorn, C. and Schauer, A. and Huntington, K. and Bajnai, D. and Fiebig, J. and Mulch, Andreas and Guo, Z.}, title = {Synchronous cooling and decline in monsoonal rainfall in northeastern Tibet during the fall into the Oligocene icehouse}, series = {Geology}, volume = {47}, journal = {Geology}, number = {3}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G45480.1}, pages = {203 -- 206}, year = {2019}, abstract = {The fall into the Oligocene icehouse is marked by a steady decline in global temperature with punctuated cooling at the Eocene-Oligocene transition, both of which are well documented in the marine realm. However, the chronology and mechanisms of cooling on land remain unclear. Here, we use clumped isotope thermometry on northeastern Tibetan continental carbonates to reconstruct a detailed Paleogene surface temperature record for the Asian continental interior, and correlate this to an enhanced pollen data set. Our results show two successive dramatic (>9 degrees C) temperature drops, at 37 Ma and at 33.5 Ma. These large-magnitude decreases in continental temperatures can only be explained by a combination of both regional cooling and shifts of the rainy season to cooler months, which we interpret to reflect a decline of monsoonal intensity. Our results suggest that the response of Asian surface temperatures and monsoonal rainfall to the steady decline of atmospheric CO2 and global temperature through the late Eocene was nonlinear and occurred in two steps separated by a period of climatic instability. Our results support the onset of the Antarctic Circumpolar Current coeval to the Oligocene isotope event 1 (Oi-1) glaciation at 33.5 Ma, reshaping the distribution of surface heat worldwide; however, the origin of the 37 Ma cooling event remains less clear.}, language = {en} } @article{MacaulaySobelMikolaichuketal.2016, author = {Macaulay, Euan A. and Sobel, Edward R. and Mikolaichuk, Alexander and Wack, Michael and Gilder, Stuart A. and Mulch, Andreas and Fortuna, Alla B. and Hynek, Scott and Apayarov, Farid}, title = {The sedimentary record of the Issyk Kul basin, Kyrgyzstan: climatic and tectonic inferences}, series = {Basin research}, volume = {28}, journal = {Basin research}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0950-091X}, doi = {10.1111/bre.12098}, pages = {57 -- 80}, year = {2016}, abstract = {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.}, language = {en} } @article{LichtCosterOcakogluetal.2017, author = {Licht, Alexis and Coster, P. and Ocakoglu, F. and Campbell, C. and Metais, G. and Mulch, Andreas and Taylor, M. and Kappelman, John and Beard, K. Christopher}, title = {Tectono-stratigraphy of the Orhaniye Basin, Turkey: Implications for collision chronology and Paleogene biogeography of central Anatolia}, series = {Journal of Asian earth sciences}, volume = {143}, journal = {Journal of Asian earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {1367-9120}, doi = {10.1016/j.jseaes.2017.03.033}, pages = {45 -- 58}, year = {2017}, abstract = {Located along the Izmir-Ankara-Erzincan Suture (IAES), the Maastrichtian - Paleogene Orhaniye Basin has yielded a highly enigmatic-yet poorly dated- Paleogene mammal fauna, the endemic character of which has suggested high faunal provincialism associated with paleogeographic isolation of the Anatolian landmass during the early Cenozoic. Despite its biogeographic significance, the tectono-stratigraphic history of the Orhaniye Basin has been poorly documented; Here, we combine sedimentary, magnetostratigraphic, and geochronological data to infer the chronology and depositional history of the Orhaniye Basin. We then assess how our new data and interpretations for the Orhaniye Basin impact (1) the timing and mechanisms of seaway closure along the IAES and (2) the biogeographic evolution of Anatolia. Our results show that the Orhaniye Basin initially developed as a forearc basin during the Maastrichtian, before shifting to a retroarc foreland basin setting sometime between the early Paleocene and 44 Ma. This chronology supports a two-step scenario for the assemblage of the central Anatolian landmass, with incipient collision during the Paleocene - Early Eocene and final seaway retreat along the IAES during the earliest Late Eocene after the last marine incursion into the foreland basin. Our dating for the Orhaniye mammal fauna (44-43 Ma) indicates the persistence of faunal endemism in northern Anatolia until at least the late Lutetian despite the advanced stage of IAES closure. The tectonic evolution of dispersal corridors linking northern Anatolia with adjacent parts of Eurasia was not directly associated with IAES closure and consecutive uplifts, but rather with the build-up of continental bridges on the margins of Anatolia, in the Alpine and Tibetan-Himalayan orogens.}, language = {en} } @article{NietoMorenoRohrmannvanderMeeretal.2016, author = {Nieto-Moreno, Vanesa and Rohrmann, Alexander and van der Meer, Marcel T. J. and Damste, Jaap S. Sinninghe and Sachse, Dirk and Tofelde, Stefanie and Niedermeyer, Eva M. and Strecker, Manfred and Mulch, Andreas}, title = {Elevation-dependent changes in n-alkane delta D and soil GDGTs across the South Central Andes}, series = {Earth \& planetary science letters}, volume = {453}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2016.07.049}, pages = {234 -- 242}, year = {2016}, abstract = {Surface uplift of large plateaus may significantly influence regional climate and more specifically precipitation patterns and temperature, sometimes complicating paleoaltimetry interpretations. Thus, understanding the topographic evolution of tectonically active mountain belts benefits from continued development of reliable proxies to reduce uncertainties in paleoaltimetry reconstructions. Lipid biomarker-based proxies provide a novel approach to stable isotope paleoaltimetry and complement authigenic or pedogenic mineral proxy materials, in particular outside semi-arid climate zones where soil carbonates are not abundant but (soil) organic matter has a high preservation potential. Here we present delta D values of soil-derived n-alkanes and mean annual air temperature (MAT) estimates based on branched glycerol dialkyl glycerol tetraether (brGDGT) distributions to assess their potential for paleoelevation reconstructions in the southern central Andes. We analyzed soil samples across two environmental and hydrological gradients that include a hillslope (26-28 degrees S) and a valley (22-24 degrees S) transect on the windward flanks of Central Andean Eastern Cordillera in NW Argentina. Our results show that present-day n-alkane delta D values and brGDGT-based MAT estimates are both linearly related with elevation and in good agreement with present-day climate conditions. Soil n-alkanes show a delta D lapse rate (A(delta D)) of -1.64 parts per thousand/100 m (R-2 = 0.91, p < 0.01) at the hillslope transect, within the range of delta D lapse rates from precipitation and surface waters in other tropical regions in the Andes like the Eastern Cordillera in Colombia and Bolivia and the Equatorial and Peruvian Andes. BrGDGT-derived soil temperatures are similar to monitored winter temperatures in the region and show a lapse rate of Delta T = -0.51 degrees C/100 m (R-2 = 0.91, p < 0.01), comparable with lapse rates from in situ soil temperature measurements, satellite derived land-surface temperatures at this transect, and weather stations from the Eastern Cordillera at similar latitude. As a result of an increasing leeward sampling position along the valley transect lapse rates are biased towards lower values and display higher scatter (Delta(delta D) = -0.9 parts per thousand/100 m, R-2 = 0.76, p < 0.01 and Delta T = -0.19 degrees C/100 m, R-2 = 0.48, p < 0.05). Despite this higher complexity, they are in line with lapse rates from stream-water samples and in situ soil temperature measurements along the same transect. Our results demonstrate that both soil n-alkane delta D values and MAT reconstructions based on brGDGTs distributions from the hillslope transect (Delta(delta D) = -1.64 parts per thousand/100 m, R-2 = 0.91, p < 0.01 and Delta T = -0.51 degrees C/100 m, R-2 = 0.91, p < 0.01) track the direct effects of orography on precipitation and temperature and hence the combined effects of local and regional hydrology as well as elevation. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} } @article{RohrmannSachseMulchetal.2016, author = {Rohrmann, Alexander and Sachse, Dirk and Mulch, Andreas and Pingel, Heiko and Tofelde, Stefanie and Alonso, Ricardo N. and Strecker, Manfred}, title = {Miocene orographic uplift forces rapid hydrological change in the southern central Andes}, series = {Scientific reports}, volume = {6}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/srep35678}, pages = {4283 -- 4306}, year = {2016}, abstract = {Rainfall in the central Andes associated with the South American Monsoon and the South American Low-Level Jet results from orographic effects on atmospheric circulation exerted by the Andean Plateau and the Eastern Cordillera. However, despite its importance for South American climate, no reliable records exist that allow decoding the evolution of thresholds and interactions between Andean topography and atmospheric circulation, especially regarding the onset of humid conditions in the inherently dry southern central Andes. Here, we employ multi-proxy isotope data of lipid biomarkers, pedogenic carbonates and volcanic glass from the Eastern Cordillera of NW Argentina and present the first long-term evapotranspiration record. We find that regional eco-hydrology and vegetation changes are associated with initiation of moisture transport via the South American Low-Level Jet at 7.6 Ma, and subsequent lateral growth of the orogen at 6.5 Ma. Our results highlight that topographically induced changes in atmospheric circulation patterns, not global climate change, were responsible for late Miocene environmental change in this part of the southern hemisphere. This suggests that mountain building over time fundamentally controlled habitat evolution along the central Andes.}, language = {en} } @article{MulchUbaStreckeretal.2009, author = {Mulch, Andreas and Uba, Cornelius Eji and Strecker, Manfred and Schonberg, Ronald and Chamberlain, C. Page}, title = {A Late Miocene stable isotope paleosoil record of Andean foreland precipitation}, issn = {0016-7037}, year = {2009}, language = {en} } @article{RohrmannStreckerBookhagenetal.2014, author = {Rohrmann, Alexander and Strecker, Manfred and Bookhagen, Bodo and Mulch, Andreas and Sachse, Dirk and Pingel, Heiko and Alonso, Ricardo N. and Schildgen, Taylor F. and Montero, Carolina}, title = {Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes}, series = {Earth \& planetary science letters}, volume = {407}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2014.09.021}, pages = {187 -- 195}, year = {2014}, language = {en} } @article{PingelMulchAlonsoetal.2016, author = {Pingel, Heiko and Mulch, Andreas and Alonso, Ricardo N. and Cottle, John and Hynek, Scott A. and Poletti, Jacob and Rohrmann, Alexander and Schmitt, Axel K. and Stockli, Daniel F. and Strecker, Manfred}, title = {Surface uplift and convective rainfall along the southern Central Andes (Angastaco Basin, NW Argentina)}, series = {Earth \& planetary science letters}, volume = {440}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2016.02.009}, pages = {33 -- 42}, year = {2016}, abstract = {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.}, language = {en} } @article{PingelAlonsoMulchetal.2014, author = {Pingel, Heiko and Alonso, Ricardo N. and Mulch, Andreas and Rohrmann, Alexander and Sudo, Masafumi and Strecker, Manfred}, title = {Pliocene orographic barrier uplift in the southern Central Andes}, series = {Geology}, volume = {42}, journal = {Geology}, number = {8}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G35538.1}, pages = {691 -- 694}, year = {2014}, abstract = {Sedimentary basin fills along the windward flanks of orogenic plateaus are valuable archives of paleoenvironmental change with the potential to resolve the history of surface uplift and orographic barrier formation. The intermontane basins of the southern Central Andes contain thick successions of sedimentary material that are commonly interbedded with datable volcanic ashes. We relate variations in the hydrogen isotopic composition of hydrated volcanic glass (delta D-g) of Neogene to Quaternary fills in the semiarid intermontane Humahuaca Basin (Eastern Cordillera, northwest Argentina) to spatiotemporal changes in topography and associated orographic effects. delta D values from volcanic glass in the basin strata (-117 parts per thousand to -98 parts per thousand) show two main trends that accompany observed tectonosedimentary events in the study area. Between 6.0 and 3.5 Ma, delta D-g values decrease by similar to 17 parts per thousand; this is associated with surface uplift in the catchment area. After 3.5 Ma, delta D-g values show abrupt deuterium enrichment, which we associate with (1) the attainment of threshold elevations for blocking moisture transport in the basin-bounding ranges to the east, and (2) the onset of semiarid conditions in the basin. Such orographic barriers throughout the eastern flanks of the Central Andes have impeded moisture transport into the orogen interior; this has likely helped maintain aridity and internal drainage conditions on the adjacent Andean Plateau.}, language = {en} }