TY - JOUR A1 - Diaz, Nathalie A1 - Dietrich, Fabienne A1 - Sebag, David A1 - King, Georgina E. A1 - Valla, Pierre G. A1 - Durand, Alain A1 - Garcin, Yannick A1 - de Saulie, Geoffroy A1 - Deschamps, Pierre A1 - Herman, Frederic A1 - Verrecchia, Eric P. T1 - Pedo-sedimentary constituents as paleoenvironmental proxies in the Sudano-Sahelian belt during the Late Quaternary (southwestern Chad Basin) JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Climate and environmental changes since the Last Glacial Maximum in the tropical zone of West Africa are usually inferred from marine and continental records. In this study, the potential of carbonate pedo-sedimentary geosystems, i.e. Vertisol relics, to record paleoenvironmental changes in the southwestern part of Chad Basin are investigated. A multi-dating approach was applied on different pedogenic organo-mineral constituents. Optically stimulated luminescence (OSL) dating was performed on the soil K-rich feldspars and was combined with radiocarbon dating on both the inorganic (C-14(inorg)) and organic carbon (C-14(org)) soil fractions. Three main pedo-sedimentary processes were assessed over the last 20 ka BP: 1) the soil parent material deposition, from 18 ka to 12 ka BP (OSL), 2) the soil organic matter integration, from 11 cal ka to 8 cal ka BP (C-14(org)), and 3) the pedogenic carbonate nodule precipitation, from 7 cal ka to 5 cal ka BP (C-14(inorg)). These processes correlate well with the Chad Basin stratigraphy and West African records and are shown to be related to significant changes in the soil water balance responding to the evolution of continental hydrology during the Late Quaternary. The last phase affecting the Vertisol relics is the increase of erosion, which is hypothesized to be due to a decrease of the vegetation cover triggered by (i) the onset of drier conditions, possibly strengthened by (ii) anthropogenic pressure. Archaeological data from Far North Cameroon and northern Nigeria, as well as sedimentation times in Lake Tilla (northeastern Nigeria), were used to test these relationships. The increase of erosion is suggested to possibly occur between c. 3 cal ka and 1 cal ka BP. Finally, satellite images revealed similar geosystems all along the Sudano-Sahelian belt, and initial C-14(inorg) ages of the samples collected in four sites gave similar ages to those reported in this study. Consequently, the carbonate pedo-sedimentary geosystems are valuable continental paleoenvironmental archives and soil water balance proxies of the semiarid tropics of West Africa. (C) 2018 Elsevier Ltd. All rights reserved. KW - Pedogenic carbonate nodules KW - Vertisol genesis KW - Soil water balance KW - Optical methods KW - Radiogenic isotopes KW - Quaternary KW - Monsoon KW - Western Africa Y1 - 2018 U6 - https://doi.org/10.1016/j.quascirev.2018.05.022 SN - 0277-3791 VL - 191 SP - 348 EP - 362 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Panek, Tomas A1 - Korup, Oliver A1 - Lenart, Jan A1 - Hradecky, Jan A1 - Brezny, Michal T1 - Giant landslides in the foreland of the Patagonian Ice Sheet JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Quaternary glaciations have repeatedly shaped large tracts of the Andean foreland. Its spectacular large glacial lakes, staircases of moraine ridges, and extensive outwash plains have inspired generations of scientists to reconstruct the processes, magnitude, and timing of ice build-up and decay at the mountain front. Surprisingly few of these studies noticed many dozens of giant (≥108 m3) mass-wasting deposits in the foreland. We report some of the world's largest terrestrial landslides in the eastern piedmont of the Patagonian Ice Sheet (PIS) along the traces of the former Lago Buenos Aires and Lago Puyerredón glacier lobes and lakes. More than 283 large rotational slides and lateral spreads followed by debris slides, earthflows, rotational and translational rockslides, complex slides and few large rock avalanches detached some 164 ± 56 km3 of material from the slopes of volcanic mesetas, lake-bounding moraines, and river-gorge walls. Many of these landslide deposits intersect with well-dated moraine ridges or former glacial-lake shorelines, and offer opportunities for relative dating of slope failure. We estimate that >60% of the landslide volume (∼96 km3) detached after the Last Glacial Maximum (LGM). Giant slope failures cross-cutting shorelines of a large Late Glacial to Early Holocene lake (“glacial lake PIS”) likely occurred during successive lake-level drop between ∼11.5 and 8 ka, and some of them are the largest hitherto documented landslides in moraines. We conclude that 1) large portions of terminal moraines can fail catastrophically several thousand years after emplacement; 2) slopes formed by weak bedrock or unconsolidated glacial deposits bordering glacial lakes can release extremely large landslides; and 3) landslides still occur in the piedmont, particularly along postglacial gorges cut in response to falling lake levels. KW - Quaternary KW - Landslide KW - Geomorphology KW - Relative dating KW - Glacier foreland KW - Glacial lake KW - Patagonian Ice Sheet KW - Paleogeography KW - South America Y1 - 2018 U6 - https://doi.org/10.1016/j.quascirev.2018.06.028 SN - 0277-3791 VL - 194 SP - 39 EP - 54 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Owen, Richard Bernhart A1 - Muiruri, Veronica M. A1 - Lowenstein, Tim K. A1 - Renaut, Robin W. A1 - Rabideaux, Nathan A1 - Luo, Shangde A1 - Deino, Alan L. A1 - Sier, Mark J. A1 - Dupont-Nivet, Guillaume A1 - McNulty, Emma P. A1 - Leet, Kennie A1 - Cohen, Andrew A1 - Campisano, Christopher A1 - Deocampo, Daniel A1 - Shen, Chuan-Chou A1 - Billingsley, Anne A1 - Mbuthia, Anthony T1 - Progressive aridification in East Africa over the last half million years and implications for human evolution JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Evidence for Quaternary climate change in East Africa has been derived from outcrops on land and lake cores and from marine dust, leaf wax, and pollen records. These data have previously been used to evaluate the impact of climate change on hominin evolution, but correlations have proved to be difficult, given poor data continuity and the great distances between marine cores and terrestrial basins where fossil evidence is located. Here, we present continental coring evidence for progressive aridification since about 575 thousand years before present (ka), based on Lake Magadi (Kenya) sediments. This long-term drying trend was interrupted by many wet-dry cycles, with the greatest variability developing during times of high eccentricity-modulated precession. Intense aridification apparent in the Magadi record took place between 525 and 400 ka, with relatively persistent arid conditions after 350 ka and through to the present. Arid conditions in the Magadi Basin coincide with the Mid-Brunhes Event and overlap with mammalian extinctions in the South Kenya Rift between 500 and 400 ka. The 525 to 400 ka arid phase developed in the South Kenya Rift between the period when the last Acheulean tools are reported (at about 500 ka) and before the appearance of Middle Stone Age artifacts (by about 320 ka). Our data suggest that increasing Middle- to Late-Pleistocene aridification and environmental variability may have been drivers in the physical and cultural evolution of Homo sapiens in East Africa. KW - Quaternary KW - paleoclimate KW - paleolimnology KW - hominins KW - Lake Magadi Y1 - 2018 U6 - https://doi.org/10.1073/pnas.1801357115 SN - 0027-8424 SN - 1091-6490 VL - 115 IS - 44 SP - 11174 EP - 11179 PB - National Academy of Sciences CY - Washington ER - TY - JOUR A1 - Berndt, Christopher A1 - Yildirim, Cengiz A1 - Ciner, Attila A1 - Strecker, Manfred A1 - Ertunc, Gulgun A1 - Sarikaya, M. Akif A1 - Özcan, Orkan A1 - Ozturk, Tugba A1 - Kiyak, Nafiye Gunec T1 - Quaternary uplift of the northern margin of the Central Anatolian Plateau BT - New OSL dates of fluvial and delta-terrace deposits of the Kizilirmak River, Black Sea coast, Turkey JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - We analysed the interplay between coastal uplift, sea level change in the Black Sea, and incision of the Kizilirmak River in northern Turkey. These processes have created multiple co-genetic fluvial and marine terrace sequences that serve as excellent strain markers to assess the ongoing evolution of the Pontide orogenic wedge and the growth of the northern margin of the Central Anatolian Plateau. We used high-resolution topographic data, OSL ages, and published information on past sea levels to analyse the spatiotemporal evolution of these terraces; we derived a regional uplift model for the northward advancing orogenic wedge that supports the notion of laterally variable uplift rates along the flanks of the Pontides. The best-fit uplift model defines a constant long-term uplift rate of 0.28 +/- 0.07 m/ka for the last 545 ka. This model explains the evolution of the terrace sequence in light of active tectonic processes and superposed cycles of climate-controlled sea-level change. Our new data reveal regional uplift characteristics that are comparable to the inner sectors of the Central Pontides; accordingly, the rate of uplift diminishes with increasing distance from the main strand of the restraining bend of the North Anatolian Fault Zone (NAFZ). This spatial relationship between the regional impact of the restraining bend of the NAFZ and uplift of the Pontide wedge thus suggests a strong link between the activity of the NAFZ, deformation and uplift in the Pontide orogenic wedge, and the sustained lateral growth of the Central Anatolian Plateau flank. (C) 2018 Elsevier Ltd. All rights reserved. KW - Quaternary KW - OSL dating KW - Black Sea KW - Pontides KW - North Anatolian Fault Zone KW - Orogenic wedge KW - Kizilirmak River KW - MIS KW - Turkey Y1 - 2018 U6 - https://doi.org/10.1016/j.quascirev.2018.10.029 SN - 0277-3791 VL - 201 SP - 446 EP - 469 PB - Elsevier CY - Oxford ER -