TY - JOUR A1 - Yang, Wei A1 - Dupont-Nivet, Guillaume A1 - Jolivet, Marc A1 - Guo, Zhaojie A1 - Bougeois, Laurie A1 - Bosboom, Roderic A1 - Zhang, Ziya A1 - Zhu, Bei A1 - Heilbronn, Gloria T1 - Magnetostratigraphic record of the early evolution of the southwestern Tian Shan foreland basin (Ulugqat area), interactions with Pamir indentation and India-Asia collision JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - The Tian Shan range is an inherited intracontinental structure reactivated by the far-field effects of the India-Asia collision. A growing body of thermochronology and magnetostratigraphy datasets shows that the range grew through several tectonic pulses since similar to 25 Ma, however the early Cenozoic history remains poorly constrained. The time-lag between the Eocene India-Asia collision and the Miocene onset of Tian Shan exhumation is particularly enigmatic. This peculiar period is potentially recorded along the southwestern Tian Shan piedmont. There, late Eocene marine deposits of the proto-Paratethys epicontinental sea transition to continental foreland basin sediments of unknown age were recently dated. We provide magnetostratigraphic dating of these continental sediments from the 1700-m-thick Mine section integrated with previously published detrital apatite fission track and U/Pb zircon ages. The most likely correlation to the geomagnetic polarity time scale indicates an age span from 20.8 to 13.3 Ma with a marked increase in accumulation rates at 19-18 Ma. This implies that the entire Oligocene period is missing between the last marine and first continental sediments, as suggested by previous southwestern Tian Shan results. This differs from the southwestern Tarim basin where Eocene marine deposits are continuously overlain by late Eocene-Oligocene continental sediments. This supports a simple evolution model of the western Tarim basin with Eocene-Oligocene foreland basin activation to the south related to northward thrusting of the Kunlun Shan, followed by early Miocene activation of northern foreland basin related to overthrusting of the south Tian Shan. Our data also support southward propagation of the Tian Shan piedmont from 20 to 18 Ma that may relate to motion on the Talas Fergana Fault. The coeval activation of a major right-lateral strike-slip system allowing indentation of the Pamir Salient into the Tarim basin, suggests far-field deformation from the India-Asia collision zone affected the Tian Shan and the Talas Fergana fault by early Miocene. (C) 2015 Elsevier B.V. All rights reserved. KW - Magnetostratigraphy KW - Cenozoic KW - Tian Shan KW - Pamir KW - Tarim Basin KW - Tectonics Y1 - 2015 U6 - https://doi.org/10.1016/j.tecto.2015.01.003 SN - 0040-1951 SN - 1879-3266 VL - 644 SP - 122 EP - 137 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Maslin, Mark A. A1 - Brierley, Chris M. A1 - Milner, Alice M. A1 - Shultz, Susanne A1 - Trauth, Martin H. A1 - Wilson, Katy E. T1 - East African climate pulses and early human evolution JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Current evidence suggests that all of the major events in hominin evolution have occurred in East Africa. Over the last two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of East Africa has varied in the past. The landscape of East Africa has altered dramatically over the last 10 million years. It has changed from a relatively flat, homogenous region covered with mixed tropical forest, to a varied and heterogeneous environment, with mountains over 4 km high and vegetation ranging from desert to cloud forest. The progressive rifting of East Africa has also generated numerous lake basins, which are highly sensitive to changes in the local precipitation-evaporation regime. There is now evidence that the presence of precession-driven, ephemeral deep-water lakes in East Africa were concurrent with major events in hominin evolution. It seems the unusual geology and climate of East Africa created periods of highly variable local climate, which, it has been suggested could have driven hominin speciation, encephalisation and dispersal out of Africa. One example is the significant hominin speciation and brain expansion event at -1.8 Ma that seems to have been coeval with the occurrence of highly variable, extensive, deep-water lakes. This complex, climatically very variable setting inspired first the variability selection hypothesis, which was then the basis for the pulsed climate variability hypothesis. The newer of the two suggests that the long-term drying trend in East Africa was punctuated by episodes of short, alternating periods of extreme humidity and aridity. Both hypotheses, together with other key theories of climate-evolution linkages, are discussed in this paper. Though useful the actual evolution mechanisms, which led to early hominins are still unclear and continue to be debated. However, it is clear that an understanding of East African lakes and their palaeoclimate history is required to understand the context within which humans evolved and eventually left East Africa. (C) 2014 The Authors. Published by Elsevier Ltd. KW - Human evolution KW - East Africa KW - Palaeoclimatology KW - Palaeoliminology KW - Tectonics KW - Hominin KW - Orbital forcing KW - Cenozoic climate transitions KW - Pulsed climate variability hypothesis Y1 - 2014 U6 - https://doi.org/10.1016/j.quascirev.2014.06.012 SN - 0277-3791 VL - 101 SP - 1 EP - 17 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Loprieno, Andrea A1 - Bousquet, Romain A1 - Bucher, Stefan A1 - Ceriani, Stefano A1 - Dalla Torre, Florian H. A1 - Fügenschuh, Bernhard A1 - Schmid, Stefan M. T1 - The valais units in Savoy (France) a key area for understanding the palaeogeography and the tectonic evolution of the Western Alps JF - International journal of earth sciences N2 - The Valais units in Savoy (Zone des BrSches de Tarentaise) have been re-mapped in great detail and are subject of combined stratigraphic, structural and petrological investigations summarized in this contribution. The sediments and rare relics of basement, together with Cretaceous age mafic and ultramafic rocks of the Valais palaeogeographical domain, represent the heavily deformed relics of the former distal European margin (External Valais units) and an ocean-continent transition (Internal Valais unit or Versoyen unit) that formed during rifting. This rifting led to the opening of the Valais ocean, a northern branch of the Alpine Tethys. Post-rift sediments referred to as "Valais trilogy" stratigraphically overlie both External and Internal Valais successions above an angular unconformity formed in Barremian to Aptian times, providing robust evidence for the timing of the opening of the Valais ocean. The Valais units in Savoy are part of a second and more external mid-Eocene high-pressure belt in the Alps that sutured the Brian double dagger onnais microcontinent to Europe. Top-N D1-deformation led to the formation of a nappe stack that emplaced the largely eclogite-facies Internal Valais unit (Versoyen) onto blueschist-facies External Valais units. The latter originally consisted of, from internal to external, the Petit St. Bernard unit, the Roc de l'Enfer unit, the MoA >> tiers unit and the Quermoz unit. Ongoing top-N D2-thrusting and folding substantially modified this nappe stack. Post 35 Ma D3 folding led to relatively minor modifications of the nappe stack within the Valais units but was associated with substantial top-WNW thrusting of the Valais units over the Dauphinois units along the Roselend thrust during W-directed indentation of the Adria block contributing to the formation of the arc of the Western Alps. KW - Alpine geology KW - Valais ocean KW - Palaeogeography KW - Structural geology KW - Tectonics KW - Metamorphism Y1 - 2011 U6 - https://doi.org/10.1007/s00531-010-0595-1 SN - 1437-3254 VL - 100 IS - 5 SP - 963 EP - 992 PB - Springer CY - New York ER - TY - JOUR A1 - Kober, Florian A1 - Zeilinger, Gerald A1 - Ivy-Ochs, Susan A1 - Dolati, A. A1 - Smit, J. A1 - Kubik, Peter W. T1 - Climatic and tectonic control on fluvial and alluvial fan sequence formation in the Central Makran Range, SE-Iran JF - Global and planetary change N2 - The geomorphic evolution of the Makran Range of SE-Iran and SW-Pakistan has been controlled by the prevailing SW-Asian monsoon and Mediterranean winter rainfall climate and the surface uplift processes resulting from the Arabia-Eurasia collision. The impact of climate on Quaternary fluvial and alluvial sequence formation and their regional correlation has been little investigated due to limited age control of these sequences. Using Be-10 cosmogenic nuclide exposure ages we established a Middle to Late Pleistocene terrace chronology. Our record tentatively indicates that terrace levels were abandoned towards the transition to or during warmer/pluvial periods (interglacials and/or interstadials) back to Marine Isotope Stage (MIS) 7, but abandoned ages show a large spread. It is hypothesized that pluvial phases correspond with times of enhanced SW-monsoons and a northward shift of the Intertropical Convergence Zone (ITCZ). Furthermore, orbital periodidties can be deduced on frequencies related to obliquity and precession cycles. Overall, caution has to be placed in sampling and interpreting alluvial deposits, which may have complex inheritance patterns and spatially and temporarily variable catchment erosion histories and terrace-channel dynamics. Beside the dominant climate control on terrace formation, elevated channel steepness indices around major thrusts and numerous knickpoints indicate an additionally tectonic influence on terrace formation. Local incision rates (mean similar to 0.6-0.8 min.a(-1)) are variable in space and time but are similar to uplift rates obtained from coastal terraces and thus suggest a regional surface uplift. (C) 2013 Elsevier B.V. All rights reserved. KW - Cosmogenic nuclides KW - Monsoon KW - Climate KW - Tectonics KW - Terraces KW - Makran Y1 - 2013 U6 - https://doi.org/10.1016/j.gloplacha.2013.09.003 SN - 0921-8181 SN - 1872-6364 VL - 111 SP - 133 EP - 149 PB - Elsevier CY - Amsterdam ER -