@article{YangDupontNivetJolivetetal.2015, author = {Yang, Wei and Dupont-Nivet, Guillaume and Jolivet, Marc and Guo, Zhaojie and Bougeois, Laurie and Bosboom, Roderic and Zhang, Ziya and Zhu, Bei and Heilbronn, Gloria}, title = {Magnetostratigraphic record of the early evolution of the southwestern Tian Shan foreland basin (Ulugqat area), interactions with Pamir indentation and India-Asia collision}, series = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, volume = {644}, journal = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-1951}, doi = {10.1016/j.tecto.2015.01.003}, pages = {122 -- 137}, year = {2015}, abstract = {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.}, language = {en} } @phdthesis{Stefer2009, author = {Stefer, Susanne}, title = {Late Pleistocene-Holocene sedimentary processes at the active margin of South-Central Chile : marine and lacustrine sediment records as archives of tectonics and climate variability}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-33731}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Active continental margins are affected by complex feedbacks between tectonic, climate and surface processes, the intricate relations of which are still a matter of discussion. The Chilean convergent margin, forming the outstanding Andean subduction orogen, constitutes an ideal natural laboratory for the investigation of climate, tectonics and their interactions. In order to study both processes, I examined marine and lacustrine sediments from different depositional environments on- and offshore the south-central Chilean coast (38-40°S). I combined sedimentological, geochemical and isotopical analyses to identify climatic and tectonic signals within the sedimentary records. The investigation of marine trench sediments (ODP Site 1232, SONNE core 50SL) focused on frequency changes of turbiditic event layers since the late Pleistocene. In the active margin setting of south-central Chile, these layers were considered to reflect periodically occurring earthquakes and to constitute an archive of the regional paleoseismicity. The new results indicate glacial-interglacial changes in turbidite frequencies during the last 140 kyr, with short recurrence times (~200 years) during glacial and long recurrence times (~1000 years) during interglacial periods. Hence, the generation of turbidites appears to be strongly influenced by climate and sea level changes, which control on the amount of sediment delivered to the shelf edge and therewith the stability of the continental slope: more stable slope conditions during interglacial periods entail lower turbidite frequencies than in glacial periods. Since glacial turbidite recurrence times are congruent with earthquake recurrence times derived from the historical record and other paleoseismic archives of the region, I concluded that only during cold stages the sediment availability and slope instability enabled the complete series of large earthquakes to be recorded. The sediment transport to the shelf region is not only driven by climate conditions but also influenced by local forearc tectonics. Accelerating uplift rates along major tectonic structures involved drainage anomalies and river flow inversions, which seriously altered the sediment supply to the Pacific Ocean. Two examples for the tectonic hindrance of fluvial systems are the coastal lakes Lago Lanalhue and Lago Lleu Lleu. Both lakes developed within former river valleys, which once discharged towards the Pacific and were dammed by tectonically uplifted sills at ~8000 yr BP. Analyses of sediment cores from the lakes showed similar successions of marine/brackish deposits at the bottom, covered by lacustrine sediments on top. Dating of the transitions between these different units and the comparison with global sea level curves allowed me to calculate local Holocene uplift rates, which are distinctly higher for the upraised sills (Lanalhue: 8.83 ± 2.7 mm/yr, Lleu Lleu: 11.36 ± 1.77 mm/yr) than for the lake basins (Lanalhue: 0.42 ± 0.71 mm/yr, Lleu Lleu: 0.49 ± 0.44 mm/yr). I hence considered the sills to be the surface expression of a blind thrust associated with a prominent inverse fault that is controlling regional uplift and folding. After the final separation of Lago Lanalhue and Lago Lleu Lleu from the Pacific, a constant deposition of lacustrine sediments preserved continuous records of local environmental changes. Sequences from both lakes indicate a long-term climate trend with a significant shift from more arid conditions during the Mid-Holocene (8000 - 4200 cal yr BP) to more humid conditions during the Late Holocene (4200 cal yr BP - present). This trend is consistent with other regional paleoclimatic data and interpreted to reflect changes in the strength/position of the Southern Westerly Winds. Since ~5000 years, sediments of Lago Lleu Lleu are marked by numerous intercalated detrital layers that recur with a mean frequency of ~210 years. Deposition of these layers may be triggered by local tectonics (i.e. earthquakes), but may also originate from changes in the local climate (e.g. onset of modern ENSO conditions). During the last 2000 years, pronounced variations in the terrigenous sediment supply to both lakes suggest important hydrological changes on the centennial time-scale as well. A lower input of terrigenous matter points to less humid phases between 200 cal yr B.C. - 150 cal yr A.D., 900 - 1350 cal yr A.D. and 1850 cal yr A.D. to present (broadly corresponding to the Roman, Medieval, and Modern Warm Periods). More humid periods persisted from 150 - 900 cal yr A.D. and 1350 - 1850 cal yr A.D. (broadly corresponding to the Dark Ages and the Little Ice Age). In conclusion, the combined investigation of marine and lacustrine sediments is a feasible method for the reconstruction of climatic and tectonic processes on different time scales. My approach allows exploring both climate and tectonics in one and the same archive, and is largely transferable to other active margins worldwide.}, language = {en} } @article{SmithFoxSchwanghartetal.2022, author = {Smith, Adam G. G. and Fox, Matthew and Schwanghart, Wolfgang and Carter, Andrew}, title = {Comparing methods for calculating channel steepness index}, series = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, volume = {227}, journal = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-8252}, doi = {10.1016/j.earscirev.2022.103970}, pages = {20}, year = {2022}, abstract = {Channel steepness index, k(s), is a metric derived from the stream power model that, under certain conditions, scales with relative rock uplift rate. Channel steepness index is a property of rivers, which can be relatively easily extracted from digital elevation models (DEMs). As DEM data sets are widely available for Earth and are becoming more readily available for other planetary bodies, channel steepness index represents a powerful tool for interpreting tectonic processes. However, multiple approaches to calculate channel steepness index exist. From this several important questions arise; does choice of approach change the values of channel steepness index, can values be so different that choice of approach can influence the findings of a study, and are certain approaches better than others? With the aid of a synthetic river profile and a case study from the Sierra Nevada, California, we show that values of channel steepness index vary over orders of magnitude according to the methodology used in the calculation. We explore the limitations, advantages and disadvantages of the key approaches to calculating channel steepness index, and find that choosing an appropriate approach relies on the context of a study. Given these observations, it is important that authors acknowledge the methodology used to calculate channel steepness index, to ensure that results can be contextualised and reproduced.}, language = {en} } @phdthesis{Rehak2008, author = {Rehak, Katrin}, title = {Pliocene-Pleistocene landscape evolution in south-central Chile : interactions between tectonic, geomorphic, and climatic processes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-19793}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Landscapes evolve in a complex interplay between climate and tectonics. Thus, the geomorphic characteristics of a landscape can only be understood if both, climatic and tectonic signals of past and ongoing processes can be identified. In order to evaluate the impact of both forcing factors it is crucial to quantify the evolution of geomorphic markers in natural environments. The Cenozoic Andes are an ideal setting to evaluate tectonic and climatic aspects of landscape evolution at different time and length scales in different natural compartments. The Andean Cordillera constitutes the type subduction orogen and is associated with the subduction of the oceanic Nazca Plate beneath the South American continent since at least 200 million years. In Chile and the adjacent regions this convergent margin is characterized by active tectonics, volcanism, and mountain building. Importantly, along the coast of Chile megathrust earthquakes occur frequently and influence landscape evolution. In fact, the largest earthquake ever recorded occurred in south-central Chile in 1960 and comprised a rupture zone of ~ 1000 km length. However, on longer time scales beyond historic documentation of seismicity it is not well known, how such seismotectonic segments have behaved and how they influence the geomorphic evolution of the coastal realms. With several semi-independent morphotectonic segments, recurrent megathrust earthquakes, and a plethora of geomorphic features indicating sustained tectonism, the margin of Chile is thus a key area to study relationships between surface processes and tectonics. In this study, I combined geomorphology, geochronology, sedimentology, and morphometry to quantify the Pliocene-Pleistocene landscape evolution of the tectonically active south-central Chile forearc. Thereby, I provide (1) new results about the influence of seismotectonic forearc segmentation on the geomorphic evolution and (2) new insights in the interaction between climate and tectonics with respect to the morphology of the Chilean forearc region. In particular, I show that the forearc is characterized by three long-term segments that are not correlated with short-lived earthquake-rupture zones that may. These segments are the Nahuelbuta, Tolt{\´e}n, and Bueno segments, each recording a distinct geomorphic and tectonic evolution. The Nahuelbuta and Bueno segments are undergoing active tectonic uplift. The long-term behavior of these two segments is manifested in form of two doubly plunging, growing antiforms that constitute an integral part of the Coastal Cordillera and record the uplift of marine and river terraces. In addition, these uplifting areas have caused major changes in flow directions or rivers. In contrast, the Tolt{\´e}n segment, situated between the two other segments, appears to be quasi-stable. In order to further quantify uplift and incision in the actively deforming Nahuelbuta segment, I dated an erosion surface and fluvial terraces in the Coastal Cordillera with cosmogenic 10Be and 26Al and optically stimulated luminescence, respectively. According to my results, late Pleistocene uplift rates corresponding to 0.88 mm a-1 are faster than surface-uplift rates averaging over the last 5 Ma, which are in the range of 0.21 mm a-1. This discrepancy suggests that surface uplift is highly variable in time and space and might preferably concentrate along reverse faults as indicated by a late Pleistocene flow reversal. In addition, the results of exposure dating with cosmogenic 10Be and 26Al indicate that the morphotectonic segmentation of this region of the forearc has been established in Pliocene time, coeval with the initiation of uplift of the Coastal Cordillera about 5 Ma ago, inferred to be related to a shift in subduction mode from erosion to accretion. Finally, I dated volcanic clasts obtained from alluvial surfaces in the Central Depression, a low-relief sector separating the Coastal from the Main Cordillera, with stable cosmogenic 3He and 21Ne, in order to reveal the controls of sediment accumulation in the forearc. My results document that these gently sloping surfaces have been deposited 150 to 300 ka ago. This deposition may be related to changes in the erosional regime during glacial episodes. Taken together, the data indicates that the overall geomorphic expression of the forearc is of post-Miocene age and may be intimately related to a climatic overprint of the tectonic system. This climatic forcing is also reflected in the topography and local relief of the Central and Southern Andes that vary considerably along the margin, determined by the dominant surface process that in turn is eventually controlled by climate. However, relief also partly reflects surface processes that have taken place under past climatic conditions. This emphasizes that due care has to be exercised when interpreting landscapes as mirrors of modern climates.}, language = {en} } @misc{MaslinBrierleyMilneretal.2014, author = {Maslin, Mark A. and Brierley, Chris M. and Milner, Alice M. and Shultz, Susanne and Trauth, Martin H. and Wilson, Katy E.}, title = {East African climate pulses and early human evolution}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {101}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2014.06.012}, pages = {1 -- 17}, year = {2014}, abstract = {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.}, language = {en} } @article{LoprienoBousquetBucheretal.2011, author = {Loprieno, Andrea and Bousquet, Romain and Bucher, Stefan and Ceriani, Stefano and Dalla Torre, Florian H. and F{\"u}genschuh, Bernhard and Schmid, Stefan M.}, title = {The valais units in Savoy (France) a key area for understanding the palaeogeography and the tectonic evolution of the Western Alps}, series = {International journal of earth sciences}, volume = {100}, journal = {International journal of earth sciences}, number = {5}, publisher = {Springer}, address = {New York}, issn = {1437-3254}, doi = {10.1007/s00531-010-0595-1}, pages = {963 -- 992}, year = {2011}, abstract = {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.}, language = {en} } @article{KoberZeilingerIvyOchsetal.2013, author = {Kober, Florian and Zeilinger, Gerald and Ivy-Ochs, Susan and Dolati, A. and Smit, J. and Kubik, Peter W.}, title = {Climatic and tectonic control on fluvial and alluvial fan sequence formation in the Central Makran Range, SE-Iran}, series = {Global and planetary change}, volume = {111}, journal = {Global and planetary change}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0921-8181}, doi = {10.1016/j.gloplacha.2013.09.003}, pages = {133 -- 149}, year = {2013}, abstract = {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.}, language = {en} }