N. Akçar

N. Akçar
Universität Bern | UniBe · Institute of Geological Sciences

PD Dr.

About

181
Publications
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2,536
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Additional affiliations
August 1995 - August 1998
Middle East Technical University
Position
  • Research Assistant

Publications

Publications (181)
Article
Cut-and-fill sequences are the result of climatically or tectonically induced alternating aggradation and incision phases of a fluvial system. A recently established cosmogenic nuclide chronology of the Cover Gravels ( Deckenschotter in German) in the northern Alpine Foreland, which are the oldest Quaternary glaciofluvial gravels and comprise evide...
Article
Full-text available
In this paper, we document that glaciofluvial gravel sequences and glacial till deposits that are exposed in the Müntschemier and Finsterhennen gravel pits (Swiss Plateau west of Bern) record three glacial advances during the Birrfeld Glaciation, which corresponds to the last glacial cycle. Sedimentological logging shows that both gravel pits expos...
Article
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Disentangling the influence of lithology from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial and temporal scales involved. The Dora Baltea catchment (western Italian Alps) is an ideal setting...
Article
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Tropical mountains and highlands in Africa are under pressure because of anthropogenic climate and land-use change. To determine the impacts on the afro-alpine environment and to assess the potential socio-economic consequences, the monitoring of essential climate and environmental variables at high elevation is fundamental. However, long-term temp...
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We present a new glacier chronology from one of the major end moraine systems of the Southern Alps. Timing and extent of the Last Glacial Maximum (LGM) advance of the Ticino-Toce glacier were reconstructed in detail based on landform relationships and surface exposure dating. ¹⁰Be and ³⁶Cl ages from 41 erratic boulders constrain the last maximum of...
Article
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Western Anatolia is one of the most seismically active regions worldwide. To date, the paleoseismic history of many major faults, in terms of recurrence intervals of destructive earthquakes, their magnitude, displacement, and slip rates is poorly understood. Regional crustal extension has produced major horst-graben systems bounded by kilometer-sca...
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Mid-latitude mountain glaciers are sensitive to local summer temperature changes. Chronologies of past glacier fluctuations based on the investigation of glacial landforms therefore allow for a better understanding of natural climate variability at local scale, which is relevant for the assessment of the ongoing anthropogenic climate warming. In th...
Article
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Previous research suggested that the Alpine glaciers of the Northern Swiss Foreland reached their maximum extensive position during the Middle Pleistocene. Relict tills and glaciofluvial deposits, attributed to the Most Extensive Glaciation (MEG), have been found only beyond the extents of the Last Glacial Maximum (LGM). Traditionally, these sedime...
Chapter
Almost 180 years of research revealed that the glaciers expanded in the valleys of 36 mountains in Anatolia during the Last Glacial Maximum (LGM). Today, glacial landforms are found in the Eastern Black Sea Mountains, Western Taurus Mountains, Central Taurus Mountains, Eastern Taurus, Eastern Anatolian Mountains, and in Northwestern and Central Ana...
Chapter
Evidence for glacial advances in the Anatolian mountains prior to the Last Glacial Cycle (LGC) are unknown. Oldest known glacial advances date back to pre-LGM (Last Glacial Maximum) within the LGC. Glacial landforms and deposits related to the pre-LGM advances are found in the Eastern Black Sea Mountains, Western Taurus Mountains, and Northwestern...
Chapter
Anatolia is the largest mountain landscape in the Eastern Mediterranean region between 36°–42°N and 26°–45°E. Its topography is controlled by the Eastern Black Sea Mountains in the north, the Taurus Mountains in the south, the Eastern Anatolian Mountains in the east, and by solitary mountains. Today, only the highest peaks of the Eastern Black Sea...
Preprint
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Disentangling the influence of bedrock erodibility from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial/temporal scales involved. The Dora Baltea catchment (western Italian Alps) appears the i...
Article
Full-text available
This study reports on the cosmogenic 36Cl dating of two normal fault scarps in western Turkey, that of the Manastır and Mugırtepe faults, beyond existing historical records. These faults are elements of the western Manisa Fault Zone (MFZ) in the seismically active Gediz Graben. Our modeling revealed that the Manastır fault underwent at least two su...
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Quantifying bedrock weathering rates under diverse climate conditions is essential to understanding timescales of landscape evolution. Yet, weathering rates are often difficult to constrain, and associating a weathered landform to a specific formative environment can be complicated by overprinting of successive processes and temporally varying clim...
Preprint
Full-text available
Mid-latitude mountain glaciers sensitively respond to local summer temperature changes. Chronologies of past glacier fluctuations based on the investigation of glacial landforms therefore allows for a better understanding of warm-season climate variability at local scale. In this study, we focus on the Holocene, the current interglacial of the last...
Article
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We used concentrations of in situ cosmogenic 10 Be from riverine sediment to quantify the basin-averaged denudation rates and sediment fluxes in the Plessur Basin, Eastern Swiss Alps, which is a tributary stream to the Alpine Rhine, one of the largest streams in Europe. We complement the cosmogenic dataset with the results of morphometric analyses,...
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Large forms of sorted patterned ground belong to the most prominent geomorphic features of periglacial and permafrost environments of the mid-latitudes and polar regions, but they were hitherto unknown in the tropics. Here, we report on relict large sorted stone stripes (up to 1000 m long, 15 m wide, and 2 m deep) on the ca. 4000 m high central San...
Conference Paper
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Rock fall processes of various size and magnitude control retreat rates of high alpine rock-walls. For millennial time scales, these retreat rates can be quantified in-situ from concentrations of cosmogenic nuclides along bedrock depth profiles (Mair et al., 2019). We measured cosmogenic 36Cl and 10Be along several such profiles at Mt Eiger in the...
Article
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Today’s ice caps and glaciers in Africa are restricted to the highest peaks, but during the Pleistocene, several mountains on the continent were extensively glaciated. However, little is known about regional differences in the timing and extent of past glaciations and the impact of paleoclimatic changes on the afro-alpine environment and settlement...
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The Arp Nouva peat bog located in the upper Ferret Valley in the Mont Blanc massif was critically evaluated since published radiocarbon dates have led to controversial conclusions on the formation of this swamp. Radiocarbon dating of woody fragments from three pits of up to 1 m depth was used to discuss the question of whether the historically docu...
Chapter
The evolution of the Swiss landscape during the Quaternary Period over the past 2.6 million years is controlled by multiple glaciations and deglaciations with at least 15 drastic environmental changes between glacier advances (with yearly average temperatures of –16° compared with today) and warm phases (with yearly average temperatures of +2° comp...
Article
During the Last Glacial Maximum, the coast of Finnmark county, northern Norway, was covered by the Scandinavian Ice Sheet (SIS), which coalesced with the Barents Sea Ice Sheet (BSIS) off the coast. The region is thus important for our understanding of the dynamic interactions between the BSIS and the SIS, yet it remains one of the least dated regio...
Article
The volcanic island of Jan Mayen, remotely located in the Norwegian‐Greenland Sea, was covered by a contiguous ice cap during the Late Weichselian. Until now, it has been disputed whether parts of the island south of the presently glaciated Mount Beerenberg area were ever glaciated. Based on extensive field mapping we demonstrate that an ice cap co...
Article
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We compile detrital 10 Be concentrations of Alpine rivers, representing the denudation rates pattern for 375 catchments across the entire European Alps. Using a homogeneized framework, we employ state-of-the-art techniques for inverting in-situ 10 Be concentrations into denudation rates. From our compilation, we find that (i) while lithologic prope...
Article
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Large rock-slope failures are among the primary geohazards in high mountain areas. These rock avalanches and rockslides constitute most of the world’s largest landslide deposits. This study focuses on the formation and geomorphological activity of the Akdag landslide complex located on the southern slope of Mount Akdag, SW Turkey. We employed detai...
Article
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Denudation of steep rockwalls is driven by rock fall processes of various sizes and magnitudes. Rockwalls are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, which can precondition the occurrence of rock fall. However, it is still unclear how the fracturing of rock together with cryogeni...
Preprint
Full-text available
Large sorted patterned grounds are the most prominent features of periglacial and permafrost environments of the mid and high latitudes, but have not yet been verified for the tropics. Here, we report on relict large sorted polygons (up to 8 m in diameter) and large sorted stone stripes (up to 1000 m long, 15 m wide, and 2 m deep) on the ~ 4000 m h...
Article
Full-text available
Blue ice moraines are common supraglacial landforms in Antarctica and they are considered to record the ice volume fluctuations. In this study, we use photogrammetry and the analysis of multiple cosmogenic nuclides (¹⁰Be, ²⁶Al, and in-situ ¹⁴C) in boulders on three blue ice moraines to explore the timing of ice volume fluctuations in the Sør Rondan...
Conference Paper
Full-text available
The Bale Mountains in the southern Ethiopian Highlands (7-8°N) are formed of multiple superimposed flood basalts and comprise Africa's largest plateau above 4000 m. Glacial and periglacial landforms are well-preserved and facilitate the reconstruction of the paleoclimate and landscape of the afro-alpine environment. During the Late Pleistocene, an...
Article
Controversy remains over when present-day configuration of the Anatolia boundary faults came into existence, and the issue of what are the driving forces of the Anatolian westward motion. The NW-striking dextral and NE-striking sinistral second-order strike-slip faults at the eastern part of the Anatolian Scholle play a crucial role within these lo...
Article
In this study, we focus on the Kandersteg rock avalanche in the central Bernese Alps in Switzerland. We achieved an improved understanding of the release and emplacement of the rock avalanche through a combination of detailed field mapping, remote image analysis, reconstruction of deposit and source area volumes, and runout modelling with DAN3D. Ba...
Preprint
Full-text available
Abstract. Denudation of steep headwalls is driven by rock fall processes of various size and magnitude. They are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, thus pre-conditioning rock fall. However, these controls and conditions thereof on the denudation processes operating on steep...
Article
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We publish a MATLAB code used to analyze concentration profile of cosmogenic 36Cl accumulated in-situ through a rupture history of the fault scarps in western Turkey (Mozafari et al., 2019). The code is a version of the forward modeling Matlab code -Fault Scarp Dating Tool- (Tikhomirov, 2014). The code models a 36Cl profile accumulated in the fault...
Article
This paper focuses on the Landquart drainage basin, where we explore geomorphic signals related to the spatial differences in bedrock lithology and differential uplift. We use concentrations of cosmogenic ¹⁰Be to quantify the sediment flux patterns in the region. Furthermore we use the chemical composition of the fine fraction (< 63 μm) of the rive...
Article
Studies of early human settlement in alpine environments provide insights into human physiological, genetic, and cultural adaptation potentials. Although Late and even Middle Pleistocene human presence has been recently documented on the Tibetan Plateau, little is known regarding the nature and context of early persistent human settlement in high e...
Article
Full-text available
Quantifications of in-situ denudation rates on vertical headwalls, averaged over millennia, have been thwarted because of inaccessibility. Here, we benefit from a tunnel crossing a large and vertical headwall in the European Alps (Eiger), where we measured concentrations of in-situ cosmogenic 36Cl along five depth profiles linking the tunnel with t...
Article
Full-text available
Fault scarps, if well-preserved, include precise evidence of past earthquakes. Using cosmogenic 36 Cl dating, the timing and slip of paleoearthquakes are recoverable beyond the available earthquake archives. One of the appropriate seismically active regions to apply 36 Cl dating is western Anatolia, where its deformation is influenced by an N-S ext...
Article
The northern Swiss Alpine Foreland exemplifies a highly transient landscape characterized by multiple knickzones along the trunk valleys and distinct bedrock straths at their junction with tributary valleys. This landscape has evolved as a result of fast base level changes in response to repeated glaciations during the Quaternary. As the archives r...
Article
There is growing interest in geochronological applications of terrestrial in situ-produced cosmogenic nuclides, with the most commonly measured being ¹⁰ Be and ²⁶ Al in quartz. To extract and then separate these radionuclides from quartz and prepare them in the oxide form suitable for accelerator mass spectrometry (AMS) requires extensive and caref...
Article
Full-text available
Determining sediment transfer times is key to understanding source‐to‐sink dynamics and the transmission of environmental signals through the fluvial system. Previous work on the Bolivian Altiplano applied the in situ cosmogenic ¹⁴C‐¹⁰Be‐chronometer to river sands and proposed sediment storage times of ~10–20 kyr in four catchments southeast of Lak...
Preprint
Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparisonmaterial (ICM) for in situ-produced cosmogenic 36Cl and natural chlorine (Clnat) analysis. The sample CoCal-N isderived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystalof alkali-feldspar...
Article
Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparison material (ICM) for in situ-produced cosmogenic ³⁶Cl and natural chlorine (Clnat) analysis. The sample CoCal-N is derived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystal of alkali-felds...
Conference Paper
Full-text available
As Turkey is located in the Alpine-Himalayan mountain belt, it has a mountainous landscape with ranges extending parallel to the coast in the north and south. This landscape causes moist air masses to leave precipitation mostly in the coastal regions. Therefore, the central parts of Turkey have lower precipitation compared to the coast, and the con...
Article
Full-text available
Sediment accumulation can occur in response to a change in either tectonic or climatic driving forces. Here, we explore these controls on the deposition of the Lima Conglomerate, Peru. We use a combination of quantitative methods to explore the age of sediment accumulation, the provenance of the material and the paleo‐erosion rates recorded by thes...
Article
Full-text available
The incision and aggradation of the Pativilca alluvial fan delta system in the western Peruvian Andes through Quaternary time can be traced in detail using well-exposed fill terraces studied by a combination of cosmogenic nuclide dating, terrace mapping and paleo-erosion rate calculations. Two alluvial terraces have been dated through depth-profile...
Article
Full-text available
9 The incision and aggradation of the Pativilca alluvial fan delta system in the western Peruvian 10 Andes through Quaternary time can be traced in detail using well-exposed fill terraces studied by a 11 combination of cosmogenic nuclide dating, terrace mapping and paleo-erosion rate calculations. Two 12 alluvial terraces have been dated through de...
Article
In parallel with increases in the global ice volume during the cold periods of the Quaternary, which is characterized by warm and cold climate cycles, glaciers developed in parts of the Eastern Black Sea Mountains, Taurus Mountains, and some high mountains in Eastern Anatolia with appropriate conditions. The Kavuşşahap Mountains, which are one of t...
Conference Paper
Full-text available
The Malatya-Ovacık Fault Zone (MOFZ) is about 270 km-long sinistral strike-slip tectonic structure within the Anatolian Scholle. This zone has a key role in evaluating the initiation and style of the deformation within the Anatolian Scholle. Although the MOFZ is claimed to be an inactive structure since 3 Ma or 4 Ma in some previous studies, recent...
Article
Our new dataset from the Rivoli‐Avigliana end‐moraine system, the westernmost amphitheatre of the Italian Alps, provides an important step towards understanding foreland‐reaching glaciations before and during the Last Glacial Maximum (LGM) in the Western Alps. 10Be data from six boulders in pre‐LGM deposits gave ages between 26.8 ± 2.1 and 41.2 ± 1...
Article
Full-text available
Terrestrial cosmogenic nuclide concentrations of detrital minerals yield catchment-wide rates at which hillslopes erode. These estimates are commonly used to infer millennial scale denudation patterns and to identify the main controls on mass-balance and landscape evolution at orogenic scale. The same approach can be applied to minerals preserved i...
Conference Paper
The Twannberg meteorite strewn field and its relation with Quaternary sediments
Article
We report results from a comprehensive surface exposure dating campaign in eastern Finnmark, located in the northernmost part of Norway and close to the Norwegian-Russian border. This is a palaeo-glaciologically important region as it sits near the proposed border-zone between the former Scandinavian and Barents Sea Ice Sheets. However, until now t...
Article
Alpine water and sediment supply influence the sediment budget of many important European fluvial systems such as the Rhine, Rhône and Po rivers. In the light of human induced climate change and landscape modification, it becomes increasingly important to understand the mechanisms of sediment production and supply in Alpine sediment systems. This s...
Conference Paper
Full-text available
During the cold periods in Quaternary, equilibrium-line altitude (ELA) decreased which caused valley glaciers to advance. To the contrary, the tongues of glaciers retreated during the warm periods. Quaternary glacier fluctuations were also recorded from Turkish mountains. Recently, the chronology of Late Quaternary advances in the northern and west...
Conference Paper
Full-text available
The evidence of paleoglaciers provides important information of past climate changes. Especially, mountain glaciers are very sensitive indicators of changes of temperature and precipitation. Depending on changes in atmospheric circulation systems in the Late Quaternary, glaciers have advanced and retreated many times. During cold periods equilibriu...