Glaciations and paleoclimate of Mount Erciyes,central Turkey,since the Last Glacial Maximum,inferred from 36Cl cosmogenic dating and glacier modeling     

Mehmet Akif Sarıkaya  Marek Zreda  Attila Çiner 《Quaternary Science Reviews》2009,28(23-24):2326-2341

Forty-four boulders from moraines in two glacial valleys of Mount Erciyes (38.53°N, 35.45°E, 3917 m), central Turkey, dated with cosmogenic chlorine-36 (³⁶Cl), indicate four periods of glacial activity in the past 22 ka (1 ka = 1000 calendar years). Last Glacial Maximum (LGM) glaciers were the most extensive, reaching 6 km in length and descending to an altitude of 2150 m above sea level. These glaciers started retreating 21.3 ± 0.9 ka (1σ) ago. They readvanced and retreated by 14.6 ± 1.2 ka ago (Lateglacial), and again by 9.3 ± 0.5 ka ago (Early Holocene). The latest advance took place 3.8 ± 0.4 ka ago (Late Holocene). Using glacier modeling together with paleoclimate proxy data from the region, we reconstructed the paleoclimate at these four discrete times. The results show that LGM climate was 8–11 °C colder than today and moisture levels were somewhat similar to modern values, with a range between 20% more and 25% less than today. The analysis of Lateglacial advance suggests that the climate was colder by 4.5–6.4 °C based on up to 1.5 times wetter conditions. The Early Holocene was 2.1–4.9 °C colder and up to twice as wet as today, while the Late Holocene was 2.4–3 °C colder and its precipitation amounts approached to similar conditions as today. Our paleoclimate reconstructions show a general trend of warming for the last 22 ka, and an increase of moisture until Early Holocene, and a decrease after that time. The recent glacier terminates at 3450 m on the northwest side of the mountain. It is a remnant from the last advance (possibly during the Little Ice Age). Repeated measurements of glacier length between 1902 and 2008 reveal a retreat rate of 4.2 m per year, which corresponds to a warming rate of 0.9–1.2 °C per century.  相似文献   

Multi-stage hydrothermal processes involved in “low-sulfide” Cu(–Ni)–PGE mineralization in the footwall of the Sudbury Igneous Complex (Canada): Amy Lake PGE zone, East Range     

Györgyi Tuba  Ferenc Molnár  Doreen E. Ames  Attila Péntek  David H. Watkinson  Peter C. Jones 《Mineralium Deposita》2014,49(1):7-47

The Amy Lake PGE zone is a “low-sulfide-type” Cu-(Ni-)PGE mineralization in the East Range footwall of the 1.85 Ga Sudbury Igneous Complex occurring in a 100-m-wide Sudbury Breccia belt that coincides with an impact-related major fracture zone (Bay Fault zone). Detailed hydrothermal alteration mapping, fluid inclusion, trace element, and stable isotope studies revealed a complex alteration and mineralization history in a multi-source, multi-stage Sudbury-related hydrothermal system. The two major stages of syn-Sudbury hydrothermal activity are characterized by similarly high-salinity, high-temperature fluids that are (1) locally derived from footwall granophyre bodies, and typified with high Ni/Cu and PGE/S ratios and high REE contents (magmatic–hydrothermal stage), and (2) a more voluminous Cu–Ni–PGE-rich fluid flux probably originated from the Sudbury Igneous Complex/footwall contact (hydrothermal stage). The second hydrothermal flux was introduced by brittle fractures in the area and resulted in a complex zonation of alteration assemblages and mineralization governed by local footwall composition. The Sudbury-related hydrothermal event was overprinted by shear-related epidote veining and calcite–chlorite replacement, both regionally present in the Sudbury structure. Based on analogies, the most important factors involved in the formation of hydrothermal low-sulfide mineralization are proposed to be (1) accumulation of PGE-enriched fluids, (2) large-scale brittle structures as conduits to these fluids, and (3) adequate host rock composition as a chemical trap resulting in sulfide and PGM precipitation. In environments meeting these criteria, hydrothermal PGE mineralization is known to have formed not only in the Sudbury footwall but also from mafic–ultramafic intrusions associated with primary magmatic PGE from several locations around the world.  相似文献   

A continuum mechanics‐based framework for boundary and finite element mesh optimization in two dimensions for application in excavation analysis     

Attila M. Zski  John H. Curran 《国际地质力学数值与分析法杂志》2005,29(4):369-393

The determination of the optimum excavation sequences in mining and civil engineering using numerical stress analysis procedures requires repeated solution of large models. Often such models contain much more complexity and geometric detail than required to arrive at an accurate stress analysis solution, especially considering our limited knowledge of rock mass properties. This paper develops an automated framework for estimating the effects of excavations at a region of interest, and optimizing the geometry used for stress analysis. It eliminates or simplifies the excavations in a model while maintaining the accuracy of analysis results. The framework can equally be applied to two‐dimensional boundary and finite element models. The framework will have the largest impact for non‐linear finite element analysis. It can significantly reduce computational times for such analysis by simplifying models. Error estimators are used in the framework to assess accuracy. The advantages of applying the framework are demonstrated on an excavation‐sequencing scenario. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

A continuum mechanics‐based framework for optimizing boundary and finite element meshes associated with underground excavations‐framework     

Attila M. Zski  John H. Curran 《国际地质力学数值与分析法杂志》2005,29(13):1271-1298

Many field problems, from stress analysis, heat transfer to contaminant transport, deal with disturbances in a continuum caused by a ‘source’ (defined by its discrete geometry) and a ‘region of interest’ (where a solution is sought). Depending on the location of ‘regions of interest’ in relation to the ‘sources’, the level of geometric detail necessary to represent the ‘sources’ in a model can vary considerably. A practical application of stress analysis in mining is the evaluation of the effects of continuous excavation on the states of stress around mine openings. Labour intensive model preparation and lengthy computation coupled with the interpretation of analysis results can have considerable impact on the successful operation of an underground mine, where stope failures can cost tens of millions of dollars and possibly lead to closure of the mine. A framework is proposed based on continuum mechanics principles to automatically optimize the level of geometric detail required for an analysis by simplifying the model geometry using expanded and modified algorithms that originated in computer graphics. This reduction in model size directly translates to savings in computational time. The results obtained from an optimized model have accuracy comparable to the uncertainty in input data (e.g. rock mass properties, geology, etc.). This first paper defines the optimization framework, while a companion paper investigates its efficiency and application to practical mining and excavation‐related problems. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

An experimental confirmation of the gravitons?     

Attila Mészáros 《Astrophysics and Space Science》1989,158(2):353-355

If the gravity is not quantized and the metric tensor is a classical quantity, the contortion should exist, and exert empirically measurable effects—at least in principle. On the other hand, it is likely that the existence of gravitons leads to the non-existence of contortion.  相似文献   

Comments on “Monitoring soil erosion in Cappadocia region (Selime–Aksaray–Turkey)” by Yilmaz et al. (Environ Earth Sci 2012, 66:75–81)     

Attila Çiner  Mehmet Akif Sarıkaya  Erkan Aydar 《Environmental Earth Sciences》2013,70(4):1927-1931

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The online TÉKA database,an integrated approach to landmark inventorization     

László Kollányi  Attila Csemez  Sándor Jombach  Zsolt Szilvácsku 《国际地球制图》2013,28(1):80-94

The reduction of untouched areas and the increase in residential, agricultural and industrial areas have gained speed in recent decades. As a result of the changes, one can often observe the disappearance of landmarks that had been connected to production, habitation and transportation. The first step for the preservation of landmarks is their identification and inventorization. In the ordinary sense of the word, ‘landmarks’ mean the important landscape heritage of national history and culture, which need to be identified, protected and preserved for future generations. The purpose of the TÉKA project was to compile a landmark cadastral register that will contribute to the preservation of landscape-related and cultural heritage in Hungary. The landmark cadastral is a Wikipedia-like GIS-based web site. One of the novelties of the TÉKA database is that the data obtained from various sources are gathered in a common, online GIS and integrated into a uniform meta database.  相似文献   

OSL-dating the Quaternary landscape evolution in the Vértes Hills forelands (Hungary)     

Edit Thamó-Bozsó  Gábor Csillag  László I. Fodor  Pál M. Müller  Attila Nagy 《Quaternary Geochronology》2010,5(2-3):120-124

Fluvial, colluvial, and aeolian sediments were dated by optically stimulated luminescence (OSL) on quartz to improve the chronological framework for Quaternary sedimentation and landscape evolution in the forelands of the Vértes Hills (central Hungary). The separated quartz was suitable for age determination based on an OSL SAR protocol. Most samples have asymmetric equivalent dose distributions and OSL ages were calculated by the mean, central, and minimum D_e values. Considering geomorphology and earlier age data from the area, the central D_e values seem most appropriate for age calculation. A fan on the geomorphological level QV in the western foreland of the Vértes Hills was deposited 79–75 (±8) ka ago. In the south-eastern foreland an alluvial fan on level QIIb is at most 42 ± 4 ka old. Fluvial incision and aggradation occurred 16–10 (±1) ka ago on the geomorphic surface QIIa. Loess is 14 ± 1 ka old, and slope sedimentation was active 11–9 (±1) ka ago. Our OSL data demonstrate that in the north-western foreland of the Vértes Hills wind remained an important agent after the last glacial times, into the early Holocene (9–8 ± 1 ka) and was able to accumulate large aeolian dunes.  相似文献   

New Methods for Modeling Laterolog Resistivity Corrections   总被引：1，自引：1，他引：0  

Jadwiga Anna Jarzyna  Adam Cichy  Dezső Drahos  Attila Galsa  Maria Joanna Bała  Andrzej Ossowski 《Acta Geophysica》2016,64(2):417-442

The paper presents methods for laterolog response modeling. In Coulomb’s charges method, Laplace’s equation is solved for the electric field distribution in rock medium with internal boundaries between different resistivity layers. There, the boundary problem is reduced to Fred-holm integral equation of the second kind. The second method uses a finite element array to model apparent resistivity from laterolog. The task is treated as DC problem and the Laplace equation is solved numerically. The presented methods were applied to borehole data covering a typical stratigraphie section of the Fore-Sudetic Monocline in southwestern Poland. Apparent resistivity was calculated using the Coulomb’s charges method and alternatively modeled using a finite element method which gave similar results. Then, a series of linear corrections for borehole, shoulder bed, and filtration effects for apparent resistivity obtained by the Coulomb’s charges method demonstrated the feasibility of calculating true resistivity of virgin and invaded zones. The proposed methods provide a flexible solution in modeling which can be adapted to other logs.  相似文献   

Asteroid Confusions with Extremely Large Telescopes     

Gyula M. Szabó  Attila E. Simon 《Earth, Moon, and Planets》2009,105(2-4):227-234

Asteroids can be considered as sources of contamination of point sources and also sources of confusion noise, depending whether their presence is detected in the image or their flux is under the detection limit. We estimate that at low ecliptic latitudes, ≈10,000–20,000 asteroids/sq. degree will be detected with an E-ELT like telescope, while by the end of Spitzer and Herschel missions, infrared space observatories will provide ≈100,000 serendipitous asteroid detections. The detection and identification of asteroids is therefore an important step in survey astronomy.  相似文献