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Your search keyword '"Leroy, S.A.G."' showing total 19 results
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11. Sediment distribution pattern of the South Caspian Sea: possible hydroclimatic implications

Author

Lahijani, H.A.K., Abbasian, H., Beni, A. Naderi, Leroy, S.A.G., Haghani, S., Habibi, P., Hosseindust, M., Shahkarami, S., Yeganeh, S., Zandinasab, Z., Tavakoli, V., Vahabi-Asil, F., Azizpour, J., Sayed-Valizadeh, M., Pourkerman, M., and Shah-Hosseini, M.

Subjects
Basins (Geology) -- Analysis -- Natural history, Terrigenous sediments -- Analysis -- Distribution, Geomorphology -- Analysis, Company distribution practices, Earth sciences
Abstract

The south Caspian subbasin extends from the foot of the Alborz Mountains to the deepest part of Caspian Sea. The lithological background and tectonic setting of the study area primarily control the deposition of thick sedimentary sequences of the basin, while hydroclimatic processes exert secondary impacts on the sediment distribution pattern. To evaluate past hydroclimatic changes, short sediment cores were retrieved from the continental shelf and upper slope of the south Caspian Sea and were treated for basic sedimentological properties and mineralogy. The results show that the sediments are composed of terrigenous, biogenic, and chemical components. The chemical component has a significant signature in the internal structure of the sediment, which reflects degradation of organic material due to a succession of aerobic and anaerobic conditions. Aerobic conditions reflect the extreme climatic conditions that lead to formation of well-oxygenated deep water in lowstands and extremely cold winters, when dense oxygenated water is allowed to touch the bottom sediments. The sediment distribution pattern demonstrates three distinctive areas in the southern continental margin with different organic matter and carbonate content. Fluvial inputs and wave hydrodynamics control the sediment properties and their distribution pattern in the upper shelf, while in deeper parts, the dynamics of water stratification and its temporal and long-term variations, relating to climate and water level changes, determine sediment composition. Overall, the sedimentary distribution pattern is a result of their sources in the catchment basin and the hydroclimate of the Caspian Sea. Key words: Caspian Sea, climate change, continental margin, deep-sea ventilation, sea level. Le sous-bassin Caspien meridional s'etend du pied des montagnes Alborz jusqu'a la partie la plus profonde de la mer Caspienne. Le contexte lithologique et le milieu tectonique de la region a l'etude sont les principaux contrôles du depôt d'epaisses sequences sedimentaires du bassin, des processus hydroclimatiques exerçant des influences secondaires sur la repartition des sediments. Afin d'evaluer les changements hydroclimatiques passes, de courtes carottes de sediments ont ete prelevees de la plateforme continentale et de la pente superieure de la mer Caspienne meridionale et ont fait l'objet d'analyses pour en determiner les proprietes sedimentologiques et la mineralogie. Les resultats montrent que les sediments sont composes de fractions terrigenes, biogenes et chimiques. La composante chimique est importante dans la structure interne des sediments, refletant une degradation de la matiere organique causee par une succession de conditions aerobies et anaerobies. Les conditions anaerobies refletent des conditions climatiques extrêmes qui menent a la formation d'eau profonde bien oxygenee durant des niveaux bas et des hivers extrêmement froids, quand l'eau oxygenee dense peut atteindre les sediments du fond marin. La repartition des sediments indique trois zones distinctes dans la marge continentale meridionale caracterisees par differents contenus en matiere organique et en carbonates. Les apports fluviaux et l'hydrodynamique des vagues contrôlent les proprietes des sediments et leur repartition sur la plateforme superieure, alors que, dans les zones plus profondes, la dynamique de la stratification de l'eau et ses variations temporelles a plus ou moins long terme reliees aux changements climatiques et du niveau de l'eau determinent la composition des sediments. Globalement, le motif de repartition des sediments est le resultat de leurs sources dans le bassin versant et de l'hydroclimat de la mer Caspienne. [Traduit par la Redaction] Mots-cles: mer Caspienne, changement climatique, marge continentale, ventilation du fond marin, niveau de la mer, [gamma]-globine., Introduction The Caspian Sea (CS) as a remnant basin of the Paratethys ancient ocean is the largest landlocked water body in the world (Lerche et al. 1997; Kosarev 2005). Its [...]

Published
2019
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13. Pollen-derived biomes in the Eastern Mediterranean–Black Sea–Caspian-Corridor

Author

Marinova, E. Harrison, S.P. Bragg, F. Connor, S. de Laet, V. Leroy, S.A.G. Mudie, P. Atanassova, J. Bozilova, E. Caner, H. Cordova, C. Djamali, M. Filipova-Marinova, M. Gerasimenko, N. Jahns, S. Kouli, K. Kotthoff, U. Kvavadze, E. Lazarova, M. Novenko, E. Ramezani, E. Röpke, A. Shumilovskikh, L. Tanţǎu, I. Tonkov, S.

Abstract

Aim: To evaluate the biomization technique for reconstructing past vegetation in the Eastern Mediterranean–Black Sea–Caspian-Corridor using an extensive modern pollen data set and comparing reconstructions to potential vegetation and observed land cover data. Location: The region between 28–48°N and 22–62°E. Methods: We apply the biomization technique to 1,387 modern pollen samples, representing 1,107 entities, to reconstruct the distribution of 13 broad vegetation categories (biomes). We assess the results using estimates of potential natural vegetation from the European Vegetation Map and the Physico-Geographic Atlas of the World. We test whether anthropogenic disturbance affects reconstruction quality using land use information from the Global Land Cover data set. Results: The biomization scheme successfully predicts the broadscale patterns of vegetation across the region, including changes with elevation. The technique discriminates deserts from shrublands, the prevalence of woodlands in moister lowland sites, and the presence of temperate and mixed forests at higher elevations. Quantitative assessment of the reconstructions is less satisfactory: the biome is predicted correctly at 44% of the sites in Europe and 33% of the sites overall. The low success rate is not a reflection of anthropogenic impacts: only 33% of the samples are correctly assigned after the removal of sites in anthropogenically altered environments. Open vegetation is less successfully predicted (33%) than forest types (73%), reflecting the under-representation of herbaceous taxa in pollen assemblages and the impact of long-distance pollen transport into open environments. Samples from small basins (

Published
2018

15. Realising consilience: How better communication between archaeologists, historians and natural scientists can transform the study of past climate change in the Mediterranean

Author

Izdebski, A. Holmgren, K. Weiberg, E. Stocker, S.R. Büntgen, U. Florenzano, A. Gogou, A. Leroy, S.A.G. Luterbacher, J. Martrat, B. Masi, A. Mercuri, A.M. Montagna, P. Sadori, L. Schneider, A. Sicre, M.-A. Triantaphyllou, M. Xoplaki, E.

Abstract

This paper reviews the methodological and practical issues relevant to the ways in which natural scientists, historians and archaeologists may collaborate in the study of past climatic changes in the Mediterranean basin. We begin by discussing the methodologies of these three disciplines in the context of the consilience debate, that is, attempts to unify different research methodologies that address similar problems. We demonstrate that there are a number of similarities in the fundamental methodology between history, archaeology, and the natural sciences that deal with the past ("palaeoenvironmental sciences"), due to their common interest in studying societal and environmental phenomena that no longer exist. The three research traditions, for instance, employ specific narrative structures as a means of communicating research results. We thus present and compare the narratives characteristic of each discipline; in order to engage in fruitful interdisciplinary exchange, we must first understand how each deals with the societal impacts of climatic change. In the second part of the paper, we focus our discussion on the four major practical issues that hinder communication between the three disciplines. These include terminological misunderstandings, problems relevant to project design, divergences in publication cultures, and differing views on the impact of research. Among other recommendations, we suggest that scholars from the three disciplines should aim to create a joint publication culture, which should also appeal to a wider public, both inside and outside of academia. © 2015 The Authors.

Published
2016

16. Realising consilience: How better communication between archaeologists, historians and natural scientists can transform the study of past climate change in the Mediterranean

Author

Izdebski, A., Holmgren, K., Weiberg, E., Stocker, S.R., Büntgen, U., Florenzano, Assunta, Gogou, A., Leroy, S.A.G., Luterbacher, J., Martrat, Belen, Masi, A., Mercuri, A.M., Montagna, P., Sadori, L., Schneider, A., Sicre, M.A., Triantaphyllou, M., Xoplaki, E., Izdebski, A., Holmgren, K., Weiberg, E., Stocker, S.R., Büntgen, U., Florenzano, Assunta, Gogou, A., Leroy, S.A.G., Luterbacher, J., Martrat, Belen, Masi, A., Mercuri, A.M., Montagna, P., Sadori, L., Schneider, A., Sicre, M.A., Triantaphyllou, M., and Xoplaki, E.

Abstract

This paper reviews the methodological and practical issues relevant to the ways in which natural scientists, historians and archaeologists may collaborate in the study of past climatic changes in the Mediterranean basin. We begin by discussing the methodologies of these three disciplines in the context of the consilience debate, that is, attempts to unify different research methodologies that address similar problems. We demonstrate that there are a number of similarities in the fundamental methodology between history, archaeology, and the natural sciences that deal with the past ("palaeoenvironmental sciences"), due to their common interest in studying societal and environmental phenomena that no longer exist. The three research traditions, for instance, employ specific narrative structures as a means of communicating research results. We thus present and compare the narratives characteristic of each discipline; in order to engage in fruitful interdisciplinary exchange, we must first understand how each deals with the societal impacts of climatic change. In the second part of the paper, we focus our discussion on the four major practical issues that hinder communication between the three disciplines. These include terminological misunderstandings, problems relevant to project design, divergences in publication cultures, and differing views on the impact of research. Among other recommendations, we suggest that scholars from the three disciplines should aim to create a joint publication culture, which should also appeal to a wider public, both inside and outside of academia.

Published
2016

18. Late Pleistocene and Holocene sea-level change and coastal paleoenvironment evolution along the Iranian Caspian shore

Author

Kakroodi, A.A. (author), Leroy, S.A.G. (author), Kroonenberg, S.B. (author), Lahijani, H.A.K. (author), Alimohammadian, H. (author), Boomer, I. (author), Goorabi, A. (author), Kakroodi, A.A. (author), Leroy, S.A.G. (author), Kroonenberg, S.B. (author), Lahijani, H.A.K. (author), Alimohammadian, H. (author), Boomer, I. (author), and Goorabi, A. (author)

Abstract

The level of the Caspian Sea is influenced by rivers mostly from the high latitudes of the Northern hemisphere and therefore any change of its catchments including temperature and precipitation directly reflects on Caspian Sea-level. We reconstructed Late Pleistocene to Holocene Caspian Sea-level by a multi-disciplinary approach from a 27.7 m long core in the SE corner of the Iranian Caspian coast in the Gomishan Lagoon. Late Pleistocene deposits containing typical Pleistocene fauna and dated around 20,120 cal yr BP bordered with a major hiatus indicating sea-level fall. Lagoonal deposits with shells dated at around 10,590 cal yr BP suggest that, after this deep lowstand, an initial transgression started, leading to landward advance of barrier–lagoon systems which still continued without any lowstand until 8400 cal yr BP. This corresponded to a biofacies change from lagoonal to the deeper biofacies including diatom and Gastropoda species. Around 8400 cal yr BP sea-level started to fall again, and reddish oxidized sediments with abundant foraminifera (Ammonia beccarii) record a regressive phase around 7700 cal yr BP. The mid-Holocene between 15.7 and 4.9 depths is characterized by a shallow marine environment mostly with high carbonate and gypsum contents, and lagoonal and highstand tract with no subaerial facies. The upper part of the core above a 4.9 m depth reflects at least five Late Holocene Caspian Sea-level cycles from 3260 cal yr BP onward. The Caspian Sea-levels are influenced both by global and regional events., Geoscience & Engineering, Civil Engineering and Geosciences

Published
2015
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