Dans de nombreuses chaînes de montagnes, on observe des témoins du processus d’obduction, correspondant au transport de la lithosphère océanique sur la croûte continentale. Le paradoxe intrinsèque de ce phénomène est celui-ci : des roches denses (ρ>3) se retrouvent au-dessus de roches moins denses (ρ≈2,7). Les processus à l’origine de cette bizarrerie tectonique sont encore mal compris. Les ophiolites du Petit Caucase et du NE de l’Anatolie correspondent à un exemple extrême de ce phénomène puisqu’on constate un transport de fragments de lithosphère océanique sur plusieurs centaines de kilomètres, à l’échelle de l’ensemble d’une bordure continentale (>1000 km) vers 90 Ma. En adoptant une stratégie pluridisciplinaire lors de l’étude de ces ophiolites, nous avons pu préciser l’évolution des premiers stades de la fermeture néotéthysienne et en conséquence l’obduction de ces dernières. Ces données suggèrent fortement une mise en place commune de l’ensemble de ces corps ophiolitiques de la région d’étude sous la forme d’une nappe, dont l’épaisseur actuelle est très réduite (quelques kilomètres tout au plus). Ceci en fait l’une des plus grandes nappes ophiolitiques obduites du globe. La modélisation numérique a validé l’hypothèse que la mise en place de cette nappe s’est faite grâce à des conditions thermiques particulières. Elle suggère que l’obduction d’ophiolites vieilles nécessite un état thermique de la lithosphère océanique proche de celui d’une lithosphère jeune (0-40 Ma). / Within many mountain ranges slivers of preserved oceanic lithosphere evidence tectonic processes responsible for their emplacement on top of the continental crust. The first order anomaly inherent to this phenomenon is that dense rocks (ρ>3) end up on top of less dense rocks (ρ≈2.7). The processes responsible for such a tectonic oddity remain uncertain. The ophiolites of the Lesser Caucasus and NE Anatolia are prime examples of this phenomenon, tectonic transport of fragments of oceanic lithosphere is evidenced on the entire continental marge (>1000 km) around 90 Ma. The multidisciplinary approach used throughout the study of the ophiolites of the Lesser Caucasus and NE Anatolian regions yielded clues specify the evolution of the Tethys and consequently the obduction of the ophiolites. This dataset strongly suggests common emplacement of the ophiolites of the study area, resembling a thrust sheet. This would be one of the biggest ophiolite nappe complexes in the world. Numerical modeling validates the hypothesis that emplacement of the ophiolitic nappe is due to particular thermal conditions. It suggests that in order to obduct old oceanic lithosphere obduction it needs to have a thermal state close to that of young oceanic lithosphere (0-40 km). Such a thermal rejuvenation is supposed for the ophiolites of the Caucasus s.l. evidenced by alkaline lavas emplaced on the ophiolite prior to the obduction event during the Late Cretaceous. Resulting seamounts and/or oceanic plateaus upon entery of the subduction zone under Eurasia would block it.

Protected area site selection is generally carried out using biodiversity data as surrogates. However, reliable and complete biodiversity data is rarely available due to limited resources, time and equipment. Instead of drawing on inadequate biodiversity data, an alternative is to use environmental diversity (ED) as a surrogate in conservation planning. However, there are few studies that use environmental diversity for site selection or that evaluates its efficiency / unfortunately, no such example exists for Turkey, where biodiversity is high but our knowledge about it is unsatisfactory. Hence, this study was carried out to investigate the efficiency of environmental surrogates and the utility of different biological taxa in conservation planning. The objective was to find out the most efficient surrogates, either environmental or biological, for conservation planning, so that limited resources can be used more efficiently to establish an effective protected areas network. The study was carried out in northeastern Turkey, within the Lesser Caucasus ecoregion. The taxonomic groups considered include large mammals, breeding birds, globally threatened reptiles and amphibians, butterflies, highly threatened plants, and ecological communities. The distribution data was taken from a previous study, while climate and topographical data were obtained from various sources and produced through spatio-statistical techniques. Complementarity-based site selection was carried out with Marxan software, where the planning unit was the 100 sq.km. UTM grid square. Various statistical methods, including geographically weighted regression, principal components analysis, and p-median algorithm, were used to determine ED across the units. Performance of different approaches and different sets of surrogates were tested by comparing them to a random null model as well as representation success. Results indicate that endemic or non-endemic highly threatened plant species, butterfly species and ecological communities represent biodiversity better than other taxa in the study area. As such, they can be used on their own as efficient biodiversity surrogates in conservation area planning. Another finding is that highly threatened plant species are required to be used in the site selection process if they need to be represented well / in other words, they are their own surrogates. It was demonstrated that while ED alone can be used as a surrogate to represent biodiversity of an area, they are not as good as biodiversity surrogates themselves. It is also suggested that using species taxa with smaller distributional ranges or taxa that complement each other due to ecological differences as surrogates provide better results. On the other hand, ED might be a more suitable surrogate if resources are very limited or field work is impossible. In such cases, using ED in conjunction with one of the better biodiversity surrogates is probably the best solution.