Determining and Mapping Eco-Cultural Subregions Using GIS and Simos Procedure

Immovable cultural properties constituting cultural heritage centre upon regions that have the level of natural features required for basic human needs. Such regions constitute a space with characteristics of an eco-cultural subregion and they do not have any administrative or geographical boundaries. Aims of this study are to introduce the concept of eco-cultural subregion, which is the holistic expression of natural features together with cultural heritage, to the literature; to present a method in identifying geographical boundaries of subregions; and to formulate a classification system. The research was conducted in the Phrygian Valley, which is one of the most important centres of ancient Phrygians in Western Anatolia, using a method based on GIS-MCDM (Geographic Information System-Multiple Criteria Decision Making). The selected MCDM technique was Simos Procedure. Natural features and cultural heritage were considered together and the entire Phrygian Valley was approached as both an ecological and a cultural region. Ecological features were analysed using 7 main and 17 subfactors, while cultural heritage was analysed using 2 main factors and 15 subfactors. Simos Procedure was employed in the assignment of weight for main factors and subfactors. First 17 ecological subregions with similar characteristics under 4 levels were identified. Considering their cultural heritage values, a classification system was formulated and eco-cultural subregions were expressed in level/degree in this system. In consequence of this procedure boundaries of eco-cultural subregions were drawn and mapped. This classification also enabled to identify the concept of eco-cultural subregion which is not found in the literature. It is expected that eco-cultural subregions will provide to discuss ecological features and cultural heritage holistically in conservation and planning studies.     

Geological, mineralogical and geochemical characteristics of zeolite deposits associated with borates in the Bigadiç, Emet and Kirka Neogene lacustrine basins, western Turkey

The Bigadiç, Emet and Kirka lacustrine basins of western Turkey may be considered as Tibet-type graben structures that were developed during the Miocene within the Izmir-Ankara suture zone complex. The volcanic-sedimentary successions of these basins are made up of mudstone, carbonate (limestone and dolomite) and detrital rocks, and also of crystal or vitric tuffs about 135 to 200 m thick. The Degirmenli (Bigadiç), Emirler (Bigadiç) Köpenez (Emet) and Karaören (Kirka) tuffs constituting the zeolite deposits are situated beneath four borate deposits (colemanite, ulexite, borax). The most abundant diagenetic silicate minerals are K- and Ca-clinoptilolites in the zeolite deposits, and Li-rich trioctahedral smectites (stevensite, saponite and hectorite) and K-feldspar in the borate deposits. In the Degirmenli, Emirler. Köpenez and Karaören deposits, the following diagenetic faciès were developed from rhyolitic glasses rich in K and poor in Na: (glass + smectite), (K-clinoptilolite + opal-CT), (Caclinoptilolite + K-feldspar ± analcime ± quartz) and (K-feldspar+analcime+quartz). K-feldspar which is also rarely associated with phillipsite (Karaören) and heulandite (Degirmenli and Karaören), succeeds clinoptilolite and precedes analcime in these diagenetic facies where dioctahedral smectites, opal-CT and quartz are the latest minerals. No diagenetic transformations exist between clinoptilolite, K-feldspar and analcime that were formed directly from glass. The lateral facies distributions resulted from the differences in salinity and pH of pore water trapped during deposition of the tuffs, but vertical distributions in vitric tuffs seem to have been controlled by the glass/liquid ratio of the reacting system and the permeability or diffusion rate of alkali elements. The Bigadiç, Emet and Kirka zeolite deposits which were formed in saline basins rich in Ca and Mg ions, show similar chemical changes, i.e. loss of alkalis and gain in alkaline-earth elements that have taken place during the diagenetic transformation of rhyolitic glasses to dioctahedral smectites or clinoptilolite. The absence of sodic zeolites such as mordenite, erionite, chabazite and silica-rich phillipsite is mainly due to the very high K/Na ratio of the starting materials rather than initial alkaline conditions or high Na content in lake waters.     

Zn-rich högbomite formed from gahnite in the metabauxites of the Menderes Massif,SW Turkey

Gahnite, ZnAl₂O₄, present as an accessory mineral in regionally metamorphosed low-grade diasporites, has reacted in adjacent higher-grade, corundum-bearing metabauxite equivalents (emeries) to form Zn-rich högbomite, (Zn,Fe²⁺,Mg,Ni)_t-2x (Ti,Sn)_xAl₂O₄, of the 4H polytype. Commonly, the initial högbomite crystals grew epitactically along the octahedral faces of gahnite, which was subsequently dissolved, so that högbomite now forms spectacularly intergrown sets of eight crystals in perfect crystallographic orientation to each other. This indicates a metamorphic reaction, probably involving a fluid, transporting mainly the elements Zn and Al. Reactant Ti minerals in the diasporites were rutile and titanian hematite (10–15 mol% FeTiO₃). In the emeries högbomite coexists with still more Ti-rich hematites containing between 26 and 37 mol% FeTiO₃. The overall reaction relations involving partial reduction may be subdivided into the intial univariant reaction, gahnite+diaspore+Ti-hematite+rutile=högbomite+H₂O+O₂. This was followed, in the absence of gahnite, by compositional readjustments of högbomite and Ti-hematite and the appearance of magnetite. Core to rim zoning profiles indicate that, with continued growth, the högbomite crystals became poorer in Zn and Ti, but richer in Fe²⁺, while the Ti-contents of coexisting hematite increased. Högbomite formation at the expense of gahnite started at temperatures as low as about 400° C for an estimated pressure of 5–6 kbar.     

Evaluation of seismicity and seismic hazard parameters in Turkey and surrounding area using a new approach to the Gutenberg–Richter relation

In this study, the spatial distributions of seismicity and seismic hazard were assessed for Turkey and its surrounding area. For this purpose, earthquakes that occurred between 1964 and 2004 with magnitudes of M ≥ 4 were used in the region (30–42°N and 20–45°E). For the estimation of seismicity parameters and its mapping, Turkey and surrounding area are divided into 1,275 circular subregions. The b-value from the Gutenberg–Richter frequency–magnitude distributions is calculated by the classic way and the new alternative method both using the least-squares approach. The a-value in the Gutenberg–Richter frequency–magnitude distributions is taken as a constant value in the new alternative method. The b-values calculated by the new method were mapped. These results obtained from both methods are compared. The b-value shows different distributions along Turkey for both techniques. The b-values map prepared with new technique presents a better consistency with regional tectonics, earthquake activities, and epicenter distributions. Finally, the return period and occurrence hazard probability of M ≥ 6.5 earthquakes in 75 years were calculated by using the Poisson model for both techniques. The return period and occurrence hazard probability maps determined from both techniques showed a better consistency with each other. Moreover, maps of the occurrence hazard probability and return period showed better consistency with the b-parameter seismicity maps calculated from the new method. The occurrence hazard probability and return period of M ≥ 6.5 earthquakes were calculated as 90–99% and 5–10 years, respectively, from the Poisson model in the western part of the studying region.     

Geochemical make-up of oceanic peridotites from NW Turkey and the multi-stage melting history of the Tethyan upper mantle

We present the whole-rock and the mineral chemical data for upper mantle peridotites from the Harmanc?k region in NW Turkey and discuss their petrogenetic–tectonic origin. These peridotites are part of a Tethyan ophiolite belt occurring along the ?zmir-Ankara-Ercincan suture zone in northern Turkey, and include depleted lherzolites and refractory harzburgites. The Al₂O₃ contents in orthopyroxene and clinopyroxene from the depleted lherzolite are high, and the Cr-number in the coexisting spinel is low falling within the abyssal field. However, the orthopyroxene and clinopyroxene in the harzburgites have lower Al₂O₃ contents for a given Cr-number of spinel, and plot within the lower end of the abyssal field. The whole-rock geochemical and the mineral chemistry data imply that the Harmanc?k peridotites formed by different degrees of partial melting (~%10–27) of the mantle. The depleted lherzolite samples have higher MREE and HREE abundances than the harzburgitic peridotites, showing convex-downward patterns. These peridotites represent up to ~16 % melting residue that formed during the initial seafloor spreading stage of the Northern Neotethys. On the other hand, the more refractory harzburgites represent residues after ~4–11 % hydrous partial melting of the previously depleted MOR mantle, which was metasomatized by slab-derived fluids during the early stages of subduction. The Harmanc?k peridotites, hence, represent the fragments of upper mantle rocks that formed during different stages of the tectonic evolution of the Tethyan oceanic lithosphere in Northern Neotethys. We infer that the multi-stage melting history of the Harmanc?k peridotites reflect the geochemically heterogeneous character of the Tethyan oceanic lithosphere currently exposed along the ?zmir-Ankara-Erzincan suture zone.