Türkiye Jeoloji Bülteni

Abstract: An 11 km long section of the Kazancı-Gümiişova Motorway is located on a soft alluvial soil. It is considered that determinationof consolidation characteristics of the alluvium soil, forming the basal soil along the studied motorway route and having low bearing capacity, is essential for the selection and design of art structures and for the in-profile optimization of the motorway embankment.In this study, data obtained from detailed in-situ and laboratory tests carried out on the basal soil at preliminary design andconstruction stages were evaluated. Based on the evaluated data, studied section of the motorway was divided in 

Abstract: In the present paper, an orbitoidal foraminifera Ilgazina unilateralis n. gen. n. sp. from the Maastrichtian of Ilgaz-Tosya (S Kastamonu) region has been described and its structural differences have been compared with the taxa showing similar structure. Thenew genus, which very closely resembles the genera Orbitoides, Sivasella and Hellenocyclina, is clearly differentiated from them bythe unilaterally situated chambers on its shell. 

Abstract: Granitic rocks cropping out in the Eastern Pontids are of Upper Cretaceous-Eocene in age and generally have quartz dioritegranodior ite-granite and tonalite composition in the northern parts. A number of porphyry Cu and Mo mineralizations are formed inrelation to these granitoids. Chemical investigations showed that these rocks are of l-type with calc-alkali affinity In addition they indicate an environment of island-arc which is gradually becomming mature.

Abstract: The Daday-Devrekani massif, located around Kastamonu region of the western Pont ides, consists of various metamorphic rocksranging from Precambrian to Early Cretaceous in age. These metamorphic rocks were derived from different source rocks in different geodynamic environments by different metamorphic conditions. The Precambrian Daday-Devrekani metasedimentary group,consisting of high-grade metased intents, is made typically of continental crust. It has also been affected by an Early-Middle Jurassicretrograde metamorphism. The Samatlar group of Lower-Middle Paleozoic age (the epicont mental cover) has been metamorphosedto very low-grade by Upper Jurassic, uossibly in Lower-Middle Jurassic. The Börümce formation of Lower Jurassic aget comprisingboth epiophiolitic and epiconlinental characters with some Lower-Middle Jurassic K-Ar ages, was affected by the very low-grademetamorphism similar to that of the Samatlar group.The p re-Lower Jurassic Çangal metaophiolite is a well-preserved fragment of oceanic crust. The Çangal metaophiolite was initially subjected to an ocean floor metamorphism before Lower Jurassic in the physical conditions of greenschist and epidoieamphibolite fades, it has also been affected by a later metamorphism during Lower-Middle Jurassic period. There are some contactaureole rocks, called Göynükdağı metamorphite with a total thickness up to 400 m in Göynükdağı region, developed around the Ahiçay-Elmalıçay granitoid from the Middle Jurassic Kastamonu granitoid belt which is an arc plutonism product. The Göynükdağıcontact aureole is composed mainly of spotted rocks of hornblend-hornfels and albite-epidote hornfels fades in the inner and outerzones, respectively. rThe cataclastic rocks such as protomylonite, mylonite, mylonite-schist and mylonite-gneiss, derived from the continental assemblage, and the glaocophane-schists, derived from the oceanic assemblage, altogether yield some Lower Cretaceous K-Ar ages. The Precambrian D aday-Devrekani metasedimentary group and its epicontinenîal cover Samaîlar group, oldest units in the Daday -Devrekani massif, are considered to be the southernmost tip of Eurasian plate. The Çangal metaophiolite is thought to be a wellpreserved part of the paleo-Tethyan oceanic cruts. As for the Börümce formation, it is assumed as epicontinental and sometimes epiophiolitic cover. The Göynükdağı contact aureole determines the contact haleous developed around arc plutonism. The Lower -Middle Jurassic metamorphism, affecting almost all the units in the D aday-Devrekani massif, and the arc magmatism of the MiddleJurassic Kastamonu granitoid belt are interpreted as the products of the subduct ion zone created by the northward subduct ion of thepaleo-Tethyan oceanic crust beneath the Eurasian plate. The Lower Cretaceous caiaclastites and glaucophanitic rocks are thoughtto have been generated by the collage between the Eurasia (Pontides) and Anatolia.

Abstract: Turkey has rich bentonite deposits. However, particularly in drilling bentonite, new deposits will be needed in future, apart fromthe Kalecik (Ankara) and Reşadiye (Tokat) deposits. Thus, bentonite deposits located at the Kelkit Valley ought to be investigated in detail, and necessary technological processes be carried out, to involve the deposit in economic utilization. Yazıcık bentonite occurin the Upper Cretaceous volcano sedimentary sequence. They have formed by the alteration of andesitic tuff and pyroclastic materialin marine environment. Yazıcık bentonite deposits, investigated partly in detail, seems to be hopefull as molding sand binder, at least in one bed.

Abstract: The studied Kirmir formation (Late Miocene-Pliocene) consists of alternation of gypsum and clay ey beds, which are conformably underlain by Bozbelen formation (sandstone, conglomerate, mudstone) and Sanycw limestones, and disconformably overlainby alluvium and tallus breccia of Pleistocene age.The unit includes three different fades, based on sedimentary properties of gypsum; 1) Individual gypsum beds inter bedded withgreen clays, 2) Scattered gypsum crystals and bassanite within an organic rich mudstone, 3) Massive gypsum with thin clay laminations. All these fades respectively reflect the different conditions of Neogene lake basin deposition: 1) Open lake with short evaporitic phases, 2) Marginal swamps with evaporitic ground water, 3) Closed lake with evaporitic lake water. These different stages ofgypsum occur ences primarily resulted from climatic changes from humid to arid. Tectonic is also thought to play a role on the regression of the lake area.

Abstract: Fluorit es were collected from a F-Pb vein related with hypabissal granodiorite porphyr intrusions ofSantonian-Campanian agewithin Istranca massif. In this vein type mineralization the fluorite and galena are the dominant ore minerals. Par agenesis consistsof fluorite + quartz + galena + pyrite + calcite. The host rock is represented by poly met amorphic crystalline basement of Precambrian age.M icrothermometric measurements on nearly 100 two-phase (1+v) inclusions yield mean homogenization temperature of 275 °Cforfluorites. Salinities range from 5 to 10 wt. percent NaCI equivalent, with mean of 7,5 %. M icrothermometric measurements onquartz reveal mean homogenization temperature oj`235"C. No fluid inclusions have been observed in calcites.The rare earth element contents of the fluorite is quite variable, ranging from 0,03 to 0,9 ppm and Ce/Yb ratios reflect the dominant trend of light rare earth element (LRIIF) enrichment. The similarity in the Tb/La ratios of dark purple, light purple and whitefluorite. indicates crystallization at about the same time. Chondrile normalized plot and rare earth element ratios of fluorite revealpersistent pozitive Ce anomalies, indicating low oxygen fugacities at the source area and negative Eu anomalies indicate the presence of the same conditions at the deposition site. Tb/La and Tb/Ca ratios confirm a liydrothermal origin for fluorites. 

Abstract: Diagenetıc quartz crystals with different textural features are observed as cement and replacement in various lit/iologies andfossils of the Berdiga limestone of Upper Jurassic-Lower Cretaceous age which has widespread exposures in eastern Pontids. Spongia spicules, radiolarian tests, clay stones, granitic and volcanic rocks rich in K-feldspar is the source for the silica required for theformation of diagenetic quartz.Various models have been proposed to explain the dissolution of carbonates and/or the replacement of carbonates by silica. Themost appropriate model is the one which explains that silicification observed in the Berdiga limestone is likely to be due to a replacment mechanism controlled by the force of crystallization. The other models (especially bacterial decay of organic substances) mayhave played a role locally during the ini t at i on of silicification of carbonates.Comparasion of diagenetic qucutz types found in the Berdiga limestone with various diagenetic environments and/or diageneticproducts of these environments has shown that diagenetic quartz crystals are not contemporaneous, and that, depending ont he timedepth function (together with volumetric shrinkage) they are observed to change from chalcedony-to quartzine-to microcrystallinequartz-and to megaquartz from shallow to deep burial environments.

Abstract: In the sudy area, the oldest outer oping formation belonging to Bolkardağ Unit is represented by Berendi formation (Jurassic Cretaceous). It is overlain technically by Kıraman ophiolitic melange which is emplaced during Companion. Mazı formation consisting of basal conglomarete, clay stone and clayey limestone levels upward, is of Middle Miocene age. The older units are overlain by Mazı formation with an angular unconformity. Divlek formation overlying the Mazı formation conformably consists of oolitic limestone and is of Upper Miocene age.Talc deposits are found within the Kıraman ophiolitic melange especially at Dildeğmez and Dolay area. Talc occurences probably, can be attributed to the fracture systems formed by Prc-Miocene shearing forces. Silica bearing metamorphic and/or acidichydrothermal waters filling the fracturesof serpantin ites had altered the serpantinites and formed the talc deposits. The formationage of talc deposits may be of Late Upper Miocene-Pliocene.Talc deposits were formed as lens-shape. But these deposits were also surrounded by low-quality stockwork types talc occur ances. In the area 75 000 tons of visible and 250 000 tons of probable talc reserve has been calculated. As a result, talc deposits studied in the area possess a quality which satisfy the requirements of color-baked ceramic industry.