Türkiye Jeoloji Bülteni

Abstract: In the tectonical evolution of the Hoyran Lake region, stable, tensional and compressional phaseshave followed each other recurringly. Main tectonical phases can be summarized as follows : (1) During the intervalof Liassic - Maestrichtian, a long stable phase and the development of Hoyran carbonate platform; (2) During the interval of Maestrichtian to Lutetian, tensional tectonism phase of gradually increasing intensity: During this phase,carbonate platform starts to be fragmented; (3) At the end of Upper Lutetian, compressional tectonics become dominant, and as a result of this, Internal Taurus ophiolitic melange nappe is emplaced on Hoyran carbonate platform.The period including the geologic events occurred up to here, and structures caused by these events has been called asPaleotectonic period; (4) Uplifting, local emergence, erosion, formation of molasse as a result of compressional tectonism, and dominant tensional tectonism; (5) A second compressional tectonism phase of lesser intensity at the endof Middle Oligocene: During this phase, by thrusting, the carbonate platform acts as a para - autochthonous unitwhile the molasse takes a new autochthonous position, and the region becomes complately terrestrial. In addition tothis, the regime of compressional tectonism begins changing to a character of tensional tectonism. The period betweenthe Paleotectonic period, which ceased at the end of Upper Lutetian, and the end of Middle Oligocene, during whichthe region becomes entirly terrestrial, has also been called as Transition period; (6) Tensional tectonism period,which has been dominating from the end of Middle Oligocene to present : During this period named as Neotectonicperiod, regional swelling, block - faulting, alkaline volcanism take place and the region acquires its present appearence.

Abstract: Sedimentological study of various Liassic sequences in the Pontides has revealed the outlines of thegeomorphological, depositional, and tectonic characteristics of their environment of deposition. At the beginning ofthe Lias, the Pontides were a positive region associated with the active continental margin of Paleo-Tethys alongthe northern border of Gondwana - land. On this wide area, formed mainly from various Paleozoic (? and Triassic}rocks, clastic platform sediments of dominantly fluvial, swamp, and shallow - marine environments were laid down.Rifting and associated block faulting began along the southern border of the Pontides related to the opening ofthe northern branch of Neo - Tethys at the beginning or just before the Sinemurian. This event affected large areasin the Pontides and generated seamounts and intervening basins corresponding with horsts and grabens respectively.This topography determined the tectonic characteristic of the northern margin of Neo-Tethys and controlled sedimentation during and after the Sinemurian. On top and along the flanks of the seamounts locally condensed seriesincluding, red-grey coloured biomicrite, bîosparite and pelmicrite, and shallow carbonate facies including oolitesand reefs were deposited, whereas mainly grey - coloured turbidites made up of shales, sandstones, conglomerateswith volcanic and crystalline clasts, and intercalations of tuffs and lavas characterized the basin deposition. Locally,into these turbidities, material was carried from the condensed sequences capping seamounts. In some areas (e.g.Amasya and Gümüşhane) deep-sea deposits directly overlie the seamount deposits as a result of the latter`s subsidence, perhaps owing to listric normal faulting and block rotation. Environmental analysis of the Liassic deposits inthe Pontides show that the Bilecik, Ankara and Alucra (Giresun) areas were generally located on seamounts, the Mudurnu and Niksar-Reşadiye areas were basins; and the Amasya, Havza, Gümüşhane and tspir - Yusuf eli regionswere rapidly subsiding seamounts. These data indicate that the northern branch of Neo - Tethys formed as a resultof the rifting of the Paleo-Tethyan magmatic arc from the Gondwana - land platform during the Lias and notearlier, during the Trias as claimed by some researchers.

Abstract: According to the observations made on the North Anatolian fault zone where the epicentral areas of1942 Erbaa and 1943 Tosya earthquakes are located, it is defined that the active fault traces change direction in a convergence sense upto 15°. At the same time the above areas qceur in the metamorphic complexes and are also subjectedto local and regional uplifting. The features obtained from these two localities, are applied to the other epicentralareas of past large magnitude earthquakes on the North Anatolian fault zone and it is noticed that these areas have the same features. Here the relationship between the above criteria and large magnitude earthquakes has been discussed, as a result of which 4 new forecasting epicentral areas of large magnitude earthquakes have been put foreward. These are (a) Bandırma district, (b) Palu-Gökdere, (c) Pötürge Karamemikler and (d) Karlıova-Elmalı river.It is recomended that an instrumental network in these areas should be installed to monitor the seismic activity associated to forthcoming large magnitude earthquakes. 

Abstract: The Instranca Massif is underlain by a basement of gneissic rocks unconformably overlain by a coverof Paleozoic and Mesozoic sedimentary rocks. These rocks are composed of shale, limestone and sandstone which areregionally metamorphosed in the greenschist facies. The sedimentary rocks are, in turn, largely intruded by UpperCretaceous granodioritic rocks and in part covered by volcano - sedimentary rocks also of Upper Cretaceous age.The many ore deposits and mineralizations known from the Istranca Massif generally occur in the contactzone between the intrusive and sedimentary cover rocks; they are the result of hydrothermal contact mineralization.Disseminated and stockwork types of mineralization formed by primary ore minerals such as pyrite, some chalcopyrite,traces of molybdenite and scheelite are found close to the contact zone within the granodiorite porphyry; locally,hydrothermal quartz veins containing trace of molybdenite cut the granodiorite porphyry. The more important deposits and mineralizations occur in some contact zones; they consist of primary ore minerals, the most important ofwhich are magnetite, chalcopyrite, bornite, the fahlerz group, pyrite, pyrrhotite, the Bi-minerals (e.g., bismuth, bismuthinite, emplectite, wittichenite, gladite, tatradymtte, etc.), sphalerite, cubanite, valleriite and scheelite in association with such secondary ore minerals as chalcocite, coveilite, malachite, azurite and limonite.The paragenesis and the texture and structure of the öre minerals has been studied in detail. The mineral cubanite and valleriite indicate a temperature of formation of 250° - 300°C, elsewhere mineralization generally occurs insome skarn zones where chalcopyrite contains exsolution stars,of sphalerite; these phenomena show that these ore deposits and mineralizations have been formed in meso - katathermal conditions.One of the most important ore deposits in the Istranca Massif is ikiztepeler, which was being worked for Cu,Mo and W. 

Abstract: Petrologic analyses of the volcanics in Gördes (Manisa) region is used in interpretation of origin andplate tectonics of Western Anatolia. Late Miocene volcanisoa is dacitic, rhyodaeitic and rhyolitic with a calcalkaline affinity. Petrochemical characteristics of the Gördes volcanics point out to the fact that they might be originatedfrom continental crust as a result of anatexis.

Abstract: In order to investigate the influence of various recharge and discharge conditions on the behaviourof the aquifer and also to evaluate present groundwater management practices in Erzin and Dörtyol plains the hydrographs of seven observation wells were studied.The well hydrographs show excellent correlation with the dry and wet periods. In spite of excessive irrigationpumpage since 1974, the groundwater reserves of Erzin plain have not been affected significantly. Starting from 1976,which also corresponds to the beginning of the wet years, the groundwater levels have risen steadily in both plains.During the period 1974 -1978 the groundwater levels in Erzin plain show an average rise of 10 m and in Dörtyol ?lainabout 4 m.The present groundwater management practice seems to be quite adequate for Erzin plains. However, in the longterm, with the present groundwater management policy, the groundwater levels in Dörtyol plain may show a general decline and also produce an undesirable salt water intrusion problems.

Abstract: Pliocene deposits extending along Dardanelles are overlain by Quaternary sediment which may bebest observed in Hamzakoy, nort of Gelibolu town. These sediment contain a rich and very well preserved fauna ofTschauda (Bakunian) Mollusc which characterize the Ponto - Caspic basin of Eastern Paratethys.

Abstract: The species representing the family Phylloceratidae in the Liassic rocks of northern Anatolia are hereplaced in four genera : Phylloceras Suess, Partschiceras Fucini, Hantkeniceras Kovacs, and CalMphylioceras Spath. Thespecies referred to Phylloceras are P.(Phylioceras) frondosum, P(P). lipoldi, P(P). hebertinum, P(P). meneghini,PCZetoceras) zetes, P(Z). pseudozetes, PCZ). bonarellii, P(Z). oenotrium* P(Z). lavizzarii, P(Z)?. anatolicum. Their systematic descriptions were given in the part I (*).CalMphylioceras is represented by a single species, C. bicicolae, in the Upper Sinemurian - Lower Pliensbachian rocks of the Bilecik, Amasya and Gümüşhane - Bayburt regions, in northern Anatolia. Previously reported speciesC. emeryi, C. alontinum, C. geyeri, C. bettonii are regarded synonyms of C. bicicolae. Partschiceras is represented bya single species, P. striatocostatum, and Hantkeniceras by three species, H. cf.hantkeni, H. pseudocalais, H. sp.

Abstract: Many of the geoelectrical measurements being made in connection with earthquake prediction studiesare based on the concept that these properties are influenced by stress or strain build up, especialyso near the failure point. Electrical properties of rocks are controlled by the fluid in the pores and craks of the rocks and, sincethis is the fraction of a rock most influenced by stresses, one should expect electrical measurements to be sensitivemeasures of changing stresses and strains. The strain changes that one is dealing with in there studies, however, arevery small (i.e. in the order of 10"4) and even though the electrical responses can amplify the effect great sensitivityis needed in making the measurements. Because, the estimated change in resistivity is only as much as 1% percent.Some important aspects to examine are depth of occurrances and factors influencing electrical properties insedimantary rocks, laboratory experiments to determine strain - resistivity relationship and careful studies of all previous work completed in this field of interest.

Abstract: There are some old coastal traces 0.5 1.3 m higher than the present sea-level along the Mediterranean coastine between «Fığla burnu» and «Malta burnu» about 20 km west of Alanya. These are coastal platformswhich are formed by bioerosion of some gastropods such at Littorina and Patella. There are also bio - constructive rimson the surfaces and along the outer edges of the platform formed by calcareous algae. Some calcareous algae samplesfrom the 0.5 m elevaıed surface of the bio - crosional platforms are dated using C1 4 method. These datings showedthat the algae lived in the period between 2690 -1545 years before present on the platforms. A neo - tectonic eventwhich happened at about 1550 years before present, caused upheaval of these former platforms about 6.5 -1.2 m. Therefore, the algae died and their biological actions finished on the platforms. This event coincides with the seismo - tectonic upheaval of the coastlines of the southern Aegen island arc that is proved by other geomorphological studiesand C1 4 datings. Afterwards, nev bio - erosionai platforms and bio - constructive rims began to develop at the presentsea-level. Formation of these features is still continuing today.