Neotectonics of Turkey – a synthesis

Abstract

Turkey forms one of the most actively deforming regions in the world and has a long history of devastating earthquakes. The belter understanding of its neotectonic features and active tectonics would provide insight, not only for the country but also for the entire Eastern Mediterranean region. Active tectonics of Turkey is the manifestation of collisional intracontinental convergence- and tectonic escape-related deformation since the Early Pliocene (~5 Ma). Three major structures govern the neotectonics of Turkey; they are dextral North Anatolian Fault Zone (NAFZ), sinistral East Anatolian Fault Zone (EAFZ) and the Aegean–Cyprean Arc. Also, sinistral Dead Sea Fault Zone has an important role. The Anatolian wedge between the NAFZ and EAFZ moves westward away from the eastern Anatolia, the collision zone between the Arabian and the Eurasian plates. Ongoing deformation along, and mutual interaction among them has resulted in four distinct neotectonic provinces, namely the East Anatolian contractional, the North Anatolian, the Central Anatolian ‘Ova’ and the West Anatolian extensional provinces. Each province is characterized by its unique structural elements, and forms an excellent laboratory to study active strike-slip, normal and reverse faulting and the associated basin formation. © 2001 Éditions scientifiques et médicales Elsevier SAS     

Lower Cretaceous black shales of the Western Carpathians,Czech Republic: Palynofacies indication of depositional environment and source potential for hydrocarbons

Uppermost Jurassic and Lower Cretaceous strata of the Silesian Nappe of the Outer Western Carpathians contain large amounts of shale, which can, under favourable conditions, become source rocks for hydrocarbons. This study analysed 45 samples from the area of Czech Republic by the means of palynofacies analysis, thermal alteration index (TAI) of palynomorphs and total organic carbon (TOC) content to determine the kerogen type, hydrocarbon source rock potential, and to interpret the depositional environment. Uppermost Jurassic Vendryně Formation and Lower Cretaceous Formations (Těšín Limestone, Hradiště and Lhoty) reveal variable amount of mostly gas prone type III kerogen. Aptian Veřovice Formation has higher organic matter content (over 3 wt.%) and oil-prone type II kerogen. Organic matter is mature to overmature and hydrocarbon potential predisposes it as a source of gas. Aptian black claystones of the Veřovice Fm. are correlatable with oceanic anoxic event 1 (OAE1).     

Crustal properties from S-wave and gravity data along a seismic refraction profile in Romania

VRANCEA'99 is a seismic refraction line that was carried out in 1999 to investigate the deep structure and physical properties of the upper lithosphere of the southeastern Carpathians and its foreland. It runs from the city of Bacau to the Danube River, traversing the Vrancea epicentral area of strong intermediate-depth seismicity and the city of Bucharest.

Interpretation of P-wave arrivals led to a velocity model that displays a multi-layered crust with velocities increasing with depth. The range of P wave velocities in the sedimentary cover increases from N to S and a structuring of the autochthonous basement of the Moesian Platform is observed. The crystalline crust displays thickness variations, but at the same time the lateral velocity structure along the seismic line remains almost constant. An intra-crustal boundary separates an upper crust from the lower crust. Within the upper mantle a low velocity zone is detected at a depth of about 55-km.

The interpretation of observable S-waves resulted in a velocity model that shows the same multi-layered crust, with S-velocities increasing similarly with depth as the P-waves. The corresponding Poisson's ratio is highly variable throughout the crust and ranges from 0.20–0.35 for the sedimentary cover to 0.22–0.25 for the crystalline crust. The interpretation of the V_p, V_s and Poisson's ratio in petrological terms suggests a large variety of rocks from sand and clay to sandstone, limestone and dolomite within the sedimentary cover. Within the crystalline crust the most probably rock types are granite, granodiorite, granite–gneiss and/or felsic amphibolite–gneiss in the upper part and gneiss and /or amphibolite in the lower part.

Based on the 2-D seismic velocity model, a density model is developed. Density values are assigned to each layer in agreement with the P-wave velocity model and with values accepted for the geological units in the area. After several iterations a good fit between the computed and observed Bouguer anomalies was obtained along the seismic line.     

Three Dimensional Plate Kinematics in Romania

Since 1996 the Collaborative Research Center (CRC) 461``Strong Earthquakes: A Challenge for Geosciences andCivil Engineering' is funded by the DeutscheForschungsgemeinschaft (German Research Foundation) asa German contribution to the UN initiative``International Decade of Disaster Reduction' (IDNDR).A central project of this CRC is the subproject B1``Three Dimensional Plate Kinematics in Romania', whichis installed to detect borders of the geotectonicplates in Romania, to quantify their three-dimensionalmovement rates and to determine in detail thedeformation of each geotectonic unit in the VranceaRegion as a contribution to the research of thetectonic cause of the intermediate depth earthquakesin this region. These aims shall be accomplished byrepeated GPS-measurements in a network which has beeninstalled in 1997 and measured until now in 1997 and1998. This network is consisting of 26 stations,covering an area of 250 km × 380 km with the Vranceaarea as the centre. The geodetic frame is given by sixstations of the CEGRN (Central European GeodynamicRegional Network) of the CEI-initiative CERGOP, forwhich coordinates and velocities in a global tectonicscenario are available. The paper gives informationabout the tectonic background, the geodetic network,the GPS-measurements and the achieved accuracies andfirst results of deformation analyses. It is shownthat until now no significant deformations could bedetected. But the extension of the GPS network andremeasurements with time intervals of two years willallow statements about the recent crustal movementswithin the lifetime of the CRC 461.     

Albian and Cenomanian palaeobathymetry in the Pieniny Klippen Belt Basin, Polish Carpathians

During the Albian and Cenomanian, the Pieniny Klippen Belt Basin, a part of the Carpathian geosynclinal domain, showed a clear differentiation into an axial deepest part represented by the Pieniny and Branisko successions and two marginal zones, a southern (Nizna and Haligovce successions, in Slovakia) and a northern zone (in Poland and Slovakia) represented by the Niedzica, Czertezik and Czorsztyn successions, becoming progressively more shallow towards the north. Five palaeobathymetric foraminiferal associations have been distinguished in the axial and northern marginal zone sediments of the Klippen Basin, corresponding to: ‘A’ shelf and upper slope: relatively large proportion of nodosariids and miliolids (Czorsztyn succession); ‘B1’ middle part of slope; oligotaxic planktonic assemblage dominant (Niedzica through Branisko successions and northern part of the Pieniny succession); ‘B2’ middle part of slope: larger proportion of agglutinated foraminifers, association characteristic of sediments influenced by turbidites (submarine flyschoid channels in the Branisko succession); ‘Cl’ middle and lower parts of slope: scarce microfauna, Hedbergella and textularids dominant (Pieniny succession, middle part); ‘C2’ slope/abyssal plain transition, close to foraminiferal lysocline (probably about 3500m below sea level): scarce specimens corroded and slightly dissolved (Pieniny succession, southern part).     

An opportunistic trace fossil assemblage from the flysch of the Inoceramian beds (Campanian-Palaeocene), Bystrica Zone of the Magura Nappe, Carpathians, Poland

A relatively poorly diversified trace fossil assemblage from thin- and medium-bedded flysch of the Inoceramian beds in the Polish Outer Carpathians is dominated by postdepositional r-selected Chondrites, Planolites and Helminthoida. Predepositional K-selected forms are very rare. This, together with a lack of evidence for bottom erosion and the relatively dark colour of interbedded mudstone and siltstone, suggest that low sediment oxygenation was the main factor controlling benthic life. Preservational factors, related to the fluid consistency of sediment and to mixed layers, seem to be present, but subordinate. Small-scale changes of diversity and abundance of the trace fossils within the sections probably reflect changes in sediment oxygenation.     

The Valanginian history of the eastern part of the Getic Carbonate Platform (Southern Carpathians,Romania): Evidence for emergence and drowning of the platform

Lower Cretaceous successions that crop out in the eastern part of the Getic Carbonate Platform (Southern Carpathians, Romania) preserve records of the Valanginian events in different settings of the platform. The integrated sedimentological, biostratigraphical, geochemical and mineralogical analysis of the upper Berriasian–Valanginian successions reveal successive stages in the evolution of the carbonate platform: (a) pre-drowning stage of the shallow-shelf and slope settings of the platform; (b) subaerial exposure and karstification; and (c) incipient flooding and drowning of the carbonate platform. Following the subaerial exposure, starting in the middle early Valanginian, the eastern part of the Getic Carbonate Platform experienced a drowning phase documented by iron oxyhydroxides, phosphate and glaucony mineralized discontinuity surface and glaucony-rich sediments disposed on the discontinuity surface. Recognition of the diachronous intra-Valanginian discontinuity surface within the studied successions is based on clear evidences (facies contrast, depositional and diagenetic features, biostratigraphic and taphonomic data, and geometrical relations). The negative–positive carbon isotope excursion is correlated with the global perturbations of the carbon cycle related to the Valanginian “Weissert” episode, and it is documented for the first time in the shallowest parts of the Getic Carbonate Platform. Tectonic activity and eustatic sea-level fluctuations were most probably the main factors that led to fault-block tilting, local emersion and subsequent drowning of the eastern part of the Getic Carbonate Platform during the Early Cretaceous. We infer that the eastern part of the Getic Carbonate Platform was affected by late Berriasian–early Hauterivian extensional tectonics that could be related to the Neo-Cimmerian movements with effects generally recognized in the northern peri-Tethyan areas.     

斯洛伐克西喀尔巴阡山脉Gemerská Poloma滑石-菱镁矿矿床中镁的交代作用

Gemerská Poloma矿床是个重要的滑石矿床(储量20万吨),位于西喀尔巴阡山脉Germeric地区。部分滑石化的镁质碳酸盐体赋存在早古生代火山沉积杂岩体中(黑色片岩,变质泥岩),在Variscan变质作用(M1)过程中受到了绿泥石-黑云母带区域变质相的改造。这种原岩是石灰岩的矿体由白色-灰白或者灰色-黑色的菱镁矿与白云石1组成,被次生的白云石2和滑石脉切割。本次研究考察了两次变质事件(M1和M2)的几个连续的矿物组合,最早的组合包括铁白云石,镁菱铁矿与菱铁矿,(并与黑电气石,铁绿泥石,磷灰石,与伊利石-白云母伴生),它们以微小残留物形式产出在菱镁矿和白云石1中,其形成可能早于M1变质作用高峰期。M1变质事件的高峰期以富铁金云母,镁绿泥石1,镁电气石(黑电气石的边缘)和石英的组合为代表。在M1退变质作用过程中,发生了镁交代作用,开始是白云石1结晶,接下来形成菱镁矿,最后是以铁菱镁矿沿裂隙的形成而终。根据碳酸盐地质测温原理,M1变质事件的高峰期温度为460~490℃,变质矿物组合特征也支持这一测温结果。滑石,白云石2,与镁绿泥石2沿着镁碳酸盐岩石裂隙的发育,主要受到M2变质事件的影响,这个变质事件与较年青的Alpine造山事件有关。 菱镁矿流体包裹体的研究表明,成矿流体具有复杂的组成,可能以MgCl2组分为主,主要来     

斯洛伐克西喀尔巴阡山Koice-Medvedia菱镁矿床的矿物学、流体包裹体和碳-氧-锶同位素研究

Kosice矿床是斯洛伐克第二大的菱镁矿床(150Mt),位于Gemeric的东部。其镁质碳酸盐矿体赋存于石炭纪石灰石和含白云石的石灰石中,同时下盘黑色片岩中也含有被铁质碳酸盐交代的薄层碳酸盐透镜体。在华力西期造山运动(M1)中,古生代岩石受到了低级变质作用(绿泥石带)。镁交代作用始于白云岩1的结晶作用,其后形成菱镁矿,最终沿裂隙形成铁菱镁矿。铁质碳酸盐包括早期铁白云石-白云石,铁白云石和后期含方解石和石英的菱铁矿。根据碳酸盐矿物对地质温度计,白云石1结晶作用发生在300~340℃。这一结果与M1的变质矿物组合(绿泥石,白云母-伊利石)吻合。铁白云石的结晶作用发生在320~370℃.少量细脉中可见白云石2,绿泥石和伊利石-多硅白云母,它们是由于阿尔卑斯期造山运动M2变质作用形成的更晚的矿物组合。 菱镁矿的流体包裹体(FI)研究,显示存在不同成分的热卤水,卤水成分变化相当于NaCl含量21~42wt％,但其它成分的盐含量高于NaCl,溶解的CO2含量也有变化。两相包裹体均一温度(Th)的范围为164~217℃,含石盐子晶包裹体均一温度的范围为217~344℃。富CO2包裹体(盐度相当于NaCl含量1-22wt％,CO2的密度为0.28~0.77 g·cm-3,均一温度为289~344℃)在菱镁矿中是次要的,但这种包裹体在与矿石伴生的石英中是主要的,并且与含石盐