ISSN:0072-1050    

DOI:10.1002/gj.3350280302

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractRemnants of two ‘Palaeotethyan’ oceanic basins are exposed in the Central Pontides of northern Turkey, separated by a continental sliver and an oceanic arc. The southern basin corresponds to the main Tethys (‘Palaeotethys’), which partially closed in Early Mesozoic time following northward subduction under the southern, active continental margin of Eurasia.The northern basin (Küre Complex) opened above the ‘Palaeotethyan’ subduction zone as a marginal basin, following rifting of a continental fragment (Istanbul fragment) from Eurasia. Marginal basin opening apparently dates from the Late Palaeozoic in the east (Küre basin) and from the Triassic in the west (Kocaeli basin). Basin closure was achieved by southward subduction‐accretion, in pre‐Late Jurassic times, leaving ‘Neotethys’ open to the south.Counterparts of the Küre Complex are found in the adjacent Crimea (Taurian Series), Istranca (Zabernevo Complex), Dobrogea (Nalbant flysch) and Caucasus (pre‐Late Jurassic Southern Slope Basin) regions. Basin opening was accompanied by oceanic crust genesis, at least in the Pontides and Caucasus. Closure before Mid‐Jurassic time was achieved by subduction‐accretion processes, whereby oceanic crust and deep‐sea sediments (including sulphides) were detached and structurally assembled, while oceanic basement was subducted. Marginal basin opening and closure is seen as one in a series of events along a long‐lived, active s

ISSN:0072-1050    

DOI:10.1002/gj.3350280303

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe eastern end of the Sivas Basin, just west of Erzincan, is known as the Kemah Basin. The lithostratigraphy of the Kemah Basin thus corresponds with the general characteristics described for the Sivas Basin: the upper stratigraphic sequence begins with the Kemah Limestones of Burdigalian age. Above these, the sediments (grey limy marls, sandstones and conglomerates) are not yet dated, but probably span Late Miocene to Plio‐Quaternary times. The lower sequence is made of (Late Oligocene?) non‐fossiliferous, mainly continental deposits (variegated clays, silts and gypsum at the base; conglomerates, sandstones and some volcanics in the footwall of the limestones).Both the basin deposits and substratum (arc volcanics, volcanoclastics and ophiolites) are involved in thrust systems with displacements consistently directed to the SSE. The sequence of thrusting deduced from the geometrical pattern of the imbricate zone and from the stratigraphic record includes at least two stages of thrust propagation. The sequence shows the rise of successive waves of active new thrusts and folds from the north, cutting through earlier thrusts in a general ‘break‐back’ sequence. The southern edge of the Neogene basin against the ophiolites covering the Munzur Limestones (Taurides) shows a moderate northward tilting.A first attempt at a (incomplete) balanced cross‐section and restoration along the Burdigalian limestones as datum gives a minimum displacement of 11 km along a section length of 12 km. The kinematics and the contraction ratio question the concept of an ‘Anatolian block’ and related displacement models during t

ISSN:0072-1050    

DOI:10.1002/gj.3350280304

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe study area is located in the southern part of the Central Pontides. The rocks exposed in this region have been divided into three major groups: basement, cover sequence and volcanic rocks. The basement rocks are composed of metamorphic units and a chaotic assemblage derived from an accretionary prism produced during the northward subduction of northern Neo‐Tethys during the Late Cretaceous. During the same period, the basal element of the cover sequence, a thick and coarsening upward flysch succession (Cankurtaran Formation) was deposited in a tectonically active forearc regime. Towards the end of the Early Palaeocene, the entire study area emerged and became the site of erosion. During the Late Palaeocene to Early Eocene, the northern and southern parts of the study area were invaded by a new transgressing sea. This period was followed by uplift, volcanic activity and the formation of regressive sequences, events resulting from continental collision between the Anatolian and Pontide blocks during Late Eocene to Early Miocene times.Continuing convergence between the Anatolian and Pontide blocks resulted in conversion of the compressional‐contractional regime into a compressional‐extensional regime and the inception of the North Anatolian strike‐slip system during the Late Miocene‐Early Plioce

ISSN:0072-1050    

DOI:10.1002/gj.3350280305

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractMélanges are usually dated from the ages of contained blocks and of the oldest unconformably overlying cover rocks. Anomalies associated with this approach are illustrated in this study of the principal mélange belts developed in Anatolia.The Karakaya Mélange belt of supposed Middle Triassic inception and the Ophiolitic Mélange belt of supposed Late Cretaceous age are readily distinguished in western Turkey but their outcrops converge eastwards, the two belts merging in Central Anatolia and becoming intermingled further east, near Sivas, where the ages and natures of the mélange belts are problematic. Thus parts of the mélange attributed to the Karakaya belt contain blocks of younger limestone (Jurassic to Early Cretaceous or even younger), whereas outcrops attributed to the Ophiolitic Mélange include blocks of clastics of Late Palaeocene‐Early Eocene or even Mio‐Pliocene age. This situation confers apparently ‘younger’ ages of formation on these mélanges. It is suggested that such anomalies result from contamination by younger blocks as a result of local remobilization of the mélanges during subsequent tectonic disturbances.A north‐south oriented area, 45 km long and 20 km wide, crossing the complex mélange zone east of Sivas, has been mapped at a 1:25 000 scale and provides critical evidence on this question. It appears that the Karakaya Mélange (or its equivalent) may have been remobilized at least four times and the Ophiolitic Mélange at least three times since their inception. During each subsequent tectonic event the mélanges have incorporated some parts of the younger deposits which formed on top of them in the interven

ISSN:0072-1050    

DOI:10.1002/gj.3350280306

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe provenance of the deep marine clastics of the Cingöz Formation, which were deposited contemporaneously during the Miocene as two small neighbouring submarine fans (western and eastern fans) in the northern part of the Adana Basin, has been studied by: (1) thin section petrography; (2) the use of the ternary discriminant diagrams (Q‐F‐L, Qm‐F‐Lt) of Dickinsonet al. (1983); and (3) the use of discriminant function analysis (DFA) techniques.Thin section petrography confirms that the compositions of sandstones in both the western and eastern fans are broadly similar, but they display subtle differences which are related to their local sources. Both of these submarine fans were ultimately supplied from a source area which contained ophiolitic, sedimentary, metamorphic and some felsic igneous rock types.The point counting results have been plotted on the ternary diagrams of Dickinsonet al. (1983). On this basis, most of the samples can be assigned to a magmatic arc provenance, with some recycling. There appears to be no significant difference in provenance between these two fans on the basis of these ternary diagrams.Discriminant function analysis of the same data, utilizing the original Dickinsonet al. (1983) data set, reveals some otherwise undetected differences in provenance between the two fans. This test also shows that the DFA of sandstones for petrotectonic purposes should be improved by adding further actual data to the data set originally assembled by Dickinsonet al. (1983). Moreover the DFA results confirm that in this instance erroneous petrotectonic inferences can be drawn from the Dickinsonet al. ternary diagrams as a result of the complex tectonic history of the source, although clues to this complexity can be discerned in the DFA data, provided that the full set of Dickinson categories is deployed. Taken together with the abundant field data these analyses show that the sands and gravels forming these small Mid‐Miocene submarine fans were supplied to the deep marine Adana Basin via two main separate point sources, together with some minor point sources, all located in the Taurus orogenic belt, on the northern margin of the A

ISSN:0072-1050    

DOI:10.1002/gj.3350280307

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWithin the framework of an integrated stratigraphy, a detailed biostratigraphic study of Late Jurassic‐Early Cretaceous (Tithonian‐Valanginian) calcareous nannofossils was carried out in north‐west Anatolia, Turkey.Samples were collected from nine sections spanning the Yosunlukbayiri and Sogukçam Limestone formations. The Yosunlukbayiri Formation consists of alternating green to cream coloured marl and micritic limestone that becomes detrital (calciturbidites) in the upper part. The Sogukçam Limestone Formation, which overlies the Yosunlukbayiri Formation, consists of white to pink, porcellaneous micritic limestone. A semi‐quantitative analysis of calcareous nannofossils was performed mainly using light microscopy. This revealed the first and last occurrences of important marker species, together with fluctuations of abundance and species diversity.Nannofossil assemblages are generally dominated by the most abundant and solution resistant taxa, such asConusphaeraspp.,Faviconus multicolumnatus, Nannoconusspp. andWatznaueriaspp., and occur in rock‐forming quantities. Five zones (Conusphaera mexicana mexicanaZone,Microstaurus chiastiusZone,Nannoconus steinmannii steinmanniiZone,Retecapsa angustiforataZone,Calcicalathina oblongataZone) and 37 biohorizons were recognized from the Tithonian to Valanginian and calibrated to the Calpionellid (Altiner and Özkan 1991) and the foraminiferal‐algal zonation schemes

ISSN:0072-1050    

DOI:10.1002/gj.3350280308

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn south‐eastern Turkey, a transgressive phase with a rich benthic foraminiferal association followed the Late Cretaceous emplacement of nappes onto the passive northern margin of the Arabian Platform. At the base, this transgressive sequence is represented by coarse clastics and local carbonate intercalations of the Antak Formation and the overlying, shallow water friable sands and carbonate facies of the Besni Formation, which is characterized by a sudden proliferation of benthic foraminifera, rudists and other macrofossil groups. Finally, below the unconformable Tertiary units, the more basinal marls and regressive sandstone‐carbonate lithologies of the Germav Formation complete the Mesozoic succession.In the light of the newly discovered benthic and planktonic foraminiferal associations, the age of this transgression has been assigned to the Late Campanian. Overlying levels yield more diversified foraminiferal assemblages including genera such asOrbitoides, Siderolites, Omphalocyclus, Loftusia, Lepidorbitoides, Sirtinaand other benthic taxa suggesting a Maastrichtian age. However, biometric analysis of the embriyon size of theOrbitoidespopulations from these levels show that these specimens are more primitive than the type Maastrichtian fo

ISSN:0072-1050    

DOI:10.1002/gj.3350280309

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe horizontal motions of the lithospheric plates generally range from a few millimetres to more than 150 mm/year; smaller motions are expected in the vertical direction. The measurement of such small relative movements has been made possible by the development of satellite geodesy [satellite laser ranging (SLR) and the global positioning system (GPS)] followed by very long baseline interferometry (VLBI). It is now possible to measure motions of less than a few millimetres per year from space.To monitor the relative movements in the Eastern Mediterranean region, SLR measurements to the LAGEOS satellite have been made within the WEGENER MEDLAS Project (Working Group of European Geoscientists for the Establishment of Networks for Earth Science Research Mediterranean Laser Ranging) since 1986 on four platforms in Turkey: Bolu/Yigilca [on the north side of the North Anatolian Fault (NAF)], Yozgat, Karaman/Melengiclik and Diyarbakir (on the Anatolian plate) as well as on six additional sites in Greece. The first results of the measurements made in 1986, 1987 and 1989 support earlier seismic results. The results from the SLR campaigns indicate a right‐lateral motion across the NAF. The results of two GPS campaigns carried out in 1988 and 1990 in north‐west Turkey indicate similar movements.The NAF shows a right‐lateral movement of 25 mm/year and the north‐western part of the Anatolian block escapes south‐west at a rate of 50 mm/year; more than expected.Up to the studies of Oralet al.(1992), the results of the vertical motions of the SLR and GPS campaigns coincide and show a surprisingly high rate for the station on the Anatolian peninsula of about 5 cm/year

ISSN:0072-1050    

DOI:10.1002/gj.3350280310

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe earthquake of 13 March 1992 (Ms = 6·8) in the densely populated Erzincan region of eastern Turkey resulted in about 500 deaths, at least 2000 people injured and widespread destruction of buildings. The results are presented of field observations carried out within the Erzincan Basin immediately after the earthquake. The main area of surface deformation is about 55 km2in extent and lies 15 km south‐east of Erzincan. Surface fractures with significant displacements were observed with orientations as follows: strike‐slip 095–110° (dextral), 040° (sinistral) and 090° (sinistral); extensional 150–180°. Most of the observed fractures are consistent with the Harvard centroid moment tensor solution for the main shock, which indicates north‐south compressional and east‐west extensional principal horizontal stress axes. It is suggested that the earthquake probably occurred as a result of dextral strike‐slip motion on a segment of the North An

ISSN:0072-1050    

DOI:10.1002/gj.3350280311

出版商:John Wiley&Sons Ltd    

年代:1993

数据来源: WILEY