The diversity dynamics of the Anisian ammonoids is analyzed in terms of generic richness and turnover rates in one North American (Nevada) and two western Tethyan (Eastern Lombardy, Balaton Highland) regions. Two pulses of diversification are outlined: one in the middle Anisian (Pelsonian) and another near the end of the late Anisian (late Illyrian). The Pelsonian global diversification is interpreted as an effect of global sea-level rise. In the early late Anisian the ammonoid generic richness definitely decreased both in the western Tethys and in Nevada. The latest Anisian peak of ammonoid diversity was low in Nevada, which is explained by the uniform local sedimentary environment and the absence of major global changes. In the western Tethys the late Illyrian diversity peak was very prominent: ammonoid generic richness, turnover and proportion of originations were very high. This explosive peak is interpreted in terms of major changes of two regional environmental factors: coeval volcanic activity and the control of nearby carbonate platforms. The late Illyrian volcanic ash falls provoked a dramatic increase of ammonoid generic richness by fertilization, i.e. supplying nutrients and iron, thus increasing primary productivity in the ocean. Carbonate platform margins offered diverse habitats with new, empty niches; the microbial mats supplied suspended organic matter for the higher trophic levels and eventually the ammonoids. In the western Tethyan regions platform growth re-appeared after the end-Permian crisis, and significantly increased in the late Illyrian. This was closely followed by the remarkable increase of ammonoid generic richness. Many of the genera which originated during the late Anisian seem to be ecologically connected to the platform or peri-platform environments. It is suggested that this explosive diversity peak is a manifestation of the co-evolution of the Tethyan carbonate platforms and the ammonoids.
The Serow ophiolite in NW Iran, located at the Iran-Turkey border, is composed of mantle sequence peridotites, predominantly lherzolitic-harzburgite with subordinate amounts of lherzolite and dunite, and a crustal sequence made from gabbros, diabases, pillow lavas and deep marine carbonates and radiolarite sediments. The rocks appear as a tectonic mélange. This ophiolitic complex forms part of the ophiolites marking a branch of Neotethys oceanic crust in NW Iran. The chemistry of olivine, orthopyroxene and clinopyroxene in the lherzolitic-harzburgite and clinopyroxene in the gabbros suggests a supra-subduction setting for the ophiolite. The Serow ophiolite is similar to other ophiolites in NW Iran such as the Piranshahr, Naghadeh and Khoy and NE Turkey ophiolites in terms of the rock units, tectonic setting and age. The Serow ophiolite links the Iranian ophiolites from Baft in the SE through the South Azerbaijan suture to the Izmir-Ankara-Erzincan suture in the NW.
The Little Plain Basin is one of the largest units in the Pannonian Basin System. Its continuation in Slovakia is called the Danube Basin. The Little Plain Basin is one of the most underexplored areas in Hungary. Based on archival geologic and geophysical data the lithostratigraphic composition of the area is controversial. The significance of the area is increased by the known Neogene and the supposed basement (Paleozoic and Mesozoic) hydrocarbon systems in Hungary and in Slovakia.
The purpose of this study is to identify the exact age, facies, geologic formations and possible source rocks of the Triassic section penetrated by the Gyõrszemere-2 well in the Little Plain Basin.
Based on new facies and paleontological results it can be stated that two Triassic sequences are identified in the well, separated by fault breccia. A carbonate sequence was deposited between the Induan and Early Anisian and above that a homogeneous recrystallized dolomite appears, the age of which is unknown.
The following formations were encountered, from base upward:
Arács Marl Fm. (3,249.5–3,030 m), silty marl with ooids, bivalves, gastropods and ostracode shells. Occasionally layers of angular quartz grains in large quantities appear. Postcladella kahlori and Spirobis phlyctaena indicates Induan (Early Triassic) age.
Köveskál Dolomite Fm. (3,030–2,790 m), rich in ooids and also containing anhydrite. The Glomospira and Glomospirella dominance indicates an age interval between Olenekian and earliest Anisian age.
Fault breccia (2,790–2,690 m) separating the Köveskál and overlying dolomites.
Upper dolomite (2,690–2,200 m): homogeneous, saccharoidal, and totally recrystallized. The age is unknown.
The low TOC values of the supposed source rock interval (marl between 3,249.5 and 3,030 m) indicate poor hydrocarbon potential.
In this paper we reconstruct the tectonic evolution of Eastern Turkey, the Lesser Caucasus and NW-N Iran from the Late Carboniferous to Recent. NW Iran is one of the most complicated regions of the country, that with Turkey and the Lesser Caucasus is influenced by movements of the Arabian Plate. The Ahar Block, which is bounded by the Tabriz, Talysh, Araks, Myaneh and Allahyarlu-Hovai Faults, underwent compression and faulting. The block shows counterclockwise rotation through the confining faults and is being compressed by northward pressure from the Arabian Plate. The age and the nature of the Allahyarlu ophiolite, which is located at the northern boundary of the Ahar Block, are not known unequivocally. During the Late Carboniferous the Allahyarlu-Kaleybar-Northern Iran Basin opened, and Neotethys 1 was spreading. During the Permian the Allahyarlu-Kaleybar-Northern Iran Basin changed from a passive to a convergent environment and closed at Late Triassic to Early Jurassic time. In the Early Jurassic Neotethys 1 began to be subducted, causing the opening of the Sevan-Akera back-arc basin. Thereafter the Sevan-Akera Basin and the Neotethys 2 Basin were widening up to the Late Jurassic. The Black Sea-South Caspian Sea-Kopet Dagh Basin opened during the Jurassic. These basins were widening up to the Paleocene, but northward slider replacement of NW Iran caused the separation of the Caspian Sea Basin and the Black Sea Basin and the formation of the Kurdamir Uplift. In the Late Cretaceous the Central Iran basins were closed and the inner-Iran ophiolites were emplaced. Neotethys 1 closed in the Late Cretaceous and Neotethys 2 in the Late Miocene.
Systematic structural and anisotropy of magnetic susceptibility (AMS) measurements were carried out on Cenozoic clay-rich deposits from the Transdanubian Range, central part of the Alcapa Unit. The aim was to improve the knowledge of the Neogene tectonic evolution of the area and of the connection of the stress field and the magnetic fabric of the sediments. The measurements of AMS revealed dominant foliation with weak lineation for Middle Eocene-Lower Miocene sediments. The directions of AMS lineation are aligned either with the direction of NNE-SSW extension of a strike slip phase (30–19 Ma) or with the direction of NE-SW extension of the main rifting phase of the Pannonian Basin (19–14 Ma).The studied Late Miocene sediments have foliated AMS fabric, maximum and intermediate AMS directions are intermixed, and the AMS fabrics do not show any sign of tectonic deformation. In contrast, joints and faults were observed in the same rocks. Detailed structural analysis shows two extensional phases between ca. 10–4 Ma, with E-W to WNW-ESE and with NW-SE extension, respectively, and the youngest neotectonic strike-slip phase. The contrast between the presence of markers of brittle deformation and the absence of tectonically-induced AMS lineation is striking, since the same types of sediments in the South Pannonian basin show just the opposite. The explanation may be that northward-moving and CCW-rotating Adria caused strong compression in the southern Pannonian Basin, resulting in ductile deformation of the clay-rich sediments and systematic reorganization of AMS texture, while in our study area sediments of similar character and age were at a larger distance from the strongly deforming basin part.
Numerous accumulations of CO2 and nitrogen-rich natural gas are known in the hot Pannonian Basin System (PBS), where even the mixture of these two fluids is a common phenomenon. The Danube Basin, part of the PBS, is characterized by the predominance of CO2 and nitrogen-rich natural gas over “normal” natural gas. The multistacked Répcelak and Mihályi gas accumulations (southern, Hungarian part of the Danube Basin) display an upward increase of nitrogen-rich natural gas at the expense of CO2. This study, using the abundant public data, the published results and the new biomarker data obtained from oil traces, attempts to explain the formation of these multistacked accumulations. A synoptic view of the vertical changes in gas composition, the maturation history of the basin and its basement, the chronology of the Neogene basaltic volcanism and the biomarker pattern of the oil traces resulted in the recognition of the metasedimentary origin of the nitrogen-rich natural gas and in a relative chronology of the mixing of the two gases and the oil.
Crystal inclusions (plagioclase, biotite, magnetite) and melt inclusions were studied in minerals of the Laleaua Albă dacite (Baia Sprie, Romania). Electron microprobe analysis of 29 melt inclusions in the plagioclase, K-feldspar, and quartz confirm that crystallization of these minerals took place from typical silicic melts enriched in potassium relative to sodium (K2O/Na2O = 1.5). The sum of the petrogenic components is 92–99 wt%. This points to a possible change in water content from 8 to 1 wt% during crystallization of phenocrysts. According to ion microprobe analysis of 11 melt inclusions, the minimum water content is 0.5 wt%, and the maximum water content is 6.1 wt%. The presence of high-density water fluid segregation in one of the melt inclusions suggests that the primary water content in the melt could reach 8.4 wt%. Ion microprobe data revealed a high concentration of Cu (up to 1260 ppm) as well as higher U content (from 5.0 to 14.3 ppm; average 11.5 ppm) in some melt inclusions as compared to the average U contents in silicic melts (2.7 ppm in island-arc settings and 7.9 ppm in continental rift settings). Chondrite-normalized trace-element patterns in melt inclusions suggest a complex genesis of the studied magmatic melts. Contents of some elements (for instance Sr and Ba) are close to those in island-arc melts, while others (for instance Th, U, and Eu) resemble those in melts of continental settings.
Partial and pervasive dolomitization of foreslope and toe-of-slope deposits of an early Carnian carbonate platform was investigated to understand the process and mechanism of dolomitization. Based on petrographic observations and C and O isotope data, the dolomitization took place in a near-surface to shallow burial setting; seawater of slightly elevated salinity was likely the dolomitizing fluid. The circulation system was maintained by reflux of evaporated sea water and geothermal heating of cold seawater derived from the surrounding deeper basin. The dolomitization was mostly controlled by the permeability of the platform-derived calcareous sediments.
The issue of settlement and the calculation of the thickness of the deformation zone are addressed in this paper. A short overview is given concerning the thickness of the deformation zone values used in general practice; the available soil models are also briefly introduced. A particular problem is used to compare the results of obtained depth of the influence zone calculated by available formulae and estimated by finite element analyses with different soil models, such as the “hardening soil”, the “Cam-Clay” and the “hardening soil with small strain” models. The deformation zone of a soft clay layer beneath a 10 m-high and 80 m-wide embankment is evaluated, and the results are compared. Special attention is given to the soil models and their capabilities and drawbacks for calculation of deformations due to large embankments.
This study demonstrates a method to identify and characterize some facies of turbiditic depositional environments. The study area is a hydrocarbon field in the Sava Depression (Northern Croatia). Its Upper Miocene reservoirs have been proved to represent a lacustrine turbidite system. In the workflow, first an unsupervised neural network was applied as clustering method for two sandstone reservoirs. The elements of the input vectors were the basic petrophysical parameters. In the second step autocorrelation surfaces were used to reveal the hidden anisotropy of the grid. This anisotropy is supposed to identify the main continuity directions in the geometrical analyses of sandstone bodies. Finally, in the description of clusters several parametric and nonparametric statistics were used to characterize the identified facies. Obtained results correspond to the previously published interpretation of those reservoir facies.