The effects of a lateral variation in lithospheric strength on foredeep evolution: Implications for the East Carpathian foredeep

Lateral variations in lithospheric strength have been adopted often in flexural modeling (both 2D and 3D) to better fit the observed basement deflections, typically supported by gravity data. This approach provides essentially a “snap-shot” of the role of lithosphere strength in determining the present day geometry.In contrast, we investigate and quantify the effects of a lateral change in lithospheric strength on the evolution of the foredeep in front of an advancing orogen. Transitions in lithospheric strength are common in the foreland of orogens and show large variations in the width of the transition zone and the strength difference. Former passive margins, for instance, will display strength changes distributed over several tens to hundreds of kilometers. Other transitions may originate from juxtaposition or accretion of pieces of lithosphere with different properties and may be characterized by a much smaller width than former passive margins.In our modeling, a constant load, representing an advancing orogenic belt, is displaced towards and across a transition from a weak to a strong plate in a 2D elastic thin plate model. The effect of different transition widths and strength contrasts on foredeep geometry and bending stress is investigated. Interference of flexural wavelengths across the transition affects foredeep geometry by causing rapid basin widening, oscillation of the bulge and volume increase. The bending stresses are found to concentrate and amplify around the strength transition. Large transition gradients, i.e. large strength contrast or small transition width, cause the highest rates of change.Basin widening caused by the orogenic load advancing towards the transition between the East European Craton and the Moesian Platform, appears to control the Sarmatian transgression over the East Carpathian foreland in Romania.     

Vertical movements in and around the south-east Carpathian foredeep: lithospheric memory and stress field control

A > 10‐km‐thick basin formed in Tertiary to Quaternary times in front and overlapping with the south‐east Carpathians. The Foc?ani Depression is part of this system and overlies the Vrancea seismogenetic volume, thought to correspond to the remnants of the continental slab subducted beneath the Carpathians. Slab detachment and its lateral migration are considered to control vertical movements in the area. We present the first complete analysis of subsidence patterns in the Depression and derive a substantially different picture. The strongest subsidence is Sarmatian in age, coeval with the main nappe emplacement events. Subsequently, subsidence did not stop and persisted until present times despite cessation of thrusting. The main depocentre remained the Foc?ani Depression and no significant lateral migration is detected. Post‐Sarmatian subsidence is contemporaneous with major exhumation/erosion in the Carpathians. The evolution of the basin is associated with a combination of vertical and far‐field horizontal stresses, and its position is controlled by pre‐existing lithospheric heterogeneities.     

Foraminiferal record of marine transgression during deposition of the Middle Miocene Badenian evaporites in Central Paratethys (Borków section,Polish Carpathian Foredeep)

Benthic and planktonic foraminifera from a marly clay intercalation sandwiched between mid‐Badenian (Middle Miocene) gypsum deposited in an environment of an evaporitic shoal (<1 m deep) at Borków (southern Poland) indicate a major marine flooding event in the previously isolated Carpathian Foredeep Basin (Central Paratethys). After this very short‐term environmental change, benthic foraminifers started to colonize a new niche which was previously defaunated, and the pattern of benthic foraminiferal colonization is similar to that related to the reflooding which terminated the Badenian evaporite deposition. The benthic foraminifer assemblages are composed of pioneer, opportunistic, r‐selected species dominated by elphidiids. The connection of the Carpathian Foredeep Basin with the marine reservoir was short‐lived. The marly clay intercalations in evaporite sequences originating in bared basins can thus register major environmental changes.     

Late Cretaceous to early Miocene deposits of the Carpathian foreland basin in southern Moravia

 The Late Cretaceous to Early Miocene strata of the Carpathian foreland basin in southern Moravia (Czech Republic) are represented by a variety of facies which reflects the evolution of the foreland depositional system. However, because of the intensive deformation and tectonic displacement and the lack of diagnostic fossils the stratigraphic correlation and paleogeographic interpretation of these strata are difficult and often controversial. In order to better correlate and to integrate them into a broader Alpine–Carpathian foreland depositional system, these discontinuous and fragmentary strata have been related to four major tectonic and depositional events: (a) formation of the Carpathian foreland basin in Late Cretaceous which followed the subduction of Tethys and subsequent deformation of the Inner Alps-Carpathians; (b) Middle to Late Eocene transgression over the European foreland and the Carpathian fold belt accompanied by deepening of the foreland basin and deposition of organic-rich Menilitic Formation; (c) Late Oligocene to Early Miocene (Egerian) uplifting and deformation of inner zones of the Carpathian flysch belt and deposition of Krosno-type flysch in the foreland basin; and (d) Early Miocene (Eggenburgian) marine transgression and formation of late orogenic and postorogenic molasse-type foreland basin in the foreland. These four principal events and corresponding depositional sequences are recognized throughout the region and can be used as a framework for regional correlation within the Alpine–Carpathian foreland basin. Received: 18 August 1998 / Accepted: 9 June 1999     

Petrologic studies of terrestrial organic matter in Carpathian flysch sediments, southern Poland

In the Carpathian Flysch, coal is present either as exotics of Carboniferous coal deposits or as autochthonous, thin layers of lustrous coal. This paper present the results of the studies of coal-bearing rocks that are coeval with the enclosing flysch sediments. These coals form lenses up to 0.15 m thick. Their morphology precludes an exotic origin. The main petrographic component is collinite with admixtures of poorly fluorescing telinite. Minor components are: exudatinite, sporinite, fusinite, micrinite and sclerotinite. Mineral matter consists of framboidal pyrite clay minerals and quartz.The random reflectance of telocollinite varies from 0.38% to 0.72%, which corresponds to subbituminous and bituminous ranks. Correlation between chemical analysis, coking properties and relfectance measurements, leads to the conclusion that boundary between subbituminous and bituminous coals should be defined by the following values: C=80wt%, VOLATILES=43wt%; calorific VALUE=32.3 MJ/kg; and R^o=0.56–0.57%.Atypical properties, such as: upper C value (75–80wt%); high volatile matter contents (over 43wt%) and low random reflectance (^o about 0.38–0.57%) in subbituminous coals; low C value (about 80–82wt%); low reflectance (0.56–0.72%); and good coking properties, of the bituminous coals are attributed to quick coalification during increasing temperature as a result of tectonic stress.     

Paleomagnetism and magnetostratigraphy of Upper Cretaceous and Cretaceous-Paleogene boundary intervals,southern Kulunda basin (West Siberia)

The study presents new paleomagnetic data on the Upper Cretaceous and Cretaceous-Paleogene boundary intervals of the southern Kulunda basin (Alei area), which were obtained from core samples collected from a 305-m-thick section penetrated in two wells. The paleomagnetic sections of each well were compiled and correlated based on the characteristic remanent magnetization (ChRM). Paleomagnetic, geological, stratigraphic, and paleontological data were used to compile the Upper Cretaceous and Cretaceous-Paleogene magnetostratigraphic section of the southern Kulunda basin. The magnetostratigraphic section consists of five magnetozones, one normal polarity zone, and four reversed polarity zones spanning the Upper Cretaceous and Lower Paleogene. The lower part of the Gan’kino Horizon, showing normal polarity, forms a single normal polarity magnetozone N. The upper part of the Gan’kino Horizon comprises two reversed polarity magnetozones (R₁km and R₂mt). The Talitsa and Lyulinvor Formations of Lower Paleogene age correspond to two reversed polarity magnetozones (R₁zl and R₂i). The compiled Upper Cretaceous and Lower Paleogene magnetostratigraphic section was correlated with the geomagnetic polarity time scale. Two options were considered for correlating the lower normal polarity part of the section with geomagnetic polarity time scale of Gradstein.     

Sedimentation in the Carpathian Flysch sea

On the ground of the sedimentary features of the Flysch the general conditions of sedimentation in the Carpathian Flysch sea are tentatively reconstructed. It is admitted that the Carpathian Flysch has been deposited in a fairly deep basin under the influence of turbidity currents. The directions of transport are presented and the distances covered by currents estimated. Some inferences concerning the shape and relief of the basin are discussed.     

Variability of natural effluents as an indicator of groundwater retention in the Carpathian foothills (southern Poland)

 Research into the patterns of natural underground water effluents has been conducted in a small catchment basin (Wierzbanówka) that is representative of the Carpathian foothills. The aim of this study was to understand the long-term dynamics of the effluents and their responses to natural and artificial factors in order to estimate groundwater resources. High variability of the effluent patterns in the Carpathian foothills is a result of precipitation fluctuations, low ground retention capacity, a low rate of absorption in the flysch rock formation areas, and of the Quaternary covers. In addition, the dominance of agricultural land use, low forest coverage, and poor hydrological management are the main causes of this variability. Any local increase in underground water resources would only be possible if forests were planted on some of the agricultural land and changes were made to water management. Received: 16 August 1999 · Accepted: 12 January 2000     

Palaeogeographic and burial controls on anhydrite genesis: the Badenian basin in the Carpathian Foredeep (southern Poland, western Ukraine)

The Badenian (Middle Miocene) Ca-sulphate deposits of the fore-Carpathian basin – including the shelf and adjacent salt depocentre – have undergone varying degrees of diagenetic change: they are preserved mainly as primary gypsum in the peripheral part of the platform, whereas toward the centre of the basin, where great subsidence occurred during the Miocene, they have been totally transformed into anhydrite. The facies variation and sequence of Badenian anhydrites reflect different genetic patterns of two members of the Ca-sulphate formation. In the lower member (restricted to the platform), anhydrite formed mainly by synsedimentary anhydritization (via nodule formation), whereas in the upper member (distributed throughout the platform and depocentre) the various gypsum/anhydrite lithofacies display a continuum of distinctive anhydrite type-fabrics. These fabrics are based on petrographic features and show from the centre to the margin: (1) syndepositional, interstitial growth of displacive anhydrite; (2) early diagenetic, displacive to replacive (by replacement of former gypsum) anhydrite formation near the depositional surface; (3) early diagenetic, displacive to replacive anhydrite formation during shallow burial; and (4) late-diagenetic (and only partial) replacement of gypsum at deeper burial. The cross-shelf lateral relations of anhydrite lithofacies and fabrics suggest that the diagenesis developed as a diachronous process. These fabrics of the upper member reflect both palaeogeographic (linked to different parts of the basin) and burial controls. Anhydrite growth started very early in the basin centre, presumably related to high-salinity pore fluids; anhydritization prograded updip toward the shelf (landward in a generalized cross-section through the basin). The intensity of gypsum replacement by anhydrite was progressively attenuated landward by a decrease in the salinity of the pore fluids. In each part of the basin, the anhydrite fabric was also controlled by the texture and degree of lithification of the fine-grained primary gypsum lithofacies. Recrystallization of these anhydrite fabrics during late diagenesis, linked to deeper burial conditions, is insignificant, allowing reconstruction of the original anhydritization pattern.     

Phosphate-rich deposits associated with the Mio-Pliocene unconformity in south-east Australia

Phosphates are present on the surface of the Mio-Pliocene unconformity in the Otway, Port Phillip and Gippsland basins of south-east Australia. The phosphates occur as lenticular lag deposits and include reworked phosphatic intraclasts, vertebrate bone and teeth. In situ phosphatized burrows are also found in sediments of Late Miocene and Early Pliocene age. The phosphatic intraclasts on the unconformity are interpreted as reworked phosphatized burrows derived from latest Miocene sediments (6 to 5 Ma). The phosphatization of these intraclasts is temporally related to the unconformity. The timing of phosphogenesis coincides with a period of transgression across the south-east Australian margin following Late Miocene uplift. This transgression is responsible for initial marine erosion of the underlying Miocene sequence, creation of a period of very slow sedimentation that was favourable to phosphate formation and subsequent deposition of the latest Miocene through to Pliocene sediments. The continental weathering of the uplifted highlands adjacent to the sedimentary basins, global phosphorus enrichment in the Late Miocene oceans and localized upwelling may all have contributed to phosphatization in south-eastern Australia.     

Palaeomagnetism and magnetostratigraphy of the Permian–Triassic northwest central Siberian Trap Basalts

A detailed palaeomagnetic and magnetostratigraphic study of the Permian–Triassic Siberian Trap Basalts (STB) in the Noril'sk and Abagalakh regions in northwest Central Siberia is presented. Thermal (TH) and alternating field (AF) demagnetisation techniques have been used and yielded characteristic magnetisation directions. The natural remanent magnetisation of both surface and subsurface samples is characterised by a single component in most cases. Occasionally, a viscous overprint can be identified which is easily removed by TH or AF demagnetisation.The resulting average mean direction after tectonic correction for the 95 flows sampled in outcrops is D=93.7°, I=74.7° with k=19 and α₉₅=3.3°. The corresponding pole position is 56.2°N, 146.0°E.Unoriented samples from four boreholes cores in the same regions have also been studied. They confirm the reversed–normal succession found in outcrops. The fact that only one reversal of the Earth's magnetic field has been recorded in the traps can be taken as evidence for a rather short time span for the major eruptive episode in this region. However, there is evidence elsewhere that the whole volcanic activity associated with the emplacement of the STB was much longer and lasted several million years.     

Upper Cretaceous Magmatic Series and Associated Mineralisation in the Carpathian – Balkan Orogen

Abstract: The Alpine Orogen contains in South East Europe, from the Carpathians to the Balkans–Srednogorie, an Upper Cretaceous, ore bearing igneous belt: a narrow elongated body which runs discontinously from the Apuseni Mountains in the North, to the western part of the South Carpathians (Banat) in Romania, and further South to the Carpathians of East Serbia and still further East to Srednogorie (Bulgaria). This results in a belt of 750 km/30–70 km, bending from N-S in Romania and Serbia, to E-W in Bulgaria. Using the well established century-old terminology of this region, we describe it in this paper as the Banatitic Magmatic and Metallogenetic Belt (BMMB). Plate tectonics models of the Alpine evolution of South East Europe involve Mesozoic rifting, spreading and thinning of the continental crust or formation of oceanic crust in the Tethian trench system, followed by Cretaceous-Tertiary convergence of Africa with Europe and opening of Eastern Mediterranean and Black Sea troughs. The result of successive stages in the collision process is not only the continental growth of Europe from N to S by the docking of several microplates formerly separated from it by Mesozoic palaeo–oceans, but also the rise of mountain belts by overthickening of the crust, followed by orogenic collapse, lateral extrusion, exhumation of metamorphic core complexes and post-collisional magmatism connected to strike-slip or normal faulting. The BMMB of the Carpathian-Balkan fold belt is rich in ore deposits related to plutons and/or volcano-plutonic complexes. Serbian authors have proposed an Upper Cretaceous Paleorift in Eastern Serbia for the Timok zone and some Bulgarian geologists have furnished geologic, petrological and metallogenetic support for this extensional model along the entire BMMB. The existence and importance of previous westwards directed subductions of Transilvanides (=South Apuseni = Mure? Zone) and Severin-Krajina palaeo–oceans, popular in Roman ian literature, seems to have little relevance to BMMB generation, but the well documented northwards directed subduction of the Vardar-Axios palaeo–ocean during Jurassic and Lower Cretaceous is a good pre-condition for the generation, during the Upper Cretaceous, of banatitic magmas in extensional regime, by mantle delamination due to slab break–off. Four magmatic trends are found: a tholeiitic trend, a calc-alkaline trend, a calc-alkaline high–K to shoshonitic trend and, restricted to East Srednogorie, a peralkaline trend. For acid intrusives, the typology is clearly I-type and magnetite–series, pointing to sources in the deep crust or the mantle; however, some high ⁸⁷Sr/⁸⁶Sr ratios recorded in banatites prove important contamination from the upper crust. The calc-alkaline hydrated magmas, most common for banatitic plutons, can be considered as recording three stages of evolution: more primitive – the monzodioritic, dioritic to granodioritic trend (S Apuseni, S Ba–nat, Timok, C and W Srednogorie); more evolved – the granodioritic-granitic trend (N Apuseni, N Banat, Ridanj–Krepoljin); the alkaline trend (E and W Srednogorie, western part of N Banat). Correlating the composition of the host plutons with the types of mineralisation, several environments can be found in the BMMB, function of timing of fluid separation (porphyry versus non-porphyry environments), depth of emplacement, size of intrusion and geology of intruded rock pile, biotite versus hornblende crystallisation, involving the evolution of K/Na ratio in fluids, i. e. development of potassic and phyllic alteration zones: a) non-porphyry environment with granodioritic to granitic magmas, plutonic level, skarn mineralisation prevails; b) porphyry environment with monzodioritic or dioritic to granodioritic magmas, subvolcanic–hypabyssal–plutonic level; porphyry Cu with skarn halo at hypabyssal-subvolcanic level; c) porphyry environment with monzodioritic or dioritic to granodioritic magmas, volcano-plutonic complexes with porphyry copper plus massive sulfide mineralisation at subvolcanic-volcanic level; d) non-porphyry environment with magmas of alkaline tendency, volcanic level, vein (“mesothermal” and “epithermal”) mineralisation.     

Terrestrial Mio-Pliocene Boundary in the Linxia Basin, Gansu, China

The Lower Pliocene of the Linxia Basin in Gansu Province is one of only a few representative sections for the Early Pliocene sedimentary records in northern China, and even in East Asia. Recently, abundant mammalian fossils were found from the base of red clays of the Lower Pliocene Hewangjia Formation at Duikang in Guanghe County within this basin. Previously, the Pliocene mammals were sparsely found in China, and most were collected from fluvial and lacustrine deposits in the eastern Loess Plateau. Mammals from the widely distributed Pliocene Hipparion Red Clay are less in number. The known fossils from Duikang include 20 species and belong to the Shilidun Fauna. Their faunal components are similar to the Early Pliocene Gaozhuang Fauna from Yushe, Shanxi. On the other hand, some taxa from Duikang have not been found in the Gaozhuang Fauna, are slightly more primitive in evolutionary level, and appeared mainly in the Late Miocene. As a result, the age of the Duikang fossils may be slightly earlier than that of the Gaozhuang Fauna and closer to the lower boundary of the Pliocene. The Duikang fossiliferous bed is 0.8 m above the top of the Late Miocene Liushu Formation, and the first occurrence of the three-toed horse Hipparion pater can be regarded as a biostratigraphical marker of the Miocene/Pliocene boundary. In conclusion, Duikang is an ideal candidate locality to establish as the stratotype of the lower boundary of the Chinese terrestrial Pliocene.     

Bryozoan event from Middle Miocene (Early Badenian) lower neritic sediments from the locality Kralice nad Oslavou (Central Paratethys,Moravian part of the Carpathian Foredeep)

Fossil Bryozoa occurs usually in shallow-water environments. One of the rare deep-water associations of Bryozoa has been studied in a profile at Kralice nad Oslavou. According to studies of foraminifera, the paleodepth was more than 150 m and less than 500 m. The bryozoan assemblages are poor, consisting of four species only, dominated by Tervia irregularis (Cyclostomatida) and Reteporella kralicensis sp.n. (Cheilostomatida), a new species being described in detail.     

The Carpathian Mountain range and the enclosed interior

The baffling duality of the Carpathian Mountain Range and the Basin it surrounds is briefly discussed. The various attempts at solving the nature of this duality, including plate tectonics with its micro-plates are mentioned. The component ranges of the Carpathians and the structural belts are given, followed by the discussion of the Carpathian Basin System, the Interior, consisting of the Great Hungarian Plain, Transdanubia, the two groups of Central Mountains, also the Apuseni (Bihar) Mountains and the Banat Contact Belt. Economic ore deposits are featured in the relevant sections.     

Tectonic and sedimentary evolution of the Lower Pliocene Periadriatic foredeep in Central Italy

The Periadriatic foredeep (Italy) was generated by Neogene downbending of the Adria Plate under the Apennine Chain. The basin is filled with Plio-Pleistocene siliciclastic turbidites. Its substratum consists of the carbonate succession of the southwestern Adria Plate margin. The influence of the basin’s morphology on sedimentation and subsequent tectonic evolution is investigated in the Abruzzo sector of the foredeep (Cellino Basin). The substratum is composed of Messinian evaporites that dip towards the Apennines (W). A NNW component along the depocentral axis is divided into four blocks with different depths. The substratum was also affected by a Messinian extensional fault system, not involving the overlying Pliocene sequence. This morphology controlled the distribution of the turbidites in the lower part of the Cellino Basin. The Plio-Pleistocene compressional deformation of the foredeep produced an inner complex structure (Internal Structure), involving the foredeep substratum and an outer imbricate thrust system (Coastal Structure), detached over the faulted Messinian evaporites. This thrust system is parallel to the extensional faults, suggesting a strong influence of the substratum morphology on the development of the compressional structures. The overall structural setting was validated with a balanced cross-section. Out-of-sequence thrusting and non-coeval deformation within each thrust sheet characterize the local tectonic history.     

Lower miocene sediments of the Maikop group in the Central Eastern Paratethys

The composite section of upper Maikop sediments compiled for the central part of the Eastern Paratethys is presented. The section (more than 1000 m) comprises the Karadzhalgan, Sakaraulian, and Kotsakhurian regional stages. The lower boundary of the Miocene drawn at the base of the Karadzhalgan regional stage is unambiguous only in the southern part of the central Ciscaucasia. In most areas of the Ciscaucasia, this boundary is drawn arbitrarily because of uniform lithology in the Oligocene-Miocene boundary interval and poor paleontological substantiation. Generally, the Maikop sequence is insufficiently studied and incomplete in many areas because of a discordant upper boundary of the Maikop Group. Nevertheless, materials presented in the paper characterize for the first time the composition and structure of the Lower Miocene sequence over a vast area of the Eastern Paratethys. The horizonwise reconstruction of Early Miocene basins has made it possible to reveal the major features of final stages in the formation of the Maikop clayey sequence.     

Pleistocene evolution of the Danube in the Carpathian Basin

The present-day drainage system of the Carpathian Basin originates from the gradual regression of the last marine transgression (brackish Pannonian Sea). The flow directions of the rivers including the Danube, are determined by the varying rates and locations of subsidence within the region. The Danube, which forms the main axis of the drainage network, first filled the depression of the Little Plain Lake and then, further southward, the Slavonian Lake. From the end of the Pliocene, the crustal movements which caused the uplift of the Transdanubian Mountains, forced the Danube to flow in an easterly direction, towards the antecedent Visegrid Gorge, and into the subsiding basins of the Great Plain. Climatic changes during the Pleistocene had the effect of forming up to seven fluvial terraces. The uplift of the mountains is demonstrated by the deformation of the terraces, while the subsidence of the Plains is proven by an accumulation of several hundred metres of sediment. The river only occupied its present position south of Budapest in the latest Pleistocene.