South Carpathians Research Articles

Tertiary tectonic evolution of the external South Carpathians and the adjacent Moesian platform (Romania)

Depth‐interpreted seismic sections of the Getic Depression foredeep, paleostress indicator data and analysis of outcrop‐ to regional‐scale structures are integrated to derive the tectonic evolution of the South Carpathians ‐ Moesian platform area. Following Late Cretaceous and older orogenic phases, the South Carpathians ‐ Moesian platform area underwent strike‐slip deformation with NE‐SW oriented compression and NW‐SE tension. In Paleogene to Early Burdigalian times, tensional deformation is recorded which led to the opening of WSW‐ENE to E‐W trending extensional basins. In the Late Burdigalian, NE‐SW oriented contraction took over causing the oblique inversion of preexisting extensional structures. During Sarmatian times, NW‐SE and slightly younger N‐S trending compression caused the activation of mainly NW‐SE dextral strike‐slip faults and, in the frontal areas, south directed thrusting. The NW‐SE direction of extension determined for Paleogene to Early Burdigalian times is hardly compatible with presently accepted models of substantially continuous dextral wrenching between the Intra‐Carpathians units to the north of the South Carpathians and the Moesian platform to the south. In contrast, we have demonstrated dextral transpressive to transtensional movements within an E‐W trending corridor from the Late Burdigalian to Late Sarmatian which are compatible with available models.

Tectono-thermal regimes and lithosphere behaviour in the External Dacides in the Upper Triassic and Jurassic Tethyan opening (Romanian Carpathians)

Traces of Mesozoic basic magmatism occur in the Romanian Carpathians in two different tectono-stratigraphic positions: (1) associated with the opening of the Tethys, and (2) associated with intracontinental basins. The latter were generated within three sedimentary basins, which are now inverted, constituting the External Dacides: the Black Flysch, Ceahlau (Eastern Carpathians) and Severin (South Carpathians) basins. Assuming a normal Jurassic lithosphere and a pure shear opening mechanism, stretching factors of 1.25 and 1.7 have been calculated for the Black Flysch and Ceahlau basins, respectively. These values were in turn used to determine the theoretical values of the syn-rift sediment thickness, and compared with those obtained by backstripping techniques. The occurrence of basic magmatism in the Black Flysch basin associated to such a low stretching factor, suggests that melt generation was possible due to ‘wet’ composition of the mantle peridotite. The thermal state was different in the Ceahlau and Severin basins, the lithosphere being affected by updoming processes prior to rifting. Upper Triassic and Jurassic thermal states of the European lithosphere are related to the coeval opening mechanism of the Tethys. There was a transition from a simple shear between Austro-Alpine (= Apuseni Mountains) and the South Carpathians, to a pure shear mechanism (accompanied by strike-slip movements) between Austro-Alpine and the northern part of the Eastern Carpathians. Related to this change in the position of the master detachment fault, an astenospheric uprise developed within the European plate. It was largest in the Severin zone, medium in the Ceahlau zone and became smaller toward the Black Flysch zone. The Dacidian Swell developed as a result of this astenospheric rise. Starting with the Lower and Middle Jurassic, the Dacidian Swell became subject of rifting.

Kyanite-bearing eclogite from the Leaota Mountains (South Carpathians, Romania): mineral associations and metamorphic evolution

A kyanite-bearing eclogite from the pre-Alpine basement of the Southern Carpathians (Leaota Mountains, Romania) shows a complete prograde metamorphic evolution, reaching pressures in excess of 20 kbar, followed by a retrograde path with decreasing pressure and temperature. It brings new evidence that this pre-Alpine basement constitutes a continental collision belt, probably of Variscan age.

The Neoproterozoic Pan-African basement from the Alpine Lower Danubian nappe system (South Carpathians, Romania)

The South Carpathians, which were thrust to the Moesian platform in the Alpine orogeny (Late Cretaceous to Tertiary), include the Danubian nappe system. The Danubian pre-Alpine basement comprises two Variscan nappes, each one made up of partially retrogressed amphibolite facies rocks intruded by granitoids and capped by an Ordovician-Devonian volcano-sedimentary cover. No lithological correlation can be established between the pre-Ordovician basements of these two units. The metamorphic basement from the first Variscan nappe, the Drăgşan Group, is composed of banded amphibolites with some augen and aluminous gneisses intruded by granodioritic to tonalitic plutons. The banded structure of the amphibolites, together with their geochemistry, suggests a volcano-sedimentary sequence. Zircon UPb data on an intercalated augen gneiss have given an age of 777 ± 3 Ma for the emplacement of the protolith of this gneiss. Nd model ages ( T DM) for the amphibolites range from 717 Ma to 817 Ma. At 777 Ma, ϵ Nd values cluster is at +8.3 to +9.8 and Sr initial ratios range between 0.7007 and 0.7023, indicating an oceanic origin without continental crust contamination. Major and trace elements from the Drăgşan amphibolites consistently display an island arc signature, with three differentiation trends evolving from an early tholeiitic trend to a more differentiated low-K calc-alkaline one. The Drăgşan terrane is similar to the early Pan-African juvenile terranes of the Sahara. The basement of the second Variscan nappe, the Lainici-Păiuş Group, is made up of metasedimentary rocks (mainly quartzites, marbles and graphitic mica gneisses) cut by early leucogranitic dykes, medium-K calc-alkaline and alkali-calcic (mainly granitic) plutons, and late medium-K porphyry diorite dykes. This magmatism can be bracketed between 588 Ma and 567 Ma (UPb zircon ages). The best preserved pluton (Tismana, 567 Ma old), displays a composite alkali-calcic (very high-K calc-alkaline) magmatic sequence, ranging from gabbro-diorite to monzogranite, including an ultramafic pod. Ages and geochemical signatures resemble the Saharan late Pan-African granitoids. The existence of Late Precambrian partly juvenile terrains is thus confirmed within the basement of South Carpathians, which renders then a segment of the European Alpine belt that can be successfully compared to the Pan-African Trans-Saharan belt.

Romanian Karst – special zones and caves

Romania is characterized by a great wealth of karst forms. The most important are bound to several regions, and namely: the Apuseni Mts., South Carpathians, Eastern Carpathians, Dobrogea. Most of the caves should be included in the List of protected natural sites, and some of them are of interest as a part of the World Geological Heritage.

Middle Triassic carbonate deposits and calcareous algae from the Sasca zone (Southern Carpathians, Romania)

The Sasca zone situated in the innermost part of the Getic Domain from the South Carpathians comprises mainly Triassic deposits of Scythian-Anisian (?Ladinian) age that can be ascribed to four different members forming the Sasca Formation. Three of the members consist of carbonate deposits. Their study permitted a brief characterization of the main microfacies types, and especially in the Valea Susara Limestone Member the identification of a relatively rich association of foraminifers and calcareous algae. The assemblage withMeandrospira dinarica, Pilammina densa, Oligoporella pilosa andPoncetella hexaster identified in these limestones indicates a Middle Anisian age (Pelsonian-Lowermost Illyrian). Difficulties arise in differentiating between the forms belonging to theOligoporella-Physoporella group for which a taxonomic revision is necessary. The morphologic characteristics of the three varieties ofDiplopora subtilis allow a splitting into different species.Teutloporella peniculiformis Ott, 1963 is regarded as anomen nudum.

Biostratigraphy of the Upper Cretaceous of Romania

This paper is a synthesis of published and new ammonite, inoceramid and planktonic foraminiferal biostratigraphic data obtained by the authors from the Upper Cretaceous rocks of the East and South Carpathians, especially from the Median Dacides tectonic units, as well as the Babadag basin of North Dobrogea, Romania.An integrated biostratigraphical scheme, using the above three fossil groups, is presented for the Cenomanian to Coniacian interval. A few new ammonite zones are established for the Cenomanian to Coniacian in Romania, and in the Turonian to Coniacian several association and inoceramid association zones are identified. The planktonic foraminiferal zones established in Romania contain few zones of the new standard scales proposed for the Tethyan realm. Most zones and subzones have been established in diverse Tethyan regions or in Romania, and two planktonic foraminiferal subzones are introduced in this paper.The first appearances of foraminifers such as Rotalipora cushmani, R. turonica, Dicarinella concavata, D. asymetrica, Contusotruncana fornicata, Globotruncana aegyptiaca, G. falsostuarti and Globotruncanita stuarti as defined in Romania, differ from the standard scale; the level at which Rotalipora sensu lato and Helvetoglobotruncana helvetica disappear is undefined. The association with Inoceramus schloenbachi belongs entirely within the lower Coniacian, and the presence of Barroisiceras haberfellneri, Forresteria petrocoriensis and Maginotruncana tarfayensis indicates the base of the lower Coniacian. The Coniacian succession in the Caugagia-Baia region of North Dobrogea is identified as a possible hypostratotype.Santonian to Maastrichtian strata contain few and poorly studied macrofossils, and a zonation using planktonic foraminifers only is possible.

Cretaceous to Miocene thrusting and wrenching along the central south Carpathians due to a corner effect during collision and orocline formation

Field studies in the Romanian South Carpathians (longitude 22.5° to 24.2°E and latitude 45.2° to 45.6°N) demonstrate (1) Cretaceous top‐to‐NE shearing parallel to the present strike of the thrust system connected with coaxial flattening within the generally northwest dipping foliation, (2) Paleogene ductile‐brittle dextral wrenching, E‐W compression (σ1: 87±15°), and basin formation (Petroşani basin) along the Cerna‐Jiu fault system, (3) large‐scale Miocene dextral wrenching along the northern margin of Moesia (σ1: 143±16°), and (4) probably Pliocene–early Pleistocene N‐S compression (σ1: 205±25°). We discuss the tectonics of the South Carpathians stressing the corner effect of the Moesian foreland promontory during convergence and formation of the Carpathian orocline. Up to the late Early Cretaceous, subduction of oceanic crust was active between Europe‐Moesia on one side and East Carpathia‐Rhodopia on the other side. Collision and intracontinental deformation occurred during the late Early and Late Cretaceous. The pinning of the thrust front at the western tip of Moesia and the foreland recess north of it caused superposition of thrusting and wrenching during collision and lateral translation, tangential stretching during orocline formation, and spreading into the recess. Further convergence during the early Tertiary resulted in dislocation of the previously welded East Carpathian‐Rhodopian and Moesian fragments along the Cerna‐Jiu fault system and the further northeast translation of the western segment. The intramontane Petroşani basin opened as a northeasterly propagating, transient pull‐apart structure along the Cerna‐Jiu fault system, which acquired a curved, northwesterly convex, transtensional trace due to the shape of the Moesian promontory. Tightening of the Carpathian orocline and/or rearrangement of the microplate geometry during the formation of the Pannonian basin system led to large‐scale dextral wrenching along the northern margin of Moesia. Pliocene N‐S compression reflects final shortening in the Carpathian system before ongoing convergence between Europe and Africa was transferred to the Mediterranean. Rotation of material lines around the Moesian corner is corroborated by paleomagnetic studies.

Tectonic implications of paleomagnetism in Upper Cretaceous deposits in the Haţeg and Rusca Montanā basins (South Carpathians, Romania)

Previous paleomagnetic studies of Upper Cretaceous deposits in the Haţeg Basin (26 sites) and Rusca Montanā Basin (four sites) concluded that only a few of these sites contained useful paleomagnetic information. For this reason, we utilized only data from six sites in Haţeg Basin (45.5°N, 22.8°E) and two sites in Rusca Montanā Basin (45.5°N, 22.4°E) for further analysis. After AF demagnetization, we identified the primary characteristic remnant magnetizations, which yielded a mean direction of D = 76.9°, I=32.9° and a mean pole of φ = 21.8°N, λ = 109.0°E, A 95= 14.2°. A comparison with the paleomagnetic results obtained from rocks of similar age from stable Africa and Europe shows that to reach their present-day position the studied areas moved to the north and rotated to the east. These results are consistent with the other paleomagnetic data in the Upper Cretaceous magmatic belt of Romania.

Considerations on the Variscides of Romania

From the proposed analysis of two geotraverses, Moesian Platform – South Carpathians and East European Platform – East Carpathians – Apuseni Mountains, it seems that the south-eastern boundary of the Variscan orogen coincided with the present south-eastern boundary of the Alpine orogen. A corollary of this fact could be that the Palaeozoic basement of the Carpathian foreland played the same role of foreland at the time of the Variscan orogeny. Herefrom, the polarity of the Variscides on which the Carpathians are built may be inferred. The mafic initial tension magmatism of the Variscan orogeny was manifested from the Silurian up to the Early Carboniferous in the present territory of the Carpathian orogen. This magmatism became bimodal in the Early Carboniferous. An exclusively acid character of this Early Carboniferous magmatism occur only in the Northern Poiana Ruscă and in the Rapolt massif. In the relative hinterland of the Variscides underlying the Carpathian orogen, an internal zone of carbonatic-platform formations of Devonian and Carboniferous age can bе outline.

The paleomagnetism of the Upper Cretaceous magmatic rocks in the Banat area of South Carpathians: tectonic implications

Forty-four sites were sampled in Upper Cretaceous magmatic rocks in the western part of the Southern Carpathians (Banat area) for a paleomagnetic study. After detailed AF demagnetization, only 10 sites yielded primary remanent magnetizations, the directions of which are similar to those identified in Senonian magmatic rocks from the Apuseni Mountains and the Haţeg and Rusca Montană Basins. The mean paleomagnetic pole for these three areas is compared with those from coeval formations of stable Europe and stable Africa. This comparison shows a large clockwise rotation, both with respect to Africa and Europe, and a northward transport to reach their present-day position during the Tertiary. The relations with adjacent zones of the Tethys mobile belt are also discussed.

Birth, life and death of the Pannonian Lake

The Miocene-Pliocene Pannonian Lake formed in an extensional basin system behind the compressional arc of the Carpathians. Its size and depth were comparable to those of the Caspian Sea. Subsidence began in Middle Miocene times, forming deep, pelagic basins, separated by reef-bearing ridges. Clastic influx filled the marginal basins during Middle Miocene time. Prograding deltas dissected the lake and completed the infilling of the basin system by the end of the Pliocene. Basin plain, prodelta, delta front, delta plain, beach, fluviatile, and marsh environments can be recognized. Terminal Miocene uplift of the Carpathians isolated the Pannonian region from the rest of Paratethys. The subsequent decrease of salinity resulted in the evolution of an endemic, freshwater mollusc fauna. Rich nutrient influx from rivers supported high organic productivity (dinoflagellates, diatoms, nannoplankton, foraminifers, ostracods, etc.), yielding organic-rich sediments. Preservation of organic matter was helped by a stratified water column and oxygen deficient bottom conditions. Deep burial, continuing subsidence, and high geothermal flux due to an extremely thin crust, led to the formation of commercially exploitable oil and gas accumulations. Shallow lacustrine zones of basin margins provided suitable environments for a rich Congeria-Melanopsis mollusc fauna. Wave action on beaches produced commercially exploitable pure quartz sand deposits. Taxodium and Alnus forests flourished around the lake producing enormous lignite deposits. Besides a rich land snail and mammal fauna, prehominids lived in the forests. There was a warm, temperate climate, with probably frostfree winters. Basaltic volcanoes overlooked the landscape, and maars hosted minor lakes with rich algal flora forming oil shale. The catchment area included most of the Carpathians and parts of the Apls and Dinarides. The positive water balance resulted in a supposed overflow in the southern margin, supplying exotic fauna to the South Carpathian and Dacian basins of the Eastern Paratethys. The Pannonian Lake was completely filled by the end of Pliocene. Recent lakes in the Carpathian Basin are not descendants of it.

A model of the lithosphere thickness in the region of the Carpathians

Directionally independent average P residuals computed for waves of teleseismic events arriving under various azimuths and incidence angles provided the basis for estimating the lithosphere thickness beneath the Carpathians and their surroundings. A thin lithosphere (60–80 km) was determined for the Pannonian Basin and the Transylvanian Basin, the thickest lithosphere(about 180 km) beneath the South Carpathians at the contact with the Moesian Platform. In other parts of the Carpathian belt the lithosphere thickens beneath the outer parts towards the SW margin of the East-European and the Moldavian Platforms. The lithosphere thicknesses derived from P residuals correlate well with the magnetotelluric determinations of a layer of increased electrical conductivity in the upper mantle.

Origin of structural arcs of the Carpathian-Balkan region

The Late Cretaceous reconstruction shows that the inner zones of the West, East, and South Carpathians were adjacent to the Dinarides and Hellenides at that time, forming together with them a linear fold system with bilateral vergence. This fold system had a northwest strike. In Paleogene-early Miocene times the general deformation of the given part of the Alpine belt took place. It was caused by rotation of its Asia Minor-Balkan part relative to the more northern part of the belt. This rotation (30°–40° counter-clockwise) was accompanied by a shortening of the considered segment of the Alpine belt by 30%. Hence exfoliation of the Carpathian-Pontide and Dinaric-Tauride branches of the Alpine belt from each other, and their disharmonious plastic deformation, resulted in the formation of the Aegean and Tauride structural arcs and the Carpathian structural loop. During formation of the Carpathian loop, the Gemeric-Tatric tectonic block moved northwards along the Penninic oceanic substratum and rotated over 90° counter-clockwise relative to the Eastern Alps.

Endemische Phytoassoziationen aus den Rumänischen Karpaten

The importance of endemic species for plant communities in the Roumanian Carpathians Mts. has been studied and discussed. Associations of the classAsplenietea trichomanis endemic in the South Carpathians were surveyed; they were classified into some endemic alliances (Gypsophilion petraeae, Micromerion pulegii, andSilenion lerchenfeldianae). Their locus classicus, nomenclatoric type and present distribution were also given.

Horizontal inhomogeneities in the upper mantle of the carpathians and caucasus

The travel-times of waves coming from distant earthquakes, recorded by seismological stations in the Carpathians and the Caucasus were used to construct a model of horizontal inhomogeneities in the upper layer of the mantle in these regions. In comparison with the adjoining platform, the East Carpathians are characterized by higher velocity, the South Carpathians and the Carpathian foredeep by lower velocity, while the West Carpathians have a velocity similar to that of the platform. The Vrinci earthquakes originate in the high-velocity block of the East Carpathians, at its boundary with the low-velocity block of the South Carpathians. The Caucasian territory can be divided into several different mantle blocks. The western part of the Great Caucasus has a higher velocity. A submeridional belt of low velocities, extending west of the line Piatigorsk—Tiflis, has been determined; the belt passes through the Stavropol part of the Great Caucasus, the Transcaucasian central massif and part of the Little Caucasus. More to the east there extends a parallel belt of greater velocities, which also intersects a series of different structures. In the East Caucasus, a low-velocity block has been established in the Caucasian foredeep and the Great Caucasus regions; the boundary between this block and a high-velocity block lying west of it passes through the Caspian Sea. The mantle earthquakes of 1935 occurring NE of Derbent seem to be connected with this boundary. The low-velocity region of the mantle also exists in the Caspian Sea, in the vicinity of the Apsheron Peninsula. A relationship between the determined velocity variations and other geophysical fields has been discussed; some known gravity anomalies in the Caucasus, interpreted as being connected with the earth's crust, are believed to be due to the vertical inhomogeneities of density in the upper mantle.

Plate Tectonics History of Romania

Similarities in lithology and age suggest that the Moesian and Moldavian platforms were united until late Precambrian tine when an independent geological evolution began in parts of Romania and lasted through Paleozoic time. In Middle Triassic time, mafic rocks appeared in the East Carpathians and Dobrogea as part of a wide belt, caused by crustal distension, from the West Carpathians to the Caucasus. Plate separation led to the development of the Siret Ocean between Pannonia and Moldavia. Jurassic sedimentation started as a shallow-water, transgressive facies except in spreading centers, such as the Siret Ocean and the proto-Apuseni area, which was then part of the Dinarides and where ophiolites with interlayered chert and radiolarite formed. By Early Cretaceous time, movement sense changed and the microplates were translated toward the stable craton. The Apuseni ophiolites were obducted onto continental crust. Convergent plate boundaries, with flysch, nappe structures, and silicic volcanism, developed between Moesia-Pannonia and the Tethys-Dinaric Oceans and between Pannonia and the Siret Ocean. In Paleocene time, a belt of calc-alkalic rocks (banatites) developed in western Romania and the Balkan Mountains as a result of plate convergence of Rhodope and Moesia as the last of Tethys was subducted. This was followed by a continental collision of Moesia and Pannonia and the uplift of the South Carpathians. Neogene volcanism and molasse developed as end stages of plate subduction and collision. Modern earthquake activity of the Vrancea Mountains and high heat flow in Transylvania suggest that subduction is still going on around the great Carpathian arch.

Study of some allanites and monazites from the South Carpathians (Romania)

Allanites and monazites from different rocks of the South Carpathians (Romania) are described, and 17 analyses are presented. The genetic relations are discussed.

Some aeropalynological remarks and conclusions on the South Carpathian Mountains (Rumania)

Two methods of research are described: 1. ( 1) Spore and pollen analysis at every hundred meters of the moss patches from the beech to the alpine zones (900–2,484 m altitude). At each level the actual structure of the vegetation has been established. 2. ( 2) Daily aeropalynological trapping of pollen in the alpine and subalpine zones between March 29 and August 21, 1965. In the first case, as long as the samples were collected within the forest, the pollen spectra were found to be in conformity with the surrounding vegetation. However, in the alpine zone pollen from lower zones becomes frequent, depending on the prevailing aerial currents in the studied mountain massif. In the second case, the following phenomena were established: periodicity in pollen productivity; reflotation owing to air turbulence; the action of southwesterly and southeasterly winds, which carried some alien pollen species before the local flowering period, and the action of northwesterly winds carrying generally the same pollen after the local flowering period. The importance of the findings for the understanding of pollen spectra from peat sediments is discussed.

Palynological investigations in the subalpine and alpine zones of the South Carpathian mountains (Rumania)

Palynological and vegetational analyses are given for four peat bogs situated in the subalpine and alpine zones of the Retezat Mountains (South Carpathian Mountains), Rumania. The results reflect the vegetational history of both the bogs and the surrounding forests or alpine communities. Five successive forest periods have been recognized, covering the forest history from the Finiglacial up to the present time. The first three periods were not represented in previously published pollen diagrams of the subalpine and alpine zones of the Rumanian mountains. The sediment containing the pollen spectra of the first forest period—the Finiglacial pine forest—was deposited by snow and glaciers which covered the Retezat Mountains at that time. During the disappearance of the glaciers the pollen became deposited at the bottoms of lakes occupying the ice-carved basins.