Rôle de la déformation métamorphique dans la cristallinité du graphite : l'exemple des schistes graphiteux de la vallée de la Lotru (Carpathes,Roumanie)Role of metamorphic strain in the cristallinity of graphite: the example of the graphitic schists from the Lotru valley (Carpathians,Romania)

The study of the schists from Lotru valley (Carpathians mountains, Romania) shows the role of stress in graphite crystallinity. The carbonaceous material was separated and studied by X-ray diffraction and Raman microspectrometry. There exists a clear contrast between the crystallization degree of graphite found in the quartz–muscovite schists (good) and that found in the quartzites (poor). This observation is in conformity with a clear differentiation of fabric. The graphite suffered an anisotropic deformation in the graphitic schists, whereas it was protected from deformation by quartz in the quartzites. In this last case, the development of graphite from the organic material took place with a volume decrease, protected by the surrounding quartz. To cite this article: S.-C. Barzoi, B. Guy, C. R. Geoscience 334 (2002) 89–95.     

Tectonic configuration of the Apuseni–Banat—Timok–Srednogorie belt, Balkans-South Carpathians, constrained by high precision Re–Os molybdenite ages

The Apuseni–Banat–Timok–Srednogorie magmatic–metallogenic belt (ABTS belt), forms a substantial metallogenic province in the Balkan-South Carpathian system in southeastern Europe. The belt hosts porphyry, skarn, and epithermal deposits mined since pre-Roman times. Generally, the deposits, prospects, and occurrences within the belt are linked to magmatic centers of calc-alkaline affinity. Fifty-one rhenium-osmium (Re–Os) ages and Re concentration data for molybdenites define systematic geochronologic trends and constrain the geochemical-metallogenic evolution of the belt in space and time. From these data and additional existing geologic-geochemical data, a general tectonic history for the belt is proposed. Mineralization ages in Apuseni-Banat, Timok, and Panagyurishte (the central district of the larger E–W Srednogorie Zone) range from 72–83, 81–88, and 87–92 Ma, respectively, and clearly document increasing age from the northwestern districts to the southeastern districts. Further, Re–Os ages suggest rapidly migrating pulses of Late Cretaceous magmatic–hydrothermal activity with construction of deposits in ~1 m.y., districts in ~10 m.y., and the entire 1,500 km belt in ~20 m.y. Ages in both Timok and Panagyurishte show systematic younging, while deposit ages in Banat and Apuseni are less systematic reflecting a restricted evolution of the tectonic system. Systematic differences are also observed for molybdenite Re concentrations on the belt scale. Re concentrations generally range from hundreds to thousands of parts per million, typical of subduction-related Cu–Au–Mo–(PGE) porphyry systems associated with the generation of juvenile crust. The geochronologic and geochemical trends are compatible with proposed steepening of subducting oceanic slab and relaxation of upper continental plate compression. Resulting influx of sub-continental mantle lithosphere (SCML) and asthenosphere provide a fertile metal source and heat, while the subducting slab contributes connate and mineral dehydration fluids, which facilitate partial melting and metal leaching of SCML and asthenosphere. Cu–Au–Mo–(PGE) porphyry deposits may develop where melts are trapped at shallow crustal levels, often with associated volcanism and epithermal-style deposits (South Banat, Timok, and Panagyurishte). Mo–Fe–Pb–Zn skarn deposits may develop where felsic melts are trapped adjacent to Mesozoic limestones at moderate crustal levels (North Banat and Apuseni). Systematic spatial variations in deposit style, commodity enrichment, Re–Os ages, and Re concentrations support specific tectonic processes that led to ore formation. In a post-collisional setting, subduction of Vardar oceanic crust may have stalled, causing slab steepening and rollback. The slab rollback relaxes compression, facilitating and enhancing orogenic collapse of previously thickened Balkan-South Carpathian crust. The progression of coupled rollback-orogenic collapse is evidenced by the width of Late Cretaceous extensional basins and northward younging of Re–Os ages, from Panagyurishte (~60 km; 92–87 Ma) to Timok (~20 km; 88–81 Ma) to Apuseni-Banat (~5 km; 83–72 Ma). Generation of a well-endowed mineral belt, such as the ABTS, requires a temporally and spatially restricted window of magmatic–hydrothermal activity. This window is quickly opened as upper plate compression relaxes, thereby inducing melt generation and ingress of melt to higher crustal levels. The window is just as quickly closed as upper plate compression is reinstated. The transient tectonic state responsible for economic mineralization in the ABTS belt may be a paleo-analogue to transient intervals in the present subduction tectonics of SE Asia where much mineral wealth has been created in the last few million years.     

Putting together the pieces of the puzzle: Traces of New Zealand in international school geography textbooks

How does a fairly remote space (the islands of New Zealand) contribute to the development of geographical literacy in the geography textbooks of post‐socialist (Romania), Western (Germany) and post‐colonial (Mexico) countries? A four‐step analysis of three textbooks of international selection revealed different regionalisation cultures combined with traditional and recently implemented educational paradigms of geography education and led to a similar result. Despite the many ways in which New Zealand's geographical distinctiveness could be used to enhance geographical literacy, there are few operationalisations of educational targets that might contribute to sustainable long‐term learning. Further, these results also offer a possible explanation for the absence of the ‘southern lands’ on students' cognitive maps of the world.     

Crustal constraints on the origin of mantle seismicity in the Vrancea Zone, Romania: The case for active continental lithospheric delamination

The Vrancea zone of Romania constitutes one of the most active seismic zones in Europe, where intermediate-depth (70–200 km) earthquakes of magnitude in excess of M_w = 7.0 occur with relative frequency in a geographically restricted area within the 110° bend region of the southeastern Carpathian orogen. Geologically, the Vrancea zone is characterized by (a) a laterally restricted, steeply NW-dipping seismogenic volume (30 × 70 × 200 km), situated beneath (b) thickened continental crust within the highly arcuate bend region of the Carpathian orocline, and (c) miscorrelation of hypocenters with the position of known or inferred suture zones in the Carpathian orogenic system. Geologic data from petroleum exploration in the Eastern Carpathians, published palinspastic reconstructions, and reprocessing of industry seismic data from the Carpathian foreland indicate that (1) crust of continental affinity extends significantly westward beneath the external thrust nappes (Sub-Carpathian, Marginal Folds, and Tarcau) of the Eastern Carpathians, (2) Cretaceous to Miocene strata of continental affinity can be reconstructed westward to a position now occupied by the Transylvanian basin, and (3) geologic structure in the Carpathian foreland (including the Moho) is sub-horizontal directly to the east and above the Vrancea seismogenic zone. Taken together, these geologic relationships imply that the Vrancea zone occupies a region overlain by continental crust and upper mantle, and does not appear to originate from a subducted oceanic slab along the length of the Carpathian orogen. Accordingly, the Vrancea zone appears to potentially be an important place to establish evidence for active lithospheric delamination.     

Isotopic climate record in a Holocene stalagmite from Ursilor Cave (Romania)

The PU‐2 stalagmite from Ursilor Cave provides the first dated Romanian isotope record for the Holocene. The overall growth rate of the speleothem was 3.5 cm kyr^?1, corresponding to a temporal resolution of 142 y between each isotope analysis. The ‘Hendy’ tests indicate that isotopic equilibrium conditions occurred during the formation of PU‐2, and hence that it is suitable for palaeoclimatic studies. The relationship between δ¹⁸O and temperature was found to be positive. This can be interpreted either as rain‐out with distance from the west‐northwest ocean source of evaporation or shifts in air mass source with changing North Atlantic Oscillation indices. Applying five U–Th thermal ionisation mass spectrometric (TIMS) dates to a 17.5 cm isotope profile (δ¹⁸O and δ¹³C) along the stalagmite growth axis enabled a tentative interpretation of the palaeoclimate signal over the past 7.1 kyr. Spikes of depleted isotopic δ¹⁸O values are centred near ca. 7, ca. 5.2 and ca. 4 ka, reflecting cool conditions. The record shows two warm intervals between ca. 3.8 and ca. 3.2 ka (the maximum warmth) and from ca. 2 to ca. 1.4 ka, when the δ¹⁸O values were less negative than present. The ‘Holocene Climate Optimum’ spanning the time interval from ca. 6.8 to ca. 4.4 ka is not well expressed in the PU‐2 stalagmite. Individual spikes of lighter δ¹³C are interpreted as indicative of periods of heavy rainfall, at ca. 7, ca. 5.5, and ca. 3.5 ka. The overall trend to lighter δ¹³C in the PU‐2 stalagmite may reflect a gradual decrease in water–rock interaction. The results demonstrate that the effect of North Atlantic oceanic changes extended to the investigated area. Nevertheless, some differences in temporal correlation and intensity of stable isotopic response to these climatic events have been found, but the exact nature of these differences and the underlying mechanism is yet to be determined. Copyright © 2002 John Wiley & Sons, Ltd.     

Late Glacial and Holocene vegetation history in the southern part of Transylvania (Romania): pollen analysis of two sequences from Avrig

We present here the results of pollen analysis of two sequences of about 8.06 m and 11.90 m length, originating from two adjacent peat bogs in the southern part of Transylvania province, Romania (155 and 122 pollen spectra). The vegetation record, which is supported by 17 ¹⁴C dates, begins in the Late Glacial interstadial when forest recolonisation began with the development of Pinus, without a pioneer Betula phase. Picea began to expand from regional refuges. After a well‐defined Younger Dryas, the Holocene opens with the expansion of Betula, Ulmus and Picea, followed, at about 10 400 cal. yr BP, by Fraxinus, Quercus and Tilia. The Corylus optimum is correlated with the Atlantic chronozone (after 8600 cal. yr BP). The local establishment of Carpinus occurred at about 6500 cal. yr BP, with a maximum at about 5700 cal. yr BP. Fagus pollen is regularly recorded after 8200 cal. yr BP. This taxon became dominant at about 3700 cal. yr BP. The first indications of human activities appear at around 7200 cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd.     

Macroseismic intensity attenuation for crustal sources on romanian territory and adjacent areas

The macroseismic intensity attenuation (m.i.a.) laws for the main seismic provinces with crustal foci of the Romanian territory and adjacent areas were established. The input data consist of MSK-64 intensities of 18 earthquakes with epicentral/maximum intensity in the range V to X degrees (MSK scale), whose isoseismal maps were available.The attenuation was analyzed as a function of distance and azimuth and from the three main attenuation formulas (logarithmic, exponential, and power-law) (the last one was preferred, as it best fits the observed data) and, consequently, were used for each seismogenic region. The bulk of derived equations is intended to be further used in the assessment of the seismic hazards of Romania.     

The East Side Story – The Transylvanian latest Cretaceous continental vertebrate record and its implications for understanding Cretaceous–Paleogene boundary events

The latest Cretaceous continental vertebrate faunas of the wider Transylvanian area figured prominently in discussions concerning the Cretaceous–Paleogene Boundary (K-Pg) events when they were first described by Nopcsa between 1897 and 1929, because they were assumed to be late Maastrichtian in age. Subsequently their age was reconsidered as early Maastrichtian, and were thus regarded of lesser importance in understanding the K-Pg boundary events in Europe and worldwide. Moreover, Transylvanian continental vertebrate assemblages (the so-called ‘Haţeg Island’ faunas) were often lumped together as a temporally restricted assemblage with a homogenous taxonomic composition. Recent fossil discoveries and more precise dating techniques have considerably expanded knowledge of the Transylvanian vertebrate assemblages, their ages, and their evolution. A synthesis of the available stratigraphic data allows development of the first comprehensive chronostratigraphic framework of the latest Cretaceous Transylvanian vertebrates. According to these new data, expansion of continental habitats and emergence of their vertebrate faunas started locally during the latter part of the late Campanian, and these faunas continued up to the second half of the Maastrichtian. During this time, long-term faunal stasis appears to have characterized the Transylvanian vertebrate assemblages, which is different from the striking turnovers recorded in western Europe during the same time interval. This suggests that there was no single ‘Europe-wide’ pattern of latest Cretaceous continental vertebrate evolution. Together, the available data shows that dinosaurs and other vertebrates were relatively abundant and diverse until at least ca. 1 million years before the K-Pg boundary, and is therefore consistent with the hypothesis of a sudden extinction, although this must be tested with future discoveries and better age constraints and correlations.     

Crescentiella morronensis (Crescenti) (incertae sedis) dominated microencruster association in Lower Cretaceous (lower Aptian) limestones from the Rarău Massif (Eastern Carpathians,Romania)

Analysis of eight outcrops from Rarău Massif (Eastern Carpathians, Romania) revealed a rich assemblage of encrusting organisms mostly of problematic biological affiliation within platform-margin facies – Crescentiella morronensis, Radiomura cautica, Koskinobullina socialis, Pseudorothpletzella schmidi, Lithocodium aggregatum and bacinellid structures, encrusting calcified sponges (Calcistella jachenhausenensis, Neuropora lusitanica) and foraminifera (Coscinophragma cribrosa). Orbitolinids, calcareous green algae and rudists assign an early Aptian age (Bedoulian) for the studied limestones. In terms of species variety, abundance and structural microfabrics the studied microencruster association show similarity with the Upper Jurassic communities from reef and peri-reefal sedimentary settings. Comparisons with such assemblages are emphasized here. The presence of the sporolithacean and peyssonneliacean red algae (Sporolithon rude and Polystrata alba) contributes also to the construction of superimposed crusts. Even if the known stratigraphic range of the microencrusters is not strictly limited to the late Jurassic, reports of comparable associations in Urgonian-type facies is poorly documented. Therefore, it exemplifies the resistance and flourishing events of many encrusters throughout the Mesozoic.     

Simion Mehedinţi's Contribution to Modern Romanian Geography

Armed with a scholarship to find an answer to the question “What is geography?” Simion Mehedin?i's studies took him to continental Europe's three main centers of geographic thought: Paris, Berlin, and Leipzig. We explore how his innovative ideas flourished, especially in Leipzig under Ratzel. The first Romanian geographer, Mehedin?i, must be credited with having defined geography as a science of mutual relationships between geospheres. This thinking reached its pinnacle in two complex books, Terra and Ethnos, the contents of which we synthetically explore. We also trace the unfavorable historical and geopolitical conditions that led to this pioneering work being little recognized worldwide.