MORPHOSTRUCTURE PATTERNS IN SATELLITE MULTISPECTRAL LANDSAT TM IMAGES
Abstract: The possibility of tectonic observations using multispectral remote sensing data is based mainly on morphostructures, which could lead directly to the structural interpretation of the area. This work aims to contribute to the creation of a morphostructure-code with a corresponding key-legend, in order to facilitate the acquisition of tectonic information by users, who do not specialize in remote sensing. The studied area covers a great part of NW Greece (Epirus Prefecture). During the summer and autumn of 1996, this region was affected by strong and disastrous earthquakes (up to 5.6 R). Data from Landsat TM have been selected and processed creating a false colour composite image and then analyzed and interpreted in order to detect the tectonic features.
POST-OROGENIC UPLIFT-INDUCED EXTENSION: A KINEMATIC MODEL FOR THE PLIOCENE TO RECENT TECTONIC EVOLUTION OF THE EASTERN CARPATHIANS (ROMANIA)
Abstract: We propose a new tectonic model for the Pliocene to recent tectonic evolution of the Eastern Carpathians, especially for the formation of the Brasov-Gheorghieni basin system in the hinterland and for the shortening in the foreland during the "Valachian Phase" of deformation. Kinematic analysis of fault-slip data indicates the formation of the Brasov-Gheorghieni basins due to NW-SE oriented extension, but with joints displaying varying orientations suggesting regional uplift as the source of extension. The trend of regional folds in the foreland indicates NW-SE oriented shortening. The sedimentation rate of coarse material in the foreland basin reflects a high post-Miocene rate of uplift, very accelerated during Pliocene-Quaternary time. The seismological data show active offset along two strike-slip faults (the Trotus and Intramoesian faults), which border both the region of extension in the hinterland and the area of shortening in the foreland. A third strike-slip fault (the Sinaia Fault) is constrained south of the Brasov-Gheorghieni basins by kinematic and seismological data. All these observations have been combined in the following new tectonic model: succeeding the continental collision in Miocene, a very high rate of uplift occurred in the Eastern Carpathians during Pliocene-Quaternary time. The uplift induced gravitational mass transfer from the uplifted area, which had a high potential energy, towards the surrounding areas with low potential energy. The mass transfer took place through the southeastward motion of a crustal block between the Trotus sinistral and the Sinaia dextral strike-slip faults above an older, reactivated detachment horizon of the Eastern Carpathians fold-and-thrust belt. The motion of this crustal block resulted in extension in the hinterland and the formation of the Brasov-Gheorghieni basin system; the extension was accommodated by shortening in the foreland.
LITHOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENT OF LOWER–MIDDLE JURASSIC CRINOIDAL LIMESTONE FORMATIONS OF THE VYSOKA NAPPE UNIT (MALE KARPATY MTS., WESTERN CARPATHIANS)
Abstract: The Lower-Middle Jurassic sequence of the Vysoka Unit in the Male Karpaty Mts. (Western Carpathians, Slovakia) comprises a complex of crinoidal limestones. The paper suggests newly dividing this unit into four formations: Trlenska Fm., Vyvrat Fm., Pristodolok Fm. and Vils Fm., all of which are described in detail. Two of them, the Vyvrat and the Pristodolok Fms., are defined as new formal lithostratigraphic units. A connection is supposed between rhythmical facies changes in these sediments and relative sea level fluctuation. Two significant regressions are recognisable in a generally shallowing upward sequence with an uncertain number of cycles of lower order between them. The influence of eustatic and regional tectonic activity control on relative sea level changes has been not distinguished. The curve of sea level changes suggested by sequence stratigraphic analysis is comparable to the curve published by Haq et al. (1988). Lateral facies changes have been studied across the Vysoka Nappe Unit. The Lower-Middle Jurassic crinoidal complex is a part of a slope apron rimming the toe-of-slope of a carbonate plateau which probably originated due to tectonic collapse of the large Triassic carbonate platform during the early Jurassic. Its proximal development (near to apex) was recognized at the SW and the distal development at the NE edge of the Vysoka Unit. Sedimentation of the crinoidal limestones was terminated by an abrupt rise of the relative sea level and followed by deposition of nodular limestone formations.
NORTH DINARIDIC LATE CRETACEOUS-PALEOGENE SUBDUCTION-RELATED TECTONOSTRATIGRAPHIC UNITS OF THE SOUTHERN TISIA, CROATIA
Abstract: In order to evaluate the structural position of Mesozoic formations underlying the Neogene South Pannonian Basin, a tentative correlation is proposed between (1) the Late Cretaceous-Paleogene subduction-related magmatic, sedimentary and metamorphic units of the North Dinarides and (2) the apparently exotic blocks of the same units found in the subsurface and at the surface within the Pannonian Basin. The formations are as follows: a — Sedimentary Late Cretaceous to Paleogene flysch sequences, at their base interlayered with basalt, alkali-feldspar rhyolite and pyroclastics and intruded by penecontemporaneous A-type granites; b — Very low-, low- and medium-grade regionally metamorphosed sequences which originated from the surrounding Late Cretaceous-Paleogene rocks; c — Synkinematic Eocene A-type and S-type granitoids and d — Underlying tectonized ophiolite melange. Concordant radiometric (71 to 48 Ma) and geological ages were obtained on the rocks of the first three units from both areas. This paper presents diagrams which schematically illustrate and summarize the Late Cretaceous to Miocene evolution of the area adjoining the North Dinarides and South Pannonian Basin. Geological profiles, based on seismic data, are presented. The occurrence of North Dinaridic Late Cretaceous-Paleogene subduction-related exotic fragments found in the South Pannonian Basin can be explained: 1 — by Oligocene uplift of detached fragments of the underthrust North Dinarides in the nascent Drava and Sava depressions, and 2 — by Pliocene strike-slip faulting.
PALEOECOLOGY OF THE LATE MIOCENE MAAR LAKES, PODRECANY BASALT FORMATION, SOUTHERN SLOVAKIA, ON THE BASIS OF SILICEOUS MICROFOSSILS
Abstract: The siliceous microfossils—diatom and chrysophycean stomatocystae—of the diatomite and alginite from two maars (Jelsovec and Pincina) of the Late Miocene Podrecany Basalt Formation in Southern Slovakia have been studied. The ecological analysis of the microfossils studied points to a shallow lake environment with ph = 7–8, salinity of 0.3–0.5 %, temperate climate. The nutrient spectrum from the Jelsovec maar where diatomite was deposited suggest an oscillation of oligotrophic and eutrophic conditions. In Pincina maar where alginite was deposited the eutrophic conditions prevailed. The exellent state of Botryococus braunii soft bodies preservation points to a stratified water column in the lake with anaerobic conditions at the bottom. In the Jelsovec maar organic matter is practically missing. The water column was not stratified, even the bottom water was oxygenated and oligotrophic conditions prevailed.
PHASE RELATIONS IN OLIVINE-ORTHOPYROXENE-CHLORITE-SPINEL-HORNBLENDE METAULTRAMAFICS FROM THE MALA FATRA MTS., WESTERN CARPATHIANS
Abstract: Metaultramafic rocks from the Mala Fatra Mts. (Western Carpathians) preserve mineral assemblages characterized by coexistence of hercynitic spinel, Ca-amphibole (Mg-hornblende), Mg-rich chlorite, olivine (forsterite) and orthopyroxene (enstatite). A large amount of hercynite and Ca-amphibole (up to 30–40 % ) is characteristic. Prograde metamorphism reached P-T conditions close to the equilibrium chlorite = forsterite + enstatite + spinel + H2O and the upper stability of Ca-amphibole which corresponds to the temperature of about 700–800 °C in the model system CMASH. Retrograde reactions lead to the replacement of spinel by secondary chlorite, orthopyroxene by talc and olivine by serpentine. Metaultramafic rocks in the Mala Fatra Mts. reached the conditions of the upper amphibolite facies. They most probably represent the fragments of metaperidotites, attached to the lower continental crust during Variscan tectonometamorphic events.
HYDROTHERMAL ALTERATION OF GRANITOID ROCKS AND GNEISSES IN THE DUBRAVA Sb-Au DEPOSIT, WESTERN CARPATHIANS
Abstract: Three alteration zones are recognized in hydrothermally altered granitoid rocks at the Dubrava Sb-Au deposit, Nizke Tatry Mts., Western Carpathians: the outermost chlorite zone, muscovite zone and the innermost illite-carbonate zone. Chlorite replacing biotite originated at temperature about 320 ± 40 °C (according to Cathelineau 1988) and the frequency distribution of AlIV in chlorite suggests its re-equilibration during later hydrothermal events. The muscovite and illite-carbonate zones are superimposed on the chlorite zone. Muscovite appears to be of both magmatic and hydrothermal origin, as deciphered from its TiO2 content. Hydrothermal muscovite replaces plagioclase and chlorite. In the innermost zone, carbonates and sulphides become abundant, muscovite and feldspars are replaced by illite. Measurements of crystallinity index values of illite gave an estimate of 180–200 °C for the illite-carbonate zone. The altered rocks were enriched in K2O, H2O, CO2, Sb and S and depleted in CaO, MgO, Fe2O3, and Na2O. Minor changes in Al2O3 and SiO2 content are ascribed either to the variations of the composition of the primary magmatic precursor or local redistribution of these elements. Limited data on alteration of amphibole gneisses and migmatites suggest that the main processes were chloritization and illititation; SiO2 and Na2O were removed and K2O added to these rocks.