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Budapest, Hungary

Novak D.,ELTE Altalanos es Alkalmazott Foldtani Tanszek | Koncz D.,ELTE Altalanos es Alkalmazott Foldtani Tanszek | Koncz D.,Schlumberger | Horvath A.,Olaj es Gazkutato Kft | And 2 more authors.
Foldtani Kozlony | Year: 2010

A curved erosional surface with a radius of 1.5 km and a width of more than 600 metres can be identified on the ultra-high resolution seismic sections acquired on Lake Balaton in the vicinity of Fonyód. The corresponding sediments above the surface are 1-2 m thick.The three-dimensional shape, as well as the oblique reflections parallel with the trend of incision reveal the remnant of a meandering channel. This channel fill unit is situated unconformably above the tilted and folded Pannonian strata, and is overlain disconformably by the Holocene mud of Lake Balaton.The channel-fill deposit is younger than the deformation of the Pannonian, and was most likely formed somewhat before the wave activity associated with the development of the lake. Therefore the supposed age of the sedimentary body is Late Pleistocene. The curvature of the meander seems to follow the Fonyód Hill on the shore of Lake Balaton, suggesting that the topography and the lithology of the hill determined the course of the Pleistocene river. Moreover, this meandering channel corresponds in terms of size, location and curvature with meanders situated outside the study area, below the peat of the Nagyberek, as mapped by MIKE (1976) from a series of densely-spaced shallow cores obtained near Fonyód. MIKE regarded these fluvial sediments as remnants of the "early Pleistocene Danube" which used to flow across this part of the country, although recent palaeohydrographic concepts dispute this idea. Nevertheless, a river of significantly high discharge must have left these channel belt deposits as it crossed the valley south of the Balaton Highland, routing towards the subsiding Danube Valley during the Late Pleistocene.

This study looks at the locality of Ceglédbercel and, using a process of detailed mapping and systematical sampling, describes a 700m-long cut of the nearby road highway 4. The aim of this research was to obtain information about the loess and other overlying sediments on the SW slope of the Kálvin Hill (191.5 m). More precisely, the aim was to examine the mineralogy, the grain-size and distribution of loess particles, the pollen and gastropoda content, the 14C age and finally, marks indicating the brittle deformation of sediments. The observations focused mainly on the loess-type deposits. The three outcropping, slightly clayey loess levels (l1, l2 and l3) were separated by two buried, partly eroded palaeosoil levels (t1 and t2). The grain-size distribution of loess levels l1 and l3 demonstrated their aeolian character, while l2 level illustrated the character of the mixed (aeolian-aquatic) sedimentation. By studying the variation coefficients of the grainsize distribution (as mean diameter Mz, dispersion σ, skewness Sk, and kurtois KG for several loess levels) it was possible to ascertain that the dust was transported from the east; furthermore, the dust probably originated in barren, frostshattered Oligo-Miocene sediments, including their finest (clayey) grain-size fractions. Thus the ordered lattice of the clay minerals of the loess may be explained by the "inherited" character of these minerals. At the same time, the deposition of the loess seems to have taken place over a long period of time (especially in the case of level l3); it was also apparent that the intensity of the deposition was relatively constant, as was the direction of dust-carrying winds. Given the results of the palaeontological and geochronological data, the evidence suggests that the studied loess column originated approximately 19,780 years ago. Furthermore, it continued to spread over the soil levels of Jászfelso{double acute};szentgyörgy (18,500 years ago) and Mende (19,780 years ago), until the last (W3) cold and dry period of the Pleistocene. The post-glacial ice melting is marked by three coarse sand levels (h1 h2 and h3 while the upper, black soil which covers the non-conforming surface of these sand levels (t3 was formed during the QC phase of the Early Holocene Climatic Optimum. It is important to notice that the neo-tectonic, brittle deformations (i.e. the lime veins, "dry" joints and microfaults) stopped below the Holocene/Pleistocene boundary.

The aim of this study is to examine the effect of the sedimentary genetics of Szo{double acute}reg-1 reservoir on sedimentary textures and petrophisical properties, and to summarize their relationships as revealed by geomathematical examination methods. During the data analysis, the drilling data of wells deepened into the residual gas cap were processed. A detailed genetic description of core samples and the interpretation of sedimentary facies units were followed by the definition of sedimentary facies. The information-gathering with respect to the properties of the pore space was also supported by scanning electron microscopy studies (Mol Plc.). The geostatistical methods used for exploring the data included multivariate statistical analysis (in this case, factor analysis), tests of cumulative frequency distribution, and also the partial correlation method. The Szo{double acute}reg-1 reservoir is a gas-capped oil play within the Algyo{double acute} Structure, lying in the Upper Pannonian Újfalu Formation. It is a part of the largest hydrocarbon accumulation of Hungary settled on a delta plain. Accordingly, four sedimentary facies can easily be distinguished related to the delta sequence: (1) natural levee - distributary channel - channel abandonment transition, (2) prograding crevasse splay - swamp transition, (3) prograding distributary channel - crevasse splay - prograding crevasse splay transition and (4) swamp - distributary channel transition. The vertical and horizontal permeability and porosity data examined in this study were measured on cores as well as carbonate content and grain-size surveys. (Mol Plc.). The investigations concluded that the pore space of sandy sediments forming the Szo{double acute}reg-1 reservoir can be regarded as a primary sedimentary pore space; however, the impacts of secondary pore space play a tributary role, and the reservoir habitat of the rock body can be regarded as a non-negligible factor. The secondary carbonate minerals in the pore space appear to occur at the level of micropores.

Peter T.,ELTE A ltalanos es Torteneti Foldtani Tanszek | Peter T.,Jelenlegi cime Eriksfiord AS | Peter S.,Mol Nyrt | Orsolya S.,ELTE A ltalanos es Torteneti Foldtani Tanszek
Foldtani Kozlony | Year: 2010

During the early stage of its evolution Lake Pannon had been dissected by several islands and peninsulas. One of the largest of these might have been the present Transdanubian Range rimmed by rocky coasts, sands and gravels at about 10 Ma ago (Kálla Gravel). These gravels were partly formed as wave-reworked beach deposits and as Gilbert-type deltaic deposits. Three depositional units were distinguished in the outcrops of the Kálla Gravel in the Tapolca Basin. The uppermost is made up of horizontal strata of well sorted, fine sand and pebbly sand and unconformably overlies the lower ones, which have a steep depositional dip up to 20-30°. The lower two units are mainly made up of open-fabric clast-supported gravel and sandy gravel. The dip of beds is not constant, there are internal low angle differences and downlaps. The two lower facies units are different only regarding their thickness and transport direction. The lowermost unit attains 20 m thickness with southerly dip directions. The overlying unit observed and studied in details in the SE part of the largest quarry is only 2-3 m thick and dips towards the NE. Both the large and small steep progradational surfaces were interpreted as foresets, while horizontal surfaces as topsets of a shallow-water Gilbert-type delta. In the largest outcrop - an active gravel pit - of the deltaic deposits ground penetrating radar (GPR) measurements were carried out in order to reveal the architecture of the deltaic body. Data were gained from three pseudo-threedimensional grids of about 30×30 m with 2 m spacing of parallel sections. Only basic processing steps were applied: bandpass filtering, true amplitude recovery and static correction. For comparison and control of GPR images geological cross-sections, logs and photographs taken during the last eight years were also used. Based on reflection terminations, amplitude and continuity variations three major units were distinguished on the radar sections as well. The lowermost unit is characterised by strong, steep, oblique reflections, which can be seen even at least to a depth of 12 m. 3-D mapping of these surfaces demonstrated fairly straight and uniform dip planes to the S, SE in harmony with the dip of the lowermost large foreset unit. In the south-eastern measure grid it is cut by a high amplitude low angle reflection, which is a downlap surface of oppositely dipping reflections up to a height of about 3 m. 3-D mapping revealed a set of small curved surfaces extending to a few tens of metres only, indicating migration towards the N-NE. Above both set of dipping reflections horizontal reflections are detected, corresponding to the topmost horizontal strata of the delta. The GPR study demonstrated that the main transport was towards the S, SE having only subtle differences in transport direction, however, still enough to show reflection terminations between the separate lobes. The low angle erosion of the previously deposited lobes may point to a lake-level drop of a few metres amplitude. The resulted accommodation was filled by minor lobes quickly migrating aside (NE) by the major one. The overlying topsets indicate a continued gradual rise of lake-level.

Csaszar G.,Eotvos Lorand University | Szinger B.,Mol Nyrt | Piros O.,Hungarian Geological and Geophysical Institute
Geologica Carpathica | Year: 2013

The Upper Triassic-Lower Cretaceous successions of the Transdanubian part of the Mecsek and Villány- Bihor Zones of the Tisza Unit have been studied from the lithological, lithostratigraphical, sedimentological, microfossil and microfacies points of view in order to correlate and interpret the significant differences between them and to draw a conclusion about their geological and paleogeographical history. After an overview of the paleogeographical reconstructions of the broader area, the succession of the Mecsek and Villány-Bihor Zones and the debated Máriaké ménd-Bár Range are introduced. Until the end of the Middle Triassic the study area acted as an entity. The first fundamental difference between the two zones can be recognized in the Late Triassic when marine carbonates were replaced by thick fluvial siliciclastics in the Mecsek Zone, while it is represented only by small, local lenses with a few and thin dolostone intercalations in the Villány Zone. The Mecsek Zone is bordered southward by one of the large listric faults to the north of which very thick siliciclastics developed in the Early to Middle Jurassic, whereas it is highly lacunose in the larger western part of the Villány-Bihor Zone. The break at the base is subaerial, higher in the succession it is shallow submarine. The sediment is silty, occasionally sandy crinoidal limestone of late Early Jurassic or even Middle Jurassic in age. The Upper Jurassic in the Mecsek Zone is composed of deep-water cherty limestone while in the Villány Zone it became a thick, shallowing pelagic limestone with reworked patch reef fragments. It is clear evidence that the Mecsek Zone had a thinned continental crust thanks to the nearby rift zone while in the Villány Zone the crust remained thick. The actualized version of the Plašienka's paleogeographical model (Plašienka 2000) is introduced.

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