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In the Bohemian Massif, there are many localities with the occurrence of secondary phosphates bound to the fissures of the host rocks. The type of these rocks partly determines the character of individual phosphate associations. As part of this comprehensive work, based on the author’s PhD thesis, the main host rock types have been classified and selected mineral associations have been studied in detail. This paper is a summary not only of the author’s research, but also of the historical knowledge in the field of secondary fissure phosphates in the Bohemian Massif. The paper concludes with a brief outline of the likely conditions for the formation of fissure phosphates. [ABSTRACT FROM AUTHOR]

This paper presents new structural, anisotropy of magnetic susceptibility (AMS), and petrological data in tandem with existing geochronological data to determine a polyphase Variscan tectonometamorphic event in the southwestern Moldanubian Zone of the Bohemian Massif. The high-grade metamorphic rocks of this Zone underwent the successive tectonometamorphic evolution (from ca. 360 to 310 Ma) that portrays three main geodynamic episodes: (a) The collisional to exhumation episode (ca. 360–335 Ma) recorded by the relict, steeply dipping, and ~ N(NNE) to S(SSW) striking foliation planes (S1) developed at temperatures of 720–754 °C and pressures of ca. 790 MPa (M1) and superimposed flat-lying foliation planes (S2) under temperatures of 674 ± 27 °C and pressures of 680 ± 110 MPa (M2). (b) The late-orogenic ~ N–S oriented shortening (ca. 335–325 Ma) controlled by convergence of a crustal segment derived from the Gondwana continent (newly named as the "Salzburgia Block) and the mostly consolidated Bohemian Massif. These collisional processes resulted in superimposition of the foliation planes (S3) dipping steeply to moderately to the ~ N to ~ NNE(NE), re-heating and metamorphic overprint at temperatures of 770–830 °C and pressures of 450–530 MPa (M3) and syn-tectonic emplacement of the numerous late-orogenic granitoids. (c) Subsequently, the switch in the paleostress regime from ~ N–S shortening to that of late-orogenic ~ ENE–WSW extension (ca. 325–310 Ma) led to the activation of regional right-lateral transtension and exhumation of the deep-seated rocks. Associated re-equilibration proceeded under temperatures of 662–701 °C and pressures of 362–437 MPa (M4 event). In the latter stages of this episode, the synchronous reactivation of the regional ~ NW–SE striking right-lateral shear zones (Pfahl and Danube) and the almost perpendicular ~ NNE(NE)–SSW(SW) striking left-lateral shear zones took place. [ABSTRACT FROM AUTHOR]

The paper contains an analysis of S-velocity distribution in the crust and upper mantle beneath the Bohemian Massif, which is the second biggest Variscan outcrop in Europe. It occupies mainly the west part of Czech Republic and also part of south-west Poland and south-east Germany. We use data from 10 permanent stations set in the region. Some previous papers relate to the same scope but use linear methods to inverse receiver function. Our new approach involves Monte Carlo techniques for inversion procedure, which is more convenient and robust for such a non-linear task. The result of Monte Carlo inversion is compared with the previously achieved one. The obtained Moho depths vary from 29 km in the north-west part of the Bohemian Massif to 38 km in the south and south-east and are consistent with other papers. Some discrepancies occur in the middle and upper crust. [ABSTRACT FROM AUTHOR]

Perpendicular or high-angle relationship of lineations is common in shear zones where synchronous fabric transposition and shearing occur. This paper documents a polyphase early-Variscan structural record exposing the transition from orogenic superstructure to infrastructure along a major detachment shear zone at the western margin of the Teplá–Barrandian domain, Bohemian Massif. On the scale of tens of kilometers this region shows major but continuous reorientation of S2/S3 intersection lineation from its NNE–SSW trends in the superstructure to the ESE–WNW trends in the infrastructure. A simple kinematic numerical model, which allows deformation parameters such as fabric attractor, deformation symmetry, and proportion of simple shear, to be varied, was formulated to explain the rotation of fabrics observed in the field. In line with the results of our kinematic modelling, these rotations are interpreted as a result of progressive transposition of the originally subvertical S2 foliation into the gently SE-dipping S3 marked by stretching at high angle to the incipient S2–S3 intersection. The mineral–fabric relations suggest that the S2 was associated with crustal thickening and is well preserved in the superstructure, while S3 was associated with exhumation of deeper parts of the infrastructure. The kinematic model confirmed the operation of major detachment shear zone and allowed a set of the most probable deformation parameters leading to successful simulation of the fabric geometries to be identified. In addition, the successful model parameters were used to restore the vertical structure of the studied region prior to exhumation on the basis of available pressure–temperature data. We believe that unlike the commonly used balanced cross-section restoration, our restoration technique can be successfully applied in orogen interiors if the mineral–fabric relations are well-constrained and high-quality pressure–temperature estimates exist. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide an overview of Li contents and their trends in pre-Variscan and Variscan granitoids in the Czech part of the Bohemian Massif. All igneous systems with significant Li enrichment are described (Fig. 1). Among other plutons, only some typical examples are selected. A special attention is given to rocks with sufficiently robust data sets on Li contents. Bulk-rock contents of Li in granitoids were assessed within several projects of the Czech Geological Survey (CGS) and the Institute of Geology of the Czech Academy of Sciences (GLÚ) in 1985-2019. Lithium was determined mostly by the AAS method in laboratories of the CGS. Analyses of micas can be divided into three groups according to the methodology: (i) classic wet complete chemical analyses of mica concentrates (from years 1985-90); (ii) a combination of AAS-Li analyses of mica concentrate and determination of other elements using a microprobe in thin sections (mostly from years 1990-2010); and (iii) a combination of Li analyses and trace element analyses using laser-ablation ICP-MS and major elements using a microprobe. The method of laser ablation was performed at Faculty of Sciences, Masaryk University in Brno, microprobe analyses in GLÚ and wet chemical analyses in CGS. Pre-Variscan granitoids in the Bohemian Massif are generally Li-poor (Fig. 2). Relatively highest Li values (0.08 wt.% Li2O + elevated P, B, and Sn) were found in the Blaník-type orthogneiss in the NE part of the Moldanubicum. Lithium is hosted in micas: ca. 0.1-0.6 wt.% Li2O in biotite and 0.2-0.4 wt.% Li2O in muscovite. Among Variscan igneous rocks (Fig. 3), Li is slightly enriched in some two-mica and muscovite granites in the Moldanubicum, and particularly in Li-biotite and zinnwaldite granites in the Krušné Hory - Erzgebirge (Saxothuringicum). Two-mica granites of the Eisgarn type in the South Bohemian pluton in the Moldanubicum contain up to 0.05 wt.% Li2O; small bodies of late muscovite granites near the Czech-Austrian border up to 0.16 wt.% Li2O. Biotite and muscovite from the two-mica granites contain about 0.1-0.5 wt.% Li2O and 0.03-0.14 wt.% Li2O, respectively. Muscovite of the Homolka muscovite granite contains up to 1.0 wt.% Li2O. In the Kreuzstein granite (0.12 wt.% Li2O), situated at Czech-Bavarian border in the NW edge of the Moldanubicum, zinnwaldite is the Li carrier; this makes this granite more similar to evolved Saxothuringian granites. Variscan granites in the Erzgebirge should be divided into two groups. The first group includes strongly peraluminous granites which dominate the western part of the area forming the Smrčiny-Fichtelgebirge, Nejdek-Eibenstock and Slavkovský les plutons (Fig. 4). These granites evolved from biotite to zinnwaldite facies containing 0.04-0.20 wt.% Li2O. Hydrothermal greisens, forming cupolas in the uppermost part of granite intrusions at Krásno, are also enriched in Li (0.6 wt.% Li2O), while vein-shaped and pericontact greisens in northern and northeastern parts of the Nejdek pluton are Li-poor (usually below 0.1 wt.% Li2O). The second group, only slightly peraluminous A-type granites, form a large volcano-plutonic complex of the Teplice caldera in the eastern Erzgebirge (Fig. 5). While early rhyolite tuffs are Li-poor (< 0.05 wt.% Li2O), later granites contain up to 0.2 wt.% Li2O in zinnwaldite facies in the upper parts of the cupolas at Cínovec and Krupka. Hydrothermal greisenization in the uppermost parts of cupolas increased the Li contents up to 0.4-1 % wt.% Li2O (0.6 wt.% Li2O on average). The only Li carrier is represented by trioctahedral Li-Fe micas with the contents from 0.25 wt.% Li2O in biotite to 4.8 wt.% Li2O in zinnwaldite (Fig. 6). The Cínovec-Zinnwald represents the only potential Li deposit in the Czech Republic. [ABSTRACT FROM AUTHOR]

Tors represent one of the most characteristic landforms in the uplands and mountains of Central Europe, including the Sudetes, Czech-Moravian Highlands, Šumava/Bayerischer Wald, Fichtelgebirge or Harz. These features occur in a range of lithologies, although granites and gneisses are particularly prone to tor formation. Various models of tor formation and development have been presented, and for each model the tors were thought to have evolved under specific environmental conditions. The two most common theories emphasised their progressive emergence from pre-Quaternary weathering mantles in a two-stage scenario, and their development across slopes under periglacial conditions in a one-stage scenario. More recently, tors have been analysed in relation to ice sheet extent, the selectivity of glacial erosion, and the preservation of landforms under ice. In this paper we describe tor distribution across Central Europe along with hypotheses relating to their formation and development, arguing that specific evolutionary histories are not supported by unequivocal evidence and that the scenarios presented were invariably model-driven. Several examples from the Sudetes are presented to demonstrate that tor morphology is strongly controlled by lithology and structure. The juxtaposition of tors of different types is not necessarily evidence that they differ in their mode of origin or age. Pathways of tor remodelling and degradation under subaerial conditions are identified and it is argued that processes of tor formation and development are ongoing. Thus, tors are not reliable indicators of past environments, because they are considerably influenced by both geological factors, such as lithology and structure, and geomorphological factors such as hillslope setting.. [ABSTRACT FROM AUTHOR]

The region of Central Europe, Adriatic region and Balkan Peninsula were subjects of geo-kinematical monitoring in several projects performed since 1992. Independent GPS epoch-wise observing campaigns took place in several regions and the whole territory is now covered by tens of permanent stations. The long-term observational series from permanent stations generally yield reliable site velocities, however distribution of such stations is not dense enough to provide velocity field with sufficient resolution all over the monitored region. On the other side the epoch-wise campaigns sites are much denser than the permanent ones, however the repeated epoch observations are not very frequent and their referencing is not unique. In the paper we shortly describe velocity fields available from various national and regional GPS geo-kinematics projects and an attempt to analyzed and interpret the homogenized the velocity fields in relationship to pozition of the important tectonic zones located in the Central Europe. In the paper we shortly describe velocity fields available from various national and regional GPS geo-kinematics projects and an attempt to analyzed and interpret the homogenized the velocity fields in relationship to pozition of the important tectonic zones located in the Central Europe. [ABSTRACT FROM AUTHOR]

In this paper, laser ablation ICP-MS U-Pb detrital zircon ages are used to discuss provenance and early Palaeozoic palaeogeography of continental fragments that originated in the Cadomian-Avalonian active margin of Gondwana at the end of Precambrian, were subsequently extended during late Cambrian to Early Ordovician opening of the Rheic Ocean, and finally were incorporated into and reworked within the European Variscan belt. The U-Pb detrital zircon age spectra in the analysed samples, taken across a late Neproterozoic (Ediacaran) to Early/Middle Devonian metasedimentary succession of the southeastern Teplá-Barrandian unit, Bohemian Massif, are almost identical and exhibit a bimodal age distribution with significant peaks at about 2.1-1.9 Ga and 650-550 Ma. We interpret the source area as an active margin comprising a cratonic (Eburnean) hinterland rimmed by Cadomian volcanic arcs and we suggest that this source was available at all times during deposition. The new detrital zircon ages also corroborate the West African provenance of the Teplá-Barrandian and correlative Saxothuringian and Moldanubian units, questioned in some palaeogeographic reconstructions. Finally, at variance with the still popular concept of the Cadomian basement units as far-travelled terranes, we propose that early Palaeozoic basins, developed upon the Cadomian active margin, were always part of a wide Gondwana shelf and drifted northwards together before involvement in the Variscan collisional belt. [ABSTRACT FROM AUTHOR]

A comprehensive anatomical and mineralogical study of fossil wood fragments from fields in the vicinity of Bečov and Břvany villages (NW Bohemia, Czech Republic) indicates that Taxodioxylon gypsaceum (Cupressaceae s.l.) predominates, but also identifies another coniferous wood: Pinuxylon parryoides (Pinaceae) and three angiosperms Quercoxylon böckhianum , Castanoxylon bavaricum and Lithocarpoxylon sp. (all Fagaceae). This paper therefore presents the first occurrence of Pinaceae and Fagaceae fossil wood in the volcanic rocks of the České Středohoří Mts. as well as its youngest palaeobotanical record in general, late Oligocene in age (26.56 ± 0.38 Ma). The samples were buried by alkaline pyroclastic deposits and were mineralized by carbonates. Two distinct depositional processes burying the fossil woods were identified. Closer to the vent, the woods occur in a near-vent pyroclastic fall deposits of the former pyroclastic cone, whereas more distant sites consist of pyroclastic flow deposits. Carbonate mineralization mostly consists of dolomite, but subordinate amounts of magnesite (likely the first time this is documented in fossil wood) as well as calcite and siderite are present. Only one sample collected in the same area, bearing clear signs of riverbed transport (Lithocarpoxylon sp.), was perfectly silicified, but its origin remains unclear. • Consideration of individual and interspecific variability in fossil wood anatomy. • Whole-plant concept and its application when defining new fossil plant taxa. • Unique mineralization of fossil wood with magnesite. [ABSTRACT FROM AUTHOR]

In the accompanying paper (Part A), depth-recursive tomography was applied to the CEL09 refraction data. A deblurred P-wave velocity image was obtained down to a depth of 20 km. This paper (Part B) is devoted to the interpretation of the upper- and middle-crustal structures of the Bohemian Massif imaged in the CEL09 section. Because of inherent ambiguity of the refraction method in imaging low-velocity zones, other well-known results based on other geophysical data sets are also used to independently verify the interpreted velocity features. Comparison with the density and velocity models previously obtained indicates that the presented P-wave velocity image has superior resolution revealing or verifying a number of geological features. The prominent lateral velocity changes encountered in the CEL09 pattern across the imaged crustal section were used to delineate the main terranes and deep regional fault zones such as the Krušné hory Fault, the SW continuation of the Litoměřice Fault Zone, the West and Central Bohemian Shear Zones, the Blanice-Rodl Fault, the Přibyslav-Vitis Fault and the Boskovice-Diendorf Fault. The 450-km-long CEL09 transect reveals seven major deeply rooted high-velocity (HV) anomalies identified as Variscan massifs intruded near or within these deep fault zones. They form buried ridges mostly parallel to the SW-NE trending Variscan strike. Their discovery allows new insights into a number of phenomena such as the West Bohemian earthquake swarms, the Saxothuringian paradox, the character of the Saxothuringian-Barrandian contact zone, the detachment surface due to the slab of the Saxothuringian crust subducting beneath the Teplá-Barrandian zone in the Devonian, the depth extent of the Mariánské-Lázně Complex (MLC) as an equivalent unit of the Zone Erbendorf-Vohenstrauss (ZEV), the subsidence of the Barrandian syncline, the root zones of the Central and South Bohemian Plutons, the accretionary wedge formed along the Moravo-Moldanubian suture and its link with the Gföhl terrane, the Carpathian foreland relief and the subsidence observed in the Vienna Basin. [ABSTRACT FROM AUTHOR]

The refraction CEL09 profile from the CELEBRATION 2000 project intersects the main terranes of the Bohemian Massif in the NW-SE direction: the Saxothuringian, the Teplá-Barrandian, the Moldanubian and the Moravo-Silesian. In its easternmost part, it crosses the Western Outer Carpathians overthrust westward onto the Bohemian Massif. Only the first 450 km were surveyed with the densest deployment of shot points providing data suitable for a reliable geological interpretation. The first-arrival depth-recursive tomography was applied here to derive a P-wave velocity image of the upper and middle crust (Part A). The proper interpretation of the obtained velocity features is the subject of the accompanying paper (Part B). The attained resolution in the velocity image is shown to be superior as compared with the previous CEL09 models based also on the more uncertain later arrivals of reflection waves. The applied DRTG (depth-recursive tomography on grid) method is based on a regular network of refraction grid rays generated for iteratively updated starting models. Only the distinct first arrivals with minimum uncertainty are used for the DRTG inversions to yield the maximum resolution. Thanks to the full control of the data fit by the grid rays used, the statistical lateral resolution could be determined at single grid depths for the chosen confidence levels. Thus, the lateral sizes of the anomalies that can be yet resolved are determined in dependence on their depths and their velocity excesses. The defocusing of the imaged features is studied on the basis of the spatial responses to spike excitation. The calculated spatial responses also allowed the edge smearing of the velocity anomalies to be assessed. Special attention is paid to the imaging of low-velocity zones that are usually suppressed by the smoothing measures used in standard tomographic methods. An improvement was achieved if the smoothing was suggested with regard to the occurrence of the low-velocity zones repeatedly appearing in higher iterations. The gained deblurring effect concerns both the negative and positive anomalies as documented on the velocity features interpreted in the accompanying paper. [ABSTRACT FROM AUTHOR]

The paper describes the predispositions and the genesis of stone tables, which are naturally - not anthropogenically - formed, rather rarely occurring geomorphic rock forms of tablelike shape. They are composed of subhorizontal desk overlying the cavity and held up by at least one supporting rock block. Part of the table or even the entire table is not in its original in situ position, because individual components or the table could have been gravitationally shifted. For closer investigation, 8 stone tables from 3 geomorphologically different areas were chosen (Fig. 1). Five stone tables occur in the Radhošťská hornatina Upland, which is a part of the Outer Western Carpathians, composed of flysch rocks of Cretaceous-Paleogene age. One locality is situated below the highest peak of the Ondřejník geomorphic unit, which is considered to be a nappe outlier consisting of Cretaceous flysch rocks. Two remaining tables occur in the Satovská pahorkatina geomorphic unit as a part of the Bohemian Massif. The area is formed of Proterozoic orthogneiss. Directly on rock surfaces of the tables, the structural measurements were performed using geological compass. The results were presented as rose and pole diagrams and were compared with the reference measurements from the surroundings. Where there was a lack of proper rock outcrops, the structural measurements from crevice-type caves situated close to the individual stone tables were used. The results are shown in Figs 2 and 3. Except for table "c", all tables are formed in close connection with the development of slope deformations. Table "c" is formed within a forest road cut in the gravitationally non-affected area. The results indicated that the basic predisposition for stone table formation is the exposure of subhorizontal sedimentary beds, metamorphic layers or similarly jointed magmatic rock in relation to the dip of slope. The second predisposition is a vertical jointing of the mature rock. The genesis of stone tables is connected mainly with gravitational processes, when individual blocks are shifted and joints become widened, or with the selective weathering and erosion, when particular components of stone tables are shaped. However, the stone table is very often a result of combined complex processes, when the slope is totally affected by gravitational processes with subsequent effect of selective weathering and erosion. Unlike dolmens described in literature, the anthropogenic origin of stone tables described in this paper is doubtful. The evidences against the artificial origin are as follows: (i) great amount of detected forms in different phases of evolution, (ii) tight similarity between structural values measured on the tables and reference values from the surrounding rocks or crevice-type caves, (iii) identified context, when tables or their components are always formed in vertically jointed rocks, which are gravitationally affected, (iv) inaccessibility of the localities, often within the landslide rocky terrains. [ABSTRACT FROM AUTHOR]

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Orogenic peridotites in the crystalline basement of the northwestern Bohemian Massif contain multiphase solid inclusions (MSI), which are interpreted to be crystallisation products of trapped former carbonate–silicate melts metasomatizing their host rocks. We applied conventional thermobarometry and forward thermodynamic modelling to constrain the P–T evolution ranging from the peak metamorphic conditions of the investigated harzburgite and lherzolite, through entrapment of the melts in the outer parts of garnets, to the (re)-equilibration of the MSI assemblages. The peak conditions of c. 1100 °C/4.5–5.5 GPa are recorded by garnet cores and large pyroxene porphyroclasts. The melt entrapment, during which garnet outer parts grew, was associated with influx of the metasomatizing liquids and probably took place during the early stage of the exhumation. Thermodynamic model of amphibole-free MSI assemblage comprising kinoshitalite/Ba-rich phlogopite (approximated by phlogopite in the model), dolomite, magnesite, clinopyroxene, orthopyroxene, garnet and chromite provided robust estimate of P and T of its (re)-equilibration, c. 900–1000 °C, 1.8–2.2 GPa. Furthermore, the lack of olivine reflects co-existence of COH fluid with high X(CO2) = CO2/(CO2 + H2O) ≥ 0.6. Models employing identical P–T–X(CO2) parameters successfully reproduced the other two amphibole-bearing assemblages observed. The modelled stability fields show perfect alignment with a characteristic isobaric segment of the solidus curve of carbonated peridotite. This co-incidence implies that the (re)-equilibration corresponds to the termination of the melt crystallisation once the near-isothermal exhumation path intersected the solidus. Decreased solubility of silicates at the carbonated peridotite "solidus ledge", inferred from the published experimental data, as well as concentric textures of some MSI indicates sequential crystallisation from the early silicates to late dolomite. The carbonated "solidus ledge" is a relatively narrow boundary in the lithospheric mantle capable of an abrupt immobilisation of fluxing or transported carbonated melts. The investigated rocks are estimated to store approximately 0.02 kg C/m3 (or 6 ppm C) occurring as carbonates in the MSI. [ABSTRACT FROM AUTHOR]

The studied Mokrsko-West (90–100 t Au), Mokrsko-East (30 t Au) and Čelina (11 t Au) deposits represent three spatially and genetically interrelated deposits of supposed affiliation to the intrusion-related gold deposit type. The deposits differ in their dominant host rocks, which are represented by ca 354 Ma old biotite tonalite (Mokrsko-West) and Neoproterozoic volcanic and volcanosedimentary rocks (Mokrsko-East, Čelina). Another difference lies in the style of veining — densely spaced networks of 0.1–5 mm thin veins (Q 2 ) within the tonalite, compared to thick (usually 5–20 cm; Q 1–2 ) and widely spaced veins within the Neoproterozoic rocks. Five generations of quartz veins, referred to as Q 0 through Q 4 were distinguished: Q 0 veins are the oldest and ore-barren, Q 1 veins mark the onset of the Au-ore formation, Q 2 veins its culmination and Q 3 veins its fading. Late quartz gangue (Q 4 ) is associated with uneconomic Ag–Pb–Zn vein-type ores hosted by calcite–barite–(quartz) veins. Quartz vein thickness (~ 0.3 to ~ 300 mm), spacing (~ 3 mm to ~ 500 mm), distribution, and related extensional strain (ca. 3–25%) evolve systematically across the studied ore district, reflecting both the major host rock and other tectonic factors. Detailed study of vein dimension parameters (thickness, length, width, aspect ratios) allowed estimation of the probable depth of the fluid source reservoir (~ 2 km or ~ 4 km) below the present surface. The depth to the fluid source seems to increase through time, being the shallowest for the Q 0 veins and the deepest for the Q 2 veins. Two independent methods of estimating fluid overpressure are discussed in the paper. Fluid overpressure during vein formation decreases from the Q 0 through the Q 2 veins, from 10 to 4 MPa or from 26 to 10 MPa, depending on the assumed tensile strength of the tonalite (5.5 and 15 MPa, respectively). The origin of joints and veins is discussed in terms of the stress orientation and crack-seal and crack-jump mechanisms. Field relationships unambiguously indicate that the veins hosted by Neoproterozoic rocks originated by reopening of the pre-existing extension joints (J 1 ) due to fluid overpressure. The origin of the densely-spaced thin veins (Q 2 ) hosted by the tonalite at the Mokrsko-West deposit is, however, less certain. It is probable that the tonalite was already affected by microfracturing analogous to the J 1 joints prior to the formation of quartz veins. The formation of the Q 1–2 veins at the Mokrsko-East deposit was constrained by the Re–Os dating of molybdenite to 342.9 ± 1.4 Ma. The ore-bearing hydrothermal system is thus ca 12 Ma younger than the tonalite that hosts the Mokrsko-West deposit. A similar ca 15–2 Ma difference between the age of the host-intrusion and the age of the hydrothermal event was encountered in several other gold deposits in the vicinity of the Central Bohemian Plutonic Complex. Two hypotheses to explain this are discussed in the paper. [ABSTRACT FROM AUTHOR]

The paper presents the results of velocity analysis performed in the Nesvačilka and Vranovice troughs. The troughs extend in the south-eastern part of the Bohemian Massif (the Moravian Block). As both belong to the most promising areas of the Bohemian Massif in the search for and production of hydrocarbons, their geological and geophysical survey is very important. Therefore, one of the key points is to determine the accurate data on the depth of the significant geological and stratigraphic units, which form the Nesvačilka and the Vranovice troughs. For this purpose the velocity analysis and the application of synthetic seismograms have been defined and applied. The results indicate that the lithostratigraphic units of the studied region are characterized by a large velocity interval. Based on the data from well log measurements (check shots) and synthetic seismograms the following velocities of seismic waves were determined in single lithostratigraphic units: 2.4-3.3 km/s in sediments of Flysch nappes, 2.7-3.6 km/s in the Palaeogene sediments, 3.3-4.3 km/s in the Jurassic sediments (3.7-5.1 km/s in carbonates and 3.5-4.8 km/s in pelites and conglomerates), 4-5.4 km/s in the Carboniferous sediments, and 4.6-6.6 km/s in the Devonian carbonates. Moreover, the synthetic seismograms and check shot results point to significant velocity interfaces. We discovered that: (a) within the sediments of Flysch nappes velocities in Menilitic Formation are higher than in the Submenilitic and the Ždánice-Hustopeče formations, (b) interface sediment of the Flysch nappes and Palaeogene deposits is characterized by a decrease of velocity, and (c) big contrast of velocity reflects the boundary between the carbonates (the Devonian and the Jurassic) and their surrounding rocks. The velocity analysis helps significantly for mapping of the Outer Carpathian Flysch nappes (the Pouzdřany Unit and especially the Ždánice Unit), the Neogene deposits, the Palaeogene deposits and the Devonian carbonates. All the knowledge we obtained has been used in detailed mapping and assessment of potential and confirmed hydrocarbon deposits in the studied area. [ABSTRACT FROM AUTHOR]

The Sn-W ore deposits in the Krupka surroundings are associated with greisens, which occur in the upper parts of Late Variscan granitoid intrusions. Fluid inclusions were studied in samples of quartz, cassiterite, apatite, fluorite, and topaz in greisenized granites, greisens, and hydrothermal veins with Sn-W mineralization. The greisenization process took place at temperatures 370–490 °C and pressures 155–371 bars, and associated fluids had predominantly low salinity and a low gas (CO2, N2 and CH4) content. The post-greisenization stage was connected with the formation of (i) low-salinity (0–8 wt. % NaCl eq.) fluid inclusions with homogenization temperatures <120–295 °C and (ii) high-salinity (18 to >35 wt. % NaCl eq.) fluid inclusions with homogenization temperatures 140–370 °C, often containing trapped crystals of quartz, topaz, and sulfides, or daughter crystals of salts and carbonates, which were identified by microthermometric measurements, electron microprobe analysis, and Raman spectroscopy. Analyses of fluid inclusion leachates have shown that Na and Ca chlorides predominate in fluids. According to hydrogen stable isotopes, the source of greisenizing and post-greisenizing fluids was not only magmatogenic but also meteoric water or fluids derived from sedimentary rocks. [ABSTRACT FROM AUTHOR]

Mafic granulite, generated from eclogite, occurs in felsic granulite at Kleť, Blanský les, in the Bohemian Massif. This is significant because such eclogite is very rare within the felsic granulite massifs. Moreover, at this locality, strong interaction has occurred between the mafic granulite and the adjacent felsic granulite producing intermediate granulite, such intermediate granulite being of enigmatic origin elsewhere. The mafic granulite involves garnet from the original eclogite, containing large idiomorphic inclusions of omphacite, plagioclase and quartz, as well as rutile. The edge of the garnet is replaced by a plagioclase corona, with the garnet zoned towards the corona and also the inclusions. The original omphacite-quartz-?plagioclase matrix has recrystallized to coarse-grained polygonal ('equilibrium'-textured) plagioclase-diopsidic clinopyroxene-orthopyroxene also with brown amphibole commonly in the vicinity of garnet. Somewhat larger quartz grains are embedded in this matrix, along with minor ilmenite, rutile and zircon. Combining the core garnet composition with core inclusion compositions gives a pressure of the order of 18 kbar from assemblage and isopleths on a P−T pseudosection, with temperature poorly constrained, but most likely >900 °C. From this P−T pseudosection, the recrystallization of the matrix took place at ~12 kbar, and from Zr-in-rutile thermometry, at relatively hot conditions of 900-950 °C. It is largely at these conditions that the eclogite/mafic granulite interacted with the felsic granulite to make intermediate granulite (see next paper). [ABSTRACT FROM AUTHOR]

This paper describes late Cambrian dikes and Early Ordovician volcano-sedimentary successions of the Prague Basin, Bohemian Massif, to discuss the timing and kinematics of breakup of the northern margin of Gondwana. Andesitic dikes indicate minor E-W crustal extension in the late Cambrian, whereas the Tremadocian to Dapingian lithofacies distribution and linear array of depocenters suggest opening of this Rheic Ocean rift-related basin during NW-SE pure shear-dominated extension. This kinematic change was associated with the onset of basic submarine volcanism, presumably resulting from decompression mantle melting as the amount of extension increased. We conclude from these inferences and from a comparison with other Avalonian-Cadomian terranes that the rifting along the northern Gondwana margin was a two-stage process involving one major pulse of terrane detachment in the early Cambrian and one in the Early Ordovician. While the geodynamic cause for the former phase remains unclear, but still may include effects of Cadomian subduction (roll-back, slab break-off), isostatic rebound, or mantle plume, the incipient stage of the latter phase may have been triggered by the onset of subduction of the Iapetus Ocean at around 510 Ma, followed by advanced extension broadly coeval (Tremadocian to Darriwilian) in large portions of the Avalonian-Cadomian belt. Unequal amounts of extension resulted in the separation and drift of some terranes, while other portions of the belt remained adjacent to Gondwana. [ABSTRACT FROM AUTHOR]

Abstract: The Teplá–Barrandian unit (TBU) of the Bohemian Massif exposes a section across the once extensive Avalonian–Cadomian belt, which bordered the northern active margin of Gondwana during late Neoproterozoic. This paper synthesizes the state-of-the-art knowledge on the Cadomian basement of the TBU to redefine its principal component units, to revise an outdated stratigraphic scheme, and to interpret this scheme in terms of a recent plate-tectonic model for the Cadomian orogeny in the Bohemian Massif. The main emphasis of this paper is on an area between two newly defined fronts of the Variscan pervasive deformation to the NW and SE of the Barrandian Lower Paleozoic overlap successions. This area has escaped the pervasive Variscan (late Devonian to early Carboniferous) ductile reworking and a section through the Cadomian orogen is here superbly preserved. The NW segment of the TBU consists of three juxtaposed allochthonous belts of unknown stratigraphic relation (the Kralovice–Rakovník, Radnice–Kralupy, and Zbiroh–Šárka belts), differing in lithology, complex internal strain patterns, and containing sedimentary and tectonic mélanges with blocks of diverse ocean floor (meta-)basalts. We summarize these three belts under a new term the Blovice complex, which we believe represents a part of an accretionary wedge of the Cadomian orogen. The SE segment of the TBU exposes the narrow Pičín belt, which is probably a continuation of the Blovice complex from beneath the Barrandian Lower Paleozoic, and a volcanic arc sequence (the Davle Group). Their stratigraphic relation is unknown. Flysch units (the Štěchovice Group and Svrchnice Formation) overlay the arc volcanics, and both units contain material derived from volcanic arc. The former was also sourced from the NW segment, whereas the latter contains an increased amount of passive margin continental material. In contrast to the Blovice complex, the flysch experienced only weak Cadomian deformation. The new lithotectonic zonation fits the following tectonic scenario for the Cadomian evolution of the TBU well. The S- to SE-directed Cadomian subduction beneath the TBU led to the involvement of turbidites, chaotic deposits, and 605±39Ma ocean floor in the accretionary wedge represented by the Blovice complex. The accretionary wedge formation mostly overlapped temporally with the growth of the volcanic arc (the Davle Group) at ~620–560Ma. Upon cessation of the arc igneous activity, the rear of the wedge and some elevated portions of the arc were eroded to supply the deep-water flysch sequences of the Štěchovice Group, whereas the comparable Svrchnice Formation (~560 to <544Ma) was deposited in a southeasterly remnant basin close to the continental margin. The Cadomian orogeny in the TBU was terminated at ~550–540Ma by slab breakoff, by final attachment of the most outboard ~540Ma oceanic crust, and by intrusion of ~544–524Ma boninite dikes marking the transition from the destructive to transform margin during the early/middle Cambrian. [Copyright &y& Elsevier]

Abstract: The Czech Republic comprises two geologically diverse provinces. The western part is an ancient, long-stabilized crystalline (slowly uplifting) massif, the Bohemian Massif, whereas the eastern part is the younger and tectonically more mobile Carpathian Foredeep and the West Carpathian mountain ranges. The Late Cenozoic fluvial record, controlled in essence by cyclic climate-driven changes of the environment shows discernible differences in both provinces and, therefore, the paper deals with these separately. In the Bohemian Massif a regular development of terrace staircases is noted, making internally consistent correlation possible. Problems that remain open to debate include dating the start of fluvial terrace staircase development, and correlating the fluvial terraces with the succession of Scandinavian glaciations that have affected the northernmost Czech Republic. On the other hand, the fluvial records in the southeastern Czech Republic show significant lateral variations; thus, northern, central and southern Moravia are reviewed separately in this paper. The terrace system in northern Moravia formed in direct contact with the ice sheet during two Scandinavian glaciations, whereas only periglacial or extraglacial conditions developed further south. Nevertheless, the existence of the Main Terrace as an important stratigraphical index horizon allows the reliable correlation of the terrace systems of all the larger Moravian rivers, despite their fragmentary development. [Copyright &y& Elsevier]

In this paper, U-Pb zircon, monazite and rutile data for crystalline rocks deposited as clasts in the Upper Viséan conglomerates at the eastern margin of the Bohemian Massif are reported. U-Pb data of spherical zircon from three different granulite clasts yielded a mean age of 339.0 ± 0.7 Ma (±2 σ), while oval and spherical grains of another granulite pebble define a slightly younger date of 337.1 ± 1.1 Ma. These ages are interpreted as dating granulite facies metamorphism. Thermochronology and the derived pressure–temperature ( P–T) path of the granulite pebbles reflect two-stage exhumation of the granulites. Near-to-isothermal decompression from at least 44 km to mid-crustal depths of around 22 km was followed by a near-isobaric cooling stage based on reaction textures and geothermobarometry. Minimum average exhumation rate corresponds to 2.8–4.3 mm year−1. The extensive medium-pressure/high-temperature overprint on granulite assemblages is dated by U-Pb in monazite at c. 333 Ma. This thermal event probably has a close link to generation and emplacement of voluminous Moldanubian granites, including the cordierite granite present in clasts. This granite was emplaced at mid-crustal levels at 331 ± 3 Ma (U-Pb monazite), whereas the U-Pb zircon ages record only a previous magmatic event at c. 378 Ma. Eclogites and garnet peridotites normally associated with high-pressure granulites are absent in the clasts but exotic subvolcanic and volcanic members of the ultrapotassic igneous rock series (durbachites) of the Bohemian Massif have been found in the clasts. It is therefore assumed that the clasts deposited in the Upper Viséan conglomerates sampled a structurally higher tectonic unit than the one that corresponds to the present denudation level of the Moldanubicum of the Bohemian Massif. The strong medium-temperature overprint on granulites dated at c. 333 Ma is attributed to the relatively small size of the entirely eroded bodies compared with the presently exposed granulites. [ABSTRACT FROM AUTHOR]

As part of the international refraction measurements in Central Europe in the year 2000, three profiles traversed the region of earthquake swarms in West-Bohemia/Vogtland. The shots were also recorded at the permanent stations of the local seismic networks. The travel times of P-waves, observed in the West-Bohemian region, are discussed and interpreted in the present paper. In general, significantly lower P-wave velocities were found in the Saxothuringian (northern) part of the studied area than in the adjacent southern parts. The observed travel times are interpreted separately for the individual geological units, in particular for the plutons, crystallinicum, and the Mariánské Lázně (Marienbad) Complex. After smoothing the selected data using rational approximations, the Wiechert-Herglotz method was used to compute vertically inhomogeneous velocity models. The characteristic features of the derived models are relatively low P-wave velocities at the surface and prominent velocity increases within the uppermost crust down to a depth of about one kilometre. [ABSTRACT FROM AUTHOR]

In the time span from January 1995 to December 1999 the Czech National Seismological Network (CNSN), consisting of ten permanent digital broadband stations, several local networks and two data centers, detected and recorded 9530 regional natural seismic events, 27 greater than magnitude 2. Most of these events were located by the Czech Seismological Service (CSS), and the most prominent of them were analyzed in detail. A large number of quarry blasts were recorded as well but were not included in the analysis. We provide basic information on the configuration of the CNSN and on the way of routine data processing employed by the CSS in this paper. The over-all regional seismicity monitored by the CNSN in 1995–1999 is briefly reviewed. The main results of observations and evaluation of the local (NW-Bohemia/Vogtland, South Bohemia, Sudeten) and induced (Kladno, Příbram, Upper Silesia, Lubin/Poland) seismic activity within this period are presented in a condensed form. Finally, a summary on macroseismic observations on the territory of the Czech Republic in 1995–1999 is also presented. [ABSTRACT FROM AUTHOR]

The Kamieniec Metamorphic Belt (KMB) and the Doboszowice Metamorphic Complex (DMC) expose a fragment of the pre-Variscan volcano-sedimentary cover preserved in the Fore-Sudetic Block in the NE part of the Bohemian Massif. We present the age of detrital and magmatic zircon grains and the bulk rock chemical composition of rock samples from the KMB and the DMC to better understand the evolution of the early Palaeozoic Gondwana margin. The zircon age spectra were acquired by U–Pb LA–ICP–MS dating and represent two groups that differ by maximum depositional age (MDA). The paragneiss from the DMC displays the MDA at 456 Ma, whereas the mica shist from the KMB displays the MDA at 529 Ma. Older age peaks in both groups of samples are represented by the Neoproterozoic and less frequent the Paleoproterozoic and Archean. The data presented indicate that the rock successions were sourced from the Cadomian orogen and deposited in the basins that developed on the Gondwana margin. Our results support the suggestion that the crystalline basement in the eastern part of the Fore-Sudetic Block has an affinity to the Trans-Saharan Belt or West African Craton and was part of a Gondwana shelf. The final stage of evolution of the studied successions was related to the Variscan thermal overprint. Based on presented data, we support the idea that the suture separating the Brunovistulian domain from the rest of the Gondwana-derived terranes is not related to the closure of the Rheic Ocean and represents a local feature. [ABSTRACT FROM AUTHOR]

Belemnites and calcareous nannoplankton (which are both stratigraphically and palaeoecologically important groups of organisms) have been used as crucial evidence for exploring an extended timespan of Jurassic sedimentation in the northern part of the Bohemian Massif. Tectonically and fragmentarily preserved Jurassic strata along the Lausitian Fault have long been considered exclusively as belonging to the Callovian through the Kimmeridgian. Based on a systematic revision of older collections, new sediment sampling and analysing data, the stratigraphic range of Jurassic sedimentation in the northern part of the Bohemian Massif has been extended, at least from the Bajocian until the Tithonian. Belemnite taxa are represented by six species and two taxa identified as Megateuthis cf. M. elliptica and Cylindroteuthis cf. C. puzosiana (five genera belonging to four families) document a stratigraphic range from the Bajocian (Megateuthis suevica and Megateuthis cf. M. elliptica) through the Kimmeridgian. Additionally, calcareous nannofossils do not contradict the Bajocian–Kimmeridgian while also proving the Tithonian age. Moreover, belemnites clearly show the prevailing Tethyan (Belemnopsis fauna) but also Boreal (Cylindroteuthis cf. C. puzosiana) provenance. Recorded fossils reveal a longer time span of sedimentation than previously known (starting at least in the Bajocian and terminating in the Tithonian), suggesting the existence of a significantly larger sedimentary basins that had been eroded prior to the Cenomanian transgression event (Upper Cretaceous). [ABSTRACT FROM AUTHOR]

The Jizerka Quaternary alluvial placer in the Czech Republic has been a well-known source of gemstones since the 16th century, and the only one in Europe that has yielded a significant amount of jewel-quality sapphire. Besides Mg-rich ilmenite ("iserine"), which is the most common heavy mineral at the locality, some other minerals have been mined for jewellery purposes. These are corundum (sapphire and ruby varieties), zircon ("hyacinth" gemstone variety) and spinel. Here, we present a detailed petrological and geochronological investigation of the enigmatic relationship between the sapphires and their supposed host rocks, supporting their xenogenetic link. Our hypothesis is based on thermal resetting of the U–Pb isotopic age of the zircon inclusion found inside Jizerka blue sapphire to the estimated time of the anticipated host alkaline basalt intrusion. The host rocks of the gemstones (sapphire and zircon) and Mg-rich ilmenite are not yet known, but could be related to the Cenozoic volcanism located near the Jizerka gem placer (Bukovec diatreme volcano, Pytlácká jáma Pit diatreme and Hruškovy skály basalt pipe). The transport of sapphire, zircon and Mg-rich ilmenite to the surface was connected with serial volcanic events, likely the fast ascent of alkali basalts and formation of multi-explosive diatreme maar structures with later deposition of volcanoclastic material in eluvial and alluvial sediments in nearby areas. All mineral xenocrysts usually show traces of magmatic corrosion textures, indicating disequilibrium with the transporting alkali basalt magma. In order to constrain the provenance and age of the Jizerka placer heavy mineral assemblage, zircon inclusion and associated phases (niobian rutile, baddeleyite and silicate melts) in the blue sapphire have been studied using LA–ICP–MS (laser ablation–inductively coupled plasma–mass spectrometry) geochemistry and U–Pb in situ dating. Modification of the zircon inclusion into baddeleyite by exposure to temperature above 1400 °C in a basaltic melt is accompanied by zircon U–Pb age resetting. A zircon inclusion in a Jizerka sapphire was dated at 31.2 ± 0.4 Ma, and its baddeleyite rim at 31 ± 16 Ma. The composition of the melt inclusions in sapphire and incorporated niobian rutile suggests that the parental rock of the sapphire was alkali syenite. The Eocene to late Miocene (Messinian) ages of Jizerka zircon are new findings within the Eger Graben structure, as well as among the other sapphire–zircon occurrences within the European Variscides. Jizerka blue sapphire mineral inclusions indicate a provenience of this gemstone mineral assemblage from different parental rocks of unknown age and unknown levels of the upper crust or lithospheric mantle. [ABSTRACT FROM AUTHOR]

This paper describes a pair of intensively studied deep seated gravitational slope deformations from the Czech Republic. Structural geological mapping and the interrogation of high resolution LiDAR DEMs have been used to reassess the extent of each slope deformation and to obtain new information about their surface morphologies. Electrical resistivity tomography has been used to image the subsurface structures while rod dilatometers and permanently installed mechanical extensometers have been used to define their kinematic behaviour. Dilatometric measurements from across a fissure the edge of the Mužský Hill DSGSD show that the progressive trend has been interspersed by five periods of movement acceleration since monitoring began in 1990 while extensometric measurements from across a second fissure about 50 m from the edge of the plateau show that this discontinuity was affected by an significant period of extension from 2004 to 2006 and a significant period of compression from 2006 to 2008. These data demonstrate that the Mužský Hill DSGSD is characterised by the lateral spreading of rigid sandstone blocks across a plastic marl formation at the edge of Příhrazy Plateau. Extensometric measurements from the Kněhyně Mountain DSGSD show that a fault located at a depth of about 25 m below the surface is characterised by progressive dilation whereas a fault located at a depth of about 57.5 m below the surface is characterised by episodic vertical dip-slip displacements. Both faults are affected by horizontal dextral strike slip displacements. These data demonstrate that the Kněhyně Mountain DSGSD is characterised by translational rocksliding associated with the neotectonic uplift of the Outer Western Carpathians. The presented kinematic data have been compared to records of precipitation, groundwater level, earthquakes, and strain changes measured by the fault displacement monitoring network EU-TecNet. Strain changes induced by the widespread redistribution of stress through the crustal appear to represent an important and hitherto underappreciated geomorphological process affecting the development of the slope deformations at Mužský Hill and Kněhyně Mountain. Future research will focus discovering whether this finding holds true for other deep seated gravitational slope deformations in different geomorphological and geological settings. [ABSTRACT FROM AUTHOR]

Amphibolite quarry at Markovice near Čáslav, eastern Bohemia, is known as an important mineral locality producing high-quality mineral specimens for more than 100 years. Mineral assemblages feature dominantly Alpine-type minerals. A student study by V. Janoušek and A. Laciok in 1988, guided by the late Professor L. Žák, dealt mainly with epidote-group minerals. Above all, the study provided detailed characteristics of garnet-anorthite symplectite formed by destabilization of clinozoisite-epidote. The symplectites often preserve outer crystal shapes of the original clinozoisite-epidote crystals. Minor relics in the symplectite show that the original clinozoisite-epidote contained 8 - 9 wt. % Fe2O3. The reaction Ep → Grt + An (+ O, H2O) at T ≈ 600 °C involved important Fe reduction, as the resulting garnet contains Alm 39.3, Adr 4.2, Grs 48.9, Prp 4.8, Sps 2.3, Uv 0.5 (mol. %). It is suggested that the geological and metamorphic evolution of the local amphibolites of the Kutná Hora Crystalline Unit included the following stages: 1) the older regional metamorphism that was instrumental in alteration of mafic volcanics and tuffs into amphibolite, 2) the brittle deformation, extension and fluid activity resulted in fractures with druses of clinozoisite-epidote, 3) in the course of a younger metamorphic event, the clinozoisite- epidote reacted under reducing conditions and its dehydration led to the formation of the studied garnet-anorthite symplectites, 4) later on, already at shallow crustal levels, late-Variscan, low-temperature fluids brought about crystallization of zeolites and hydrated silicates. The temporal sequence of processes is interpreted in terms of a polymetamorphic history of the host Kutná Hora Crystalline Unit. A repeated find of garnet-plagioclase symplectites replacing epidote crystal clusters in 2005 prompted preparation of this paper. [ABSTRACT FROM AUTHOR]

According to Czech legislative, the soil gas radon measurements are performed in a standard depth of 80 cm. However, on some localities characterized by low soil and subsoil thickness, this depth is not achievable. Therefore, the main aim of research activities was oriented to find out the depth relationship of soil gas radon concentration and its relation to additive radiometric parameters—gamma spectrometry and gamma dose rate. For practical use, the gamma dose rate was found to have better relationship to radon concentration than uranium concentration or total activity. The soil gas radon measurements were performed on 106 localities in the Czech Republic using the modified probe with side inlet of soil gas. The measurements were oriented to localities with demonstrably low thickness of soils and subsoils (in average 30–40 cm from surface to unweathered underlying rock). The choice of localities covered the most frequented rock types of the Czech Republic differing by radon index. For each locality, the complementary radiometric parameters (gamma dose rate and gamma spectrometry) were measured on the soil surface and closely situated rock outcrops. The growth of radon concentration with depth was confirmed on most of the localities with linear regression coefficient R = 0.95. The linear regression relationship was found between maximum soil gas radon concentration and gamma dose rate measured on the rock outcrops with coefficient R = 0.65 for all summarily processed data. The differences of this relationship were observed according to variability of lithological types and ranges of gamma dose rate. In a specified gamma dose rate ranges, the results could contribute to precising the method of building site assessment in conditions of low soil and subsoil thickness. [ABSTRACT FROM AUTHOR]

Rockslides in the Variscan orogenic belt of the Central Europe are a rare and poorly studied phenomenon. These relatively stable features have recently been shaped by secondary rockfall, toppling, sliding, or slumping. On afforested slopes, such processes can be efficiently analysed and dated by dendrogeomorphic methods. We performed detailed analyses of 355 increment cores from 81 Picea abies (L.) Karst. trees growing on two dormant rockslides in northeastern Czechia to reconstruct the activity of rock block movements and rockfalls. For the event determination we used standard event-response (I t) index and a semi-quantitative approach involving logical spatial position of disturbed trees during a three-year period. Furthermore, climate preparatory and triggering factors were analysed to investigate possible main drivers of recent secondary processes. Overall, four periods of certain block reactivations at the Prudký site since 1940 and seven periods of certain block reactivations at the Rudohorský site since 1834 were reconstructed. Most of the events can be dated to the period 1960–2000, but our data do not indicate any high-magnitude activity. This paper also demonstrates the results of tree eccentric growth not only in the main supposed direction of stem tilting but also in the direction perpendicular to the main direction when ca. 40% of all trees growing on rock blocks recorded the movements in both analysed axes of stem tilting, suggesting possible complex deformation and different directions of block movements over time. It also appeared that the periods with greatest activity of secondary movements were characterised by a significantly higher rain-on-snow factor (p = 0.007 and 0.026 at the Prudký and the Rudohorský site, respectively) thus indicating block detachments during periods of rapid snowmelt. • Dating of rock block movements and rockfalls using dendrogeomorphic techniques. • First chronologies of rockslide body disintegration in Variscan mid-mountains. • Spatial patterns of disturbed trees during three-year periods were examined. • Tree-ring data suggests complex movements of rock blocks in multiple directions. • Activity is related to years with significantly higher rain-on-snow precipitation. [ABSTRACT FROM AUTHOR]

The geological environment is undoubtedly one of the basic factors that influence the formation of surface runoff. The extent to which this factor can also affect the hydrodynamic characteristics of flash floods, which is also indirectly associated with flood risk, is the main topic of this study. In two geologically different areas of the Bohemian Massif (crystalline rocks predominate) and the western Carpathians (flysch rocks predominate), a total of 40 watersheds characterised by sharing a certain hydrological analogy were selected (20 watersheds from the Massif and 20 from the Flysch zone). In each of these watersheds, 1-year, 10-year and 100-year flash flood return periods were constructed using the two-dimensional hydrodynamic model Iber. The outputs from this model included raster datasets of areas, depths, and flow velocities during inundations. Subsequently, these rasters were analysed and compared with an emphasis on differences within the individual geological study areas. The outputs showed clear differences in the individual hydrodynamic characteristics (e.g. the average inundation area during Q100 was 29.07% larger in the Flysch than in the Massif). Overall, the Flysch zone appeared to be far riskier in terms of flash floods than in the case of the Bohemian Massif. [ABSTRACT FROM AUTHOR]

The results of geomorphological research into the Sazava river terraces are presented. This terrace system is characteristic by its variable structure which is conditioned by specific hydrodynamic processes that existed during the late Cenozoic evolution of the river valley. Two levels of Neogene fluvial sediments and seven Quaternary terrace accumulations along the Sazava course are distinguished. In the paper is also established their chronostratigraphical relation to the Vltava-Labe terrace systems. Morfostratigrafie teras řeky Sázavy v Českém masivu V práci jsou předloženy výsledky geomorfologického výzkumu říčních teras Sázavy. Tento terasový systém má velmi rozmanitou strukturu, která vznikala postupně působením specifických hydrodynamických procesů při vývoji údolí Sázavy v mladším kenozoiku. V údolí Sázavy byly zjištěny dvě úrovně neogenních říčních sedimentů a sedm stupňů terasových akumulací kvartérního stáří. Dnešní údolní dno střední části toku Sázavy leží vzhledem k nivě Vltavy ve zřetelně visuté poloze a na současnou úroveň bylo vyhloubeno převážně v době vzniku VI. terasy. Ve studii je také provedena chronostratigrafická korelace říčních teras Sázavy s terasami Vltavy a Labe. Podle aktuálního stratigrafického schématu kvartéru odpovídá celý systém teras Sázavy převážně období komplexu cromer po weichsel. Erozní fáze před akumulací I. terasy náleží v údolí Sázavy do závěru starého pleistocénu.

Abstract: The paper provides an overview of a several decades-long study of transitional Carboniferous–Permian (Stephanian C–Autunian) sedimentary successions in continental basins of the Czech part of the Bohemian Massif. These predominantly monotonous fluvial red beds intercalate with laterally widespread grey to variegated sediments of dominantly lacustrine origin. Both, fossil and climatic records show that apart from a generally known long-term climatic shift to drier conditions in Early Permian, the climate oscillated on several time scales throughout the study interval. Climatic indicators in the red beds part of the succession include palaeosols ranging between red vertisols and vertic calcisols suggesting strongly seasonal dry sub-humid climate. This is in agreement with the rarity of plant remains, which were mostly completely oxidised and only rarely preserved as plant impression in red mudstones or as silicified mostly gymnosperm woods in sandy channel fills. Silicification instead of coalification was the dominant fossilisation process during red-beds deposition. Even drier, possibly semi-arid climate may be indicated by spatially and temporarily restricted bimodal sandstones, dominated by well-rounded quartz grains and interpreted as eolian in origin. Periods of moist sub-humid (or even humid) climate were accompanied by formation of perennial lakes containing grey laminated mudstones, dark grey bituminous mudstones or limestones, muddy limestones, chert layers or even spatially restricted coals, some of them, however, of economic importance. Shorter climatic oscillations operating on a scale of tens to possibly hundreds of thousands of years are represented by transgressive–regressive lacustrine cycles followed by significant changes in lake water salinity reflected by boron content. The fossil record indicates the presence of dryland and wetland biomes in basinal lowlands although their proportions varied significantly as the climate changed. During deposition of red beds, the alluvial plain was vegetated dominantly by dryland biome assemblages. The composition of these assemblages is indicated by fairly common silicified gymnosperm (cordaitalean and coniferous) woods in sandstone–conglomerate fluvial channel bedforms and by poorly preserved impressions of walchian conifer shoots and cordaitalean leaves in associated mudstone intercalations. This is in agreement with sub-vertical root rhizolites and haloes in calcic vertisols. Occurrence of “wet spots” colonised by wetland assemblages is indicated by rather exceptional findings of silicified calamite stems in fluvial red beds associated with gymnospermous woods. During the humid intervals parts of the basinal lowlands were occupied by lakes surrounded by broad belts of wetland biome floras. During the “Stephanian C” most of these floras were dominated by tree ferns, calamites and sub-dominant pteridosperms. Local peat swamps were colonised by lycopsids including Sigillaria brardii, Asolanus camptotaenia and even some lepidodendrid lycopsids. In contrast, the fossil record of “Stephanian C” dryland floras is rarely preserved in lacustrine sediments. The fossil record of “Autunian” lakes, however, suggests increasing proportions of dryland elements, including conifers and peltasperms. The response of lacustrine faunas to climatic oscillations around the Carboniferous–Permian transition is less prominent than that of plants. The origin of the transition between the local Elonichthys–Sphaerolepis and Acanthodes gracilis bio/ecozones around the Carboniferous/Permian boundary is impossible to deduce from the existing fossil record. [Copyright &y& Elsevier]

The formation and exhumation of Variscan high- to ultrahigh-pressure metamorphic rocks from the Moldanubian Zone in the Bohemian Massif are the subject of controversy regarding their unclear relationship to possible subduction zones. In this paper we present the results of a petrological study of eclogites that occur together with serpentinites within amphibolite facies gneisses in the Moldanubian Zone, east of the Teplá–Barrandian Block. More than 100 bodies of retrogressed eclogite and serpentinite follow an approximately 250km long SW–NE trending zone in the central part of the Bohemian Massif. Together with surrounding gneisses, the eclogites share a medium to low-pressure amphibolite facies metamorphism. P–T conditions estimated for the eclogite facies stage indicate a relatively low-temperature geothermal gradient similar to those observed in the Saxothuringian Zone, which occurs north and northwest of the Teplá–Barrandian Block. The presence and distribution of eclogites and comparison of their P–T and age data with HP–UHPM rocks in other units in the Bohemian Massif allow us to constrain the Variscan suture, which straddles the SE of the Teplá–Barrandian Block. The existence of this suture in relation to available geotectonic models and its possible continuation through other allochthonous units along the European Variscan Belt are discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents monomineral and multiphase inclusions in garnet from eclogites and clinopyroxenites, which form layers and boudins in garnet peridotites from two areas in the Moldanubian zone of the Bohemian Massif. The garnet peridotites occur in felsic granulites and reached UHP conditions prior to their granulite facies overprint. In addition to complex compositional zoning, garnets from hosting eclogites and clinopyroxenites preserve inclusions of hydrous phases and alkali silicate minerals including: amphiboles, chlorites, micas and feldspars. Amphibole, biotite and apatite inclusions in garnet have a high concentration of halogens; CO2 and sulfur are involved in carbonates and sulfide inclusions, respectively. The inclusion patterns and compositional zoning in garnet in combination with textural relations among minerals, suggest that the ultramafic and mafic bodies are derived from lithospheric mantle above the subduction zone and were transformed into garnet pyroxenites and eclogites in the subduction zone. Based on compositional, mineral and textural relations, all of these rocks along with the surrounding crustal material were overprinted by granulite facies metamorphism during their exhumation. [Copyright &y& Elsevier]

Abstract: Mélanges have been reported from a variety of modern tectonic settings and are a hallmark of the Franciscan-type subduction–accretion complexes. In the Precambrian, however, well documented examples of mélanges become extremely scarce. This paper describes in detail Neoproterozoic to early Cambrian mélanges recently recognized in the Cadomian basement of the Teplá–Barrandian unit, Bohemian Massif. The mélanges are of sedimentary and tectonic origin and include voluminous successions of graywackes interpreted to represent mass-transport deposits presumably along the upper slope of an accretionary wedge. The clast compositions indicate multiple episodes of mixing of terrigenous arc-derived and deep-water (?pelagic) material. Moreover, abundant bodies of (meta-)basalts, interpreted as dismembered seamounts or pillow volcanoes, were emplaced tectonically into various structural levels of this sedimentary mélange by two different mechanisms. At an upper level, the irregular to elongated bodies of basalts were offscraped, only weakly strained, and incorporated in the sedimentary matrix that exhibits steep cleavage indicating horizontal pure shear shortening and oblate strain. In contrast, at a lower level, disc-shaped and closely spaced basalt bodies are ductilely sheared and reworked into a flat-lying prolate to plane-strain fabric suggesting horizontal ductile flow, presumably along the base of the accretionary wedge during flat-slab oceanic subduction. Our new U–Pb ages also reveal that the mélange formation continued until the early Cambrian (<527Ma). We conclude that these sedimentary–tectonic mélanges and the inferred mélange-forming processes are identical to those that operate along modern active plate margins and, in general, reveal their potential as excellent markers for establishing modern-style subduction in Precambrian settings. [Copyright &y& Elsevier]

Abstract: Standard and spectral gamma-ray (GRS) logs are widely used as indicators of facies in the subsurface. In siliciclastics, however, the gamma-ray signal is often influenced by changes in the provenance of the K, U and Th-bearing detrital minerals. In this paper, we have compared outcrop and laboratory GRS with modal and chemical sandstone and mudstone composition and facies in an approximately 2.5km-thick siliciclastic turbidite system of the Moravo-Silesian Culm Basin (Lower Carboniferous), Czech Republic. The aim was to separate the facies signal from the detrital provenance one. The siliciclastics have moderately high outcrop gamma-ray values (174 API on average) and slightly lower laboratory values (127 API). Both the outcrop and laboratory data show low sensitivity to facies, which is demonstrated by the low contrast between the K, U and Th concentrations in the seven facies types ranging from proximal to distal turbidites. Markedly higher GRS variability is observed between equivalent facies at different stratigraphic levels. Major carriers of the GRS signal include K-feldspars, muscovite, sericite, biotite and albite for K, zircon, apatite, monazite and xenotime for U and monazite, thorite, REE secondary minerals, xenotime, apatite and zircon for Th. With the effect of facies filtered out, the GRS values reveal a stratigraphic variability, which coincide with the changes in the sandstone modal composition. A shift from the low-grade metamorphic and volcano-sedimentary provenance to predominantly magmatic sources with ultrapotassic plutonites in the early Late Viséan is associated with a marked increase in U and Th concentrations and generally higher sandstone radioactivity compared to mudstones. Another provenance shift to high-grade metamorphic sources with granulites in the latest Viséan is associated with a rapid decrease in Th, U and partly K concentrations and an increase in the GRS contrast between sandstone and mudstone facies. The GRS data sensitively reflect the extremely rapid exhumation of mid-crustal and deep-crustal rocks in the major source area, the Moldanubian Zone of the Bohemian Massif. [Copyright &y& Elsevier]

Abstract: This paper provides evidence for recent geodynamic activity within the Sudeten and Krušné Hory Mts. Fault Zones of the Bohemian Massif, Central Europe. Data were recorded using crack gauges and tiltmeters located on specific geological structures within caves and galleries. These data are supported by rangefinder, seismic, and groundwater observations. It is shown that a significant pressure phenomenon, here termed a pressure pulse, occurred during 2003. The pressure pulse initiated a series of tectonic deformations. In the Krušné Hory Mts., the pulse was preceded by chaotic tilt movements followed by significant tilt reorientation. Several stages of the deformation process were determined, analysed, and described. These stages represent stability, relaxation, compression, compaction, and later relaxation. The pressure pulse itself was associated with the compressional stage. Moderate, but regionally significant, earthquakes occurred during the later stages of the deformation process. This precludes the idea that they might be responsible for the initiating the recognised movements. At the same time, an unusual sequence of earthquake micro-swarms occurred in West Bohemia. These events should all be seen as the result of tectonic deformation initiated by the pressure pulse. Supplementary data indicate an affinity between the deformation process and large global disturbance within the Earth''s crust (). [Copyright &y& Elsevier]

Abstract: This paper presents the results of two separate geophysical investigations undertaken across the Sudetic Marginal Fault zone in the Bohemian Massif. This fault zone represents one of the most important tectonic features in central Europe. The first, preliminary, investigation used electrical resistivity tomography (ERT) to define the exact position of the main fault at two localities (Kamenička & Bílá Voda). Both profiles revealed a resistivity gradient that divided a complex of crystalline rocks with high resistivities from sedimentary deposits with low resistivities. From these data, sites were selected for palaeoseismic trenching. This trenching provided detailed information regarding the surveyed structures and lithologies. The second, more extensive, investigation used electrical resistivity tomography and gravimetric survey in order to extend the previously recognised features both laterally and to depth. The fault is displayed by the presence of an expressive resistivity gradient, even on profiles undertaken in more homogeneous lithologies. Finally, the most intensive investigations were conducted at Bílá Voda, where highly detailed ERT was undertaken on the floor of the trench. From this, it was possible to trace approximately logged geological structures to far greater depths and assess sedimentary thicknesses. A gravimetric survey was also undertaken adjacent to the trench. From modelling the gravitational effects of the fault zone, it is shown that the fault dips about 75° NE and that the vertical offset of Miocene vs. bedrock on the fault is approximately 200m. The presented study has demonstrated the value of undertaking two phases of geophysical exploration separated by a trenching investigation. It is considered that this methodology is particularly suitable for the study of active tectonics in analogous intraplate settings where fault slip-rate is low. [Copyright &y& Elsevier]