Zr-Nb-REE-Y mineralization consisting of aeschynite-(Y), fergusonite-(Y), monazite-(Ce), synchysite-(Ce), bastnäsite-(Ce) and zircon has been identified in the area of the SEDEX-type sulphide Pb-Zn-Ag ore deposit near Oskava in the southern part of the Vrbno Group (NE part of the Bohemian Massif ). These REEminerals occur together with zircon in hydrothermally altered acid metatuffs. Hydrothermal alteration is mainly manifested by albitization, sericitization and carbonatization. Zr-Nb-REE-Y mineralization is present mainly in rocks with relatively high muscovite content in the bedrock and overburden of the sulphide ore zone. In typical cases, REE mineral and zircon grains are concentrated in muscovite-rich bands that are part of acid metatuffs (Fig. 2 to 7). An identical association of REEminerals and zircon was also found in sulphide samples from the ore zone. The sulphide ores usually have a distinctive banded structure with bands up to several cm thick consisting mainly of sphalerite, with less abundant pyrite, galena, chalcopyrite, arsenopyrite and other ore minerals (Fig. 1). However, the acid metatuffs in the ore zone have a low muscovite content and their Zr-Nb-REE-Y mineralization is very poor compared to the muscovite-rich acid metatuffs in its bedrock and overburden. At the Oskava sulphide deposit, Zr-Nb-REE-Y mineralization has also been identified in hydrothermally altered volcanic rocks (quartz alkali-feldspar trachyte, alkali-feldspar rhyolite). The results of representative WDX analyses of all REEminerals listed above are presented in Tables 1 to 3. Within the Bohemian Massif, this is a new type of mineralization. The EU countries classify the resources of REE as critical raw materials, some even as strategic raw materials. Nevertheless, the described mineralization is probably presently of no economic significance due to the low REE, Y, Nb and Zr grades. The occurrence of Zr-Nb-REE-Y mineralization at Oskava indicates that a possible source of these elements could be the products of Devonian acid volcanism in the Vrbno Group.
Current paleomagnetic investigations in the Most Basin are unique among the recent studies as the number of explored localities and samples, and use of up-to-date equipment concerns. Extensive lacustrine and fluvio-deltaic deposits overlying the Main Coal Seam (Most Formation, Lower Miocene) are the subject of the research. This article summarises the main results of investigations in magnetostratigraphy and rock magnetism in context with other related disciplines since 2014. So far, magnetostratigraphic analysis has been carried out on the following boreholes 70–380 m deep from both central and marginal parts of the basin: SP269 (Spořice), HK591, HK772 and HK930 (the former Hrdlovka village), HD50 (Háj u Duchcova), A24 (Srbice u Teplic), ZU5A (Chabařovice), LB432 (the former Libkovice village), OS17 (Osek), DO565 (Droužkovice), AL505 (the former Albrechtice village), DU7 (Dubí u Teplic), JU2183 (the former Jenišův Újezd village), MR93 (Mariánské Radčice), ZL70 (Litvínov-Záluží), and RL8 (the former Růžodol village). In terms of magnetostratigraphy, we demonstrate that a local lake was present in the Bílina area from the end of paleomagnetic chron C5Dr.2r through chron C5Dr.1n to the beginning of the C5Dr.1r chrons (Holešice Member). The progradation of the Bílina Delta took place during the end of C5Dr.2r and its rapid development occurred mainly during the C5Dr.1n subchron. The coalescence of small local lakes began in the C5Dr.2r subchron and early in the C5Dr.1r chron culminated in the formation of a large basin- wide lake. Substantial changes occurred at the Holešice/Libkovice boundary near the C5Dr.1r/C5Dn reversal when hydrology of the basin-wide lake changed. The sediments of the Libkovice Member were deposited over a period of ca. 1.0 million years during C5Dn, C5Cr, and C5Cn.3n chrons. The beginning of the Miocene Climatic Optimum is also dated to this period. In the Lom Member sediments, geomagnetic polarity was not measurable; the C5Cn.2r/ C5Cn.2n reversal was thus not recovered, and most of C5Cn.2n was missing in the record. The youngest lithostratigraphic unit in which geomagnetic polarity has been measured is the Osek Member with sediments of the second basin-wide lake. Here, the Most Basin record ends at C5Cn.1n chron in the uppermost part of the Burdigalian. This comprehensive magnetostratigraphic framework allows for chronological understanding for the basin evolution from small isolated lakes to a major basin-wide system, terminating about 15.9 million years ago. Note that, in magnetostratigraphic studies, identification of sedimentary magnetic carriers is crucial for ensuring the reliability of paleomagnetic records. However, our understanding of this issue remained limited until the recent study of the RL8 core. The findings indicate that the magnetic carriers in the studied section consist of a mixture of diagenetic greigite and biogenic magnetite, implying that the paleomagnetic age is younger than the sediment itself. This discovery should be considered in the chronostratigraphic framework of the Most Basin. Yet, the character of magnetic carriers in the cores from different parts of the basin remains an open question. The objective of this multidisciplinary research of the Most Basin is not only to make the stratigraphic scale significantly more accurate, but also to acquire better knowledge of paleogeography and environmental changes during Miocene.
The paper informs about the discovery of a new locality with fauna and flora Kochov “U jasanu” belonging to the Kochov lake horizon (Letovice Formation, Boskovice Graben). The outcrop includes, among other beds, a layer of bituminous limestone overlain by a layer of laminated bituminous gray limestone with a high clay content. A rich vertebrate fauna occurs in both beds (Beds No. 4 and 5 on Fig. 1A, C). The limestone layer contains skeletons of amphibians of the genus Discosauriscus and actinopterygian fish of the genus Paramblypterus. The overlying laminated bituminous limestone is notable for the abundance of fish of the genus Paramblypterus, while discosauriscid amphibians are absent. The representation of the fauna in these two fossiliferous beds clearly coincides with the occurrence of fauna in other outcrops of the so called Kochov Horizon in the vicinity of Kochov and Drválovice (Fig. 1B). The agreement between these layers is enhanced by their almost equal thickness and the presence of thin layers of tuffitic material. The newly discovered locality, together with the other outcrops of the Kochov Horizon, demonstrates the relatively considerable extent of the Kochov Lake. This sedimentary basin had an area of at least 3.5 km2. The outcrops of the so called Bačov Horizon lying to the south contain the same fauna as the outcrops of the Kochov Horizon, and the thicknesses of the fossiliferous layers are almost identical. This suggests that both horizons could be deposited simultaneously and made part of a single basin.
This is the first description of a rare mineral baddeleyite (ZrO2) closely associated with gem quality zircon from the Jizerka alluvial placer in the Jizerské hory Mts., a well-known source of sapphire and zircon (variety “hyacinth”) since medieval times. Baddeleyite occurs in cavities at Jizerka zircon rims in form of clusters of skeletal crystals and isolated symplectitic intergrowths with former quartz. Baddeleyite symplectitic textures provide evidence for a partial dissolution of the Jizerka zircon in basaltic lava during volcanic eruption and fast ascent to the Earth´s surface. The width of only up to 30 μm of the remnants of the baddeleyite coronas around the zircon xenocrysts indicates a short residence time of the Jizerka zircons in the sub-crustal magma chambers at temperatures higher than the closure of the U-Pb system in zircon (> 900 °C) and may also reflect resetting of their age to the age of the host alkaline basalt. Preservation of the corona also indicates the short transport of zircon from the volcanic source to the Jizerka stream. Coincidence in composition of the baddeleyite from the Jizerka zircon and those in kimberlite zircons rims indicates at least some similarities in the conditions of their origin, such as high temperature and fast transport to the surface. The primary host rocks of the gemstones (sapphire and zircon) and abundant Mg-ilmenite (“iserine”) in the Jizerka alluvial placer are not well constrained, but most likely could be related to the cluster of alkali basalt extrusions conducted in the close vicinity.
During the construction of the Příbor bypass road (2009– 2011), a body of volcanic rocks belonging to the Teschenite Association (Fig. 2), enveloped by the Lower Cretaceous (upper Barremian) sediments, was uncovered on the western edge of the city. The rocks are unaltered to strongly altered picritic rocks near the thrust plane. Completely altered hyaloclastites, or hyaloclastite breccias, were also recognized. These rocks are smectitized (montmorillonite-saponite), carbonatized, and impregnated with pyrite and marcasite. Anatase, baryte, palygorskite, and quartz are accessory phases. The findings of xenocrysts of Cr-rich oxyspinelides as well as calcite pseudomorphs after olivine in the weathered zone provide evidence for the affiliation of hyaloclastites to picritic rocks. Further excavation work near the roundabout (Fig. 1, GPS coordinates N 49° 38.417’ E 018° 07.745’) in 2017 uncovered in these rocks blocks of carbonate material up to 15 × 15 × 25 cm in size. The carbonate material makes fillings of cavities in the hyaloclastite breccia. Their oldest mineral is pyrite that forms fibrous aggregates (sunflower microtexture) up to several centimeters long (Fig. 3) composed of pyrite framboids overgrown by tabular pyrite (Fig. 4). The pyrite aggregates are covered by an older generation of calcite resembling speleothems (stalactites) with a distinctly concentric structure. The spaces between the stalactites are filled by younger white coarse-grained crystalline calcite, in places within cavities (Fig. 3). The isotopically very light sulfur in pyrite with the sunflower microtexture (δ34S −39.9 ‰ CDT) indicates its bacterial origin at anoxic conditions. The aggregates probably represent the original strings of chemotrophic bacteria colonies. Isotopic signature of six calcite samples (δ13C down to −45.6 ‰ V-PDB, δ18O 26.7–30.6 ‰ V-SMOW) demonstrates their cold (hydrocarbon) seep origin (Tab. 1, Fig. 5). These seeps were probably thermally induced by the ascending magma and its extrusion onto the seabed. A similar formation was previously documented for the carbonate from the Baška locality (δ13C up to −28.3 ‰ V-PDB), where it is bound to pillow lavas of the Teschenite Association Rocks. Worldwide, the thermogenic methane seeps triggered by active volcanism are known, but usually not associated with the formation of seep carbonates.
Samples of recently formed secondary sulphates from the site known since the mid-19th century as Nezabudické skály (e.g., Feistmantel 1856) were studied (Fig. 1–3). The site is situated in the Berounka valley, near the village of Nezabudice in the Rakovník district, and lies in the Křivoklátsko Protected Landscape Area (GPS 50° 01’ 23.22” N; 013° 50’ 21.66” E). The samples were taken from places where the schists and graywackes of Neoproterozoic age contain inserts of black pyritised graphitic schists, usually strongly weathered, and where water occasionally flows or seeps. Here, sulphates form efflorescences directly on the walls, or thicker crusts under overhangs, where mineralised water drips. The most abundant is gypsum, forming hard grape-like crusts composed of small colourless crystals. Very brittle, fibrous, dry, powdery, white crusts and deposits were identified as hexahydrite with a small admixture of epsomite and gypsum. These very brittle, white aggregates of Mg-salts are mostly formed separately from the gypsum crusts. At the foot of the wall, brittle, grey-white aggregates of alunogen with slavíkite and earthy, yellow crusts of magnesiocopiapite, up to several cm thick, are formed (see Fig 4–5). X-ray diffraction data were obtained on a Bruker D8 Advance powder diffractometer; CuKα radiation and a position- sensitive Lynx Eye XE detector were used. To verify the chemical composition, the samples were studied on a Jeol 6490LV electron microscope under the following conditions: accelerating voltage 15 kV, electron beam current 1 nA, and working distance 15 mm. The chemical composition was determined using an INCA Act-X energy- dispersive detector (EDX) (Oxford Instruments). Abundant alunogen, sometimes intergrown with yellow copiapite on the surface of the aggregates, forms soft when wet, brittle when dry, grey or yellowish crusts, up to several cm thick. After drying, the crusts form brittle, strongly porous aggregates composed of intergrown, colourless, thin alunogen plates, several tenths of a millimetre in size. Only Al and S were detected chemically, the calculated lattice parameters for the space group P1– are: a = 7.4258(8) Å, b = 26.951(1) Å, c = 6.0571(8) Å, α = 89.99(1)°, β = 97.55(1)°, γ = 91.87(1)°, V = 1201.1(1) Å3, and Z = 2. Groups of clear alunogen tables are covered in places by inconspicuous, pale yellow-green microcrystalline aggregates of slavíkite in the deeper parts of the crust. Aggregates of slavíkite are also composed of hexagonal tabular crystals, but only 5–10 μm in size (Fig. 5a–c). The partial empirical formula of slavíkite is Mg4.47Al1.37Fe13.91(SO4)21. The calculated lattice parameters of slavíkite for the space group R3– are: a = 12.1883(2) Å, c = 34.955(4) Å, V = 4497.0(6) Å3, and Z = 1. Magnesiocopiapite mostly occurs separately as earthy sulphur-yellow nodules and forms distinctly elongated, parallel-growing hexagonal tables, 20–40 μm in length (Fig. 5d). An indicative analysis on an EDX detector would reveal a minor content of Mg in addition to dominant Fe and S. The calculated lattice parameters of magnesiocopiapite for space group P1– are: a = 7.348(1) Å, b = 18.770(2) Å, c = 7.394(1) Å, α = 91.36(1)°, β = 102.16(1)°, γ = 98.86(1)°, and V = 983.4(2) Å3. Other sulphates identified via XRD that were studied in more detail are halotrichite- pickeringite, hexahydrite, epsomite, and gypsum.
Detailed documentation of extensive outcrops of the Vršany Mine (Early Miocene, Most Basin) near the town of Most during 2014–2022 made possible to compile a detailed geological section of an important structure that was formerly known only from boreholes. The structure that is up to 3 kilometres long and several hundred meters wide is characterized by sudden interruption of the coal seam and its replacement by clastic sediments, while the seam is thickened at its edges. The newly documented section allowed for discussion of its formation. Documented sudden facies transitions within the structure fill, the presence of one prominent fault plane along which coarser clastic sediments accumulated, divergence of layers, significant deformation of the lower part of the sediment infill as well as the displaced parts of coal seam clearly demonstrate that the deformation structures result from the interaction of clastic sediment of the Žatec delta deposition and loading of peat layers. The distinctive structure in the Vršany Mine was caused by synsedimentary burial of clastic sediments into only partly compressed peat along a growth fault gradually prograding in the direction of the paleoflow. The missing parts of the seam were apparently moved along the growth fault to the eastern edge of the structure. This caused thickening of this part of the seam by its lateral compaction and displacement of the seam slivers from the area of the seamless zone.
The aim of this study was to quantify groundwater inflows into Kamenice River in its part flowing through the Bohemian Switzerland National Park using thermometry. In particular, the 10-kilometer section from the confluence of Chřibská Kamenice with Kamenice to the confluence of the Kamenice and Elbe rivers was measured. Temperature and electric conductivity were measured on 11.–12. 12. 2022 during low water levels along 41 profiles in total. Conductivity measurements were used for evaluation of the groundwater inflows, as the contrast between the Kamenice River (240 μS/cm upstream, 193 μS/cm downstream) and the groundwater inflows (about 80 μS/cm) was higher than that between the temperature (Kamenice River about 4 °C, tributaries about 8 °C). The yield of groundwater inflows was calculated using mixing equations. For the Kamenice River and surface tributaries and visible springs, the measured value of conductivity was used, and for hidden subaqueous inflows, approximate conductivity value of 80 μS/cm was considered. The river discharge of 1060 l/s was determined from the limnigraph at the beginning of the measured section below the Chřibská Kamenice and Kamenice rivers confluence. Discharge of 1580 l/s was calculated by cumulative adding of inflows for the end of the measured section. This value is rather close to the discharge of 1650 l/s, measured by the Czech Hydrometeorological Institute in Hřensko on 12. 12. 2022. Total inflow in the measured section was estimated at about 500 l/s. Out of this, about 100 l/s are contributed by the Jetřichovická Bělá Stream (and possibly springs around its mouth), about 35 l/s come from the Suchá Bělá Stream, and the remaining about 380 l/s are from smaller subsurface and surface tributaries. The highest inflows were noted in sections 6200–6900 m (70 l/s), 3400–4200 m (50 l/s), and in the inaccessible section 4200–5100 m (80 l/s). Since the surface tributaries (springs and small streams) had typically a low discharge (first l/s), the most of the inflow into the Kamenice River appears to be represented by hidden inflows from pores and small fractures in sandstone. This study demonstrated that thermometry is a rapid and effective tool for both locating and characterizing groundwater inflows in the Bohemian Cretaceous Basin.
The west Bohemian region hosts globally unique CO₂-rich mineral waters associated with Cenozoic intra-plate volcanism and major tectonic structures, including the Mariánské Lázně Fault. While principal balneological sources are state-protected, which requires monitoring of their chemistry, numerous locally used smaller springs within the Slavkovský les (Protected Landscape Area) lack systematic hydrogeochemical characterization. This study addresses this critical knowledge gap through a comprehensive hydrogeological investigation. We have mapped and conducted detailed physicochemical analyses of 178 mineral springs across a 955.7 km² study area. The results demonstrate a direct lithological control on water chemistry. Based on cluster analysis, the springs were classified into five distinct hydrochemical facies: (1) Mg-HCO₃ type, unequivocally linked to serpentinite weathering; (2) Ca-HCO₃ type, associated with amphibolite terrains; (3) high-TDS Na-HCO₃/SO₄ type (“Karlovy Vary type”), resulting from deep circulation with potential interaction with residual Miocene brines; (4) transitional Ca-Na-HCO₃ facies; and (5) probably anthropogenically influenced springs with molar Na-Cl ratio 0.6–1.2. Temporal monitoring of representative springs revealed significant chemical stability, indicating well-buffered systems largely resilient to seasonal hydrological changes. The majority of springs exhibited pristine quality, with nitrate concentrations consistently below the 0.1 mg/l detection limit. This research provides the first systematic hydrogeochemical inventory of the Slavkovský les after more than 60 years. It establishes a critical scientific baseline for the implementation of evidence-based protection strategies and underscores the necessity of extending this systematic evaluation to adjacent, uncharacterized regions.
Craniid brachiopods are generally rare in Silurian and Devonian rocks. Correspondingly, only few taxonomic works focused on this group, with a rare exception of Holmer et al. (2018) review from the Silurian of Gotland. Recently, several shells of a so far unknown craniid brachiopod have been observed in the Požáry stratotype section, Czech Republic. The shells represent the first observed craniids of Silurian age in the Prague Basin. All specimens come from the Požáry stratotype locality in Prague Řeporyje (Kříž 1999). In the section above the tunnel portal, layers of weathered sparitic limestone (the so called “white beds”) of the Kopanina Formation (Ludfordian) crop out near the base of the rock wall. This part of the exposure corresponds to the upper part of the Ananaspis fecunda horizon (Kříž 1999). In the lowest weathered layer about 20 cm thick (Fig. 1) a rich brachiopod and crinoid fauna was found. The fossil assemblage is dominated by small to mediumsized brachiopods Lissatrypa fumida, Gracianella plicumbra, Cyrtia postera, Jarovathyris canaliculata, Cadudium sphaerulites, Metaplasia sp., Dayia sp. and Salopina sp. In addition to brachiopods, trilobites Otarion diffractum, Ananaspis fecunda, calyces and pluricolumnals of microcrinoids, isolated plates of machaeridians, gastropod shells, and other small fossils are abundant. Craniid brachiopods are generally rare, representing less than 1% of the total brachiopod fauna. The described specimens are characterized by a small dorsal valve, having a broadly trapezoid to pyriform outline, wellmarked anterocentral apex, and prominent concentric growth bands. By contrast to muscle scars that are not preserved, the porosity of the shell wall is well marked. Although valves are rather poorly preserved, in their outline and the macroornament are similar to shells of Urbicrania limbata (nomen nudum). Havlíček and Vaněk (1998) figured this and other similar species from the DvorceProkop and Řeporyje limestones (Lower Devoinian, Pragian) in the Prague Basin, but without the formal description.
Sandstone caves are usually an unfavourable environment for the preservation of gastropod shells and vertebrate bones in Quaternary sediments. The cause of unfavourable taphonomic conditions in sedimentary fills is most often low pH, which leads to the dissolution of fossils. However, there are exceptions to this rule. Here we report on the discovery of Quaternary sediments rich in calcareous fossils that we have made in Otto Mörtzsch Cave (Labské pískovce Protected Landscape Area, Czechia). This site is one of the deepest crevice-type caves (−40 m) in the Elbe River Canyon, the largest European sandstone canyon located at the border between Czechia and Germany (Fig. 1). The good preservation of the gastropod shells and vertebrate bones found (Fig. 2) is probably due to the presence of secondary carbonates (speleothems) on the cave walls and their erosion and deposition together with the fossils (Figs 2, 3, 4). The original source of calcium carbonate was likely loess, which was deposited above the cave during the Last Pleniglacial and later degraded. Radiocarbon (14C) dating results (Table 1) show that the natural archive represented by the sedimentary sequence studied reflects environmental changes in the Elbe River Canyon during the Early and Middle Holocene (Northgrippian and Greenlandian), when the sandstone landscape was not yet strongly affected by natural acidification. The acidification process later caused decalcification and oligotrophication of soils and a subsequent decline in acid- sensitive fauna and flora. This fact is also evidenced by the gastropod fauna we found, dominated by species associated with mixed forest environment (Fig. 2), and by dated charcoal from oak (Quercus) and hazel (Corylus) trees (Table 1). Results of 14C dating further indicate that Otto Mörtzsch Cave was formed at the beginning of the Holocene at the latest. The natural archive in Otto Mörtzsch Cave is unique, and further research may significantly deepen our knowledge of the Holocene environmental history of the Labské pískovce (Elbe Sandstones) Protected Landscape Area and the nearby České Švýcarsko (Bohemian Switzerland) National Park.
A new set of disarticulated skeletal elements of brittle stars from Upper Turonian hemipelagic sediments from the Úpohlavy Quarry was discovered recently. This new material helped to extend our knowledge of the systematics and to specify quantitative proportions of individual taxa. The first study of ophiuroids from this locality was already carried out by Štorc and Žítt (2008). Ten species are documented, pertaining to the orders of Ophiurida, Amphilepidida and Ophiacanthida. Another three species are probably present but their systematic position could not be determined due to the poor state of their preservation. The most frequent species are Ophiotitanos serrata, Ophiopeza? nekvasilovae, Ophiolepis cf. pulchra, Ophioderma substriatum and probably also Ophiojagtus cf. alternatus. Less common species are Amphilimna? plana and Manfredura sp. nov. On the other hand, Ophiodoris senonensis, Ophiotreta aff. striata and Ophiomusa sp. nov. are rare in the studied assemblage. Finally, the probable palaeoecology of ophiuroids is discussed.
In the vicinity of the town of Louny, founded in the 13th century, silicified spiculitic marlstone (“opuka“ in Czech) as well as the overlying grey-green glauconitic sandstone about 3 m thick have been exploited in numerous quarries since the Middle Ages. The “opuka“ and sandstone belong to the Bílá Hora Formation of the Bohemian Cretaceous Basin and are of Lower Turonian age. The quarry workers used to call the sandstone in Czech “Malnický řasák” or just “řasák“ (grey-green, mottled stone near the village of Malnice) and this term was also used in Czech geological literature. This paper focuses on the petrographic character of the „řasák“ and its use both in the historic centre of Louny and in the new districts from the 19th and 20th centuries. The rock material was studied macroscopically and in the case of abandoned quarries and several objects and a pavement also microscopically in thin section. The “řasák“ is a strongly silicified, medium to coarse-grained or non-uniformly grained glauconitic sandstone with admixture of micrite and with bioclasts, predominantly monaxonic and desmoid spicules of siliceous sponges, to a lesser extent foraminifera or bivalves. The “řasák“ is heavily bioturbated, with the sand fraction decreasing below 25% in the subordinate parts of the rock which are classified as glauconitic, sandy silicite. The defensive wall around Louny, whose construction began in the 15th century, represents one of the oldest structures where „řasák“ was used. “Řasák“ can be also found on other buildings from the 16th–20th century, e.g. in walls around churches, on water towers or in the retaining walls. From the second half of the 19th century until the 1930s, it was mainly used on the plinths of dwellings, public buildings, family houses and villas or on the plinths and walls around restored Gothic churches. Renowned Czech architects, among others J. Mocker, K. Hilbert and J. Kotěra, used the “řasák“ as a decorative element, thanks to its colour and the possibility of carving it into blocks and variously shaped pieces. The pedestals of “„řasák“ also contribute to the architectural qualities of the Kotěra Colony, completed in 1913 and conceived as a garden city. This colony is the oldest in the Czech Republic and one of the oldest on the European continent.
Shale of the Šárka Formation (lower and middle Darriwilian) containing siliceous nodules, so-called “Šárka balls”, were excavated in a temporary outcrop at the building site in Praha – Horní Měcholupy in the 1980s. The studied nodules yielded a fossil association typical of the Euorthisina-Placoparia Community (or assemblage according to some authors). It is dominated by rhynchonelliform brachiopod Euorthisina moesta, trilobite Placoparia cambriensis, molluscs, especially gastropods and bellerophontids, and hyoliths. Other discovered taxa are represented by a few or single specimens. Unexpectedly, this also concerns ostracod Conchoprimitia osekensis that is otherwise very common. The scarcity of ostracods, low diversity of trilobites, and even absence of stylophoran echinoderms and rhynchonelliform brachiopod Eodalmanella socialis, that are abundant at most localities of the “Šárka balls”, reflect a collecting (sampling) bias rather than a typical feature of this site. However, the find represents a unique record of the fossils of the Šárka Formation from this part of Prague where is a very low chance to discover other material due to the densely built-up area.
Early Cretaceous brittle stars (ophiuroids) have not been systematically studied in the territory of the Czech Republic yet. The studied fauna comes from three thick limestone bodies in the immediate proximity of the town of Štramberk. Most localities with ophiuroid finds (Fig. 1) belong to the Kopřivnice Formation of Late Valanginian age (sensu Houša 1976) in the Kotouč Quarry (localities 6, 20 and 25), in the Obecní Quarry (locality 3) and in the lower Blücher Quarry (locality 1). Locality 2 in the Obecní Quarry pertains to the Hradiště Formation according to Svobodová et al. (2011), being of Hauterivian and Barremian age. The herein preliminarily described material was gathered from old rock samples, tentative old rock washings and sets of Štramberk Early Cretaceous fossils collected and studied in the 1960s–1980s. During many years of research, only three hundred disarticulated skeletal elements of brittle stars have been found here. They are therefore extremely rare in the Štramberk area. Several assemblages of ophiuroid ossicles from the Kopřivnice Formation contain only arm vertebrae. As suggested by the wide morphological variety of the vertebrae, the presence of many species now lacking a closer systematic classification can be expected here. However, the assemblage from the Hradiště Formation (Obecní Quarry, locality 2) contains taxonomically important lateral arm plates, which enabled the study of ophuiroid diversity. Here, the dominant genera are Ophiotitanos (Ophiodermatina) and Squamophis? (Euryalidae). On the other hand, taxa Ophiomusa sp. (Ophiomusaidae), Dermocoma sp. (Ophiodermatina) and Ophiacanthina fam. et gen. indet. are rare. As concerns the drawings by Mauric Remeš (1902), it is evident that his specimens were only two fragmentary vertebrae, but due to the poor state of preservation, they cannot be assigned to any taxon. The places of deposition of these specimens are not known today. As far as palaeoecology concerns, we cannot determine why Ophiotitanos was so abundant in Štramberk (especially in the Hradiště Formation) and what type of food it preferred. The occurrence of Squamophis? in the Kopřivnice and Hradiště Formations points to at least partly similar living conditions in a wider area, their survival for a prolonged time interval (Late Valanginian, Hauterivian, Barremian) or the re-establishment of the necessary living conditions. These euryalids are able to attach to objects rising above the bottom, spread their arms into the water current and feed on zooplankton. Fauna from the Obecní Quarry, locality 2, is very different from the ophiuroid assemblages of the Aptian of Cuchía (Spain) and Wizard Way (Texas) (Thuy et al. 2014) but is very similar to the fauna from the Barremian of Serre de Bleyton (France; Thuy – Kroh 2011). Fauna from Blake Nose (Aptian and Albian, Atlantic Ocean off Florida; Thuy et al. 2012, Thuy 2013) also bears some resemblance to the aforementioned ophiuroid assemblage. It is also remarkable that, much like the localities of the nearshore depositional environments of the Bohemian Cretaceous Basin (Upper Cenomanian and Lower Turonian) (e.g., Štorc 1997), the assemblage from the Hradiště Formation comprises euryalids, ophiomusaids and ophiacanthins, with Ophiotitanos being the most frequent taxon.
The rocks of the teschenite association form smaller scattered occurrences in the upper part of the Hradiště Formation of the Silesian Unit. The teschenite association represents a relatively heterogeneous group of ultrabasic to intermediate igneous rocks with variable amount of felsic and mafic minerals. The age of the igneous rocks corresponds to the Berriasian–Barremian. Three outcrops of the Hradiště Formation with igneous intrusions has been studied in the bed of the Kopřivnička Stream and its tributaries, south of the Town of Kopřivnice (Fig. 1). The area of Červený kámen, Pískovna and Holý vrch elevations is mainly formed by the Baška Facies (calcareous sandstones and conglomerates) of the Silesian Unit. The KOP5 section was studied in more detail (Fig. 2). In the section, contact metamorphosed sediments were found both in the footwall and in the hanging wall of a magmatic rock, which therefore represents an intrusive body. In the contact metamorphosed sediments, recrystallization of carbonates was observed (Fig. 3c), resulting in impure sandy marbles, which are usually dark in colour. Igneous rock is accompanied by a mottled and banded shale. The volcanic intrusive rock and the sandy marble layer approx. 1–2 m above it show a very high content of potassium feldspar (mainly sanidine). The explanation of such a high potassium feldspar accumulation in the sediments is equivocal. According to SEM observations, the potassium feldspar is primarily of clastic origin. However, its formation by metasomatic replacement of plagioclase cannot be ruled out. Based on the structure and mineral assemblage, the igneous rock from the studied profile can be classified as altered alkaline lamprophyre, i.e. fourchite (olivine-free monchiquite). Well-preserved dinoflagellate cysts Aptea anaphrissa, Circulodinium distinctum, Cribroperidinium orthoceras, Kiokansium polypes, Odontochitina operculata, Oligosphaeridium poculum, Prolixosphaeridium parvispinum, Subtilisphaera perlucida were retrieved from the associated claystones. According to the determined dinoflagellate, sediments of the Hradiště Formation in the Kopřivnička stream are of the Upper Barremian to the Lower Aptian age. The organic facies corresponds to a dysoxic environment in the deeper shelf (palynomorphs are dominated by dinoflagellates). Most of the samples are thermally affected by the associated volcanic intrusion.
Geological borehole 4310_02W at Valy nad Labem yielded 145 meters of the core that sampled Upper Cenomanian to Middle Turonian sediments of the Bohemian Cretaceous Basin. These sediments are represented by the Peruc–Korycany, Bílá Hora and Jizera Formations, overlaying the metamorphosed Ordovician basement. Here we describe in detail distinct lithologies and macrofaunal content of these strata. The same stratigraphic range was confirmed by calcareous nannofossil assemblages correlated with UC4b-UC5a, UC6b, UC7 and UC8a zones (sensu Burnett 1998) and by studies of foraminifera belonging to zones Gavelinella cenomanica, Lingulogavelinella – Gavelinella belorussica and Fursenkoina tegulata, respectively.
The formation of ice crystals that leave imprints in the underlying substrate is a well-known phenomenon from current observation and laboratory experiments (Häntzschel 1935, Reineck 1955, Van Loon 1990). According to these studies, ice crystal imprints form at subfreezing temperatures at the sediment-air interface in a water-saturated fine-grained substrate. Observation of ice crystal imprints is particularly relevant to tidally affected sea beaches, riverbanks and rainwater ponds. Both natural and artificial ice crystal imprints show a wide variety of shapes. There is no difference between structures from marine and freshwater environments on a macroscopic scale. As far as is known, the morphology of recent ice crystal imprints depends mainly on the grain size of the host substrate, its water saturation and the freezing temperature or the number of repeated freeze-thaw cycles (Allan 1926, Mark 1932, Häntzschel 1935, Mikuláš 2010). It is evident that imprints of ice crystal imprints (usually their pseudomorphs, to be more precise) can pass into the fossil record with a similar probability as, for example, traces of the activity of organisms. Nevertheless, adequately described findings of pseudomorphs after ice in the geologic record are extremely rare; recently it is mainly the work of Voigt et al. (2021). During a routine inspection of the Medalův Mlýn site (Fig. 1), known as the best and easily accessible outcrop of the so-called Paseky Shale (Cambrian Series 2; see below), I found structures that I tentatively identified as imprints of ice crystals. The imprints (Fig. 2A, B) were found on a single shale fragment (imprint and counterprint) taken from the disintegrating surface of the outcrop within the layer marked on the profile (Fig. 1). The shale fragment is siltstone, with grains hardly visible to the naked eye, with a small proportion of mica, light brown in color. The thickness of the split shale plate was 12 mm. Twelve isosceles triangular formations are visible on the plate, interpreted as pseudomorphs after ice crystals. The shape of the isosceles triangles is characterized by the apex angle, which ranges from 20 to 28° in the pseudomorphs from the Paseky Shale. The length of the triangles is 3–9 mm, the width is 2.5–3.7 mm. All triangles are arranged in a 38 mm long cluster. Six of them form a star-like cluster. Four are situated next to one another and facing a similar direction (± 20°). The remaining two appear to be randomly placed and oriented; one is in an area densely covered by the other pseudomorphs, the other is somewhat apart. Conspicuous circular imprints with a diameter of 1.2 or 1.5 mm occur at the tips of one of the clusters and one solitary triangle. About 50 cm higher in the profile, a layer with abundant microbial coatings (microbially-induced sedimentary structures, MISS) occurs (Fig. 4). Evidence of subfreezing temperatures at the sediment-air interface in the water-saturated fine-grained substrate in the upper part of the Paseky Shale indicates a very shallow-water origin of the deposits, including the occasional emergence of the bottom. Combined with the occurrence of MISS, it is clear that microbial communities were occasionally exposed to a terrestrial environment, which may have affected their ability to survive in a wet, but only exceptionally flooded, environment for a long time. It is remarkable as well that the arthropod community of the Paseky Shale could have been exposed to frost (including possible freezing of the water surface). In the future, all this knowledge acquired individually can represent a valuable basis for considerations about the development of the settlement of brackish and fresh waters and about the evolutionary adaptations of the groups of biota present at that time.
The occurrence of asteroids in the Bohemian Cretaceous Basin is very limited. Their truly abundant occurrence is known only from the Upper Cenomanian and Lower Turonian strata of the so- called surf facies (e.g., the localities of Skalka near Velim, Kamajka, etc.). However, without exception, these occurrences (together with other fauna) consist only of isolated elements accumulated after the complete disintegration of the asteroid skeletons. The principal factor limiting the preservation of asteroid is their complicated skeleton consisting of many articulated elements. The muscular and ligamentary articulations between them decompose easily, which causes complete post-mortem destruction of the skeletons. Therefore, more complete individuals of asteroids are rare, and their preservation necessitates specific conditions. A nearly complete specimen has recently been found at Radouč locality in the town of Mladá Boleslav in Central Bohemia. The rock exposure is formed by medium-grained calcareous sandstone passing upwards to coarse- grained calcareous sandstone of the uppermost part of the Jizera Formation (apparently the Mytiloides labiatoidiformis inoceramid zone and the Subprionocyclus neptuni ammonite zone of the Upper Turonian). These levels correspond lithostratigraphically to the lower part of the Teplice Formation in the western part of the Bohemian Cretaceous Basin. The asteroid individual is rather well preserved. However, the detailed surface sculpture of the marginal parts seems to be damaged, probably by dissolution during diagenesis of the sediments. The preservation of the overall shape of the skeleton of the individual indicates its rapid post-mortem burial, probably with the dorsal side facing upwards. Only the distal parts of 2 arms have rapidly disintegrated at the site of its final deposition (Figs. 3a–c). The individual reaches the size of approximately 9 cm in the radial–interradial direction. It has relatively long and narrow arms with more than half of the supramarginal parts of each arm in dorsal contact. At the same time, there is a corresponding reduction in the disc size. The arrangement and the character of small disc elements are strongly disturbed by post-mortem decay. In conclusion, taxonomic determination of the find as Nymphaster sp. (Family Goniasteridae) can be tentatively considered. To refine it, richer material is needed. The described asteroid is deposited in the collections of the Chlupáč Museum, Faculty of Science, Charles University, Prague, No. CHMHZ MS 2892.
This article focuses on the historical development, current state, and future perspectives of geology education in the Czech Republic. The theoretical part of the article presents analysis of the evolution of the geology curriculum and its position within the Czech educational system. It highlights significant personalities and events in geological sciences and describes the changes in geology education since the 18th century to the present. The empirical part of the article employs qualitative research through focus group interviews to reflect on current approaches to geology education in lower secondary schools (ISCED 2). The respondents included ninth-grade students from primary schools, teacher education students at the Faculty of Science of Charles University, and science teachers. Based on their statements, SWOT analyses were created to identify the strengths, weaknesses, opportunities, and threats associated with geology education. Strengths include practical field exercises and field trips that provide students a direct contact with geological materials and demonstrate interdisciplinary connections between geology, chemistry, physics, and geography. Weaknesses involve low student interest, lack of teaching aids, and the complexity of integrating geology into other subjects. Threats include low teacher motivation and inadequate resources in school natural science collections, while opportunities lie in tandem teaching and collaboration with research and educational institutions. The article emphasizes the need to strengthen interdisciplinary connections, increase teacher support and motivation through further education, and improve school collection. Emphasis is also placed on popularizing geology to make it more attractive not only to students but also to the broader public. Overall, it is essential for geology education to respond to current challenges and trends, thus contributing to the formation of comprehensive scientific education that will inspire students to further study and interest in natural sciences.
