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The taxonomy of the soft-shell turtle Rafetus bohemicus (Liebus, 1930), family Trionychidae, subfamily Trionychinae, is revised based on new and previously mentioned material (including the type material) from the Early Miocene (Burdigalian, MN 3) sites of the Most Basin, Czechia. Given that the diagnosis was so far based only on plastral elements, here we focused on the cranial material and combined our study with previously published data on postcranial elements. 3D models of the skulls derived from CT scans allow us to provide the first complete skull description of R. bohemicus, including several new cranial diagnostic characters of the species. Our results not only enable the distinction of the trionychid genera Trionyx and Rafetus, both recorded from Central Europe during the Early Miocene, but further allow us to provide an emended diagnosis for R. bohemicus. We confirm the conclusions of a previous study according to which Trionyx pontanus, T. preschenensis, T. aspidiformis, and T. elongatus are nomina dubia. R. bohemicus from Břešt'any (MN 3) represents the oldest record of this genus in Europe as well as the oldest occurrence of the genus. [ABSTRACT FROM AUTHOR]

The taxonomy of the soft-shell turtle Rafetus bohemicus (Liebus, 1930), family Trionychidae, subfamily Trionychinae, is revised based on new and previously mentioned material (including the type material) from the Early Miocene (Burdigalian, MN 3) sites of the Most Basin, Czechia. Given that the diagnosis was so far based only on plastral elements, here we focused on the cranial material and combined our study with previously published data on postcranial elements. 3D models of the skulls derived from CT scans allow us to provide the first complete skull description of R. bohemicus, including several new cranial diagnostic characters of the species. Our results not only enable the distinction of the trionychid genera Trionyx and Rafetus, both recorded from Central Europe during the Early Miocene, but further allow us to provide an emended diagnosis for R. bohemicus. We confirm the conclusions of a previous study according to which Trionyx pontanus, T. preschenensis, T. aspidiformis, and T. elongatus are nomina dubia. R. bohemicus from Břešt’any (MN 3) represents the oldest record of this genus in Europe as well as the oldest occurrence of the genus.

We describe the occurrence and possible origin of rare beds 1–10cm thick and containing 20–70% of crandallite, a Ca-Al phosphate enriched in Sr and Ba, found within otherwise monotonous clay-rich lacustrine sediments of the Most Basin in the Central-European Neogene Ohře Rift system. The beds were formed at ca. 17.31, 17.06, and 16.88Ma, while the entire suite of monotonous clays of the Libkovice Member was deposited between 17.46 and 16.65Ma. Trace-element and organic geochemistry, Ar-Ar geochronology and C-O-Sr isotope systematics are used to infer their source and processes leading to their formation. The most enigmatic aspect of the formation of the crandallite beds is the removal of a huge amount of phosphorus from its biogenic cycle in the lacustrine system, which was otherwise stable for ca. 0.8My. Formation of detritus-poor crandallite beds could result from some exceptional environmental disruptions that hindered transport of fine clastic material to the basin floor. Silicic volcanic activity in the area of the Pannonian Basin could have triggered this disruption. Crandallite could provide evidence of long-lasting droughts and acidification of the exogenic environment, as they are roughly coeval with the onset of the Miocene Climatic Optimum at ca. 17.0Ma.

Trace elements are a natural part of the environment; however, anthropogenic activities can significantly contribute to their abundance and mobility in the environment. This study is focused on trace element mobility in sediments of a river system (the Bílina River, Czech Republic) affected by coal mining. It follows the previous research of trace element mobility in lignite from the Main Coal Seam in Bílina Quarry (Cahová et al. 2019). Eight samples of river sediment were taken along the Bílina River flow to evaluate the changes in As, Cr, Ni and V contents. Sequential extraction analysis modified according to Querol et al. (1996) and Feng et al. (2000) was used to determine the mobility of the studied elements under conditions close to natural. The amount of studied elements contained in each extract was determined by inductively coupled plasma mass spectrometry (ICP-MS). Water-extractable species of toxic elements may pose a risk to the environment due to their high mobility and bioavailability. It has been found that the release of compounds from the river sediment into the environment is conditioned by acidic conditions. While total metal contents in the river sediment ranges from tens to hundreds of J^g/g, the amounts of metals extracted in each extraction step (deionised water and 1 M ammonium acetate at pH 5 and 7), typically reaches only tens to hundreds of ng/g, therefore the amount of easily mobilized elements is minimal. [ABSTRACT FROM AUTHOR]

Based on a fossil fruit from the early Miocene strata of the Most Basin in Northern Bohemia (Czech Republic), a new species of the genus Halesia L. of the family Styracaceae is described as Halesia mosbruggeri Kvaček, sp. nov. The fossil occurrence of this genus, which today shows a disjunct distribution, adds a further evidence for the ancient connection between North America and Eurasia during the Neogene. [ABSTRACT FROM AUTHOR]

We describe the occurrence and possible origin of rare beds 1-10cm thick and containing 20-70% of crandallite, a Ca-Al phosphate enriched in Sr and Ba, found within otherwise monotonous clay-rich lacustrine sediments of the Most Basin in the Central-European Neogene Ohře Rift system. The beds were formed at ca. 17.31, 17.06, and 16.88Ma, while the entire suite of monotonous clays of the Libkovice Member was deposited between 17.46 and 16.65Ma. Trace-element and organic geochemistry, Ar-Ar geochronology and C-O-Sr isotope systematics are used to infer their source and processes leading to their formation. The most enigmatic aspect of the formation of the crandallite beds is the removal of a huge amount of phosphorus from its biogenic cycle in the lacustrine system, which was otherwise stable for ca. 0.8My. Formation of detritus-poor crandallite beds could result from some exceptional environmental disruptions that hindered transport of fine clastic material to the basin floor. Silicic volcanic activity in the area of the Pannonian Basin could have triggered this disruption. Crandallite could provide evidence of long-lasting droughts and acidification of the exogenic environment, as they are roughly coeval with the onset of the Miocene Climatic Optimum at ca. 17.0Ma. [ABSTRACT FROM AUTHOR]

Three new early Miocene fossiliferous horizons were found in the Libouš Mine near Chomutov in the Most Basin. The Libkovice Member of the Most Formation was originally considered as devoid of fossils, apart from rare findings in drillcores. The new fossiliferous horizons within lacustrine clay sediments can be precisely dated (17.0-17.3 Ma) thanks to their position close to the phosphate-bearing horizons C1-C3 (Fig. 2, 3), which allow a broad correlation across the Most Basin (Fig. 1). Newly recognized floras are characterized by common early Miocene representatives of Betulaceae, Myricaceae, Ulmaceae, Aceraceae, Rhamnaceae, Cupresaceae and Pinaceae known from the Most Basin, with possible indication of a warming trend towards the upper fossiliferous/crandallite horizon documented by the presence of thermophilic elements such as Cedrelospermum sp., Bumelia oreadum and Leguminosae gen. et. sp. indet (Fig. 4). This possible warming trend in the upper part of the Libkovice Member represents the beginning of the Middle Miocene Climatic Optimum, which was confirmed by previous researches. The vegetation analysis distinguished several plant assemblages of azonal riparian forest, mixed swamp forest, and zonal mesophytic evergreen broadleaved forest mixed with pine stands. The results of the Integrated Plant Record vegetation analysis demonstrate, that the vegetation corresponds to the Mixed Mesophytic Forest vegetation type with a close affinity to the living plant assemblage of Fagus crenata growing on Mt. Fuji in Japan. [ABSTRACT FROM AUTHOR]

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Copyright of Zpravoday Hnede Uhli is the property of Brown Coal Research Institute, j.s.c. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Zpravoday Hnede Uhli is the property of Brown Coal Research Institute, j.s.c. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Most Basin represents a coal basin with a long mining history in the Czech Republic. The majority of palaeo-environmental and geochemical studies have been focused on the upper part of the coal-bearing Most Formation where the coal is generally enriched in As, Cr, Ni, Cu and Zn. This study evaluated the distribution of V, Cr, Ni, Cu, Zn, Pb, Se, As, and Mn from the lower part. Regarding to the transport of inorganic elements into environment, the evaluation of mobility potential was also conducted. The total of 51 samples were collected from the Lower Bench in the Holešice Member. The chemical analyses were performed together with optical microscopy. The X-ray spectroscopy and ICP-MS were used to detect trace element contents in the study set of samples. 4 samples were subjected to the Sequential Extraction Procedure. The prepared leachates were analysed using the ICP-MS method. In total, 13 elements were screened in samples within the study profile. The mode of occurrence is the key factor for identifying a potential source of the trace elements. All evaluated trace elements (V, Cr, Ni, Cu, Zn, Pb, Se, As and Mn) leached most in the oxidisable fraction. On the other hand, As, Mn, Ni, Zn and Cd leached in more mobile fractions, e.g. reducible and acid. [ABSTRACT FROM AUTHOR]

Copyright of Zpravoday Hnede Uhli is the property of Brown Coal Research Institute, j.s.c. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The material of Machichnus regularis and Machichnus multilineatus was re-examined with respect to the potential tracemaker. New characters were defined for M. multilineatus - scratch profile with flat horizontal bottom and undulated microrelief of scratches. Based on these characters and additional information, both previously suggested tracemakers (beavers and porcupines) are rejected and a new one - a large squirrel is proposed. The squirrel origin of gnawing traces is additionally supported by actuopalaeontologic study on gnawing behaviour of recent red squirrels. On this basis, squirrels are recognized as overlooked but important taphonomic agents in Late Cenozoic assemblages. The tracemaker of M. regularis was not unambiguously recognized, but a connection with smaller squirrel or aplodontid species seems probable. [ABSTRACT FROM AUTHOR]

An extensive collection of nearly 4200 fossil plants remains from lower Miocene deposits at Bílina and Břešťany were examined for signs of damage caused by arthropods. Determining the frequency and diversity of plant–arthropod interactions was the main objective, followed by a comparison of the level of damage to plant taxa for which there were at least 25 specimens. There were significant differences in the frequencies of the damage caused by the different functional feeding groups in the whole assemblage and individual taxa. Comparison of the diversity of the different types of damage by rarefying their five occurrences also confirmed the differences in the levels attained. The highest diversity was recorded for deciduous trees ( Alnus , Nyssa and Populus ). The organisms that caused some of the highly specific types of damage, such as mining and oviposition, were taxonomically identified on the basis of their unique morphological traits. There was one remarkable non-herbivore plant–arthropod interaction represented by a solitary record of a caddisfly case built exclusively of Taxodium needles. [ABSTRACT FROM AUTHOR]

Thirty samples of the lacustrine sediments from three localities of the Most Basin including coal samples were studied by petrological and organic geochemical methods. The consistent results indicate the relatively stable surface development of the sediments in the environment of the Holešice, Lom and Osek Members. Biological material with contribution of microbial activity participated in the storing, which led to the formation of clayey coal. In the results of the chemical composition dominated sesqui-, diand triterpene compounds. Completely different sediments of Libkovice Member contained low proportions of small organic particles dispersed in the sediment. In the extracts of these samples prevailed hopanes, perylene and sulphur after the action of microorganisms. The base of the organic fraction also formed remains of terrestrial plants and liptinite macerals, especially alginite, liptodetrinite and bituminite that are typical for lacustrine sediments. [ABSTRACT FROM AUTHOR]

The objective of the present study was to determine the trace element contents in the lower and upper benches of the main coal seam (Holešice Member) in the Most Basin. The contents of all analyzed elements were compared to Clarke values for coals. Fifty coal samples from the lower bench and ten samples from the upper bench were collected in the Bílina open cast mine in the Most Basin. Contents of the following trace elements: As, V, Ni, Cu, Zn, Pb were determined in collected samples using the X-ray fluorescence method (XRF). The chemical and technological parameters such as ash yield and calorific value, total sulphur, total carbon, nitrogen, hydrogen, were measured. All results are presented in relevant figures as a median. Results of technological parameters proved the coal seam of the upper bench to be classified as a low-rank coal according to the International Classification ECE-UN (1998). Based on the ash content, calorific value, and the content of major organic elements (S, N, H, C), the samples of the upper bench are classified as lignite, while samples from the lower bench as coaly claystone according to the ash yield up to 50 wt.% (Fig. 1). The coal claystone contained an increased amount of all observed trace elements, vanadium in particular. Clarke values for brown coal and all coals determined by Ketris and Yudovich (2009) are significantly lower compared to the median of element contents given for the upper and lower benches of the main coal seam. The results further show clearly that contents of As, V, Ni, Cu, Zn, and Pb are higher in the lower bench compared to the upper bench. The high variability in concentrations of the analyzed elements prevents to establish their actual contents. There was no significant correlation between total carbon and vanadium content found in analyzed samples (Fig. 2). A marked correlation between As and Sd was observed only in the lower bench (Fig. 3). [ABSTRACT FROM AUTHOR]

We present a critical evaluation of the Early Miocene terrestrial and aquatic mollusc fauna of the North Bohemian Lake in the Most Basin in the Czech Republic. In total, 90 species (8 aquatic and 81 terrestrial gastropods, one bivalve) are documented from that lake system that had formed within the North Bohemian Rift. Only three of these species are newly recorded for the Most Basin, suggesting that the fauna is well sampled. Based on historical collections of the Natural History Museum in Vienna, which were partly acquired by quantitative bulk samples from Tuchořice, a rough estimate of the composition of the terrestrial assemblage can be presented. More than 80% of the >30,400 shells are represented by carychiids, vertiginids and valloniids, suggesting the presence of densely forested wetlands fringing the North Bohemian Lake. About 57% of the terrestrial species are known so far exclusively from the Most Basin. This high degree of "endemism", however, is rather a result of the still very fragmentary knowledge of coeval European faunas. Discus rasseri Harzhauser, Neubauer & Georgopoulou sp. nov. and Discus zagorseki Harzhauser, Neubauer & Georgopoulou sp. nov. are described as new species and Esuinella Harzhauser, Neubauer & Georgopoulou gen. nov. (Valloniidae), Nordsieckula Harl & Harzhauser gen. nov. (Orculidae), and Manganellia Harzhauser, Neubauer & Georgopoulou gen. nov. (Discidae) are introduced as new genera. Serrulastra (Serruplica) tuchoricensis nom. nov. is proposed as replacement name for Clausilia laevigata Frankenberger, 1914. [ABSTRACT FROM AUTHOR]

Copyright of Paläontologische Zeitschrift is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Six sediment cores from two of four depocentres in the Most Basin, mostly consisting of macro fossil barren fluviodeltaic and lacustrine sediments of Holešice and Libkovice members of the Most Formation (lower Miocene, Burdigalian) were subjected to chemostratigraphic correlation, based on CEC and EDXRF proxy element analyses. CEC-step, prominent K/Al minima and crandallite-bearing horizons in monotonous lacustrine mudstones of the Libkovice Member provide several local isochronous or nearly isochronous key horizons, which we propose for a basin-scale correlation of the upper Most Basin sediment fill. These key horizons prove a spatially uniform sedimentary environment in a single lake (original area ~1,000 km²) during deposition of a considerable part of the siliciclastics overlying the main coal seam that tops the lower basin fill. We propose the CEC-step horizon as a novel boundary between Holešice and Libkovice mem¬bers, i.e. the conversion of previously formal lithostratigraphic units to members with an isochronous boundary. That boundary together with recent sedimentological studies would assign Břešťany clay to the top of the Holešice Member. The upper boundary of the Libkovice Member could be the sediment coarsening related to a lake level decrease before deposition of Lom coal seam. The study will allow progress in palaeogeographic and palaeoenviromental reconstruction of the lower Miocene in the Most Basin. The proxy analyses (CEC vs Al/Si ratios) allow reliable numeric differentiation between kaolinite-rich, smectite-poor and smectite-rich clay assemblages in Holešice and Libkovice members. The plots of CEC vs Al/Si ratios should be applicable for fingerprinting any other monotonous lacustrine clastics with variable mineralogy of the clay assemblage. [ABSTRACT FROM AUTHOR]

Abstract: Numerous coalified tree stumps remained preserved in-situ in the so-called “Stump Horizon” (the palaeontologic horizon No. 31), which represents clayey overburden of the main coal seam in the Bílina open cast mine in the Most Basin (Czech Republic). The petrological and chemical composition, palaeobotanical origin and preservation of 24 selected tree stumps were studied by optical and scanning electron microscopy and gas chromatography–mass spectrometry (GC–MS). Composition of the fossil wood is dominated by ulminite, particularly texto-ulminite B. Textinite forms up to 38vol.% in the decomposed tree stumps. Corpohuminite dominates in bark and root tissues. Partly gelified and deformed woody tissues contain both corpohuminite and resinite fillings. Random reflectance of ulminite ranges from 0.33% to 0.39% and carbon content from 49wt.% to 78wt.%. Samples represent pure woody material with small admixtures of clay minerals, siderite, and very rare pyrite. Observations by scanning electron microscopy revealed various levels of deformed secondary xylem with more or less swollen cell walls, conspicuous tracheids, uniseriate rays of a different height, and round or cylinder-like resin or corpohuminite bodies. According to our results and other published data the wood might belong to Glyptostroboxylon and Taxodioxylon genera that are supposed to belong to Glyptostrobus and Quasisequoia plants respectively, representatives of the coniferous family Cupressaceae. The biomarker composition in the extracts of the fossil wood includes sesquiterpenoids (α-cedrane, drimane, eudesmane), diterpenoids (abietane, fichtelite, 16α(H)-phyllocladane) and their degraded compounds. The terpenoids are derived from precursors produced by the source plants and microorganisms. The terpenoid signatures support a relationship to the Cupressaceae family with input of microbial species. These characteristics were identical for all studied samples. Significant variations have been observed in sesquiterpenoid α-cedrane and diterpenoid 16α(H)-phyllocladane contents. [Copyright &y& Elsevier]

Abstract: A detailed study of more than 4000 plant macrofossils from the lower Miocene of the Most Basin (localities Bílina Mine and Břešťany) in northern Bohemia has been made in order to implement quantitative and taxonomic analyses of gall occurrences. Fourteen distinct arthropods were identified as possible causers of fossil galls. Similarities in the form, size and position on the host-plant leaves allowed identifications at least to the generic level and to discuss their relationships to extant gall-inducing species that cause morphologically similar galls on related host-plant species. The fossil galls were induced by members belonging to the following insect and mite families: Psyllidae (Hemiptera), Cecidomyiidae (Diptera), Cynipidae (Hymenoptera) and Eriophyidae (Acari). Galls on Taxodium induced by gall midges of the genus Taxodiomyia (Diptera: Cecidomyiidae) are recorded for the first time. All here described galls are the first records of fossil galls from the Neogene of the Central Europe and complement the view plant–insect interactions during the lower Miocene. The Bílina Mine collection comprises material from several fossiliferous layers representing also different ecosystem types. The presence of elevated gall frequency in the Lake Clayey Horizon (LCH) accompanied by the lower diversity of the other damage types implies colder and drier habitat with unevenly distributed rainfall in comparison with Delta Sandy Horizon (DSH). [Copyright &y& Elsevier]

Abstract: Exposures in the Bílina opencast mine provide a direct evidence that the 3.5m thick upper bench of the Main Seam in the Most Basin passes over a distance of about a kilometre into a hundred metres thick equivalent of clastic deltaic sediments with Gilbert-type mouth bars and thus clearly corroborates the co-existence of lacustrine delta–mire system. Deposition of the delta and the upper bench of the Main Seam were affected by five short-term lacustrine incursions, possibly related to tectonic subsidence before final lacustrine transgression took place. Between the temporary lacustrine incursions, delta mouth bars prograded into an extensive mire being separated only by a shallow compaction lake along mouth bars foreland. However, most clastics, introduced from delta were caught by dense vegetation in a narrow proximal zone of mire and did not affect more distal parts of relatively dry woodland mire with water table fluctuating around the surface. It is therefore characterised by low ash yield and increased resinite, fusinite and inertodetrinite contents. Palynological data indicate that the peat-forming vegetation of the upper bench of the Main Seam was dominated by Taxodiaceae (Glyptostrobus, Athrotaxis) and Calamus palm accompanied by paludal species of the family Pinaceae and rich undergrowth of ferns and Vaccinium-type Ericaceae. Progradation of delta mouth bars to the proximity of the study section is documented by increasing proportion of allochthonous elements produced by plants colonizing the flood plain and delta plain areas (Nyssa–Taxodium, Parrotia–Ulmus pyramidalis and Comptonia–Pinus oviformis associations). In contrast, during periods of temporary lacustrine transgressions the mire was replaced by open water environment, which favoured deposition of clay-rich coals or partings (>30% of ash yield) of the flooding horizons in spite of fact that delta body retreated to the basin margin and the clastics were introduced from a larger distance. Rare palynomorphs indicate only sparse vegetation cover of aquatic plants during this time. Clay content seems to be the best indicator of the water level fluctuations. Facies indices (e.g. TPI and GI) show only poor correlation to hydrological and floristic changes detected in the mire–lake system. [Copyright &y& Elsevier]

Abstract: Terrestrial plants and insects account for the majority of the Earth''s biodiversity today, and herbivorous interactions are dated back more than 400 million yr. However, investigation of their associations remains in its infancy in Europe. The Miocene is characterized by palaeogeographic re-organization due to the collision of the African with the Eurasian plates. Antarctica''s enormous impact on global climatic conditions, and thus on European palaeoenvironment, resulted from a series of episodes of minor glaciations in the Early Miocene after the initial cooling and ice sheet formed during the Oligocene. More than 3500 plant remains showing various kinds of feeding damage were available for the present study. These trace fossils are classified according to their external morphology into damage types (DT) and grouped to functional feeding-groups. The Neogene plant record in Europe is rich and diverse, offering a profound large-scale understanding of the floristic and vegetational development. A database of fossil traces from the Most Basin was compiled and analyzed by various statistical methods in terms of the diversity and intensity of palaeoherbivory. The primary objective is to present results on the development of insect herbivory through the section of the Bílina Mine in North Bohemia, with the aim of understanding the principal factors that caused the observed phenomena. The research was focused on two horizons—Delta Sandy Horizon (DSH) and Lake Clayey Horizon (LCH)—both sufficiently represented to compare their palaeoecological and palaeoclimatological signals on the basis of the presence of damages caused by insects and other herbivorous arthropods. A total sample of 60 different damage types, attributed to eight main functional feeding groups, was examined. Results from analyses of the frequency and diversity of the selected categories of plant arthropod associations within both examined horizons significantly support different environmental conditions. The LCH seems to be affected by the relatively colder and drier climatic conditions as indicated by a four times greater frequency of leaves with galls and lower taxonomic diversity and species equability, whereas DSH indicates warmer and more humid conditions reflecting the higher diversity of the plant species and damage types. [Copyright &y& Elsevier]

Rare aluminium hydroxo-sulphate, felsöbányaite, Al4(SO4)(OH)10·4H4O, was found at two occurrences in the Most Basin (northern Bohemia, Czech Republic). It forms white earthy and powdery aggregates filling gaps and cracks in coal matrix in the Libouš Quarry, Březno near Chomutov. Unit-cell parameters of the Libouš sample refined from the X-ray powder diffraction data are: a 13.056(5), b 10.126(5), c 11.101(4) Å, β 103.90(4) and V 1424(1) Å3. At the Bílina quarry felsöbányaite occurs as hemispherical to spherical aggregates formed by tiny tabular crystals with a size of 2 - 5 μm in clay and carbonates. Unit-cell parameters of the Bílina sample refined from the X-ray powder diffraction data are: a 13.024(8), b 10.011(3), c 11.113(7) Å, β 104.34(5) and V 1404(1) Å3. Felsöbányaite is formed at studied occurrences by reaction of sulphate anions (from weathering of Fe-sulphides) with alumosilicates from clay rocks within coal seams. [ABSTRACT FROM AUTHOR]

Porcellanite is a term conventionally used for multicoloured jasper-like rocks, formed from clays by pyrometamorphism. In the territory of the Most Basin, however, all pyrometamorphic rocks produced by natural fossil combustion of a Neogene coal seam are traditionally marked by the term „porcellanites". The Most Basin (also known as the North Bohemian brown-coal Basin) is situated in the northwest of the Czech Republic and with the annual production of ca 50 millions metric tons of brown coal represents the main energy source of the Czech Republic. The previous authors mentioned 65 localities of combustion pyrometamorphic rocks scattered in the region of the Most Basin in the territory of about 1400 km². The pyrometamorphic complexes form flat-lying or shallow-dipping deposits and they have size ranging from several hundreds metres up to several kilometres and the thickness varying from several metres up to about 35 m. This paper brings mostly unpublished data on mineralogy of pyrometamorphic rocks formed from thermally altered carbonates present in a subordinate amount in a sedimentary sequence. These rocks studied in detail represent buchites, slags and paralavas which are strongly different from typical glassy porcellanites; the main differences comprise coarse-grained structure, chemical composition, presence of more or less macroscopic mineral phases, and frequently high magnetic susceptibilities (10-1- 10-2 SI). Most common mineral assemblages formed from siderite contain olivine + magnetite + anorthite ± orthopyroxene or sekaninaite + tridymite + fayalite + Ti-hercynite. Aggregates of massive magnesioferrite accompanied by hematite were locally found. Most exotic assemblages are hosted by Si-undersaturated calcareous paralava from the Želénky porcellanite deposit. This rock is characterized by high concentrations of Ca and Fe, moderate Mg, and low Si, Al and alkalis. High temperatures (experimentally 980-1150 °C or even higher) with high oxygen fugacity accompanied with extremely high concentrations of Fe2O3 and CaO and lackof silicon resulted in crystallization of esseneite, melilites rich in gehlenite and ferrigeh-lenite components, kirschsteinite, variety of spinels including magnesioferrite, three ferrites (srebrodolskite, unnamed CaFe4O7, and barium hexaferrite BaFe12O19) and some additional phases. In pyrometamorphic rocks of the Most Basin nearly 50 minerals and unnamed phases were identified till now: anatase, anhydrite, ankerite, apatite, aragonite, barite, calcite, celsian, chalcopyrite, cordierite, corrundum, cristobalite, diopside, esseneite, fayalite, forsterite, garnet, goe-thite, Ca-graftonite, gypsum, hematite, hercynite, ilmenite, K-feldspar, kirschsteinite, metakaolinite, maghemite, magnesioferrite, magnetite, melilites, monazite, mullite, orthopyroxene, perovskite, plagioclase, pyrite, quartz, sekaninaite, sillimanite?, spinel, srebrodolskite, tridymite, calcium silicate - Ca2SiO4, calcium ferrite - CaFe4O7, barium hexaferrite - BaFe12O19, and several poorly identified phases. [ABSTRACT FROM AUTHOR]

Both yellow and white whewellite from the Most Basin (brown coal basin of Neogene age in the NW of Czech Republic) is strongly fluorescent and phosphorescent in long-wave ultraviolet light. Whewellite crystals display in UVA light intense green-yellow fluorescence (wavelength 366 nm) and subsequent phosphorescence (green-yellow glow) which is observable at least 15 - 20 seconds after irradiation. Less pronounced phosphorescence is observable also after the irradiation by UVC light (wavelength 254 nm) and even after the illumination by common artificial light. Whewellite from the Kladno Coal Basin (also Czech Republic) is not luminescent. Chemical composition and lattice parameters of both luminescent whewellite from the Most Basin and non-luminescent from the Kladno Basin are nearly identical. [ABSTRACT FROM AUTHOR]