The middle and upper Lochkovian (Lower Devonian) conodont successions in key peri‐Gondwana localities (Spanish Central Pyrenees and Prague Synform) and their relevance for global correlations

Detailed correlation, based on conodont sequences, between middle and upper Lochkovian carbonate successions from two key peri‐Gondwanan regions, the Spanish Central Pyrenees and the Prague Synform, is attained for the first time. This correlation facilitates the definition of tie points for further multidisciplinary studies that seek to establish high‐resolution temporal subdivision and global correlation. Some intervals have a precision of less than 0.5 Ma, which is significantly greater than in previous studies. The estimated elapsed time considered herein is about 3.2 Ma and is subdivided into five major zones of global scope: transitans‐trigonicus, trigonicus‐kutscheri, kutscheri‐pandora β, pandora β‐gilberti and gilberti‐steinachensis β. By providing tie points and globally applicable criteria, this research contributes to the international cooperative effort to subdivide the Devonian standard stages into globally recognised substages.     

Devonian graptolites from southwestern Europe: a review with new data

Lower Devonian graptolite faunas have been recognized in the Normandy and southeastern regions of the Armorican Massif, France; the Pyrenees and Catalonian Coastal Ranges regions and northern Minorca, Balearic Islands, Spain; the southern Hesperian Massif (Ossa Morena Zone) of the Iberian Peninsula; and from southeastern Sardinia, Italy. All but one the of the graptolite faunas collected throughout this large region are from Lochkovian age strata, representing the Monograptus uniformis, Monograptus praehercynicus, and Monograptus hercynicus biozones corresponding to the lower, middle and upper Lochkovian, respectively, and mostly represented by monospecific or low diversity assemblages. Although many individual sections contain representatives of two of the biozones, relatively few reveal all three. A single, poorly preserved faunule, collected in the Ossa Morena region of Spain from strata dated by brachiopods as Pragian–early Emsian may represent the only known graptoloid fauna of post-Lochkovian age. Almost all graptolites have been recovered from condensed successions of black shales and limestone nodules, similar to those of other proto-Tethyan (i.e. outer shelf, with dominantly pelagic faunas) regions such as Thuringia, Bohemia, the Carnic Alps and northwestern Africa. The two exceptions are an occurrence in a shallow-water, coarser clastic sequences at the Carteret locality in Normandy and in deep water turbidites on the island of Minorca. Graptolites are not known from any other thick, shallow water clastic sequences, although whether this is because of paleo environmental exclusion or simply lack of recovery to date is unknown. Other fossil evidence (e.g. chitinozoans), however, indicates continuous marine sedimentation from the Silurian to Devonian. © 1996 John Wiley & Sons, Ltd.     

Larger foraminifera distribution and strontium isotope stratigraphy of the La Cova limestones (Coniacian–Santonian, “Serra del Montsec”, Pyrenees, NE Spain)

The Upper Cretaceous La Cova limestones (southern Pyrenees, Spain) host a rich and diverse larger foraminiferal fauna, which represents the first diversification of K-strategists after the mass extinction at the Cenomanian–Turonian boundary.The stratigraphic distribution of the main taxa of larger foraminifera defines two assemblages. The first assemblage is characterised by the first appearance of lacazinids (Pseudolacazina loeblichi) and meandropsinids (Eofallotia simplex), by the large agglutinated Montsechiana montsechiensis, and by several species of complex rotalids (Rotorbinella campaniola, Iberorotalia reicheli, Orbitokhatina wondersmitti and Calcarinella schaubi). The second assemblage is defined by the appearance of Lacazina pyrenaica, Palandrosina taxyae and Martiguesia cyclamminiformis.A late Coniacian-early Santonian age was so far accepted for the La Cova limestones, based on indirect correlation with deep-water facies bearing planktic foraminifers of the Dicarinella concavata zone. Strontium isotope stratigraphy, based on many samples of pristine biotic calcite of rudists and ostreids, indicates that the La Cova limestones span from the early Coniacian to the early-middle Santonian boundary. The first assemblage of larger foraminifera appears very close to the early-middle Coniacian boundary and reaches its full diversity by the middle Coniacian. The originations defining the second assemblage are dated as earliest Santonian: they represent important bioevents to define the Coniacian-Santonian boundary in the shallow-water facies of the South Pyrenean province.By means of the calibration of strontium isotope stratigraphy to the Geological Time Scale, the larger foraminiferal assemblages of the La Cova limestones can be correlated to the standard biozonal scheme of ammonites, planktonic foraminifers and calcareous nannoplankton. This correlation is a first step toward a larger foraminifera standard biozonation for Upper Cretaceous carbonate platform facies.     

Subdivision of the Lochkovian Stage based on conodont faunas from the stratotype area (Prague Synform,Czech Republic)

Relatively rich conodont faunas from sections in the Prague Synform (Barrandian area, Czech Republic) include a number of indexes and other important guide conodonts that can be correlated with other regions, especially with Nevada and the Spanish Central Pyrenees. The collation and detailed correlation of conodont data from the Lochkovian in two parallel sections in the Požáry quarries, together with biostratigraphic control of additional data from several (incomplete) sections with changing facies development, is the basis for a new detailed regional biozonal scale for the Lochkovian in the Prague Synform. The new subdivision follows, with modification, the global threefold conodont subdivision of the Lochkovian. Data from the Prague Synform enable further detailed subdivision of the lower, middle and upper Lochkovian into small‐scale units. The conodont distribution shows a large proportional discrepancy between the late Lochkovian elsewhere; the conodont record in the latest Lochkovian in the Prague Synform area, which appears to be rather restricted and requires further discussion. Copyright © 2012 John Wiley & Sons, Ltd.     

Early Serpukhovian (late Mississippian) microflora from the Guadiato Area (southwestern Spain)

Calcareous microflora occur commonly in the early Serpukhovian (late Mississippian) rocks from the Guadiato Area (southwestern Spain) despite the fact that this area contains mostly siliciclastic sediments. The microflora recorded in the carbonate beds is regarded as representative of both relatively deep‐water and shallow‐water facies and can be compared with the slope and shelf facies environments distinguished in the Guadiato Area. Up to 45 algal taxa have been identified in the carbonate beds, of which 26 taxa occur in the relatively deep‐water assemblages, whereas the shallow‐water assemblages are composed of up to 43 taxa. The entire algal assemblage is dominated by calcifoliids, common cyanobacteria and incertae sedis, but the shallow‐water assemblages contain more commonly dasyclads, red algae and aoujgaliids. Most of these taxa are present, but poorly known, in other Serpukhovian carbonate platforms in the western Palaeotethys. Some algae (Hortonella uttingii, Kamaenella tenuis and Koninckopora inflata), usually regarded as being restricted to the Viséan, have been found in Serpukhovian rocks in the Guadiato Area, and also in Algeria, thus their stratigraphic ranges might be extended up to the Serpukhovian. Other important taxa include: Archaeolithophyllum, Cabrieropora, Calcifolium, Falsocalcifolium, Fourstonella, Frustulata, Kulikia, Neoprincipia and ‘Windsoporella’, which are exceptionally recorded in Serpukhovian rocks, or not recorded at all, because they are typically recorded in the Pennsylvanian (cf. Clavaporella), although some of them show earlier occurrences in Viséan rocks (Claracrusta, Paraepimastopora and Sparaphralysia). Some of the algal taxa can be considered as potential regional markers for the Serpukhovian, such as Archaeolithophyllum, cf. Clavaporella, Frustulata and Girvanella (?) sp. The algal assemblages found in the Guadiato Area show the greatest similarities with those in the Béchar‐Mézarif (Algeria), Pyrenees and Montagne Noire (southern France). Copyright © 2005 John Wiley & Sons, Ltd.     

Valentinagraptus a new genus of plectograptid graptoloid from the lower Ludlow (Silurian) of Barrandian,Bohemia

The new plectograptid—Valentinagraptus simplex gen. nov., sp. nov.,—(Family Retiolitidae) was recovered from the nilssoni and progenitor biozones (early Gorstian, Ludlow) of the Barrandian area of central Bohemia, Czech Republic. The new taxon is characterized by a sub‐oval form and considerably reduced rhabdosome framework. The rhabdosome is similar to Plectograptus, with a simple ancora umbrella with large proximal orifices, but has a simple ancora sleeve with horizontal lateral lists connecting ladder‐like ventral walls. Copyright © 2006 John Wiley & Sons, Ltd.     

Facies development,depositional settings and sequence stratigraphy across the Ordovician–Silurian boundary: a new perspective from the Barrandian area of the Czech Republic

The Hirnantian and Llandovery sedimentary succession of the Barrandian area has been assigned to middle and outer clastic‐shelf depositional settings, respectively. Deposition was influenced by the remote Gondwanan glaciation and subsequent, long‐persisting, post‐glacial anoxia triggered by a current‐driven upwelling system. High‐resolution graptolite stratigraphy, based upon 19 formally defined biozones—largely interval zones—and five subzones, enabled a detailed correlation between 42 surface sections and boreholes, and enabled linking of the sedimentary record, graptoloid fauna dynamics, organic‐content fluctuations and spectral gamma‐ray curves. The Hirnantian and Llandovery succession has been subdivided into four biostratigraphically dated third‐order sequences (units 1–4). Time–spatial facies distribution recorded early and late Hirnantian glacio‐eustatic sea‐level lowstands separated by a remarkable mid‐Hirnantian rise in sea‐level. A major part of the post‐glacial sea‐level rise took place within the late Hirnantian. The highstand of Unit 2 is apparently at the base of the Silurian succession. Short‐term relative sea‐level drawdown and a third‐order sequence boundary followed in the early Rhuddanian upper acuminatus Zone. Early Aeronian and late Telychian sea‐level highstands and late Aeronian drawdown of likely eustatic origin belong to units 3 and 4. Sea‐level rise culminated in the late Telychian, which may also be considered as a highstand episode of a second‐order Hirnantian–early Silurian cycle. Facies and sequence‐stratigraphic analysis supports recent interpretations on nappe structures in the core part of the Ordovician–Middle Devonian Prague Synform of the Barrandian. Copyright © 2006 John Wiley & Sons, Ltd.     

Upper Famennian and Lower Tournaisian sections of the Moravian Karst (Moravo‐Silesian Zone,Czech Republic): a proposed key area for correlation of the conodont and foraminiferal zonations

Foraminiferal and conodont faunas at the Devonian–Carboniferous (D–C) boundary in the southern part of the Moravian Karst (Czech Republic) were studied in different facies of the basin slope. The joint presence of foraminifers and conodonts in calciturbidites along with a positive δ¹³C excursion of the Hangenberg anoxic event enabled the high‐resolution calibration of the late Famennian–early Tournaisian interval (Upper expansa–crenulata conodont zones). The conodont stratigraphic and biofacies succession reveals a strong correlation with other European areas. The Siphonodella sulcata morphotype (close to Group 1 sensu Kaiser and Corradini and “nov. gen. nov. sp. 1” sensu Tragelehn) enters prior to the Hangenberg Event, which resembles Upper and Uppermost Famennian conodont successions from Franconia, Bavaria and Morocco. The diversification of the early siphonodellids takes place after the Hangenberg Event and after the protognathodid radiation. In terms of foraminiferal biostratigraphy, the D–C boundary interval is characterized by the first appearance datum (FAD) of Tournayellina pseudobeata close below the D–C boundary followed by a sequence of Tournaisian bioevents, where apart from the last appearance datums (LADs) of quasiendothyrs, the FADs of the Neoseptaglomospiranella species and chernyshinellids play an important role in a similar manner as in Eastern Europe. The correlation of these bioevents elsewhere is often hindered by glacioeustatically‐driven unconformities and widespread occurrences of unfavourable facies for plurilocular foraminifers (Malevka beds and Bisphaera beds). Copyright © 2013 John Wiley & Sons, Ltd.     

Some late precambrian microfossils from the Bohemian Massif and their correlation

A brief account is given of the main biostratigraphical conclusions resulting from the micropalaeontological study of the Bohemian Upper Proterozoic. The relatively rich microfossil material presently known from the Barrandian area enables comparison to be made both with Middle and Upper Brioverian microfossils of the West European Brioverian complex and also with those from the Upper Riphean and Vendian platform sediments. A correlation between the relatively close geographical areas of Bohemia, Lusatia and Saxony on the basis of microorganisms is evident. Biocommunities from siliceous rocks display algal-mat assemblages. Their features are very similar to those of biogenic rocks reported from other regions, especially Australia and North America. In the Moldanubian Supergroup, the ?eský Krumlov Formation, in which graphitized phytoclasts with anatomical structures of primitive land plants have recently been found, was examined. The question of the age of this formation remains open and its study is still in progress. The correlation of the sedimentary complex of the East Sudeten (the presumably Proterozoic Záb?eh Formation) with the Palaeozoic assemblage is possible due to the finds of Chitinozoa. Remains of megascopic algae were recently found in this assemblage, along with chilinozoan chambers. This association is highly specialized and comprises new taxa of higher Thallophytes.     

Variability of petroleum inclusions in vein, fossil and vug cements—a geochemical study in the Barrandian Basin (Lower Palaeozoic, Czech Republic)

Although no commercial oil or gas occurrences have been found in the Barrandian Basin, residual oils and petroleum inclusions give evidence about the petroleum history of this Lower Palaeozoic Basin. Petroleum inclusions are hosted in six generations of calcite and quartz cements that can be attributed to different stages of a basinal cycle and associated diagenetic events. They were analysed using an on-line crushing and an off-line crush-and-leach approach. Five different groups (PI-A to PI-E) and intermediate mixtures (PI-M) could be differentiated based on the relative distribution of n-alkanes. All oils had a calculated aromatic maturity R_c ranging between 0.9 and 1.6%. PI-A shows a molecular weight maximum in the range of n-C_8–11 with a constant attenuation towards higher carbon numbered n-alkanes. This distribution is interpreted as the pristine precursor oil for other petroleum inclusion groups. PI-B has a maximum weight abundance at n-C_15–20. The genetic relationship between PI-B and PI-A can tentatively be explained by mixing effects or by gas stripping. PI-C is bimodal and characterised by a molecular weight maximum at n-C_32–34, and also a molecular weight maximum at n-C_15–20 similar to that of group PI-B. PI-D shows a normally distributed molecular weight maximum in the range n-C_25–28 and is interpreted as a wax precipitate from ascending gas saturated in n-alkanes. PI-E contains predominantly gaseous compounds with only a few higher hydrocarbons. Thompson's aromaticity values are elevated for condensates of group PI-E, and also for group PI-C that is dominated by long-chained n-alkanes. This gives evidence that fault-bound petroleum migration in the Barrandian Basin was associated with evaporative fractionation for group PI-C and PI-E. Samples of group PI-E yielded gas-range compounds only, and all come from a last generation of vein-filling whitish calcite that was formed in a late uplift phase of the basin. For other petroleum inclusion groups, only a vague preferential occurrence in specific mineralisation phases or stratigraphic intervals of the host rock has been found. This reflects the predominance of fracture-bound migration in the Barrandian Basin. Aromatic maturity values also showed no correlation between either crystal type or PI-group. In six of the investigated petroleum inclusion samples alk-1-enes are present. These terminal olefins are interpreted to be the result of the natural pyrolysis of petroleum due to the intrusion of volcanic dykes or hydrothermal processes. An artificial generation of olefins during sample work-up and analysis is unlikely. The preservation of alk-1-enes from Palaeozoic times was possible due to the protecting environment of petroleum inclusions.     

Solemys (Chelonii,Solemydidae) remains from the Maastrichtian of Pyrenees: evidence for a semi-aquatic lifestyle

We report on a turtle from the Mina Esquirol site (Vallcebre basin), a new locality of early Maastrichtian age in the south-eastern Pyrenees. Fossils were located in the basal Tremp Formation, which was deposited in a littoral marsh. The material consists of a cast of a carapace including peripheral fragments and partial neural plates. The carapace exhibits a vermiculate ornamentation that is characteristic of genus Solemys and a histological bone structure similar to that of terrestrial taxa. However, taphonomic data indicates little transport and a short biostratinomic history, whereas palaeontological and sedimentological context indicates that the specimen was preserved in a shallow brackish water environment. Based on this taphonomic and sedimentological evidence, we suggest that at least some species of genus Solemys had a lifestyle similar to extant fresh or brackish water turtles (terrapins) and that the histological evidence alone for a terrestrial lifestyle is misleading.     

A new species of Mirovia (Coniferales, Miroviaceae) from the Lower Cretaceous of the Iberian Ranges (Spain)

The Lower–Middle Albian coaly clay bed of the Escucha Formation, which is exposed at Rubielos de Mora (eastern Iberian Ranges, Spain), contains a diverse fossil plant assemblage. Among the taxa present in this layer, Mirovia gothanii Gomez sp. nov. differs from other species of the genus by its greater leaf length, margins typically overhanging the depressed stomatal groove, a single short, blunt, papilla borne by each subsidiary cell, non-stomatal cells inside the groove and margins, and a higher number of resin ducts in the mesophyll. Morphological study of the well-preserved cuticles demonstrates that the species also occurs in Lower Cretaceous coals of Santa Maria de Meià (Pyrenees, Spain) where Gothan (1954) described it as Sciadopitytes sp. Both localities constitute the southernmost extent of the genus in Laurasia when the family was likely to have reached its climax in terms of abundance and diversity.     

An unusual theropod track assemblage from the Cretaceous of the Zhucheng area, Shandong Province, China

More than 125 footprints of theropods from the Cretaceous Longwangzhuang Formation have been mapped in a preliminary study at a site in the Zhucheng region of China. The tracks represent at least three morphotypes. The largest morphotype is a large theropod (footprint length ∼30 cm) represented by a single trackway and an isolated natural cast. At least 10 trackways assigned to the new ichnospecies Corpulentapus lilasia represent a medium-sized biped (footprint length ∼13 cm) with very short, wide, robust, ‘tulip-shaped’ tracks and long steps (∼5 × footprint length), and a short central digit (III) indicating weak mesaxony. Corpulentapus trackways are narrow and theropod-like even though track morphology is convergent with the footprints of some ornithopods. The third morphotype, made by a medium-sized grallatorid track maker (ichnogenus Paragrallator), is about the same size (∼13 cm) as the robust morphotype, but far more elongate and gracile, with an elongate central digit (III) indicating strong mesaxony. This ichnotaxon requires detailed comparison with Grallator sensu stricto. The contrast in morphology between the two common morphotypes is striking and demonstrates that two distinct medium-sized taxa of presumed theropod affinity frequented the same habitat in significant numbers.     

Latest Campanian and Maastrichtian Siderolitidae (larger benthic foraminifera) from the Pyrenees (S France and NE Spain)

The siderolitids from the uppermost Campanian and Maastrichtian deposits of the Pyrenees have been re-studied. This has revealed a high diversity and rapid replacement of taxa, confirming the group as a good tool for high resolution biostratigraphy. Two genera have been found in the uppermost Campanian–Maastrichtian interval in the Pyrenean deposits: Siderolites Lamarck, and Wannierina Robles-Salcedo. Siderolites, with canaliferous spines or denticulate periphery, is represented by four species replacing each other from the latest Campanian to Maastrichtian: Siderolites praecalcitrapoides (latest Campanian), S. pyrenaicus sp. nov. (early Maastrichtian), Siderolites calcitrapoides (late Maastrichtian) and Siderolites denticulatus (late Maastrichtian). Wannierina is characterised by well-developed keels and ramified marginal canals. Two species of Wannierina have been identified and they succeeded one another from latest Campanian to early Maastrichtian: Wannierina vilavellensis sp. nov. (latest Campanian) and Wannierina cataluniensis (early Maastrichtian). The species of the genus Siderolites inhabited shallow waters of tropical to subtropical platforms with moderate-to-high water-energy conditions and those of the genus Wannierina are typical of deep–water low-energy environments but still in the eutrophic zone.     

Biostratigraphy,sedimentology and sequence stratigraphy of the Tournaisian–Viséan transitional strata in South China (Guangxi)

The biostratigraphy and sedimentological evolution of the Tournaisian–Viséan (T–V) transitional strata in South China (Guangxi) have been investigated. The sediments were deposited on a carbonate platform and in slope and basinal environments. In the T–V transitional strata, six foraminiferal associations have been distinguished which allow correlation between the shallow and deep water deposits. A careful examination of the evolutionary stages of the foraminifer Eoparastaffella provides a more accurate criterion for the definition of the T–V boundary, but does not significantly modify the historical one. The distinction of two morphotypes is based on the elevation of the last whorl and the peripheral outline. Tournaisian specimens of Eoparastaffella have a well rounded periphery (morphotype 1) contrasting with the subangular periphery of younger Viséan specimens (morphotype 2). A coefficient can be deduced from simple biometric measurements for more precisely defining the T–V boundary. The sequence stratigraphy of the T–V strata in South China has been reconstructed by combining biostratigraphical and sedimentological data. It allowed the correlation of the T–V transitional strata between the platform area and the slope and basinal locations. Late Tournaisian strata were deposited during a highstand systems tract. Near the end of the Tournaisian, a major drop in relative sea-level led to the development of an unconformity in the platform area. Lowstand deposits formed during latest Tournaisian time in the basin where a detailed biostratigraphic framework has been devised. Sediments deposited during the ensuing transgressive systems tract overlie the late Tournaisian highstand sediments in the platform area and the latest Tournaisian lowstand deposits in the basin. A major drop in relative sea-level near the end of the Tournaisian has been recognized worldwide. Therefore, the possibility of using the sequence stratigraphy of the T–V strata in South China for worldwide correlations should be investigated. © 1997 John Wiley & Sons, Ltd.     

Decoupling between the middle and upper crust during transpression-related lateral flow: Variscan evolution of the Aston gneiss dome (Pyrenees, France)

We present a structural, AMS, microstructural and kinematic study of the Aston gneiss dome (French Pyrenees), which consists of a core made up of orthogneiss and paragneiss intruded by numerous sills of Carboniferous peraluminous granite. The orthogneiss corresponds to a former Ordovician granitic laccolith. Four Variscan events have been evidenced in this gneiss dome: (i) D1 deformation observed only as relics in the orthogneisses and their country-rocks located above the sillimanite isograd, and characterized by a NS to NE–SW non coaxial stretch associated to top to the south motions (NS convergence); (ii) D2-a deformation observed in the orthogneisses and their country-rocks, mainly migmatitic paragneisses, located below the sillimanite isograd and in the peraluminous granites whatever their structural level, and characterized by an EW to N120°E stretch associated to a top to the east flat shearing (lateral flow in the hot middle crust in a transpressive regime); (iii) D2-b deformation characterized by EW-trending megafolds corresponding to the domes in the middle crust and by EW-trending tight folds with subvertical axial planes in the metasedimentary upper crust; (iv) subvertical medium-temperature mylonitic bands developed by the end of the transpression.The Aston massif is a good example of decoupling between a cold upper crust and a hotter middle crust overheated by a thermal event originated in the upper mantle. This decoupling allowed the lateral flow of the migmatitic middle crust along a direction at high angle with respect to the more or less NS-trending direction of convergence. We suggest that the HT-LP metamorphism developed before the formation of the domes during D2-a, coevally with the emplacement of numerous sills of peraluminous granite, whereas the emplacement of the large calc-alkaline plutons in the upper crust occurred by the end of D2-b. Our data invalidate the previous geodynamical models based on either early or late extensional regime to explain the development of the HT-LP metamorphism. This new interpretation of the dynamics of the Variscan crust of the Pyrenees is consistent with recent studies conducted in Archaean and Palaeoproterozoic hot continental crusts having undergone oblique convergence, and characterized by a competition between vertical thickening and lateral flow induced by the important rheological contrast between two thermally different levels.     

Welsh Borderland bouillabaisse: Lower Old Red Sandstone fish microfossils and their significance

Fish remains from over 100 localities in the Upper Silurian to Lower Devonian (traditional Lower Old Red Sandstone: LORS: Přidolí–Pragian) of Wales and the Welsh Borderland Anglo-Welsh Basin, southwest Britain have been investigated. Work on microfossils of fish (‘microvertebrates’, generally <5–8 mm) is reviewed, covering agnathan thelodonts, heterostracans, cephalaspids, anaspids, and gnathostomes including acanthodians, placoderms, and chondrichthyans, including the first from Pembrokeshire. Scales of the following taxa are newly identified: acanthodians Euthacanthus sp., Nostolepis musca, Parexus recurvus and Cheiracanthoides sp. cf. C. rarus; early “sharks” including Altholepis sp.; and a (?)radotinid placoderm. Species ranges in space, time and environment reveal interesting patterns, the most significant being a wide geographic distribution, which does not support a wholly freshwater provenance for the Anglo-Welsh Basin; endemic taxa are few. Using the International mid-Palaeozoic Microvertebrate zonal scheme, the presence of a Thelodus parvidens–Paralogania ludlowiensis-osteostracan Assemblage within the Ludlow Bonebed at the base of the former Downton Group (now in part in the new lithostratigraphically defined Daugleddau Group) supports a basal Přidolí age for the member. A mid-Přidolí dearth with few taxa, mainly acanthodians and cephalaspids is followed by an upper Přidolí Trimerolepis–Paralogania kummerowi–Loganellia cuneata-poracanthodid-Toombsaspis pococki Assemblage. The Silurian–Devonian boundary is equated with the appearance of Turinia pagei and associated taxa including Phialaspis symondsi at a level about 30 m below the local Chapel Point Limestone. This biozone can be correlated across the Old Red Sandstone continent. All vertebrate species including newly recognised Lochkovian chondrichthyans indicate marine environments were present in the LORS.     

广西玉林早泥盆世早期腕足动物生物地层研究

在广西玉林樟木地区早泥盆世北均塘组、良合塘组、樟木组３５属４８种腕足动物演化和地层分布特征研究的基础上,建立了６个腕足动物生物带（自下而上）：１．Ｑｕａｄｒｉｔｈｙｒｉｎａｅｘｐａｎｓａ－Ｐｒｏｄａｖｉｄｓｏｎｉａｍｉｒａｂｉｌｉｓ带;２．Ｇｒａｙｉｎａｍａｇｎｉｆｉｃａｇｕａｎｇｘｉｅｓｉｓ－Ｓｃｈｉｚｏｐｈｏｒｉａｓｕｌｃａｔｉｎａ带;３．Ｒｅｔｉｃｕｌａｒｉｏｐｓｉｓｃｏｓｔａｔｕｓ带;４．Ｇｒａｙｉｎａｍａｇｎｉｆｉｃａｓｉｎｉｃａ带;５．Ｑｕａｄｒｉｔｈｙｒｉｓｒｏｂｕｓｔａ－Ｂｏｕｃｏｔｉａ带;６．Ｑｒｉｅｎｔｏｓｐｉｒｉｆｅｒｗａｎｇｉ带。依据国际对比和与笔石的层位关系认为：第１－３带为晚洛赫柯夫期,并且１、２、３带很可能分别相当晚洛赫柯夫早、中、晚期;第４带为早布拉格早期;第５、６带分别相当中、晚布拉格期。     

Metamorphic inheritance of Rheic passive margin evolution and its early‐Variscan overprint in the Teplá‐Barrandian Unit,Bohemian Massif

Rift‐related regional metamorphism of passive margins is usually difficult to observe on the surface, mainly due to its strong metamorphic overprint during the subsequent orogenic processes that cause its exposure. However, recognition of such a pre‐orogenic evolution is achievable by careful characterization of the polyphase tectono‐metamorphic record of the orogenic upper plate. A multidisciplinary approach, involving metamorphic petrology, P–T modelling, structural geology and in situ U‐Pb monazite geochronology using laser‐ablation split‐stream inductively coupled plasma mass spectrometry, was applied to unravel the polyphase tectono‐metamorphic record of metapelites at the western margin of the Teplá‐Barrandian domain in the Bohemian Massif. The study resulted in discovery of three tectono‐metamorphic events. The oldest event M1 is LP–HT regional metamorphism with a geothermal gradient between 30 and 50 °C km^?1, peak temperatures up to 650 °C and of Cambro‐Ordovician age (c. 485 Ma). The M1 event was followed by M2‐D2, which is characterized by a Barrovian sequence of minerals from biotite to kyanite and a geothermal gradient of 20–25 °C km^?1. D2‐M2 is associated with a vertical fabric S2 and was dated as Devonian (c. 375 Ma). Finally, the vertical fabric S2 was overprinted by a D3‐M3 event that formed sillimanite to chlorite bearing gently inclined fabric S3 also of Devonian age. The high geothermal gradient of the M1 event can be explained as the result of an extensional, rift‐related tectonic setting. In addition, restoration of the deep architecture and polarity of the extended domain before the Devonian history – together with the supracrustal sedimentary and magmatic record – lead us to propose a model for formation of an Ordovician passive continental margin. The subsequent Devonian evolution is interpreted as horizontal shortening of the passive margin at the beginning of Variscan convergence, followed by detachment‐accommodated exhumation of lower‐crustal rocks. Both Devonian shortening and detachment occurred in the upper plate of a Devonian subduction zone. The tectonic evolution presented in this article modifies previous models of the tectonic history of the western margin of the Teplá‐Barrandian domain, and also put constraints on the evolution of the southern margin of the Rheic ocean from the passive margin formation to the early phases of Variscan orogeny.     

Recent activity and seismotectonics of the Eastern Pyrenees

Results from a recent earthquake in the Eastern Pyrenees are presented and the seismotectonics of the region is analyzed from the presently available data. On 26 September 1984 an earthquake (M_L = 4.4) took place in the area of the historical destructive earthquake of 1428. Several portable stations installed in the epicentral area to record aftershocks permitted of defining a precise location at 42°19.2′N, 2°10.2′E and 5 km depth. A maximum felt intensity of V (MSK) is obtained from macroseismic data. The epicentral location lies within a block bounded by E-W-trending structures and the focal solution shows right-lateral shearing with a NW-SE pressure axis.The seismicity in the Eastern Pyrenees shows a complex pattern which can be associated with both E-W fractures and NE-SW fault systems. Focal solutions of another two recent earthquakes of M_L ~ 4, with differences in horizontal pressure axis, are also discussed.