Genesis of stromatactis in an upper jurassic carbonate buildup (Mlynka,Cracow region,Southern Poland): Internal reworking and erosion of organic growth cavities

Summary The Middle Oxfordian strata in the southern part of the Cracow-Wielun Upland consist of platy and bedded limestones (‘normal facies’), of massive limestones as well as locally of mass flow sediments. Massive limestones, prevailing in the Upper Oxfordian, form commonly carbonate buildups, which are made up predominantly of cyanobacterial allochems and to a minor amount of siliceous sponges. Stromatactis can be best observed in the Mlynka quarry. They occurs in the uppermost part of slope sediments close to a cyanobacterial-sponge buildup. The bedding-plane of the slope sediments is directly overlain by debris-flow and grain-flow sediments. Fragments of a primary laminar framework rich in growth-cavities occur in the uppermost part of the slope sediments as precondition for the formation of stromatactis. The stromatactis cavities were formed by internal reworking and erosion within these organic growth cavities, caused by strong bottom currents due to mass transport from higher parts of the buildup.     

The significance ofSaccocoma-calciturbidites for the analysis of the Polish epicontinental late Jurassic Basin: An example from the Southern Cracow-Wielun Upland (Poland)

Summary In the top section of the Upper Jurassic profile in the S part of the Cracow-Wielun upland there occur deposits with numerous fragments of the plantonic crinoidsSaccocoma. Sedimentary structures indicate that these deposits are calciturbidites with domination of the redeposited pelagic material. TheSaccocoma-calciturbidites rest on the slope beds of Oxfordian cyanobacterial-sponge carbonate buildups formed in the Polish epicontinental basin, bordering the Tethys ocean in the north. The occurrence of the planktonicSaccocoma seems to be connected with a short deepening the S part of the Polish epicontinental basin in the Late Jurassic. This deepening caused the change within biocoenoses thriving in carbonate buildups and was mainly expressed in reducingTubiphytes. ‘Tubiphytes-reefs’, representing the last stage in the development of the carbonate buildups in the S part of the Cracow-Wielun upland, marked the most shallow sedimentation environment. With deepending of the basin,Tubiphytes and other benthonic forms disappeared, and, simultaneously, the dominant fauna became planktonic. The abundance of planktonic crinoidsSaccocoma (=Lombardia), as well as the presence of planktonic foraminifers, nannoplankton cf.Schizosphaerella, coccoliths and radiolarians indicates a pelagic, open-sea depositional environment. TheSaccocoma-dominated sediments, which had been primarily deposited from a suspension on a sea floor with a distinct relief, became subsequently transported by turbidity currents. A limited extent and thickness of theSaccocoma-calciturbidites was caused by a relatively small amount of the primary material which could be transferred by the turbidity currents because the period of pelagic sedimentation was short. TheSaccocoma-calciturbidites indicate a distinct shift in conditions of sedimentation resulting from over-regional changes and, despite the lack of index fossils, seem to represent a local lithostratigraphic horizon. These sediments probably mark a sedimentation event which caused a minor levelling of the sea floor relief. Then, after a sedimentation break, wide-spread destruction of the tops of carbonate buildups and formation of debris flows in the shallowing Late Jurassic sea took place. TheSaccocoma-calciturbidites in the S part of the Cracow-Wielun upland can be found near edges of horsts. This suggests that the foundations of these horsts are probably of sedimentary origin, dating back at least to the Late Jurassic. TheSaccocoma-calciturbidites in the S part of the Polish epicontinental basin seem to result from local, synsedimentary tectonic movements, which probably reflect over-regional events on the one hand, and oscillations of the sea level-on the other.     

The origin of Jurassic reefs: Current research developments and results

Summary In order to elucidate the control of local, regional and global factors on occurrence, distribution and character of Jurassic reefs, reefal settings of Mid and Late Jurassic age from southwestern Germany, Iberia and Romania were compared in terms of their sedimentological (including diagenetic), palaeoecological, architectural, stratigraphic and sequential aspects. Upper Jurassic reefs of southern Germany are dominated by siliceous sponge—microbial crust automicritic to allomicritic mounds. During the Oxfordian these form small to large buildups, whereas during the Kimmeridgian they more frequently are but marginal parts of large grain-dominated massive buildups. Diagenesis of sponge facies is largely governed by the original composition and fabric of sediments. The latest Kimmeridgian and Tithonian spongiolite development is locally accompanied by coral facies, forming large reefs on spongiolitic topographic elevations or, more frequently, small meadows and patch reefs within bioclastic to oolitic shoal and apron sediments. New biostratigraphic results indicate a narrower time gap between Swabian and Franconian coral development than previously thought. Palynostratigraphy and mineralostratigraphy partly allow good stratigraphic resolution also in spongiolitic buildups, and even in dolomitised massive limestones. Spongiolite development of the Bajocian and Oxfordian of eastern Spain shares many similarities. They are both dominated by extensive biostromal development which is related to hardground formation during flooding events. The Upper Jurassic siliceous sponge facies from Portugal is more localised, though more differentiated, comprising biostromal, mudmound and sponge-thrombolite as well as frequent mixed coral-sponge facies. The Iberian Upper Jurassic coral facies includes a great variety of coral reef and platform types, a pattern which together with the analysis of coral associations reflects the great variability of reefal environments. Microbial reefs ranging from coralrich to siliceous sponge-bearing to pure thrombolites frequently developed at different water depths. Reef corals even thrived within terrigeneous settings. In eastern Romania, small coral reefs of various types as well as larger siliceous sponge-microbial crust mounds grew contemporaneously during the Oxfordian, occupying different bathymetric positions on a homoclinal ramp. Application of sequence stratigraphic concepts demonstrates that onset or, in other cases, maximum development of reef growth is related to sea level rise (transgressions and early highstand) which caused a reduction in allochthonous sedimentation. The connection of reef development with low background sedimentation is corroborated by the richness of reefs in encrusting organisms, borers and microbial crusts. Microbial crusts and other automicrites can largely contribute to the formation of reef rock during allosedimentary hiatuses. However, many reefs could cope with variable, though reduced, rates of background sedimentation. This is reflected by differences in faunal diversities and the partial dominance of morphologically adapted forms. Besides corals, some sponges and associated brachiopods show distinct morphologies reflecting sedimentation rate and substrate consistency. Bathymetry is another important factor in the determination of reefal composition. Not only a generally deeper position of siliceous sponge facies relative to coral facies, but also further bathymetric differentiation within both facies groups is reflected by changes in the composition, diversity and, partly, morphology of sponges, corals, cementing bivalves and microencrusters. Criteria such as authigenic glauconite, dysaerobic epibentic bivalves,Chondrites burrows or framboidal pyrite in the surrounding sediments of many Upper Jurassic thrombolitic buildups suggest that oxygen depletion excluded higher reefal metazoans in many of these reefs. Their position within shallowing-upwards successions and associated fauna from aerated settings show that thrombolitic reefs occurred over a broad bathymetric area, from moderately shallow to deep water. Increases in the alkalinity of sea water possibly enhanced calcification. Reefs were much more common during the Late Jurassic than during the older parts of this period. Particularly the differences between the Mid and Late Jurassic frequencies of reefs can be largely explained by a wider availability of suitable reef habitats provided by the general sea level rise, rather than by an evolutionary radiation of reef biota. The scarcity of siliceous sponge reefs on the tectonically more active southern Tethyan margin as well as in the Lusitanian Basin of west-central Portugal reflects the scarcity of suitable mid to outer ramp niches. Coral reefs occurred in a larger variety of structural settings. Upper Jurassic coral reefs partly grew in high latitudinal areas suggesting an equilibrated climate. This appears to be an effect of the buffering capacity of high sea level. These feedback effects of high sea level also may have reduced oceanic circulation particularly during flooding events of third and higher order, which gave rise to the development of black shales and dysaerobic thrombolite reefs. Hence, the interplay of local, regional and global factors caused Jurassic reefs to be more differentiated than modern ones, including near-actualistic coral reefs as well as non-actualistic sponge and microbial reefs.     

Origin and evolution of an Upper Jurassic complex of carbonate buildups from Zegarowe Rocks (Kraków–Wieluń Upland, Poland)

The Upper Jurassic complex of Zegarowe Rocks is situated on the Kraków–Wieluń Upland in southern Poland. The complex is dominated by massive limestones representing carbonate buildups. The successive stages of carbonate buildup development include: colonisation, aggradational growth and progradation phases. In the colonisation phase, on top of loose peloidal-ooid sands micritic peloidal thrombolites developed. Peloidal and agglutinated thrombolites and stromatolites proliferated during the aggradational growth phase, whereas the progradation phase was characterised by shallowing and related development of agglutinated stromatolites with coprolites. The latter were the effect of periodical stabilisation of detrital sediments by microbial mats. The Zegarowe Rocks complex developed upon an elevation of the Late Jurassic stable northern shelf of the Tethys. This elevation was formed due to local decrease in subsidence rate, induced by the presence of a Palaeozoic granitoid intrusion in the shelf substratum. The carbonate buildups of the Zegarowe Rocks complex, initially developing as sediment-starved mounds upon fault-controlled intraplatform highs under strongly restricted background sedimentation rate, were replaced by agglutinated microbial reefs.     

Youngest early carboniferous (late Visean) shallow-water patch reefs in eastern Australia (Rockhampton Group, Queensland): Combining quantitative micro- and macro-scale data

Summary Although skeletal organisms have received most of the emphasis in studies on Phanerozoic roef history, the roles of non-skeletal (non-enzymatic) carbonates (e.g., synsedimentary cements, automicrite, microbialite, etc.) in reef framework construction are becoming increasingly better understood. One problem in understanding the role of non-enzymatic carbonates in reef construction has been the difficulty in recognizing them in reef facies. Whereas skeletal organisms commonly can be recognized and documented in the field, non-enzymatic carbonates may be recognizable only in thin section. This paper describes the application of a new sampling technique that allows the quantitative comparison of skeletal macrofauna and flora with associated non-enzymatic carbonates and other microfaunal/microfloral constituents. The technique involves the point counting of thin sections made from small diameter cores that are systematically recovered from grids and line transects that cover a reasonable area (m²) of reef facies. Small, shallow-water patch reefs are abundant in scattered oolitic intervals in the Lower Carboniferous strata of eastern Australia. The youngest known Carboniferous reefs in eastern Australia occur in uppermost Visean strata (limestone FC5) near the top of the Rockhampton Group, approximately 50 km west-northwest of Rockhampton, Queensland. The largest sampled reef was 15 m thick and 42 m in diameter, with synsedimentary relief above the sea floor of at least 2 m during the primary growth phase. The reef occurs within bioclasticoolitic grainstones representing a shallow shelf setting and consists of eight common framework microfacies: 1) coral boundstone; 2) bryozoan boundstone; 3) mixed crinoid-bryozoan boundstone; 4) tubular problematica boundstone; 5) sponge-automicrite boundstone; 6) encrusted thrombolite boundstone; 7) mixed automicrite boundstone; and 8) thrombolitic wackestone-packstone. Reef growth was initiated by automicrite-producing biofilms, sponges and a tubular problematic organism. Primary relief building was accomplished by automicrite-dominated frameworks and lithistid sponges, crinoids, and corals. Large cerioidAphrophyllum coral colonies had a heterogeneous distribution through the reef. The framework of the main relief-bearing portion of the reef consists on average of 44.4% automicrite and automicrite-bound detritus, excluding automicrite-bound sponge body fossils, and at most 19.6% skeletal organisms in growth position (minimum of 7.2%). If sponge body fossils are included as automicrite framework, because they are preserved only as a result of automicrite formation, the percentage of automicrite and bound sediment is 54.9%. A smaller sampled reef consisting of the same basic facies had 39.5% automicrite and automicrite-bound sediment in its fremework (50.2% including sponges) and, at most, 33.4% skeletal organisms in growth position (minimum of 22.7%). The greater volume of skeletal framework in the small reef reflects a greater proportion of large corals. Of framebuilding skeletal organisms, automicrite-preserved lithistid and other sponges and cerioid rugose corals provided the greatest volume. However, crinoid holdfasts were the most widespread skeletal framework components. The dominant framework facies are sponge-automicrite boundstone, encrusted thrombolite, boundstone, mixed automicrite boundstone, and coral boundstone. The reefs are similar in overall framework construction and ecological succession to slightly older Visean reefs in eastern Australia and to some of the late Visean reefs of northern England. Surprisingly, framework similarities also exist between the reefs and certain thrombolite-lithistid-coral reefs of the European Jurassic.     

The late jurassic ‘Massenkalk fazies’ of Southern Germany: calcareous sand piles rather than organic reefs

Summary Upper Jurassic (Malm δ to ζ1) massive limestones (‘algal-sponge-reefs, sponge-reefs, reef-complexes, reefs, algal-sponge-bioherms, biolithites, Massenkalk, bioherms, Stillwasser-Mudmounds’) were analyzed in the Southern Swabian Alb, the Southern Franconian Alb and in drilling wells in the Molasse basin (Southern Bavaria). This analysis was carried out within the frame of a multidisciplinary DFG-study with the objective of decifering the controls on the development of Upper Jurassic spongiolites, their three-dimensional distribution, their characteristic faunal composition, and the diagenetic trends of the different primary facies. The data base consists of detailed facies mapping in the areas of the Eybtal and the Blautal (1300 samples) as well as comparative studies in the Upper Donautal (Swabian Alb) and the Southern Franconian Alb (400 samples). All together about 500 thin sections were studied. The distribution of the most important components (ooids, intraclasts, peloids, corals, sponges, sponge spicules, cyanobacterial crusts, brachiopods, molluscs, echinoids, bryozoans, serpulids,Terebella, Tubiphytes), and diagenetic features (dolomite, dedolomite, silicification, stylolites, clay flasers, hematite patches) results in a spatial distribution pattern of facies types. The largest part (70 %) of the massive limestones consists of a peloid-lithoclast-ooid sand facies rich in completely or partly micritized ooids. These ooids, especially in beds of the Malm δ to ε, might be the clue to a reinterpretation of the water depth. True biogenic constructions occur (about 30 % of the volume; sponge-algalmudmounds, algal-sponge-boundstones, and brachiopod-algal-sponge-mounds) within and at the margins of this facies and are interpreted as platform sands. The spatial distribution of the buildups in relation to the sand facies was probably controlled by hydrodynamic conditions. In addition, zoned sponge-algal-mounds occur in intraplatform channels and nodular sponge-algal-mudmounds in the marly basin sediments between platform sand areas. Breccias and slumpings in beds older than the Malm ζ have to be reinterpreted. Most of the breccias found originated from the flanks of the sand platforms, reflecting the faunal composition of the algal-sponge-boundstones which stabilized the flanks. Breccias of this composition occur throughout the Malm δ-ζ1 and differ markedly in their composition from the sand facies. The boundary breccia (Malm ε/ζ1) is interpreted as marking a regressive maximum. The increasing growth of buildups, rich in brachiopods in the Malm ζ1, is ascribed to an increase of reef growth at the beginning of a transgression. Detailed facies analyses necessary for the reconstruction of the spatial distribution of different facies types are in progress. Most of the older data on faunal distributions cannot be used for detailed facies analysis because they differentiated only between massive facies and bedded facies. Therefore Upper Jurassic limestones of Southern Germany should be restudied in order to recognize the volumetric importance of sand facies and buildups within massive limestones.     

Hoof-Like Unguals,Skin, and Foot Movements Deduced from Deltapodus Casts of the Galve Basin (Upper Jurassic-Lower Cretaceous,Teruel, Spain)

Galve (Teruel, Spain) is a town in the interior of a synclinal fold with Upper Jurassic marine limestones along its flanks, and, in its core, Upper Jurassic–Lower Cretaceous continental and shoreline sediments crop out. The core sediments cover an area about 8 km², and contain a concentration of sites with footprints, bones, and eggshells of dinosaurs. The footprints are both shafts and natural casts. Some casts are attributed to stegosaurs (Deltapodus). The Deltapodus casts are characterized by features that allow us to make direct observations on the skin formed by polygonal scales, and ellipsoidal “hooves,” as well as deductions on the movement of the limbs during walking. According to the opinion of some authors, dinosaur footprints are indicators of the motion of their limbs and sometimes of the whole body. So far, results have been deduced from theropod, ornithopod, and sauropod footprints. This article shows the results obtained from analis of the aforementioned Deltapodus casts, i.e., forelimb movement similar to that of the forelimbs of sauropods, and the rigid structure of the autopodial part of the hind limb.     

<Emphasis Type="Italic">Crescentiella</Emphasis>-microbial-cement microframeworks in the Upper Jurassic reefs of the Crimean Peninsula

In the Upper Jurassic reef successions of the Crimean Peninsula (Sudak and Jalta areas), the microencruster Crescentiella morronensis (Crescenti), microbialites, and multiple generations of cements, form microframeworks. They were observed in two stages of the carbonate platform evolution, in the Middle–Upper Oxfordian, and in the Upper Kimmeridgian–Tithonian. Generally, in both stages, the features of the microframeworks are similar and consist of densely packed Crescentiella associated with microbialites and branched colonies of the sclerosponge Neuropora lusitanica Termier. The difference between the occurrences of the two stages is the variable amount of nubecularid foraminifera and enigmatic tube-shaped structures forming the central cavities of Crescentiella. The Crescentiella-microbial-cement microframeworks formed under phreatic conditions in the upper slope and seaward marginal depositional settings where intensive synsedimentary cementation took place. They formed in the initial stages of long cycles of restoration and blooming of the reefs. The late Jurassic examples resemble the Permian algae-microbial-cement reefs as well as the Triassic Tubiphytes and cement crust-dominated reefs. Concurrently, all these examples formed a transitional facies zone between typical slope facies to shallow subtidal platform margin facies characterized by high taxonomic diversity of calcified sponges, corals, and microencrusters forming the principal part of the reefs.     

Upper Triassic (Carnian) reef biota from the Sambosan Accretionary Complex, Kyushu, Japan

Calcified sponges, algae, and reef problematica are abundant yet poorly known from the Triassic of Japan. They are abundant in shallow-water carbonate, redeposited blocks of the Sambosan Accretionary Complex, Konosé Group, and southern Kyushu. Based on study of thin-sections from reef limestone exposed along the Kuma River, some important organisms and reef microfacies are described, which seem typical of Upper Triassic reef complexes. The most abundant reef organisms are hypercalcified sponges, including sphinctozoans, inozoans and chaetetids, followed by cyanophycean algae (including “Tubiphytes”-like organisms), and solenoporacean red algae. Loose sponge spicules in one thin-section also indicate the occurrence of rare hexactinellid sponges. Chambered demosponges described from the Konosé carbonate rocks include Solenolmia manon manon (Münster), Colospongia sp., Jablonskyia andrusovi (Jablonsky), several unidentified chambered sponges as well as the inozoid Permocorynella sp. 1 and Permocorynella sp. 2. Also present are chaetetid sponges and solenoporacean red algae belonging to Parachaetetes cassianus (Flügel) and Parachaetetes? sp. or Solenopora? sp. Especially abundant in thin-sections are cyanophyceans and “Tubiphytes”-like organisms. Among the organisms is Cladogirvanella Ott and Hedstroemia sp. The composition of the biota and presence of typical problematic organisms increases our knowledge of shallow-water Upper Triassic carbonate rocks in a remote setting in western Panthalassa. The composition of the biota indicates a mostly Carnian age. Most comparable organisms are known from both the northeastern and southern Tethys.     

Marine carbonate facies in response to climate and nutrient level: The upper carboniferous and permian of central spitsbergen (Svalbard)

Summary Carbonate-dominated successions of the Gipsdalen and Tempelfjorden Groups from Svalbard record a significant shift from Photozoan to Heterozoan particle associations in neritic settings during the late Palaeozoic. During the Bashkirian, benthic particle associations which included photoautotrophs such as phylloid algae (Chloroforam Association) characterised shallow subtidal environments. Most depositional settings which endured siliciclastic terrestrial input exhibited poorly diversified associations dominated by brachiopods, bryozoans and siliceous sponges (Bryonoderm Association). During the Moscovian to Asselian, highly diversified associations typified by various calcareous green algae,Palaeoaplysina, Tubiphytes, fusulinids, smaller and encrusting foraminifers (Chloroforam Association) prevailed in carbonate sediments from supratidal to shallow subtidal environments. During the Sakmarian and Early Artinskian, oolitic carbonate sands (Chloroforam Association) typified intertidal flats, whereas shallow subtidal environments were occupied by moderately diversified associations with fusulinids, smaller foraminifers, echinoderms and bryozoans (Bryonoderm-extended Association) and poorly diversified associations with echinoderms, brachiopods and bryozoans (Bryonoderm Association). During the Late Artinskian to Kazanian, poorly diversified associations characterised by brachiopods, echinoderms and bryozoans (Bryonoderm Association), and sponge-dominated associations (Hyalosponge Association) reigned within siliceous carbonates of intertidal and shallow subtidal environments. This trend is interpreted as a result of climatic cooling and fluctuations of prevailing levels of trophic resources within shallow-water settings during the studied time period. While raised nutrient levels were restricted to near-shore settings during the Bashkirian, steady mesotrophic conditions arose from the Sakmarian onward and increased to late Permian times.     

Coral-rudist bioconstructions in the Upper Cretaceous Haidach section (Gosau Group; Northern Calcareous Alps, Austria)

Summary In the area of Haidach (Northern Calcareous Alps, Austria), coral-rudist mounds, rudist biostromes, and bioclastic limestones and marls constitute an Upper Cretaceous shelf succession approximately 100 meters thick. The succession is part of the mixed siliciclasticcarbonate Gosau Group that was deposited at the northern margin of the Austroalpine microplate. In its lower part, the carbonate succession at Haidach comprises two stratal packages that each consists, from bottom to top, of a coral-rudist mound capped by a rudist biostrome which, in turn, is overlain by bioclastic limestones and, locally, marls. The coral-rudist mounds consist mainly of floatstones. The coral assemblage is dominated by Fungiina, Astreoina, Heterocoeniina andAgathelia asperella (stylinina). From the rudists, elevators (Vaccinites spp., radiolitids) and recumbents (Plagioptychus) are present. Calcareous sponges, sclerosponges, and octocorals are subordinate. The elevator rudists commonly are small; they settled on branched corals, coral heads, on rudists, and on biolastic debris. The rudists, in turn, provided settlement sites for corals. Predominantly plocoid and thamnasteroid coral growth forms indicate soft substrata and high sedimentation rates. The mounds were episodically smothered by carbonate mud. Many corals and rudists are coated by thick and diverse encrustations that indicate high nutrient level and/or turbid waters. The coral-rudist mounds are capped byVaccinites biostromes up to 5 m thick. The establishment of these biostromes may result from unfavourable environmental conditions for corals, coupled with the potential of the elevator rudists for effective substrate colonization. TheVaccinites biostromes are locally topped by a thin radiolitid biostrome. The biostromes, in turn, are overlain by bioclastic limestones; these are arranged in stratal packages that were deposited from carbonate sand bodies. Approximately midsection, an interval of marls with abundantPhelopteria is present. These marls were deposited in a quiet lagoonal area where meadows of sea grass or algae, coupled with an elevated nutrient level, triggered the mass occurrence ofPhelopteria. The upper part of the Haidach section consists of stratal packages that each is composed of a rudist biostrome overlain by bioclastic wackestones to packstones with diverse smaller benthic foraminifera and calcareous green algae. The biostromes are either built by radiolitids,Vaccinites, andPleurocora, or consist exclusively of radiolitids (mainlyRadiolites). Both the biostromes and the bioclastic limestones were deposited in a low-energy lagoonal environment that was punctuated by high-energy events.In situ-rudist fabrics typically have a matrix of mudstone to rudistclastic wackestone; other biogens (incl. smaller benthic foraminifera) are absent or very rare. The matrix of rudist fabrics that indicate episodic destruction by high-energy events contain a fossil assemblage similar to the vertically associated bioclastic limestones. Substrata colonized by rudists thus were unfavourable at least for smaller benthic foraminifera. The described succession was deposited on a gently inclined shelf segment, where coral-rudist mounds and hippuritid biostromes were separated by a belt of bioclastic sand bodies from a lagoon with radiolitid biostromes. The mounds document that corals and Late Cretaceous elevator rudists may co-occur in close association. On the scale of the entire succession, however, mainly as a result of the wide ecologic range of the rudists relative to corals, the coral-dominated mounds and the rudist biostromes are vertically separated.     

Lower Jurassic Bahamian-type facies in the Choč Nappe (Tatra Mts,West Carpathians,Poland) influenced by paleocirculation in the Western Tethys

The Lower Jurassic (upper Sinemurian) of the Hronicum domain (Tatra Mts., Western Carpathians, Poland) represents typical tropical shallow-water carbonates of the Bahamian-type. Eight microfacies recognized include oolitic-peloidal grainstone/packstone, peloidal-bioclastic grainstone, peloidal-lithoclastic-bioclastic-cortoidal grainstone/packstone, peloidal-bioclastic packstone/grainstone, peloidal-bioclastic wackestone, spiculitic wackestone, recrystallized peloidal-oolitic grainstone and subordinate dolosparites. The studied sediments were deposited on a shallow-water carbonate platform characterized by normal salinity, in high-energy oolite shoals, bars, back-margin, protected shallow lagoon and subordinately on restricted tidal flat. Some of them contain the microcoprolite Parafavreina, green alga Palaeodasycladus cf. mediterraneous (Pia) and Cayeuxia, typical of the Early Jurassic carbonate platforms of the Western Tethys. The spiculite wackestone from the upper part of the studied succession was deposited in a transitional to deeper-water setting. The studied upper Sinemurian carbonates of the Hronicum domain reveal microfacies similar to the other Bahamian-type platform carbonates of the Mediterranean region. Thereby, they record the northern range of the Lower Jurassic tropical shallow-water carbonates in the western part of the Tethys, albeit the thickness of the Bahamian-type carbonate successions generally decrease in a northerly direction. The sedimentation of the Bahamian-type deposits in the Hronicum domain, located during the Early Jurassic at about 28°N, besides other specific factors (i.e., light, salinity, and nutrients) was strongly controlled by the paleocirculation of warm ocean currents in the Western Tethys.     

Jurassic radiolarites in a Tethyan continental margin (Subbetic, southern Spain): palaeobathymetric and biostratigraphic considerations

A region of the pelagic Subbetic basin within the Southern Iberian Continental Margin is studied in lithostratigraphical and biostratigraphical detail. Jurassic radiolarites (Jarropa Radiolarite Formation, Bathonian–Oxfordian) interbedded with shallow-water marine limestones have been recognized. Underlying the radiolarites (Camarena Formation, Bajocian) are oolitic limestones showing shallowing-upward cycles with karstic surfaces on the top, corresponding to deposition on an isolated carbonate platform on volcanic edifices. The Milanos Formation (upper Kimmeridgian–Tithonian), overlying the radiolarites, contains calciclastic strata with hummocky cross-stratification, which indicate outer carbonate ramp deposition. In the Jarropa Radiolarite Formation some calcisiltite strata with hummocky cross-stratification have been found. The bathymetry of the Subbetic Jurassic pelagic sediments, including the radiolarites, is considered as moderate or shallow in depth. We suggest that the pelagic character of the Jurassic sediments in this margin and their equivalents in other Alpine domains is a consequence of distance from the continent (beyond the pericontinental platform) but not necessarily of depositional depth.     

Occurrence of high-diversity metazoan- to microbial-dominated bioconstructions in a shallow Kimmeridgian carbonate ramp (Jabaloyas,Spain)

The horizontal and vertical transitions of a wide range of bioconstructions are documented from the shallow domains of a Kimmeridgian carbonate ramp (Upper Jurassic) in the Jabaloyas area of NE Spain. The bioconstructions include microbial buildups, coral-bearing thrombolite buildups, coral-microbial buildups, branching coral patches, oyster patches, and stromatoporoid carpets. Buildups form stacked pinnacles up to 19 m thick, within a broad spectrum of coeval inter-buildup carbonate facies. Coral-bearing thrombolites are coincident with shallow-marine oolitic sands, indicating development during the initial platform flooding (unit 1). During the continued sea-level rise (units 2 and 3), coral-microbial buildups [encrusted by Crescentiella (Tubiphytes) and serpulids] were established from proximal to distal mid-ramp domains, and these showed an increasing proportion of microbial crust in distal domains. Inter-buildup oolitic facies sharply grade down-dip to hummocky cross-stratified intraclastic, peloidal, and skeletal deposits, mostly sourced from the coral-microbial buildups. The lower part of unit 4 was dominated by microbialites in the proximal areas, related to local fresh-water input causing seawater stratification and oxygen depletion. The upper part of unit 4 indicates an initial recovery of metazoan frame builders, with abundant branching corals. During the late regression (units 5 and 6), Marinella lugeoni red algae, oyster patches, and stromatoporoid boulders developed close to the shoreline in well-oxygenated waters with high nutrient content. The reported data contribute to the discussion of the optimal environmental conditions for each “bioconstruction window” in Jabaloyas, namely sediment and nutrient supply, water depth, water oxygenation, wave energy and light availability.     

Upper jurassic to lower cretaceous carbonate facies of african affinities in a Peri-European area: Chalkidiki Peninsula, Greece

Summary The Epanomi-New Iraklia area (West coast of the Chalkidiki peninsula) is considered to belong to the Prepeonias subzone (or Gevgeli unit), with a palaeogeographic position near the European margin, represented by the Serbo-Macedonian massif, and at a considerable distance from the fragmented African plate, the marginal block of which is here the Pelagonian Domain. In some boreholes in the area an Upper Jurassic to Lowei Cretaceous limestone sequence has been observed, ending with an unconformity and followed by an Upper Middle-Lower Upper Eocene transgressive bioclastic limestone, an Upper Eocene to Lower Oligocene clastic series and Neogene deposits. This Upper Jurassic to Lower Cretaceous carbonate platform sequence and probably the Upper Jurassic limestones with bauxites of the nearby Mt. Katsika, show African affinities, viz: the presence of the essentially Aptian algal speciesSalpingoporella dinarica, an African plate marker; the chlorozoan type association and the bauxite formation during the Late Jurassic indicating tropical conditions; finally, the chloralgal type association and the sporadic presence of radial-fibrous ooids during the Early Cretaceous indicating peritropical conditions. Lower Cretaceous limestones are apparently missing in the innermost Hellenides. In the Pelagonian Domain s.l., on the other hand, Upper Jurassic to Lower Cretaceous limestones are found in some places, with same characteristics as in the Epanomi-New Iraklia boreholes. On the contrary, the Upper Eocene to Lower Oligocene clastic series of the boreholes can be correlated with the Axios (=Vardar) molassic basin, inline with its present situation. During the Mesozoic, the Epanomi area therefore belonged to a micro-block, next to the NE margin of the Pelagonian Domain, in contrast to earlier interpretations. Its present time position results from Early Cenozoic tectonic phases.     

Microbial contribution to deposition of upper carboniferous and lower Permian seamount-top carbonates,Akiyoshi, Japan

Summary Microbial organisms significantly contributed to the accumulation of shallow-marine carbonates in an open-ocean realm of the Panthalassan Ocean during Late Carboniferous-Early Permian time. The Jigokudai plateau in the northern part of the Akiyoshidai Plateau is the study area, where the limestone of the Upper Carboniferous Kasimovian Stage to the Lower Permian Artinskian Stage is well exposed. The fusulinid biostratigraphy as well as top-bottom geopetal fabrics revealed that the rocks of the study area are overturned. The thickness of this succession is approximated to 150 m. The succession is lithologically divided into the Lower Jigokudai and Upper Jigokudai formations. The lime-stones of these formations were deposited in a lagoonal setting. The Lower Jigokudai formation (95 m thick: Kasimovian to Asselian) is characterized by sand shoal facies represented by crinoid-Tubiphytes-fusulinid peloidal pack/grainstones and oolitic grainstones. Phylloid algal grain/packstones and microbial boundstones subordinately crop out. The Upper Jigokudai Formation (55 m thick: Sakmarian to Artinskian) is characterized by shoal and tidal flat facies represented by mollusk-fusulinid peloidal grain/rudstones, and peloidal grain/rudstones and peloidal lime-mudstones, respectively. Laterally discontinuous microbial bound-stones occur intercalated in mollusk-fusulinid peloidal grain/rudstones. This formation contains pendant and meniscus cements, and flat-pebble breccia indicative of an intertidal deposition and subaerial exposure. Various types of boundstone and organosedimentary structures constructed mainly by filamentous cyanobacteria,Tubiphytes obscurus tubular microproblematicum A, and other microproblematica were recognized. Significant facies types are (1) filamentous cyanobacteria-microproblematicum A bind/framestones, (2)Tubiphytes obscurus bindstones, (3) stromatolitic bindstones, (4) microbial laminites, (5) microbially linked structures, (6) oncoids, (7) microproblematica B-C framestones. The calcimicrobes, combined with synsedimentary cementation, formed small-scale and low-relief mounds of these facies, and greatly contributed to the deposition of the Kasimovian to Artinskian Panthalassan buildup.     

Middle Miocene carbonates from the Northern Plateau of the Western Desert (Egypt): Petrography and geochemistry

Summary An extensive carbonate platform of predominately Middle Miocene age (Marmarica Formation) occupies the larger part of the northern plateau of the Western Desert of Egypt. The Marmarica Formation (up to 150m thick) exposed on the cliffs facing the Mediterranean coast consists mainly of alternating limestones and dolostones. Deposition took place in a shallow and normal marine environment. The limestones are dominated by algal boundstone, crossbedded packstone and bioturbated wackestone facies. The occurrence of the crossbedded packstone facies throughout the Marmarica Formation indicates that a shallow marine environment prevailed. Lithification of the precursor carbonates took place mainly in a meteoric environment. Replacement dolomitization ranged from fabric destructive to retentative and from fabric selective to pervasive. The presence of an abundant open marine fauna, the lack of evaporites, coupled with the contents of Sr and Na suggests that dolomitization took place in solutions more dilute than normal sea water. The limestone and dolostone facies cannot be separated into distinct types based on their major or trace element chemistry. Only Mn and Sr seem to be facially controlled. Both elements are particularly enriched in the lagoonal facies compared with the organic buildup facies. The difference in the Mn content is attributed to their proximity to continental areas at the time of deposition. The differences in Sr values are interpreted by an originally differing mineralogy (calcite versus aragonite) and different rates of diagenesis. Dolomitization did not appear to influence the Mn content as substantially as the Sr content. The amount of the acid insoluble residue is controlled by the distribution of Si, Ti, Al, Fe, k, Rb and Zr.     

Maastrichtian facies succession and sea-level history of the Hossein-Abad,Neyriz area,Zagros Basin

The Maastrichtian shallow-water carbonate platform (Tarbur Formation) is described from outcrop in southwest Iran. It is characterised by eight microfacies types, which are dominated by larger foraminifera, rudist debris and dasycladacean algae. They are grouped into four distinct depositional settings: tidal flat, lagoon, barrier and open marine. The depositional settings include stromatolitic boundstone of tidal flat, peloidal dasycladacean miliolids wackestone and peloid bioclastic imperforate foraminifera wackestone of restricted lagoon, Omphalocyclus miliolids bioclast packstone–grainstone and miliolids intraclast bioclast packstone–grainstone of open lagoon, rudist bioclast grainstone of inner-platform shoals and rudist bioclast floatstone–rudstone and bioclastic wackestone of open-marine environments.

The facies and faunal characters are typical of a ramp-like open shelf. The lack of reef-constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. On the basis of facies analysis, three depositional sequences (third order) are defined.     

A eustatically driven calciturbidite sequence from the Dinantian II of the Eastern Rheinisches Schiefergebirge

Summary The Gladenbach Formation is an approximately 30 m thick, well-segregated calciturbidite sequence, restricted to the H?rre belt of the eastern Rheinisches Schiefergebirge. It is middle Tournaisian in age (lowerPericyclus Stage, lower cd II of the German Culm zonation) and is an equivalent of the Liegende Alaunschiefer. The sequence is composed predominantly of minor turbiditic fining-upward cycles. Cycles start with massive calciturbidite beds. They are composed of fine-grained intraclastic-bioclastic grainstone/packstone, more or less ooid-bearing in the top of the formation, and/or radiolarian-rich packstone. Cycles continue with platy, dense limestones consisting of radiolarian-rich wackestone/packstone and microlithoclastic-microbioclastic wackestone/packstone. Different types of shales finish the fining-upward development. Minor cycles can be grouped into several 4th order cycles, composing a single 3rd order cycle. Towards the top, abundance of resedimented platform components, like ooids, calcareous smaller foraminifers, echinoderms, brachiopods, bryozoans and critical conodont genera, increases. Simultaneously, the thickness of the minor cycles decreases. This indicates a transgressive phase, characterized by increasing over-production of carbonate on platform realms and a correlated increase in the frequency of resedimentation events in the basin. The transgression corresponds to the well-documented global eustatic transgression of the Lowercrenulata andisosticha-uppercrenulata Zone of the conodont chronology. Thus, the Gladenbach Formation is interpreted as a transgressive systems tract/highstand systems tract. The Liegende Alaunschiefer is the time-equivalent, starved basin facies. Predominating hemipelagic calciturbidites of the lower Gladenbach Formation derive from the deeper shelf slope or from an intrabasinal swell, which might constitute a flexural bulge in front of the shelf slope. Turbidite sediments from the upper part of the formation derive from shelf-edge sands and the upper shelf slope. The source might be related to the ancient Devonian reef complex of Langenaubach-Breitscheid in the southwest.     

Microbial boundstone dominated carbonate slope (Upper Carboniferous,N Spain): Microfacies,lithofacies distribution and stratal geometry

Summary The Carboniferous, particularly during the Serpukhovian and Bashkirian time, was a period of scarce shallow-water calcimicrobial-microbialite reef growth. Organic frameworks developed on high-rising platforms are, however, recorded in the Precaspian Basin subsurface, Kazakhstan, Russia, Japan and Spain and represent uncommon occurrences within the general trend of low accumulation rates and scarcity of shallow-water reefs. Sierra del Cuera (Cantabrian Mountains, N Spain) is a well-exposed high-rising carbonate platform of Late Carboniferous (Bashkirian-Moscovian) age with a microbial boundstone-dominated slope dipping from 20° up to 45°. Kilometer-scale continuous exposures allow the detailed documentation of slope geometry and lithofacies spatial distribution. This study aims to develop a depositional model of steep-margined Late Paleozoic platforms built by microbial carbonates and to contribute to the understanding of the controlling factors on lithofacies characteristics, stacking patterns, accumulation rates and evolution of the depositional architecture of systems, which differ from light-dependent coralgal platform margins. From the platform break to depths of nearly 300 m, the slope is dominated by massive cement-rich boundstone, which accumulated through the biologically induced precipitation of micrite. Boundstone facies (type A) with peloidal carbonate mud, fenestellid and fistuliporid bryozoans, sponge-like molds and primary cavities filled by radiaxial fibrous cement occurs all over the slope but dominates the deeper settings. Type B boundstone consists of globose centimeter-scale laminated accretionary structures, which commonly host botryoidal cement in growth cavities. The laminae nucleate around fenestellid bryozoans, sponges, Renalcis and Girvanella-like filaments. Type B boundstone typically occurs at depths between 20–150 m to locally more than 300 m and forms the bulk of the Bashkirian prograding slope. The uppermost slope boundstone (type C; between 0 and 20–100 m depth) includes peloidal micrite, radiaxial fibrous cement, bryozoans, sponge molds, Donezella, Renalcis, Girvanella, Ortonella, calcareous algae and calcitornellid foraminifers. From depths of 80–200 m to 450 m, 1–30 m thick lenses of crinoidal packstone, spiculitic wackestone, and bryozoan biocementstone with red-stained micrite matrix are episodically intercalated with boundstone and breccias. These layers increase in number from the uppermost Bashkirian to the Moscovian in parallel with the change from a rapidly prograding to an aggrading architecture. The red-stained strata share comparable features with Lower Carboniferous deeper-water mud-mound facies and were deposited during relative rises of sea level and pauses in boundstone production. Rapid relative sea-level rises might have been associated with changes in oceanographic conditions not favourable for thecalcimicrobial boundstone growth, such as upwelling of colder, nutrient-rich waters lifting the thermocline to depths of 80–200 m. Downslope of 150–300 m, boundstones interfinger with layers of matrix-free breccias, lenses of matrix-rich breccias, platform- and slope-derived grainstone and crinoidal packstone. Clast-supported breccias bound by radiaxial cement are produced by rock falls and avalanches coeval to boundstone growth. Matrix-rich breccias are debris flow deposits triggered by the accumulation of red-stained layers. Debris flows develop following the relative sea-level rises, which favour the deposition of micrite-rich lithofacies on the slope rather than being related to relative sea-level falls and subaerial exposures. The steep slope angles are the result of in situ growth and rapid stabilization by marine cement in the uppermost part, passing into a detrital talus, which rests at the angle of repose of noncohesive material. In the Moscovian, the aggradational architecture and steeper clinoforms are the result of increased accommodation space due to tectonic subsidence and due to a reduction of slope accumulation rates (from 240±45−605±35 m/My to 130±5 m/My). The increasing number of red-stained layers and the decrease of boundstone productivity are attributed to environmental changes in the adjacent basin, in particular during relative rises of sea level and to possible cooling due to icehouse conditions. The geometry of the depositional system appears to be controlled by boundstone growth rates. During the Bashkirian, the boundstone growth potential is at least 10 times greater than average values for ancient carbonate systems. The slope progradation rates (nearly 400–1000 m/My) are similar to the highest values deduced for the Holocene Bahamian prograding platform margin. The fundamental differences with modern systems are that progradation of the microbial-boundstone dominated steep slope is primarily controlled by boundstone growth rates rather than by highstand shedding from the platform top and that boundstone growth is largely independent from light and controlled by the physicochemical characteristics of seawater.