Sedimentary facies from Upper Triassic reefal limestone of the Sambosan accretionary complex in Japan: mid-ocean patch reef development in the Panthalassa Ocean

Microfacies of the Early to Middle Norian reefal limestone of the Sambosan Accretionary Complex (SAC) at Kamase locality, southwest Japan, are classified into seven major facies types in stratigraphic order: peloidal grainstone-packstone, unfossiliferous lime-mudstone, tubular problematica-rich wackestone, sponge-coral floatstone, sponge bafflestone, coral rudstone, and peloidal-bioclastic packstone-grainstone. The SAC records patch reef development on a mid-oceanic seamount in the Panthalassa Ocean. Because most examples of Triassic reefs come from the former Tethys, counterparts such as those from the SAC are pivotal in resolving paleogeographic issues as well as clarifying the depositional patterns between the eastern Tethys and adjacent western Pacific (Panthalassa). We also reveal that the primary stratigraphy of the reefal limestone was disrupted by submarine landslides of the seamount in an open-ocean realm during the late Middle to Late Jurassic time.     

Jurassic neptunian dikes at Mt Mangart (Julian Alps,NW Slovenia)

Jurassic neptunian dikes are common within Upper Triassic to Lower Jurassic platform limestone of the Julian Alps. At Mt Mangart, the following geometries were observed: irregular dissolution cavities, thin penetrative fractures, larger fractures with sharp sidewalls, and laterally confined breccia bodies. Inside a complex neptunian dike system two main generations of infillings were differentiated. The first generation is heterogeneous and consists of bioclastic limestones, representing uniquely preserved sediments subdivided into five different microfacies. The second generation is more common and typically consists of coarse-grained breccias with host-rock clasts and marly limestone matrix containing echinoderms. Fracture formation and void filling of the first generation of neptunian dikes is dated as Pliensbachian and is interpreted to be caused by the Julian carbonate platform dissection due to widely recognized Lower Jurassic Tethyan rifting. The timing of formation for the second generation is only broadly constrained, ranging from the Pliensbachian to the Late Cretaceous.     

Late paleozoic and Late Triassic limestones from north Palawan Block (Philippines): Microfacies and paleogeographical implications

Summary Selected Late Paleozoic and Triassic limestone exposures were studied on northern Palawan Island, Philippines, with regard to microfacies, stratigraphy and facies interpretation. Although some of the outcrops were already reported in literature, we present the first detailed microfacies study. Late Paleozoic carbonates in the El Nido area are represented by widley distributed Permian and locally very restricted Carbonifenous limestones. Of particular interest is the first report of Carboniferous limestones in the Philippines dated by fossils. Fusulinids indicate a ‘Middle’ Carboniferous (Moscovian-Kasimovian) age of the Paglugaban Formation only known from Paglugaban Island. The Permian Minilog Formation consists mostly of fusulinid wackestones and dasycladacean wacke-/packstones. Fusulinid datings (neoschwagerinids and verbeekinids) provide a Guadalupian (Wordian-Capitanian) age. The depositional setting of the Middle Permian carbonates corresponds to a distally steepened ramp with biostromes built by alatoconchid bivalves locally associated with richthofeniid brachiopods. Late Triassic limestones occur in isolated exposures on and around Busuanga Island (Calamian Islands). The age of the investigated carbonates is Rhaetian based on the occurrence ofTriasina hantkent Maizon. Microfacies data indicate the existence of reefs (Malajon Island) and carbonate platforms (Kalampisanan Islands, Busuanga Island, Coron Island). Reef boundstones are characterized by abundant solenoporacean red algae, coralline sponges and corals. Platform carbonates yield a broad spectrum of microfacies types, predominantly wacke- and packstones with abundant involutinid foraminifera and some calcareous algae. These facies types correspond to platform carbonates known from other parts of Southeast Asia (Eastern Sulawesi and Banda Basin; Malay Peninsula and Malay Basin). The Philippine platform carbonates were deposited on and around seamounts surrounded by deeper water radiolarian cherts. The new data on facies and age of the Philippine Permian and Triassic carbonates contradict a close paleogeographical connection between the North Palawan Block and South China and arise problems for the currently proposed origin of the North Palawan Block at the paleomargin of South China. We hypothesize that North Palawan was part of the Indochina Block during the Carboniferous and Permian, separated from the Indochina Block during the Middle Permian and collided with the South China Block in the Late Cretaceous.     

Episodic sedimentation on a peri-Tethyan ridge through the Middle–Late Jurassic transition (Villány Mountains, southern Hungary)

The Villány area, as a central part of the Tisza microcontinent/terrane along the European margin of Tethys, was characterized by intense subsidence in the Early and Middle Triassic, followed by a long interruption of subsidence in the Late Triassic to Middle Jurassic. During the Middle–Late Jurassic transition, marine sedimentation started with three distinct sedimentary episodes dated as Late Bathonian, Early Callovian, and Middle–Late Callovian, respectively. The succession is terminated by a thick limestone of Middle Oxfordian age. The sedimentary features, microfacies, and macroinvertebrate associations of these four stratigraphic units are documented and illustrated. The Middle to Late Jurassic sedimentary episodes of the Villány succession record an interplay of local and global factors and paleogeographical changes. At the beginning, local tectonic movements governed the main features of sedimentation, though the role of eustasy was also essential. From the mid-Callovian onwards, global climatic, biotic, and paleoceanographical changes controlled the nature and formation of the local carbonate sediments. The Callovian stromatolites are attributed to the activity of sulphate-reducing bacteria in a deep sublittoral, current-swept environment. Upwelling of eutrophic Tethyan waters is recorded by the prevalence of the Bositra filament microfacies in the Callovian. The long submarine hiatus at around the Callovian–Oxfordian transition mirrors a serious restriction of the carbonate budget, due to sudden cooling and a change in the oceanic current system (opening of a circumglobal Tethyan Passage), and to a higher amount of dissolved CO₂. In the Middle Oxfordian, the carbonate production considerably increased in accordance with the sudden global warming.     

Distribution of Triassic Foraminifers in the Limestone Massifs of the Dalnegorsk District,Primorsky Krai

Paleontological Journal - Foraminifer assemblages from five massifs of the Triassic limestones of the Dalnegorsk District have been described for the first time, and images of these foraminifers...     

Facies and biota of Anisian to Carnian carbonate platforms in the Northern Calcareous Alps (Tyrol and Bavaria)

Summary During the Middle and early Late Triassic carbonate ramps and rimmed platforms developed at the northwestern margin of the Tethys ocean. In the Northern Calcareous Alps, Anisian stacked homoclinal ramps evolved through a transitional stage with distally steepened ramps to huge rimmed platforms of Late Ladinian to Early Carnian age. Middle Triassic to early Late Triassic facies and biota of basin, slope and platform depositional systems are described. Special emphasis is given to foraminifers, sponges, microproblematic organisms and algae. The Ladinian to early Carnian reef associations are characterized by the abundance of segmented sponges, microproblematica, biogenic crusts and synsedimentary cements. Among the foraminifers, recifal forms likeHydrania dulloi andCucurbita infundibuliformis (Carnian in age) are reported from the Northern Calcareous Alps for the first time. Some sphinctozoid sponges likeParavesicocaulis concentricus were known until now only from the Hungarian and Russian Triassic.     

Salinity reduction of the end-Triassic sea from the Alpine region into northwestern Europe

A palaeoecological analysis of the Penarth Group (='Rhaetic') of southern England and Wales is undertaken in terms of a species-richness comparison with the Zlambach and Kössen Beds of the Austrian Alps. The three groups studied, bivalves, foraminifers and ostracodes, comprise the most important invertebrate faunas occurring in the deposits cited. All show significant diversity from the Alps into northwest Europe. Coupled with the disappearance of stenohaline elements including ammonites, and taking into account other facies information, the evidence suggests a transgression of a shallow epicontinental sea in northwest Europe at the end of the Triassic. The salinity of this sea (˜25–30%□) was appreciably below that of the Tethyan ocean.     

Middle and Upper Triassic radiolarite components from the Kcira-Dushi-Komani ophiolitic mélange and their provenance (Mirdita Zone,Albania)

The Middle Jurassic Kcira-Dushi-Komani Mélange in the northwestern Mirdita Ophiolite Zone contains blocks of Triassic oceanic crust, radiolarites and open marine limestones. We describe the microfacies and present biostratigraphic data from radiolarite clasts and blocks and from basalt-radiolarite blocks with preserved autochthonous sedimentary cover. The radiolarians yield Middle to Late Triassic (Late Anisian to Late Norian) ages for the oceanic realm from which the ophiolite and radiolarite blocks and clasts derived. Together with limestone blocks, the provenance areas of the components in the Kcira-Dushi-Komani Mélange are determined as the distal shelf and the ocean floor of the Neotethys. In the course of ophiolite obduction, the components were transported by mass movements into newly formed trench-like basins in front of the westward propagating nappe stack. These basins were later incorporated in the nappe stack forming the typical features of a syntectonic mélange. Our radiolarian biostratigraphic data confirm Late Anisian formation of the Neotethys Ocean, parts of which became closed in the Middle Jurassic. The data clearly speak in favour of one Neotethys Ocean to the east, from which the Mirdita ophiolites derived as far-travelled nappes.     

Upper Triassic reefs of the Oman Mountains: Data from the South Tethyan margin

Summary The Upper Triassic reefal limestones of the Oman Mountains were investigated with respect to their microfacies, palaeontology and community structure. The reef fauna described and figured for the first time occurs in parautochthonous slope deposits of the Arabian platform (Sumeini Group) and in allochthonous reefal blocks (‘Oman Exotics’, Hawasina Complex). The ‘Oman Exotics’ are tectonically dislocated blocks, derived from isolated carbonate platforms on seamounts in the Hawasina basin or in the South Tethys Sea. The lithofacies and fauna of these blocks comprise a cyclic platform facies with megalodonts, reef and reef debris facies. The reefal limestones are dated as Norian/Rhaetian by benthic foraminiferal associations (Costifera, Siculocosta, Galeanella) and typical encrusting organisms (Alpinophragmium, Microtubus). Some small ‘Oman Exotics’ are of Carnian age. The shallow-marine organisms include scleractinian corals of different growth forms, ‘sphinctozoans’, ‘inozoans’ chaetetids, spongiomorphids, disjectoporids and solenoporacean algae as the main reef builders, various encrusters like microbes, foraminifers, sponges and many different problematical organisms for the stabilisation of the reef framework and a group of dwellers including benthic foraminifers, gastropods, bivalves and a few dasycladacean algae. The reef communities are characterized by the coverage of organisms and distributional pattern. Analogies with the coeval reef deposits from the European part of the Tethys have been recognized. Some species, now collected in Oman, were also reported from American and Asian localities.     

A theropod tooth from the Late Triassic of southern Africa

An isolated, large recurved and finely serrated tooth found associated with the prosauropodEuskelosaurus from the Late Triassic part of the Elliot Formation is described here. It is compared to the Triassic thecodonts and carnivorous dinosaurs and its possible affinity is discussed. The tooth possibly belongs to a basal theropod and shows some features similar to the allosauroids. This tooth is of significance, as dinosaur remains except for some footprints and trackways, are poorly known in the Late Triassic horizons of southern Africa.     

Pangea Megasequences of Tethyan Gondwana-margin reflect global changes of climate and tectonism in Late Palaeozoic and Early Triassic times—A review

The maximum concentration of continental crust at the Pangea stage is characterized by a specific depositional sequence generally referred to as the Pangea Megasequence. Extending in time from the Late Carboniferous to the middle of the Triassic, the succession exhibits similar trends across the whole of Gondwana. Invariably, the sequence was initiated by Late Carboniferous to Early Permian glacial and periglacial deposits. Deglaciation occurred in Early Sakmarian time, evidenced by a typical, commonly transgressive facies. The succeeding formations comprise, in ascending order, coal measures, redbeds, some more coal measures and again redbeds with an intercalation of fluviatile sands in the Early Triassic.After deglaciation the basic depositional theme was modified, depending on postglacial adjustments of climate and on the type of regional tectonic regimes. Extension of the tropical climatic belt after deglaciation was one factor that governed the resulting sediment facies. Coal deposition that prevailed in central Gondwana in the Early Permian gave way to dominance of redbeds in the Middle and Late Permian and, in more distal positions, evaporitic deposits were laid down, following deglaciation. Within marine realms, coralline limestones were formed.Within Gondwana the depositional period of the Pangea Megasequence was governed by three distinctive tectonic regimes: collision dominated the Panthalassa margin, transpressional sag controlled the interior basins, and extension and rifting was experienced along the entire Tethyan margin. In the Early Permian, large and complex graben structures commenced to develop between Africa and India (Malagasy Trough) and between India and Australia (West Australian Trough), giving access to Tethyan waters during deglaciation, commencing in the late Early Sakmarian.Rifting along the Tethyan margin commenced in the Early Permian and was associated with active volcanism between Cashmere and Yunnan and in north-western Australia. Spreading of Neo-Tethys and the formation of oceanic crust, leading to the separation of the Cimmerian Blocks from Gondwana, commenced in the late Early Permian and continued into the Triassic. Thus two facies realms developed, an intracratonic rift facies comprising the Cashmere, Lhasa and Baoshan blocks and a facies controlled by detachment, comprising more distal blocks, such as Tengchong, Malay and Sumatra. The present distribution of individual blocks was governed by fold movements of the Himalayan Orogeny, complicated by transpression along the eastern Himalayan Syntaxis.     

Anisian foraminifers from allochthonous limestones of the Tanoura formation (Kurosegawa Terrane, West Kyushu, Japan)

Thirty-five species belonging to 21 genera of foraminifers are distinguished from allochthonous limestone blocks contained within the autochthonous mudstones and sandstones of the Carnian Tanoura Formation, Kurosegawa Terrane of West Kyushu (SW Japan). These blocks are considered to be Anisian in age, based on the occurrence of two foraminifers widely distributed in the Anisian of the Tethyan Realm, Pilammina densa and Meandrospira dinarica; they are associated with Involutinid-like forms, such as Triadodiscus and Aulotortus, and with other foraminifers. The allochthonous limestones are mostly composed of oolites, abundant bioclasts and detrital quartz grains. They are thought to have been redeposited during the Carnian on the shelf slope of the South Kitakami-Kurosegawa Old Land. Palaeogeographically, this terrane was part of the North Gondwana margin, then isolated eastwards before its Early Cretaceous amalgamation with South China. Three foraminiferal species, Triadodiscus eomesozoicus (Oberhauser), Triadodiscus? tanourensis, n. sp., and Triadodiscus? sp. are described from the Anisian allochthonous blocks.     

Jurassic evolution of Southern Hemisphere marine palaeobiogeographic units based on benthonic bivalves

The distribution of benthonic Jurassic bivalve genera in the Southern Hemisphere is analysed here. For this region, palaeobiogeographic units (biochoremas) are quantitatively characterized according to their biologic contents (mainly levels of endemism). Their evolution through time is followed from the latest Triassic to the earliest Cretaceous. The Tethyan Realm is undoubtedly the most mature and persistent through time, with three subordinate units: an Australian unit restricted to the Late Triassic, a North Andean unit, which appears sporadically as an endemic centre, and an East African unit which is recognisable from Bajocian times onwards. From Late Triassic times, a South Pacific Realm has been recognised, with a Maorian Province mostly based on the distribution of monotoid genera. A South Andean unit is also recognisable through most of the Jurassic, and its reference either to the South Pacific unit or to the Tethyan Realm is a matter of debate. Being a transitional biogeographic setting between Tethyan and South Pacific first-order units, it is included in the South Pacific unit due to the common presence of antitropical (didemic) genera. The East African unit is included within the Tethyan Realm during the Jurassic, but during Early Cretaceous times, it splits into two units, one of which was regarded as part of the “South Temperate Realm” by Kauffman. The rank of all these units changed with time. Throughout the Jurassic, the ecotone between South Pacific and Tethyan palaeobiogeographic units fluctuated in position with time. The approximate latitudinal location of the ecotonal boundary area and its shift through time are recognised on the basis of faunal composition along the Andean region.     

THE GENESIS OF CONDENSED SEQUENCES IN THE TETHYAN JURASSIC

Pelagic limestones of the west Sicilian Middle Jurassic are used as type examples in this examination of Tethyan condensed sequences. Two main processes were involved in the genesis of this type of deposit: stratigraphic condensation (minimal sediment input) and reworking. The lack of nannoplankton during most of the Jurassic caused stratigraphic condensation, and the particular environment in which these beds were deposited – that of topographic high – was considerably influenced by currents; thus reworking led to a further reduction in sediment thickness. The presence of algal stromatolites in certain condensed sequences and the traces of boring algae in associated ferromanganese nodules suggest deposition within the photic zone. A maximum depth of 200 metres is inferred. Many features of condensed sequences are comparable with those on Recent seamounts; these include presence of ferromanganese nodules and crusts, mixed faunas, calcarenite lenses, algal biscuits, and evidence of submarine solution and lithification. Jurassic Tethyan condensed sequences can thus be interpreted as ancient seamount deposits.     

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.     

Facies stacking and extinctions across the Triassic–Jurassic boundary in a peritidal succession from western Sicily

An uppermost Triassic–lowermost Jurassic carbonate platform succession, which is 430 m thick, in northwestern Sicily is described with the aim to provide new data on the sedimentological and biological variations across the Triassic–Jurassic boundary in peritidal environments. The studied succession belonged to the rimmed carbonate shelf that developed during the Late Triassic along the margins of the Ionian Tethys. The peritidal sediments consist of meter-scale shallowing-upward cycles formed by subtidal, intertidal, and supratidal facies. Three main informal units are differentiated along the section on the basis of the variations recorded by the subtidal facies. The lower and middle units are attributed to the Rhaetian, on the basis of the common presence of the foraminifer Triasina hantkeni, associated with several benthic foraminifers, such as Aulotortus sinuosus and Auloconus permodiscoides. Megalodontids are particularly abundant and large in the lower unit, whereas they become rare in the middle unit and disappear in the upper unit. The last occurrence of T. hantkeni, along with the disappearance of the benthic foraminifer fauna, and the bloom of the calcareous alga Thaumatoporella parvovesiculifera is assumed as a proxy of the Rhaetian–Hettangian boundary. Recovery biota during the early Jurassic occurs about 20 m upward of the boundary zone, marked by the appearance of benthic foraminifers, such as Siphovalvulina sp. The observed biostratigraphic signature in the studied section is easily comparable to similar Tethyan sections already described from Italy, Greece, and Turkey; thus, it is believed that the faunistic turnover does not reflect local facies variations, in response to changes in the accommodation space of the platform, but regional changes in a more wide area of ocean Tethys.     

Early Triassic peritidal carbonate sedimentation on a Panthalassan seamount: the Jesmond succession,Cache Creek Terrane,British Columbia,Canada

The Jesmond succession of the Cache Creek Terrane in southern British Columbia records late Early Triassic peritidal carbonate sedimentation on a mudflat of a buildup resting upon a Panthalassan seamount. Conodont and foraminiferal biostratigraphy dates the succession as the uppermost Smithian to mid-Spathian. The study section (ca. 91 m thick) is dominated by fine-grained carbonates and organized into at least 12 shallowing-upwards cycles, each consisting of shallow subtidal facies and overlying intertidal facies. The former includes peloidal and skeletal limestones, flat-pebble conglomerates, stromatolitic bindstones, and oolitic grainstone, whereas the latter consists mainly of dolomicrite. The scarcity of skeletal debris, prevalence of microbialite, and intermittent intercalation of flat-pebble conglomerate facies imply environmentally harsh conditions in the mudflat. The study section also records a rapid sea-level fall near the Smithian-Spathian boundary followed by a gradual sea-level rise in the early to mid-Spathian.     

Middle Triassic carbonate deposits and calcareous algae from the Sasca zone (Southern Carpathians,Romania)

Summary The Sasca zone situated in the innermost part of the Getic Domain from the South Carpathians comprises mainly Triassic deposits of Scythian-Anisian (?Ladinian) age that can be ascribed to four different members forming the Sasca Formation. Three of the members consist of carbonate deposits. Their study permitted a brief characterization of the main microfacies types, and especially in the Valea Susara Limestone Member the identification of a relatively rich association of foraminifers and calcareous algae. The assemblage withMeandrospira dinarica, Pilammina densa, Oligoporella pilosa andPoncetella hexaster identified in these limestones indicates a Middle Anisian age (Pelsonian-Lowermost Illyrian). Difficulties arise in differentiating between the forms belonging to theOligoporella-Physoporella group for which a taxonomic revision is necessary. The morphologic characteristics of the three varieties ofDiplopora subtilis allow a splitting into different species.Teutloporella peniculiformis Ott, 1963 is regarded as anomen nudum.     

History of a Late Carboniferous phylloid algal bank complex in northeastern New Mexico

The growth history of a phylloid algal biohermal complex of Late Carboniferous (Westphalian) age, outcropping within the La Pasada Formation in northeastern New Mexico, U.S.A., is described in relationship to paleogeography, biostratigraphy, and microfacies associations. This phylloid algal biohermal complex occurs within typical Late Paleozoic cyclical sediments, in a paleogeographic setting along a narrow shelf margin bordering a deep geosynclinal trough to the northwest. Fusulinid foraminifers suggest that the bioherm is of Middle Pennsylvanian (lower Des Moines) age, whereas the overlying sediments are of middle Des Moines age. Both field and petrographic evidence suggest that the bioherm grew upward from relatively shallow water depths, into extremely shallow water where it probably was subaerially exposed. Biohermal growth appears to have been initiated on a 'hard-ground' surface on which lithified clasts and abundant clusters of robust linoproductid brachiopods served as a foundation. Four major microfacies have been identified from the biohermal complex. These are: (I) phylloid algal wackestones-packstones (mound proper), (2) marly limestones (sediments laterally adjacent to and overlying mound), (3) pelletal-foraminiferal wackestone (partially capping the mound), and (4) crinoidal packstones-grainstones (post-mound). Comparison is made with other surface and subsurface occurrences of phylloid algal complexes of similar age in the southwestern United States.