Tethyan Region Research Articles

A new Eocene lineage of reticulate Nummulites (Foraminifera) from Kilwa district, Tanzania; a place for Nummulites ptukhiani?

Reticulate Nummulites are a widespread and distinctive group of Nummulites, frequently used in biostratigraphy, but their evolution is poorly understood. Studies from the Western Tethys suggest they form a single lineage, the Nummulites fabianii lineage, with an increasing proloculus size over time. This has led to their use as one of the diagnostic taxa for larger benthic foraminiferal biostratigraphy. However, outside of this region, additional taxa have been recorded. The most widely discussed example is Nummulites ptukhiani, which was described from Armenia, whose morphology does not fit with the N. fabianii lineage. This raises the question whether reticulate Nummulites are monophyletic, or the result of multiple independent convergent evolutionary lineages. Here we present data from three newly identified populations of Lutetian to Bartonian reticulate Nummulites from the stratigraphically well-constrained Tanzania Drilling Project records, which shed new light on the ancestry of these aberrant forms. These populations are characterized by extremely large proloculi and unusual morphology. We demonstrate that the populations are consistent with an evolutionary lineage that is morphologically distinct but contemporaneous with the N. fabianii lineage of the Tethys. These forms are remarkably similar in external and internal morphology to the Armenian Nummulites ptukhiani. We therefore refer to them as the N. ptukhiani lineage. The existence of a second lineage of reticulate Nummulites indicates that their evolution is more complex than previously thought and raises questions as to whether they evolved from a common ancestor, or independently. It also underlines the importance of carrying out thorough studies of larger benthic foraminifera with independent stratigraphical control from outside of the Tethyan region to more fully understand their evolution and to enable accurate biostratigraphy.

Parascolymia (Scleractinia: Lobophylliidae) in the Central Paratethys Sea (Vienna Basin, Austria) and its possible biogeographic implications.

Palaeobiogeographical and palaeodiversity patterns of scleractinian reef corals are generally biased due to uncertain taxonomy and a loss of taxonomic characters through dissolution and recrystallization of the skeletal aragonite in shallow marine limestones. Herein, we describe a fossil lobophylliid coral in mouldic preservation from the early middle Miocene Leitha Limestone of the Central Paratethys Sea (Vienna Basin, Austria). By using grey-scale image inversion and silicone rubber casts for the visualization of the original skeletal anatomy and the detection of distinct micromorphological characters (i.e. shape of septal teeth, granulation of septocostae) Parascolymia bracherti has been identified as a new species in spite of the dissolved skeleton. In the recent era, Parascolymia like all Lobophylliidae is restricted to the Indo-Pacific region, where it is represented by a single species. The new species proves the genus also in the Miocene Mediterranean reef coral province. A review of the spatio-temporal relationships of fossil corals related to Parascolymia indicates that the genus was probably rooted in the Eastern Atlantic‒Western Tethys region during the Paleocene to Eocene and reached the Indo-Pacific region not before the Oligocene. The revealed palaeobiogeographical pattern shows an obvious congruence with that of Acropora and tridacnine bivalves reflecting a gradual equatorwards retreat of the marine biodiversity center parallel to the Cenozoic climate deterioration.

Age, nature, and origin of Ordovician Zhibenshan granite from the Baoshan terrane in the Sanjiang region and its significance for understanding Proto-Tethys evolution

This contribution reports on a better understanding of the Proto-Tethys evolution in the Sanjiang Tethyan region of China. The manuscript presents laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon ages, Sr–Nd–Hf isotope systematics, and whole-rock major and trace element of Ordovician magmatic rocks from the calc-alkaline Zhibenshan granite, which formed along the northern margin of East Gondwana. The U–Pb zircon dating of monzogranite from the Zhibenshan granite yields crystallization ages of 466–457 Ma. The monzogranite has Cross–Iddings–Pirsson–Washington normative corundum (3.34%) and is peraluminous with Al2O3/(Na2O+ K2O+CaO) molar ratio of 1.26, similar to S-type granites. All samples are enriched in large ion lithophile elements (LILEs, such as Rb, K, U, and Th) and depleted in high field strength elements (HFSEs, e.g. Nb and Ti). These granites are enriched in light rare earth elements (REEs) and depleted in heavy REEs with strongly negative Eu anomalies (δEu = 0.19–0.24). The initial 87Sr/86Sr ratios range from 0.7118 to 0.7176 and εNd(t) values from −11.3 to −10.3 with Nd model ages of 2114–2037 Ma. Magmatic zircons with early Palaeozoic dates have εHf(t) values ranging from −13.3 to −1.8 and Hf model ages from 2258 to 1537 Ma. These geochemical and isotopic features suggest that the Zhibenshan granite originated from an ancient crustal source. Ordovician granites in the Baoshan terrane represent the southward continuation of the early Palaeozoic granitic belt that extended along the northern margin of East Gondwana, providing important evidence for the evolution of the Proto-Tethyan Ocean.

Biogeography of goby lineages (Gobiiformes: Gobioidei): origin, invasions and extinction throughout the Cenozoic

AbstractAimTo combine a time‐calibrated phylogeny with distributional, fossil and geomorphological data to infer the patterns of lineage origins and biogeography among gobies.LocationGlobal marine areas (Indo‐West Pacific, Western Indian Ocean, Mediterranean, Atlantic and Eastern Pacific) throughout the Cenozoic.MethodsI inferred a molecular phylogeny using beast, simultaneously calibrating nodes for Gobiidae, Gobionellidae and their combined clade. I used that phylogeny, coupled with current range data, to reconstruct historical distributions with the R module BioGeoBEARS under both a dispersal, extinction and cladogenesis (DEC) model and an augmented model including founder effect speciation (DEC+J). I then compared model fits for placing the ancestral node of Gobiidae + Gobiidae at varying reef hotspots throughout the Cenozoic: the West Tethys (Mediterranean), Western Indian Ocean or Indo‐West Pacific.ResultsGoby lineages arose over a 12–13 million year period in the late Eocene, followed by repeated invasions of the Eastern Pacific, Atlantic and Mediterranean from an ancestral Indo‐West Pacific distribution. Optimization with DEC+J is preferred to DEC, but constraining the root of the phylogeny with a West Tethyan (Mediterranean) or Western Indian Ocean distribution does not result in significantly different model fits under DEC+J.Main conclusionsIn Gobiidae, several lineages migrated through the West Tethys to the Atlantic, followed by extinction in the Mediterranean. In contrast, lineages of Gobionellidae in the Mediterranean did not spread beyond the eastern North Atlantic. Gobionellidae invaded the Eastern Pacific by distinct routes in different lineages, either from the Caribbean through the open Isthmus of Panama or around the northern Pacific Rim. Eastern Pacific Gobiidae are younger and derived from tropical Atlantic clades. Although the reconstructed ancestral area of gobies is the Indo‐West Pacific, fossils indicate that gobioids were present in the West Tethys region throughout the Oligocene and Miocene, including taxa that are not known from that area today.

Climate variability during the Carnian Pluvial Phase — A quantitative palynological study of the Carnian sedimentary succession at Lunz am See, Northern Calcareous Alps, Austria

The Middle and Upper Triassic prevailing dry climate was interrupted by a global phase of increased humidity during the Early Carnian, the Carnian Pluvial Phase (CPP). It started at the Julian 1–2 boundary and lasted approximately until the latest Julian or early Tuvalian. In the Tethys this is reflected by a change from limestone deposits to, first, organic rich mudstones and then to siliciclastics. The CPP occurred along the northern rim of the Tethys and is reported from many locations within and surrounding Europe. In this study samples from Lunz am See in Austria were analyzed for palynology and for bulk carbon isotope values covering a 450m thick succession. A known −3‰ bulk organic carbon isotope excursion, possibly as a result of the eruption of large amounts of volcanogenic material, in the Göstling Member and the basal Reingraben Formation has been confirmed. A total of five distinctive palynology assemblages were recognized and correlated regionally. While the under- and overlying formations yield terrestrial and subordinate also marine palynomorphs, the palynoflora of the Lunz Formation is near wholly terrestrial in origin. Climate trends were inferred from multivariate statistical analysis (PCA) of the palynofloral record. Palynomorphs show a general trend from a dry climate during the Julian 1 to wetter conditions during the Julian 2. The wetter conditions were periodically interrupted by shorter periods of dryer climate. In terms of temperature trends the climate was warmer during the early Julian 2 which corresponds with the deposition of the Reingraben Formation, temperature decreased again and remained fairly stable during most of later part of the Julian 2, which corresponds to the deposition of the Lunz Formation. This study correlates with similar observations from other locations from the western Tethys region that support the theory of a wide-ranging to global Carnian Pluvial Phase.

Cenomanian–Coniacian (Upper Cretaceous) bivalves of the Sergipe Basin, Brazil: Order Pholadomyida

Twenty-two species of the bivalve order Pholadomyida, belonging to six genera and seven subgenera of the families Pholadomyidae, Pleuromyidae and Poromyidae are described from the Cenomanian–Coniacian Cotinguiba Formation of the Sergipe Basin, north-eastern Brazil. Eleven species, Pholadomya (Ph.) cf. agrioensis Weaver, Ph. (Ph.) kasimiri Pusch, Ph. (Ph.) nodulifera Munster, Ph. (Ph.) occidentalis Morton, Ph. (Procardia) vignesi Lartet, Pleuromya ligeriensis (d’Orbigny), Pl. servesensis Choffat, Liopistha (L.) aequivalvis (Goldfuss), L. (Psilomya) elongata Stanton, L. (P.) globulosa (Forbes) and L. (Sergipemya) gigantea (J. Sowerby) are recorded from the Sergipe Basin for the fi rst time. The new subgenus Sergipemya of the genus Liopistha, family Poromyidae, is erected on the basis of morphological characters such as numerous commarginal ribs, large and highly infl ated valves, a well-developed rounded umbonal anterior ridge bordering a deep depression on the anterior part, and the presence of two unequal cardinal teeth with a cardinal tear-shaped socket in the left valve. The pholadomyid fauna of Sergipe closely resembles that of other Tethyan regions in western and southern Europe, northern and western Africa and the Middle East. The distribution patterns of the taxa were probably influenced by east–west-directed currents. Southern Tethyan pholadomyids reached western Africa and north-eastern South America via the Trans-Saharan Seaway.

Early Jurassic Trochotomidae (Vetigastropoda, Pleurotomarioidea) from the Neuquén Basin, Argentina

AbstractTrochotomidae is a small but distinctive extinct family of pleurotomarioidean gastropods characterized by trochiform shells with an elliptical trema. Two new species of trochotomids are described from Pliensbachian deposits in the Neuquén Basin, Argentina. The new genus-group namePlacotomais proposed to replace the pre-occupied nameDiscotomaHaber non Mulsant. The record ofTrochotoma(Trochotoma)protonotialisnew species andTrochotoma(Placotoma)neuquensisnew species in the early Jurassic of Argentina extends the paleobiogeographical distribution of the genus (and the family) to the Southern Hemisphere. The new taxa reported here represent a component of the pleurotomarioidean adaptive radiation that took place in the Tethyan region during the earliest Jurassic. They are related to local patch coral reefs of shallow, open-marine paleoenvironments, agreeing with the known habitat of most species of this family. The group was well represented in the Tethyan region during the Mesozoic, especially during the Jurassic, and the new species represent its southernmost occurrence.

Ammonoid diversification in the Middle Triassic: Examples from the Tethys (Eastern Lombardy, Balaton Highland) and the Pacific (Nevada)

The diversity dynamics of the Anisian ammonoids is analyzed in terms of generic richness and turnover rates in one North American (Nevada) and two western Tethyan (Eastern Lombardy, Balaton Highland) regions. Two pulses of diversification are outlined: one in the middle Anisian (Pelsonian) and another near the end of the late Anisian (late Illyrian). The Pelsonian global diversification is interpreted as an effect of global sea-level rise. In the early late Anisian the ammonoid generic richness definitely decreased both in the western Tethys and in Nevada. The latest Anisian peak of ammonoid diversity was low in Nevada, which is explained by the uniform local sedimentary environment and the absence of major global changes. In the western Tethys the late Illyrian diversity peak was very prominent: ammonoid generic richness, turnover and proportion of originations were very high. This explosive peak is interpreted in terms of major changes of two regional environmental factors: coeval volcanic activity and ...

Relationship between Porphyry Copper Occurrences, Crustal Preservation Levels, and Amount of Exploration in Magmatic Belts of the Central Tethys Region

Relationship between Porphyry Copper Occurrences, Crustal Preservation Levels, and Amount of Exploration in Magmatic Belts of the Central Tethys Region

Seep deposits from northern Istria, Croatia: a first glimpse into the Eocene seep fauna of the Tethys region

AbstractThree isolated limestone deposits and their fauna are described from a middle Eocene Flysch succession in northwestern Istria, Croatia. The limestones are identified as ancient methane-seep deposits based on fabrics and characteristic mineral phases, δ13Ccarbonatevalues as low as −42.2 ‰ and13C-depleted lipid biomarkers indicative of methane-oxidizing archaea. The faint bedding of the largest seep deposit, the great dominance of authigenic micrite over early diagenetic fibrous cement, as well as biomarker patterns indicate that seepage was diffusive rather than advective. Apart from methanotrophic archaea, aerobic methanotrophic bacteria were present at the Eocene seeps as revealed by13C-depleted lanostanes and hopanoids. The observed corrosion surfaces in the limestones probably reflect carbonate dissolution caused by aerobic methanotrophy. The macrofauna consists mainly of chemosymbiotic bivalves such as solemyids (Acharax), thyasirids (Thyasira) and lucinids (Amanocina). The middle Eocene marks the rise of the modern seep fauna, but so far the fossil record of seeps of this age is restricted to the North Pacific region. The taxa found at Buje originated during the Cretaceous Period, whereas taxa typical of the modern seep fauna such as bathymodiolin mussels and vesicomyid clams are absent. Although this is only a first palaeontological glimpse into the biogeography during the rise of the modern seep fauna, it agrees with biogeographic investigations based on the modern vent fauna indicating that the dominant taxa of the modern seep fauna first appeared in the Pacific Ocean.

Paleobiogeographic significance of a new ozawainelloid fusulinid Pseudoacutella partoazari n. sp., from the Asselian (lowermost Permian) of Gaduk (Central Alborz, Iran)

The uppermost Carboniferous–Lower Permian Dorud Group that crops out at the Gaduk section of Central Alborz is over 44m thick and includes thick sequences of conglomerate, quartzarenite, calcareous sandstone, oncolitic fusulinid limestone, sandy limestone, sandstone and shale. The Toyeh, Emarat and Shah Zeid formations of this Group were dated as latest Gzhelian to Early Sakmarian. A review of the Asselian fusulinids and smaller foraminifers of Iran emphasizes (1) how the foraminiferal assemblages of Alborz and central Iran differ; (2) why non-Pseudofusulina cannot be a nomen substitutum to Pseudofusulina (even if this latter was often misinterpreted in the Tethyan regions). A new smaller fusulinid Pseudoacutella partoazari n. sp. is described from the Emarat Formation (Asselian) that crops out in the Gaduk area. The palaeobiogeographic significance of Pseudoacutella is discussed, because this genus, which was cosmopolitan from Late Bashkirian to Moscovian, became rare in the Upper Pennsylvanian of the USA and the Carnic Alps, and then, very rare in Lower Permian of Texas, Arizona and Iran.

Multiple Dolomitization Episodes In Deep-Water Limestones of the Triassic Lagonegro Basin (Southern Italy): From Early Reflux To Tectonically Driven Fluid Flow

Abstract Massive dolomitization does not commonly occur in deep-water carbonates. However, this regional study on outcrops and subsurface samples of Triassic Lagonegro basinal carbonates from the southern Apennines fold and thrust belt (Italy) shows that the evolution of the Lagonegro basin was punctuated by two events of massive dolomitization. These processes resulted in two distinct dolomite types, displaying different petrographic and geochemical features. A medium-crystalline and fabric-preservative dolomite in the northern area (Molise, Campagna, and San Fele–Mount Pierno) contrasts with a medium- to coarse-crystalline and fabric-destructive dolomite in the southern area (from Pignola to the high Val d'Agri). Geochemical data (increase in δ18O with respect to typical Late Triassic seawater values, high Sr and low Mn and Fe content, Sr isotopes consistent with Late Triassic seawater) indicate that the dolomite in the northern area is the result of an early replacement caused by a marine and possibly oxidizing fluid during shallow burial. Dolomitizing fluids likely were expelled through reflux from the Norian Apenninic carbonate platform towards the proximal Lagonegro basin. This reflux was promoted by the Norian peculiar paleoceanographic and climatic conditions in the Tethyan region, and affected only the proximal basinal facies. Dolomites in the southern area display a decrease in δ18O compared to Late Triassic seawater values and show lower Sr, higher Mn and Fe contents, and higher Sr isotope ratios compared to the early dolomites of the northern area. Fluid-inclusion microthermometry reveals homogenization temperatures between 70 and 120°C and salinities of 1.9 to 6.4 wt % NaCl eq. for saddle dolomites. These geochemical signatures indicate that the southern area was affected by late diagenetic burial dolomitization, interpreted to be the result of large scale tectonically driven fluid flow during the second compressional phase characterizing the southern Apennines fold and thrust belt emplacement. The dolomite distribution across the Lagonegro basin (northern and southern) is possibly controlled by the paleogeographic distribution of the facies (proximal vs. distal) as well as by their proximity to thrust faults. The Lagonegro case study demonstrates that basinal successions may undergo multiple dolomitization episodes in a manner similar to carbonate platform successions, from early shallow to deep-burial diagenesis. One of the relevant implications is that in areas of restricted oceanographic circulation, during periods of aridity, reflux dolomitization may extend beyond the platform margin, into deep-water carbonates, having the potential to alter their reservoir quality.

Permian-Triassic conodonts from Dajiang (Guizhou, South China) and their implication for the age of microbialite deposition in the aftermath of the End-Permian mass extinction

The widespread microbialites deposition that followed the End-Permian mass extinction in the Tethyan realm have been intensively studied because of the evidence they provide on the nature of this crisis and its aftermath. However, the age of the microbialite event remains controversial. New conodont collection across the Permian-Triassic (P-T) transition from Dajiang (Guizhou Province, South China) in this study enable us to discriminate four conodont zones, in ascending order, they are: Hindeodus parvus zone, Isarcicella lobata zone, Isarcicella isarcica zone and Hindeodus sosioensis zone. The age of microbialite in the P-T transition at the Dajiang Section is considered to be within the Hindeodus parvus zone and thus to clearly post-date the main extinction crisis. Reviewing the age of onset of microbialites throughout the Tethyan regions reveals two different ages: a Hindeodus changxingensis zone age is dominant in south-western and westernmost Tethys, whilst most other regions show microbialite deposition began in the Hindeodus parvus zone. Our investigation also indicates that two conodont changes occur at this time: an increase of hindeodid species immediately following a sequence boundary and the mass extinction, and a phase of extinction losses in the earliest Triassic Isarcicella isarcica zone during highstand development.

Cow sharks (Hexanchiformes) from the Cretaceous deposits of the Crimea

This paper presents descriptions of five species of sharks of the families Hexanchidae and Crassodontidanidae from the Cretaceous deposits of South-West Crimea: Crassodontidanus aff. wiedenrothi (Thies, 1983) (Bolshoy Kermen Mountain, lower Hauterivian), Pachyhexanchus pockrandti (Ward et Thies, 1987) (Bolshoy Kermen Mountain, lower Hauterivian), Notidanodon aff. lanceolatus (Woodward, 1886) (Belaya Mountain, lower – middle Cenomanian), N. cf. lanceolatus (near Maryino Village, middle Aptian), and N. dentatus (Woodward, 1886) (Kremennaya Mountain, lower Cenomanian). The tooth of Crassodontidanus aff. wiedenrothi is close in morphology to those of C. wiedenrothi from the Jurassic of Germany. Pachyhexanchus pockrandti is the second record of this species in the Tethys region. Representatives of Notidanodon aff. lanceolatus are sharply different from other species of this genus in tooth morphology; this taxon is, likely, an ancestral form for the family Heptranchidae.

Fossil Sirenia of the West Atlantic and Caribbean region. Ix. Metaxytherium albifontanum, sp. nov.

ABSTRACT We describe a new species of the halitheriine dugongid genus Metaxytherium from the late Oligocene of Florida and South Carolina. The new species is represented by cranial and postcranial material, including parts of the axial and appendicular skeleton. Metaxytherium albifontanum, sp. nov., differs from other species of Metaxytherium by the following unique combination of plesiomorphic and derived characters: posterior end of nasal process of premaxilla broad and flat relative to what is observed in most other members of the genus (somewhat resembling M. subapenninum); ventral extremity of jugal under posterior edge of orbit (character 85[1]) (shared with M. krahuletzi); exoccipitals separated in dorsal midline (character 66[1]) (shared with all other species in the genus, except some M. krahuletzi); and innominate with acetabulum (nearly lost or lost in M. crataegense, M. floridanum, M. serresii). This new species was sympatric with two dugongines, Crenatosiren olseni and Dioplotherium manigaulti. The small tusks and cranial morphology of M. albifontanum, sp. nov., indicate that it was likely a consumer of small seagrasses. Our phylogenetic analysis is consistent with previous ones in placing Hydrodamalinae within a paraphyletic Metaxytherium spp. and placing the Metaxytherium spp. + Hydrodamalinae clade as the sister group to Dugonginae. Metaxytherium albifontanum, sp. nov., is the oldest known member of its genus; this might indicate that the group originated in the West Atlantic and Caribbean region and later dispersed to the Old World Tethys region. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP.

Ostracods of the genus Palaeocytheridea Mandelstam in the Middle and Upper Jurassic of Europe: 3. Stratigraphy and paleobiogeography

The analysis of distribution of endemic and cosmopolitan ostracods of the genus Palaeocytheridea shows that, in the Bajocian and Bathonian, the Tethyan and Boreal-Atlantic regions of Western and Eastern Europe developed in partial isolation, while beginning from the middle of the Lower Callovian, these parts of the European paleobasin were connected. For the Middle Jurassic of Western and Eastern Europe and, in particular, for Ukraine, the ostracod zones are recognized based on stratigraphic distribution of species of the genus Palaeocytheridea.

Mesozoic‐Cenozoic Multi‐Stage Intraplate Deformation Events in the Langshan Region and their Tectonic Implications

AbstractIn the Langshan region, northwestern China, marked multi‐stage intraplate deformation events have occurred since the Mesozoic, including (1) northeast‐striking ductile left‐lateral strike slip during the Middle‐Late Triassic, which is closely related to the collision between the North China and the Yangtze plates; (2) top‐to‐the‐southeast thrust with northwest‐southeast trending maximum compression during the Late Jurassic; (3) nearly eastward detachment during the Early Cretaceous; (4) top‐to‐the‐northwest thrust with northwest‐southeast trending maximum compression during the Late Cretaceous and Early Cenozoic; (5) northeast‐striking brittle left‐lateral strike slip with nearly north‐south trending maximum compression; and (6) northwest‐southeast extension during the Middle‐Late Cenozoic. All these deformation events belong to the intraplate deformation across the entire Central Asian region and respond to the tectonic events along the plate boundaries or deep tectonics. The structures developed in early events in the crust were the most important factors controlling the later deformation styles, and few new structures have later developed. Based on previous research and our results, the paleostress inversion in the Langshan region shows that the Mesozoic intraplate deformations in the study region mainly resulted from the tectonic events from the Paleo‐Pacific region and have no or a weak relation to the Tethys region. During the Late Jurassic, the maximum compression from the Mongolia‐Okhotsk region cannot be excluded. The Langshan region is the bridge between southern Mongolia and the western Ordos tectonic belt and is thus important to understand the nature and relationship between both regions.

Carbon isotope stratigraphy of Torinosu‐type limestone in the western Paleo‐Pacific and its implication to paleoceanography in the Late Jurassic and earliest Cretaceous

AbstractCarbon isotope stratigraphy of the Late Jurassic and earliest Cretaceous was revealed from Torinosu‐type limestone, which was deposited in a shallow‐marine setting in the western Paleo‐Pacific, in Japan. Two sections were examined; the Nakanosawa section of the late Kimmeridgian to early Tithonian age (Fukushima Prefecture, Northeast Japan), and the Furuichi section of the late Kimmeridgian to early Berriasian age (Ehime Prefecture, Southwest Japan). The age‐model was established using Sr isotope ratio and fossil occurrence. The limestone samples have a low Mn/Sr ratio (mostly <0.5) and lack a distinct correlation between δ13C and δ18O, indicating a low degree of diagenetic alteration. Our composite δ13C profile from the two limestone sections shows three stratigraphic correlation points that can be correlated with the profiles of relevant ages from the Alpine Tethyan region: a large‐amplitude fluctuation (the lower upper Kimmeridgian, ∼152 Ma), a positive anomaly (above the Kimmeridgian/Tithonian boundary, ∼150 Ma), and a negative anomaly (the upper lower Tithonian, ∼148 Ma). In addition, we found that δ13C values of the Torinosu‐type limestone are ∼1‰ lower than the Tethyan values in the late Kimmeridgian. This inter‐regional difference in δ13C values is likely to have resulted from a higher productivity and/or an organic burial in the Tethyan region. The difference gradually reduces and disappears in the late Tithonian, where the Tethyan and our δ13C records show similar stable values of 1.5–2.0‰. This isotopic homogenization is probably due to changes in the continental distribution and the global ocean circulation, which propagated the 13C‐depleted signature from the larger Paleo‐Pacific to the smaller Tethys Ocean during this time.

Late Triassic ammonoid Sirenites from the Sabudani Formation in Tokushima, Southwest Japan, and its biostratigraphic and paleobiogeographic implications

AbstractDiscovery of Sirenites senticosus (Dittmar) in the upper part of the Sabudani Formation of the Kurosegawa Belt, Kito area, Tokushima Prefecture, Japan, establishes a late Early Carnian age for this part of the stratigraphic unit. Because S. senticosus was mainly distributed in the Tethyan region, its occurrence provides evidence that Late Triassic ammonoids of Japan had strong affinities with those of the Tethyan faunas. This finding clearly differs from the biogeographic distribution of contemporary bivalves in the region, which are referred to as the Kochigatani bivalve faunas, and show strong affinities to faunas of the Boreal region.

Brachiopods, fusulines and palynomorphs of the Mengkarang Formation (Early Permian, Sumatra) and their palaeobiogeographical significance

Brachiopods, fusulines and palynomorphs from the Lower Permian Mengkarang Formation (Sumatra, Indonesia) have been studied in order to establish the palaeogeographical position and the palaeolatitude of the West Sumatra Block. The position of the West Sumatra Block within the Palaeo-Tethys and Panthalassa oceans and its relationships to their marginal landmasses, in particular the Gondwana supercontinent and the Cathaysian palaeogeographical area, currently is uncertain.Brachiopods, fusulines and palynomorphs of the Lower Permian Mengkarang Formation were analysed to test the Gondwanan versus Cathaysian affinity of the West Sumatra Block. Six genera and two species of fossil brachiopods were identified: Neochonetes (Neochonetes) carboniferus (Keyserling, 1846), Marginifera (Arenaria) sp. ind., Reticulatia sp. ind., Stereochia aff. S. irianensisArchbold, 1981a, ?Protoanidanthus sp. ind., Cancrinella sp. ind., and an undetermined genus and species of the subfamily Toryniferinae. Multivariate analysis of the available brachiopod data including those from the Mengkarang Formation identified two groups, the first comprising Iran, Yukon, the Urals and West Sumatra, the second comprising South Thailand, Baoshan, central Afghanistan, Karakoram, India, West and East Australia, indicating that Lower Permian brachiopods from West Sumatra are best grouped with warm water taxa rather than with cold water taxa from the Gondwanan-Perigondwanan region.Six fusuline species belonging to five genera were identified from six limestone samples: Eostaffella sp., Schubertella sp., Pseudoschwagerina cf. afghanensisLeven, 1971, Pseudoschwagerina meranginensisThompson, 1936, Eoparafusulina ?haydeniLeven, 1971, Pseudofusulina rutschiThompson, 1936. The fusuline fauna is rather poor in terms of generic composition as it is composed mainly by widespread genera but, in a broad sense, the Lower Permian West Sumatra fauna is typical of palaeo-tropical Tethyan regions because of the common occurrence of large schwagerinids.Only one sample level in the Mengkarang Formation yielded abundant palynomorphs, dominated by Laevigatosporites spp. indeterminate bisaccate pollen, Florinites florini Imgrund, 1960 and Convolutispora sp. This assemblage is very different from coeval assemblages of the Gondwanan region, northern Palaeotethyan regions of Kazakhstan, and parts of western Europe and the Intrasudetic Basin, but has more affinity with the Cathaysian phytogeographic province as represented in northern China, Turkey and northern Iraq.