REVUE DE MICROPALEONTOLOGIE最新文献

Triassic marine ostracods from south-eastern Asia are poorly known, leading to a profound misreading of their biodiversity on the eastern Tethys margin during this critical interval of the history of life. Here we describe the first Late Triassic ostracod assemblage from the Khao Pathawi Limestone exposed in Uthai Thani Province, central Thailand. It comprises 22 relatively poorly preserved species, their taxonomy is discussed and adds to the scientific understanding of marine ostracods during the Late Triassic. The noticeable lack of the archetypal Triassic Metacopina and ornate Bairdiidae is discussed. Although several of the recovered species might be new to science, it is premature to describe them. Two species are shared with Rhaetian communities described from western and southern Tethyan localities and additional shared species may be confirmed in the future, illustrating the largescale distribution of ostracod taxa during the Late Triassic. Overall, the ostracod assemblage described here is in line with the Norian-Rhaetian age proposed for the Khao Pathawi Limestone.

Palynomorphs and benthic foraminifers are reported from the Upper Holocene Bangkok Clay Formation at a whale-fall excavation site in Samut Sakhon Province, located 15 kilometers from the shoreline of the Gulf of Thailand. The aim of this research is to interpret the paleoenvironment of the whale-trapped layer using bioindicator assemblages. Twenty-two palynomorphs are identified. The palynomorphs are composed of tropical plants and categorized based on their ecological communities into five groups: mangrove, back mangrove, floodplain, terrestrial, and ferns. Of these, mangrove and floodplain pollen assemblages are dominant. The pollen was transported via aeolian and fluvial systems to deposit in the delta system, then wave and tide processes dispersed them to the deeper part of the sea floor. The foraminiferal assemblage is dominated by marine ammonioids and miliolids without agglutinated forms, representing a shallow marine setting with low freshwater influence. The assemblages of foraminifers together with ostracods, gastropods and diatoms suggest sedimentary deposition in shallow subtidal marine environments, where salinity varied from slightly brackish to normal. The terrigenous sediment influx was high; the depositional environment is likely to be the distal part of a prodelta.

We report for the first time a rich and well-preserved marine ostracod and foraminifera association from lower Pleistocene fossiliferous sandstones of the Mida Section (Cap Bon, NE Tunisia).

Micropalaeontological analysis of nine samples taken along an eight-meter exposure revealed 46 ostracod species belonging to 34 genera, 15 species of benthic foraminifera belonging to 14 genera and 8 species of planktonic foraminifera belonging to 4 genera. The ostracod association enabled us to draw a palaeoenvironmental reconstruction of this area during the Gelasian to Calabrian time, highlighting a regressive cycle from circalittoral to shallow infralittoral palaeoenvironments. Planktonic foraminifera were used to constrain the age of the section to the end of Gelasian-beginning of Calabrian. Moreover, the discovery of Bythocythere turgida in the lower part of the section allowed to infer that these sandstones were deposited during the early Pleistocene cold periods.

Well-preserved and diverse radiolarian assemblages were recovered from a continuous 95 m-thick Lower Jurassic succession of grey siliceous limestone and marl on Mount Rettenstein (Northern Calcareous Alps, Austria). A total of seven radiolarian samples across the Late Sinemurian–Early Pliensbachian boundary were studied – five samples were assigned to the Upper Sinemurian and two samples to the Lower Pliensbachian. In total, 188 radiolarian species have been identified. In this article, we present 90 species and 33 genera belonging to the order Nassellaria. One genus and five species are described as new: Katroma hasta Cifer nov. sp., Tipiforma missoniae Cifer nov. gen. nov. sp., Trexus rotundus Cifer nov. sp., Wrangellium mediterraneum Cifer nov. sp., and Zhamoidellum spinosum Cifer nov. sp. In the Sinemurian, the most abundant nassellarian genera are Droltus, Parahsuum and Saitoum. The Pliensbachian yields an entirely different nassellarian assemblage dominated by the genera Zhamoidellum and Lantus. Compiled stratigraphic and geographic ranges as well as a synonymy, descriptions and remarks are provided.

Non-marine ostracods from the Upper Cretaceous of Southern Hemisphere (South America, Africa and India) are studied and discussed for the purpose of establishing a biostratigraphy scheme and their paleogeographic distribution. The paleogeographic analysis performed here reveals ten distinct groupings of species: (1) Neuquén and Paraná basins (Brazil) are characterized by Ilyocypris riograndensis, Neuquenocypris minor, Neuquenocypris tenuipunctata, Wolburgiopsis vicinalis and Vecticypris aff. punctata; (2) Wolburgiopsis neocretacea is characteristic of Los Llanos Formation (Sub-Andean Basin, Argentina) and Neuquén (Argentina) and Parana basins (Brazil); (3) Ilyocypris triebeli is characteristic of Sub-Andean Basins (El Molino Formation, Bolivia; Los Llanos, Ciénaga del Rio Huaco formations, Argentina), and Yacoraite formations (Salta Basin); Neuquén (Argentina), Paraná and Campos basins (Brazil): Ilyocypris triebeli; (4) Neuquén (Argentina), Paraná and Santos basins (Brazil): Fossocytheridea lobulata; (5) Paraná, Santos (Brazil), Congo (R. D. Congo) basins and Lameta Formation (India): Stenocypris cylindrica; (6) Paraná (Brazil) and Congo (R. D. Congo) basins: Paracypria makawensis and Species “K 530 b” Grekoff, 1960; (7) Yacoraite Formation (Salta Basin) and Neuquén Basin (Argentina), Paraná (Brazil) and Congo (R. D. Congo) basins: Ilyocypris argentiniensis; (8) Neuquén (Argentina), Paraná (Brazil) and Congo (R. D. Congo) basins: Alicenula kwangoensis; (9) Paraná Basin (Brazil) and Lameta Formation (India): Candona chuiensis, Cypridopsis huenei, Paracandona jabalpurensis and Paralimnocythere hasuii; (10) Paraná (Brazil), Congo (R. D. Congo) basins and Lameta Formation (India): Periosocypris megistus. Other generic correlations, especially the genera Wolburgiopsis, Neuquenocypris, Virgatocypris, Altanicypris and Talycypridea, reinforce this paleobiogeographical similarities and a Campanian-Maastrichtian age to the Bauru Group (Paraná Basin) and the Kwango Series (Congo Basin), whose age was still in need of refinement.

The present study represents the first attempt to described foraminiferal fauna of the Gucuo Locality and is among the first work to illustrate the Upper Jurassic to Lower Cretaceous benthic foraminifers of South Tibet. The material consists in a combination of unpublished data on the Gucuo Section and published data on the Gyangze; Weimei, and Bandingsi sections.

A total of 239 specimens have been currently recorded in the Upper Jurassic to Lower Cretaceous Menkadun and Gucuo formations of the Gucuo locality. To facilitate further researches on foraminifers from the Tethyan Himalayas, a total of 59 species from 38 genera have currently been repertory and described. Among the recorded specimens, a few species are significant biostratigraphic markers used to identify and constrain the age of four foraminiferal assemblages. The Textularia aff. haeusleri assemblage contains a few numbers of agglutinated species very similar to the one described in the Oxfordian to Kimmeridgian Nupra Formation of the Thakkola Region. The Tithonian Trochammina quinqueloba assemblage is a widespread biostratigraphic horizon recorded in both southern and northern parts of South Tibet, as well as in the Indian and the Proto-Atlantic oceans. The Berriasian to Valanginian Trochammina abrupta assemblage contains typical Early Cretaceous foraminifers. It confirms the Jurassic/Cretaceous boundary should be delineated at the base of the shale Unit of the Gucuo Formation, although it was previously attributed to the base of the volcaniclastic sandstone units using ammonite data. This latest being currently associated to the Valanginian to Hauterivian Ammobaculites crepinae–Textularia bettenstaedti foraminiferal assemblage.

A palaeoecological reconstruction along a southwest to northeast transect of South Tibet, Himalayas, is proposed to understand the composition and dynamic of foraminiferal assemblages along with palaeoenvironmental changes. The morphogroup approach has been selected as the best methods to illustrate both sea-level and oxic changes. The northern tectonic zone of South Tibet is associated with the abundance of deep-water agglutinated foraminifers, which suggests a deep environment beyond the shelf break. The southern tectonic zone of South Tibet is rich in typical species of shallow environment and was located on the neritic shelf. The morphogroup analysis reveals localized, periodic disaerobic conditions on the sea-floor. The Jurassic to Cretaceous Boundary interval was associated with a drop of the sea-level, whereas the rise in diversity and abundance of marginal-sea taxa during the Valanginian to Hauterivian times underline a higher sea-level and a pulse in the development of epeiric seas in the southern part of South Tibet.

The ostracod genus Liuzhinia has been reported from Permian and Triassic marine deposits mainly from the Tethyan area but its classification and history remain obscure. Here we report on the discovery of a rare steinkern of Liuzhinia antalyaensis from the Early Triassic of South China bearing the first known adductor muscle scars, allowing for first insights into its supra-generic classification. We demonstrate that Liuzhinia does not belong to Bairdiidae and propose that the observed muscle scars could illustrate ancestral characters of Paracyprididae or Bythocyprididae. We summarize the diversity of Liuzhinia through time, including the newly described Liuzhinia phetchabunensis Forel & Chitnarin sp. nov. from the Middle Permian of central Thailand, and discuss its geographical distribution and environmental preferences over its stratigraphical range.

On the bottom of the circalittoral zone of the Mediteranean Sea, prevalently calcareous algae, and subordinately bryozoans, sponges and serpulids give rise to bioconstructions called Coralligenous (algal reef). It with different aspects, mostly columnar or dome-shaped, and different zoo-phitological compositions represent a true biodiversity hot spots on the sea bottom. Ostracod and foraminifer do not participate directly in the construction of the reef but they can contribute significantly to the increase in its degree of biodiversity. The present study wants to be the first attempt to analyze the composition and structure of the microfaunas associated with bioconstructions in an area located along the Ionian coast of SE Sicily offshore Marzamemi (SR, Italy). For this purpose, seven samples, picked up from the surface of the bioconstructions, were collected between 33 and 37 m depth using the sorbona sampling device. Living ostracod associations include 22 taxa: clearly dominant are the specimens belonging to the genus Xestoleberis, followed by the genera Neonesidea, Tenedocythere, Aurila, Loxoconcha, Urocythereis; poorly represented are the genera Carinocythereis, Paradoxostoma and Polycope. Foraminifers associations are almost exclusively represented by benthic phytal taxa and include over 3700 specimens belonging to 130 different taxa. The families quantitatively prevalent, both in terms of richness of species and abundance, are Elphidiidae, followed by Hauerinidae, Cibicididae, Ammoniidae, Homotrematidae, Planorbulinidae, Textulariidae, Cribrolinoididae, Asterigerinatidae, Rosalinidae, Spiroloculinidae and Globigerinidae that are subordinate, while little represented are Astrononionidae, Haplophragmoididae, Polymorphinidae, Ammodiscidae, Ellipsolagenidae, Spirillinidae etc.

A small-sized orbitolinid was originally reported as Coskinolinoides cf. texanus Keijzer from Cenomanian carbonates of western Greece in the early seventies, later described as the new species Paracoskinolina fleuryi Decrouez and Moullade. However, its internal test structure does not fit the characteristics of the genus Paracoskinolina Moullade emend. Arnaud-Vanneau. The original generic assignment is re-instated herein, but its more complex marginal zone does not allow for assignment to Coskinolinoides texanus described from the middle–upper Albian of Texas. Coskinolinoides fleuryi (Decrouez and Moullade) comb. nov., becoming the second nominal species of the genus, shows an unusual broad and dispersed distribution (Senegal, Tunisia, Spain, Greece, Philippines) with stratigraphic records encompassing the latest Aptian?–Albian to early Cenomanian interval. Despite the present contribution, the genus Paracoskinolina still contains additional species that need taxonomic revision.

A new ostracod association, referred to the Early Pleistocene on the basis of the nannoplancton analysis, is studied and described. It comes from the so-called “Agira marls” outcropping in contrada Santa Venera, SW of the Agira town (Central Eastern Sicily). The ostracod fauna is composed by 39 species, 11 species being here proposed and described as new: Eucytherura sanctavenerae n. sp., Aurila seguenzai n. sp., Aurila diodoroi n. sp., Cimbaurila ramdohri n. sp., Tenedocythere eleonorae n. sp., Loxoconcha pokornyi n. sp., Paracytheridea longicristata n. sp., Cistacythereis oertlii n. sp., Costa agyrina n. sp., Echinocythereis hartmannii n. sp. and Tegmenia mariasophiae n. sp. The remaining are known species or left in open nomenclature.