REVUE DE MICROPALEONTOLOGIE最新文献

The Araripe, Jatobá and Tucano Norte basins, northeast Brazil, have an extensive fossil record. Among the groups found, are the ostracods, which have great relevance for this region due to their significant occurrence and wide diversity during the Upper Jurassic–Lower Cretaceous. These basins contain the rift process record of the Gondwana breakup for the posterior installation of the South Atlantic Ocean, data reinforced by the correlated ostracod non-marine fauna with some African basins. This paper presents a detailed taxonomic and biostratigraphic study of the ostracod species recovered from outcrops from these three basins. A total of 29 species were identified, distributed in eight genera: Theriosynoecum pricei, Theriosynoecum sp. cf. T. sp. 6, Cypridea acicularis, Cypridea ambigua, Cypridea indiennensis densipunctata, Cypridea sellata, Cypridea semilunaris, Cypridea vianai, Cypridea paraibensis, Cypridea (Morinina?) bibullata bibullata, Cypridea (Morinina?) bibullata tribullata, Cypridea sp. cf. C. (Morinina?) langei, Cypridea sp. cf. Cypridea miritiensis, Cypridea sp. 1, Paracypridea brasiliensis, Paracypridea quadrirugosa quadrirugosa, Paracypridea ex. gr. elegans, Salvadoriella redunca posterior, Reconcavona? jatobaensis, Reconcavona striata, Reconcavona striatula, Reconcavona swaini, Reconcavona aff. R.? polita, Reconcavona sp. cf. R. triebeli, Reconcavona sp.1, Reconcavona sp.2, Rhinocypris sp.1, Darwinula? sp. cf. D. oblonga, Alicenula sp. cf. Alicenula leguminella. From the identification of these species, it was possible to infer a stratigraphic range from Tithonian to Barremian, which corresponds to the local RT-001 to RT-007 biozones.

In this article is analysed for the first time the ostracods association from the Early Pliocene (MPL 3 Zone) sandy clayey silt outcropping, along the shore, to the left of the Nocella river mouth (Castellammare Gulf, NW Sicily). The ostracods association is abundant and well preserved and is referred to a not very deep paleoenvironment of the Continental Shelf. Some species, belonging to the genera Cytherelloidea, Eucytherura, Pseudocytherura, Aurila, Pachycaudites, Tenedocythere, Capsacythere, Echinocythereis have been identified, described and figured here for the first time.

The ostracod fauna of two late Messinian stratigraphic sections in eastern Tunisia have been analysed. The first section (Salakta-SAL section), is located south of Cape Bon, the second (Wadi el Kebir–OK section) in the Sahel region. In both sections the shallow marine ostracod fauna is dominant but have also been found taxa referable to the Lago Mare facies. From the shallow water marine levels, several ostracods taxa were recognized; some of which, due to their morphological particularities, have been described as new species. In a first contribution (Sciuto et al., 2021) have been described twenty-four taxa. Now, a second series of sixty shallow water marine ostracod taxa coming from the sedimentary levels of the Oued El Bir Formation, considered unknown or little known until now are systematically listed below, described and illustrated. They belong to the genera Cytherella, Bairdia, Cushmanidea, Cytheridea, Cyamocytheridea, Miocyprideis, Aurila, Cimbaurila, Peteraurila, Urocythere, Callistocythere, Leptocythere, Mediocytherideis, Loxoconcha, Loxoconchissa, Sagmatocythere, Neomonoceratina, Carinocythereis, Chrysocythere, Cistacythereis, Keijella, Mutilus, Neocytheretta, Okadaleberis, Verrucocythereis, Cytheretta, Xestoleberis.

The Ayios Photios Group in SW Cyprus represents a deep-water slope or base of slope sequence that was accumulated on a Mesozoic margin of the Mediterranean Tethys. The Episkopi Formation is an essentially radiolaritic sequence, the age of which was previously considered to range between the Callovian and the Valanginian. A moderately well preserved (PI 4-5) radiolarian assemblage was extracted after laboratory leaching with diluted hydrofluoric acid of a radiolarian chert bed south of the village of Episkopi. Based on the co-occurrence of Bernoullius rectispinus leporinus Conti & Marcucci, Hexasaturnalis tetraspinus (Yao) and Theocapsommella cucurbiformis (Baumgartner), the assemblage is correlated with the Middle Bathonian (Unitary Association Zone 6). Our results extend downwards the known age range of radiolarites of the Episkopi formation and reduce the previously known range of depositional hiatus with the underlying Upper Triassic formations of the Ayios Photios Group.

Calcareous nannofossil biostratigraphy of Alaka well was carried out to identify the biohorizons that exist, ultimately for biozonation, chronostratigraphy and geologic age calibration of the studied interval. The study involved sedimentology analysis, gamma ray description and preparation of two hundred and twelve (212) ditch cuttings, sampled at 9.144m intervals for the study of calcareous nannofossils on smear slides. Sedimentology and gamma ray analyse showed deposition within shallow marine paleoenvironments with alternating minor transgressions in a generally progradational delta setting, accounting for the low calcareous nannofossil occurrences. The calcareous nannofossil assemblages recovered from the slide preparations consist of fourteen (14) species, comprising nine (9) long ranged, non-stratigraphic significant forms and five (5) short ranged stratigraphic significant forms. The biohorizons identified included Base (B) occurrence of Catinaster coalitus at 3578m; Discoaster hamatus at 2874m; Top (T) occurrence of Discoaster hamatus at 2518m and Base absence (Ba) of Reticulofenestra pseudoumbilicus at 2280m. Other biohorizons included Top occurrence (T) of Discoaster bollii at 2435m and Discoaster deflandrei at 3578m respectively. The biohorizons defined boundaries between biozones and showed that the studied interval penetrated four biozones from CNM11 to CNM14 of Backman et al. (2012), NN7 to NN10 of Martini (1971) and CN5b to CN8a of Okada and Bukry (1980). The geologic age of the studied interval ranged between about 11.60 Ma within CNM11/NN7/CN5b zone to about 8.80 Ma within CNM14/NN10/CN8a zone, the standard chronostratigraphy lies within Tortonian stage. Two chronostratigraphic surfaces were mapped in the studied section and comprised one global maximum transgression at 3514m corresponding to 10.5 Ma maximum flooding event, and one localized maximum transgression at 2847m corresponding to 9.5 Ma maximum flooding surface, separated by sea-level lowstand mapped at 3331m and corresponding to 10.35 Ma.

An inventory of 35 species of ostracods (Crustacea) recovered from sediment samples from a shallow embayment nearby the Mu Koh Phetra National Park in the southwestern coast of Peninsular Thailand, Andaman Sea is given. Most of the species are well-known from the Indo-Pacific area and some others are kept in open nomenclature or compared to already know species because because only few specimens were found. Several species may be new to science but have also to be kept in open nomenclature until new material is obtained. The very abundant specimens of this assemblage are mainly disarticulated valves. This contribution adds to our knowledge of the distribution of ostracods in the Andaman Sea and the degree of ostracod relationship between the Indonesian, Indian and West Pacific areas.

Resumé

Un inventaire de 35 espèces d'ostracodes (Crustacea) provenant de sédiments d'une baie peu profonde près du Parc National Mu Koh Phetra sur la côte sud-ouest de la péninsule de Thïlande, Mer d'Andaman, est donné. La plupart des espèces sont bien connues de la zone Indo-Pacifique et certaines sont conservées en nomenclature ouverte ou comparées à des espèces déjà connues en raison du faible nombre de spécimens collectés. Plusieurs espèces semblent nouvelles mais sont aussi conservées en nomenclature ouverte jusqu’à l'observation de nouveau matériel. Les très abondants spécimens qui composent cet assemblage sont principalement des valves désarticulées. Cette contribution accroit notre connaissance de la distribution des ostracodes dans la Mer d'Andaman et de la relation entre les ostracodes des zones indonésiennes, indiennes et ouest-pacifiques.

Palynomorphs from the Toarcian and Aalenian Djigiat Formation of Karachay-Cherkessia in the Kuban River Basin (North Caucasus, southwest Russian Federation) are reported for the first time. Five samples carefully selected for their biostratigraphical content were studied to document the palynological assemblages. Four samples (1, 2, 3, 4) were collected from pieces of rock with key index ammonite specimens, and sample 5 comprises fragments of ammonite shells from a sideritic concretion. Three of these samples (4, 2 and 1) yielded relatively abundant and diverse aquatic microplankton (acritarchs, dinoflagellate cysts, prasinophytes and zygnematalean algae) and terrestrial palynomorphs (pollen and spores); the remaining two samples (3 and 5) were less productive and contained fewer than 50 palynomorph specimens. The study of the dinoflagellate assemblages provided characteristic and key information. These are the uppermost Toarcian Nannoceratopsis Assemblage and the uppermost Toarcian to lowermost Aalenian Parvocysta Suite Assemblage. The former is overwhelmingly dominated by Nannoceratopsis with sparse numbers of the Parvocysta suite, and the latter yielded more diverse and common specimens of Parvocysta and its relatives. This is consistent with the hypothesis that the Parvocysta suite migrated from the Boreal Realm further south into Laurasia during the Toarcian. Certain dinoflagellate cysts such as Mancodinium semitabulatum and Scriniocassis spp., which are typical of Europe and much of Greater Laurasia are absent. Composition of the pollen and spores proved relatively out to be monotonous, and cannot be subdivided. However, in general, the composition of the assemblages of spores and pollen is consistent with the Toarcian–Aalenian transition.