Dating the Tethyan Ocean in the Western Alps with radiolarite pebbles from synorogenic Oligocene molasse basins (southeast France)

For the first time in the Western Alps, radiolarite pebbles collected from Tertiary foreland molasse conglomerates are treated for microfossil extraction and dated. Among forty pebbles collected in the field, seven of them released diagnostic radiolarian assemblages ranging in age from Late Bajocian?CEarly Callovian to Middle Oxfordian?CEarly Tithonian. These ages overlap previous biochronological data obtained from in situ localities of the Schistes Lustrés Piemont zone of the French-Italian Alps and triple the number of diagnostic radiolarite samples known so far in this segment of the chain. The diagnostic pebbles are characterized by low grade metamorphism, showing that some eroded thrust-sheets from the oldest parts of the ocean escaped any tectonic burial during the Alpine convergence. Mixing of low and high-grade radiolarites, mafics and ultramafics pebbles implies that various ocean-derived units were exposed. This tectonic scenario involves tight refolding and severe uplift of the Eocene subduction wedge in the Early Oligocene.     

Sequence stratigraphy of the Lower Cenomanian Bahariya Formation, Bahariya Oasis, Western Desert, Egypt

The Lower Cenomanian Bahariya Formation corresponds to a second-order depositional sequence that formed within a continental shelf setting under relatively low-rate conditions of positive accommodation (< 200 m during 3–6 My). This overall trend of base-level rise was interrupted by three episodes of base-level fall that resulted in the formation of third-order sequence boundaries. These boundaries are represented by subaerial unconformities (replaced or not by younger transgressive wave ravinement surfaces), and subdivide the Bahariya Formation into four third-order depositional sequences.

The construction of the sequence stratigraphic framework of the Bahariya Formation is based on the lateral and vertical changes between shelf, subtidal, coastal and fluvial facies, as well as on the nature of contacts that separate them. The internal (third-order) sequence boundaries are associated with incised valleys, which explain (1) significant lateral changes in the thickness of incised valley fill deposits, (2) the absence of third-order highstand and even transgressive systems tracts in particular areas, and (3) the abrupt facies shifts that may occur laterally over relatively short distances. Within each sequence, the concepts of lowstand, transgressive and highstand systems tracts are used to explain the observed lateral and vertical facies variability.

This case study demonstrates the usefulness of sequence stratigraphic analysis in understanding the architecture and stacking patterns of the preserved rock record, and helps to identify 13 stages in the history of base-level changes that marked the evolution of the Bahariya Oasis region during the Early Cenomanian.     

A fossiliferous resin from the Cenomanian of the Paris and Aquitanian basins of northwestern France

The discovery of a Cenomanian fossiliferous resin at different localities in the Paris and Aquitanian basins of northwestern France is described. The abiotic peculiarities and methodological difficulties are mentioned and evidence for the following arachnid and insect orders given: Phalangiida, Araneae; Blattariae, Isoptera, Psocoptera (?), Heteroptera, Planipennia, Coleoptera, Hymenoptera, Lepidoptera and Diptera. Biostratonomic and palaeoecological implications are discussed.     

Integrated stratigraphy across the Aptian/Albian boundary at Col de Pré-Guittard (southeast France): A candidate Global Boundary Stratotype Section

The outcrop of the Marnes Bleues at the Col de Pré-Guittard, 11 km north of the village of Rémuzat in the Départment of Drôme in southeastern France is probably the most intensively studied succession spanning the Aptian/Albian boundary interval. Following the rejection of the proposed GSSP for the base of the Albian Stage (based on the first occurrence of the ammonite Leymeriellla tardefurcata in the section at Le Pillart, Tartonne, Alpes-de-Haute Provence), we re-visit the Pré-Guittard section. A new candidate GSSP defined by the first occurrence of the planktonic foraminifera Microhedbergella renilaevis Huber and Leckie, 2011 is here proposed. This first occurrence is placed in a 100 m section with 28 secondary markers, including calcareous nannofossils, planktonic foraminifera, palynomorphs, an inoceramid bivalve, ammonites, stable carbon isotopes, and local marker beds. The outcrop fulfils most of the physical criteria required of a Global Stratotype Section and Point.     

Integrated stratigraphy and palaeoenvironment of the P/E boundary interval, Rakhi Nala section, Indus Basin (Pakistan)

Marine sedimentary section across the Paleocene/Eocene (P/E) boundary interval is preserved in the Dungan Formation (Lower Indus Basin), Pakistan. Four dinoflagellate zones in the P/E interval of the Rakhi Nala section (Lower Indus Basin) are identified and correlated. The quantitative analysis of the dinoflagellate cyst assemblages together with geochemical data are used to reconstruct the palaeoenvironment across the P/E interval. The dinocyst assemblages allow the local correlation of the Dungan Formation (part) of the Sulaiman Range with the Patala Formation (part) of the Upper Indus Basin and global correlation of the Zone Pak-DV with the Apectodinium acme Zone of the Northern and Southern hemispheres. The onset of the carbon isotopic excursion (CIE) associated with Paleocene Eocene Thermal Maximum (PETM) is used globally to identify the P/E boundary. The CIE for the total organic carbon (fine fraction) δ¹³C_FF is of a magnitude of ?1.7‰ is recorded for the first time in the Indus Basin. The Apectodinium acme precedes and straddles the onset of the CIE in the Indus Basin. This Apectodinium acme is also accompanied by a planktonic and benthonic foraminifera “barren zone.” The CIE in the Indus Basin, coupled with the changes in the dinocyst distribution and the benthonic and planktonic foraminifera assemblages, provides evidence of the changes associated with the PETM in this little-known part of the world. The benthonic foraminiferal assemblage indicates bathyal environment of deposition at the time of P/E boundary interval; the presence of dominantly open marine dinoflagellates and high planktonic foraminiferal ratio suggest that the water column at this site was well connected with the rest of the Tethys.     

Lower carboniferous (Dinantian) stratigraphy and structure in the Kingscourt Outlier,Ireland

Logging of 55 recent boreholes, together with remapping, has resulted in a fundamental reassessment of the stratigraphy and sedimentology of the Dinantian Kingscourt Outlier. Despite the present isolated position of the outlier within the Longford-Down Massif, the Kingscourt rocks are an integral part of the Dublin Basin succession. The newly defined Ardagh Platform marks the most northerly limit to basinal sedimentation in the Dinantian Dublin Basin. The Courceyan is a typical but thinner, north Dublin Basin succession with two new formal units: the Rockfield Sandstone Member and the Kilbride Formation. The latter, a coarse-grained, well washed limestone of latest Courceyan to early Chadian (late Tournaisian) age is the shallow water equivalent of the Feltrim Formation (Waulsortian facies), which is absent in the outlier. The Courceyan interval in the north of the outlier is markedly attenuated. In the succeeding Chadian-Brigantian interval basinal facies predominate in the south, but on the Ardagh Platform an almost complete coeval Viséan shallow water sequence is found. A new platform unit (Deer Park Formation) of latest Asbian to Brigantian age is defined in the Ardagh area. The Dee Member (Chadian) is newly defined for the lower part of the basinal Tober Colleen Formation and the Altmush Shale Member is formally defined for the upper part of the Loughshinny Formation. Two major structures dominate the Kingscourt Outlier: the NE-SW trending Moynalty Syncline in the south and the N-S trending Kingscourt Fault. Both are Hercynian structures, but probably represent reactivated Caledonide basement-controlled structures. Dinantian syn-depositional faulting is indicated in both the Courceyan (‘Kingscourt Sag’) and Chadian-Asbian. The latter period of faulting in the Ardagh area separates platform facies in the north from basinal facies to the south. In the late Asbian, platform facies with carbonate build-ups prograded south into the basin as far south as Nobber, but in the latest Asbian to Brigantian, basinal facies extended northwards over the collapsed platform margin.     

Tommotian (Lower Cambrian) stratigraphy and fossil fauna communities in the Kiya River section (Kuznetsk Alatau)

The lower Ust’-Kundat Formation has been studied in detail in a section along the Kiya River (Kuznetsk Alatau, Altai-Sayan folded area). The section was deposited during the Tommotian stage and is a stratotype for the Lower Cambrian Ust’-Kundat sequence comprising several members of the Ust’-Kundat Formation. Member 2 contains newly discovered and previously known species of archaeocyathids near its top found stratigraphically lower than the oldest known archaeocyathan assemblage of the Nochoroicyathus mariinskii biozone. The found archaeocyaths cannot be dated precisely and may have either Tommotian or Atdabanian ages. Small shelly fossils from the same section cover a large stratigraphic range as well. The findings call for updating the age of the upper Ust’-Kundat sequence and the Tommotian upper boundary in the regional stratigraphy of the Altai-Sayan folded area.     

Jurassic-Cretaceous (Bathonian to Cenomanian) palynology and stratigraphy of the West Tiba-1 borehole,northern Western Desert,Egypt

Land-derived pollen and spores and marine dinoflagellate cysts were extracted from the Jurassic and Cretaceous sediments of the West Tiba-1 borehole, northern Western Desert, Egypt, On the basis of the recovered palynomorphs, of known stratigraphical significance, the following stages were assessed: Bathonian-Oxfordian (Middle-Late Jurassic) and Hauterivian, Aptian-Early Albian, Late Albian-Early Cenomanian, Early Cenomanian and Late Cenomanian (Early-Middle Cretaceous). No palynomorphs diagnostic for the Berriasian, Valanginian and Barremian stages (Early Cretaceous) were depicted. Based on the nature and composition of the identified palynomorph content, five informal palynomorph assemblage zones were recognised. These are: the Gonyaulacysta jurassica-Korystocysta kettonensis Assemblage Zone (PI, Bathonian-Oxfordian), Ephedripites-Aequitriradites verrucosus Assemblage Zone (PII, Hauterivian), Afropollis jardinus-Duplexisporites generalis-Tricolpites Assemblage Zone (PIIl, Aptian-Early Albian), Nyssapollenites-Elaterosporites Assemblage Zone (PIV, Late Albian-Early Cenomanian) and Assemblage Zone PV (Early-Late Cenomanian). The latter zone was differentiated into two subzones, namely the Classopollis brasiliensis-Elaterosporites klaszii Assemblage Subzone (PVa, Early Cenomanian) and Afropollis kahramanensis-Triporates Assemblage Subzone (PVb, Late Cenomanian). The time stratigraphy of the studied interval was revised. The occurrences and types of the dinoflagellate cysts, extracted from the studied succession, reflect a general shallow (shelf) marine pal˦oenvironment.     

中扬子台地下奥陶统含礁层系层序地层研究

运用露头层序地层学原理与方法，将中扬子台地早奥陶世含礁地层划分为4个Ⅱ型层序，并阐述了各层序的体系域特征和形成的沉积动力学机制以及海平面变化对沉积、生物迁移、生物礁及环境的控制作用。认为在含礁层序形成过程中，存在着4个海平面变化旋回，第一旋回为两河口期早至中期，第二旋回为两河口期晚期至道保湾期早期，第三旋回为道保湾期早至晚期，第四旋回为大湾期早至中期，其中两河口期存在着3个次一级的旋回，第一旋回发生于分乡组二段(鲡粒段)；第二旋回发生于分乡组三段(互层段)；第三旋回发生于分乡组四段(夹层段)；识别出3个平衡型碳酸盐体系和一个滞后型碳酸盐岩沉积体系。研究结果表明，分乡组与红花园组生物礁均形成于高海平面时期。由于海平面变化过程中存在多个次一级的旋回，致使本区生物礁具有厚度和规模小、数量多和分布广等特点。     

Integrated biostratigraphy and carbon isotope stratigraphy of the Lower Cretaceous (Barremian to Albian) Adriatic-Dinaridic carbonate platform deposits in Istria, Croatia

The Adriatic-Dinaridic carbonate platform (ADCP) was one of the largest and relatively well preserved Mesozoic platforms in the Mediterranean region (central Tethys). The peninsula Istria, in the northwestern part of the ADCP, is built up predominantly of shallow-water carbonates of the Middle Jurassic (Dogger) to Eocene age and, to a lesser extent, of Paleogene clastic deposits (flysch and calcareous breccia). This study focuses on a Lower Cretaceous (Barremian to Albian) succession of strata at five localities in western Istria. Stratigraphic determinations are based on identification of nine microfossil assemblages (benthic foraminifera and calcareous algae Dasycladales) and on using their taxa as index fossils. The age of strata with these microfossil assemblages, however, is questionable. Most of the age uncertainties are associated with a regional emersion, which occurred on the ADCP during the Aptian or close to the Aptian-Albian transition. It is unclear what portions of the Upper Aptian and/or Lower Albian are missing along this unconformity. A stable isotope study was conducted on homogenous micritic matrix samples in an attempt to resolve some of these uncertainties. Variations in carbon isotope compositions proved useful for stratigraphic correlation between the examined successions of strata, for improving their age determination, and for relating them to other coeval successions that span an important time interval of major oceanographic changes and carbon-cycle perturbations associated with the Early Aptian oceanic anoxic event (OAE 1a).     

An ichthyosaur vertebra from the Cretaceous (Middle Cenomanian) Karai Formation,southern India

The note describes a well-preserved ichthyosaur vertebra from the upper Cretaceous Karai Formation (late Albian to late Cenomanian) of the Uttattur Group of rocks exposed near Ariyalur, Tamil Nadu, southern India.     

Permian continental basins in the Southern Alps (Italy) and peri-mediterranean correlations

The Late Carboniferous to Permian continental successions of the Southern Alps can be subdivided into two main tectono-sedimentary Cycles, separated by a marked unconformity sealing a Middle Permian time gap, generally estimated at over 10 Ma. The lower cycle (1), between the Variscan crystalline basement and the Early Permian, is mainly characterised by fluvio-lacustrine and volcanic deposits of calc-alkaline acidic-to-intermediate composition, which range up to a maximum thickness of more than 2,000 m. The upper cycle (2), which is devoid of volcanics, is mostly dominated through the Mid?–Late Permian by alluvial sedimentation which covered the previous basins and the surrounding highs, giving rise to the subaerial Verrucano Lombardo-Val Gardena (Gröden) red-beds, up to about 800 m thick. The palaeontological record from the terrigenous deposits of both the above cycles consists mainly of macro- and microfloras and tetrapod footprints. The age of the continental deposits is widely discussed because of the poor chronological significance of a large number of fossils which do not allow reliable datings; however, some sections are also controlled by radiometric calibrations. The comparison with some selected continental successions in southern Europe allows to determine their evolution and set up correlations. A marked stratigraphic gap shows everywhere between the above-mentioned Cycles 1 and 2. As in the Southern Alps, the gap reaches the greatest extent during the Mid-Permian, near the Illawarra Reversal geomagnetic event (265 Ma). In western Europe, however, such as in Provence and Sardinia, the discussed gap persists upwardly to Late Permian and Early Triassic or slightly younger times, i.e. to the onset of the “Alpine sedimentary Cycle”, even though in northeastern Spain (Iberian Ranges, Balearic Islands) this gap results clearly interrupted by late Guadalupian–Lopingian deposits. The above two major tectonosedimentary cycles reflect, in our view, two main geodynamic events that affected the southern Europe after the Variscan orogenesis: the Late Carboniferous–Early Permian transformation of the Gondwana–Eurasia collisional margin into a diffuse dextral transform margin and the Middle–Late Permian opening of the Neotethys Ocean, with the onset of a generalised extensional tectonic regime and the progressive westward marine ingression.     

Jurassic and Cretaceous stratigraphy of the Anabar area (Arctic Siberia,Laptev Sea coast) and the Boreal zonal standard

Recent integrated studies of Mesozoic reference sections of the Anabar area (northern Middle Siberia, Laptev Sea coast) and the reinterpretation of all the previous data on a modern stratigraphic basis permit considerable improvement of the bio- and lithostratigraphic division and facies zoning of Jurassic and Cretaceous sediments in the region. Analysis of abundant paleontological data allows the development or considerable improvement of zonal scales for ammonites, belemnites, bivalves, foraminifers, ostracods, dinocysts, and terrestrial palynomorphs from several Jurassic and Cretaceous intervals. All the zonal scales have been calibrated against one another and against regional ammonite scale. Reference levels of different scales useful for interregional correlation have been defined and substantiated based on the analysis of lateral distribution of fossils in different regions of the Northern Hemisphere. It provides the possibilities to propose and consider parallel zonal scales within the Boreal zonal standard for the Jurassic and Cretaceous periods. A combination of these scales forms an integrated biostratigraphic basis for a detailed division of Boreal-type sediments regardless of the place of their formation and for the comparison with the international stratigraphic standard as far as a possible use of a set of reference levels for correlation.     

Fusulinid biostratigraphy of the Lower Permian Zweikofel Formation (Rattendorf Group; Carnic Alps,Austria) and Lower Permian Tethyan chronostratigraphy

The Zweikofel Formation of the Rattendorf Group in the Carnic Alps (Austria) is 95–102 m thick and consists of a cyclic succession of thin‐ to thick‐bedded fossiliferous limestone and intercalated thin intervals of siliciclastic sediment. The siliciclastic intervals were deposited in a shallow marine nearshore environment. The variety of carbonate facies indicates deposition in a shallow neritic, normal‐saline, low‐ to high‐energy environment. The Zweikofel Formation is characterized by a paracyclic vertical arrangement of facies and represents sedimentary sequences that are not well understood elsewhere in the Tethys. Fusulinids and conodonts from the upper Grenzland and Zweikofel formations in the Carnic Alps clearly suggest that what has been called ‘Sakmarian’ in the Tethys includes both the Sakmarian and Artinskian stages of the Global Time scale. Fusulinids from the lower part of the Zweikofel Formation at Zweikofel closely resemble those of the Grenzland Formation and approximately correlate with the upper part of the Sakmarian and lower part of the Artinskian of the Global Time scale. The upper part of the Zweikofel Formation correlates approximately with the lower‐middle (?) parts of the Artinskian Stage of the Global Time scale. A new regional Hermagorian Stage of the Tethyan scale is proposed between the Asselian and Yakhtashian. The lower boundary of the Hermagorian Stage is proposed to be located at the base of bed 81 in the 1015 section of Darvaz (Tadzhikistan). The boundary between the Hermagorian and Yakhtashian stages is placed at the base of bed 73 in the Zweikofel section at Zweikofel, Carnic Alps. In the Darvaz region, Tadzhikistan, the type area for the Yakhtashian Stage, this boundary has never been precisely defined. The entire fusulinid assemblage of the upper part of the Grenzland and Zweikofel formations reported herein includes 62 species of 18 genera, of which one subgenus and 12 species and subspecies are new. Copyright © 2012 John Wiley & Sons, Ltd.     

Inflorescences of Mauldinia sp. (Lauraceae) and associated fruits from the Cenomanian of Languedoc Roussillon,France

Inflorescences of Mauldinia (Lauraceae) are described from the middle Cenomanian Pauletian facies of Gard, Languedoc-Roussillon, south-eastern France. This is the first record of the genus from this part of Europe. Mauldinia sp. is described based on peduncles and lateral units. Isolated, slender peduncles show spirally arranged scars or rarely attached lateral units. Isolated lateral units consist of cladode-like structures showing up to seven flower/fruit scars. Some isolated fruits were found associated with peduncles and lateral units. Fruits are ovoid fruits contain a single, elongated seed. The pericarp consists of epicarp, mesocarp and endocarp. The seed consists of two cotyledons containing well-developed reserve cells. Mauldinia sp. from Gard differs from known Mauldinia species by having longer internodes along the peduncle and by the shape of the lateral units. Sedimentological and palaeontological evidence suggests that Mauldinia sp. from Gard grew in a protected, littoral environment with limited marine influence. This report provides new information to the relatively poorly known Cretaceous record of angiosperms in France. The occurrence of Mauldinia in the lower Upper Cretaceous of Gard corroborates the widespread occurrence of the genus in marginal littoral environments during the mid-Cretaceous.     

A new amber deposit from the Cretaceous (uppermost Albian-lowermost Cenomanian) of southwestern France

A Cretaceous amber deposit has recently been discovered in a quarry of Charente-Maritime (southwestern France), at Cadeuil. This paper presents the sedimentary and palaeoenvironmental settings of the uppermost Albian-lowermost Cenomanian series including the amber deposit. A preliminary analysis of the amber samples reveals diverse fossil arthropods (a few mites and at least 20 insect families within 9 orders), as well as numerous micro-organisms, mainly algae and mycelia. A myceloid colony of bacteria, a flagellate algae and four especially well preserved insects are illustrated (Diptera Dolichopodidae, Diptera Chironomidae, Hymenoptera Parasitica, and Heteroptera Tingidae). The abundance of the limnic micro-organisms is discussed in terms of bloom events. Their relative scarcity in almost all the amber pieces containing fossil arthropods is attributed to differences in the origin of resin: production along trunk and branches for amber with arthropods; production by aquatic roots for amber rich in algae. The absence of pollen and spores in amber is attributed to differences in the respective periods of resin and palynomorph production, which may be related to a seasonal climate during the Albian-Cenomanian transition in Western Europe.     

Palynology and genetic sequence stratigraphy of the reservoir rocks (Cenomanian,Bahariya Formation) in the Salam Oil Field,north Western Desert,Egypt

Twenty-eight samples from the Bahariya Formation of the Salam-17 Well in the north Western Desert were palynologically investigated. These samples are of Cenomanian age. Fair diversity and fair to moderately preserved palynomorph assemblage has been recovered. Among them, the dinoflagellate cysts showed very poor diversity and abundance. Four miospore zones have been informally identified in the lower Cenomanian. Various palynofacies criteria, adopted from previous publications (e.g. relative particle abundance data, brown to black wood ratio, equi-dimensional to lath-shaped black wood ratio, average size of phytoclasts and spores/pollen ratio) are applied as alternative indicators to monitor the proximal–distal trends instead of the marine palynomorphs-based parameters. The method can be applied in the Egyptian Western Desert to overcome the rarity and absence of dinoflagellate cysts in the recovered organic residues. The palynofacies study of the section demonstrates a predominantly regressive phase, characterized by deltaic, distributary or tidal channels, interrupted by short-lived marine incursions. The palynofacies trends within the studied succession indicate six genetic sequences informally described as Genetic Stratigraphic Sequences A through F.