Coniacian Santonian Research Articles

Senonian platform-to-slope evolution in the tectonically-influenced Syrian Arc sedimentary belt: Beni Suef Basin, Egypt

The Beni Suef Basin is a rift basin that was formed in the Early Cretaceous in response to the break-up of the Gondwana. The infill consists of a thick Mesozoic–Paleogene succession deposited during two main tectonic phases; the Early Cretaceous syn-rift phase and the Late Cretaceous post-rift phase. The post-rift phase was subsequently subjected to an intense compressional tectonic regime related to late Cretaceous Syrian arc tectonics. Within the basin-fill succession, the Senonian deposits, which are composed of carbonates and mixed siliciclastic/carbonate rocks of the “B” and “A” members of the Abu Roash Formation, was formed as a marine platform developed under fluctuated shelfal conditions. These deposits were overlain by chalk of the Khoman Formation that is interpreted to have formed in an outer shelf–middle slope setting. The Senonian succession is subdivided into two 3rd order depositional sequences (Latest Turonian–Early Coniacian SQ-1 and Coniacian–Santonian SQ-2) and one 2nd order depositional sequence (Campanian–Maastrichtian SQ-3). The depositional history of the Senonian in the Beni Suef Basin is interpreted to have been controlled by variable sedimentation accompanied by progradation and retrogradation of carbonate platform between inner and outer shelf environments during the Coniacian–Santonian, and between inner shelf and upper slope environments during the Campanian–Maastrichtian to the end of Senonian. The changes in depositional environments and relative sea-level fluctuations were a factor of the variations in accommodation and sedimentation likely controlled primarily by the Syrian Arc tectonic pulses, which may also have affected basin development and that of the surrounding areas over the northern Western Desert of Egypt particularly during Senonian.

Calcareous nannofossils from the Great Australian Bight (IODP Site U1512) as a record of the peak and early decline of the mid-Cretaceous super greenhouse

Abstract International Ocean Discovery Program drilling in the Great Australian Bight (Site U1512) provides a record of Turonian to Santonian hemipelagic sedimentation deposited in an elongate epicontinental basin that opened westward to the Southern Ocean during the peak and the early decline of the Cretaceous hot greenhouse. Despite its relatively high paleolatitude (at about 60°S), the biostratigraphy of calcareous nannofossils from this succession is directly correlative to low-latitude zonation schemes throughout the Turonian to Santonian. These calcareous nannofossil assemblages are somewhat restricted in species composition, lacking some elements generally found in Late Cretaceous assemblages (e.g., holococcoliths). In addition, two biostratigraphically-important high latitude taxa (Thiersteinia ecclesiastica, and Zeugrhabdotus kerguelenesis) have biostratigraphic ranges notably shorter than elsewhere, indicating range truncation through local extirpation. Quantitative paleoecological analysis of the calcareous nannofossil assemblages indicates that the major change in the paleoenvironment was the evolution from conditions that were quite warm and had relatively elevated surface water fertility in the Turonian to cooler and possibly more oligotrophic conditions in the Coniacian–Santonian. The first cooling began at about 92 Ma, accelerated at about 91.2 Ma and then continued to gradually cool during the Coniacian–Santonian. This paleotemperature scenario is consistent with those documented from other localities globally.

Cretaceous lithostratigraphy of North-East Greenland

An updated and revised lithostratigraphic scheme is presented for the Cretaceous of North-East Greenland from Traill Ø in the south to Store Koldewey in the north. The Ryazanian to lower Maastrichtian succession is up to several kilometres thick and comprises four groups, 12 formations and 18 members. The groups record the tectonic evolution of the East Greenland depocentre on the western flank of the evolving proto-Atlantic seaway. The Wollaston Forland Group encompasses the uppermost Jurassic – lowermost Cretaceous rift-climax succession and contains the Lindemans Bugt and Palnatokes Bjerg Formations; two new members of the latter formation are erected from Store Koldewey. Post-rift Cretaceous strata are referred to the new Brorson Halvø Group and the Home Forland Group. The Brorson Halvø Group (uppermost Hauterivian – middle Albian) is dominated by slope and basinal mudstones of the new Stratumbjerg Formation but also includes fluvio-deltaic and shallow marine sandstones of the revised Steensby Bjerg Formation on northern Hold with Hope and submarine slope apron breccias and conglomerates of the revised Rold Bjerge Formation on Traill Ø. The Home Forland Group covers the middle Albian – Coniacian succession. The basal unconformity records an important mid-Albian tectonic event involving intrabasinal uplift, tilting and erosion, as exemplified by the middle Albian conglomerates of the new Kontaktravine Formation on Clavering Ø. The Home Forland Group is dominated regionally by mud-dominated slope to basinal deposits of the elevated and revised Fosdalen Formation; it also includes lowstand basin-floor fan sandstones of the new upper Albian Langsiden Member. The new Jackson Ø Group (upper Turonian – lower Maastrichtian), records a phase of basin reorganisation marked by a significant fall in sedimentation rate in North-East Greenland, probably linked to rift events in, and bypass to, the central proto-Atlantic rift system. The base of the group is an erosional unconformity on Traill Ø and Geographical Society Ø overlain by submarine slope-apron conglomerates of the Turonian Månedal Formation. The base is conformable on Hold with Hope but is defined by a condensed interval (the Coniacian Nanok Member) that is succeeded conformably by slope and basin-floor turbidite sandstones of the Coniacian–Santonian Østersletten Formation and slope to basinal mudstones of the Campanian – lower Maastrichtian Knudshoved Formation. The new Leitch Bjerg Formation of Campanian slope-apron conglomerates and sandstones in eastern Geographical Society Ø erosionally overlies the Knudshoved Formation.

Predatory behaviour in mosasaurid squamates inferred from tooth microstructure and mineralogy

Dental morphology, microstructure and chemistry provide unique insights into various aspects of the evolutionary history and ecology of extinct clades. However, most studies have focused exclusively on the morphological aspects of teeth, while there are significantly fewer detailed accounts of tooth microstructure and mineralogy. Here we provide a full description of the enamel and dentine microstructure of mosasaurid squamates based on an assessment of isolated teeth belonging to two distantly related mosasaurid taxa, i.e., a russellosaurinan and a mosasaurine, from the ?Coniacian–Santonian and Maastrichtian of Belgium. The obtained data are further explored with regard to their value for inferences of mosasaurid predatory behaviour. SEM observations have shown that the Schmelzmuster consists of columnar enamel with an outer layer of parallel crystallites; transmitted light observations have further revealed the presence of mantle dentine cushioning between enamel and orthodentine, and electron microprobe analyses have demonstrated the unaltered enamel chemistry and heterogeneous diagenetic alteration of dentine. Columnar enamel allows minute movements without rupture under bending stress, and together with the presence of shock-absorbing mantle dentine and possibly elevated Fe contents in the enamel, which increase its hardness and enhance acid resistance, it is suggestive of a good ability of the teeth to withstand severe mechanical damage. Such properties of teeth indicate adaptation to shaking and tearing large and resisting prey.

Palaeoenvironmental and source rock potential of the Turonian–Miocene sequence in the West Esh El Mellaha (SW margin of the Suez rift, Egypt): Insights from palynofacies, palynology and organic geochemistry

A detailed palynological, palynofacies and geochemical study has been undertaken on cuttings samples selected from wells drilled in the Gulf of Suez, Egypt. Inter alia, the samples yielded marine palynomorphs, non-marine palynomorphs, amorphous organic matter (AOM) and phytoclasts. Deposits of the Matulla Formation are dated as Coniacian–Santonian based on the angiosperm pollen and dinoflagellate cyst content. Angiosperm pollen Areolipollis vespiformis in the Rudeis Formation is taken as a biostratigraphic marker for the early Miocene.Two palynofacies associations were identified. Association-A from the Matulla and upper Rudeis formations consists mainly of Type-III gas-prone kerogen. Association-B contains Type-II and Type-II/III kerogens with mixed oil and gas, and is typical of Duwi, Esna, Thebes and lower Rudeis samples. Samples were deposited under various dysoxic–anoxic and suboxic–anoxic conditions.The peridiniacean assemblage from the Upper Cretaceous Matulla Formation intimates deposition in a tropical to subtropical setting within the Tethyan Realm of the Malloy Suite. Salixipollenites, fern spores, and dinoflagellate cysts suggest successive phases of humidity versus aridity during the early Miocene.Geochemical data show that samples from the Duwi Formation are Type-II and Type-II/III kerogens. Based on low HI values and low abundance of AOM, palynofacies association-A samples indicate Type-III gas-prone kerogen, whereas association-B samples have the greatest values of HI and AOM, indicating oil-prone Type-II to Type-II/III kerogens.

Meso–Cenozoic cooling and exhumation history of the Orlica‐Śnieżnik Dome (Sudetes, NE Bohemian Massif, Central Europe): Insights from apatite fission‐track thermochronometry

AbstractThis study presents the first suite of apatite fission‐track (AFT) ages from the SE part of the Western Sudetes. AFT cooling ages from the Orlica‐Śnieżnik Dome and the Upper Nysa Kłodzka Graben range from Late Cretaceous (84 Ma) to Early Palaeocene–Middle Eocene (64–45 Ma). The first stage of basin evolution (~100–90 Ma) was marked by the formation of a local extensional depocentre and disruption of the Mesozoic planation surface. Subsequent far‐field convergence of European microplates resulted in Coniacian–Santonian (~89–83 Ma) thrust faulting. AFT data from both metamorphic basement and Mesozoic sedimentary cover indicate homogenous Late Cretaceous burial of the entire Western Sudetes. Thermal history modeling suggests that the onset of cooling could be constrained between 89 and 63 Ma with a climax during the Palaeocene–Middle Eocene basin inversion phase.

Pioneer nannofossil assemblages from the initial transgression of the Niobrara seaway in the Turonian, San Juan Basin, New Mexico, USA

Abstract Nannofossils of the North American Late Cretaceous Western Interior Seaway have been extensively studied, but these investigations have primarily focused on the diverse communities of the Niobrara and Greenhorn sea-level highstands. We lack a firm understanding of the nature of early nannofossil communities from the initial stages of the transgression, and of how the diverse assemblages of the Coniacian–Santonian became established. We investigated nannofossils in a core from the San Juan Basin, New Mexico, with concentrated sampling across this transgression. We then compared nannofossil assemblages from the initial transgression of the seaway to the more established, cosmopolitan assemblages of the Niobrara highstand. The initial stages of transgression were characterized by unusual, low-diversity assemblages dominated by holococcoliths and seldom reported and previously undescribed species of hetero- and holococcoliths. Herein, we describe five new species and one new genus from these assemblages: Ahmuellerella frankiae sp. nov., Gartnerago waszczakii sp. nov., Orastrum schollei sp. nov., Pharus clarescopoli sp. nov., and Wisea sanjuanensis gen. et sp. nov. These initial assemblages transitioned to more cosmopolitan, higher-diversity assemblages, coincident with an unconformity that likely represents subaqueous erosion or prolonged non-deposition. Above this unconformity, the nannoplankton were abundant, diverse, and characterized by open-marine, cosmopolitan taxa that persisted through the Coniacian and Santonian. X-ray fluorescence data collected from the core show a high abundance of the detrital elements Al and Ti in the section, indicating substantial detrital clay input into the area, coincident with deposition of the holococcolith-dominated assemblages. The detrital influence lessened as cosmopolitan nannoplankton became more abundant in the area. We suggest that the initial holococcolith-rich assemblages are representative of a shallow-marine, potentially hyposaline, turbid or unstable environment. Such assemblages have been observed from the Late Turonian elsewhere in northern New Mexico and may represent typical pioneer nannofloras of the Late Cretaceous Western Interior marine transgressions. Our integrated investigation of nannofossils and X-ray fluorescence geochemistry adds to the meager knowledge base of pioneer nannofloral communities in the initial phases of continental marine transgression.

A new faveoloolithid oogenus from the Wido Volcanics (Upper Cretaceous), South Korea and a new insight into the oofamily Faveoloolithidae

The Cretaceous oofamily Faveoloolithidae has a unique shell unit and pore canal system that clearly differs from most of the extant and fossil eggshells. Despite its distinctiveness, morphological (micro- and ultrastructural) and crystallographic features of the Faveoloolithidae are poorly known. Here we report a new faveoloolithid nesting ground from the Upper Cretaceous siltstones within the Daeri Andesite of the Wido Volcanics (Coniacian–Santonian), South Korea. Forty-one of the same kind of dinosaur eggs distributed in at least eight clutches occur in seven different stratigraphic horizons, suggesting a colonial nesting ground and paleontological site fidelity (reuse of a site over geological time scale). These eggs were assigned to a new ootaxon, Propagoolithus widoensis oogen. et oosp. nov., based on a unique shell unit morphology which is branching towards the external part of eggshell, unlike other faveoloolithid eggs. New morphological and crystallographic features of P. widoensis provide a new insight into the oofamily Faveoloolithidae: (1) superimposed shell units, which are widely used as diagnoses of the Faveoloolithidae and Dictyoolithidae, are in fact taphonomic artifacts and (2) round and crystallographically upright shell units partially connected by inclined crystals (bridges) at the inner portion in the tangential section is proposed as an additional synapomorphy of the oofamily Faveoloolithidae. Furthermore, elemental analysis combined with light microscopy, EBSD, and CL analyses provide a successful reconstruction of the complex pore canal infilling process, and suggest that magnesium concentration can be used as a proxy for calcite overgrowth.

The East Anatolia–Lesser Caucasus ophiolite: An exceptional case of large-scale obduction, synthesis of data and numerical modelling

We present new, geological, metamorphic, geochemical and geochronological data on the East Anatolian–Lesser Caucasus ophiolites. These data are used in combination with a synthesis of previous data and numerical modelling to unravel the tectonic emplacement of ophiolites in this region. All these data allow the reconstruction of a large obducted ophiolite nappe, thrusted for >100 km and up to 250 km on the Anatolian-Armenian block. The ophiolite petrology shows three distinct magmatic series, highlighted by new isotopic and trace element data: (1) The main Early Jurassic Tholeiites (ophiolite s.s.) bear LILE-enriched, subduction-modified, MORB chemical composition. Geology and petrology of the Tholeiite series substantiates a slow-spreading oceanic environment in a time spanning from the Late Triassic to the Middle‒Late Jurassic. Serpentinites, gabbros and plagiogranites were exhumed by normal faults, and covered by radiolarites, while minor volumes of pillow-lava flows infilled the rift grabens. Tendency towards a subduction-modified geochemical signature suggests emplacement in a marginal basin above a subduction zone. (2) Late Early Cretaceous alkaline lavas conformably emplaced on top of the ophiolite. They have an OIB affinity. These lavas are featured by large pillow lavas interbedded a carbonate matrix. They show evidence for a large-scale OIB plume activity, which occurred prior to ophiolite obduction. (3) Early‒Late Cretaceous calc-alkaline lavas and dykes. These magmatic rocks are found on top of the obducted nappe, above the post-obduction erosion level. This series shows similar Sr-Nd isotopic features as the Alkaline series, though having a clear supra-subduction affinity. They are thus interpreted to be the remelting product of a mantle previously contaminated by the OIB plume. Correlation of data from the Lesser Caucasus to western Anatolia shows a progression from back-arc to arc and fore-arc, which highlight a dissymmetry in the obducted oceanic lithosphere from East to West. The metamorphic P-T-t paths of the obduction sole lithologies define a southward propagation of the ophiolite: (1) P-T-t data from the northern Sevan-Akera suture zone (Armenia) highlight the presence and exhumation of eclogites (1.85 ± 0.02 GPa and 590 ± 5 °C) and blueschists below the ophiolite, which are dated at ca. 94 Ma by Ar-Ar on phengite. (2) Neighbouring Amasia (Armenia) garnet amphibolites indicate metamorphic peak conditions of 0.65 ± 0.05 GPa and 600 ± 20 °C with a U-Pb on rutile age of 90.2 ± 5.2 Ma and Ar-Ar on amphibole and phengite ages of 90.8 ± 3.0 Ma and 90.8 ± 1.2 Ma, respectively. These data are consistent with palaeontological dating of sediment deposits directly under (Cenomanian, i.e. ≥ 93.9 Ma) or sealing (Coniacian‒Santonian, i.e., ≤89.8 Ma), the obduction. (3) At Hınıs (NE Turkey) P-T-t conditions on amphibolites (0.66 ± 0.06 GPa and 660 ± 20 °C, with a U-Pb titanite age of 80.0 ± 3.2 Ma) agree with previous P-T-t data on granulites, and highlight a rapid exhumation below a top-to-the-North detachment sealed by the Early Maastrichtian unconformity (ca. 70.6 Ma). Amphibolites are cross-cut by monzonites dated by U-Pb on titanite at 78.3 ± 3.7 Ma. We propose that the HT-MP metamorphism was coeval with the monzonites, about 10 Ma after the obduction, and was triggered by the onset of subduction South of the Anatolides and by reactivation or acceleration of the subduction below the Pontides-Eurasian margin. Numerical modelling accounts for the obduction of an “old” ∼80 Myr oceanic lithosphere due to a significant heating of oceanic lithosphere through mantle upwelling, which increased the oceanic lithosphere buoyancy. The long-distance transport of a currently thin section of ophiolites (<1 km) onto the Anatolian continental margin is ascribed to a combination of northward mantle extensional thinning of the obducted oceanic lithosphere by the Hınıs detachment at ca. 80 Ma, and southward gravitational propagation of the ophiolite nappe onto its foreland basin.

Contribution to the stratigraphy and sedimentology of the Upper Jurassic – lower Eocene succession of the Mitla–El Giddi stretches, west Central Sinai, Egypt

The present study deals with the stratigraphy, petrography and facies analysis of the stratigraphic succession of Mitla-El Giddi stretches (west Central Sinai, Egypt). Lithostratigraphically, the study area is covered by a thick succession extending from Late Jurassic to early Eocene time. This succession is subdivided into the Masajid Formation (Upper Jurassic (Oxfordian) at the base followed upwardly by the Risan Aneiza Formation (Lower Cretaceous (? Aptian- Albian), the Galala Fm. (Cenomanian), the Abu Qada Formation (lower Turonian), the Buttum Formation (middle Turonian), the Wata Formation (middle–upper Turonian), the Themed Formation (Coniacian–Santonian), the Sudr Chalk (Campanian–Maastrichtian), the Mitla Formation (= Esna Shale) (Paleocene–lower Eocene), the Thebes Formation (lower Ypresian) and the Minia Formation (upper Ypresian) at top. The Aptian – Albian Risan Aneiza Formation is first recorded at G. El Hamra in the study area. As well, a new formational name (the Mitla Formation) is used to describe the Paleocene – lower Eocene unit equivalent to the Esna Shale due to variation in lithology mainly represented by chalky limestone and argillaceous limestone. Many unconformities, represented by variable sedimentologic features, i.e., red paleosols, conglomerates, crustified laminated limestone and glauconitic facies were investigated and mostly attributed to the Syrian Arc System.The petrographic investigations especially for the lithified rocks revealed eighteen limestone microfacies, three dolostone microfacies and four sandstone microfacies, besides the non-lithified shale, sandy shale, clay and marl lithofacies. The recognized facies and their related paleoenvironments document lateral and common vertical transition between inner, middle and outer ramp setting. These facies could be subdivided into eight associations that are related to six depositional environments: peritidal flat/beach clastics, peritidal flat carbonates, lagoonal clastics, lagoonal carbonates, high energy shoal of ooids and patch reefs (oolitic shoal), intertidal-subtidal open marine, storm influenced subtidal open marine (mid-ramp) and hemipelagic outer ramp facies.The study indicates that, the area was controlled by a long-term transgressive phase and several higher order sea level fluctuations during the deposition of the studied succession. The main factors controlling the ramp deposition and the described events are; structure control mainly Syrian Arc deformation, eustatic sea level fluctuations combined with environmental influences such as autochthonous carbonate productivity-siliciclastic supply and paleorelief conditions.

New Titanosauria (Dinosauria, Sauropoda) remains from the Upper Cretaceous (Plottier Fm) of the southern Neuquén Basin (Patagonia, Argentina)

Fil: Bellardini, Flavio. Provincia del Neuquen. Municipalidad de Plaza Huincul. Museo "Carmen Funes"; Argentina. Direccion Provincial de Patrimonio Cultural. Subsecretaria de Cultura; Argentina

New data on the planktonic foraminifers from the Yunusdag Formation (Coniacian–Santonian) in the Kelevudag Section, northeastern Azerbaijan

An assemblage of planktonic foraminifers is recognized for the first time from the Yunusdag Formation (Kelevudag Section, northeastern Azerbaijan) The analysis of foraminifers from the studied sample suggests that it may belong to the upper part of the Marginotruncana coronata Zone, embracing the interval from the upper Turonian to the lower Coniacian inclusive. The taxonomic composition of the assemblage allows the Kelevudag section to be assigned to an intermediate province separating the Boreal and Tethyan realms and including the Late Cretaceous carbonates of Dagestan.

Geological evolution of the Central Pontides

Abstract Before the Late Cretaceous opening of the Black Sea, the Central Pontides constituted part of the southern margin of Laurasia. Two features that distinguish the Central Pontides from the neighbouring Pontide regions are the presence of an extensive Lower Cretaceous submarine turbidite fan (the Çağlayan Formation) in the north, and a huge area of Jurassic–Cretaceous subduction–accretion complexes in the south. The Central Pontides comprise two terranes, the Istanbul Zone in the west and the Sakarya Zone in the east, which were amalgamated before the Late Jurassic (Kimmeridgian), most probably during the Triassic. The basement in the western Central Pontides (the Istanbul Zone) is made up of a Palaeozoic sedimentary sequence, which ends with Carboniferous coal measures and Permo-Triassic red beds. In the eastern Central Pontides, the basement consists of Permo-Carboniferous granites and an Upper Triassic forearc sequence of siliciclastic turbidites with tectonic slivers of pre-Jurassic ophiolite (the Küre Complex). The Küre Complex is intruded by Middle Jurassic granites and porphyries, which constitute the western termination of a major magmatic arc. Upper Jurassic–Lower Cretaceous shallow-marine limestones (the İnaltı Formation) lie unconformably over both the Istanbul and Sakarya sequences in the Central Pontides. Two new measured stratigraphic sections from the İnaltı Formation constrain the age of the İnaltı Formation as Kimmeridgian–Berriasian. After a period of uplift and erosion during the Valanginian and Hauterivian, the İnaltı Formation is unconformably overlain by an over 2 km-thick sequence of Barremian–Aptian turbidites. Palaeocurrent measurements and detrital zircons indicate that the major part of the turbidites was derived from the East European Platform, implying that the Black Sea was not open before the Aptian. The Çağlayan turbidites pass northwards to a coeval carbonate–clastic shelf exposed along the present Black Sea coast. In the southern part of the Central Pontides, the Lower Cretaceous turbidites were deformed and metamorphosed in the Albian. Albian times also witnessed accretion of Tethyan oceanic crustal and mantle sequences to the southern margin of Laurasia, represented by Albian eclogites and blueschists in the Central Pontides. A new depositional cycle started in the Late Cretaceous with Coniacian–Santonian red pelagic limestones, which lie unconformably over the older units. The limestones pass up into thick sequences of Santonian–Campanian arc volcanic rocks. The volcanism ceased in the middle Campanian, and the interval between late Campanian and middle Eocene is represented by a thick sequence of siliciclastic and calciclastic turbidites in the northern part of the Central Pontides. Coeval sequences in the south are shallow marine and are separated by unconformities. The marine deposition in the Central Pontides ended in the Middle Eocene as a consequence of collision of the Pontides with the Kırşehir Massif.

Chapter 2: Inoceramid Bivalves from the Coniacian and Basal Santonian (Upper Cretaceous) of the Western Canada Foreland Basin

ABSTRACT Inoceramid bivalves are the dominant invertebrate fauna of the Coniacian and basal Santonian of the Western Canada Foreland Basin in western Alberta. In the upper lower Coniacian through to basal Santonian, six successive faunas are recognized, which provide the basis for corresponding, formally defined inoceramid zones. From bottom upward these are the zones of: Cremnoceramus crassus crassus /C. deformis deformis, Inoceramus gibbosus, Volviceramus koeneni, Volviceramus involutus, Sphenoceramus subcardissoides, and Sphenoceramus ex gr. pachti. Particular faunas represent assemblages known widely from the Euramerican biogeographic region, although they characterize mostly its northern, boreal area. The inoceramid-based biostratigraphic scheme allows correlation with other parts of the North American Western Interior and with parts of the Euramerican biogeographic region. The studied succession provides a good record of the Inoceramus gibbosus Zone, which characterizes the topmost lower Coniacian. ...

Paucispecific macroinvertebrate communities in the Upper Cretaceous of El Hassana Dome (Abu Roash, Egypt): Environmental controls vs adaptive strategies

Based on rock and fossil data from the Upper Cretaceous of the El Hassana Dome (Abu Roash, Egypt), factors controlling facies architecture and the nature of biotopes are highlighted. The succession formed on a non-rimmed shelf, the architecture of which varied from an inner to an outer shelf setting upsection. Macrobenthic biotopes are reconstructed and their palaeoecological significance assessed using a novel ternary plot. Based on diversity and community structure (770 specimens assigned to 28 bivalve and gastropod taxa), four paucispecific associations are identified. These are: 1. the ‘Cucullaea’ Assemblage, a low-energy, soft-substrate, oligotrophic outer shelf environment with reduced terrigenous input dominated by infaunal bivalves and hexactinellid sponges; 2. the ‘Plicatula’ Assemblage, a low-energy, restricted inner shelf lagoonal setting with soupy substrates and dysoxia below the sediment-water interface dominated by plicatulid and ostreid bivalves, 3. the ‘Durania’ Assemblage, a high-energy, high-temperature, shoal environment dominated by elevator rudists with minor numbers of echinoids, corals and bryozoans, which together form several biostromes. and 4. The ‘Trochactaeon’ Assemblage, which share the same characteristics of the ‘Durania’ Assemblage. The paucispecific nature of these biotopes is indicative of different stress factors. Consequently, the predominant taxa exhibit different degrees of adaptive strategies. In addition to global sea level, local tectonics have significantly affected facies distribution and biotope structure. The shallower facies during the early Turonian and the dysoxia spanning the Coniacian–Santonian were linked to synsedimentary tectonics, which formed many barriers and led to circulation restrictions.

First record of Pliensbachian (Lower Jurassic) amber and associated palynoflora from the Monti Lessini (northern Italy)

The fossil record of amber dates back to the Palaeozoic, but it is only since the Mesozoic that amber became relatively common, probably because of the spreading of resin-producing plants. In Italy, the oldest ambers come from the Middle and Upper Triassic of the Dolomites. Cretaceous ambers come from some Albian sites in the Dolomites and from the Coniacian–Santonian of Vernasso, Julian Prealps, northern Italy. Until now, no Jurassic sites with amber have been reported in Italy, and this “Jurassic gap” seems generalized, since there are only a few Jurassic ambers described all over the world. Here, we report the first finding of Lower Jurassic (Pliensbachian) amber from the Bellori locality (Grezzana, Verona Province, Northern Italy). The amber was found in two clayey-coal levels containing plant remains and cuticles, with subordinate bivalves, foraminifera and ostracods. Palynomorphs of the amber levels are dominated by levigate and ornamented spores (ferns) and Circumpolles (conifers). Foraminiferal linings and algal cysts are also present. The freshwater alga Pseudoschizaea is reported for the first time from the Lower Jurassic. The amber shows different kinds of preservation, some peculiar features probably connected with the plant structure, and colours ranging from light yellow to blackish red. Moreover, it includes millimetre-sized wood structures (“mummified wood”) and gas bubbles. Fourier-transform–Infrared, thermogravimetric and differential thermogravimetric analyses were carried out and resulted in a clear characterization of this amber with respect to all others known so far. These data, together with sedimentological observations and fossil content analysis, suggest a coastal palaeoenvironment under rather wet conditions, comparable with the present-day Everglades, with the addition of a monsoonal climate as in the modern southern Asia.

The Coniacian–Santonian sedimentary record in southern Tanzania (Ruvuma Basin, East Africa): Planktonic foraminiferal evolutionary, geochemical and palaeoceanographic patterns

AbstractA 101 m thick stratigraphically complete late Coniacian–early Santonian (ca89 to 83 Ma) sedimentary sequence drilled in Tanzania (Tanzania Drilling Project Site 39) allows, for the first time, examination of the planktonic foraminiferal biostratigraphy and evolution, the depositional history, and geochemical patterns of the subtropical–tropical Indian Ocean region. The sedimentary succession corresponds to an outer shelf to upper slope setting and is dominated by calcareous clayey siltstones and mudstones. The occurrences of Tethyan marker species enable application of the tropical biozonation including identification of theDicarinella concavataandDicarinella asymetricaZones. In addition, Tanzania Drilling Project Site 39 is proposed as reference section for the Coniacian/Santonian boundary in the Indian Ocean with the boundary placed at the lowest occurrence ofGlobotruncana linneianain agreement with the Global Stratotype Section and Point (Spain). The record at Tanzania Drilling Project Site 39 provides a unique opportunity to document the planktonic foraminiferal evolution in a subtropical marginal sea environment during a key period in their evolutionary history characterized by a major radiation among the deep‐dwelling taxa. Combined documentation of lithological and geochemical changes (%CaCO3, %Corg,δ13Ccarbandδ18Ocarb) reveals a setting influenced by continental‐derived nutrients in theDicarinella concavataZone (Lindi Formation) with a change to higher carbonate production and reduced surface water primary productivity in the overlyingDicarinella asymetricaZone (Nangurukuru Formation). Planktonic foraminiferal assemblage changes mirror the depositional and geochemical trends and indicate a progressive shift from a more eutrophic to a more oligotrophic regime through time. At the local scale, this palaeoceanographic scenario is consistent with the deepening of coastal Tanzania in response to the Late Cretaceous marine transgression registered in south‐east Tanzania. Because the tectonic evolution and sea‐level rise along the East Africa continental margin is superimposed on the Coniacian–Campanian global long‐term sea‐level high, this study hypothesizes that the epicontinental invasion of blue waters may have favoured radiation among deep‐dwelling taxa.

Radiolarian paleobiogeography in the late Albian–Santonian

Radiolarian paleobiogeography for the late Albian–Santonian is proposed for the first time. The paleobiogeographic differentiation is found to be different for the Albian, Cenomanian, Turonian, and Coniacian–Santonian. The Tethyan and Boreal superrealms can be recognized for the Albian–Santonian. For the Albian–Santonian, the Tethyan Superrealm can be subdivided into realms: Atlantic-Mediterranean, Carpathian-Caucasian, and Tropical-Pacific. The boundaries of these realms changed throughout geological time. The Boreal Superrealm recognized for the Albian so far cannot be subdivided into realms, whereas in the Cenomanian it included the East European and Western Siberian realms without a clear definition of the boundaries and the Boreal-Pacific (in the North Pacific). The Boreal Superrealm is subdivided in the Turonian into two realms (European-Western Siberian and Boreal-Pacific), and in the Coniacian–Santonian, it is subdivided into three realms (European, Western Siberian, and Boreal-Pacific). The Austral Superrealm can be recognized only for the Albian and Cenomanian, and because of the lack of data, it cannot be delineated for the Turonian and Coniacian–Santonian.

Evolution of radiolarians in the late Albian–Campanian

The dynamics of radiolarian evolution in the late Albian–Campanian is analyzed, and several stages are recognized. The first stage (late Albian–middle Cenomanian), related to the MCE regional anoxic event, showed low evolutionary tempos and hence lacked structural change in radiolarian communities. The second stage (late Cenomanian–early Turonian), corresponding to ОАЕ 2, which was a global anoxic event, is characterized by a decrease in the number of genera, while many genera showed increased diversification of species composition. At this stage, a considerable number of genera became extinct and appeared, suggesting an increased rate of the radiolarian evolution. The third stage (middle Turonian–early Coniacian), including the beginning of ОАЕ 3, is characterized by a stabilized number of genera. The fourth stage (late Coniacian–Santonian) completely encompasses ОАЕ 3 except for its very beginning. At this stage, the radiolarian communities underwent a significant structural change, while their rate of evolution increased considerably. Nevertheless, during the ОАЕ 3 stage, a distinct trend toward a decrease in generic diversity continued from the late Cenomanian to the middle Turonian. The fifth stage (Campanian) is characterized by quite significant changes in the assemblage composition, while the trend toward a gradual decrease in the number of genera steadily continued. At this stage, which coincided with a considerable cooling, twice as many genera became extinct as during ОАЕ 2. The analysis of the dynamics of radiolarian evolution showed that the anoxic MCE, ОАЕ 2, and ОАЕ 3 events did not result in degradation of radiolarian assemblages. This suggests that this group has significant stratigraphic potential. In general, the evolution of radiolarians in the Late Cretaceous was gradual. By the end of the Campanian, nearly half of the generic diversity was composed of genera which appeared at the beginning of the Cretaceous and earlier.

Isotope studies of carbonate rocks of La Luna Formation (Venezuela) to constrain the oceanic anoxic event 3 (OAE3)

87Sr/86Sr ratios, δ13C, and δ18O determinations performed on 30 bulk carbonate rocks are presented to constrain the isotope characteristics regarding Oceanic Anoxic Event 3 in the La Luna Formation, Maracaibo Basin. The samples were collected along a 22 m profile in San Miguel region (Merida State, Venezuela). The exhibited 87Sr/86Sr ratios are between 0.707659, at the base, and 0.707733 at the top of studied section, corresponding estimated younger numerical ages than the inferred ages dated as Santonian (85.8–83.5 Ma) based on occurrence of Dicarinella asymetrica. The obtained 87Sr/86Sr ratios are certainly higher than expected for Santonian sea Sr and they are attributed to regular riverine strontium fluxes in the restricted (gulf-like) Maracaibo Basin. The values of δ18O data between −3.76‰ and −11.76‰ are distributed in two distinct clusters in a same way and coherent as for δ13C data which are in a range between −1.75‰ and −13.87‰. One of the clusters δ13C = –2.5 ± 1.0‰ and δ18O = -10.0 ± 1.5‰), illustrate the homogeneous marine deposition under tropical conditions, while the other, more variable, probably could reflect the cyclicity of temporally changes in Pacific versus Atlantic Ocean circulation with cooling water or cooling trend climate. These δ13C values around −2.5 ± 1.0‰ do not fit with the significant carbon isotope excursion as expected for the oceanic anoxic event (OAE) and support the work hypothesis that Coniacian–Santonian anoxic event (denominate as OAE3) is not a global one.