Cenomanian-Turonian Deposits Research Articles

First report of the genus Thorectichthys (Ellimmichthyiformes) in America, from the Cenomanian deposits of the Cintalapa Formation, Chiapas, southeastern Mexico

The El Chango quarry is an outstanding paleontological site of Mexico. The marine limestones of this site represent a small outcrop of the Cintalapa Formation and bear a significant assemblage of Early Cenomanian continental plants plus marine crustaceans, decapods, mollusks, and fishes. This paper includes the description of a double-armored herring species from El Chango, which is named Thorectichthys fideli and belongs to the family Paraclupeidae, in the order Ellimmichthyiformes. This new species shares the diagnostic generic features with T. marocensis and T. rhadinus, two slightly younger North African species previously discovered in Cenomanian–Turonian deposits of the Akrabou Formation, Morocco. The new species has a couple of peculiar features never before observed in the ellimmichthyiforms; the caudal skeleton of this fish has four uroneurals, and the horizontal limb of the preopercle is dorsally notched allowing the superficial lateral exposure of a broad and massive posterior process of the quadrate. Including this species in a comprehensive phylogenetic analysis confirms the monophyletic nature of Thorectichthys and its inclusion as a basal clade of the family Paraclupeidae. Thorectichthys fideli sp. nov. adds to an increasing assemblage of Mexican Cretaceous ellimmichthyiforms that includes ancestral as well as more derivatives species that shows the broad Albian–Cenomanian distribution of the ellimmichthyiforms, along the epicontinental environments of the Tethys Sea.

Carbonate reservoirs quality assessment using sequence stratigraphy study and diagenetic analysis: A case of the oxic Cenomanian-Turonian deposits in Dahar Cliff, Southern Tunisia

The present study relies on field work, including detailed sedimentological and sequence stratigraphic analyses of the oxic Cenomanian-Turonian carbonates in Southern Tunisia. Based on petrographic study, six microfacies were recognized (MF1-MF6). These microfacies are grouped into three facies associations referred to peritidal flat, shallow subtidal and deep subtidal environments, suggesting an inner ramp type-platform. The sequence stratigraphic analysis led to interpret these sequences as a transgressive systems tract (TST) which, locally, contains abundant microfauna of the Whiteinella archaeocretacea biozone. The TST interval is capped by a centimetric highly bioturbated limestone bed corresponding to the maximum flooding surface (MFS). The logged sections culminate with the highstand systems tract (HST) referred to the Gattar Member. Sea-level fluctuations have played a key role in shaping the sequence stratigraphic patterns and driving the associated diagenetic processes. These features were developed in meteoric, marine, mixed meteoric-marine realms including eodiagenetic and mesodiagenetic states. The impact of diagenesis on reservoir properties is twofold, with both enhancing and reducing effects. Porosity is increased by the dissolution of aragonitic rudistic shells, resulting in moldic and vuggy pores, while dolomitization creates intercrystalline porosity. Fractures improve permeability networks by creating channels for fluid movement. However, cementation, micritization and compaction gave detrimental effects on reservoir properties. The improvement of reservoir quality noted along HSTs is primarily linked to diagenetic processes associated with a drop-in sea level. In the Tataouine region, intense dolomitization occurred in the TSTs, resulting in increased porosity and a more promising reservoir potential.

Lithostratigraphic, Paleoenvironmental Characterization and Correlations of the Albian–Turonian Deposits of the Errachidia–Boudnib–Erfoud Basin (Southeast Morocco)

Ten detailed sections have been logged and studied from the “Infra-Cenomanian’’ to the Cenomanian–Turonian deposits in the Errachidia–Boudnib–Erfoud Basin between Tazzouguerte and Anounizme(SE Morocco). They show variations in their lithology and microfacies that reflect changes in the depositional environment from the base to the top of the sedimentary record. Indeed, depositional setting grades from a fluvial environment marked by sandstone deposits of the Ifezouane Formation to an alluvial plain and coastal lagoon environment comprising an alternation of red clay, gypsum, and green marl beds of the Aoufous Formation and, finally, towards shallow to moderately deep marine environments with the deposition of the carbonates of the Akrabou Formation. Correlations between the studied sections show variations in the thickness of strata throughout the basin. The variations recorded in the so-called “Infra-Cenomanian” series may be related to the structuration of the basement. The Cenomanian–Turonian carbonate platform shows deeper marine and thicker sediments towards the east, while it thins towards the west until its disappearance in Anounizme. This reflects the global Cenomanian–Turonian transgression in the Errachidia–Boudnib–Erfoud Basin from the eastern Tethyan realm towards the west. The regional correlation of the Errachidia–Boudnib–Erfoud Basin with the Ouarzazate and Agadir basins shows an eastward thinning of the Cenomanian–Turonian marine deposits of Agadir. This suggests the presence of a paleorelief at the Anounizme locality. This could be the boundary between the Errachidia–Boudnib–Erfoud Basin, with Tethyan influence, to the east and those of Ouarzazate and Agadir, with Atlantic affinity, to the west.

Late Cenomanian–early Turonian ammonites from the Western Saharan Atlas (Algeria)

ABSTRACT New palaeontological and biostratigraphic data from the Cenomanian–Turonian deposits of the western Saharan Atlas are presented in this study. More than 300 specimens of ammonites were collected from Kebeur es Seguia and Aïn El Orak sections, representing the Rhoundjaïa Formation. With the exception of the three ammonites previously described from the western Saharan Atlas by former authors [namely Neolobites vibrayeanus (d’Orbigny), Vascoceras gamai Choffat and Vascoceras cauvini Chudeau], nine additional ammonite species [Calycoceras (Calycoceras) cf. naviculare (Mantell), Eucalycoceras cf. pentagonum (Jukes-Brown), Metoicoceras geslinianum (d’Orbigny), Nigericeras gadeni (Chudeau), Fikaites subtuberculatus (Collignon), Pseudaspidoceras pseudonodosoides (Choffat), Fagesia peroni Pervinquière, Fagesia tevesthensis (Peron) and Choffaticeras (Choffaticeras) sinaiticum (Douvillé)] are described and illustrated from the studied area. Biostratigraphic analysis revealed four ammonite biozones; three from the late Cenomanian namely, the Neolobites vibrayeanus Total Range Zone, the Metoicoceras geslinianum Total Range Zone and the Vascoceras cauvini Total Range Zone; and one from the early Turonian (earliest Turonian), the Choffaticeras sinaiticum Total Range Zone. The recognised ammonite zones demonstrate a significant palaeobiogeographical relationship between the studied area and other countries of North Africa, the Middle East, South America and southern Europe.

Impact of the Anoxic Oceanic Event II on the evolution of ostracods in the Cenomanian-Turonian deposits of the Tinrhert Basin (SE Algeria).

Dans le bassin du Tinrhert, au passage Cenomanien/Turonien, les ostracodes sont rares dans la plupart des niveaux echantillonnes ; ils ne presentent aucune variabilite, leur frequence ne depassant pas 4% de toute la microfaune. Leur presence optimale, tant qualitative que quantitative, s'observe a la base du Turonien inferieur ou leurs corteges sont domines par les genres Cythereis, Paracypris et Cytherella. Afin de comprendre ces observations, nous avons mene une etude paleoecologique sur cinq coupes geologiques et reconstitue l'impact des conditions sedimentologiques (quartz, gypse et pyrite) et celui des variations eustatiques.

Biostratigraphie, géochimie et réponse des composantes microfauniques aux variations environnementales au passage Cénomanien-Turonien à Thénièt El Manchar (Monts de Bellezma, Batna, NE Algérie)

[fr] La présente étude livre une analyse biostratigraphique et géochimique des dépôts cénomano-turoniens de la région Thénièt El Manchar, située dans les Monts de Bellezma-Batna, et leur évolution verticale. Une coupe (TM), épaisse de 180 m, est décrite dans ce secteur. Elle correspond à la Formation des Marnes de Smail, subdivisée en quatre unités litho-stratigraphiques (IA, IB, IC, ID), datée du Cénomanien grâce à la présence d’ammonites et de corail, et à la base de la Formation des Dolomies de l’Oued Skhoun (unité, IIA), datée de la base du Turonien au moyen de foraminifères planctoniques. L’analyse qualitative et quantitative des foraminifères (planctoniques et/ou benthiques), des ostracodes et des marqueurs géochimiques, permet de reconstituer l’évolution du paléo-environnement et les variations paléo-bathymétriques au cours de l’intervalle stratigraphique concerné. Ainsi, les unités IA-IB-IC et la partie inférieure de l’unité ID (Cénomanien) sont dominées par des associations de foraminifères benthiques agglutinés et des carapaces entières d’ostracodes, témoignant d’un milieu de plate-forme et d’un faible hydrodynamisme. Dans ces dépôts, les associations montrent une diversité spécifique faible à moyenne et une abondance plus ou moins élevée, témoignant de conditions trophiques et d’oxygénation considérées comme normales. Les derniers termes de l’unité ID (sommet du Cénomanien) et l’unité IIA (base du Turonien) marquent, quant à eux, une évolution vers des conditions plus profondes, comme le montre la succession standard des événements déjà reconnus en Afrique du nord, à savoir: l’abondance de foraminifères planctoniques, la présence de ‘filaments’ et une réduction drastique de la faune d’ostracodes. En outre, les courbes isotopiques du carbone (δ13C) et de l’oxygène (δ18O) des carbonates mettent en évidence des anomalies isotopiques relatives aux modifications paléo-environnementales. Les données du δ13C et celles du COT indiquent une productivité primaire faible. Les données du δ18O, quant à elles, indiquent une augmentation des paléo-températures, cause principale du déclenchement de l’EAO 2. Ces interprétations paléo-environnementales s’accordent avec les données connues du contexte paléogéographique régional et mettent en exergue les spécificités téthysiennes.

Litho- and biostratigraphy, facies patterns and depositional sequences of the Cenomanian-Turonian deposits in the Ksour Mountains (Saharan Atlas, Algeria)

The Cenomanian-Turonian deposits exposed in the Ksour Mountains, western part of the Saharan Atlas (Algeria), document marine shelf environments that had been thriving on the North African passive margin, connected northwards to the Tethys Ocean, and fringed southwards by the Saharan craton. Their lithological, palaeontological, and sedimentological characteristics have been investigated to provide new insights into the biostratigraphy, palaeo-environmental evolution and sea-level changes in this western part of the Saharan Atlas. Three formations are recognized, from base to top of the studied succession: 1. The El Rhelida Formation comprising two informal units: the mixed siliciclastic-carbonate unit deposited under different flow regime conditions, from shoreline to backshore environments, and the limestone–claystone unit including coastal mudflat deposits prone to storm events. The early Cenomanian age of the El Rhelida Formation is supported by vertebrate assemblages. 2. The Mdaouer Formation comprising two units: the evaporitic unit dominated by claystone and evaporite alternations deposited on a flat coastal sabkha with occasional storms, and the marlstone–limestone unit formed in a peritidal-lagoonal environment. The Mdaouer Formation is of early-middle Cenomanian age. 3. The Rhoundjaïa Formation comprising three units: the lower limestone unit consisting of relatively homogeneous fossiliferous limestones; the middle marly unit composed of marlstone and bioclastic limestones, and the upper limestone unit consisting of carbonates showing vertical variations in faunal content and stratonomy. The Rhoundjaïa Formation was deposited in homoclinal ramp setting. Ammonite data indicate an early late Cenomanian to early Turonian age for this interval. Within an overall transgressive trend, the Cenomanian-Turonian deposits of the Ksour Mountains record three third-order depositional sequences bounded each by regional discontinuities.

Roveacrinids (Crinoidea, Roveacrinida) from the Cenomanian-Turonian of southwest Algeria (Saharan Atlas and Guir Basin)

In the southwestern part of Algeria, the Cenomanian-Turonian marine deposits build up a prominent ledge in a perched syncline (Ksour Mountains, western Saharan Atlas) or at high radius of curvature (Guir Basin). The petrographical analysis of the Cenomanian-Turonian deposits of the Ksour Mountains and of the Guir Basin reveals unexpected assemblages of roveacrinoidal ossicles comparable with those formerly reported from the Tinrhert area. For the first time, isolated ossicles of genuine and undisputable Roveacrinidae are illustrated. Three sections, Djebel Rhoundjaia (western Saharan Atlas), Berridel and Kénadsa (Guir Basin), were scrutinized to recognize the microcrinoidal sections within the carbonate microfacies and to compile the successive occurrence of respective roveacrinid taxa (besides the classical search for standard index microfossils) in an attempt to pinpoint more precisely the position of the Cenomanian-Turonian boundary (C/T B). These assemblages are particularly morphologically and taxonomically diverse with three species of genus Roveacrinus and one of genus Orthogonocrinus. The presence of Saccocomidae (Applinocrinus) is especially unusual in such stratigraphic levels. The relative abundance and diversity of Roveacrinidae evidence a peak when approaching the C/T B. Such an event is recurring in the latest Cenomanian in various Tethyan and Atlantic areas. These fluctuations are consistent with a high surface-water productivity just before the C/T B.

New findings of seeds and fruits from Cenomanian–Turonian deposits of Western Siberia

Three-dimensional remains of seeds and fruits originating from Cenomanian–Turonian deposits of the Simonovo Suite are reported from one locality at the Kem’ River near the village Maslennikovo (58°11'24.8"N, 91°54'24.2"E) and from six localities at the Kiya River near the village Kubayevo (56°04'27.5"N, 87°52'22.4"E; 56°04'39.6"N 87°52'19.0"E; 56°04'39.6"N, 87°52'20.9"E), from the south of Western Siberia. The majority of the findings studied belong to undescribed genera of gymnosperms and flowering plants. The Maslennikovo collection has yielded seeds of Alapaja cf. uralensis Dorofeev (Cupressaceae) and Liriodendroidea Knobloch et Mai (Magnoliaceae), fruits of Porosia cf. verrucosa (Lesq.) Hickey, as well as platanaceous heads. The Kubayevo collections contain seeds and remains of a female cone of cf. Krassilovidendron fecundum Sokolova, Gordenko et Zavialova (Cupressaceae), seeds of Saccospermum cf. trebecense Knobloch et Mai and fruits or seeds of Spirellea Knobloch et Mai (angiosperms of unknown affinities). Despite having originated from deposits of the same suite, the Maslennikovo and Kubayevo collections almost don’t have overlapping forms.

Evidence of bacteriogenic iron and manganese oxyhydroxides in Albian–Cenomanian marine sediments of the Carpathian realm (Poland)

The Albian and Cenomanian marine sediments of the Silesian and Tatric basins in the Carpathian realm of the Western Tethys contain ferric and ferromanganese oxyhydroxides, visible macroscopically as brown stainings. They coat calcareous bioclasts and mineral clasts, fill pore spaces, or locally form continuous, parallel microlayers, tens of micrometers thick. Light-microscope (LM) and scanning-electron-microscope (SEM) obser- vations show that the coatings contain elongated capsules, approximately 3–5 µm across and enriched in iron and manganese, which may be remnants of the original sheaths of iron-related bacteria (IRB). Moreover, the ferric and ferromanganese staining observed under LM is similar to bacterial structures, resembling the sheaths, filaments and rods formed by present-day bacteria of the Sphaerotilus–Leptothrix group. All of the possible bacteria-like structures are well preserved owing to processes of early diagenetic cementation. If the observed structures are fossil IRB, these organisms could have played an important role in iron and manganese accumulation on the sea floor during Albian–Cenomanian time. The most plausible source of metals for bacterial concentration in the Silesian Basin might have been submarine low-temperature hydrothermal vents, as previously was hypothesized for Cenomanian–Turonian deposits on the basis of geochemical indices.

Depositional environments and sequence architecture of the Raha and Abu Qada formations (Cenomanian–Turonian), west central Sinai, Egypt

Cenomanian–Turonian deposits are important reservoirs for many oil fields in the Western Desert and the Gulf of Suez region of Egypt. Study of the Raha and Abu Qada formations (Cenomanian–Turonian), from five dip-oriented outcrop locations in west central Sinai; indicates deposition of a mixed siliciclastic-carbonate system on a ramp setting. The inner ramp facies (bivalve and benthonic foraminiferal wackestone) grades northward to the mid ramp facies (echinoderm calcisphere packstone, and oyster floatstone), and outer ramp facies (planktonic foraminiferal wackestone and calcisphere wackestone).The two studied formations comprise one second-order depositional sequence (duration of approximately 10 Million years). This large scale sequence includes four third-order depositional sequences, three of which are observed in the Raha Formation, with the other one recorded in the Abu Qada Formation. Because west central Sinai was tectonically stable during the Cenomanian and Turonian, the main factor controlling the lateral and vertical distribution of facies tracts is likely due to changes in the relative sea level. The Cenomanian–Turonian boundary event is known as the largest oceanic anoxic event during the Cretaceous. This global event has been documented in three of the studied sections. The recorded δ13C excursions range from+3.04‰ to+5.24‰. These high positive excursions in δ13C are associated with highly negative values of δ18O (values range from −6.01‰ to −1.38‰).

Krassilovianthus gen. nov., a new staminate inflorescence with similarities to Platanaceae and Hamamelidaceae from the Cenomanian–Turonian of western Kazakhstan

Staminate inflorescences from Cenomanian-Turonian deposits of the Sarbay locality of western Kazakhstan are described as Krassilovianthus gen. nov. The new genus is characterized by the unique structure of the flower, which is unknown in similar platanoid heads. Flowers of Krassilovianthus gen. nov. possess a perianth that is considerably longer than its two stamens. The stamens are bisporangiate and dithecate, with small tricolporate pollen grains. Platanoid reproductive organs and leaves found at the Sarbay locality are considered.

Род Ettingshausenia (Platanaceae) в сеноман-туронских флорах Евразии

Rhomboid platanaceous leaves from the Cenomanian-Turonian deposits of Rurasia are revised. The most part of findings are referred to Ettingshausenia cuneifolia (Bronn) Stiehler. Emended diagnosis of the genus Ettingshausenia and detailed morphological and epidermal characteristics of E. cuneifolia are given. It is proposed to consider genus Ettingshausenia as a natural extinct genus of Platanaceae family.

Biostratigraphic and isotopic record of the Cenomanian–Turonian deposits in the Ohaba-Ponor section (SW Haţeg, Romania)

The middle Cenomanian–lower Turonian deposits of Ohaba-Ponor section (Southern Carpathians) were studied from biostratigraphic and isotopic points of view. Both the qualitative and semiquantitative nannofloral analyses, as well as the stable isotope (δ 13C and δ 18O) data support significant palaeoenvironmental changes in the investigated interval. Two δ 13C positive excursions were recognized: (1) an excursion up to 1.8‰ (PDB) within the middle/late Cenomanian boundary; (2) an excursion up to 2.2‰ (PDB) in the Cenomanian/Turonian boundary interval. The oldest δ 13C positive excursion recorded (placed within the Acanthoceras jukes-brownei/Eucalycoceras pentagonum Ammonite Zone boundary interval, and in the NC11 Calcareous Nannofossil Zone respectively) could be assigned to the middle Cenomanian Event II (MCEII). During the above-mentioned event, significant increase in abundance of Watznaueria barnesae, followed by successive blooms of Biscutum constans and Eprolithus floralis, were observed. The youngest δ 13C positive excursion was identified in the Cenomanian/Turonian boundary interval (in the NC12 and lower part of the NC13 Calcareous Nannofossil Zones). Even the amplitude of this δ 13C positive excursion is lower in the Ohaba-Ponor section, as generally reported, this may represent the regional record of the OAE2. The successive peaks of the nannofossils Biscutum constans, Zeugrhabdotus erectus and Eprolithus floralis indicate episodes of cooler surface water and high fertility, which preceded and lasted the Cenomanian/Turonian boundary event. Additionally, fluctuations of δ 18O values between −2 and −6‰ suggest also cooler conditions within the Cenomanian/Turonian boundary interval.

Integrated biostratigraphy and inter-regional correlation of the Cenomanian–Turonian deposits of Wadi Feiran, Sinai, Egypt

The Cenomanian–Turonian succession exposed in the Wadi Feiran, Sinai, Egypt, is composed of siliciclastic and carbonate sediments belonging to the Raha (at the base), Abu Qada and Wata formations. Biostratigraphically, the succession has been subdivided into five ammonite zones, which are coeval with five planktic foraminiferal zones. The foraminiferal zones are the Late Cenomanian Hedbergella planispira and Rotalipora cushmani, the Cenomanian–TuronianWhiteinella archaeocretacea , and the Turonian Helvetoglobotruncana helvetica and Marginotruncana schneegansi zones. The Whiteinella archaeocretacea Zone is subdivided into the Late Cenomanian Whiteinella brittonensis and Early Turonian Helvetoglobotruncana praehelvetica subzones. The ammonite zones are the Late Cenomanian Neolobites vibrayeanus and Vascoceras cauvini, and the Turonian Vascoceras proprium /Vascoceras obesum , Choffaticeras segne and Coilopoceras requienianum zones. The integration, chronostratigraphic position and correlation of the proposed biozones are discussed. The Cenomanian/Turonian boundary is located within the Abu Qada Formation, coinciding with the base of the Vascoceras proprium / Vascoceras obesum ammonite Zone and the Helvetoglobotruncan praehelvetica foraminiferal Subzone.

The Cenomanian–Turonian boundary in the Gafsa-Chott area (southern part of central Tunisia): biostratigraphy, palaeoenvironments

This study is based on biostratigraphical and palaeoenvironmental analyses of four columnar sections exposed in the Gafsa-Chott area of central Tunisia. The Cenomanian-Turonian deposits in this area are divisible into Zebbag s.s. (at base), Bahloul and Gattar Formations or their equivalents. The Cenomanian-Turonian boundary is placed within the Bahloul Formation s.s.on the basis of the occurrence of several index ammonite faunas including Choffaticerasaff. massipianum(Pervinqui ère). The Gattar Formation and its equivalents are assigned to a part of the late Early Turonian (Thomasites rollandiand Choffaticeras luciaeIntervals). The occurrence of Spathites (Jeanrogiceras)aff. revelieranus (Courtiller) encrusting the top of the Gattar equivalent probably indicates the top of the Lower Turonian. The meaning of the association C. luciaePervinquière, Thomasites rollandiforma jordaniPervinquière and S. (J.)aff. revelieranuswith respect to the M. nodosoidesZone needs to be clarified. A wide lateral variation in facies is the characteristic feature of the sequence, caused by a rapid change in the depositional setting. It has been concluded that the Cenomanian-Turonian transition of the area under consideration was deposited in a dysaerobic environment, as evidenced by the occurrence in a basin setting of a micritic limestone unit rich in organic matter with planktonic and nektonic organisms and certain stunted neritic fossils. Oxygen impoverishment was less drastic on the carbonate platforms, as indicated by the occurrence of pelagic white limestones devoid of organic matter and containing cephalopods as well as planktonic foraminifers and minute bivalves.

Organic geochemistry of Cretaceous black shales from the Galicia Margin, Ocean Drilling Program Leg 103

Organic-carbon-rich “black shales” from three different Cretaceous episodes sampled during Ocean Drilling Program Leg 103 have been studied by organic geochemical methods. Rock-Eval analysis, carbon isotope data, and lipid biomarkers show organic matter to contain varying proportions of marine and continental materials. In Hauterivian-Barremian organic-carbon-rich turbiditic marlstones, major amounts of land-derived organic matter are found. Aptian-Albian black-colored shales are interspersed within green claystones, from which they differ by containing more marine organic matter. An abbreviated layer of black shale from the Cenomanian-Turonian boundary is dominated by well-preserved marine organic matter. Downslope transport and rapid reburial within a predominantly oxygenated deepwater setting created most of these examples of black shales, except for the Cenomanian-Turonian deposits in which deepwater anoxia may have been involved.