As part of a study of the Cenomanian-Coniacian sedimentary succession in the Sergipe Basin in nor... more As part of a study of the Cenomanian-Coniacian sedimentary succession in the Sergipe Basin in northeastern Brazil, microfacies analyses were tested for possible chronostratigraphic application. The common and widespread remains of roveacrinid echinoderms proved useful for intrabasinal biochronostratigraphy. Local dolomitization in the basin, which destroyed most other fossil remains, left the magnesian-calcitic roveacrinid skeletons largely unaffected. Thus, where diagnostic fossils are scarce or lacking, roveacrinids may provide an ancillary means of chronostratigraphic correlation. The forms recorded from Sergipe are described, and a stratigraphic range chart is presented for intrabasinal application, with the possibility of regional or even global correlation either qualitatively (presence/absence patterns) or quantitatively (ecoevent patterns). Several roveacrinid abundance horizons have been reported worldwide in relation to sea level changes and associated hypoxic events, during which roveacrinids developed abundant opportunistic populations. The present study of the Sergipe Basin provides a basis for comparisons and correlations of roveacrinid occurrences in the mid-Cretaceous succession of the South Atlantic continental margin basins and ODP/DSDP drill cores.
Until recently, it has been assumed that pelagic crinoids, the roveacrinids (Roveacrinida, Crinoi... more Until recently, it has been assumed that pelagic crinoids, the roveacrinids (Roveacrinida, Crinoidea), became extinct during the Cretaceous-Paleogene boundary event. Recent finds of well-preserved roveacrinidal remains (brachials and radials) in the Danian (Early Paleogene) of Poland showed that they survived into the earliest Cenozoic. This group was thus characterized as a "dead clade walking". Here, we present fossil evidence that these pelagic crinoids survived in Poland until at least the Middle Miocene (Badenian, ca. 14 Myr ago)-more than 50 Myr after their supposed extinction. These Miocene roveacrinids constitute the first documented evidence of Roveacrinida in strata of Neogene age, thus prolonging the stratigraphic range of pelagic crinoids. This find characterizes the order as a "Lazarus taxon" rather than a "dead clade walking" group.
New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & T... more New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & TRAPPE) GRANIER et al. 2003, reveal the presence of a reproductive structure (ampulla) located on the inner-middle part of each primary lateral. This fact suggests a new interpretation of the alga and the establishment of a new genus: Granieria BARATTOLO & ROMANO, n. gen. Also, the taxonomic status of the other club-shaped specimens from both the High and Middle Atlas of Morocco and the Central Apennines of Italy is reviewed.
Biostratigraphical, geochemical and microfaunal responses to environmental changes around the Cen... more Biostratigraphical, geochemical and microfaunal responses to environmental changes around the Cenomanian-Turonian boundary at Thénièt El Manchar
The Cretaceous Period (145-66 Ma) consisted of several oceanic anoxic events (120-80 Ma), stimula... more The Cretaceous Period (145-66 Ma) consisted of several oceanic anoxic events (120-80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes-e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.
The Wadi Daya Formation, or the «Calcaires crayeux» of the older literature, attains a thickness ... more The Wadi Daya Formation, or the «Calcaires crayeux» of the older literature, attains a thickness of to 40 metres in the Talerhza Basin of the South Rifian Ridges Domain. Previously, this unit was first dated as Vraconian (i.e., mid-Cretaceous), but then reinterpreted as Cenomanian-Turonian and Cenomanian-Coniacian on the basis of foraminiferal and ostracod assemblages, respectively. Here, we record for the first time in the South Rifian Ridges, some typically Turonian ammonoid and a nautiloid species, namely Romaniceras (Yubariceras) cf. ornatissimum (Stoliczka), Spathites (Jeanrogericeras) cf. reveliereanus (Courtiller), Neoptychites cephalotus (Courtiller), Pachydesmoceras linderi (de Grossouvre), Lewesiceras peramplum (Mantell) and Angulithes galea (Fritsch in Fritsch & Schlönbach). These species are herein described and illustrated. In view of these data, the underlying «Marnes et marno-calcaires jaunes» Formation, formerly dated as Vraconian, could in fact be of a middle to late Cenomanian date, in accordance with the age assignment based on planktonic foraminifera. Deposition of the overlying «Marnes jaunes» Formation, previously dated as Cenomanian-"Senonian", probably started during the latest Turonian or earliest Coniacian.
Fossil shells of the marine bivalve Plagiostoma striatum SCHLOTHEIM sampled from the Middle Trias... more Fossil shells of the marine bivalve Plagiostoma striatum SCHLOTHEIM sampled from the Middle Triassic (so-called Muschelkalk) of Poland demonstrate that, under unfavourable environmental conditions, this species commonly occurring in Triassic German basins exhibits a dwarfed shell. As a consequence of a marine regression episode resulting in a significant increase of salinity and a partial emersion of seafloor these bivalves vanished. The next transgressive pulse caused a re-emergence of these bivalves. They were initially characterized by half-size shells than in the population living prior to the regression episode and, subsequently, during progressive transgression, their shells returned to normal size. Coincidence between eustatic curve and changes in bivalve shell size and their disappearance may be attributed also to biotic interactions, such as a biotic collapse in primary bioproductivity or/and a competition for space or any other resources due to shelf habitat loss during regressive periods.
Proceedings of the Geologists' Association, Apr 1, 2021
Abstract A ‘filament’ event bed/level corresponds to the occurrence of thin elongate calcitic, sh... more Abstract A ‘filament’ event bed/level corresponds to the occurrence of thin elongate calcitic, shells, or plates of pelagic, bivalve or crinoidal, origin, within pelagic, laminated and organic-matter rich limestones. These organic-rich limestones had been generally deposited under hypoxic/anoxic conditions in an outer-ramp environment. These thin elongate, bivalve shells, or crinoidal plates, are found broken in small pieces, disintegrated, or simply preserved parallel to bedding as almost complete specimens. Such ‘filament’ beds were spotted in SE Turkey in deposits, namely the Karababa-A Member, around the Cenomanian-Turonian boundary (C/TB) and above. On a global scale, these filament event beds illustrate sea-level rise related to eustacy and/or climatic change. The abundance of filaments close to the C/TB is a biological marker of high organic productivity resulting from a climatic change to warmer conditions. The prevailing higher sea-level conditions were then favourable to the accumulation and preservation of organic-rich facies, characteristic of the Oceanic Anoxic Event 2 (OAE2). Using both biostratigraphic and carbon isotopic data, those deposits were dated from the latest Cenomanian-Turonian age. ‘Filament’ event beds were recorded in the same order, except for some small differences. A good number of these bio-events are global. Consequently, on a global scale, they are susceptible to constrain the C/TB, especially the base of the Turonian stage, with a significant degree of confidence.
In the northwestern part of the Arabian Platform, the Adıyaman district (SE Turkey) displays some... more In the northwestern part of the Arabian Platform, the Adıyaman district (SE Turkey) displays some Lower-Middle Cenomanian deep-marine sediments of the Derdere Formation. These sediments are yielding abundant echinodermal remains, among which some thecal and brachial plates are assignable to roveacrinids. Routine microfacies analysis of the Lower-Middle Cenomanian part of the Derdere Formation revealed unexpected early Cenomanian assemblages of roveacrinoidal ossicles, comparable with those formerly reported further south in the Cenomanian-Turonian of the Arabian Platform. For the first time, genuine and undisputable Roveacrinidae are illustrated for SE Turkey. Seven borehole sections were scrutinized in search of microcrinoidal sections, most especially within carbonate microfacies. Within the scope of better constraining the position of the Lower-Middle Cenomanian, we had been compiling the successive occurrence of respective identified roveacrinid remains. These roveacrinidal assemblages are consisting in: Roveacrinus communis DOUGLAS (1908) (= R. derdereensis Farinacci & Manni); Roveacrinus cf. alatus DOUGLAS (1908); Roveacrinus spinosus PECK (1943); Roveacrinus sp.; Roveacrinidae indet.; Applinocrinus sp.; and Saccocomidae indet. These specimens provide significant clues to constrain the palaeogeographic reconstruction of Tethyan seaways, and represent potential fossil index candidates for the Lower Cenomanian stratigraphy of the Adıyaman district.
Boletín de la Sociedad Geológica Mexicana, Jul 10, 2018
The Mesozoic carbonate deposits of Mexico yield a number of overlooked, ill-known, and even enigm... more The Mesozoic carbonate deposits of Mexico yield a number of overlooked, ill-known, and even enigmatic microfossils, among which are roveacrinoids (Echinodermata, Crinoidea, Roveacrinida). Most of these pelagic organisms probably came from the central Tethysian seaways, and later on from the early central Atlantic Ocean through the northwestern Tethysian neck, thus reaching the Central American platforms (Comanchean shelf, Central Texas platform, and Coahuila platform) and the Western Interior seaway. The present work intends to enlist as comprehensively as possible the Mexican records of roveacrinid crinoids, to propose a revised interpretation of the sections illustrated (most of them being originally erroneously assigned) and to provide a sound data base for further systematic and biostratigraphic research.
Les microfaunes cenomano-turoniennes de la bordure occidentale du bassin anglo-parisien sont etud... more Les microfaunes cenomano-turoniennes de la bordure occidentale du bassin anglo-parisien sont etudiees sur un profil sud-nord grace a douze coupes de terrain. Celles-ci permettent d'etablir un cadre biochronostratigraphique detaille, ameliorant celui etabli par juignet ; l'analyse des populations microfauniques precise par ailleurs les associations caracteristiques des environnements hypoxiques sur la plate-forme distale. Cette double approche genere un decoupage biostratigraphique fin en rapport avec le detail des observations. Toutes les coupes ont ete etudiees selon le meme standard de detail. L'utilisation des variations quantitatives ou indices (rapport p/b, diversite specifique, indice platycopidique,) pallie l'absence de marqueurs dans certains sites ; elle permet de reconnaitre systematiquement les biochronozones et specialement de positionner la limite cenomano-turonienne. Les indices micropaleontologiques elabores caracterisent les phases de sous-oxygenation dans les depots etudies. Une reconstitution de la frange hypoxique epicontinentale est obtenue grace a l'analyse de leurs variations. L'hypoxie chronique de la mer de la craie turonienne est etablie grace aux donnees chronostratigraphiques auxquelles s'adjoignent les interpretations paleoecologiques. Chaque indice contribue a preciser l'intensite de l'hypoxie. L'hypoxie influence immediatement l'indice platycopidique cependant que les foraminiferes sont moins sensibles, nuancant ainsi les variations de l'hypoxie. Des niveaux hypoxiques homologues sur l'ensemble du profil sont correles au moyen des differents indices. Plusieurs pulsations hypoxiques, allant en s'accentuant, precedent l'evenement global paroxystique ; ce dernier est suivi par d'autres d'importance moindre, allant en s'amortissant. Au sein d'une serie globalement hypoxique, il reste possible de distinguer des pics secondaires qui coincident regulierement avec une montee eustatique. L'intensite de l'hypoxie peut etre liee a l'eustatisme par la recherche du synchronisme entre les variations microfauniques, les fluctuations des elements-traces et les variations du niveau marin. Le modele normand peut donc servir a comprendre le black band britannique qui devrait normalement etre encadre par des niveaux hypoxiques secondaires
New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & T... more New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & TRAPPE) GRANIER et al. reveal the presence of a reproductive structure (ampulla) located on the inner-middle part of each primary lateral. This fact suggests a new interpretation of the alga and the establishment of a new genus: Granieria BARATTOLO & ROMANO, n. gen. Also, the taxonomic status of the other club-shaped specimens from both the High and Middle Atlas of Morocco and the Central Apennines of Italy is reviewed.
The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria i... more The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria is well exposed and rich in macroinvertebrates, including cephalopods. Twenty-five ammonite species and two nautiloid species from the Thénièt El Manchar, Djebel Metrassi and Djebel Bouarif sections are described and seven assemblage zones proposed as provisional working units: Mantelliceras mantelli-Sharpeiceras laticlavium Assemblage Zone (lower Cenomanian), Mantelliceras dixoni Assemblage Zone (uppermost lower Cenomanian), Cunningtoniceras inerme Assemblage Zone (lower middle Cenomanian), Acanthoceras rhotomagense and Acanthoceras cf. rhotomagense Assemblage Zone (middle middle Cenomanian), Acanthoceras amphibolum Assemblage Zone (upper middle Cenomanian), Acanthoceras jukesbrownei Assemblage Zone (uppermost middle Cenomanian), and Neolobites vibrayeanus Assemblage Zone (lower upper Cenomanian). The lower Cenomanian Mantelliceras mantelli-Sharpeiceras laticlavium Zone is subdivided into the Submantelliceras aumalense, Sharpeiceras schlueteri and Mantelliceras saxbii subzones. The base of the middle Cenomanian is marked by the disappearance of species of Mantelliceras and the appearance of the scleractinian coral Aspidiscus cristatus (Lamarck, 1801), associated with Cunningtoniceras inerme (Pervinquière, 1907). The middle Cenomanian contains abundant A. cristatus and species of Acanthoceras, i.e., A. cf. rhotomagense (Defrance in Brongniart, 1822), A. jukesbrownei (Spath, 1926) and A. amphibolum Morrow, 1935. An ammonite zonal scheme is then applied to the Cenomanian exposed in the Bellezma-Aures mountains located on the southern Tethys margin in Algeria.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Un assemblage paléontologique a été récolté dans le Cénomanien du Djebel Metrassi (Batna, NE Algé... more Un assemblage paléontologique a été récolté dans le Cénomanien du Djebel Metrassi (Batna, NE Algérie). Constitué de 327 spécimens, il comporte un corail, 24 espèces de bivalves, 14 espèces de gastéropodes, 3 espèces d'ammonites et 7 espèces d'échinides. Cet assemblage permet d'établir une liste systématique originale, avec des espèces inédites, pour le Cénomanien de ce Djebel et vient soutenir le découpage lithostratigraphique proposé.
As part of a study of the Cenomanian-Coniacian sedimentary succession in the Sergipe Basin in nor... more As part of a study of the Cenomanian-Coniacian sedimentary succession in the Sergipe Basin in northeastern Brazil, microfacies analyses were tested for possible chronostratigraphic application. The common and widespread remains of roveacrinid echinoderms proved useful for intrabasinal biochronostratigraphy. Local dolomitization in the basin, which destroyed most other fossil remains, left the magnesian-calcitic roveacrinid skeletons largely unaffected. Thus, where diagnostic fossils are scarce or lacking, roveacrinids may provide an ancillary means of chronostratigraphic correlation. The forms recorded from Sergipe are described, and a stratigraphic range chart is presented for intrabasinal application, with the possibility of regional or even global correlation either qualitatively (presence/absence patterns) or quantitatively (ecoevent patterns). Several roveacrinid abundance horizons have been reported worldwide in relation to sea level changes and associated hypoxic events, during which roveacrinids developed abundant opportunistic populations. The present study of the Sergipe Basin provides a basis for comparisons and correlations of roveacrinid occurrences in the mid-Cretaceous succession of the South Atlantic continental margin basins and ODP/DSDP drill cores.
Until recently, it has been assumed that pelagic crinoids, the roveacrinids (Roveacrinida, Crinoi... more Until recently, it has been assumed that pelagic crinoids, the roveacrinids (Roveacrinida, Crinoidea), became extinct during the Cretaceous-Paleogene boundary event. Recent finds of well-preserved roveacrinidal remains (brachials and radials) in the Danian (Early Paleogene) of Poland showed that they survived into the earliest Cenozoic. This group was thus characterized as a "dead clade walking". Here, we present fossil evidence that these pelagic crinoids survived in Poland until at least the Middle Miocene (Badenian, ca. 14 Myr ago)-more than 50 Myr after their supposed extinction. These Miocene roveacrinids constitute the first documented evidence of Roveacrinida in strata of Neogene age, thus prolonging the stratigraphic range of pelagic crinoids. This find characterizes the order as a "Lazarus taxon" rather than a "dead clade walking" group.
New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & T... more New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & TRAPPE) GRANIER et al. 2003, reveal the presence of a reproductive structure (ampulla) located on the inner-middle part of each primary lateral. This fact suggests a new interpretation of the alga and the establishment of a new genus: Granieria BARATTOLO & ROMANO, n. gen. Also, the taxonomic status of the other club-shaped specimens from both the High and Middle Atlas of Morocco and the Central Apennines of Italy is reviewed.
Biostratigraphical, geochemical and microfaunal responses to environmental changes around the Cen... more Biostratigraphical, geochemical and microfaunal responses to environmental changes around the Cenomanian-Turonian boundary at Thénièt El Manchar
The Cretaceous Period (145-66 Ma) consisted of several oceanic anoxic events (120-80 Ma), stimula... more The Cretaceous Period (145-66 Ma) consisted of several oceanic anoxic events (120-80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes-e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.
The Wadi Daya Formation, or the «Calcaires crayeux» of the older literature, attains a thickness ... more The Wadi Daya Formation, or the «Calcaires crayeux» of the older literature, attains a thickness of to 40 metres in the Talerhza Basin of the South Rifian Ridges Domain. Previously, this unit was first dated as Vraconian (i.e., mid-Cretaceous), but then reinterpreted as Cenomanian-Turonian and Cenomanian-Coniacian on the basis of foraminiferal and ostracod assemblages, respectively. Here, we record for the first time in the South Rifian Ridges, some typically Turonian ammonoid and a nautiloid species, namely Romaniceras (Yubariceras) cf. ornatissimum (Stoliczka), Spathites (Jeanrogericeras) cf. reveliereanus (Courtiller), Neoptychites cephalotus (Courtiller), Pachydesmoceras linderi (de Grossouvre), Lewesiceras peramplum (Mantell) and Angulithes galea (Fritsch in Fritsch & Schlönbach). These species are herein described and illustrated. In view of these data, the underlying «Marnes et marno-calcaires jaunes» Formation, formerly dated as Vraconian, could in fact be of a middle to late Cenomanian date, in accordance with the age assignment based on planktonic foraminifera. Deposition of the overlying «Marnes jaunes» Formation, previously dated as Cenomanian-"Senonian", probably started during the latest Turonian or earliest Coniacian.
Fossil shells of the marine bivalve Plagiostoma striatum SCHLOTHEIM sampled from the Middle Trias... more Fossil shells of the marine bivalve Plagiostoma striatum SCHLOTHEIM sampled from the Middle Triassic (so-called Muschelkalk) of Poland demonstrate that, under unfavourable environmental conditions, this species commonly occurring in Triassic German basins exhibits a dwarfed shell. As a consequence of a marine regression episode resulting in a significant increase of salinity and a partial emersion of seafloor these bivalves vanished. The next transgressive pulse caused a re-emergence of these bivalves. They were initially characterized by half-size shells than in the population living prior to the regression episode and, subsequently, during progressive transgression, their shells returned to normal size. Coincidence between eustatic curve and changes in bivalve shell size and their disappearance may be attributed also to biotic interactions, such as a biotic collapse in primary bioproductivity or/and a competition for space or any other resources due to shelf habitat loss during regressive periods.
Proceedings of the Geologists' Association, Apr 1, 2021
Abstract A ‘filament’ event bed/level corresponds to the occurrence of thin elongate calcitic, sh... more Abstract A ‘filament’ event bed/level corresponds to the occurrence of thin elongate calcitic, shells, or plates of pelagic, bivalve or crinoidal, origin, within pelagic, laminated and organic-matter rich limestones. These organic-rich limestones had been generally deposited under hypoxic/anoxic conditions in an outer-ramp environment. These thin elongate, bivalve shells, or crinoidal plates, are found broken in small pieces, disintegrated, or simply preserved parallel to bedding as almost complete specimens. Such ‘filament’ beds were spotted in SE Turkey in deposits, namely the Karababa-A Member, around the Cenomanian-Turonian boundary (C/TB) and above. On a global scale, these filament event beds illustrate sea-level rise related to eustacy and/or climatic change. The abundance of filaments close to the C/TB is a biological marker of high organic productivity resulting from a climatic change to warmer conditions. The prevailing higher sea-level conditions were then favourable to the accumulation and preservation of organic-rich facies, characteristic of the Oceanic Anoxic Event 2 (OAE2). Using both biostratigraphic and carbon isotopic data, those deposits were dated from the latest Cenomanian-Turonian age. ‘Filament’ event beds were recorded in the same order, except for some small differences. A good number of these bio-events are global. Consequently, on a global scale, they are susceptible to constrain the C/TB, especially the base of the Turonian stage, with a significant degree of confidence.
In the northwestern part of the Arabian Platform, the Adıyaman district (SE Turkey) displays some... more In the northwestern part of the Arabian Platform, the Adıyaman district (SE Turkey) displays some Lower-Middle Cenomanian deep-marine sediments of the Derdere Formation. These sediments are yielding abundant echinodermal remains, among which some thecal and brachial plates are assignable to roveacrinids. Routine microfacies analysis of the Lower-Middle Cenomanian part of the Derdere Formation revealed unexpected early Cenomanian assemblages of roveacrinoidal ossicles, comparable with those formerly reported further south in the Cenomanian-Turonian of the Arabian Platform. For the first time, genuine and undisputable Roveacrinidae are illustrated for SE Turkey. Seven borehole sections were scrutinized in search of microcrinoidal sections, most especially within carbonate microfacies. Within the scope of better constraining the position of the Lower-Middle Cenomanian, we had been compiling the successive occurrence of respective identified roveacrinid remains. These roveacrinidal assemblages are consisting in: Roveacrinus communis DOUGLAS (1908) (= R. derdereensis Farinacci & Manni); Roveacrinus cf. alatus DOUGLAS (1908); Roveacrinus spinosus PECK (1943); Roveacrinus sp.; Roveacrinidae indet.; Applinocrinus sp.; and Saccocomidae indet. These specimens provide significant clues to constrain the palaeogeographic reconstruction of Tethyan seaways, and represent potential fossil index candidates for the Lower Cenomanian stratigraphy of the Adıyaman district.
Boletín de la Sociedad Geológica Mexicana, Jul 10, 2018
The Mesozoic carbonate deposits of Mexico yield a number of overlooked, ill-known, and even enigm... more The Mesozoic carbonate deposits of Mexico yield a number of overlooked, ill-known, and even enigmatic microfossils, among which are roveacrinoids (Echinodermata, Crinoidea, Roveacrinida). Most of these pelagic organisms probably came from the central Tethysian seaways, and later on from the early central Atlantic Ocean through the northwestern Tethysian neck, thus reaching the Central American platforms (Comanchean shelf, Central Texas platform, and Coahuila platform) and the Western Interior seaway. The present work intends to enlist as comprehensively as possible the Mexican records of roveacrinid crinoids, to propose a revised interpretation of the sections illustrated (most of them being originally erroneously assigned) and to provide a sound data base for further systematic and biostratigraphic research.
Les microfaunes cenomano-turoniennes de la bordure occidentale du bassin anglo-parisien sont etud... more Les microfaunes cenomano-turoniennes de la bordure occidentale du bassin anglo-parisien sont etudiees sur un profil sud-nord grace a douze coupes de terrain. Celles-ci permettent d'etablir un cadre biochronostratigraphique detaille, ameliorant celui etabli par juignet ; l'analyse des populations microfauniques precise par ailleurs les associations caracteristiques des environnements hypoxiques sur la plate-forme distale. Cette double approche genere un decoupage biostratigraphique fin en rapport avec le detail des observations. Toutes les coupes ont ete etudiees selon le meme standard de detail. L'utilisation des variations quantitatives ou indices (rapport p/b, diversite specifique, indice platycopidique,) pallie l'absence de marqueurs dans certains sites ; elle permet de reconnaitre systematiquement les biochronozones et specialement de positionner la limite cenomano-turonienne. Les indices micropaleontologiques elabores caracterisent les phases de sous-oxygenation dans les depots etudies. Une reconstitution de la frange hypoxique epicontinentale est obtenue grace a l'analyse de leurs variations. L'hypoxie chronique de la mer de la craie turonienne est etablie grace aux donnees chronostratigraphiques auxquelles s'adjoignent les interpretations paleoecologiques. Chaque indice contribue a preciser l'intensite de l'hypoxie. L'hypoxie influence immediatement l'indice platycopidique cependant que les foraminiferes sont moins sensibles, nuancant ainsi les variations de l'hypoxie. Des niveaux hypoxiques homologues sur l'ensemble du profil sont correles au moyen des differents indices. Plusieurs pulsations hypoxiques, allant en s'accentuant, precedent l'evenement global paroxystique ; ce dernier est suivi par d'autres d'importance moindre, allant en s'amortissant. Au sein d'une serie globalement hypoxique, il reste possible de distinguer des pics secondaires qui coincident regulierement avec une montee eustatique. L'intensite de l'hypoxie peut etre liee a l'eustatisme par la recherche du synchronisme entre les variations microfauniques, les fluctuations des elements-traces et les variations du niveau marin. Le modele normand peut donc servir a comprendre le black band britannique qui devrait normalement etre encadre par des niveaux hypoxiques secondaires
New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & T... more New observations on abundant material from the type locality of Petrascula iberica (DRAGASTAN & TRAPPE) GRANIER et al. reveal the presence of a reproductive structure (ampulla) located on the inner-middle part of each primary lateral. This fact suggests a new interpretation of the alga and the establishment of a new genus: Granieria BARATTOLO & ROMANO, n. gen. Also, the taxonomic status of the other club-shaped specimens from both the High and Middle Atlas of Morocco and the Central Apennines of Italy is reviewed.
The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria i... more The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria is well exposed and rich in macroinvertebrates, including cephalopods. Twenty-five ammonite species and two nautiloid species from the Thénièt El Manchar, Djebel Metrassi and Djebel Bouarif sections are described and seven assemblage zones proposed as provisional working units: Mantelliceras mantelli-Sharpeiceras laticlavium Assemblage Zone (lower Cenomanian), Mantelliceras dixoni Assemblage Zone (uppermost lower Cenomanian), Cunningtoniceras inerme Assemblage Zone (lower middle Cenomanian), Acanthoceras rhotomagense and Acanthoceras cf. rhotomagense Assemblage Zone (middle middle Cenomanian), Acanthoceras amphibolum Assemblage Zone (upper middle Cenomanian), Acanthoceras jukesbrownei Assemblage Zone (uppermost middle Cenomanian), and Neolobites vibrayeanus Assemblage Zone (lower upper Cenomanian). The lower Cenomanian Mantelliceras mantelli-Sharpeiceras laticlavium Zone is subdivided into the Submantelliceras aumalense, Sharpeiceras schlueteri and Mantelliceras saxbii subzones. The base of the middle Cenomanian is marked by the disappearance of species of Mantelliceras and the appearance of the scleractinian coral Aspidiscus cristatus (Lamarck, 1801), associated with Cunningtoniceras inerme (Pervinquière, 1907). The middle Cenomanian contains abundant A. cristatus and species of Acanthoceras, i.e., A. cf. rhotomagense (Defrance in Brongniart, 1822), A. jukesbrownei (Spath, 1926) and A. amphibolum Morrow, 1935. An ammonite zonal scheme is then applied to the Cenomanian exposed in the Bellezma-Aures mountains located on the southern Tethys margin in Algeria.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Un assemblage paléontologique a été récolté dans le Cénomanien du Djebel Metrassi (Batna, NE Algé... more Un assemblage paléontologique a été récolté dans le Cénomanien du Djebel Metrassi (Batna, NE Algérie). Constitué de 327 spécimens, il comporte un corail, 24 espèces de bivalves, 14 espèces de gastéropodes, 3 espèces d'ammonites et 7 espèces d'échinides. Cet assemblage permet d'établir une liste systématique originale, avec des espèces inédites, pour le Cénomanien de ce Djebel et vient soutenir le découpage lithostratigraphique proposé.
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