Récifs, trottoirs et autres biolithosores du bassin de San Miguel de Salinas

International audienceLe bassin de San Miguel de Salinas, situé dans la région du Levant espagnol à l'extrémité des Cordillères Bétiques, comporte trois groupes principaux de dépôts messiniens : - des marnes à Foraminifères planctoniques, - des faciès diversifiés dits du "Messinien préévaporitique" constitués de dépôts marneux, de bancs gréseux, de constructions récifales à Porites et Algues rouges dominantes, de niveaux d'estran à Hermelles qui seront exposés dans les deux premiers chapitres de cette note et enfin de marnes polychromes lagunaires à charophytes. - des faciès du "Messinien évaporitique" rythmés par des séquences où se succèdent : (a) des Stromatolithes; (b) des calcaires blancs oolithiques et sableux de dépôts de plages. C'est au sein de ce membre que s'individualisent des microséquences à Vermets-stromatolithes qui sont l'objet du dernier point de cette communication. (c) des sables jaunes à langues de progradation correspondant probablement à des "fan-deltas" ; (d) des marnes de décantation azoïques ou à rares organismes planctoniques et benthiques ; (e) des gypses sélénites toujours développés en fin de séquence. L'un des points remarquables de ce bassin messinien à terme évaporitique est l'abondance et la diversité des bioconstructions aussi bien avant que pendant l'événement messinien. Trois types de bioconstructions sont ici décrites et interprétées en terme de paléoenvironnement: - Des récifs à Porites et Algues rouges dont l'état de conservation a permis d'effectuer une zonation récifale comportant 6 unités s'échelonnant du frontolittoral au prélittoral. Des précisions bathymétriques et paléoenvironnementales sont fournies. - Une séquence type comportant des biolithosores à Sabellariidae (Annélides agglutinants) est présentée, suivie d'une description des biohermes et de la microstructure des tubes. Ces bioconstructions caractérisent un paléoenvironnement intertidal inférieur dont les eaux sont à salinité normale à légèrement dessalé. L'extrême rareté de ces constructions à Hermelles dans les périodes géologiques mérite d'être signalée

INSOLENTITHECA EMEND., PROTO INSOLENTITHECA N. GEN., AND CALIGELLIDAE EMEND., PERMANENT CYSTS OF PALAEOZOIC FORAMINIFERA?

Insolentitheca was interpreted as a microproblematicum, a foraminiferal test, or a syzygial cyst. Arguments are listed versus syzygial cysts or ordinary foraminiferal agglutinates, and for permanent cysts with probable infaunal life. Protoinsolentitheca fundamenta n. gen. n. sp. is described, which links Insolentitheca and the Caligellidae. Some elements of nomenclature are introduced to describe the particular tests of the Caligellidae. These taxa could be basically represented by an infaunal naked or chitinaceous foraminifer, which secretes during its lifetime a calcified perimeter denominated the chimney, only present in the Caligellidae. To this initial secretion are added two types of "agglutinated" and bioeroded tests: the fundamental in Protoinsolentitheca and Insolentitheca, and the bricks, in Insolentitheca only.

SMALLER FORAMINIFERS, CHARACTERISTIC ALGAE AND PSEUDO-ALGAE OF THE LATEST CARBONIFEROUS-EARLY PERMIAN RATTENDORF GROUP,CARNIC ALPS (AUSTRIA/ITALY)

Limestones of the latest Carboniferous-early Permian Rattendorf Group (Lower Pseudoschwagerina Limestone, Grenzland Formation and Upper Pseudoschwagerina Limestone) of the Carnic Alps (Austria/Italy) contain a rich and interesting assemblage of smaller foraminifers, algae and pseudo-algae. The foraminiferal assemblage of the Lower Pseudoschwagerina Limestone is identical to that of the Auernig Formation. The Grenzland Formation is characterized by the appearance of the genus Geinitzinaand Pseudovermiporella, and the disappearance of Bradyinidae. The Upper Pseudoschwagerina Limestone contains the same species as the Grenzland Formation, but is characterized by the local appearance of Neoendothyra (?) and diverse species of Hemigordiidae and Nodosarioidea. The biostratigraphical value of diverse species of Hemigordius, ìArenovidalinaîsensu Baryshnikov = ìNeohemigordiusîsensu Pinard & Mamet, Nodosinelloides, Protonodosariaand Geinitzinafor the Asselian and early Sakmarian stages is briefly discussed. The systematical part contains some generic remarks on the Hemigordiidae and Nodosarioidea. Due to the porcelaneous wall, the microfossils Ellesmerellapermica(Pia) (= ìGirvanellaî subparallelaFlügel & Flügel-Kahler) and Pseudovermiporella spp., which are generally interpreted as algae, are considered as attached miliolinid foraminifera. A new genus of problematical Chlorophyta, Homannisiphon,is established.&nbsp

MICROFACIES AND MICROFOSSIL ASSEMBLAGES (SMALLER FORAMINIFERS, ALGAE, PSEUDOALGAE) OF THE HUECO GROUP AND LABORCITA FORMATION (UPPER PENNSYLVANIAN-LOWER PERMIAN) SOUTH-CENTRAL NEW MEXICO, USA

During the latest Carboniferous and earliest Permian (Virgilian-Wolfcampian), the eastern margin of the Orogrande Basin in south-central New Mexico was rimmed by a narrow, tectonically unstable shelf, on which sediments of the Laborcita and Abo formations were deposited. Sediments of the Hueco Group accumulated on the more stable western margin of the Orogrande Basin. On the eastern shelf, the Laborcita Formation of the northern Sacramento Mountains represents a transition from marine to terrestrial facies and is composed of clastic-carbonate cycles. Limestones accumulated during relative sea-level highstands in a shallow marine shelf environment. Clastic sediments were deposited during relative lowstands when there was strong clastic influx in a nearshore to terrestrial environment. The overlying Abo Formation is composed of terrestrial red beds. On the western shelf, the Shalem Colony Formation of the Hueco Group, equivalent to the Laborcita Formation, is composed of mostly normal marine shallow shelf limestones with only minor interbedded clastics. The Robledo Mountains Formation and Hueco Group reflects a trend from a restricted shallow  shelf and tidal flat clastics facies in the lower part to more open conditions in the upper part, which also prevailed during deposition of the overlying Apache Dam Formation. Limestones of the Laborcita Formation and Hueco Group contain smaller foraminifers, algae and problematic carbonate microfossils. All taxa except two pseudoalgae in open nomenclature (Litostroma (?) sp. and “problematicum gen. 1”) are taxa already described. Compared with the Carnic Alps (Austria/Italy), the assemblages of smaller foraminifers of the Laborcita Formation  and Shalem Colony Formation are very similar to those of the Auernig and Carnizza Formations (Auernig Group), and Lower Pseudoschwagerina Limestone (Rattendorf Group), indicating an Orenbugian (“Bursumian”) to Asselian age. Smaller foraminifers of the Robledo Mountains Formation allow correlation with the Grenzland Formation and Upper Pseudoschwagerina Limestone (Rattendorf Group) of the Carnic Alps, dated as Asselian to Sakmarian. Smaller foraminifers of the Apache Dam Formation suggest an Artinskian age, correlating with the Wolfcampian, or the Trogkofel Group of the Carnic Alps.  &nbsp

New evidence for Hercynian faulting in the southernmost margin of the Rharb Basin (Morocco)

Abstract The Miocene-Pliocene Rharb Basin has important groundwater and hydrocarbon potential in western Morocco. The Pliocene-Quaternary reservoir rests upon the Miocene-Pliocene marly units. The paleogeographic limits are based on planktonic foraminifera biozones. They contributed to the geometric reconstruction of this basin. The goal of the present study is to establish the paleogeographic evolution of the Rharb Basin and the Hercynian structures deduced from seismic and gravity data interpretation. The Pliocene-Quaternary deposits exhibit thickness and lateral facies variations. The Pliocene bathyal gulf showed several tectonic phases, marked by the westward migration of the paleogeographic limit in its eastern part, and a southward migration from its northern one. During Miocene-Pliocene times, the tectonic activity within the study area is characterized by extensional and compressional structures. The faults affecting the Paleozoic units were reactivated several times. The comparison between the paleogeographic limits and identified Hercynian structures constitutes fresh evidence for reactivation of pre-existing Hercynian faults

SMALLER FORAMINIFERS FROM THE LOWER PERMIAN EMARAT FORMATION, EAST OF FIRUZKUH (CENTRAL ALBORZ, IRAN)

The uppermost Carboniferous-Lower Permian Dorud Group of the Gaduk section in Central Alborz (Iran) is more than 44 m-thick; it includes thick succession of conglomerates, quartzarenites, calcareous sandstones, oncolitic fusulinid limestones, sandy limestones, sandstones and shales. The Toyeh, Emarat and Shah Zeid formations of this Group were dated from the Gzhelian to the Sakmarian. A review of the uppermost Gzhelian, Asselian and lower Sakmarian smaller foraminifers of the Emarat Formation of the Gaduk section is here presented. Three foraminiferal biozones are defined: the Nodosinelloides shikhanica-Geinitzina primitiva Zone is latest Gzhelian in age; the Nodosinelloides spp.-Geinitzina spp.-Pseudoacutella partoazari Zone is Asselian; the Rectogordius iranicus gadukensis-Endothyra cf. bamberi Zone is early Sakmarian in age. A new subspecies Rectogordius iranicus gadukensis n. subsp. is described, and the genera Pseudovidalina and Grovesella are discussed. The studied assemblages are correlated with those from the Carnic Alps (Austria-Italy), East European Platform of Russia, the Urals (Russia), Darvaz (Uzbekistan), the northern and central Pamirs (Tajikistan), Central Iran, northern Afghanistan and other classical regions of the Tethyan realm

Foraminifères et algues calcaires dans les roches brigantiennes comme guides pour la reconnaissance de l'intervalle de la limite Viséen-Serpukhovien du Maroc.

Revision of foraminifers, algae and problematic algae of well-known late Viséan formations in the Jerada syncline in the Eastern Meseta, Azrou-Khenifra Basin in the Central Meseta and Oued Cherrat in the Western Meseta, suggests that the recognition of the chronostratigraphic units within this period lacks most of the foraminiferal markers in the Western European foraminiferal biozonations. Many taxa recorded in the Moroccan Meseta are considered as late Asbian guides in Western Europe, but in the Meseta, they are first recorded in the early Brigantian. Although some foraminiferal taxa are proposed as guides for the early Brigantian in Morocco, this substage is far more easily recognized by the algal and problematic algal assemblages. In contrast, the late Brigantian, and thus, the equivalent to the lower part of the Serpukhovian, is recognized by typical foraminifers that have been also recorded in Western Europe. Moreover, the algae do not display any significant change at this level. The unusual and unrepresentative foraminiferal assemblages recorded from the Brigantian in Morocco, suggest that most of the numerous outcrops and sections ascribed to the late Asbian in the literature should be revised because, as is demonstrated in a few cases in this study, those outcrops probably belong to younger Brigantian chronostratigraphic units.Une révision des foraminifères, des algues et des algues problématiques dans les formations bien connues du Bassin de Jérada (Méséta orientale), du Bassin d’Azrou-Khenifra (Méséta centrale) et de l’Oued Cherrat (Méséta occidentale), révèle que l’identification des unités chronostratigraphiques durant le Viséen supérieur est rendue difficile par l’absence fréquente des foraminifères-guides dont on dispose dans les biozonations d’Europe occidentale. La plupart des taxons trouvés dans la Méséta marocaine pourraient être considérés comme des guides de l’Asbien supérieur, tels qu’en Europe occidentale, mais dans la Méséta ils ne se rencontrent qu’au cours du Brigantien inférieur. Bien que des foraminifères aient été proposés comme guides du Brigantien inférieur au Maroc, ce sous-étage se caractérise plus aisément par les assemblages d’algues et d’algues problématiques. Au contraire le Brigantien supérieur, et donc la base du Serpukhovien, est facilement reconnaissable grâce à des foraminifères qu’on trouve aussi en Europe occidentale, alors que les algues ne montrent aucun chan-gement significatif durant cette période. Les associations typiques et atypiques de foraminifères qu’on trouve au Brigantien incitent à penser que nombre de coupes et d’affleurements attribués à l’Asbiensupérieur, dans la littérature marocaine, sont à reviser, car, comme cela est prouvé en quelques caspar cette étude, de tels affleurements pourraient appartenir à des unités chronostratigraphiques plusrécentes du Brigantien.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Ciencia, Innovación y Universidadespu

New data on the incertae sedis biota and foraminifera of the mid-Famennian Baelen Member (Late Devonian, eastern Belgium)

The Baelen mud mounds in eastern Belgium represent a local member of the mid-Famennian Souverain-Pré Formation (an important carbonate interval within the Condroz Sandstone Group). The lower part of this member contains silty bioclastic wackestones and packstones that are particularly rich in the problematical algae Serrisinella and Dreesenullella. Plurilocular foraminifera (Septabrunsiina and Baelenia) and rare solitary rugose corals (Neaxon? sp.) occur within crinoidal grainstones (tempestites) interfingering with the latter bioclastic wacke-/packstones and red-stained stromatactoid spiculitic mudstones (carbonate mound core facies). Although Serrisinella is quite common in other mid- and late Famennian limestones, of Belgium, Dreesenulella is almost endemic of the Baelen Member. Both genera apparently inhabited the muddy sediment-water interface, constituting meadows probably in zones of intermittently strong bottom currents. The taxonomic similarities between Dreesenulella and Saccamminopsis are discussed, as well as their possible affinities with the Xenophophyrea and Kokomiacea. Moreover, the first stages of the Septabrunsiina–Baelenia foraminiferal lineage are analysed in detail. The taxonomic and palaoecological positioning of Serrissinella and Dreesenulella adds to the discussion about the palaeobathymetry of the Baelen mud mounds and corroborates sedimentological evidence for their relatively shallow carbonate ramp depositional setting

DISCUSSION SUR L'AGE MURGABIEN OU MIDIEN DES SERIES PERMIENNES DU JEBEL TEBAGA (SUD DE LA TUNISIE)

A biostratigraphical analysis of Jebel Tebaga (Tunisia) is given. The Permian is divided in two zones: Afghanella zone of Middle-Upper Murgabian age; and Neoschwagerina, Yabeina and Dunbarula zone of Upper Murgabian- Lower Midian age, himself divided in a lower subzone with Dunbarula nana and an upper subzone wirh Dunbarula mathieui and Codonofusiella