Tetrataxidae, Palaeotextulariidae y Biseriamminidae (Foraminiferida) del Mississippiense del Área del Guadiato (Córdoba, España)

En la Sierra de la Estrella (Área del Guadiato, Córdoba) se localiza una sucesión del Viseense superior, principalmente carbonatada, con desarrollo de montículos tipo mud-mound. En esta zona predominan calizas bioclásticas, brechoideas y bioconstruidas, aunque también se localizan niveles de areniscas y conglomerados. Se han identificado un total de 7 litofacies que agrupan a su vez a 9 microfacies tipo: 1.–Mudstonewackestone con cavidades estromatactoideas y fábricas fenestrales, 2. Wackestonepackstone con algas y bioclastos, 3.1.–Packstone de pseudopeloides, 3.2.–Packstone con algas, pseudopeloides y litoclastos, 4.1.–Packstone de briozoos y crinoideos, 4.2.–Packstone con algas y espículas, 5.–Packstone-rudstone de litoclastos, 6.–Grainstone de cortoides y litoclastos, 7.–Arenitas híbridas. El ambiente de sedimentación se interpreta como una zona de transición entre rampa interna y externa carbonática con influencia de terrígenos y desarrollo de montículos microbianos. [ABSTRACT] Late Viséan calcareous rocks containing buildups occur in the Sierra de la Estrella, Guadiato Valley. Bioclastic, breccioid and biohermal limestones as well as sandstones and conglomerates occur. Lithofacies analysis allow to identify 7 types, with 9 characteristic microfacies: 1.–Micropeloidal mudstone-wackestone with stromatactoid cavities and fenestral fabrics, 2.–Algal-bioclastic wackestone-packstone, 3.1.–Pseudopeloidal packstone, 3.2.–Packstone with algae, pseudopeloids and lithoclast, 4.1.–Bryozoal-crinoidal packstone, 4.2.–Packstone with algae and sponge spiculae, 5.–Packstone-rudstone with lithoclasts, 6.–Cortoid-lithoclasts grainstone, 7.–Hybrid sandstones. Sediments are attributed to a inner to outer carbonate ramp with sporadic terrigenous influence. Some microbial mounds developed in such environment

Two new Late Viséan (Mississippian) species of the genera Nevillea and Mikhailovella (Foraminiferida) from the Guadiato Area (SW Spain)

Two new endemic species from the Guadiato Area are described in this work, Nevillea cordobensis and Mikhailovella fresnedosensis. These species range from the Late Viséan foraminiferal zones 14 to 15 (V3a-V3bα-β-γinf o Cf5 Cf6α-β-γ inf). The first occurrence of Mikhailovella from Zone 14 is controversial, because its first occurrence is usually used as biomarker from Zone 15. Analysis of the rest of the foraminiferal assemblages from the same levels also suggests that the first occurrence of this genus is at the base of the Late Viséan. [RESUMEN] En este trabajo se describen dos nuevas especies de foraminíferos endémicos del Área del Guadiato, Nevillea cordobensis y Mikhailovella fresnedosensis. Estas especies tienen un rango estratigráfico que abarca las zonas 14 y 15 de foraminíferos (V3a-V3bα-β-γinf o Cf5 Cf6α-β-γ inf), ambas en el Viseense superior. La aparición de Mikhailovella desde la Zona 14 es un dato controvertido, ya que se considera como un taxon guía de la Zona 15. El análisis del resto de las asociaciones de foraminíferos pertenecientes a los mismos niveles sugiere que la aparición de este género desde la base del Viseense superior

Biozonas de foraminíferos de la Sierra del Castillo (banda central de la Cuenca del Guadiato, Córdoba)

Se estudian los afloramientos calcáreos de la Sierra del Castillo (Córdoba), abordando el trabajo desde un aspecto tanto sedimentológico como bioestratigrálico, mediante el análisis de los 26 tramos litológicos reconocidos en dos secciones estratigráficas, la de la Cantera y la del Collado El análisis de las facies da como resultado la reconstrucción de tres ambientes sedimentarios, llanura intermareal, llanura submareal y plataforma somera. Dentro de los cuales se pueden diferenciar subambientes y cuerpos sedimentarios, como puede ser barras, rellenos de canales, «ripples>, etc. La secuencia define cinco efectos regresivos y cuatro transgresivos, que no dejan discontinuidades estratigráficas de gran importancia, quedando por lo tanto un registro bastante continuo. El estudio sistemático de los foraminíferos nos da como resultado un total de 19 familias representadas con un total de 75 géneros; a partir de estos, vamos a definir con más precisión la bioestratigrafía de los afloramientos, que inicialmente están datados como Viseense Superior-Namuriense Inferior, y que concretaremos en el Viseense ter- minal, comprendido entre las zonas de foraminíferos 15 y 16 de MAMET. [ABSTRACT] The calcareous outcrops of the Sierra del Castillo (Córdoba) are studied, involving sedimentological biostratigraphical works, with the analysis of the 26 recognized levels in two sections, the Cantera and the Collado. The reconstruction of three sedimentary enviroments, intertidal flat, subtidal flat and shallow shelf is obtained from the analysis of the facies. Inside these, local environments and sedimentary bodies can be distinguished, like shoals, chanels filling, ripples, etc. The sequence define five regressive efects and four transgressive ones which not represent significative estratigraphic discontinuities, so the record is rather continous. The foraminifer sistematic studyresults in 19 represented families and 75 genera; we will define with more precision thebiostratigraphy of the ourcrops, which initially are dated as Late Viséan-Early Namurian and we will centre in Latest viséan, foraminiferal zones 15 and 16 of MAMET

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

Early Serpukhovian conodonts from the Guadiato Area (Córdoba, Spain)

The conodont assemblages of three stratigraphic sections from lower Serpukhovian rocks of the Guadiato Area (southwestern Spain) are composed of fifteen taxa, included in nine genera. Many of them are identified in open nomenclature due to the poor preservation of the specimens, of which most of them are fragmented, the presence of juvenile specimens, and the current controversy in the recognition of some multielement apparatuses. Generally, the faunas are not highly diversified and there is a low abundance of specimens in the horizons that yield conodonts. The assemblages include: Cavusgnathus navicula, Cavusgnathus cf. navicula, Gnathodus girtyi, of which two subspecies were identified, Gnathodus girtyi girtyi and Gnathodus girtyi meischneri, Hindeodontoides? sp., Hindeodus cristula, Idioprioniodus healdi, Idioprioniodus spp., Kladognathus macrodentata?, Kladognathus tenuis-complectens, Lochriea? sp., Mestognathus bipluti, Synclydognathus geminus, Synclydognathus spp. and many unidentifiable fragments

Middle to Late Mississippian and Early Pennsylvanian foraminiferal zonal scheme of South China—a case study from the Youjiang Basin: biostratigraphical and palaeobiogeographical implications

Ten foraminiferal zones are proposed in the Youjiang Basin (South China): Pojarkovella, Pojarkovella nibelis-Endothyranopsis compressa, Cribrospira panderi-Eostaffella ikensis, Climacammina, Janischewskina delicata, Eostaffellina decurta, Bradyina cribrostomata, Eostaffellina actuosa-Eostaffellina protvaensis, Plectostaffella and Pseudostaffella antiqua zones. These zones span the interval from the middle Viséan to the late Serpukhovian in a continuous succession, and above, a final zone characteristic of the Severokeltmian Substage in the middle part of the early Bashkirian. These zones are compared with other foraminiferal zones described from China, particularly with those from South China and allow to uniformize the foraminiferal stratigraphical records in the region, and to standardize the foraminiferal zones defined in those regions. The stratigraphical range of some taxa is still debated, but the Viséan-Serpukhovian and the lower-upper Serpukhovian boundaries are well constrained by well-known cosmopolitan taxa. Foraminifers during the lower Middle Mississippian (middle Viséan to the earliest late Viséan) are more similar to the foraminiferal assemblages described from Western Europe, whereas from the upper Middle to Late Mississippian (i.e. latest Viséan-Serpukhovian) are more similar to those in the Russian Platform, and thus, the use of the Russian zonal scheme and biostratigraphy is more practical than to use the biozones defined in Western Europe

Inventory and analysis of the distribution of Viséan corals from the Guadiato Area (Córdoba, SW Spain)

he coral content of the Visean rocks from the Guadiato Area (SW Spain) have been studied during the last 25 years. Part of the coral assemblages have been previously described, but never as whole. The 69 recorded coral species belonging to Rugosa, Tabulata and Heterocorallia are illustrated. The family Antiphyllidae is represented by two genera and three species; the family Laccophyllidae is represented by one species; the family Cyathaxoniidae is represented by one genus and two species; the family Amplexidae is represented by one species; the family Zaphrentoididae is represented by one species; the family Plerophyllidae is represented by one species; the family Polycoeliidae is represented by one species; the family Pentaphyllidae is represented by one species; the family Cyathopsidae is represented by four genera and five species; the family Bothrophyllidae is represented by one species, the family Aulophyllidae is represented by nine genera and ten species; the family Palaeosmiliidae is represented by four genera and four species; the family Lithostrotionidae is represented by five genera and sixteen species; the family Axophyllidae is represented by three genera and thirteen species; the family Geyerophyllidae is represented by one species; the family Heterophyllidae is represented by two genera and two species; the family Syringoporidae is represented by one species; the family Multithecoporidae is represented by one genus and three species; the family Syringolitidae is represented by one species; the family Pyrgiidae is represented by one species. The degree of abundance and diversity is regarded as moderate and the degree of endemism is low. The significance of the coral assemblages for biostratigraphy, palaeobiogeography and environmental palaeontology is analysed

A new early Visean coral assemblage from Azrou-Khenifra Basin, central Morocco and palaeobiogeographic implications

A new early Visean coral assemblage has been recorded from turbidite facies in the southern part of the Azrou-Khenifra Basin, northwest of Khenifra, central Morocco. The newly discovered Ba Moussa West (BMW) coral fauna includes Siphonophyllia khenifrense sp. nov., Sychnoelasma urbanowitschi, Cravenia lamellata, Cravenia tela, Cravenia rhytoides, Turnacipora megastoma and Pleurosiphonella crustosa. The early Visean age of the coral assemblage is supported by foraminiferal and conodont data, with the recognition of the basal Visean MFZ9 Zone. This confirms that the first transgression in the Azrou-Khenifra Basin was during the earliest Visean. The allochthonous coral assemblage was recovered from coarse-grained proximal limestone debris flow and turbidite beds within a fault-bounded unit, lying to the west of a thrust syncline containing upper Visean limestones. No evidence exists of the former early Visean shallow-water platform from which the corals were derived. All other in situ platform carbonate rocks around the southern margin of the Azrou-Khenifra Basin are probably of late Visean (Asbian–Brigantian) age. The early Visean Ba Moussa West coral fauna can be compared with that at Tafilalt in eastern Morocco, as well as in other Saharian basins of Algeria. Many of the genera and species in the Ba Moussa West assemblage are identical to those in NW Europe, with which it must have had marine connections. The new rugose species described, Siphonophyllia khenifrense, is probably endemic to North Africa. Its ecological niche in NW Europe was occupied by S. cylindrica or S. aff. garwoodi

Coral assemblages of the Serpukhovian–Bashkirian transition from Adarouch (Morocco)

The Carboniferous outcrops from Adarouch (central Morocco) are composed of siliciclastic and carbonate rocks, and the latter have yielded abundant fossils. The upper part of the marine succession in the Idmarrach Formation and its laterally equivalent Tirhela Formation belong to the Bashkirian. More recent investigations of poorly preserved coral assemblages from the upper part of Idmarrach 2 section and the upper part of the Tirhela Formation are here described. The assemblage from the upper Idmarrach Formation comprises several typical Mississippian taxa, such as Aulophyllum fungites, Dibunophyllum bipartitum, Koninckophyllum interruptum, Siphonodendron scaleberense and Lithostrotion decipiens, and some highly evolved forms previously undescribed of Mississippian genera such as Haplolasma sp., Arachnolasma sp., Siphonodendron sp., Diphyphyllum sp., Solenodendron sp., Clisiophyllum sp. and a new species Corwenia tirhelensis sp. nov. In addition, an undetermined petalaxid has been also recorded. Similarly, the assemblage from near the top of the Tirhela Formation yielded some species regarded usually as Mississippian, such as Palaeosmilia murchisoni and Lithostrotion decipiens. We also identified the long-ranging tabulate Syringopora sp., Corwenia tirhelensis sp. nov., and a single species of the fasciculate rugosan, Siphonodendron tindoufense, previously described from Bashkirian rocks in the Tindouf Basin (southern Morocco). The presence of the latter taxon in both the Idmarrach and Tirhela sections implies a communication between the Adarouch region and the Saharan basins. The occurrence of S. tindoufense at the approximately same stratigraphic level in Tindouf, Taoudenni, Reggan-Ahnet and Adarouch, demonstrates its important regional stratigraphic value in North Africa

Diagenetic and Biological Overprints in Geochemical Signatures of the Gigantoproductus Tertiary Layer (Brachiopoda): Assessing the Paleoclimatic Interpretation

Variations in the geochemical signatures of fossil brachiopod shells may be due to diagenesis and/or biological processes (i.e., ‘vital effects’). It is critical to characterise them in order to identify reliable shell areas suitable for paleoclimate studies. This investigation contributes to an in-depth understanding of geochemical variations in Gigantoproductus sp. shells (SW Spain, Serpukhovian age), throwing light onto the Late Paleozoic Ice Age interpretation. Microstructural, crystallographic, cathodoluminescence and geochemical (minor and trace elements, δ18O, δ13C, and strontium isotopes) characterisations have been performed on the tertiary layer of the ventral valve, to assess the preservation state. Poorly preserved areas exhibit microstructural and geochemical changes such as recrystallisation, fracturing and higher Mn and Fe enrichment. Moreover, these areas have a higher dispersion of ⁸⁶Sr, ⁸⁷Sr, δ18O and δ13C than well-preserved areas. Three structural regions have been identified in well-preserved areas of the ventral valve by differences in valve curvature and thickness, such as the umbonal and thick and thin regions. These regions have different proportions of Mg, S, Na, δ18O, and δ13C, which are interpreted as ‘vital effects’ and probably related to growth-rate differences during shell growth. The Gigantoproductus tertiary layer seems the most suitable for paleoclimate studies, because it retains the original microstructure and geochemical composition