Revision and new data of the ammonite family Pseudotissotiidae in the Iberian Trough, Spain

The ammonites assigned to the family Pseudotissotiidae of the Wiedmann (Tübingen,Germany) and Goy, Carretero and Meléndez (Madrid, Spain) collections obtained from the Iberian Trough have been revised. New, mainly lower Turonian, specimens of the species Pseudotissotia sp., Choffaticeras (Choffaticeras) quaasi (Peron, 1904), C. (C.) pavillieri (Pervinquière, 1907), C. (C.) segne (Solger, 1903), C. (C.) sinaiticum (Douvillé, 1928), C. (Leoniceras) luciae (Pervinquiére, 1907), C. (L.) barjonai (Choffat, 1898), Wrightoceras llarenai (Karrenberg, 1935), W. munieri (Pervinquière, 1907), W. submunieri Wiedmann, 1975b, and Donenriquoceras forbesiceratiforme Wiedmann, 1960, have been also presented. In addition, we designate and refigure the lectotype of Pseudotissotia (Leoniceras) alaouitense Basse, 1937, and refigure the lectotype of P. barjonai Choffat, 1898. Studies on the morphologies and the geographical and temporal distributions of all of these species have led to the identification of several phylogenetic relationships between them, and to distinguish four main phases in the evolution of the family, characterized by the successive dominance of Choffaticeras (Choffaticeras), Choffaticeras (Leoniceras), Donenriquoceras and Wrightoceras with Donenriquoceras

The ammonite genera Fagesia and Neoptychites (family Vascoceratidae) in the Iberian Trough, Spain

The ammonites assigned to the genera Fagesia Pervinquière, and Neoptychites Kossmat, of the Wiedmann (Tübingen, Germany) and Goy, Carretero and Meléndez (Madrid, Spain) collections obtained from the Iberian Trough have been revised. New mainly lower Turonian specimens of the species Fagesia catinus (Mantell), F. tevesthensis (Peron), F. rudra (Stoliczka), F. superstes (Kossmat), F. pachydiscoides Spath, and Neoptychites cephalotus (Courtiller) have also been presented. In addition we have described one new species: F. mortzestus. Studies of the morphologies and the geographical and stratigraphical distributions of all these species have led to the identification of several phylogenetic relationships between them, and to distinguishing one main phase in the evolution of the family Vascoceratidae Douvillé, characterised by the dominance of Fagesia with Neoptychites

Characterization of Choffatirhynchia nov. gen. (Brachiopoda, Rhynchonellida) in the Toarcian (Jurassic) of the Iberian Range (Spain)

Se describen y caracterizan Choffatirhynchia nov. gen. y las dos especies que se incluyen en él: C. vasconcellosi (CHOFFAT in DUBAR, 1931) y C. turolensis nov. sp., discutiéndose las afinidades y diferencias de este género con otros géneros próximos, como Homoeorhynchia BUCKMAN, 1918, Rhynchonelloidea BUCKMAN, 1918, Quadratirhynchia BUCKMAN, 1918 y Globirhynchia BUCKMAN, 1918. Se precisa la distribución estratigráfica, en la Cordillera Ibérica, de C. vasconcellosi y de C. turolensis, en relación con la bioestratigrafía de detalle de dos secciones expandidas representativas del Toarciense del sector central de la cordillera (Sección de la Rambla del Salto y Sección de Ariño), en las que se han estudiado las asociaciones de ammonoideos y braquiópodos. Los datos obtenidos en la Cordillera Ibérica, junto con los proporcionados por diferentes autores en otras cuencas del Tethys Occidental, han permitido establecer la distribución paleobiogeográfica de las especies de Choffatirhynchia, que se conocen en la Península Ibérica, Sureste de Francia y Norte de África.Choffatirhynchia nov. gen. is described and characterized, together with the two species included in the new genus, C. vasconcellosi (CHOFFAT in DUBAR, 1931) and C. turolensis nov. sp. The genus Choffatirhynchia includes medium-sized rhynchonellids, that present a subtetrahedral to globose shell, with the dorsal valve more convex than the ventral valve, a subrectangular dorsal fold, and numerous and dense ribs covering the whole shell; the beak is suberect, narrow and pronounced, with a big foramen; the areas are weak and not depressed; a narrow and shallow septalium, and raduliform crura are present. Choffatirhynchia is distinguished from Homoeorhynchia BUCKMAN, 1918 and Rhynchonelloidea BUCKMAN, 1918, taken as closest from a morphological point of view, in its wider and lower dorsal fold and denser costulation. It differs from Quadratirhynchia BUCKMAN, 1918, a genus to which C. vasconcellosi had previously been assigned occasionally, in the suberect beak and the absence of depressed planareas and squama-glotta. It is distinguished from Globirhynchia BUCKMAN, 1918, in which some species present a rimmed foramen similar to that found in C. turolensis, for having a less convex ventral valve as compared to the dorsal valve. The stratigraphical distribution in the Iberian Range of C. vasconcellosi and of C. turolensis is accurately established on the basis of the detailed biostratigraphy of two expanded sections representative of the Toarcian of the central sector of this mountain range (section of Rambla del Salto and section of Ariño), in which both ammonoid and brachiopod associations have been studied. C. vasconcellosi, the type species of the genus, is recorded in the Iberian Range in the Serpentinus Zone and in the Laticosta Subzone of the Bifrons Zone of the Toarcian. It is found in the same stratigraphic position in the Coastal-Catalan Range, in the Pyrenees, in the Balearic Islands (Minorca), in the Lusitanian Basin in Portugal and in the Middle Atlas in Morocco. C. turolensis nov. sp. is recorded in the Iberian Range from the Bifrons Zone (Bifrons Zubzone) to the Insigne Zone (Insigne Subzone) of the Toarcian; its presence in the Pyrenees and in southeastern France is also probable. C. vasconcellosi is a frequent species in the brachiopod associations that characterise the Spanish Bioprovince of brachiopods, recognised along several basins of the Western Tethys. C. turolensis nov. sp. is, on the contrary, a species of a more restricted distribution and is recorded at a time of low diversity in the whole region.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEEspaña. Ministerio de Ciencia y TecnologíaConsejo Superior de Investigaciones Científicas (España)pu

Warming-driven mass extinction in the Early Toarcian (Early Jurassic) of northern and central Spain. Correlation with other time-equivalent European sections

Causes of the major mass extinction recorded during the Early Toarcian (Early Jurassic) are controversial. Many authors have concluded that the mass extinction is caused by the widespread oceanic anoxia derived from a postulated Early Toarcian Oceanic Anoxic Event (ETOAE), supposedly synchronous in all basins and global in extent. Another group of papers links the mass extinction with a major climate change that occurred synchronously with the mass extinction. The results of the study of five sections of the uppermost Pliensbachian and Lower–Middle Toarcian deposits, located in northern and central Spain are presented. Detailed ammonite-based biostratigraphy, coupled with stable isotope analysis of belemnite calcite and bulk carbonates, as well as total organic carbon (TOC) analyses have been performed in all sections. Records of the vertical distribution of mainly benthic fossils have been compiled in four of the studied sections. Results obtained in the Spanish outcrops have been compared and correlated with other European sections. The excellent mutual relation between the patterns of the Early Toarcian progressive warming and the concomitant progressive losses of species evidences a cause-and-effect relationship between the increase of temperature and the mass extinction. From an uppermost Pliensbachian cooling interval, warming started at the Lower Toarcian Tenuicostatum Zone. Increase of average seawater palaeotemperature is associated with a progressive and substantial drawdown in the number of species of nektonic, planktonic and benthic organisms, representing the extinction interval. A prominent increase in seawater temperature occurred around the Lower Toarcian Tenuicostatum–Serpentinum zonal boundary. Average temperatures at the Serpentinum Zone increased about 7 °C, marking the extinction boundary. The high temperatures continued during the Middle Toarcian Bifrons Chronozone, representing the repopulation interval. The anoxia linked to the postulated ETOAE cannot be the responsible for the mass extinction, because it has been synchronously recorded in the oxygenated environments of many European and Northern African platforms. Deposition of laminated organic-rich black shale facies, above 5 wt.% TOC indicating anoxic environments, was mostly confined geographically to the Western Europe Euxinic Basin, and mainly deposited after the extinction event, during the interval of faunal recovery

Late Triassic and Early Jurassic palaeogeographic evolution and depositional cycles of the Western Tethys Iberian platform system (Eastern Spain)

Deposition of Upper Triassic and Lower Jurassic sediments on the Iberian platform system took place in a post-rift intraplate basin which formed part of the western Tethys shelf. Nevertheless, there is evidence for the tensional reactivation of a network of faults with associated magmatic activity. Early Jurassic palaeogeographic reconstructions, based on over 70 sections and 9 oil wells, reveal the presence of a series of highs and lows (depocentres). Two main highs, referred to as the El Maestrazgo High, in the east, and the La Mancha High, in the west, where condensed sections were deposited, were mainly controlled by syndepositional faults. The main depocentres were situated between these two highs areas, in a northwest trending belt in the central, northern and southern areas. Despite partial fault control, development of some Early Jurassic depocentres appears to be mainly controlled by thermal contraction of the lithosphere following Triassic main rifting pulse. The Upper Triassic–Lower Jurassic succession of the Iberian platform system was deposited during four transgressive and regressive cycles of 12 to 6 My duration. The lowermost cycle LJ-1 started in late Norian and lasted until the Sinemurian. The second cycle LJ-2 started in the Sinemurian and ended in the Pliensbachian (Davoei Zone), and can be subdivided into two minor cycles LJ2-1 and LJ2-2. The cycle LJ-3 started with an extensive upper Pliensbachian (Davoei Zone) transgression, whereas the top of its regressive cycle is dated to the Toarcian (Variablilis Zone). Within cycle LJ-3, three cycles can be distinguished. Maximum deepening was reached during the Bifrons Zone and active volcanism took place along the Teruel and Caudiel faults. The transgressive phase of the cycle LJ-4 started in the Thouarsense Zone and extended up to the Insigne Zone; its regressive phase developed during the upper Toarcian (Pseudoradiosa and Aalensis Zones) and part of the Aalenian (Opalinum and Murchisonae Zones). This cycle can be subdivided in two minor cycles, with their transgressive peaks occurring during the Insigne Zone, and the Aalensis Zone respectively. Palaeogeographically this corresponds with the expansion of the marginal carbonate platforms over hemipelagic deposits. The top of the cycle corresponds to a major unconformity with regional emersion during the Aalenian Murchisonae Zone

Bivalvos del Pliensbachiense en la Sección de Almonacid de la Cuba (Cordillera Ibérica, España)

Se ha realizado el estudio taxonómico detallado de unos ciento noventa especímenes de bivalvos pliensbachienses, procedentes de la región de Almonacid de la Cuba (Zaragoza), que ha dado como resultado la caracterización y descripción de veinte especies pertenecientes a catorce géneros de las subclases Pteriomorphia (14%; Mytiloidea, Pinnoidea, Limoidea, Ostreoidea y Pectinoidea) y Heteroconchia (86%; Lucinoidea, Cardioidea y Pholadomyoidea). El análisis del estado de conservación de los Pteriomorphia permite suponer que al menos una de las capas microestructurales que formaron la concha es de composición calcítica mientras que en los Heteroconchia, que sólo se han registrado como moldes internos, la composición de la concha era de naturaleza aragonítica. El 61% de los ejemplares estudiados pertenece a la superfamilia Pholadomyoidea, que es además la que muestra mayor diversidad taxonómica. El modo de vida de los bivalvos registrados en las formaciones pliensbachienses indica que se produjo una disminución relativa de la energía del medio entre las formaciones Río Palomar y Almonacid de la Cuba que sin embargo presenta episodios de más alta energía en su parte superior. El registro de bivalvos de la Formación Cerro del Pez permite inferir que la energía del medio debió ser incluso más baja que la de la Formación Almonacid de la Cuba, mientras que el notable aumento de formas cementantes y epifaunales bisadas en la Formación Barahona, apunta a la existencia de un ambiente con una energía considerablemente mayor que la supuesta para las formaciones anteriores. [ABSTRACT] A collection of one hundred ninety specimens Pliensbachian Bivalves from the Almonacid de la Cuba region (Zaragoza) has been analysed. As a result, twenty species included in fourteen genera are described. These species are included into the Subclass Pteriomorphia (14%; Mytiloidea, Pinnoidea, Limoidea, Ostreoidea y Pectinoidea) and mostly in the Subclass Heteroconchia (86%; Lucinoidea, Cardioidea y Pholadomyoidea). Preservation in the Pteriomorphia suggests that, at least one of the wall layer was originally calcitic, whereas in the Heteroconchia (only recorded as internal moulds), the wall composition was entirely aragonitic. The 61% of the studied specimens are included in the Superfamily Pholadomyoidea, which is also the Superfamily with a higher taxonomic diversity. The lifestyle of these Pliensbachian bivalves suggests that the energy in the environment decreased between the Río Palomar and Almonacid de la Cuba Formations. Nevertheless, in the upper pat of the latter, a period of high energy is recognised. The bivalves from Cerro del Pez Formation suggest that the energy in this formation was even lower than in the Almonacid de la Cuba Formation. The increase in the byssate epifaunal and cemented bivalves in the Barahona Formation suggests the highest energy environment of the all studied formations

Mass extinction and recovery of the Early Toarcian (Early Jurassic) brachiopods linked to climate change in Northern and Central Spain

The Early Toarcian mass extinction event represented the most important Mesozoic and Cenozoic turnover of the population of brachiopods and severely affected other benthic fauna. Two main hypotheses have been proposed to explain the synchronous and global mass extinction: an oceanic anoxic event or awarming episode. To test both hypotheses, the dynamics of the brachiopod assemblages below and above the extinction boundary are analyzed and compared with the seawater paleotemperature variations, calculated from the δ18O data recorded in belemnite rostra. Five sections from Northern and Central Spain, well dated with ammonites, have been selected for this study. The sections show no indication of sedimentary breaks and contain abundant brachiopods, which have been grouped into four assemblages. The changes observed in the brachiopod assemblages show a close correlation with the changes in the seawater paleotemperatures. The oldest assemblage (assemblage 1) coincides with a cooling interval recorded to have taken place in the latest Pliensbachian. Paleobiogeographical reconstruction shows that this assemblage was distributed at paleolatitudes between 30 and 45°N, with a preference for relatively cool waters. With the rise of temperatures that took place during the earliest Toarcian Tenuicostatum Zone, assemblage 1 was substituted by assemblage 2, which composed of different species of the same genera but considerably restricted to the warmer waters of lower paleolatitudes, between 28 and 35°N. Coinciding with the rapid and pronounced increase in seawater temperature, recorded at the Tenuicostatum–Serpentinum zonal boundary, all of these brachiopod species disappeared in the studied localities, marking clearly the extinction boundary. Predominant southward currents through the Laurasian Seaway precluded the possible migration of the brachiopods to cooler northern waters. The brachiopods' disappearance is independent from the oxygenation degree of the sea bottom, and therefore the rapid warming seems to be the most plausible cause of the mass extinction. After the extinction event, the recovery of the brachiopodswas uneven. Subsequent to a brief pause, recoverywas rapid in Central Spain and in other southern areas of Western Tethys, whereas in northern Spain and in the whole of Europe north of the French Central Massif, brachiopods did not recover until the Mid to Late Toarcian times

Events around the Triassic–Jurassic boundary in northern and eastern Spain: A review

More than 20 successions containing the Triassic–Jurassic (T–J) boundary were studied in five of the major geological units of Spain. The data are from outcrop, cored boreholes, and interpreted well-logs. A consistent −3.4‰ δ13Corg isotope excursion, starting in the Rhaetian and continuing in the Hettangian, was recorded in Asturias. Climate changes in the T–J transition show a warming episode in the early Hettangian. Other climate changes are indicated by an increase in hygrophytic miospores above the T–J boundary; this reflects a more humid episode at the beginning of the Hettangian. The Messejana Dyke in southeastern Iberia is part of the Central Atlantic Magmatic Province (CAMP). CO2 outgassing related to extensive magmatic activity in the CAMP is thought to be one of the possible factors responsible for the end-Triassic mass extinction. No major sea-level changes or unconformities were recorded at the T–J boundary. Only in the Asturias area was there a well-defined shallow carbonate platform during the T–J transition. The other areas of eastern and northern Spain were occupied by coastal playas and sabkhas that developed in arid climatic conditions. The biotic crisis around the T–J boundary is reflected in the palynomorph record. In Asturias, seven species do not persist beyond the late Rhaetian, and only six appeared in the Triassic–Jurassic transition. However, 22 taxa appeared in the early Hettangian

Lower Toarcian ammonite and foraminifera assemblages in the San Miguel de Aguayo Section (Basque-Cantabrian Basin, Spain)

We present the biostratigraphical events, ammonites and foraminifera from the Pliensbachian (Spinatum Chronozone) to the Toarcian (Bifrons Chronozone) in San Miguel de Aguayo. We sampled the profile layer by layer for ammonites (400 specimens in 86 successive levels), and we extracted 19 samples for foraminifera (4858 picked specimens). In the Spinatum Chronozone, the Amaltheidae Family dominated, with little presence of the Arieticeratinae or Harpoceratinae. The Tenuicostatum Chronozone presents a good record of Dactylioceratinae, with successive species, from Dactylioceras (Eodactylites) simplex to Dactylioceras (Orthodactylites) semicelatum. The Serpentinum Chronozone is characterised by Harpoceratinae (Eleganticeras, Cleviceras, Harpoceras), Hildoceratinae (Hildaites, Orthildaites) and by the persistence of Dactylioceras (Orthodactylites). The Bifrons Chronozone presents a good succession of Hildoceras. The foraminifera are benthic and autochthonous, and the calcareous hyaline taxa of the Lagenina Suborder, Vaginulinidae Family, are dominant. The most diverse genera are Nodosaria and Lenticulina. The most abundant species is Lenticulina toarcense, which constitutes 55.37% of the total number of specimens. Also represented, albeit as a minority, are the Textulariina, Miliolina, Spirillinina and Robertinina Suborders. The ammonites are typical of the Submediterranean Province and common to the Subboreal Province; the species of the Mediterranean Province are scarce and their record is sporadic in the Pliensbachian–Toarcian transition. The foraminifera are typical of the Atlantic Boreal Domain; two main biotic events were recognised: step-wise extinction of species between the Hawskerense and Semicelatum subchronozones, with a maximum extinction rate in the Semicelatum Subchronozone, and faunal turnover principally in the Elegantulum Subchronozone (Serpentinum Chronozone)

El Toarciense Superior, Aaleniense y Bajociense en Camino (Santander). Precisiones bioestratigráficas.

La sucesión estratigráfica descrita e interpretada en el presente trabajo permite identificar la totalidad de las biozonas correspondientes al Toarciense superior, Aaleniense y Bajociense. Los efectos de condensación tafonómica o de condensación estratigráfica no son relevantes a escala zonal. Estos materiales se formaron en el ámbito de una plataforma carbonatada, marina-abierta, de tipo epicontinental, y comportamiento subsidente diferencial, que da lugar al predominio de facies más somera en las áreas meridionales. El tránsito Bajociense-Bathoniense corresponde a una fase generalizada de somerización en la cuenca, entre dos episodios transgresivos que sucesivamente se desarrollan durante el Bajociense superior y Bathoniense inferior. En etapas anteriores a éstas, durante el Toarciense superior, Aaleniense y Bajociense inferior, predominó la sedimentación de tipo pelágico, si bien en condiciones algo más restringidas. La persistencia de ambientes marinos abiertos durante estos intervalos temporales también ha podido ser inferida a partir de las sucesivas asociaciones registradas. Las faunas de ammonites muestran afinidades subboreales, aunque en repetidas ocasiones experimentaron influencias submesogeas