Antonio Goy

CALIBRATION OF THE PLIENSBACHIAN-TOARCIAN CALCAREOUS NANNOFOSSIL ZONE BOUNDARIES BASED ON AMMONITES (BASQUE-CANTABRIAN AREA, SPAIN)

Based on a continuous succession of ammonite and calcareous nannofossil assemblages, the main purpose of this paper is the correlation between ammonite and calcareous nannofossil zone boundaries in two expanded sections from the Basque-Cantabrian area. The ammonite assemblages show clear euroboreal features and allow the identification of Pliensbachian-Toarcian zones and subzones established for NW Europe. Due to the presence of Mediterranean taxa documented at different levels, they are also helpful to improve the biocorrelations between Boreal and Tethyan successions. The calcareous nannofossil assemblage changes provide a useful set of easily recognizable events that facilitate the recognition of all the Pliensbachian-Toarcian zones described for NW Europe and Mediterranean Province. Based on the FO Similiscutum cruciulus (Jamesoni Zone), FO of Lotharingius hauffii (Stokesi/Margaritatus Zone boundary), FO of Carinolithus superbus (Serpentinus Zone), FO of Discorhabdus striatus (Serpentinus/Bifrons Zone boundary) and FO of Retecapsa incompta (Insigne Zone), the NJ3/NJ4, NJ4/NJ5, NJ5/NJ6, NJ6/NJ7 and NJ7/NJ8 Zone boundaries have been recognized. Besides, the NJ4, the NJ5 and the NJ6 span almost the same ammonite-defined time interval in both NW Europe and Basque-Cantabrian area. With respect to the ammonite zone, the zone boundaries NJ3/NJ4 and the NJ6/NJ7 coincides with the NJT3/NJT4 and the NJT6/NJT7 proposed for Mediterranean Province. Instead, the zone boundaries NJ4/NJ5 and the NJ5/NJ6 not coincides with the NJT4/NJT5 and the NJT5/NJT6 proposed for Mediterranean Province. Furthermore, in NW Europe and Mediterranean Province the FO of Retecapsa incompta is placed in the Levesquei Zone and Meneghinii Zone, whilst in the Basque Cantabrian area it lies in the Insigne Zone.

The Lias/Dogger boundary in Iberia; Betic and Iberian cordilleras and Lusitanian Basin

In this paper we present a synthesis on the Toarcian/Aalenian (Lias/Dogger) boundary in the Iberian Peninsula. We have selected in each domain the most representative areas and sections in which this boundary is represented: Fuentelsaz and Moyuela sections in the Iberian Cordillera, Sierra de Ricote and Cerro Mendez in the Betic Cordillera, and Sao Giao in the Lusitanian Basin. In these areas the succession across the Toarcian/Aalenian boundary is represented mainly by pelagic grey marl-marly limestone rhythmites, which contain abundant and characteristic ammonites. The standard ammonite zones of Aalensis (Mactra, Aalensis and Buckmani Subzones) for the uppermost Upper Toarcian, and Opalinum (Opalinum and Comptum Subzones) in the Lower Aalenian are recognised and characterised. Although the ammonite assemblages of the Betic Cordillera are typical of the Mediterranean province, and the Iberian and Lusitanian basins constitute a Sub-Mediterranean one, the ammonite assemblages are similar in the three basins, with the only significant difference being that phylloceratids and lytoceratids are abundant in the Betic domain and are scarcer in the other basins.

A complementary section for the proposed Toarcian (Lower Jurassic) global stratotype: The Almonacid de la Cuba section (Spain)

We present the biostratigraphy (ammonites, brachiopods, foraminifers, and ostracodes), lithostratigraphy, sedimentology, sequence stratigraphy, magnetostratigraphy, and isotope stratigraphy of the Almonacid de la Cuba section located in the Iberian Range, central-eastern Spain. This section, which contains a continuous and expanded record of the Pliensbachian-Toarcian boundary (Early Jurassic), has been proposed as a complementary section for the Toarcian GSSP. An excellent ammonite-based biozonation has been obtained. Four ammonite assemblages characterized by the presence of Pleuroceras, Canavaria, Dactylioceras (Eodactylites), and Dactylioceras (Orthodactylites) have been distinguished. The base of the Toarcian is located at level CU35.2, based on the first occurrence of Dactylioceras. The occurrence of taxa from the NW European and the Mediterranean provinces is useful to improve the correlation between both provinces. Foraminiferal and ostracode assemblages are rich and diversified and no significant biostratigraphic events take place at the Pliensbachian-Toarcian boundary. The magnetostratigraphic data presented here are the most complete record of reversals of the earth magnetic field for the Pliensbachian-Toarcian boundary. A good record of the onset of the positive δ13C excursion reported in the Lower Toarcian of many European sections has been obtained. Average paleotemperatures measured at the latest Pliensbachian Spinatum Biochron of about 12.5°C, recorded a marked increase of the seawater temperature which started during the Toarcian, reaching average temperatures of 16.7°C at the Tenuicostatum Biochron. The obtained 87Sr/86Sr values fully agree with the LOWESS calibration curve.

The associations of Brachiopodsfrom the Toarcian-Aalenian transition in the Fuentelsaz section (Iberian Range, Spain)

Abstract The stratigraphic continuity and good preservation of the Brachiopods in the section of Fuentelsaz (Province of Guadalajara, Spain), permit to carry out a detailed study of these fossils in the Toarcian-Aalenian transition. This study puts on evidence an episode of species renewal in the Aalensis Subzone, and another episode of morphological modification at the Base of the Buckmani Subzone, the Latter being more important from the stratigraphical point of view. In the transition from the Buckmani Subzone to the Opalinum Subzone no significative change is observed in the associations.

Bivalves from the Triassic−Jurassic transition in northern Spain (Asturias and western Basque−Cantabrian Basin)

Abstract. Bivalve mollusks from the Triassic-Jurassic transition collected in eight localities in Asturias and the western Basque-Cantabrian Basin (Palencia province) are systematically revised. Preservation is poor at all localities. The dominant Rhaetian bivalves are Isocyprina concentrica (Moore) and Bakevellia (Bakevelloides) praecursor (Quenstedt). These species, together with Isocyprina cf. ewaldi (Bornemann), Pteromya cf. crowcombeia (Moore), Pseudoplacunopsis alpina (Winkler), and Modiolus? sp. (cf. minimus J. Sowerby), with a specimen of Arcestidae (?), belong to an assemblage similar to that found in the Westbury and Lilstock formations (Penarth Group) in the late Rhaetian of southern England. The most abundant Hettangian species is Isocyprina (Eotrapezium) germari (Dunker). Others are referred to Cuneigervillia rhombica (Cossmann), Sphaeriola? sp., Eomiodon? sp. and Pteromya cf. tatei (Richardson and Tutcher). All Hettangian shell beds examined are monotypic or have very low diversity, a biological indication that they may belong to a restricted marine environment, with high environmental stress levels. Even the more diverse assemblage (Pteromya-Cuneigervillia-Eomiodon) was probably also salinity controlled. The fauna analyzed here clearly belongs to the same facies and environment as those described from Aquitaine (France) and the Pyrenees and is different from coeval bivalve assemblages from other European Hettangian localities. The Triassic-Jurassic boundary cannot be precisely located at the studied sections on the basis of the bivalve faunas alone, but these indicate that the transition beds in Asturias were deposited in a marginal marine environment and the benthic fauna was dominated by shallow burrowing, suspensivorous bivalves.

Nautiloids from the Muschelkalk facies of the Southiberian Triassic (Betic Cordillera, southern Spain)

The study of Middle Triassic (Ladinian) nautiloids from three successive ammonoid zones, and two sub-zones, of the Southiberian Triassic Muschelkalk facies (Betic Cordillera, southern Spain) has allowed the identification of the following species: Mojsvaroceras haasi Parnes, 1986, M. kummeli Parnes, 1986, Germanonautilus bidorsatus (von Schlotheim, 1820), G. tridorsatus (Böttcher, 1938), Grypoceras? quadrangulum (Beyrich, 1866a), Indonautilus awadi Kummel, 1960, I. privatus (Mojsisovics, 1882) and Picardiceras picardi Parnes, 1986. The possibly endemic Indonautilus innocens sp. nov. is described herein. Although some of these species have already been reported from the Betic Cordillera, most are described in detail and illustrated for the first time and their stratigraphical distributions determined accurately for this region. Of the nine nautiloid species described herein, five are known from the Germanic and Tethyan provinces and four are restricted to the Sephardic Province. The genus Picardiceras is typical of the Sephardic Province. It appears that during the Ladinian the Betic Cordillera was a palaeogeographical region for faunal exchange between Central Europe, North Africa and the Middle East. http://zoobank.org/urn:lsid:zoobank.org:pub:98032616-2778-439B-B6D4-D32BFF7CCB83

The hydrocarbon source rocks of the Pliensbachian (Early Jurassic) in the Asturian Basin (Northern Spain): Their relationship with the palaeoclimatic oscillations and gamma-ray response.

Deposition of black shale facies, one of the main contributors for hydrocarbon production, is commonly assumed to be linked to Oceanic Anoxic Events (OAEs), which are supposed to be generated during warm palaeoclimats. This assumption could bias the exploration for hydrocarbon source rocks preferentially towards sediments deposited under warm palaoenvironments, as a preferential guide for hydrocarbon exploration. As a consequence, the establishment of the links between palaeotemperature and the formation of organic-rich deposits is of primary importance to find arguments on this subject. For this purpose, the Upper Sinemurian, Pliensbachian and Lower Toarcian (Lower Jurassic) deposits of the Asturian Basin in Northern Spain, including more than 100 m thick succession containing organic-rich and black shale deposits, has been studied. Correlation between palaeoclimatic data, previously obtained from oxygen isotopes, and the TOC content reveals that black shales and organic-rich sediments were deposited not only during warming intervals but also during a prominent cooling event that occurred at the Late Pliensbachian. This cooling interval has been pointed out as one of the main candidates to have developed ice caps in the poles during the Jurassic. On the contrary, no black shales were generated during the postulated Early Toarcian OAE, which coincides with a superwarming interval. Additionally, the study of the facies cycles and the measurement of gamma-ray in outcrops and its correlation with TOC content provides data on the use of natural radioactivity and sea level changes as a proxy for preliminary organic matter richness evaluation.

Nautiloids From the Toarcian of the Iberian Peninsula, Spain and Portugal

A study of the Lower Jurassic nautiloids held in the Universidad Complutense de Madrid and the Instituto Geologico y Minero, Spain, and in the Universidade de Coimbra and the Museu Geologico e Mineiro, Portugal, has revealed the presence of numerous and diverse representatives of the genera Cenoceras, Ligeiceras, Ophionautilus, and Digonioceras in the Toarcian of the Iberian Peninsula. Specifically, the taxa Cenoceras robustum, C. fontannesi, C. semistriatum, C. astacoides, C. jourdani, C. toarcense, C. ciryi, C.? beirense, Ligeiceras fourneti, L. inornatum, L. anomphalum, L. jurense, L.? globulum, Ophionautilus sp., Digonioceras sp. 1, and D. sp. 2 have been identified and described, and their stratigraphic distributions have been determined for this region of southwestern Europe.

CONSERVATION MANAGEMENT OF THE AALENIAN STAGE GSSP IN FUENTELSAZ (CASTILLA-LA MANCHA, SPAIN)

The Global Boundary Stratotype Section and Point of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic) in Fuentelsaz Section is the first GSSP defined in Spain. Among the requirements of the ICS for the choice of the best boundary level are accessibility to the type-section and free access for research, and guarantees from the respective authority concerning to the free access and the permanent protection of the site. In our point of view, the most suitable protection figure to safeguard the fulfilment of the ICS’s requirements according to the Spanish Conservation Policy and Legislation is the Natural Monument. This paper deals with the conservation management and classification of the Fuentelsaz area as a Natural Monument, being the Comunidad de Castilla-La Mancha Authorities the ones that have to take the necessary steps to protect the site.