José M. Tavera

Lower Aptian ammonite and carbon isotope stratigraphy in the eastern Prebetic Domain (Betic Cordillera, southeastern Spain)

Major global palaeobiologic and palaeoenvironmental changes occurred during the Early Aptian. Precise dating and timing of the different events is crucial to determine possible cause-effect relationships between them. In this regard, the combination of biostratigraphic and chemostratigraphic data can provide a very useful tool for time control. So far attempts to correlate the Lower Aptian carbon isotope record and the ammonite zonation yielded contradictory conclusions. In this paper, we present the results of an integrated analysis of the ammonite stratigraphic distribution and highresolution carbon isotope profiles from Lower Aptian sections of the eastern Prebetic Domain (Betic Cordillera, southeastern Spain). We recognized, in ascending order, the Deshayesites oglanlensis, Deshayesites forbesi, Deshayesites deshayesi, and Dufrenoyia furcata Zones. This succession is the same as that recently identified in the eastern Iberian Chain, and it closely correlates with both standard Mediterranean and Boreal zonations. The carbon isotope record displays the trends globally recognized for the Early Aptian, with two long positive shifts separated by a pronounced negative excursion. Calibration of this isotopic record with the ammonite zonation shows that the age of OAE 1a, which corresponds to the negative excursion and subsequent positive shift, is constrained to the middle/upper part of the Deshayesites forbesi Zone.

Integrated biostratigraphy ofthe Durangites and Jacobi Zones (J/K boundary) at the Puerto Escaño section in Southern Spain (Province of Cordoba)

Abstract In the present paper we discuss the possibilities for the correlation of ammonites, calpionellids and calcareousnannofossils as recorded in the Puerto Escano section in Southern Spain (province of Cordoba), where a very detailed sampling was carried out. The section has proved to be a very significant one due both to the favorable outcrop and bedding preservation, and to the abundance of well-preserved fossil remains. We consider the selected section at Puerto Escano to be one of the most advantageous sites for the analysis of the stratigraphic distribution of significant macro and microfossils and thus for the study of the traditional Jurassic-Cretaceous boundary in ammonitico-rosso facies of the Mediterranean area.

The significance of Mediterranean ammonites with regard to the traditional Jurassic-Cretaceous boundary

Abstract We discuss the significance of Mediterranean faunas in the study of the traditional Jurassic-Cretaceous boundary based on ammonites. Reviewing the record of ammonites and calpionellids from southern Spain and also discussing data from SE France, Bulgaria, Czechoslovakia, Cuba, Mexico and Argentina, which permit correlation with the Spanish faunas, we conclude that: a) Berriasella jacobi Mazenot is a good index fossil for the base of the Berriasian (=base of the Cretaceous System), b) the jacobi ammonite association clearly differentiates the latest Tithonian (Durangites Zone), c) the genus Kossmatia occurs in shelf deposits and, when present, is very rare in the European Tethys, d) the Mexican Gulf was not the centre of dispersal for Durangites or Kossmatia .

Biostratigraphic analysis of the pelagic Barremian/Aptian in the Betic Cordillera (southern Spain): preliminary data

Abstract The Lower Cretaceous rhythmic sequences (marls and marly limestones) of the pelagic domain in the Betic Cordillera (Subbetic Zone) provide optimal conditions for integrated biostratigraphic scales based on different fossil groups. In this paper we present a preliminary study of the stratigraphic distribution of different species of ammonites, planktonic foraminifera, calcareous nannofossils and radiolaria recorded principally in one Barremian-Aptian section in Jaen (Andalusia, southern Spain). For the ammonites, which are present only in the Barrentian and probably in the lowermost Aptian, it appears reasonable to use the zonation proposed by Busnardo (1984) for SE France. Planktonic foraminifera can be differentiated in seven zones (Hedbergella sigali, Globigerinelloides blowi, Hedbergella trocoidea, Leupoldina cabri, Globigerinelloides algerianus, Planomalina cheniourensis and Ticinella bejaouaensis) for the Barremian-Aptian interval. Four interval zones (Lithraphidites bollii, Micrantholithus hoschulzii, Hayesites irregularis and Rhagodiscus angustus) can be distinguished according to the vertical distribution of the calcareous nannofossil species. Finally, two radiolarian assemblages can be identified, a lower one for the Barremian-Lower Aptian and an upper one for the Upper Aptian. Correlations between the scales used in this paper are established.

Le Valanginien du bassin de Safi (Maroc atlantique) et sa faune d'ammonites. Implications paléobiogéographiques

Abstract The study of ammonite assemblages collected from the Calcaire inferieur and the Argiles brunes in the region of Safi (Morocco) has allowed us to pinpoint the age of these formations and to attribute them, respectively, to the Boissieri Zone ower part of the Campylotoxus Zone and to the upper part of the Campylotoxus Zone pper Valanginian. These units are also reinterpreted in terms of sequence stratigraphy. In addition, the analysis of the faunal spectrum shows that, although differing in some respects, these ammonite associations are similar to those of other peri-Tethyan platforms, while differing considerably from the basin assemblages.