Organic-Rich facies in the Sinemurian and Pliensbachian of the Lusitanian Basin, Portugal: Total organic carbon distribution and relation to transgressive-regressive facies cycles

The upper Sinemurian to Pliensbachian series of the Lusitanian Basin (Portugal) correspond to marly limestone sediments rich in benthic and nektonic macrofauna. This sedimentary record includes several intervals of organicrich facies, which are particularly well developed in the western sectors of the basin. They correspond to grey and dark marls locally showing strong lamination (black shale type) and are recognized as one of the most important potential oil source rocks. This study shows the vertical and lateral distribution of these organic-rich intervals, supported by over 550 total organic carbon (TOC) determinations. The results presented reveal two important intervals, with several black shale occurrences, in the Oxynotum(?)–Raricostatum (Polvoeira Member of Água de Madeiros Formation) and at the top of the Ibex-upper part of Margaritatus zones (top of the Vale das Fontes Formation), showing in the distal (western) sectors up to 22% and 15% TOC, respectively. TOC values decrease progressively towards the proximal sectors, the youngest organic-rich interval being the most expressive at the basin scale. This lateral TOC distribution, the facies stacking patterns and the decrease observed in benthic macrofauna confirm that these intervals are related to 2nd-order transgressive phases. 2nd-order regressive phases, developed during the uppermost Raricostatum and Spinatum zones respectively, show lower TOC values. TOC distribution combined with other stratigraphic and sedimentological parameters enabled seven facies maps to be created for the time interval studied. At the regional scale, this study shows for the first time the good similarity between the upper Sinemurian-Pliensbachian sedimentary successions of the Lusitanian and Basque- Cantabrian basins

A calcareous nannofossil and organic geochemical study of marine palaeoenvironmental changes across the Sinemurian/Pliensbachian (early Jurassic, ~191Ma) in Portugal

The Sinemurian/Pliensbachian boundary (~ 191 Ma) is acknowledged as one of the most important steps in the radiation of planktonic organisms, especially primary producers such as dinoflagellates and coccolithophores. To date, there is no detailed study documenting changes in planktonic assemblages related to palaeoceanographic changes across this boundary. The aim of this study is to characterize the palaeoenvironmental changes occurring across the Sinemurian/Pliensbachian boundary at the São Pedro de Moel section (Lusitanian Basin, Portugal) using micropalaeontology and organic geochemistry approaches. Combined calcareous nannofossil assemblage and lipid biomarker data document for a decrease in primary productivity in relation to a major sea-level rise occurring above the boundary. The Lusitanian Basin was particularly restricted during the late Sinemurian with a relatively low sea level, a configuration that led to the recurrent development of black shales. After a sharp sea-level fall, the basin became progressively deeper and more open during the earliest Pliensbachian, subsequently to a major transgression. This sea-level increase seems to have been a global feature and could have been related to the opening of the Hispanic Corridor that connected the Tethys and palaeo-Pacific oceans. The palaeoceanographic and palaeoclimatic changes induced by this opening may have played a role in the diversification of coccolithophores with the first occurrence or colonization of Tethyan waters by placolith-type coccoliths

Organic-Rich facies in the Sinemurian and Pliensbachian of the Lusitanian Basin, Portugal : Total organic carbon distribution and relation to transgressive-regressive facies cycles

The upper Sinemurian to Pliensbachian series of the Lusitanian Basin (Portugal) correspond to marly limestone sediments rich in benthic and nektonic macrofauna. This sedimentary record includes several intervals of organicrich facies, which are particularly well developed in the western sectors of the basin. They correspond to grey and dark marls locally showing strong lamination (black shale type) and are recognized as one of the most important potential oil source rocks. This study shows the vertical and lateral distribution of these organic-rich intervals, supported by over 550 total organic carbon (TOC) determinations. The results presented reveal two important intervals, with several black shale occurrences, in the Oxynotum(?)-Raricostatum (Polvoeira Member of Água de Madeiros Formation) and at the top of the Ibex-upper part of Margaritatus zones (top of the Vale das Fontes Formation), showing in the distal (western) sectors up to 22% and 15% TOC, respectively. TOC values decrease progressively towards the proximal sectors, the youngest organic-rich interval being the most expressive at the basin scale. This lateral TOC distribution, the facies stacking patterns and the decrease observed in benthic macrofauna confirm that these intervals are related to 2nd-order transgressive phases. 2nd-order regressive phases, developed during the uppermost Raricostatum and Spinatum zones respectively, show lower TOC values. TOC distribution combined with other stratigraphic and sedimentological parameters enabled seven facies maps to be created for the time interval studied. At the regional scale, this study shows for the first time the good similarity between the upper Sinemurian-Pliensbachian sedimentary successions of the Lusitanian and Basque- Cantabrian basins

Bivalves from Água de Madeiros Formation (Upper Sinemurian) of the Lusitanian Basin (Portugal)

Apresenta-se a distribuição estratigráfica dos taxa de moluscos bivalves ao longo da Formação de Água de Madeiros (Sinemuriano superior–extrema base do Pliensbaquiano) na Bacia Lusitânica. Estudaram-se as secções de S. Pedro de Moel e Peniche, por serem as mais completas e representativas do ponto de vista do registo paleontológico e seu significado biostratigráfico. Esta análise estratigráfica de alta resolução baseia-se em 2691 espécimes recolhidos em 180 estratos, o que permitiu um acréscimo significativo (31%) de novos taxa reconhecidos na bacia neste intervalo. Evidencia-se uma variação vertical na composição taxonómica das associações faunísticas com o surgimento de espécies oportunistas interpretadas como facultativamente pseudoplânctónicas. Este registo é observado na transição entre as cronozonas Oxynotum e Raricostatum, interpretando-se como tendo sido favorecido por mudanças na deposição, de que resultaram condições pelo menos disóxicas. O surgimento de formas de Pseudomytiloides e de Oxytoma durante o Sinemuriano terminal da bacia aponta para que estas ocorrências sejam as primeiras no contexto do Jurássico NO europeu.The stratigraphic distribution of bivalve molluscs throughout the Água de Madeiros Formation (Upper Sinemurian– lowermost Pliensbachian) at the Lusitanian Basin is present here. The work was carried out on the sections of S. Pedro de Moel and Peniche. This high-resolution stratigraphic analysis is based on 180 sampled beds and 2691 bivalve specimens. This new collection allows a significant improvement (31%) of the number of taxa already known for the basin, during this interval. The occurrence of a faunal turnover that allowed the spanning of opportunistic species, here interpreted as representative of a pseudoplanktonic habitat, is also shown. This record is noted around the Oxynotum–Raricostatum chronozone transition and inferred to have resulted from depositional changes linked with dysoxic conditions near the water-substrate interface. The appearance of Pseudomytilodes and Oxytoma forms in the Lusitanian Basin seems to be the earliest in the NO European Lower Jurassic provinceDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEFondo Europeo de Desarrollo Regional (FEDER)Ministerio de Ciencia e Innovación (MICINN)European Community Research Infrastructure Action - FP6pu

The brachiopod record in the Lower Toarcian (Jurassic) of the Rabaçal-Condeixa region (Portugal): stratigraphic distribution and palaeobiogeography

Se estudian los braquiópodos del Toarciense Inferior de la región de Rabaçal-Condeixa (Cuenca Lusitánica). En la Zona Polymorphum se ha registrado un conjunto muy diverso que incluye taxones de las provincias Noroeste Europea y Mediterránea. También se han encontrado en esta zona las especies típicas de la llamada “Fauna de Koninckella”, supuestamente asociada a ambientes profundos o pobres en oxígeno. Los Braquiópodos desaparecen en los primeros niveles de la Zona Levisoni, cuando comienza la sedimentación del miembro Calizas nodulosas en plaquetas de la Formación S. Gião. La recuperación coincide con el registro de Soaresirhynchia bouchardi, seguido de formas características de la “Fauna Española” - especies de Telothyris, Homoeorhynchia y Choffatirhynchia - que se encuentran también en los primeros niveles de la Zona Bifrons.São estudados os braquiópodes do Toarciano inferior da região de Rabaçal-Condeixa (Bacia Lusitânica). A Zona Polymorphum mostra uma associação muito diversa que inclui taxas das províncias do Noroeste da Europa e Mediterrânica. Registam-se igualmente nesta zona as espécies típicas da chamada “Fauna de Koninckella”, supostamente associada a ambientes sedimentares profundos ou pobres em oxigénio. Os Braquiópodes desaparecem nos primeiros níveis da Zona Levisoni, associados ao membro Calcários nodulosos em plaquetas da Formação de S. Gião. A recuperação coincide com o registo de Soaresirhynchia bouchardi, seguido de formas características da ”Fauna Espanhola” – espécies de Telothyris, Homoeorhynchia e Choffatirhynchia - que se encontram também nos primeiros níveis da Zona BifronsThe brachiopods from the Lower Toarcian of the Rabaçal- Condeixa (Lusitanian Basin) area are studied. A very diverse assemblage is recorded in the Polymorphum Zone, including both NW European and Mediterranean taxa. The typical species of the socalled “Koninckella Fauna”, that is supposedly associated to deep or oxigen-poor environments are also recorded throughout this Zone. Brachiopods disappear in the first levels of the Levisoni Zone and beginning of the Thin nodular limestones member of the S. Gião Formation. Brachiopods recovery is marked by the appearance of Soaresirhynchia bouchardi, followed by the typical representatives of the “Spanish Fauna” - species of Telothyris, Homoeorhynchia and Choffatirhynchia - that are distributed also in the first levels of the Bifrons ZoneDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasFALSEFundación Española para la Ciencia y la TecnologíaEspaña. Ministerio de Innovación y Cienciapu

Upper Sinemurian (Oxynotum–Raricostatum chronozones) from the S. Pedro de Moel area (Lusitanian Basin, Portugal)

El estudio detallado de la sucesión de ammonoideos (más de 800 ejemplares) procedentes de dos secciones expandidas (Polvoeira and Água de Madeiros), localizadas en la región de S. Pedro de Moel (Cuenca Lusitánica) ha permitido caracterizar la Cronozona Oxynotum (Subcronozona Oxynotum) por la existencia de Oxynoticeras, Bifericeras, Cheltonia y Plesechioceras y la Cronozona Raricostatum (subcronozonas Raricostatum, Macdonnelli y Aplanatum) por taxones típicos de las zonas estándar de Echioceras, Leptechioceras y Paltechioceras. El límite Sinemuriense-Pliensbachiense se ha marcado formalmente, por primera vez en la Cuenca Lusitánica con el primer registro de Gemmellaroceras aff. G. aenigmaticum, asociado a Apoderoceras subtriangulare.O estudo detalhado da sucessão de amonóides (mais de 800 exemplares) procedentes de duas secções expandidas(Polvoeira e Água de Madeiros), localizadas na região de S. Pedro de Moel (Bacia Lusitânica) permitiram caracterizar a Cronozona Oxynotum (Subcronozona Oxynotum) através da ocorrência de Oxynoticeras, Bifericeras, Cheltonia e Plesechioceras e a Cronozona Raricostatum (subcronozonas Raricostatum, Macdonnelli e Aplanatum) onde se reconheceram taxa típicos do quadro biostratigráfico de referência com Echioceras, Leptechioceras e Paltechioceras. O limite Sinemuriano- Pliensbaquiano é definido formalmente pela primeira vez com base na presença de Gemmellaroceras, afins a G. aff. aenigmaticum, associado a Apoderoceras subtriangulareThe detailed study of the ammonite succession (more than 800 specimens) observed in two expanded sections (Polvoeira and Água de Madeiros), located in the S. Pedro de Moel area (Lusitanian Basin), has allowed characterizing the Oxynotum and Raricostatum chronozones of the Upper Sinemurian. The Oxynotum Chronozone (Oxynotum Subchronozone) is recognized by the occurrence of the genera Oxynoticeras, Bifericeras, Cheltonia and Plesechioceras and the Raricostatum Chronozone (Raricostatum, Macdonnelli y Aplanatum subchronozones) by the record of several typical taxa of the standard zonation, pertaining to the genera Echioceras, Leptechioceras y Paltechioceras gr. tardecrescens. Based on the occurrence of Gemmellaroceras (G. aff. aenigmaticum) and the first record of Apoderoceras subtriangulare, the Sinemurian-Pliensbachian boundary is formally defined for the first time in the Lusitanian BasinDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasFALSEPortugal.Fundación para la Ciencia y la TecnologíaMinisterio de Innovación y Cienciapu