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Upper Toarcian ostracod assemblages from Boca da Mata, Alvaiázere, Central Portugal, are described to complement earlier work on the ostracods of the Toarcian GSSP at Peniche, western Portugal. A total of 44 species are recorded and the following new taxa described: Cytheropterina ainsworthi sp. nov., Eucytherura alvaiazerensis sp. nov., Otocythere iberobritannica sp. nov., Ophektycythere gen. nov. with O. herrrigi sp. nov., O. mataensis sp. nov. and O.? sicoensis sp. nov. The assemblages reflect oxygenated fully marine, sublittoral shallow water conditions in a proximal margin of the Lusitanian Basin. The species spectrum has most in common with material described from Western Europe especially the Fastnet Basin, offshore Ireland. Lowermost Aalenian assemblages contain some Toarcian species but also new taxa not studied in detail. [ABSTRACT FROM AUTHOR]

This research is focused on the ammonoids of Oxynotum Zone and Raricostatum Zone (Densinodulum Subzone) from Asturian (Spain) and Lusitanian (Portugal) basins. They come from expanded sections from where 216 specimens have been collected. These have been classified in eight genera and 15 species that belong to families Echioceratidae, Oxynoticeratidae and Eoderoceratidae. Most of the ammonoids are typical of the Northwest European Province. Echioceratidae is the most frequent in the Asturian Basin, whereas Oxynoticeratidae is the predominant in the Lusitanian Basin. Eoderoceratidae specimens are scarcer, and they are registered only between the middle part of Oxynotum Subzone and the lower part of Densinodulum Subzone. A new species is proposed for the upper part of Oxynotum Subzone of the Lusitanian Basin, Plesechioceras rochai sp. nov., which is relatively frequent. As well, also in Portugal, Cheltonia sp. is registered in Densinodulum Subzone, which is a form different from Cheltonia accipitris. This provides new evidence to support the hypothesis of the relation micro-macroconch between the genera Oxynoticeras (M) and Cheltonia (m). Remarkable differences in the studied area are the presence of Paroxynoticeras salisburgense and Plesechioceras cf. delicatum in the Asturias Basin, and Crucilobiceras densinodulum, associated to Oxynoticeras lymense, in the Lusitanian Basin. [ABSTRACT FROM AUTHOR]

New stable carbon isotope and biomarker data for oils and source rock extracts from the Lusitanian Basin, Portugal, were studied in order to investigate the petroleum systems which are present there. The new analytical data was combined with data presented in previous publications, and oil‐oil and oil‐ source rock correlations were carried out. Three genetic groups of oils (Groups 1, 2 and 3), belonging to three different petroleum systems, were identified: Group 1 oils occur in the northern sector of the Lusitanian Basin and were generated by the Coimbra Formation (Sinemurian) source rock. Reservoir rocks for oils in this group are the Coimbra, Água de Madeiros (upper Sinemurian – lower Pliensbachian), Boa Viagem (Kimmeridgian –Tithonian) and Figueira da Foz (upper Aptian – Cenomanian) Formations. Other potential source rocks in the northern sector of the basin, such as the Polvoeira Member of the Água de Madeiros Formation and the Marly Limestones with Organic Facies (MLOF) Member of the Vale das Fontes Formation (Pliensbachian), had biomarker characteristics which differed from those of the Group 1 oils and did not therefore generate them. Group 2 oils occur in the central and southern sectors of the basin. The source rock is the Cabaços Formation (middle Oxfordian), and reservoir rocks are the Montejunto (middle‐upper Oxfordian) and Abadia (Kimmeridgian) Formations. Group 3 is represented by an oil sample from the central sector of the Lusitanian Basin. Both the source rock and the reservoir rock for the oil are the Montejunto Formation. Geochemical data combined with the regional tectono‐stratigraphic history suggest that the generation‐migration‐accumulation of most of the oil (critical moment) in the Coimbra – Coimbra ‐ Água de Madeiros ‐ Boa Viagem ‐ Figueira da Foz (!) petroleum system occurred in the early Campanian. For the Cabaços – Montejunto ‐ Abadia (!) and Montejunto – Montejunto (!) petroleum systems, the critical moment occurred in the late Cenomanian. [ABSTRACT FROM AUTHOR]

Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Knowledge on the evolution of choanoflagellates is key for the understanding of the ancestry of animals, and although molecular clock evidence suggests the appearance of choanoflagellates by late Neoproterozoic, no specimens of choanoflagellates are known to occur in the fossil record. Here the first putative occurrence of choanoflagellates in sediments from the Cretaceous (Cenomanian–Turonian) is described by means of several cutting-edge petrographic techniques, and a discussion of its paleoenvironmental significance is performed. Furthermore, their placement in the organic matter classification systems is argued, with a placement in the Zoomorph Subgroup (Palynomorph Group) of the dispersed organic matter classification system being proposed. Regarding the ICCP System 1994, incorporation of choanoflagellates is, at a first glance, straightforward within the liptinite group, but the definition of a new maceral may be necessary to accommodate the genetic origin of these organisms. While modern choanoflagellates may bring light to the cellular foundations of animal origins, this discovery may provide an older term of comparison to their extant specimens and provide guidelines for possible identification of these organic components in other locations and ages throughout the geological record. [ABSTRACT FROM AUTHOR]

High‐resolution analysis of the late Pliensbachian – early Toarcian belemnite assemblages from the Peniche section (Lusitanian Basin) has enabled, for the first time, recognition of eight taxa of the suborder Belemnitina, previously reported from contemporaneous north‐west Tethyan and Arctic sections. The presence of Bairstowius amaliae sp. nov. in the late Pliensbachian (emaciatum Zone) represents a novelty given that hitherto the genus Bairstowius was known only from late Sinemurian and early Pliensbachian deposits. Additionally, the replacement of Bairstowius amaliae by Catateuthis longiforma, during the latest Pliensbachian, suggests an evolutionary relationship between the two taxa. This relationship suggests a new scenario for the subsequent development of endemic Toarcian Boreal–Arctic faunas, characterized by the occurrence of Catateuthis. Comparison of the Peniche belemnite fauna with coeval faunas from the Mediterranean/Submediterranean and Euro‐Boreal domains indicates taxonomic uniformity during the late Pliensbachian and early Toarcian (emaciatum and polymorphum Zones), in the north‐west Tethys. Despite the lack of a marked taxonomic turnover, the Pliensbachian–Toarcian boundary corresponds to a slight decrease in diversity observed not only in the Lusitanian Basin but also in coeval north‐western European basins. Ordination and cluster analyses indicate that the largest changes in belemnite diversity and palaeogeographical distribution occurred rather during the Toarcian Oceanic Anoxic Event (base of the levisoni Zone). This event is marked by the extinction of taxa, affecting more severely the Mediterranean/Submediterranean domain and resulting in a more pronounced provincial differentiation among north‐western European and Arctic belemnite faunas. [ABSTRACT FROM AUTHOR]

The stratigraphical occurrence of ostracod assemblages of the uppermost Pliensbachian (emaciatum Biozone) and Lower-Middle Toarcian (polymorphum, levisoni and bifrons biozones) at Peniche, western Portugal, is reported, an interval that encompasses the Toarcian Global Boundary Stratotype Section and Point (GSSP) and the Toarcian Oceanic Anoxic Event as represented by a Carbon Isotope Excursion (CIE). The broad pattern of ostracod faunal turnover and replacement in the Peniche GSSP section before, during and after the CIE, including "survivor" and "Lazarus" species, and the stepwise extinction of metacopine ostracods is similar to that described from elsewhere in Western Europe. Assemblage composition is closest to material described from the Fastnet Basin, offshore SW Ireland, and the Mochras Farm Borehole, Wales, Great Britain. The d13C record at Peniche and Mochras Farm facilitates a very refined comparison of ranges of species in common between the two sites. The species Bairdia paramolesta sp. nov. and Kinkelinella ventrocarinata sp. nov. are described. [ABSTRACT FROM AUTHOR]

Reduction of body size is a common response of organisms to environmental stress. Studying the early Toarcian succession in the Lusitanian Basin of Portugal, we tested whether the shell size of benthic marine communities of bivalves and brachiopods changed at and before the global, warming–related Toarcian oceanic anoxic event (T-OAE). Statistical analyses of shell size over time show that the mean shell size of communities decreased significantly before the T-OAE. This trend is distinct in brachiopods and is caused by larger-sized species becoming less abundant over time, whereas it is not significant in bivalves, suggesting a decoupled response to environmental stress. Reductions in shell size precede the decline in standardized sample-level species richness associated with the early Toarcian extinction event. Such decreases in the shell size of marine invertebrates, well before the onset of biodiversity change, suggest that reductions in body size more generally may be a precursor of a subsequent loss of species and turnover at the community level caused by climate change. Sedimentological evidence is against hypoxia as a driver of extinction and the preceding size decrease in the brachiopod fauna in the studied succession, although low oxygen levels are widely held responsible for elevated early Toarcian extinction rates globally. Reduction of mean shell size in brachiopods but stasis in bivalves is difficult to explain with ocean acidification, because experimental work shows that brachiopods can be resilient to lowered pH, albeit long-term metabolic costs and potential evolutionary adaptations are unknown. Rising early Toarcian temperatures in the Lusitanian Basin seem to be a plausible factor in both diversity decline associated with the T-OAE and the preceding reductions in mean shell size, because thermal tolerances in modern bivalves are among the highest within marine invertebrates. [ABSTRACT FROM AUTHOR]

Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Although molecular clock evidence suggests their appearance by late Neoproterozoic, only recently the first identification of fossil choanoflagellates in sediments from the Cretaceous was made (Fonseca et al., 2023). Here, attenuated total reflection (ATR) micro-Fourier-transform infrared (micro-FTIR) spectroscopy was used to achieve the first macromolecular characterization of single-specimen fossil choanoflagellates, and to assess differences and similarities with dinoflagellate cysts from the same sample. ATR micro-FTIR spectra reveal consistent molecular differences between fossil choanoflagellates and dinoflagellate cysts. Both microfossils are composed of a predominantly hydrogen-cross-linked, aliphatic biomacromolecule, with notable contributions of (probably polycyclic) aromatic rings, aromatic ethers, and phenols. However, choanoflagellates were systematically more aliphatic in nature than dinoflagellate cysts. The generally aliphatic-aromatic compounds in fossil choanoflagellates differ from actin found in modern choanoflagellates (Karpov and Leadbeater, 1998) and a cellulose-like carbohydrate in modern dinoflagellates (Versteegh et al., 2012) and were likely a result of (possibly early diagenetic) molecular alteration due to oxidative polymerization, which is a common taphonomical phenomenon in organic fossils (Gupta and Briggs, 2011). Despite taphonomical effects, a parallel molecular analysis of different fossil organisms from the same sample can reveal chemosystematic signatures and, in this case, highlights a different pre-diagenetic macromolecule present in the analyzed fossil choanoflagellates compared to other microeukaryotes. These results provide a first basis to further decrypt the chemospecific signatures of fossil choanoflagellates using complementary analytical methods, as well as to explore the fossilization and preservation behavior of these primitive metazoans. This is necessary to be able to construct chemotaxonomical arguments which could support established morphological affinities of modem and fossil organisms. [ABSTRACT FROM AUTHOR]

Lower Jurassic sedimentary successions in many central and northern Atlantic basins include relatively thick organic-rich intervals. Despite intense research, it is still unclear which mechanisms led to the deposition of these sediments during the Early Jurassic. In this talk, we will (1) present a detailed temporal and geographical framework of Sinemurian and Toarcian organic matter preservation intervals (OMPIs; subdivided into local, regional, and superregional) and (2) broadly constrain the relationship of OMPIs with the Early Jurassic δ13C record. For this, we combine an in-depth analysis of the distribution of organic-rich facies in the Sinemurian and Toarcian with new geochemical data [total organic carbon (TOC) and organic matter pyrolysis] from Portugal, Spain, and Morocco. The developed OMPI framework suggests a strong local control on organic matter preservation during most of the Sinemurian. Regionally widespread organic-rich facies are associated with the most negative δ13C values of the broad Sinemurian-Pliensbachian negative carbon isotopic trend (including the Sinemurian-Pliensbachian Boundary Event). Pliensbachian OMPIs are expressive in the areas bordering the proto-Atlantic Ocean and are often linked with positive δ13C excursions and short-lived warm intervals, but OMPIs are also observed for the Late Pliensbachian cool interval. Toarcian maximum TOC content occurs with the positive 513C (recovery) trend following the 513C negative shift typically linked to the Early Toarcian Oceanic Anoxic Event (T-OAE). However, superregional OMPIs predate and postdate the T-OAE, indicating that conditions favouring the preservation of organic matter (increased productivity and/or enhanced preservation) were not restricted to the T-OAE interval. We will also briefly discuss how future research should aim to disentangle (1) the complexities in estimating original TOC and organic carbon accumulation rates, (2) temporal and spatial variability in environmental or Earth system feedback mechanisms driving sedimentary carbon sequestration, and (3) their combined impact on the global carbon cycle. [ABSTRACT FROM AUTHOR]

A macroinvertebrate assemblage has been studied from the Thin Nodular Limestones Member ( TNL) of the Fonte Coberta section (Lusitanian Basin, Portugal), giving special attention to its trace fossils. The assemblage was studied to analyse the influence of the Toarcian Oceanic Anoxic Event (T- OAE) on the macroinvertebrate community. The TNL consists of thin alternations of marl/limestone and nodular limestone beds, showing clear differentiations from bottom to top. Integrative analysis of the macrofossil assemblage for the studied interval, conducted for the first time in the Lusitanian Basin, reveals three major features: (1) abundant trace fossils with dominance or near exclusiveness of Thalassinoides, and a local record of Spongeliomorpha; (2) scarcity, but not extinction, of ammonoids; and (3) the absence of previously abundant brachiopods. The findings reveal a selective incidence of the T- OAE on the macrobenthic community, with a major influence (extinction) of brachiopods, severe changes (diminution in abundance and diversity) on ammonoids and a minor effect on macrobenthic tracemakers. A complex relationship between different palaeoenvironmental conditions during the T- OAE can be interpreted, discarding anoxic conditions in the seafloor, although low oxygen conditions in the water column are a possibility. The increase in seawater temperature and availability of nutrients on the seafloor would have played an influential role. [ABSTRACT FROM AUTHOR]

Here, we present an integrated stratigraphical study across the Sinemurian-Pliensbachian interval cropping out into the Portuguese reference section of S. Pedro de Moel (Lusitanian Basin). Characterized by marl-limestone alternations of the Água de Madeiros Formation (subdivided into Polvoeira and Praia da Pedra Lisa members), this succession is particularly dominated by organic-rich facies (black shales) and contains a diverse fauna of benthic and nektonic macro fossils. This stratigraphic and sedimentary setting is the basis for a high-resolution carbon isotope study, constrained by new ammonite biochronostratigraphic determinations and other palaeontological data. The new ammonite collections characterize the Oxynotum and Raricostatum chronozones and the Raricostatum, Macdonnelli and Aplanatum subchronozones, and accurately identify the Sinemurian-Pliensbachian boundary in this western Iberian margin setting. Carbon isotope measurements were made from bulk carbonate (δ13Ccarb) from 351 samples, representing the Oxynotum to earliest Jamesoni (early Taylori) Chronozone intervals. The carbon isotope values exhibited a large range, varying between +2.85‰ in the Oxynotum Subchronozone to very negative values observed in some limestone beds from the Raricostatum Subchronozone (lowest reaching -6.7‰), a variation clearly controlled by lithological and facies changes. Despite these strong anomalous isotopically light values (below -2‰), which are clearly associated with organic matter degradation and early diagenesis, the δ13Ccarb curve shows a long-term negative trend across the Oxynotum to the early Taylori Subchronozone interval. This tendency is reversed around 5 m above the Sinemurian-Pliensbachian boundary, and the δ13Ccarb values become positive correlative with an absence of organic matter and argillaceous sediments in the limestone beds of Praia da Pedra Lisa Member. Although the δ13C data recorded across the Sinemurian-Pliensbachian of the Lusitanian Basin had been controlled by internal depositional conditions, the general evolution of carbon isotopes agrees with the trend recognized in other basins. [ABSTRACT FROM AUTHOR]

Data on lipids, carbohydrates and proteins of the most expressive black shale (s.l.) intervals of the Early--Late Pliensbachian (Early Jurassic, ˜187 Ma) organic-rich hemipelagic series of the Lusitanian Basin (Portugal) were determined using a method that has been successfully applied over the last two decades in the characterization of biomass and very immature sediments. The goal of this paper is to test the applicability of these techniques to the ancient geological record. To our knowledge, this is the first time that this type of biogeochemical data from sedimentary series older than Oligocene is reported and tentatively used for palaeoenvironmental/diagenetic inferences. Carbohydrates and proteins are present in low concentrations, reaching up to 385.13 and 451.13 µg/g rock, respectively. The main variations are observed in the lipid contents, ranging from 197.67 to 8446.36 µg/g rock. The samples with the highest amounts of lipids seem to correlate with low [O2] time intervals determined by independent data, such as organic petrography, micropalaeontology and sedimentology. This was probably related with selective lipid preservation under oxygen and hydrogen sulfide-rich depleted environments. The good overall match between the determined lipid contents and specific depositional/early diagenetical conditions seem to favor the idea that the easy to perform and inexpensive method applied here has the potential to add useful information to the study of ancient organic-rich carbonate sedimentary series. [ABSTRACT FROM AUTHOR]

The study across the Pliensbachian–Toarcian boundary sedimentary record in the Bizanet section of the Pyrenean Basin (southern France) revealed the presence of solid bitumen. This secondary organic matter was characterized using petrographic (transmitted and reflected white lights, incident blue light, and scanning electron microscopy) and geochemical (total organic carbon, total sulfur, and insoluble residue) techniques. The spore coloration index (SCI) was also determined. With the characterization of the optical properties and reflectance of the solid bitumen, it was possible to distinguish four different families (A–D) that display a wide range of reflectance values, from 0.21% to 2.64% BRr, i.e., from glance pitch to meso-impsonite. SCI values were higher than 9–9.5 (%Req > 1.50%). The comparison between the equivalent vitrinite reflectance values of the solid bitumen and SCI showed that this index and the solid bitumen D values are concordant, indicating that solid bitumen D can be considered an indigenous bitumen. The other three families of solid bitumen (A–C) are considered as having migrated. The laterally equivalent Pont de Suert section (South Pyrenean Zone) displays no trace of solid bitumen which points to the important role of the morphotectonic context of the Bizanet section in the migration of these hydrocarbons, namely, the presence of a major thrust fault in the eastern Corbières close to the section's location. [ABSTRACT FROM AUTHOR]

The Santos Basin in offshore Brazil belongs to the major carbonate reservoir province known informally as the Pre-Salt. A detailed analysis of cores, plugs, sidewall samples and thin-sections from two wells in a sector of this basin was undertaken, on an interval corresponding to the upper part of the Lower Cretaceous Barra Velha Formation. Several facies and subfacies types have been classified independently from existing terminologies for these carbonate rocks. The specific features of the studied material are discussed and comparison to other nomenclatures is made. The facies include, namely: laminated argillaceous limestones; in-situ grown carbonates with a range of singular morphologies (of debatable origin), from laminar crust, stromatolitic-like fabric to robust or delicate shrubby structures; intraclastic grainstones/packstones, whose clasts may be mostly remnants of shrubs or differ; spherulitic grainstones/packstones; locally, oncoidal grainstones/rudstones and packstones/floatstones. These rocks are interpreted as depositional and diagenetic or essentially diagenetic facies. The latter are regarded as originally similar to some of the former ones but now "disguised", because they were differently impacted by diagenesis processes over different time periods. Recognizing these effects is relevant, because they produce different reservoir facies characteristics and quality. The best potential reservoirs are some of the depositional and the mostly diagenetic facies. The palaeoenvironmental setting of the studied facies fits into a shallow, low-gradient lake. Charophyte and other possible, unidentified algae, albeit extremely rare, are documented for the first time. The facies pattern shows some cyclicity, suggestive of both water depth and chemistry changes. If the interpretations in this study are correct, they (i) reinforce existing datasets to improve understanding of these facies; (ii) raise caution concerning some facies previously considered as separate depositional products, which in fact may instead result from diagenetic modifications; (iii) stress the relevance of microfacies analysis and diagenetic petrography to help deciphering how diagenetic modifications impact on reservoir facies properties and quality; and (iv) add new issues to the naming and textural classification problems of the Brazil Pre-Salt carbonates. • High-resolution characterization and illustration of Pre-Salt facies (microfacies). • Distinguishing depositional and diagenetic facies with reservoir potential. • Contribution to classification of the Pre-Salt carbonate rocks. • Identification for the first time of charophytes in the Pre-Salt carbonates. • Contribution to the palaeoenvironmental interpretation of these facies. [ABSTRACT FROM AUTHOR]