Decapod fauna from the lower Aptian in the Valencian sector of the Maestrat Basin (NE Iberia)

Two decapod (Arthropoda: Malacostraca: Decapoda) assemblages from two newly discovered localities near Torreblanca (Castelló, Valencian Country, Spain), situated in the Orpesa Sub-basin of the Maestrat Basin, are described. The first assemblage exhibits a diverse fauna of lobsters, including erymoids, glypheoids and nephropoids representatives of five different genera, some of them reported for the first time in Iberia, as well as brachyuran crabs, primarily palaeocorystoids, including one new species, Paranecrocarcinus xivertensis. It is assigned to the uppermost Aptian of the Benassal Formation. The second assemblage, found in the lower Albian Escucha Formation, showcases an exceptional richness of exquisitely preserved complete remains of a new genus and species of axiidean ghost shrimp, Cretagourretia salasi, along with some palaeocorystoids, also representatives of a new species, Joeranina tausi, within a varied community of invertebrates and plants. This work investigates the paleoenvironment in which these assemblages thrived, and explores their faunal similarities with other decapod assemblages from the nearby Garraf Basin, as well as more distant ones such as the Basque-Cantabrian Basin and the Isle of Wight. An ammonite occurrence, likely belonging to the genus Roberticeras, has been identified in the upper Aptian Benassal Formation. Additionally, the juvenile stage of the ammonite Parengonoceras bassei from the lower Albian Escucha Formation is reported and described for the first time. The study provides valuable insights into reconstructing coastal to marine environments and the associated biota that developed in the Maestrat Basin during the Aptian-Albian transition.

Comprehensive analysis of the Cretaceous and Tertiary decapod crustaceans of the North Pacific Rim, focused primarily on the Brachyura, has resulted in additions to our understanding of the evolution and distribution of these animals, both in that region and globally. Hypotheses about changes in climatological and paleoceanographic conditions have not been extensively tested using decapod crustaceans, although they have been well-documented globally and for the North Pacific Ocean by sedimentological and other faunal evidence. Evidence from the occurrences of decapod crustaceans supports hypotheses obtained through these other means. Because the decapod fauna was studied independent of other faunas, it provides a means by which to compare and test patterns derived from molluscan and other faunal data. The brachyuran decapods show distinctive paleobiogeographic patterns during the Cretaceous and Tertiary, and these patterns are consistent with those documented globally in the molluscan faunas and paleoceanographic modeling. Additionally, the changes in the decapod fauna reflect patterns unique to the North Pacific Ocean. The decapod fauna is primarily comprised of a North Pacific component, a North Polar component, a component of Tethyan derivation, an amphitropical component, and a component derived from the high Southern latitudes. The Cretaceous and Tertiary decapod faunas of the North Pacific Ocean were initially dominated by taxa of North Pacific origin. Decapod diversity was highest in the Pacific Northwest of North America during the Eocene, and diversity has declined steadily since that time. Diversity in Japan was relatively low among the Decapoda until the Miocene, when diversity increased markedly due to the tropical influence of the Tethys and Indo-Pacific region. Diversity has remained high in Japan into the present time. The Cretaceous, Eocene, and Miocene were times of evolutionary bursts within the Brachyura and were separated by periods of evolutionary stasis.

Comprehensive analysis of the Cretaceous and Tertiary decapod crustaceans of the North Pacific Rim, focused primarily on the Brachyura, has resulted in additions to our understanding of the evolution and distribution of these animals, both in that region and globally. Hypotheses about changes in climatological and paleoceanographic conditions have not been extensively tested using decapod crustaceans, although they have been well-documented globally and for the North Pacific Ocean by sedimentological and other faunal evidence. Evidence from the occurrences of decapod crustaceans supports hypotheses obtained through these other means. Because the decapod fauna was studied independent of other faunas, it provides a means by which to compare and test patterns derived from molluscan and other faunal data. The brachyuran decapods show distinctive paleobiogeographic patterns during the Cretaceous and Tertiary, and these patterns are consistent with those documented globally in the molluscan faunas and paleoceanographic modeling. Additionally, the changes in the decapod fauna reflect patterns unique to the North Pacific Ocean. The decapod fauna is primarily comprised of a North Pacific component, a North Polar component, a component of Tethyan derivation, an amphitropical component, and a component derived from the high Southern latitudes. The Cretaceous and Tertiary decapod faunas of the North Pacific Ocean were initially dominated by taxa of North Pacific origin. Decapod diversity was highest in the Pacific Northwest of North America during the Eocene, and diversity has declined steadily since that time. Diversity in Japan was relatively low among the Decapoda until the Miocene, when diversity increased markedly due to the tropical influence of the Tethys and Indo-Pacific region. Diversity has remained high in Japan into the present time. The Cretaceous, Eocene, and Miocene were times of evolutionary bursts within the Brachyura and were separated by periods of evolutionary stasis.

The term “reef” has been frequently misused when applied to fossil coral communities. Our popular but biased view of coral community structure based on the idyllic picture of recent tropical reefs has failed to recognize that, in many fossil examples, alternative states of community structure with no or limited framework may occur. The Aptian colonial scleractinians analysed in the western Maestrat Basin (eastern Spain) constitute an example of non-reef-building coral populations, which thrived in marly slope settings. These corals developed within the photic zone but below the storm wave-base. All colonies are found well-preserved in life position. They are mostly decimetres in size and mainly occur isolated giving rise to a continuous and uniform (dominated by domal and massive forms) unbound growth fabric with a low to medium degree of development (coral skeletal volume = 5–20%). Occasionally, however, colonies growing on top of each other forming small metre-sized bioherms are also present. A total of 21 species were identified. Coral diversity in each sample location varies between three and nine species. These numbers of species are comparable with those exhibited by coeval coral assemblages from other basins of the Tethys, but are comparatively low when compared with diversities exhibited by many Recent and fossil coral communities. The corals studied apparently found optimal ecological conditions for their development on the marly slopes of the western Maestrat Basin. This is primarily expressed in the unusually large dimensions (up to 2.3 m in width) of some of the coral colonies when compared to other Cretaceous occurrences, and in the persistence and resilience of the coral populations. The observed coral genera and species (suborders Archeocaeniina, Faviina, Fungiina and Microsolenina) are very common in the time interval between the Barremian and the Early Albian and most of them have been reported from several other localities in the western and central Tethyan realm. In addition, the coral-bearing levels also contain the poorly known and exotic genera Agrostyliastraea and Procladocora. There are no significant differences at species level or in community structure between the Early and Late Aptian faunas investigated. Therefore, the coral communities as well as the environmental conditions controlling them would have been relatively stable during the time intervals when these corals flourished. An important palaeoecological implication is that comparatively low species diversities and the absence of reef frameworks do not necessarily imply unfavourable environmental conditions for coral growth. Furthermore, this study may serve as an example for the analysis of other level-bottom coral communities displaying a loose growth fabric.

Patterns in the distribution of Aptian rudists and corals within a sequence-stratigraphic framework (Maestrat Basin, E Spain)

Outcrop-scale reconstruction of depositional geometries and facies distribution of carbonate systems improves our knowledge on their heterogeneity distribution, stacking patterns and stratal architecture. The collected data and derived models can be used as analogues for characterizing and modelling potential subsurface reservoirs. Traditional sedimentological analyses in cropping out carbonate systems have limited accuracy depending on exposure conditions, accessibility or past erosive processes. On the other hand, there is a need to complement classical sedimentological approaches with quantitative characterizations and models of sedimentary bodies. In this respect, processing of three-dimensional (3D) point clouds captured by terrestrial LIght Detection And Ranging (LIDAR) technology combined with real-time kinematic global positioning system offers to field geologists the possibility to construct virtual 3D digital outcrop models (DOMs), which allow for more accurate analyses, reconstructions and quantification of the outcropping facies distribution than conventional digital terrain models. We present a LIDAR 3D DOM of an Aptian flat-topped non-rimmed carbonate platform margin from the western Maestrat Basin (Spain). The DOM served as a departing point to perform a 3D reconstruction that shows the relationship between depositional architecture and facies distribution of the carbonate system. The reconstruction not only highlights the value of digital outcrop models to characterize virtual attributes not observable in the outcrops due to the limitations of the 2D views of the exposures, but also allows to refine outcrop-scale sequence stratigraphic analyses. In addition, the 3D sequence stratigraphic approach obtained together with the 3D facies distribution model generated can be used as an analogue for the characterization of subsurface carbonate reservoirs with similar depositional profiles. The workflow of this study followed these steps: 1) Acquisition of the outcrop 3D point data set using a ground-based terrestrial LIDAR equipped with a differential GPS; 44 overlapping scans were needed to cover the entire outcrops of the flat-topped non-rimmed carbonate system characterized, each scan has associated a high-resolution photograph. 2) Mapping stratigraphic surfaces and pseudowells describing 5 lithofacies onto each individual photograph using a CAD-based tool, the mapping is carried directly onto the photographs because manipulating the images and interpreting the details is easier than directly digitizing onto the point-cloud. 3) The features mapped onto the photographs are projected into the corresponding point-cloud in order to georeference them. 4) Locally georeferenced individual point-clouds and attached interpretations were globally georeferenced by means of the UTM coordinates of each scan. 5) The stratigraphic boundaries mapped are used reconstruct the surfaces bounding stratigraphic units. 6) Population of the internal facies distribution conditioned to the pseudowells. This methodology allows to efficiently extracting information from point clouds, and resulted in the construction of a high-resolution 3D geological model displaying the stratal architecture and facies heterogeneity of sedimentary bodies, confined within a 3D sequence stratigraphical framework.

We report an integrated study of an expanded and relatively complete syn-rift continental to epeiric marine succession of Aptian age, cropping out in the western Maestrat Basin (eastern Iberian Chain). Four transgressiveregressive sequences are recognized throughout this mixed carbonate-siliciclastic succession, with excellent age control provided by ammonite biostratigraphic data. The transgressive systems tracts consist mainly of alternations of marls and limestones rich in orbitolinids. The regressive systems tracts are essentially characterized by wave- and tidally influenced siliciclastic and carbonate deposits, and by the development of carbonate platforms with rudists, corals, orbitolinids and green algae. Carbon and oxygen isotope curves were established in order to identify the global d13C perturbations related to the Early Aptian Oceanic Anoxic Event (OAE1a). These perturbations commence with a horizon of coral rubble encrusted by Lithocodium aggregatum and Bacinella irregularis with widespread large-sized discoidal Palorbitolina lenticularis. Associated d18O values indicate high-frequency cooling-warming climatic cycles. The fault-controlled rapid syn-rift subsidence recorded during this stage was the most important factor in producing accommodation. However, the major transgressions, sea level falls and biotic changes recorded in the eastern Iberian Chain are in agreement with those registered in other contemporaneous basins of the Tethys. Thus, the resulting sedimentary succession faithfully reflects the major oceanographic and climatically-driven global changes that characterized this stage albeit within a context established by regional tectonics. Hence, this well-documented record of the evolution of an Aptian epicontinental sea provides a useful comparative case study for the analysis of other Aptian epeiric sedimentary successions.

Middle Permian brachiopods from the Tumenling Formation in the Wuchang area, southern Heilongjiang, NE China, and their palaeobiogeographical implications

Biostratigraphic characterization by means of ammonoids of the lower Aptian Oceanic Anoxic Event (OAE 1a) in the eastern Iberian Chain (Maestrat Basin, eastern Spain)

The decapod fauna from the Badenian (middle Miocene) deposits of western Ukraine comprises in total 31 taxa: 20 species, 9 taxa left in open nomenclature, and 2 determined at family level. Thirteen of these taxa are reported for the first time from the territory of Ukraine. Among them are the first records of Trapezia glaessneri Muller, 1976 in the Fore-Carpathian Basin and Pachycheles sp. in Paratethys. One taxon ( Petrolisthes sp. A) probably represents a new species. The occurrence of this significant decapod fauna is restricted almost exclusively to the Upper Badenian (i.e., early Serravallian) coralgal reefs of the Ternopil Beds. The taxonomic composition of the decapods indicates that the Late Badenian depositional environment was a shallow marine basin dominated by reefs that developed in warm-to-tropical waters of oceanic salinity. The decapod assemblage from the Ternopil Beds is similar in its taxonomic composition to numerous decapod faunules from fossil reefs of Eocene to Miocene age from the Mediterranean realm and of Miocene age from Paratethys. In contrast, decapod remains are very scarce in Badenian siliciclastic deposits (Mikolaiv Beds) and are represented by the most resistant skeletal elements, i.e., dactyli and fixed fingers. This scarcity was caused by the high-energy environment, with frequent episodes of redeposition, which disintegrated and abraded the decapod remains.

The present paper analyses the stratigraphic distribution of ammonites collected in the Lower Aptian sediments of the Maestrat Basin (E Spain). The faunal successions obtained from the systematic sampling of ten selected sections located in several sub basins led us to identify four biostratigraphic units (from base to top: Deshayesites oglanlensis, Deshayesites forbesi, Deshayesites deshayesi and Dufrenoyia furcata Zones) that are directly correlatable with the current Mediterranean standard zonation. This study further provides essential biochronologic information to accurately date the different lithostratigraphic units included in the interval studied. Thus, the upper part of the Xert Formation can be tentatively attributed to the lowermost Aptian (D. oglanlensis Zone). The Forcall Formation, which has yielded most of the ammonites, practically extends within most of the Lower Aptian. Its lower and middle parts (Cap de Vinyet and Barra de Morella Members) correspond to the upper part of the D. oglanlensis Zone and the lower part of the D. forbesi Zone, respectively. The base of the Morella la Vella Member (upper part of the Forcall Formation) includes the local record of Oceanic Anoxic Event 1a (OAE 1a) and correlates with the Roloboceras hambrovi horizon (middle/upper part of the D. forbesi Zone). The boundary between the Forcall Formation and the Villarroya de los Pinares Formation is diachronous and varies depending on the sub-basins. The base of the Villarroya de los Pinares Formation can be dated as the middle-upper part of the D. furcata Zone in the Galve, Perello and Salzedella sub-basins.

Four 200-m depth strata were sampled for fish and decapod crustaceans on the upper continental slope (400–1200 m) off Nova Scotia. There was more-or-less continuous replacement of fish fauna with depth. Numerically dominant fishes in the upper two strata (< 800 m) were Sebastes spp., Phycis chesteri, and Glyptocephalus cynoglossus. Predominant fishes in the lower two strata (> 800 m) were Centroscyllium fabricii, Synaphobranchus kaupii, and Coryphaenoides rupestris. Nezumia bairdii was relatively abundant throughout the depth range sampled. The ichthyofauna of the upper slope was similar to that off the Middle Atlantic States and off Newfoundland at comparable depths, but qualitative differences existed in losses of some and additions of other species. Dominant decapod crustaceans in the shallowest stratum (200–400 m) were Pontophilus norvegicus, Plesiopenaeus edwardsianus, and Panalus propinquus. This stratum appeared to be a transition zone between shelf and slope decapod faunas. More species occurred and at higher densities in the deeper strata; predominant were Acanthephyra spp., Pasiphaea tarda, Metacrangon jacqueti, and Sabinea hystrix. The decapod fauna off Nova Scotia is similar to that of the mid-Atlantic Bight but less diverse.

C-isotopes, TOC and O geochemical data from the lower Aptian Cuchía section in the western Basque-Cantabrian basin (BCB) allow an accurate delimitation of the OAE1a-equivalent and its geochemical Menegatti´s segments, a detailed δ13Ccarb correlation with regional and interregional sections, and a high-resolution construction of TOC and bulk-rock δ18Ocarb curves and their interpretation. The δ13Ccarb values range from -2‰ and +4‰ (VPDB). They agree with previous data from the eastern BCB sections (Aralar) confirming the ammonite age of the OAE1a in the Basque-Cantabrian basin: Deshayesites forbesi, Deshayesites deshayesi, and Deshayesites deshayesi-Dufrenoyia furcata transition Zones. Interregional δ13Ccarb correlation with pelagic (Cismon, Italy, and Mid-Pacific Mountains, DSDP Site 463) and neritic (Roquefort-La Bédoule, France) core sections, reveals a common profile of a wide negative excursion characteristic of the OAE1a. It consists of a double trough separated by a flat relative maximum, with two negative spikes in the upper trough of neritic sections. TOC absolute values range from 0.12% to 1.37%. Segments of the TOC curve with persistent low values closely correspond with descending segments of the δ13Ccarb curve, and are attributed to lesser organic productivity in the BCB. Detailed bulk-rock δ18Ocarb data (-5.71‰ to -1.05 ‰ PDB) and variation curve show two main positive O-isotope shifts and three minor positive inflections, within a general negative trend characteristic of the OAE1a. The two major positive shifts correspond to both shallowing upwards sequences and the lowermost can be related to a eustatic sea level fall. Independent interregional correlation of the O-isotope shifts with C-isotopes supports their interpretation as punctuating colder events within a general warming trend.

Fossiliferous amber deposits from the Cretaceous (Albian) of Spain

This investigation is aimed to study the morphological variability of the polyconitid rudist, Polyconites hadriani, from the Aptian carbonate platforms of the western Maestrat Basin, in Iberia. The individuals of the platform top to upper slope carbonates differ from those of the slope deposits in the size and external shape of the shell. Therefore, the populations of these two distinct platform habitats were compared by morphometric measures (dorso-ventral commissural diameter and antero-posterior commissural diameter). The results of the morphometric analysis showed that shell size and shell form were correlated with depth. (1) Larger shells occur in the slope deposits while smaller shells in the shallower platform top to upper slope settings; (2) commissural outline is compressed dorso-ventrally in the individuals from the platform top to upper slope environments and in half the individuals from the slopes, whereas the commissural outline is compressed antero-posteriorly in the other half of the slope group. It is suggested that phenotypic plasticity allowed P. hadriani to adapt shell growth to the different ecological conditions prevailing in the two habitats.