Se cierra una etapa con el volumen 5 de la Revista y ahora nos encontramos ante un nuevo reto. No falta razón a este planteamiento, pues no sólo supondrá doblar ampliamente todo el proceso que lleva a la publicación, aunque esto ya está asumido por el Consejo de Redacción, sino que será necesario que el flujo de trabajos ofrecidos a la Revista se mantenga y, preferentemente, aumente en relación con el de este último año. Ahí está el reto principal, concierne mayormente a todos los socios. Los cinco volúmenes y el número extraordinario publicados comprenden un total de 696 páginas y 65 trabajos. Estos tienen una amplia distribución temática, así 3 son de Tafonomía/ Paleoecología; 3 Morfología/Biometría; 5 Bioestratigrafia; 11 Evolución; 4 lcnología; 2 Trilobites; 5 Braquiópodos; 7 Moluscos; 9 Micropaleontología; 6 Vertebrados y 4 de otros grupos. También están representados varios lapsos temporales geológicos: Paleozoico inferior (3); Devónico (4); Carbonífero (4); Triásico (l); Jurásico (3); Cretácico (10); Paleógeno (8); Neógeno (12) y Cuaternario (2). De ellos están escritos en español 42 y en inglés 23.

The Basco-Cantabrian Domain (Basco-Cantabrian Basin of some authors) represents the eastern part of the southern side of the Bay of Biscay. In Late Cenomanian, as a result of previous environmental and morphological modifications, it was composed of two approximately E-W oriented elements, which are, from north to south: A deep marine area and a marine shelf called the Navarro-Cantabrian Platform. The deep marine area comprised two major elements that were, from north to south: a) An E-W oriented and westward open depression: the Saint-lean-de-Luz Trough; b) A topographically higher region: the Biscay-Guipúzcoa Shallows. It connected at north, through a northward dipping slope, with the St-J-Luz Trough. At south, it rose up to the Navarro-Cantabrian Platform and its limit might correspond to a great structural element: the Bilbao Fault (Amiot, Floquet, Mathey, 1982; Engeser et al., 1984). The southeastern part of the B-C Shallows was a small, always E-W trending despression: the Plencia Trough. On the contrary, its eastern part was a shoal: the Basque Shoal, whose some sectors are small platforms of inner type, whereas some other are emerged. The eastern limit of the whole deep marine area could correspond with an alignment of diapirs: the. Line of Navarra Diapirs (Rat, 1983). During the Cretaceous, that line separated an Occidental and Navarro-Cantabrian domain from an Oriental and Pyrenean one.

En el Monte Urko hay una sección sin interrupciones sedimentarias que comprende el paso Cretácico-Terciario (K/T). El estudio de la nanoflora realizado cuantitativamente sobre un total de 500 ejemplares por muestra, escogidos al azar, pone de manifiesto una asociación típica de la Zona de Mictila murus, con Watznaueria barnesae (Black), Micula decussata Vekshina, Prediscosphaera cretacea (Arkhangelski), Arkhangelskiella cymbifornis Vekshina y Cribrosphaerella ehrenbergii (Arkhangelski) como especies más abundantes. En el Terciario basal la asociación de nanoflora contiene las mismas especies encontradas en el Maastrichtiense superior, pero su proporción se reduce del 94% al 78% del total de la asociación, mientras que las especies persistentes (Cyclagelosphaera reinhardtii (Perch-Nielsen), Markalius inversus (Deflandre), Thoracosphaera spp. y Braarudosphaera spp.) pasan del 6% al 22% aumentando progresivamente en términos más altos hasta el 79%. Especímenes atribuibles dudosamente a la especie terciaria Biantholithus sparsus Bramlette y Martini se han detectado a unos 25 cm sobre el límite K/T. Las especies persistentes, interpretadas como oportunistas, muestran un aumento en los últimos centímetros bajo el límite K/T; así se pasa de su práctica ausencia a unos 30-40 cm, al 3-6 % en los últimos 15 cm. Este aumento, que puede interpretarse como una inestabilidad del ecosistema, no queda reflejado en la δ13C hasta que se traspasa el límite K/T, con una variación máxima del 2 ‰ en los 10 cm basales del Daniense, coincidiendo con los cambios más importantes de la nanoflora, los porcentajes más altos de Thoracosphaera spp., y los cambios en las asociaciones de foraminíferos planctónicos.

Investigations of calcareous nannoplankton assemblages including species richness and abundance data were performed across the K–Pg boundary interval at Agost (SE Spain), between −100cm and +100cm, below and, respectively, above the boundary, at a considerable high resolution averaging 2cm. From a total of 98 species of the Upper Maastrichtian, only 13 survived mass extinction, while the rest of the 86% vanished in the K–Pg fallout layer. A slight progressive decline in species richness and abundance was observed toward the top of the Maastrichtian, where mixed assemblages, consisting of both cold-water taxa and typical Tethyan ones are present. Four successive acme events were observed, i.e. Markalius inversus and the calcareous dinoflagellate genus Thoracosphaera starting from the base of the Paleocene, followed by those of Braarudosphaera bigelowii and Neobiscutum parvulum. The most prominent acme intervals belong to Thoracosphaera spp. and B. bigelowii, opportunistic taxa, for which the survival strategy may be linked to their capability to encyst and survive severe environmental deterioration. At the upper part of the studied succession, calcareous nannoplankton assemblages are already dominated by survivor species, as well as incoming ones, showing an early pioneer calcareous nannoplankton ecosystems about 35–40kyr after the K–Pg boundary. Correlation between the calcareous nannoplankton assemblage fluctuation, including species richness and abundance, and the paleoenvironmental changes, such as the eustatic and climatic modifications, are also discussed.

The GSSP for the base of the Santonian Stage is defined at 94.4 m in the eastern border of the "Cantera de Margas" quarry, Olazagutia (Navarra, N. Spain: 42 degrees 52' 05.3 '' N, 2 degrees 11' 40 '' W) and marked by the first occurrence (FO) of the inoceramid bivalve Platyceramus undulatoplicatus. This first occurrence is located about 9 in below the contact between a lower marly unit and an upper more calcareous unit. The FO of the planktonic foraminifer Sigalia carpatica is the secondary marker of the GSSP and first occurs 7 m below the primary marker, but it becomes consistently present about 4.2 m above the boundary. In addition, six peaks in the carbon stable isotope curve can be recognized between the Kingsdown Event 17.2 m below and the Bedwell Event 12.35 m above the GSSP. The basal Santonian GSSP was approved by the International Subcommission on Cretaceous Stratigraphy in September 2010, by the International Commision of Stratigraphy in April 2012, and ratified by the International Union of Geological Sciences in January 2013.

Oceanic Anoxic Event 2 (OAE 2) during the Cenomanian–Turonian (C/T) transition caused stepwise marine extinctions. Using organic compounds, stable carbon and oxygen isotopes, and foraminifera from three depth-transect sections in northern Spain, this study revealed repeated anoxic/euxinic events coinciding with warming and stepwise extinctions of planktonic and/or benthic foraminifera within intermediate to surface waters in the proto-North Atlantic during the C/T transition. Those short-duration euxinic events occurred four times: at 93.95Ma, marked by the extinction of Rotalipora greenhornensis; at 93.90Ma, marked by the extinction of Rotalipora cushmani; at the mid-time maximum of the plateau of the δ13C of carbonates (93.70Ma); and at the time of the C/T boundary (93.55Ma). Furthermore, the main benthic foraminiferal extinctions occurred during the first and second euxinic events in the upper slope, during the second and third euxinic events in the outer to middle shelf, and during the third and fourth events in the middle shelf. The main euxinic events in each section also showed a progression to the shallow shelf. The main anoxia–extinction events occurred in the upper slope and outer shelf then moved to the middle shelf. The shallowest section had relatively weak anoxia and a proportionally low extinction rate. These new findings indicate that foraminiferal extinctions started from the intermediate water and the continental slope and then moved to the continental shelf. This was the result of the repeated progression of euxinic–anoxic water from the upper slope to the middle shelf on the eastern continental margin of the proto-North Atlantic four times during a 400kyr period, to the end of the Cenomanian.

Abstract The Cenomanian–Turonian boundary interval of the Arobes section, northern Spain, represents the maximum depth of a relatively shallow succession. The investigated section extends within the Rotalipora cushmani and Whiteinella archaeocretacea planktonic foraminiferal zones, and from UC3 up to UC8 nannofloral zones, respectively. The Oceanic Anoxic Event 2 (OAE2) is about 16 m thick and includes a positive δ13C excursion, from 3 up to 5.5‰. The first peak of δ13C is situated towards the upper part of the Rotalipora cushmani planktonic foraminiferal zone, while the second peak of δ13C is situated in the lower part of the Whiteinella archaeocretacea planktonic foraminiferal zone. The plateau, the youngest phase of OAE2, ends slightly above the first occurrence (FO) of the nannofossil Quadrum gartneri. Based on nannofloral fluctuation, an unstable environment is recognized from the last occurrence (LO) of the nannofossil Axopodorhabdus albianus up to the FO of the nannofossil Quadrum gartneri. Mesotrophic, eutrophic and oligotrophic nannofossils have successive peaks throughout the OAE2. In the lower part of OAE2, especially in the trough phase and second build-up, productivity increased. The calcareous dinoflagellate Thoracosphaera spp. peaks up to almost 30% in the lower part of the second build-up phase. The critical nannofloral turnover episode is characterized by impoverished calcareous nannofossil assemblages and temporary disappearances of high-fertility taxa, such as Biscutum constans and Zeugrhabdotus erectus. This shift in nannofloral assemblages starts in the last stages of OAE2; that is, towards the top of the second build-up phase and also covers the main part of the plateau phase of δ13C.

Oceanic anoxic event 2 (OAE2), which occurred during the Cenomanian-Turonian (C-T) transition and lasted 1 m.y., is characterized by a positive global carbon isotopic excursion and stepwise extinctions in marine biota. To examine temporal variations in the dissolved oxygen content of the water column, shallow-marine C-T sediments from northern Spain were analyzed for concentrations of dibenzothiophenes, which are indicators of euxinic depositional environments, and 2,3,6-trimethylarylisoprenoids, which probably indicate photic-zone euxinia. The positive excursion in delta C-13 values of carbonates is accompanied by short-term (10(3)-10(4) yr) and long-term (10(5) yr) increases in dibenzothiophene and 2,3,6-trimethylarylisoprenoid concentrations, suggesting that the bottom water and photic zone of the eastern marginal sea of the North Atlantic Ocean were euxinic. Two of the short-term increases in organic compound concentrations took place just after the last occurrence of the planktonic foraminifers Rotalipora greenhornensis and R. cushmani. These transient maxima indicate that the extinction of both planktonic foraminifers was due to short-term OAEs lasting 10(3)-10(4) yr.

Detailed rock magnetic properties of four sedimentary marine sections spanning the CretaceousTertiary boundary have been investigated in the Iberian Peninsula. In Agost and Caravaca (SE Spain), which present a very good preservation state of the impact ejecta layer that defines the boundary, the magnetic fingerprint of impact-generated Mg-Ni-rich spinels is revealed by increases of one order of magnitude in magnetic susceptibility and isothermal remanent magnetization (IRM), associated with a decrease in coercivity of remanence. This dominant ferrimagnetic phase is accompanied by a significant amount of high-coercivity antiferromagnetic material, mainly goethite with very fine grain sizes and haematite, resulting from early diagenesis under the anomalous post-impact conditions. Rock magnetism supports a post-impact increase in the terrigenous/carbonate ratio during the early Danian, followed by a recovery of carbonate production that exceeds the end-Maastrichtian values. Zumaya and Sopelana (N Spain) present worst preservation states of the impact ejecta layer. In Zumaya some patches of impact material are found on top of the calcite layer that separates the end-Maastrichtian from the K-T boundary clay. In these patches, increases in susceptibility and IRM and a decrease in coercivity of remanence point to the presence of Mg, Ni-rich spinels of meteoritic origin. In Sopelana, no vestiges of the impact ejecta layer were found, and consequently there is no magnetic evidence of meteoritic Mg-Ni-rich spinels; although the sampled interval is too narrow, magnetic properties point to a recovery of carbonate production in the early Danian exceeding that of the end-Maastrichtian, in agreement with Agost and Caravaca results.

The FO of the inoceramid Platyceramus undulatoplicatus in the eastern border of the “Cantera de Margas”, Olazagutia, northern Spain, was selected by the Santonian Working Group as GSSP for the base of the Santonian Stage, in November 2007. As it was circulated on December 14th, 2007, the Olazagutia section was selected with 24 favorable votes (Ten Mile Creek got 6 votes; Abstain: 4 votes, and 1 negative vote for both candidates), in total 35 persons returned ballot-paper on time (2 votes where sent later that the dead-line). These 35 delivered valid votes are around 73% of all possible votes (48). The 24 favorable votes received by Olazagutia are around 68% of valid votes (35). In both cases these figures are more than 60% required for a quorum and a valid decision, respectively. Following the procedures of the International Commission on Stratigraphy, we have produced this proposal for the consideration of the International Subcommission on Cretaceous Stratigraphy.

The Upper Coniacian–Lower Santonian marine sediments of two sections in the Romanian Carpathians were investigated for their calcareous nannofossil content. These sections were previously dated based on macro- and microfaunal assemblages. The first occurrence (FO) of the inoceramid species Platyceramus undulatoplicatus, the primary marker for the Coniacian/Santonian boundary interval, was not identified. The boundary was identified based on the FOs of the ammonite genus Texanites and of the planktonic foraminifer Dicarinella asymetrica. In terms of the nannofossils, the Coniacian/Santonian boundary in the Romanian Carpathians falls within the UC11c (equivalent to CC16) Nannofossil Zone, between the FO of Lucianorhabdus cayeuxii and the last occurrence (LO) of Lithastrinus septenarius. The succession of the nannofloral events identified in the Romanian Carpathians (the FO of Lithastrinus grillii followed by the FO of Lucianorhabdus cayeuxii and by an increased abundance of holococcoliths and Micula concava) is similar to that recorded in the Olazagutia section of northern Spain. A comparison of the nannofossil biostratigraphy focused on the Coniacian/Santonian boundary interval in other European regions, mainly in low to middle-latitudes, is also presented.

Carbon and oxygen stable isotopes have been analysed from 56 bulk sediment samples taken through an 85m section across the first occurrence of the planktonic foraminiferan Abathomphalus mayaroensis at Zumaya, and from 10 samples across the same level at Sopelana, Basque Country, Spain. At Zumaya, carbon isotope values lie between +0.82 and +2.38‰ VPBD and correlate well with lithology. Oxygen isotope values lie between −4.00 and −2.72‰ VPBD and correlate weakly with lithology. At Sopelana, carbon isotope values range from 1.48 to 1.83; oxygen isotope values from −3.40 to −2.30‰VPBD. A carbon versus oxygen isotope cross-plot indicates some diagenetic overprinting. Oxygen isotope values imply palaeotemperatures of 27–32°C, confirming some diagenetic influence. A smoothed carbon isotope curve shows a peak in unit 6, two troughs in unit 7, a peak in unit 8, declining values in unit 9 and another trough in the lower half of unit 10. This pattern correlates well with the limited carbon isotope curve for Sopelana. The two minima adjacent to the first occurrence of A. mayaroensis, the lower of which coincides with the first occurrence of the calcareous nannofossil Lithraphidites quadratus, may prove useful in international correlation of the Lower–Upper Maastrichtian boundary.

Clay mineralogy and whole-rock stable isotopes (δ18O and δ13C) of Upper Cretaceous marly sediments on the Basque-Cantabrian Basin have been integrated to determine the main effects of diagenesis, palaeoclimate and tectono-sedimentary factors in sections belonging to deep- (Barrika) and platform-marine (Isla de Castro, Villamartín and Olazagutía) settings.The mean values for the clay assemblages and δ18O exhibit notable differences among the sections, partially explainable by the influence of diagenesis. The Barrika sediments, with more diagenetically advanced illite-smectite (I-S) mixed-layer (R1, 70% illite), authigenic chlorite, and low δ18O (−4.05‰ PDB), experienced higher diagenetic grade than Isla de Castro and Olazagutía, which have R0 I-S (20% illite) and heavier δ18O. Villamartín was also affected by higher diagenesis than Isla de Castro and Olazagutía, given the occurrence of R1 I-S (60% illite) and low δ18O (−4.11‰ PDB). However, the absence of other clays in Villamartín (e.g. authigenic chlorite) is indicative of less diagenetic grade than Barrika. These results show the useful integration of clay mineralogy and stable isotopes to detect different diagenetic grades in distinct marine successions of the same basin.Despite being influenced by diagenesis, the clay mineralogy partially preserves its inherited signature. This allows detection of major contents of I-S and mica, and minor kaolinite, interpreted as indicative of warm palaeoclimatic conditions. High kaolinite content in Villamartín and absence of kaolinite in Isla de Castro, though, are considered to be a product of neither diagenesis nor palaeoclimatic influences. Instead, tectono-sedimentary causes, related to unsuitable conditions for clay formation and transport from the local source areas, contributed to original clay differences. The inferred effects of diagenesis, palaeoclimate and tectono-sedimentary factors make this work important to show the potentially great variety of controls on the clay mineralogy of marine sections, which are often uncritically treated in studies concerning the Late Cretaceous.

The interval studied comprises a 45-m-thick section of uppermost Coniacian and lower Santonian strata. More than 30 planktonic foraminiferal species were recorded. The following sequence of bioevents is recorded from bottom to top: (1) FO of Sigalia carpatica; (2) FO of Costellagerina pilula; (3) FO of typical “pill-box-like” morphotypes of Globotruncana linneiana. The planktonic foraminifera allow the subdivision of the section studied into two heterohelicid zones: Pseudotextularia nuttalli and Sigalia carpatica, and the correlation of the zonal boundary with the inoceramid scheme. The Coniacian/Santonian boundary, as defined by the first occurrence of Platyceramus undulatoplicatus (Roemer), falls in the lower part of the Sigalia carpatica Zone. FOs of Costellagerina pilula and typical “pill-box-like” morphotypes of Globotruncana linneiana are a good proxy for the stage boundary.

Carbon and oxygen stable isotopes have been analysed from 45 bulk sediment samples taken through a 40-m section across the Coniacian/Santonian boundary at Olazagutia, Navarra, Spain, a candidate Global Boundary Stratotype section for this stage boundary, and related to key bioevents. Carbon isotope values lie between +2.68 and +3.05‰; oxygen isotope values between −3.12 and −2.26‰, VPDB. Neither carbon nor oxygen isotope curves include significant excursions. Nevertheless, the carbon isotope curve can be correlated precisely with a published carbon isotope curve from southeast England. Within the limits of our sampling resolution (approximately one sample per 22,000 years), correlations based on carbon isotopes and on first and last occurrences of the inoceramid bivalve Platyceramus undulatoplicatus (the primary biomarker for the Coniacian/Santonian boundary) are equally accurate. Minor fluctuations in the oxygen isotope curve may reflect periodic incursions of cooler Atlantic water into the area around Olazagutia.

Detailed qualitative and quantitative studies of the calcareous nannofloral assemblages were carried out on 65 cm across the K/T boundary interval of the Caravaca section. Preservation of nannofloral assemblages is moderate to good. Reworking was identified in the lowermost Danian, but did not essentially influence the rest of the section studied. The nannofloral study shows that most of the Cretaceous taxa disappeared in the “fallout” lamina, a bio-event which is synchronous with the mass extinction of the planktonic foraminifera and with significant geochemical anomalies. Beside these events, a rapid decline of the calcareous nannofossils is recorded in the uppermost 12 cm of the Maastrichtian (about 4 ky prior to the K/T boundary). Such decline becomes more pronounced in the transitional layer, just below the K/T boundary, therefore predating the main extinction event. This pattern is in agreement with other evidences of an unstable ecosystem and inputs of cold-water taxa in this area with typical Tethyan upper Maastrichtian nannofossil assemblages. Two successive blooms, of Thoracosphaera spp., followed by that of Braarudosphaera bigelowii, were identified at the base of the Danian. In the upper part of the studied sequence, nannoflora records are already dominated by survivor as well as by incoming taxa, showing an early pioneer calcareous nannofloral ecosystem about 25 ky after the K/T boundary mass extinction event.

Evidence of physical disruptions caused by the postulated bolide impact at the close of the Maastrichtian is clearly defined in the record of the K/T boundary (KTB) layer from different sites in the Southern Peninsula of Haiti. Lithologic and biostratigraphic record of the KTB layer from the different sites also show varying degrees of mixing, yielding faunal components within a time range consistent with bioevents characteristic of the traditional boundary zone equivalent to the uppermost part of the Abathomphalus mayaroensis Zone, part of the Guembelitria cretacea Zone, and the Parvularugoglobigerina eugubina Zone, respectively. The calcareous nannofloras also show transitional taxa that concur with the foraminiferal data, and are indicative of the Micula murus and M. prinsii Subzones as well as the CP1a, Cruciplacolithus primus Subzone, of the Early Paleocene. The Boundary layer shows variation in thickness with a maximum of 75cm at the Beloc stratotype, and the topmost part of the main tektite layer is coincident with an iridium peak. Geochemical analyses and radiometric dating have also demonstrated that the spherules are tektites (Premo and Izett, 1991) that can be chronologically related to the impact event recorded at Chicxulub, Yucatan, Mexico, 65 million years ago. Most importantly faint primary sedimentary structures within the boundary layer are constant at all outcrops, but discrete spatial differences exist even within short distances. In addition, in the areas adjacent to the stratotype (Platon Piton and Madame Toussaint) a volcanogenic layer occurs below the main tektite layer assigned to the Chicxulub event, and it also shows conspicuous, as well as cryptic, cross-lamination indicative of complex, multiphase, subaqueous flow processes that affected sedimentation of the layers similar to the KTB layer. Such structures are known to characterize oscillatory wave processes that affect cohesionless sediments. Water motion associated with seiche is the only known modern analog of a subaqueous flow that provides a plausible mechanism to explain how various levels of the water column in a large basin can oscillate to develop the structures observed. Because of the magnitude of the bolide impact, “megaseiches” must have developed in the oceans worldwide, and subsequently more localized “megaseiches” developed during major crustal readjustment. These phenomena may thus explain the heterogeneity of patterns and faunal discrepancies observed at KTB sites of different water depths worldwide. The structures represent a record of water movement and resuspension of sediment at different times. As observed in smaller-scale modern seiche, various oscillatory modes controlled the duration and attenuation of the water movement, the magnitude of bottom traction and resuspension that led to complex sedimentary structures and reworking of the microfossils.