Abstract Albian dinosaur tracks from the Monte Grande Formation (Basque–Cantabrian Basin) are described. Sedimentary succession shows seven different facies associations (FAs) with four track-bearing levels (levels 1–4) of a braid delta system. FA 4, a proximal crevasse subdelta, preserves in levels 2 and 3 theropod, possibly sauropod and undetermined dinosaur tracks, as well as Ophiomorpha and Skolithos traces. FA 5, a middle crevasse subdelta, presents undetermined cross-section tracks in levels 1 and 4, besides Ophiomorpha , Skolithos and locally Teichichnus in other layers. Both FAs have the same general ichnoassociation, although with preservational variations. The sedimentary succession represents an area with periods of crevasse subdelta progradation and colonization of opportunistic organisms, and other periods of subdelta abandonment represented by short sedimentary hiatuses in which the water sheet would be shallow or even absent and where dinosaurs would be roaming. Particularly, the traces of levels 2 and 3 represent the same ichnocoenosis constituting two different suites and may be envisaged as penecontemporaneous, produced within a short-term preservational window. This tracksite is one of the scarce Albian dinosaur ichnological records in the southwestern European island palaeoarchipelago and one of the few worldwide localities where Albian dinosaur tracks have been found in deltaic facies.

Abstract Quantitative analysis performed on latest Pliensbachian–early Toarcian calcareous nannofossil assemblages from the Camino section (Basque Cantabrian Basin) allowed their response to the environmental changes recorded during this time interval to be deciphered, characterized by an extinction event. The results were introduced within a principal component analysis and compared with the stable isotope and total organic carbon curves. During the latest Pliensbachian, the Mirabile and the lowermost part of the Semicelatum Ammonite Subzones, Schizosphaerella , Bussonius prinsii , Biscutum finchii , Calcivascularis jansae and Similiscutum avitum , taxa that probably thrived in rather cold waters, dominated the calcareous nannofossil assemblages. Coinciding with warmer and wetter conditions, which probably led to an increase in surface water fertility, recorded slightly below the extinction boundary, the mesotrophic taxa B. novum , L. hauffii and Calyculus spp. were dominant. Nevertheless, T. patulus and C. jansae , which became extinct just below the extinction boundary, show preferences for oligotrophic conditions. Salinities similar to those of modern oceans have been inferred around the extinction boundary, considering the coupling between the abundances of Calyculus spp. and the species richness together with the absence of black shales. After the extinction boundary, nannofossil assemblages were dominated by the deep-dwelling C. crassus and the shallow-dwelling Lotharingius species, interpreted as opportunistic taxa. This work confirms that calcareous nannofossils are a really useful tool for palaeoceanographic and palaeoenvironmental reconstructions, especially in terms of climatic changes.

Abstract In Asón Valley hydrothermal dolomite area (Basque–Cantabrian Basin, northern Spain), an overlapping stepover area between two major basement faults, the Cabuerniga and Ruahermosa transtensional faults, was the location for different scales and types of extensive fractures. This fracture mesh affected the Albian Ranero limestone and was formed in a dilational jog, a regional fluid throughflow area. It acted as pathway for overpressured fluids that controlled the dolomite mineralization in the Ranero massif area. The study of synchronous structural features, fluid flow channelling and dolomitization processes indicated their tectonic control. The fluid circulated and concentrated preferentially in more fractured areas with increased permeability, such as extensional chimneys, creating dolomite bodies. Repeated extensive tectonic activity enhanced fracture porosity, promoting overpressured fluid migration and cyclical dolomitization events. The studied fracture pattern suggests the presence of sinistral transtension during the formation of extensional joint-sets that channellized the mineralizing fluid-flow. A gradation in structural features and dolomite facies and textures is visible from the main Pozalagua fault dolomite body to peripheral dolomite bodies as the Breccia body and Ranero megajoints. These differences could reflect a proximal–distal trend from the main fluid-flow area along the Pozalagua fault to the Ranero megajoints.