Between two worlds: Cova Eirós and the Middle-Upper Palaeolithic transition in NW Iberia

Iberia, a natural cul-de-sac peninsula, plays a major role in the study of the Neanderthals demise and its eventual relationship with the spread of Anatomically Modern Humans (AMH) in Europe. The site of Cova Eirós (Galicia, Spain), located in NW Iberia, contains Middle and Upper Palaeolithic levels, based on the cultural remains recovered at the site. No human remains directly associated with those levels were discovered yet. The available radiocarbon dates from the levels 2 (c. 35 ka cal BP, Early Upper Paleolithic) and 3 (c. 41 ka cal BP, Late Middle Paleolithic), point to a late survival of Neanderthal groups in North Iberia and to a relative quick arrival of the AMH, c. 35-36 ka cal BP, with respect to other territories of the Iberian Peninsula. The archaeological record shows clear differences between the Middle and the Upper Palaeolithic occupations, regarding raw-material acquisition, lithic technology and subsistence strategies. The location of Cova Eirós in the westernmost margin of the Cantabrian Rim and in the Atlantic Façade, makes this site a key place to understand the spread of the first AMH and the progressive demise of Neanderthal populations.

Radial anisotropy and S-wave velocity depict the internal to external zones transition within the Variscan orogen (NW Iberia)

The cross-correlation of ambient noise records registered by seismic networks has proven to be a valuable tool to obtain new insights into the crustal structure at different scales. Based on 2- to 14-s-period Rayleigh and Love dispersion data extracted from the seismic ambient noise recorded by 20 three-component broadband stations belonging to two different temporary experiments, we present the first i) upper crustal (1–14 km) high-resolution shear wave velocity and ii) radial anisotropy variation models of the continental crust in NW Iberia. The area of study represents one of the best exposed cross-sections along the Variscan orogen of western Europe, showing the transition between the external eastern zones towards the internal areas in the west. Both the 2-D maps and an E-W transect reveal a close correspondence with the main geological domains of the Variscan orogen. The foreland-fold and thrust-belt of the orogen, the Cantabrian Zone, is revealed by a zone of relatively low shear wave velocities (2.3–3.0 km/s), while the internal zones generally display higher homogeneous velocities (> 3.1 km/s). The boundary between both zones is clearly delineated in the models, depicting the arcuate shape of the orogen grain. The velocity patterns also reveal variations of the bulk properties of the rocks that can be linked to major Variscan structures, such as the basal detachment of the Cantabrian Zone or the stack of nappes involving pre-Variscan basement; or sedimentary features such as the presence of thick syn-orogenic siliciclastic wedges. Overall, the radial anisotropy magnitude varies between −5 and 15 % and increases with depth. The depth pattern suggests that the alignment of cracks is the main source of anisotropy at < 8 km depths, although the intrinsic anisotropy seems to be significant in the West-Asturian Leonese Zone, the low-grade slate belt adjacent to the Cantabrian Zone. At depths > 8 km, widespread high and positive radial anisotropies are observed, caused by the presence of subhorizontal alignments of grains and minerals in relation to the internal deformation of rocks either during the Variscan orogeny or prior to it.

Two-step obduction of the Porvenir serpentinites: A cryptic Devonian suture in SW Iberian Massif (Ossa-Morena Complex)

ABSTRACT The Porvenir serpentinites are an ∼600-m-thick body of meta-peridotites exposed in SW Iberia (Variscan Orogen). The serpentinites occur as a horse within a Carboniferous, out-of-sequence thrust system (Espiel thrust). This thrust juxtaposes the serpentinites and peri-Gondwanan strata onto younger peri-Gondwanan strata, with the serpentinites occupying an intermediate position. Reconstruction of the pre-Espiel thrust structure results in a vertical juxtaposition of terranes: Cambrian strata below, Porvenir serpentinites in the middle, and the strata at the footwall to the Espiel thrust culminating the tectonic pile. The reconstructed tectonic pile accounts for yet another major thrusting event, since a section of upper mantle (Porvenir serpentinites) was sandwiched between two tectonic slices of continental crust (a suture zone sensu lato). The primary lower plate to the suture is now overlying the upper plate due to the Espiel thrust. Lochkovian strata in the upper plate and the Devonian, NE-verging folds in the lower plate suggest SW-directed accretion of the lower plate during the Devonian, i.e., Laurussia-directed underthrusting for the closure of a Devonian intra-Gondwana basin. Obduction of the Porvenir serpentinites was a two-step process: one connected to the development of a Devonian suture zone, and another related to out-of-sequence thrusting that cut the suture zone and brought upward a tectonic slice of upper mantle rocks hosted in that suture. The primary Laurussia-dipping geometry inferred for this partially obducted suture zone fits the geometry, kinematics, and timing of the Late Devonian suture zone exposed in NW Iberia and may represent the continuation of such suture into SW Iberia.

Management of Soil Fertility and Agricultural Intensification in NW Iberia, 1750–1900

This article describes agricultural practices of fertilization in the NW of the Iberian Peninsula between 1750 and 1900, where a leguminous plant called gorse (Ulex Europaeus) was used as bedding for livestock in order to produce manure. During the period examined, this whole region experienced a process of agricultural intensification which resulted in a net loss of nutrients in the soil. Peasants dealt with the increasing nutrient requirements by adapting land and livestock management in order to produce more manure during the second half of the 20th century. However, this was done at the expense of nutrient reserves in extensively managed areas, all of which resulted in an unsustainable agricultural pattern. Our data also suggest that the context of nutrient scarcity could be related to changes in the migration pattern, which started to be more intense after 1850 and preferred distant destinations (America), thus switching from seasonal to permanent stays.

Landscapes of the ‘Coast of Death’: dolmen topographies of NW Iberia

This paper investigates the dolmen landscapes of Neolithic communities found within Costa da Morte (Coast of Death), Galicia. Its goal is to uncover whether or not the megalithic monuments of a particular and coherent area of the south-eastern side of the Atlantic Façade are situated in relation to complex locational variables. In particular, in this paper, we explore the entirety of their surrounding topography. For the very first time, we were able to demonstrate that very specific natural landscapes surrounding the dolmens of this region in Iberia were likely selectively drawn upon, expanding our understanding of the Neolithic of this area and the people's relationship with their natural world.