Western Pyrenees Research Articles

Geochemical correlation of pyrobitumen fills with host mid-Cretaceous Black Flysch Group (Basque-Cantabrian Basin, western Pyrenees)

Abundant syndepositional pyrobitumen fills occur within Albian hydrothermal vent carbonates of the organic-rich Black Flysch Group in the Basque-Cantabrian Basin, indicating that these carbonates were charged with oil during Albian times. A carbon isotopic study of pyrobitumens and samples of candidate oil generating rocks (Jurassic and Albian host rock units) as well as Carboniferous-sourced condensate was undertaken to test an Albian source hypothesis for the pyrobitumens. On the basis of similar isotopic ratio values, the pyrobitumens show a strong positive correlation with the host Black Flysch Group. This is supported by Stahl-type curves and a Sofer plot, which show that the pyrobitumens best match the host Albian deposits, whereas the Jurassic source rock and the Carboniferous sourced condensate plot separately. This new Albian pyrobitumen-source correlation demonstrates the existence of an oil generating rock unrecognised till now in the Basque-Cantabrian Basin – the mid-Cretaceous Black Flysch Group.

The Geomechanical Height/Radius Ratio Applied to Analysis and Preservation of Neolithic Tumuli, with Examples from Alava (Spain)

The height/radius ratio of a tumulus and the angle of repose for the materials used in its construction permits one to: predict possible construction methods, calculate the path of geometric evolution before and after the current form and compare degrees of preservation. By way of example a Neolithic tumulus is compared with a modern-day one, both made out of identical lithology. Finally, comments are made on h/r values for tumuli and tumuli with dolmens for the ar- chaeological catalogue of Alava, in the Western Pyrenees.

Potholing: Skin and Stone

be treated alongside illnesses of all kinds. But also, caves have always had their other dark and mysterious side, as the lairs of witches and dragons. Some of these rock shelters or caves were assimilated into the Christian tradition and have become sanctuaries, as is the case at Covadonga. Caving, like dermatology, has its own language. Some of the common terms include: stalactites, stalagmites, columns. Others are less well known but easy to interpret: crawl holes, chambers, flowstones, potholes. Some are more exotic: gours, cave pearls, cone karsts, etc. Also the kit and The incident involving the Belgian caver Annette van Houtte in early August last year, in the Navarre region of the western Pyrenees, had enormous repercussions in the media and brought public attention to a hobby both little known and discrete: speleology or caving. This science is, simultaneously, a hobby, a sport, an adventure, and, above all, a passion. Caves may be naturally or artificially formed. The former are more common in areas of limestone rock formed at the bottom of seas in the Mesozoic and Paleozoic eras and pushed up by tectonic forces to form the highest mountain ranges on the planet. Rainwater dissolves the calcium carbonate in the rocks and deposits it again, shaping the most capricious cavities. Spain has a rich limestone heritage, including the Pyrenees and the Picos de Europa, which are both peppered with caves and potholes. Many are extremely well-known: El Soplao in Cantabria, Valporquero in Leon, the Drach cave in Majorca, Las Grutas de las Maravillas in the Onuba mountains of Aracena, or the Nerja caves in Malaga. Some caves were formed by volcanic action, like the famous Los Verdes cave in Lanzarote, and there are caves in granite areas produced by the direct erosion of subterranean rivers, like the Folon system in Pontevedra province, north-western Spain. The conquest and study of caves has no objective other than knowledge itself—geological, topographical and mineralogical—and the personal challenge. Now that people have reached both poles and all the highest peaks in the world, the only unknown territories left for our adventurous spirit to explore and master are the ocean depths and bowels of the earth. Entering a space previously untouched by any human being is a magical, almost mystical, event. The human relationship with caves dates back to prehistory. For thousands of years they were home to our distant ancestors, providing shelter against the cold and inclement weather, and protection from animals and enemy clans. In fact, only a few decades ago, some Spaniards still lived in caves carved out of the rock itself. It is more than likely that, at some point in time, an inhabited cave or rock shelter formed the first rudimentary hospital, in conjunction with huts in surrounding camps where injured hunters could Potholing: Skin and Stone

Ecología y gestión pastoral en el Pirineo. Una perspectiva de medio siglo

Along the last 50 years, we have studied the pyrenean extensive farming system. In spite the transhumant traditional system, after a weakness period is now finishing, the potential productivity of mountain pastures is still important. Moreover, the recent declaration of the “Parque Natural de los Valles Occidentales” (Western Pyrenees, Spain) may help to develop new strategies to save traditional cultures. After following the bibliography about this topic, we emphasized the ecological role of herbivores, specially after a behaviour selection of the herds in order to improve pasture’s quality and management. If we want to maintain nice and productive mountain grasslands, we would also profite “dehesas” and ancient fields around the villages, and the pre-pyrenean farms (“pardinas” in Aragon) as well. A case study (Aisa-Borau valley) is here introduced. Nowadays it’s true we have an important scientific and technical knowledge, but for a recuperation of the grassland system and a training of young shepherds we need a better coordination between Schools and research centers, both together with the aid of the Natural Protected areas.

Cambios en la cubierta vegetal en el Pirineo aragonés en los últimos 50 años

Changes of vegetal cover in the Aragonese western Pyrenees are shown throughout the last 50 years. The evolution is characterized by a generalised revegetation process with an advance of shrubs and forests. The medium and low slo- pes show the most intense revegetation as a consequence of the agricultural aban- donment and the decrease of the livestock pressure. Nevertheless, few vegetation changes are recorded in cultivated lands and the pastures located above timberline. In the analysed period, the most important changes were recorded in the decades of 1960 and 1970 whereas in the decades of 1980 and 1990 the rate of vegetation growth has decreased noticeably. The socioeconomic factors (agricultural abandon- ment, livestock extensification and reforestations) affect the spatial and temporal pat- terns of revegetation. Also the relief has a noticeable influence, mainly elevation and aspect.

Comunidades nidificantes de aves en pastos supraforestales pirenaicos. Su evolución a lo largo del año

Bird density has been studied along areas with different features in supraforest pastures from two locations in Central Western Pyrenees, Aisa and Borau mountain passes (County of Huesca). Censuses, which have been taken all through the year, report on the formation of breeding bird communities and on those which exploit the studied environments during the postbreeding period. A stronger stability is noticeable in those areas which are higher than 2.000 m above sea level. There, breeding species are mostly highlanders and occurs a lack of strong population fluctuations of arthropods that prevents the invasion by consumers during the postbreeding period. Conversely, in lower areas prevail birds from the forest edge or deforested areas over the highland birds, except for the active large rocky places. In these places, highland birds include the Mediterranean highland factor (paleoxeromontanas).

Three‐dimensional gravity and magnetic modeling of crustal indentation and wedging in the western Pyrenees‐Cantabrian Mountains

The complex crustal structure of the boundary zone between the Iberian and European plates, from the western Pyrenees to the Cantabrian Mountains, is probed by three‐dimensional (3‐D) gravity and magnetic modeling constrained by deep seismic profiles. The 3‐D modeling results support the presence of a continuous Iberian crustal root and suggest that the geometry of the orogenic belt that formed in latest Cretaceous‐Tertiary times along the northern margin of Iberia was conditioned by oblique structures separating areas characterized by different tectonic styles. In the western Pyrenees and the Basque‐Cantabrian basin (a thick Mesozoic basin presently incorporated to the Pyrenean‐Cantabrian belt), the relatively narrow thinning of the crust inherited from the Mesozoic rifting stage conditioned a structural style in which portions of the southward indenting European lower crust are interpreted to be back thrusted toward the north and uplifted to shallow depths, promoting the appearance of significant potential field anomalies. In the Basque‐Cantabrian basin, the strongest aeromagnetic anomaly of the whole Iberian Mainland is superimposed on the eastern part of a well‐defined positive gravity anomaly, similar in amplitude and wavelength to those located along the North Pyrenean Zone. These observations suggest that the eastern part of the dense, lower crustal causative body is strongly magnetized and may correspond to a gabbroic cumulate originated in the axis of the ancient Mesozoic rift. To the west, Tertiary compression affected the North Iberian (Cantabrian) passive continental margin, whose geometry and inherited structures conditioned the formation of a double crustal delamination and the uplift of the Cantabrian Mountains.

The Eaux-Bonnes landslide (Western Pyrenees, France): overview of possible triggering factors with emphasis on the role of groundwater

The purpose of this study is to achieve an understanding of the failure mechanisms which caused the Eaux-Bonnes landslide. The geological investigations carried out on the slope of the landslide showed that the sliding mass was cut by numerous faults. The factors controlling the landslide failure were complex, and it is known that neither earthquakes nor heavy precipitation could have triggered the disruption. The groundwater within the solid rock mass has been surveyed, because significant precipitation events during the 2 years preceding the beginning of the paroxysmal phase of the landslide could have led to an increase in pore water pressure along these fractures, thereby triggering the landslide. In order to achieve a full understanding of the failure mechanism, and to identify the origin of the groundwater, a hydrogeochemical survey was carried out over a period of 1 year. The results reveal the existence of high sulphate concentrations in the groundwater originating in springs located at the bottom of the landslide. The sulphate concentrations are correlated with high calcium concentrations, and clearly indicate the presence of gypsum in the vicinity of the lower reaches of the landslide. The presence of gypsum in this area of the Pyrenees suggests that deep groundwater played a role in triggering the landslide.

A structural model for the seismicity of the Arudy (1980) epicentral area (Western Pyrenees, France)

SUMMARY The Western Pyrenees presents a diffuse and moderate (M ≤ 5.7) instrumental seismicity. It nevertheless historically suffered from strong earthquakes (I = IX MSK). The seismic sources of these events are not yet clearly identified. We focus on the Arudy (1980) epicentral area (M = 5.1) and propose here the reactivation of early Cretaceous normal faults of the Iberian margin as a potential source. The late Cretaceous inversion of this basin, first in a left-lateral strike-slip mode and then in a more frontal convergence, resulted in a pop-up geometry. This flower structure attests of the presence of a deep crustal discontinuity. The present-day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode. This reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts, rooted on this discontinuity. These thrusts accommodate the shortening component of the strain. The distribution of the instrumental seismicity fits well the structural model of the Arudy basin. Whatever the compressive regional context, the structural behaviour of the system explains too the extensive stress tensor determined for the Arudy crisis if we interpret it in terms of strain ellipsoid. Indeed numerical modelling has shown that this concomitant activity of strike-slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain. We identify too a 25‐30 km long potential seismic source for the Arudy area. The size of the structure and its potential reactivation in a strike-slip mode suggest that a maximum earthquake magnitude of ∼6.5 could be expected. The extrapolation of this model at the scale of the Western Pyrenees allows to propose other potential sources for major regional historical earthquakes.

Evidence of an abrupt environmental disruption during the mid-Paleocene biotic event (Zumaia section, western Pyrenees)

An abrupt environmental disruption occurred in the photic zone and at the seafloor during the mid-Paleocene biotic event (MPBE). Calcareous nannoplankton, planktic foraminifer, and benthic foraminifer assemblages at Zumaia section (western Pyrenees) underwent a rapid and remarkable transformation. The major calcareous plankton assemblage changes suggest a shift from relatively cooler mesotrophic to warmer, more oligotrophic conditions, indicating a disturbed environment due to the warming of the ocean. Benthic foraminifer assemblages were also significantly affected by the MPBE; diversity of the assemblages and buliminids show net decline and the low food and opportunistic taxa increase in abundance. The reorganization of the planktic ecosystem possibly involved changes in the food flux (type and quantity) to the seafloor, thus triggering changes in the benthic communities. A 1‰ negative δ 13 C shift and a 30% carbonate content decrease are recorded in connection with the biotic event. This suggests that during the MPBE, as in the Paleocene-Eocene Thermal Maximum (PETM), an input of a large mass of isotopically depleted carbon into the ocean and atmosphere could have lowered the deep-sea pH, triggering a rapid shoaling of the lysocline and contributing to greenhouse warming. The MPBE was short lived: according to the counting of limestonemarl couplets, the stratigraphic expression of precession cycles throughout the Zumaia section, the MPBE lasted for ∼52–53 k.y., with the core of the event representing ∼10–11 k.y. The Zumaia section is the first land-based locality in which the MPBE is recognized and described in detail. Due to its expanded character and excellent paleontological record, this section may prove to be a global reference section for the study of this short-lived event.

First comprehensive contribution to medical ethnobotany of Western Pyrenees

BackgroundAn ethnobotanical and medical study was carried out in the Navarre Pyrenees, an area known both for its high biological diversity and its cultural significance.As well as the compilation of an ethnopharmacological catalogue, a quantitative ethnobotanical comparison has been carried out in relation to the outcomes from other studies about the Pyrenees. A review of all drugs used in the area has also been carried out, through a study of the monographs published by the institutions and organizations responsible for the safety and efficacy of medicinal plants (WHO, ESCOP, and the E Commission of the German Department of Health) in order to ascertain the extent to which the Navarre Pyrenees ethnopharmacology has been officially evaluated.MethodsFieldwork was carried out over two years, from November 2004 to December 2006. During that time we interviewed 88 local people in 40 villages. Information was collected using semi-structured ethnobotanical interviews and the data was analyzed using quantitave indexes: Ethnobotonicity Index, Shannon-Wiener's Diversity, Equitability and The Informant Consensus Factor. The official review has been performed using the official monographs published by the WHO, ESCOP and the E Commission of the German Department of Health.ResultsThe ethnobotanical and medical catalogue of the Navarre Pyrenees Area comprises 92 species, of which 39 have been mentioned by at least three interviewees. The quantitative ethnobotany results show lower values than those found in other studies about the Pyrenees; and 57.6% of the Pyrenees medical ethnobotany described does not figure in documents published by the above mentioned institutions.ConclusionThe results show a reduction in the ethnobotanical and medical knowledge in the area of study, when compared to other studies carried out in the Pyrenees. Nevertheless, the use of several species that may be regarded as possible sources for pharmacological studies is reported here such as the bark of Sambucus nigra, the roots of Fragaria vesca, or the leaves of Scrophularia nodosa. These species are not currently approved by the WHO, ESCOP and the E Commission of the German Department of Health, institutions that, apart from encouraging the greater use of plants for medicinal purposes, may help in the design of development plans for these rural areas by validating their traditional medicine.

Bird and Mammal Footprints From the Tertiary of Navarre (Western Pyrenees)

A rich variety of vertebrate footprints is known from a number of Upper Eocene to Lower Miocene localities of Navarre (western Pyrenees). The sediments were deposited in a wide range of depositional environments, from marginal marine to diversified terrestrial. Abundant bird tracks have been found in the coastal deposits of the Upper Eocene Liedena Sandstone of the Yesa and Itzagaondoa areas. Ciconiiformes-like (Leptoptilostipus pyrenaicus) and Charadriiformes-like (Charadriipeda ichnospp.) footprints have been recognized. Mammal ichnites have been discovered in the Oligocene and Lower Miocene deposits of Navarre. Equoid perissodactyl ichnites similar to those of Plagiolophustipus occur in the Oligocene fluviatile rocks of the Mués Sandstone of Olexoa and the Rocaforte Sandstone near Oibar and Sada. Trackways of entelodontids (Entelodontipus) are known in fluviatile-palustrine beds of the Oligocene Mués Sandstone of Olkotz. Additionally, bird (Charadriiformes-like) tracks are known in fluviatile-palustrine floodplain deposits of the Lower Miocene Ujué Formation of Los Arcos. In the same area, the Desoio and Los Arcos outcrops have also yielded perissodactyl trackways of possible Equoidea. Trackways of rhinocerotids (?) and artiodactyls (possibly Pecoripeda) are described from the Lower Miocene (Ramblian) palustrine limestones marginal to the Lerín Formation of Kaparroso and from alluvial fan deposits of the Uncastillo-Perdón Formation of Altzorritz, respectively.

Reassessment of the Early–Middle Eocene biomagnetochronology based on evidence from the Gorrondatxe section (Basque Country, western Pyrenees)

Thirteen Lower–Middle Eocene (Ypresian–Lutetian) successions, including the Gorrondatxe section in the western Pyrenees, show biomagnetostratigraphic correlation schemes that do not agree with the current standard framework. The main discrepancy concerns the position of the boundary between planktonic foraminiferal Zones P9 (=E7, approximately) and P10 (=E8, approximately), which was thought to occur within calcareous nannofossil Subzone CP12a and at the boundary between magnetic polarity Chrons C22n and C21r. However, in the differing correlation scheme the boundary between Zones P9 (=E7) and P10 (=E8) occurs close to the base of Subzone CP13a and to the boundary between Chrons C21n and C20r. An attempt at a new Ypresian–Lutetian boundary biomagnetochronology is made based on data from the Gorrondatxe section, which shows that the boundary between Zones P9 (=E7) and P10 (=E8) is 3.1 Myr younger than hitherto considered. Therefore, the duration of the Early Eocene, most commonly defined according to this planktonic foraminiferal zonal boundary, has generally been underestimated over the last four decades.

A paleomagnetic study of the Basque Arc (Basque-Cantabrian Basin, Western Pyrenees)

The Basque Arc constitutes the northern segment of the Basque-Cantabrian basin, in the western part of the Pyrenees. The main goal of the present study was to find out by means of paleomagnetic analysis if the arched shape of the Basque Arc has a primary origin, due to the development of sedimentary basins related to the opening of the Bay of Biscay or a secondary origin due to rotations about vertical axes. Nine volcanic flows of late Albian to Santonian age (100–83.5 My) were sampled together with 10 sedimentary sites (marls, limestones, calcarenites and sandstones) of lower Jurassic to early Eocene age in order to carry out paleomagnetic and rock-magnetic experiments, 15 paleodirections being obtained. In order to analyse these results together with data from previous studies, the studied area was subdivided into a western, a central and an eastern sector. While inclinations of all three sectors show a similar value, declinations differ. The western sector displays a 37 ± 16° clockwise rotation of its mean paleodeclination, the central sector is not rotated (4 ± 9°) and both sedimentary sites which make up the eastern sector show counter-clockwise rotations (−25 ± 11° and −68 ± 9°). These results suggest that the shape of the Basque Arc does not have a primary origin, but a secondary origin due to rotations about vertical axes as a result of differential shortening related to post-Lutetian compressive tectonics which resulted in the formation of the Pyrenees.

POST-VARISCAN MAFIC DIKES FROM THE LATE OROGENIC COLLAPSE TO THE TETHYAN RIFT: EVIDENCE FROM SARDINIA

Dolerite dikes cut the Lower Paleozoic medium- to high-grade metamorphic basement, the Sardinia-Corsica batholith and the Stephanian - Autunian calcalkaline effusives (1st volcanic episode, according e.g. to Bonin, 1989; Cabanis et al., 1990) with a N-S trend and subvertical dip. Their occurrence is reported from several areas of Sardinia, from the N to the SE. The basic dikes are associated with diorite to rhyolite dikes having trends ranging from E-W to N-S. A late Triassic lamprophyric dike intruded the garnet-staurolite-kyanite micaschists near Mt. Nieddu and has a 40°N direction. Two 40Ar-39Ar age determinations for the dolerite dikes were carried out on amphibole. Ages between 253.8±4.9 and 248±8 Ma (Permian - Early Triassic) probably correspond to the emplacement interval. A continental within-plate geochemical signature, with prevalent tholeiitic to transitional (dolerites) and minor alkalic (lamprophyre) terms, has been determined. The relative LILE and REE enrichment compared with the MORBs and Nd isotopic ratios (4 bulk samples; initial 143Nd/144Nd ratios between 0.512529±0.000025 and 0.513143±0.000023) is consistent with a source in a sub-continental lithospheric mantle. The remarkable compositional and isotopic variability can be explained by the partial melting of a heterogeneous source. Crustal contamination variably affects some transitional dikes; the host Arzachena monzogranite probably represents the major contaminant source. On the whole, the geochemical data support an anorogenic geochemical affinity, in accordance with the extensional regional tectonics, for the Permo-Triassic dikes in Sardinia. The E-W emplacement patterns correspond to the major fractures and primarily R and RI structures associated with the late Variscan transcurrent-extensional E-W faults. The N-S emplacement trend is consistently associated with a generalized E-W extension of the Sardinian crust: in a predrift restoration it coincides with the patterns of extension between the European and Insubric crust at the beginning of the Tethyan rift. In Sardinia, the lamprophyre dike is significantly younger than the late Variscan alkaline volcanites and dikes of the rest of the Mediterranean domain (e.g. Eastern Provence: 278-264 Ma, 40Ar/39Ar isotope dating on feldspar from rhyolites and on plagioclase from mafic flow, Zheng et al., 1992; Western Pyrenean Axial Zone: 271-266 Ma, K-Ar isotope dating on kaersutite phenocrysts from mafic dikes, Debon and Zimmermann, 1993), in accordance with the diachronism of both the first and second volcanic episodes in different areas of the Mediterranean domain. The overlap between the calc-alkaline events and the volcanic and sub-volcanic alkalic event, is not exclusive to Sardinia and Corsica (e.g. the Pyrenees and Pan-African orogen).

“Lombardi à Arudy !” Images de l’exploitation forestière dans les Pyrénées françaises de 1916 à 1975

En 1916, Aldo Lombardi (1892-1965), fils d’un scieur du Tessin, et son ami Morello achètent une scierie dans les Pyrénées-Orientales et y exploitent les sapinières à l’aide d’un tricâble. En 1920, pour les besoins d’une coupe, la scierie est transportée dans les Hautes-Pyrénées puis, pour réaliser un contrat d’un million de m3 d’une coupe intercommunale à Arudy (Pyrénées-Atlantiques) pour, étant sans cesse techniquement améliorée, mettre en oeuvre les produits de l’essentiel des coupes du Béarn durant près de 50 ans. Employant jusqu’à 1 000 salariés en 1938, l’entreprise Lombardi & Morello est remarquablement intégrée, de l’exploitation par tricâbles — dont elle était le leader français — à la réalisation, durant la dernière guerre, de baraquements pré-assemblés pour l’armée. Quand, en 1965, Jacques Lombardi (1929-2002) succède seul à son père, il devient un des premiers à réaliser des chalets préfabriqués et des charpentes en fermettes. Les très forts coûts de récolte des bois de montagne et la baisse des cours des résineux entraînent la fermeture de l’entreprise dans les années 1990. Ses exploitations, où les routes forestières et les pistes remplaceront complètement les tricâbles à partir de 1970, marquent toujours nettement les peuplements forestiers des reliefs difficiles des Pyrénées occidentales.

La période 19000-14000 BP dans le bassin de l'Èbre

In Aragon, the archaeological sites of Chaves and Fuente del Trucho present lithic industries (notched points) that allow us to envisage contacts within the Mediterranean Solutrean and the Salpetrian of Languedoc around 19 700 BP. On the other hand, the Western Pyrenees (Navarre) clearly presents influences from the Aquitaine and Cantabrian zones during the Final Solutrean. The cave of Abauntz (level f) has provided evidence for these relations with its flat retouched notched points. The relations with sites of the northern slope seem to point to the Velate/ Otsondo mountain pass, used throughout history. For the Lower Magdalenian, the sites are concentrated in the valley of the Cinca, on the south pre-Pyrenees slope. The sites of Forcas I (levels 17 to 15) and Alonsé (level m), dated around 15 000-14 500 BP, allow us to establish comparisons with Catalonian sites, following the Cinca-Segre axis (Parco, Montlleó), then through Cerdagne, towards Roussillon via the Têt. That would correspond to the northern communication route, the most important, ever since the Upper Solutrean. Furthermore, the radiometric data as well as the industries obtained allow us to confirm prehistoric human occupations on the buttresses of the Iberian Mountain Chain (cave of El Gato and shelters of Vergara, Alejandre and Toros). All these sites seem to mark the passageways of some tributaries of the right bank of the Ebro, such as the Jalón river towards the Meseta and the Guadalope river towards the Spanish Levantine coast.

Influence of site characteristics and thinning intensity on litterfall production in two Pinus sylvestris L. forests in the western Pyrenees

Litterfall production was studied for 30 months in two contrasting Pinus sylvestris L. stands in the western Pyrenees managed under two low thinning intensities: Aspurz (625 m a.s.l., Mediterranean climate) and Garde (1335 m a.s.l., continental climate). Nine 0.12 ha plots per site were set up with three treatments three times repeated: removal of 0% (not thinned, P0), 20% (P20) and 30% (P30) of initial basal area. Total litterfall was significantly higher in Aspurz (5533 kg ha −1 year −1) than in Garde (3986 kg ha −1 year −1). Maximum annual needle fall values were in September (Aspurz) or October (Aspurz and Garde), and second order peaks were in June or July at both sites. In both sites, cones and other pine organs (e.g., seeds, inflorescences) showed the same seasonal patterns, while bark and branches, affected by sporadic occurrence of storms or snowfalls, followed no clear pattern. Low thinning effects were site-dependent (e.g., needles; Aspurz, P0 > (P20 = P30); Garde, P0 > P20 > P30) due to between site differences in stand structure. Thus, more dominant and codominant trees (i.e., high litterfall producers) were felled in P30 than in P20 in Garde relative to Aspurz. Needle fall in Aspurz showed unique significant positive correlations with days of dryness and moisture deficit, probably reflecting its Mediterranean climate. However, relative to Aspurz, Garde exhibited significant retarded responses of total litterfall and needle fall to changes in air temperature, soil temperature and soil moisture suggesting in part that Garde's needles are more resistant to climatic stress. Furthermore, litterfall was better predicted in Aspurz than in Garde, partly due to the greater influence of sporadic windstorms and snowstorms in Garde. It appears that in these Pyrenean P. sylvestris stands, site-dependent climatic variables have an important control on litterfall. At the local scale, however, stand structure influences effects of thinning on litterfall.

Fire and human activities on the Pyrenees mountain (Western Pyrenees and Eastern Pyrenees), inferred from pedoanthracological, palynological, micro-charcoal and archaeological data: An interdisciplinarity approach

In this communication we present new results about relation between fire, human activities and vegetation dynamics provided by interdisciplinary investigations carried out in the Palaeoenvironment and human activities on the Basque mountain program led by Galop since 2001 and in the Cerdagne’s program led by Rendu since 2002. This research field is located precisely in massif of Iraty (Western Pyrenees) and in the Enveig’s slope (Eastern Pyrenees). On the Basque mountain, macro-charcoal, micro-charcoal and pollen analysis show important phases of fire in relation to agro-sylvo-pastoral activities and confirm the use of slash and burns cultivation since Neolithic (Vanniere et al. 2001). These results fit well with palaeoenvironmental and archaeological data obtained in the same area. Strong human impact on the forest cover occurred during Bronze Age as it has been demonstrated by numerous contemporaneous burial mounds found and dated on the slopes (Marembert, 2000; Rendu, 2002; Carozza et al., 2005). Current landscape essentially consists of pastures with small stands of Fagus forest. Some isolated old oaks are principally situated near pastoral farms. Pedoanthracological analysis carried out in this area give informations about agro-pastoral activities and their consequences on Quercus – beech forest since Bronze Age period. Radiocarbon dated charcoals found in the slopes soils indicate fire. This induces clearance of the oak forest due to human activities. This progressive deforestation seems to have favoured Fagus expansion in the forest cover after 4000 BP. On the Enveig’s slope, the same interdisciplinarity approach shows a link between palaeoenvironment (Galop, 1998) and archaeological data (Rendu, 2003) and summer farming settlements. This revealed that occupation and grazing activities have started during Neolithic and have increased during Bronze Age period. Human impact appears to be the main factor for local extinction of Abies alba. It is interesting to compare micro-charcoal data and cumul dates of macro-charcoals to show that anthropic phases coincide with fire history both in Western and Eastern Pyrenees. This interdisciplinary approach helps in understanding the intensity of fires and their consequences on the dynamics of vegetation. Methodologicaly, pedoanthracoanalysis provide informations that confirm palynological and micro-charcoal results, with more precise spatial reconstructions. Laboratoire GEODE UMR5602, 5 allees A. Machado, Maison de la Recherche, 31058 Toulouse le Mirail cedex 9, France, Tel. : +33 (0)561 50 25 99, Fax : +33 (0)561 50 42 75, bal@univ-tlse2.fr. Laboratoire de Chrono-EcologieUMR 6565 CNRS – Universite de Franche-Comte 16 route de Gray 25030 Besancon cedex France, Tel. : +33 (0) 381 66 63 95, boris.vanniere@univ-fcomte.fr Laboratoire de Chrono-EcologieUMR 6565 CNRS – Universite de Franche-Comte 27, Chemin du Rayat, F-31600 MURET, France, Tel. : +33 (0) 561 50 25 99, Fax : +33 (0)561 50 42 75, didier.galop@univ-fcomte.fr. Laboratoire FRAMESPA, 5 allees A. Machado, Maison de la Recherche, 31058 Toulouse le Mirail cedex 9, France, Tel. : +33 (0) 561 50 36 77, christine.rendu@wanadoo.fr.

A point‐sourced calciclastic submarine fan complex (Eocene Anotz Formation, western Pyrenees): facies architecture, evolution and controlling factors

AbstractA complete transect of a fossil carbonate ramp slope has been reconstructed using outcrop data from the Lower‐Middle Eocene Anotz Formation in the western Pyrenees. The Anotz Formation contains four calciclastic (mostly bioclastic) members encased within hemipelagic marl/limestone alternations, each calciclastic member representing a submarine fan system. Individual fans are composed of a gullied upper slope, a leveed feeder channel, a channelized lobe area, an unconfined lobe zone and a peripheral lobe fringe that grades downcurrent into basinal deposits. Quantitative data on the dimensions and degree of lateral continuity and vertical connectivity of the Anotz calciclastic fan elements are presented. These data provide information for a better understanding of the intrinsic nature of calciclastic submarine fans and to model their reservoir potential. The long‐term evolution of the Anotz carbonate slope was generally progradational, as evidenced by the four discrete episodes of calciclastic‐fan development. The location of the fans was controlled by the synsedimentary tectonic activity of the Pamplona fault, which created a slope valley along which the reworked shallow‐water calciclastic sediments were funnelled. In addition, episodic basinward tilting of the shallow‐water carbonate ramp, linked to the development of the South Pyrenean foreland basin, switched on and off the process of calciclastic resedimentation and determined the growth or abandonment of the fan systems.