Predicting travel times and transport characterization in karst conduits by analyzing tracer-breakthrough curves, , Morales Tomas, De Valderrama Inigo, Uriarte Jesus A. , Antiguedad Inaki, Olazar Martin,

SummaryThis paper analyzes data obtained in 26 tracer tests carried out in 11 karstic connections following solutional conduits in karst aquifers in the Basque Country. These conduits are preferential drainage pathways in these aquifers and so they confer a marked anisotropy and high vulnerability to them. Consequently, their consideration in protection and management studies and projects is a priority.The connections studied cover a wide hydrogeological spectrum (a wide range of sizes, slopes, geomorphic and hydrologic types) and the tests have been carried out at different hydrodynamic states. It is noteworthy that they all follow a similar trend, which has allowed for the development of a statistical approximation for the treatment of the whole information.Relationships have been established involving velocity, solute time of arrival, attenuation of peak concentration and time of passage of tracer cloud. These relationships are a valuable tool for management and supporting decision-making and allow for making estimates in connections in which the information available was scarce. This information is especially useful, given that the complexity of transport in karst conduits gives way to important deviations between real data (empirical observations) and the data obtained by simple approaches based on the Fickian-type diffusion equation

Application of a solute transport model under variable velocity conditions in a conduit flow aquifer: Olalde karst system, Basque Country, Spain, 1997, Morales Juber, Olazar Mart, Arandes Jose Mar, Zafra Pedro, Antig_ Edad, Basauri F. ,

Aroca (domaine marin côtier, Pays basque, France) : un karst continental ennoyé par les transgressions maritimes quaternaires, 2007, Vanara Nathalie , Perre Alain, Pernet Marc, Latapie Serge, Jaillet Stéphane, Martine Olivier

AROCA (LITTORAL, BASQUE COUNTRY, FRANCE): A CONTINENTAL KARST DROWNED BY QUATERNARY MARITIME TRANSGRESSIONS. The rocky formations in shallow areas of the Atlantic coast are hardly known. Studies are rare because of the difficulties of direct observation (diving in always agitated, troubled water, depth between – 20 and – 40 m). Our first step was to make a detailed topography of a submarine plateau named Aroca, 4 km off Socoa harbour (bay of Saint-Jean-de-Luz). This plateau was already known for having a large variety of forms within a small surface (150 x 100 m). We gave names to most remarquable formations and defined five main characteristic zones: - in the exokarstic domain 1/ a top surface with channels, 2/ a dismantled surface with pinnacles; - in the endokarstic domain 3/ caves, galleries, arches; - at the limits 4/ three inclined plans, west, north and east, 5/ a cliff to the south. A typology of forms shows a predominance of ablation reliefs: aplanation, over-deepened channels, covered rooms and galleries, arches, residual pinnacles. Deposit accumulations regroup chaotic breakdown blocks, pebble accumulations and sand covers. Statement of explanations requires recognition of the nature and age of the outcrops and succession of erosional agents during the Pleistocene. Rocks are dated from Ypresien (limestones) to Bartonian (marls). Continental erosion during sea regressions is responsible of caracteristic landforms and deposits; for example wall banks, allochthonous pebbles… The currently active marine erosion during sea transgressions is due to storms, tide, dissolution, biochemical action (lithophages) and gravity. We propose a paleogeographic reconstitution. After an essentially calcareous sedimentation in Eocene and an essentially marly sedimentation in Oligocene, the sea recedes during Miocene. From then, the platform, henceforward above the water, is subject to meteoric erosion. In Pliocene, evolution of the massif is isovolumic (under a marly cover and with a low hydraulic gradient). During the lower and middle Pleistocene, the erosion of the marly cover goes on. During the upper Pleistocene, the wurmian (–18000 BP) marine regression allows entrenchment of the hydrographic system thanks to an increase of hydraulic gradients (classic functional karst). From 15000 years onwards, a general transgression of sea level happens by successive steps. During the Boreal, a break in transgression allows the formation of a paleo-shore at –20 to –30 m, inducing a peneplanation phase in the tidal or infratidal zone. From 7500 BP onwards, a a rapid transgression from –23 to –8, then a slower one from –8 to the present level stops karstification on the massif. At present, only marine abrasion is active and tends to obliterate the previously built landforms.