Juan A. Morales

Evolution and facies architecture of the mesotidal Guadiana River delta (S.W. Spain-Portugal)

Abstract The Guadiana River estuary and delta is one of the most important mesotidal fluvio-marine systems of the southwestern Iberian Peninsula. The river mouth was formed as a narrow channel excavated by fluvial incision during the Pleistocene lowstand and then flooded 6500 yr ago, during the Flandrian transgression (Holocene). The estuary is in an advanced state of sediment infilling in its proximal part, due to its narrow morphology which prevents passage of sediment through to the open coast. Consequently, sediment is accumulating in the river mouth, causing progradation as response of the interaction between coastal and fluvial processes. Sedimentation is controlled by the interaction of sediment load delivered by the Guadiana River and the active longshore current which also supplies sand eroded from barrier islands and friable cliffs in the Portuguese Algarve to the west. Tidal range is mesotidal (2.0 m) and mean significant wave height is 0.6 m with an average period of 3.6 s. Morphological differences exist between the two sides of the river mouth: the western side has a large spit separated from the mainland by a marsh and the eastern side shows an array of old barrier islands separated by salt marsh areas. A vibracore study allows us to distinguish 12 different depositional facies in the system: fluvial delta, tidal inlet, flood-tidal delta, washover, beach, dune, estuarine channel, lagoon, tidal creek, channel margin, tidal flat and salt marsh. Furthermore, a different architectural scheme of these facies is present on each side. To the east, there is a longitudinal repetition of the sandy facies corresponding to the barrier islands; on the west side, there is a transverse growth of a single spit containing eolian dunes. These differences result from asymmetric interaction between the tidal and fluvial currents at the rivers mouth and the waves and tidal currents of the open coastal zone.

A description of how metal pollution occurs in the Tinto-Odiel rias (Huelva-Spain) through the application of cluster analysis

In the last few decades, the study of space-time distribution and variations of heavy metals in estuaries has been extensively studied as an environmental indicator. In the case described here, the combination of acid water from mines, industrial effluents and sea water plays a determining role in the evolutionary process of the chemical makeup of the water in the estuary of the Tinto and Odiel Rivers, located in the southwest of the Iberian Peninsula. Based on the statistical treatment of the data from the analysis of the water samples from this system, which has been affected by processes of industrial and mining pollution, the 16 variables analyzed can be grouped into two large families. Each family presents high, positive Pearson r values that suggest common origins (fluvial or sea) for the pollutants present in the water analyzed and allow their subsequent contrast through cluster analysis.

EVOLUTION OF ESTUARINE FACIES IN A TIDAL CHANNEL ENVIRONMENT, SW SPAIN : EVIDENCE FOR A CHANGE FROM TIDE- TO WAVE-DOMINATION

Abstract The transition from tide- to wave-dominated environments is documented in Holocene estuaries along the mesotidal coast of Huelva, southwestern Spain. This transition is a consequence of the decreasing tidal prism caused by estuarine siltation, a process favoured by the inherited morphology of the prior fluvial valleys. The Domingo-Rubio tidal channel is a small estuary adjacent to the mouth of two wave-dominated estuaries along the coast of Huelva. Coring and vibracoring of both surficial and subsurface sediments allow the distinction of six lithofacies that form five depositional environments: (1) salt marsh; (2) active channel-margin; (3) washover-fan; (4) tidal channel; and (5) estuarine channel. The facies architecture reveals the infilling process of the tidal channel due to the interaction of both waves and tides. Wave activity is registered in the elongation of the spit, whereas tidal action produces facies associations characteristic of tide-dominated estuaries. The recent history of this estuary records three successive stages: (1) an initial tide-dominated open marine environment; beginning at 3090 ± 60 years B.P., with strong tidal currents in very energetic channels displaying a straight-meandering-straight morphology; (2) a wave-dominated period during which waves transport sand into the inner estuary and also along the mouth spit at about 2500 years B.P.; and (3) a second tide-dominated stage from 300 ± 80 years B.P. onward, during which weaker tidal currents distribute the sediment. Four factors controlled the transition from tide to wave domination: (1) the relief formed during deposition; (2) the decreasing tidal prism; (3) the inner facies distribution versus those of the outlet; and (4) the seaward spit elongation of adjacent estuaries.

Evolution of beach–dune fields systems following the construction of jetties in estuarine mouths (Cantabrian coast, NW Spain)

Abstract The morphology of many Spanish estuarine mouths has been modified over recent decades to improve access to the harbours located inside. The normal practice has been the construction of jetties along one or both sides of the mouth to improve the flow though the main estuarine channel and thereby prevent the formation of bars in the main channel bed and ebb-tidal delta lobes or mouth bars in the mouths. The new wave refraction/diffraction dynamics created by these structures induces a strong modification of the beach–dune systems. In the zones adjacent to the jetties, a rapid migration occurs until the beach profile and the associated dune field stabilise, which occurs when the confined space is unable to retain more sediment. This process may include the reworking of outer sandy bottoms and the generation of new stabilised bars. A portion of the sand used by waves to form this accretion is supplied by erosive processes occurring during the same period on the beaches and dune fronts located in areas further away from the jetties, which in many cases are heavily used. The aim of this paper was to analyse the accretion geometries and rates of beach–dune systems in several estuaries that drain into the Cantabrian coast and the subsequent erosion in the outer dune belt, testing a conceptual model formulated to explain the factors that determine the beach–dune response to human actions. The methodology applied can be exportable to other regions to facilitate the prediction of anthropic effects from harbour development and coastal management policies and the subsequent conservation of these environments.

Sedimentary Characteristics of the Holocene Tsunamigenic Deposits in the Coastal Systems of the Cadiz Gulf (Spain)

Juan A. Morales1, Jose M. Gutierrez Mas2, Jose Borrego1 and Antonio Rodriguez-Ramirez3 1Departamento de Geologia. Facultad de Ciencias Experimentales. Universidad de Huelva. Campus Universitario del Carmen, s/n. 21007 Huelva. 2Departamento de Ciencias de la Tierra. Facultad de Ciencias del Mar y Ambientales. Universidad de Cadiz. Campus Universitario Rio San Pedro, s/n. Puerto Real (Cadiz). 3Departamento de Geodinamica y Paleontologia. Facultad de Ciencias Experimentales. Universidad de Huelva. Campus Universitario del Carmen, s/n. 21007 Huelva. Spain

Reply to the comment on “Formation of Chenier plain of the Doñana marshland (SW Spain): Observations and geomorphic model” by A. Rodríguez-Ramírez and C.M. Yáñez-Camacho [Marine Geology 254 (2008) 187–196]

article i nfo It is paradoxical that work in question (Rodriguez-Ramirez and Yanez-Camacho, 2008) has started a debate in the scientific community about the values of the reservoir effect used in the 14

Estuaries of the Huelva Coast: Odiel and Tinto Estuaries (SW Spain)

The estuary of the Odiel and Tinto rivers is located in the southwest of the Iberian Peninsula on the western Gulf of Cadiz (Atlantic Ocean). The Huelva estuary is constituted by the common mouth of the Odiel and Tinto Rivers in a “Y” shape oriented in a N-S direction across 35 km long incised valley. This estuary was generated after the Flandrian Transgression (Holocene), which signified the marine inundation of the main fluvial valleys incised by the rivers during the last Pleistocene lowstand. It extends along the south-western coastal margin of the Guadalquivir sedimentary basin that was incised on Cenozoic non-consolidated sediments during the late Pleistocene and early Holocene when sea level was located up to 100 m below the present position. This estuary is presently completely filled with sediments and has started to prograde to build a delta. The fluvial basin of both rivers is seriously affected by acid mine drainage, so this estuary have a induces important changes in the chemical characteristics of the water, suspended particulate matter (SPM) and sediments.

Beaches of Huelva

The Huelva Coast forms the littoral sector of the SW Iberian Peninsula which extends from the mouth of the Guadiana River, on the border with Portugal, to the mouth of the Guadalquivir River. From a physiographic point of view, the Huelva Coast can be considered a linear, low and sandy coast formed by long beaches, although it could be divided in different sectors according to its topographic configuration and distribution of sedimentary environments.

The Guadiana River Delta

The Guadiana Estuary is a good example of rock bounded estuary which consists of a single narrow estuarine channel with a meandering morphology imposed by faults systems affecting the hard geology of the substrate. Only along the last kilometers of the estuarine channel, the valley opens when Cenozoic Guadalquivir Basin formations appear. In this area, the Guadiana develops a prograding coastal system constituted by successive sandy barriers separated by salt marshes which configure a wave dominated delta. This progradation is possible thanks an interaction of the coastal agents which enhanced the silting in addition to a good availability of sediments. This chapter explains an explanation of the dynamic functioning of the open coastal environment, so as the resulting facies model.

Future Perspectives of the Spanish Coast

Presently, there is a high degree of knowledge about the coastal dynamics of many segments of the coast. The highlights of the functioning of wind, waves, tides and currents in each one of the sectors composing the Spanish coast have been studied and described. The main geomorphologic and sedimentary features of, so as the depositional or erosional trends or each coastal track are also defined. National, regional and local administrations have in their hands the tools to develop a correct Integrated Coastal Zone Management in each one of these coastal tracks. This is vital in Spain, especially, take into account that a big part of the Spanish economy is based in the tourism of sun and beaches. Nowadays, the present coastline suffers the errors committed by the coastal managers in the past. For that, the present Integrated Coastal Zone Management along the Spanish coasts represent an exciting challenge for the competing administrations, since today the entire Coast is public and protected by laws, but with a big responsibility, because now all the scientific knowledge is available for the coastal managers.