Geomorfología litoral y significación de las variacones del nivel del mar

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Análisis de secuencias de islas barrera pleistocenas en relación con variaciones del nivel del mar, laguna de La Mata (Alicante)

En la laguna de La Mata (Alicante) se estudia un complejo de cordones litorales pleistocenos que forman el cierre de la actual laguna. Se analizan las secuencias resultantes y los posibles indicadores de variaciones del nivel del mar. Asimismo se interpretan estos depósitos en base a una curva aparente de tendencias del nivel del mar, obtenida con la suma de las componentes eustáticas cíclicas y la componente relativa debida al factor tectónico aplicado. [ABSTRACT] A complex of Pleistocene coastal barriers is studied in La Mata lagoon (Alicante). The resuting sequences are analyzed in order to establish indicators 0f sea level changes. These deposits can be correlated with an apparent curve of sea level tendencies obtained with the sum of the cyclic eustatic component and the relative component due to the tectonic factor applied

Fan-surface dynamics and biogenic calcrete development: Interactions during ultimate phases of fan evolution in the semiarid SE Spain (Murcia)

Pleistocene alluvial fan surfaces of the Campo de Cartagena–Mar Menor Basin, Murcia, SE Spain. are capped by thick mature calcretes. Calcrete profiles consist mainly of six different horizons: prismatic, chalky, nodular, massive, laminar and coated-gravels. Petrographic study of the calcretes has shown the occurrence of features such as alveolar septal structures, calcified filaments, coated grains, spherulites, calcified root cells and calcispheres that indicate the biogenic origin of the calcretes, mainly induced by plant root related microbial activity. The calcretes studied were formed initially in the soil and represented the K horizon. Development of the calcrete profiles took place in six main stages and was driven by multiple phases of soil formation, erosion and reworking. The relationships between these processes caused the formation of different calcrete profiles in proximal and distal fan areas. In the distal areas, which are controlled by limited distal fan aggradation, episodic sediment input, buried previously developed calcretes and generated new space for calcrete growth by plants growing in the overlying unconsolidated materials. This allowed the renewal of calcrete formation and it led to the development of complex composite profiles which are thicker than in proximal areas, where surface stabilisation andror dissection enabled calcrete reworking and brecciation. These processes of erosion, sedimentation, reworking and renewed calcrete formation initiated by vegetation were repeated through time. They explain the complex macro- and microstructures of these calcretes and indicate that calcrete development, even reaching mature stages, can start before the fan surface is completely abandoned, but it requires episodic sedimentation. Eventually, distal fan aggradation and continuous calcrete development throughout the entire fan surface, led to the ultimate fan surface induration, controlling subsequent landscape evolution. So, fan surface calcretes cannot be envisaged as simple top-surface carbonate accumulations, but as complex feedback systems in which pedogenic, biogenic and sedimentary processes interact in response to the evolving fan-surface dynamics during the terminal phases of fan development in semiarid environments. q1998 Elsevier Science B.V. All rights reserved

Depositional history of estuarine infill during the last postglacial transgression (Gulf of Cadiz, Southern Spain)

The Late Pleistocene and Holocene evolution of the estuaries in the Gulf of Cadiz is interpreted for the first time using drill cores, logs, trenches, and 38 new radiocarbon data, and the results compared with the shelf. The Odiel, Tinto and Guadalete Rivers deposited conglomerates during a highstand that did not reach the present sea level dated at ca. 25–30 ka (Isotopic Stage (IS) 3), corresponding to a relatively humid period in the area. Rivers incised these coarse-grained deposits during the last main lowstand at ca. 18 ka, when sea level dropped to -- 120 m and the coastline lay 14 km seawards from the present. The erosional surface is a sequence boundary and the flooding surface of the postglacial eustatic rise, overlain by the valley fill deposits of the transgressive and highstand phases of the last fourth- and fifth-order depositional sequences recognised in the shelf. The first marine influence in the estuaries during the transgression occurs at -25/-30 m at. ca. 10,000 years BP. According to fossil assemblages, the transgressed basins changed from brackish to more open marine as the sea rose until ca. 6500 years BP, when it reached the maximum flooding and the sandy estuarine barriers ceased to retrograde toward the muddy central basins. Then, the rate of eustatic rise decreased drastically, and the estuarine filling followed a two-fold pattern governed by the progressive change from vertical accretion to lateral (centripetal) progradation. At ca. 4000 years BP the fluvial input surpassed the already negligible rate of rise, causing partial emergence of tidal flats and spit barriers in the largely filled estuarine basins. Prevalence of coastal progradation upon vertical accretion at ca. 2400 years BP caused accelerated expansion of tidal flats and rapid growth of the sandy barriers. Further changes since the 16th century reflect widespread anthropic impacts. q2000 Elsevier Science B.V. All rights reserved

La “Ruta de las huellas fósiles” (Monsagro, Salamanca): un ejemplo de iniciativa geoturística aplicada al desarrollo rural

Se presenta la “Ruta de las huellas fósiles”, realizada en el casco urbano de Monsagro (Sierra de Francia, Salamanca). Mediante seis paneles didácticos e interpretativos, que incluyen el acceso “online” desde las nuevas tecnologías (smartphone, tablets, ipod….) a información complementaria implementada en videos, códigos QR, geoapps y juegos, se han promocionado y divulgado los contenidos geológicos de la zona, basados principalmente en el interés paleontológico de sus icnofósiles, atribuidos a diversos tipos de gusanos y trilobites durante el Ordovícico Inferior, y en el interés geomorfológico de sus cresterías cuarcíticas con relieve apalachiense, del encajamiento fluvial del río Agadón y de sus formaciones superficiales como canchales. Los visitantes señalan como fortalezas de la ruta su fácil y didáctico recorrido, así como la implicación ciudadana en la conservación de las icnitas

Holocene aeolian phases and human settlements along the Atlantic coast of southern Spain

A combined geomorphological, radiocarbon dating, archaeological and historical approach permits a refining of the age of the coastal dune systems related to estuaries in the Gulf of Cadiz. Three dune systems are distinguished in this paper. The oldest one, DI, which accumulated under prevailing WSW winds during the first millennium BC, overlays both the occupational horizons of Late Neolithic-Early Copper Age (fourth millennium BC) and the 'lithic workshop levels' (fourth to second millennia BC). The middle dune system, D2, containing both Roman and medieval remains, accumulated between the thirteenth or fourteenth centuries and the seventeenth century AD. The youngest D3 system is associated with the time of building of watchtowers in the seventeenth century AD but extends to the present; it is related to SW prevailing winds. We explain the absence of aeolian deposits prior to ~2700 cal. BP as the result of trapping of a large part of the sediment supply in the estuaries, which starved the neighbouring beaches and aeolian settings. Aeolian accumulation reached significant values when sedimentation in the coastal zone changed from being mainly aggradational in the estuaries (~6500~2700 cal. BP) to mainly progradational in spit barriers and related dunes (post ~2700 cal. BP). The present analysis of aeolian systems suggests a non-direct correlation, at least in some cases, between coastal progradation of spit barriers and aridity

Improving the coastal record of tsunamis in the ESI-07 Scale : Tsunami Environmental Effects Scale (TEE-16 Scale)

This paper discusses possibilities to improve the Environmental Seismic Intensity Scale (ESI-07 scale), a scale based on the effects of earthquakes in the environment. This scale comprises twelve intensity degrees and considers primary and secondary effects, one of them the occurrence of tsunamis. Terminology and physical tsunami parameters corresponding to different intensity levels are often misleading and confusing. The present work proposes: i) a revised and updated catalogue of environmental and geological effects of tsunamis, gathering all the available information on Tsunami Environmental Effects (TEEs) produced by recent earthquake-tsunamis; ii) a specific intensity scale (TEE-16) for the effects of tsunamis in the natural environment at coastal areas. The proposed scale could be used in future tsunami events and, in historic and paleo-tsunami studies. The new TEE-16 scale incorporates the size specific parameters already considered in the ESI-07 scale, such as wave height, run-up and inland extension of inundation, and a comprehensive and more accurate terminology that covers all the different intensity levels identifiable in the geological record (intensities VI-XII). The TEE-16 scale integrates the description and quantification of the potential sedimentary and erosional features (beach scours, transported boulders and classical tsunamites) derived from different tsunami events at diverse coastal environments (e.g. beaches, estuaries, rocky cliffs,). This new approach represents an innovative advance in relation to the tsunami descriptions provided by the ESI-07 scale, and allows the full application of the proposed scale in paleoseismological studies. The analysis of the revised and updated tsunami environmental damage suggests that local intensities recorded in coastal areas do not correlate well with the TEE-16 intensity (normally higher), but shows a good correlation with the earthquake magnitude (Mw). Tsunamis generated by earthquakes can then be considered efficient processes in the direct transference of the "energy" released by offshore seismogenic sources to the nearest coastal areas, even over distances of hundreds of kilometres (>200km). This scale, as the previous ones, is independent of the earthquake type (i.e. style of faulting) and only focuses on the environmental effects triggered by tsunamis of seismic origin

La difusión de los valores expresivos en el trabajo

The aim of this paper is to test two theoretical propositions that try to explain the observed variations in the distribution of instrumental and expressive work values. On the one hand the generation effect hypothesis, which assumes that a value shift is the result of the replacement of older generations by younger ones, and, on the other hand, the hypothesis that states that the change is determined by factors related to individual socioeconomic status. Data, from ten European countries, show that the hypothesis of generational change is inconsistent and reinforce the importance of educational level as a factor to explain work orientations.L’objectif de cet article est de vérifier deux proposi­tions théoriques qui essaient d’expliquer les varia­tions observées dans la distribution des valeurs instrumentales et expressives du travail. D’un côté l’hypothèse du changement intergénérationnel, qui suppose qu’un changement de valeurs soit le résul­tat du remplacement des plus vieilles générations par les plus jeunes et, d’un autre côté, l’hypothèse qui affirme que le changement est déterminé par des facteurs relatifs au statut socio-économique de l’individu. Les données de dix pays européens montrent que l’hypothèse du changement intergé­nérationnel est inconsistante et renforcent l’impor­tance du niveau d’études comme facteur explicatif des orientations de travail.El objetivo de este artículo es verificar dos proposiciones teóricas que tratan de explicar las variaciones observadas en la distribución de los valores instru­mentales y expresivos del trabajo. Por un lado la hipótesis del cambio intergene­racional, que supone que un cambio de valores es el resultado del reemplazo de las generaciones más viejas por las más jóvenes y, por otro lado, la hipótesis que afirma que el cambio está determinado por factores relacionados con el status socioeconómico del individuo. Los datos de diez países europeos muestran que la hipótesis del cambio intergeneracional es inconsistente y refuerzan la importan­cia del nivel de estudios como factor explicativo de las orientaciones laborales

Paleo and historical seismicity in Mallorca (Baleares, Spain): a preliminary approach

The island of Mallorca is subject to low seismic activity. The instrumental record shows that current seismicity is surficial (La isla de Mallorca presenta una actividad sísmica baja. El registro instrumental muestra que la sismicidad actual es superficial

Dunas eólicas y facies asociadas pleistocenas y holocenas en el acantilado del Asperillo (Huelva)

Facies analysis and tridimensional relationships of the eolian and eolian-connected deposits of Pleistocene and Holocene age in Huelva allow to proprose sedimentary models and discuss their temporal evolution and chronology