2,009 research outputs found
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
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