Marsh Sedimentology

El estudio del registro sedimentario holoceno del estuario de los ríos Tinto y Odiel (Huelva) se ha realizado históricamente por medio de sondeos y de afloramientos superficiales. Nuevos perfiles naturales en la Isla de Saltés (La Cascajera) están ofreciendo una nueva perspectiva sobre la génesis y cronología de los depósitos. Para la determinación temporal de estos procesos se llevaron a cabo dataciones radiométricas mediante el análisis de series de Uranio y de radiocarbono. El contraste de los resultados de ambas técnicas ha permitido observar grandes desfases temporales en las series de Uranio, siendo Las edades de 14C son unos 200 años más antiguas que las de U/Th, para las mismas muestras. La contaminación postsedimentaria en estos sistemas abiertos, ha favorecido el rejuvenecimiento de la edad de la muestra, por el continuo aporte al sistema de 234U y 238U. Esto pone de manifiesto lo inapropiado del método U/Th en sedimentos estuarinos recientes y, sobre todo, altamente conta...

Mazagon Beach is one of the most significant beaches in the SW Spanish coast from a touristic but also scientific point of view. Historically this beach developed a ridge-and-runnel system in the foreshore and extensive dunes in the backshore area. Today wave dynamics in this area is completely disturbed by human interventions, since large harbor infrastructures have been built near the beach. The construction of a new dock in the marina allowed observing in a wide trench the beach stratigraphic sequence as well as the geometric relationships between the Holocene facies and the Plio-Pleistocene formations. The base of the succession is a muddy level which is in contact with the Pleistocene alluvial sediments. On these facies, the beach sedimentary sequence consists on a vertical succession of bioclastic gravels and medium sands displaying parallel laminated sets alternating with foresets of crossbedding. Above this beach sequence, a complex, cross-stratified strata composed by very fine sands represents the supratidal coastal dunes. The entire sequence represents the deposition during the late pulses of rising sea level and the highstand period.

Mazagon Beach is one of the most significant beaches in the SW Spanish coast from a touristic but also scientific point of view. Historically this beach developed a ridge-and-runnel system in the foreshore and extensive dunes in the backshore area. Today wave dynamics in this area is completely disturbed by human interventions, since large harbor infrastructures have been built near the beach. The construction of a new dock in the marina allowed observing in a wide trench the beach stratigraphic sequence as well as the geometric relationships between the Holocene facies and the Plio-Pleistocene formations. The base of the succession is a muddy level which is in contact with the Pleistocene alluvial sediments. On these facies, the beach sedimentary sequence consists on a vertical succession of bioclastic gravels and medium sands displaying parallel laminated sets alternating with foresets of crossbedding. Above this beach sequence, a complex, cross-stratified strata composed by very fine sands represents the supratidal coastal dunes. The entire sequence represents the deposition during the late pulses of rising sea level and the highstand period.

La playa de Mazagon es una de las playas mas significativas de la costa SW de Espana desde un punto de vista turistico pero tambien cientifico. Historicamente esta playa desarrollo un sistema de crestas y surcos, asi como extensas dunas eolicas en el area emergida. Hoy dia, la dinamica de olas en esta area esta completamente perturbada por las intervenciones humanas, ya que se han construido grandes infraestructuras portuarias cerca de la playa. La construccion de una nueva ampliacion del puerto deportivo permitio observar en una amplia zanja la secuencia estratigrafica de la playa, asi como las relaciones geometricas entre las facies del Holoceno y las formaciones de Plio-Pleistoceno. La base de la sucesion es un nivel de fangos que esta en contacto con los sedimentos aluviales del Pleistoceno. En estas facies, la secuencia sedimentaria de playa consiste en una sucesion vertical de bioclasticas de gravas y arenas medias que muestran sets de laminas paralelas alternando con foresets...

The tsunami of 27 February 2010 that affected the coast of central Chile produced significant changes in the coastline of the Maule region. Some of these changes have been recorded in the geomorphology of sandy coastline between the Mataquito and Huenchullami rivers, named locally as "La Trinchera". The retreat of the coastline, the destruction of the bar of the Mataquito river and part of the bar of the Huenchullami river, and the formation of breachs and fans are the most important changes. As consequences of such an alteration is recorded in the sediment exchange in the beach-dune system, which is evidenced by the change in the dynamics of the dune field which is located inland. All these transformations and evolution of sandy coastline are revealed by satellite images obtained post earthquake.

Resumen: El análisis geológico pluridisciplinar de un testigo continuo obtenido en el río Tinto (SO de España) permite diferenciar tres facies sedimentarias, depositadas en el borde de canal o los canales distributarios menores (FA-1: arcillas negras) o debidas a la acción de tsunamis durante un periodo de estuario abierto (FA-2: arenas bioclásticas y gravas) o con un elevado grado de relleno (FA-3: arenas bioclásticas con gradación a arenas medias superiores). Estos eventos energéticos tuvieron lugar durante los últimos 3.800 años y la comparación con otros depósitos tsunamigénicos de esta área revela un notable grado de correlación con los tsunamis históricos que se han sucedido en este área.

The first human settlements (6000−4000 BP) in the early estuary of the Tinto and Odiel rivers were located in the ancient coastal banks or in the nearby hills. From 4000 years BP onwards, the estuarine sediments started to emerge as sand barriers and chenier plains, prograding towards the mouth. As the littoral strands stabilized morphologically, they are colonized by human settlements in successive periods, the oldest inland (Almendral) and more recent outward (Cascajera). These emerged morphologies were surrounded by muddy tidal flats in the estuary and only the high-energy marine events such as a tsunami or extraordinary storms were able to modify both the landscape and human settlements installed on them. This work also describes the morphodynamic model that built the chenier plain of La Cascajera.