Papers by Alejandro Cearreta
Journal of Radioanalytical and Nuclear Chemistry, 2020
This study describes a rapid method for sequential determination of uranium and plutonium isotope... more This study describes a rapid method for sequential determination of uranium and plutonium isotopes in soil and sediment samples and its application to the study of Anthropocene sedimentary records. Different pretreatment methods have been tested (open-vessel digestion, borate salts fusion and NaOH salt fusion) achieving the complete dissolution of the sample in case of fusion methods. LiBO2 and Li2B4O7 (80/20) flux was finally selected because a higher amount of sample can be analyzed (up to 5 grams). Moreover, separation steps with extraction chromatographic resin UTEVA were optimized. Average recoveries obtained for uranium and plutonium were acceptable, 59 % and 72 % respectively, and relative bias were below ± 15 %. The time to complete the separation is approximately 11 hours without ashing the samples and, consequently, it can be used in emergencies.
Journal of Iberian Geology, 2008
In 1970 the largest oil refinery in Spain was built on the Muskiz estuary and occupies most of it... more In 1970 the largest oil refinery in Spain was built on the Muskiz estuary and occupies most of its original surface. An integrated high-resolution microfaunal-geochemical study has revealed the evolution and environmental development of this estuary during the last 120 years, mainly by the identification and assessment of natural processes versus anthropogenic impacts. Benthic foraminifera, trace elements and PAHs data from surface sediment samples and sediment cores from the meagre remaining intertidal flat and marsh areas together with short-life radiometric isotope determinations provide a chronology for environmental changes in this estuary. Concentrations of organic and inorganic pollutant, both in modern and recent materials, are generally low and show no significative variations in space or time, except those associated to sedimentological changes in the core records. Natural processes in the middle estuary indicate the change from previous sandy, normal-salinity conditions t...
The Bay of Biscay coastal area is a typical inundation coastline, formed as a consequence of the ... more The Bay of Biscay coastal area is a typical inundation coastline, formed as a consequence of the eustatic sea-level rise that followed the last deglaciation. Erosive processes are dominant along the southern area (named Cantabrian coast of Spain), as constant wave attack causes active cliff destruction. Short and narrow estuaries are separated from the open sea by sandbars, beaches and dune deposits. The eastern area of the Bay of Biscay (known as Aquitaine coast of France) is mainly a straight and continuous sandy beach backed by a coastal dune system fixed during the 19th century. These extensive dune fields formed when sand deposits on the continental shelf were reworked during the Holocene sea-level rise. The morphology and extent of the different estuarine sedimentary environments are constantly altered by erosion and deposition of sediments, and they are sensitive to even small changes in sea level. The Holocene transgressive episode caused the deposition of large volumes of w...
Marine Micropaleontology, 2004
The foraminiferal assemblages recorded in the sedimentary successions of nine boreholes drilled i... more The foraminiferal assemblages recorded in the sedimentary successions of nine boreholes drilled in the Bilbao estuary have been analyzed. Palaeoenvironmental interpretation of these and other previously studied assemblages defines the Bilbao estuary sedimentary infill as a depositional sequence within a fourth-order eustatic cycle (Holocene). This sedimentary sequence comprises a wide range of foraminiferal assemblage zones (FAZ) that are organized into three systems tracts. Each systems tract is composed by a distinct suite of FAZs separated by continuous stratigraphic surfaces. During Lateglacial low sea-level conditions, sedimentation was represented by fluviatile gravels and coarse sands barren of foraminifera (lowstand systems tract). During marine transgression (transgressive systems tract, 8500-3000 cal years BP), great volumes of mainly near-marine sediments were deposited in the lower estuary, alternation of brackish and near-marine sediments were accumulated in the middle estuary, and brackish materials sedimented in the upper estuary. The highstand systems tract deposited during the upper Holocene (3000 cal years BP-19th century human reclamation) represented brackish intertidal and supratidal conditions as the sedimentary infill was taking place under stabilized sea-level. Comparison of these results with other sedimentary sequences from different coastal areas in the Bay of Biscay indicates that, following postglacial sea-level rise, modern estuaries in the region began to develop around 8500 cal years BP. A final transgressive event was dated at around 3000 cal years BP when sea level reached approximately its present position after a second upward-shallowing sequence commenced.
Geogaceta, 2022
Se ha analizado el registro sedimentario reciente del estuario del Nalón a partir de dos sondeos ... more Se ha analizado el registro sedimentario reciente del estuario del Nalón a partir de dos sondeos intermareales que han sido datados mediante 210Pb y 137Cs. Los resultados muestran por primera vez sus asociaciones características de foraminíferos bentónicos, constituidas por un total de 46 especies, así como los importantes cambios experimentados por estas asociaciones, en consonancia con las variaciones en el magnetismo ambiental, como consecuencia, posiblemente, de las actividades mineras desde 1850 CE que sugieren unas condiciones ambientales deterioradas. Estas malas condiciones persistieron durante décadas, incluso más allá del cese de la minería de mercurio y carbón, hasta el siglo XXI cuando se ha comenzado a observar una leve recuperación ambiental.
Comunicações Geológicas, 2021
The Avilés estuary is one of the most important industrial ports in northern Spain, whose natural... more The Avilés estuary is one of the most important industrial ports in northern Spain, whose natural characteristics have been largely altered since the 1830s. Here, the environmental transformation of this estuary during the 19th century is explored using a multi-proxy approach including benthic foraminiferal content, sedimentology (grain-size), trace metals and short-lived radionuclides (210Pb and 137Cs) analysed from a 50-cm-long sediment core and a surface sample collected from the middle part of the estuary in the Pedro Menéndez Channel. The obtained results provide evidence that indicate an evolution from a naturally-driven environment with high a marine influence towards a more restricted setting under brackish conditions. The observed environmental change is interpreted as being mostly derived from physical modifications linked to the marsh reclamation and channelling starting in 1833 and intensified since 1860. This study provides a preindustrial environmental reference framework for future studies in coastal areas of the NW Atlantic Iberian margin.
Rosol, Ch. & Rispoli, G. (eds.) Anthropogenic Markers: Stratigraphy and Context, Chapter: 1. Max Planck Institute for the History of Science, Berlin in coop with HKW, Berlin and AWG, IUGS., 2022
The Anthropocene Working Group is preparing the case for the definition of a new stratigraphic Ep... more The Anthropocene Working Group is preparing the case for the definition of a new stratigraphic Epoch: this requires the demonstration of an objective change in properties of a geological archive over time. As each property being examined for this distinction can be considered as a time series, we encounter a classic scientific problem of distinguishing signal from noise. We need to understand the reasons why a signal of change should exist in order to know how to look for it—for example, in what chemical form would a new pollutant emerge? We also need a theory (a model) of the noise—over time, how large are the natural background fluctuations, and what are their properties? A familiar example of this challenge is the tricky problem of distinguishing long-term climate change from the background of weather events. In this essay we examine these issues with respect to several chemical signals of environmental change which reflect global (anthro-)(bio-)geochemical cycles. To begin, we see
what can be learned from the extensive measurements of sea-level change: an instructive example of a high-quality source of data with considerable noise in terms of geographic variation.
https://www.anthropocene-curriculum.org/contribution/the-anthropocene-signal-amidst-the-noise
Rosol, Ch. & Rispoli, G. (eds.) Anthropogenic Markers: Stratigraphy and Context, Chapter: 2. Max Planck Institute for the History of Science, Berlin in coop with HKW, Berlin and AWG, IUGS., 2022
Extinction, coupled with many other biological signals, is a major
geological indicator of the An... more Extinction, coupled with many other biological signals, is a major
geological indicator of the Anthropocene. The introduction of non-native
species, deforestation, depletion of fisheries and modification of coastal
environments, domestication of animals, and the reconfiguration of
terrestrial ecosystems are all evident in the geological record and are
being explored by the Anthropocene Working Group (AWG) and many
other investigators. This essay begins by outlining the geological record of
life over four billion years, the calamities that have occasionally erased
much of its diversity, and the more recent human impacts upon it. We
show that lakes, seas, estuaries and wetlands provide important archives
of humanity’s reconfiguration of life, and we speculate on the biological
and paleontological signature of the near future.
https://www.anthropocene-curriculum.org/contribution/biological-and-paleontological-signatures-of-the-anthropocene
Con el fin de evaluar la aceleracion en el ascenso relativo del nivel marino durante el Antropoce... more Con el fin de evaluar la aceleracion en el ascenso relativo del nivel marino durante el Antropoceno, se han comparado los resultados previamente establecidos para el siglo XX con los resultados obtenidos a partir del estudio de 61 nuevos puntos indicadores del nivel marino durante el Holoceno en el sur del Golfo de Vizcaya. Estos resultados indican un ascenso rapido hasta los circa 7000 anos cal BP que se puede estimar en 9-12 mm ano-1. Desde entonces, el nivel del mar ha ascendido suavemente en concordancia con los datos proporcionados a nivel global, con una velocidad media de 0,7 mm ano-1. Esta velocidad contrasta netamente con la tasa de ascenso registrada durante el siglo XX de 1,9 mm ano-1, confirmando la aceleracion detectada a nivel global como resultado de las actividades antropogenicas. Aunque los resultados obtenidos son altamente satisfactorios, los diferentes rangos de error proporcionados por ambos estudios hacen necesarios mas estudios de este tipo para reducir los er...
E. Leorri was supported by a postdoctoral grant from the Basque Government and by the Conseil GA ... more E. Leorri was supported by a postdoctoral grant from the Basque Government and by the Conseil GA ©nA ©ral of the VendA ©e (F). This work has been partially funded by the UNESCO06/08 and IT-332-07/GIU06-10 research contracts and it represents a contribution to IGCP project #495.
Para evaluar la respuesta cuantitativa de los foraminiferos con en relacion con los niveles marea... more Para evaluar la respuesta cuantitativa de los foraminiferos con en relacion con los niveles mareales del estuario de Mira, se han desarrollado una serie de funciones de transferencia basadas en un matriz de datos compuesta por 29 muestras y 95 especies obtenidas en tres transeptos. La relacion entre los resultados obtenidos e inferidos indica el optimo funcionamiento de las funciones de transferencia (r 2 jack = 0.87), lo cual implica que reconstrucciones de gran precision (error: ± 12 cm) de los cambios recientes en el nivel marino son posibles. Por otro lado, es importante estudiar el posible efecto de la relacion no lineal entre las mareas y la elevacion de las muestras en los errores de reconstruccion.
The process of saltmarsh natural regeneration in the Basque coast is studied on the basis of micr... more The process of saltmarsh natural regeneration in the Basque coast is studied on the basis of microfaunal and geochemical determinations and historical data. After the abandonment of agricultural soils in estuarine areas during the 20th century, the entrance of brackish water rapidly transformed theses areas with deposition of increasing amounts of sand and benthic foraminifera at a very high sedimentation rate. This rapid regeneration process is of great interest for environmental management of modern coastal areas particularly under the current scenario of accelerating sea-level rise when scientifically-sound adaptation measures should be implemented.
The Holocene sedimentary filling in the estuaries of the Cantabrian Coast has been studied by the... more The Holocene sedimentary filling in the estuaries of the Cantabrian Coast has been studied by the boreholes EL1, Ria of Bilbao, and IS2, Ria of Bidasoa. The micropalaeontological analysis of both litoral sequences has allowed to recognize 5 and 7 different benthic foraminifera assemblages respectively. These have been used to determine the correspondant estuarine depositional subenvironments (from subtidal to middle/upper marsh). Two recurrent phases of sediment build up as sea level rose were distinguished. They were interpreted as the consequence of two different marine advances on this region: a first one dared around 8000 years B.P. (Atlantic stage) and a second one identified around 2500 years B.P. (Subatlantic srage).
espanolSe ha analizado el contenido en metales y foraminiferos bentonicos de los sedimentos super... more espanolSe ha analizado el contenido en metales y foraminiferos bentonicos de los sedimentos superficiales de la ria de Suances con el fin de caracterizar la respuesta geoquimica y microfaunistica a las condiciones ambientales actuales en esta zona costera. Los elevados niveles de Zn, Pb y Cd junto con las reducidas cantidades de foraminiferos sugieren una situacion ambiental muy negativa y persistente en el tiempo asociada a los vertidos mineros, industriales y urbanos efectuados en este ecosistema durante los ultimos 160 anos. El analisis geologico multidisciplinar representa una buena herramienta para el seguimiento historico, tanto preterito como futuro, de los procesos de transformacion ambiental. EnglishMetal and benthic foraminiferal contents from surface sediments of the Suances estuary have been analyzed in order to characterize the geochemical and microfaunal responses to the present environmental conditions in this coastal area. High levels of Zn, Pb, and Cd together with ...
1Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, 6 Universidad del Pa... more 1Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, 6 Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain. 7 mariajesus.irabien@ehu.eus 8 2Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, 9 Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain. 10 alejandro.cearreta@ehu.eus, humberto.serrano@ehu.eus 11 3Departamento de Ciencias Médicas y Quirúrgicas, Universidad de Cantabria UC, 12 Avenida. Herrera Oria s/n, 39011 Santander, Spain. jose.gomez@unican.es 13 4Unidad Académica Procesos Oceánicos y Costeros, Instituto de Ciencias del Mar y 14 Limnología, Universidad Nacional Autónoma de México, 04510 Ciudad de México, 15 México. jasanchez@cmarl.uman.mx 16 5Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad 17 Nacional Autónoma de México, Calz. Joel Montes Camarena s/n, 82000 Mazatlán, 18 Sinaloa, México. caro@ola.icmyl.unam.mx 19 Corresponding author: María Jesús Ira...
The Holocene, 2016
Major Mediterranean deltas began to develop during a period between 8000 and 6000 yr BP when the ... more Major Mediterranean deltas began to develop during a period between 8000 and 6000 yr BP when the rate of fluvial sediment input overtook the declining rate of sea-level rise. However, different authors have argued that the Ebro Delta primarily formed during the late Middle Ages as a consequence of increased anthropogenic pressure on its river basin and these arguments are supported by the scarcity of previous geological studies and available radiocarbon dates. To reconstruct the environmental evolution of the Ebro Delta during the Holocene, we used micropalaeontological analysis of continuous boreholes drilled in two different locations (Carlet and Sant Jaume) on the central delta plain. Different lithofacies distributions and associated environments of deposition were defined based on diagnostic foraminiferal assemblages and the application of a palaeowater-depth transfer function. The more landward Carlet sequence shows an older and more proximal progradational delta with a sedime...
Estuarine, Coastal and Shelf Science, 2016
Understanding the dynamics of salt marshes is key under the current climatic scenario. With this ... more Understanding the dynamics of salt marshes is key under the current climatic scenario. With this objective we took 50-cm long sediment cores from recently regenerated salt marshes in the southern Bay of Biscay. These cores were analyzed using microfaunal and geochemical ...
RESUMEN Los trabajos de excavación en el área de Zaldu (Sopelana, Bizkaia) han evidenciado la pre... more RESUMEN Los trabajos de excavación en el área de Zaldu (Sopelana, Bizkaia) han evidenciado la presencia de dos yacimientos arqueológicos, Mendieta I y II. En el primero, la industria lítica aparece dentro de un contexto estratigráfico original atribuido al Paleolítico Inferior. Las características estratigráficas y sedimentarias de formación del yacimiento derivan de procesos fluvio-aluviales y pedogenéticos. Palabras clave: paleosuelo, paleolítico antiguo, tecnología lítica, uribe kosta. SUMMARY The excavation works in the Zaldu area (Sopelana, Biscay) has evidenced the presence of two archaeological sites, Mendieta I and II. In the first one, the lithic industry appears within an original stratigraphic context of lower Paleolithic age. The stratigraphic and sedimentary features in this site derived from fluvio-alluvial and pedogenic processes. Key words: paleo-soil, ancient palaeolithic, lithic technology, uribe kosta. LABURPENA Zaldu gunean (Sopela, Bizkaia) egindako indusketa lanak bi aztarnategi arkeologikoen topaketa eman du, hau da, Mendieta I eta II. Lehenengoan, harri industria Behe Paleolito garaiko jatorrizko testuinguru estratigrafiko batean agertzen da. Sorkuntzako ezaugarri estratigrafikoak eta sedimentarioak prozesu flubio-alubial eta pedogenetiko bategatik ematen da. Gako-hitzak: paleo-lurra, behe paleolitoa, harri industria, uribe kosta.
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Papers by Alejandro Cearreta
what can be learned from the extensive measurements of sea-level change: an instructive example of a high-quality source of data with considerable noise in terms of geographic variation.
https://www.anthropocene-curriculum.org/contribution/the-anthropocene-signal-amidst-the-noise
geological indicator of the Anthropocene. The introduction of non-native
species, deforestation, depletion of fisheries and modification of coastal
environments, domestication of animals, and the reconfiguration of
terrestrial ecosystems are all evident in the geological record and are
being explored by the Anthropocene Working Group (AWG) and many
other investigators. This essay begins by outlining the geological record of
life over four billion years, the calamities that have occasionally erased
much of its diversity, and the more recent human impacts upon it. We
show that lakes, seas, estuaries and wetlands provide important archives
of humanity’s reconfiguration of life, and we speculate on the biological
and paleontological signature of the near future.
https://www.anthropocene-curriculum.org/contribution/biological-and-paleontological-signatures-of-the-anthropocene
what can be learned from the extensive measurements of sea-level change: an instructive example of a high-quality source of data with considerable noise in terms of geographic variation.
https://www.anthropocene-curriculum.org/contribution/the-anthropocene-signal-amidst-the-noise
geological indicator of the Anthropocene. The introduction of non-native
species, deforestation, depletion of fisheries and modification of coastal
environments, domestication of animals, and the reconfiguration of
terrestrial ecosystems are all evident in the geological record and are
being explored by the Anthropocene Working Group (AWG) and many
other investigators. This essay begins by outlining the geological record of
life over four billion years, the calamities that have occasionally erased
much of its diversity, and the more recent human impacts upon it. We
show that lakes, seas, estuaries and wetlands provide important archives
of humanity’s reconfiguration of life, and we speculate on the biological
and paleontological signature of the near future.
https://www.anthropocene-curriculum.org/contribution/biological-and-paleontological-signatures-of-the-anthropocene
La Asociación Naturalista Txipio Bai fue fundada en 1993 con el objetivo de conseguir la paralización del macroproyecto urbanístico “Marina de Txipios”. Desde entonces trabaja por el reconocimiento y la defensa de los valores naturales de Uribe Kosta y el estuario del Butroe. Fue declarada de utilidad pública por el Gobierno Vasco en el año 2012.