The Anthropocene perspective : a geological approach to climate change

The most recent division of geological time is based on climate events caused by variations in the Earth's orbit and axis of rotation on a scale of thousands of years. However, the magnitude of geological change caused by humankind through its still young technosphere, particularly since the mid-20th century, is negatively affecting the other classical spheres (atmosphere, hydrosphere, biosphere, and geosphere). This is because of our increasing demand for raw materials and the incomplete recycling of its residues (e.g., greenhouse gases). The massive use of fossil fuels to power the recent boom in industrial development has turned humanity into the new agent of planetary-scale climate change. Some alterations associated with this new Anthropocene climate system are already irreversible and exceed the natural variability of the last few thousand years.This work is based on different ideas published collectively by the Anthropocene Working Group (International Commission on Stratigraphy) , of which the author is a member, over the last few years. It received economic support from project grants RTI2018-095678-B-C21 (MCIU/AEI/FEDER, UE) and IT976-16 (EJ/GV) . Two anonymous reviewers improved the original manuscript with their comments and suggestions

A high marsh transfer function for sea-level reconstructions in the southern Bay of Biscay.

E. Leorri was supported by a postdoctoral grant from the Basque Government and by the Conseil Gà ©nà ©ral of the Vendà ©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

Cambios recientes del nivel marino en el sur del Golfo de Vizcaya: reconstrucciones basadas en funciones de transferencia aplicadas en marismas en comparación con datos instrumentales

In order to assess the accuracy and regional significance of salt-marsh reconstructions of former sea level based on foraminiferal transfer functions, we compared the calibration of the foraminiferal assemblages of two salt-marsh cores from two estuaries using the regional transfer function constructed for the southern Bay of Biscay. The foraminifera-based reconstructions were placed into a temporal framework using 137Cs, heavy metal concentrations, and 210Pb-derived sediment accumulation rates. The resulting relative sea-level (RSL) curves were compared with the nearest tide-gauge data (Santander). The two RSL trends from core sediments show excellent agreement and are in very good agreement with instrumental data, providing a regional relative sea-level rise of 1.9 mm yr-1 for the 20th century.Con el fin de evaluar la precisión y el carácter regional de las reconstrucciones del nivel marino basadas en funciones de transferencia usando foraminíferos de marisma, hemos comparado la calibración de las asociaciones de foraminíferos de dos sondeos perforados en sendos estuarios, usando una función de transferencia de validez regional construida para el sur del Golfo de Vizcaya. Estas reconstrucciones basadas en las asociaciones de foraminíferos han sido situadas en un marco temporal utilizando 137Cs, concentraciones de metales pesados y los cocientes de acumulación sedimentaria basados en 210Pb. La curva del nivel marino resultante ha sido comparada con el mareógrafo más próximo al área de estudio (Santander). Las dos curvas obtenidas a partir de los sondeos presentan una excelente correlación entre sí y muy buena correlación con los datos procedentes del mareógrafo, proporcionando un ascenso relativo del nivel marino de 1.9 mm año-1 para el siglo XX, siendo este ascenso de carácter regional

Impacto humano sobre la costa

Sin resumenSin resume

El registro geológico de la transformación ambiental de la ría de Bilbao durante el Holoceno y el Antropoceno

The northeastern coast of Spain is characterized by Mesozoic-Cenozoic sedimentary rocks forming high cliffs interrupted by short, narrow estuaries that are separated from the open sea by sandbars, beaches and dune deposits. 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 well preserved estuarine sediments that can be studied to understand environmental and sea-level changes during this interglacial. The Bilbao estuary was originally the most extensive estuarine area on the Cantabrian coast of northern Spain. The modern estuary is 15 km long, an average of 100 m wide, and its channel depth ranges from 2 m in the upper estuary to 9 m at the mouth. The estuary is formed by the tidal part of the Nervion river, although four other rivers (Kadagua, Asua, Galindo and Gobelas) discharge into the main course. The tidal channel discharges into a wide marine bay called El Abra (average 3.5 km wide; up to 30 m deep). Tides are semidiurnal, with ranges between 4.6 m (spring tides) to 1.2 m (neap tides). The first iron and steel industry was opened on the middle estuary over reclaimed marshes as early as 1854. Since then, the natural features of the Bilbao estuary have been dramatically modified by urban, industrial and port developments. The exploitation of abundant local iron ore led to the early industrial development of Bilbao in the mid-19th century. The original estuary was rapidly reduced in size through land reclamation to form a tidal channel. This was isolated by dyking from its original intertidal areas, to allow a navigable watercourse from the city to the open sea. Today the Bilbao estuary is a largely artificial system which bears little resemblance to the original estuary. It has been calculated that the total amount of the original estuarine surface lost through human activity is approximately 1,000 ha. During the last 150 years, the Bilbao estuary has received wastes from many sources (mineral sluicing, industrial wastes and urban effluents) which have significantly degraded the environmental quality of the estuary. At present, the Bilbao estuary is the most polluted coastal area of northern Spain. A significant decrease in the flux of organic matter and heavy metal contaminants has occurred over the last decades, however, due to the implementation of environmental protection policies, the improvement in waste-treatment systems and the closure of some major factories during recent periods of economic recession. Furthermore, estuarine regeneration is currently being undertaken as part of a Revitalization Strategic Plan. Despite these improvements, the unremoved contaminated sediments from the intertidal areas may act as a long-term source of heavy metals to the aquatic environment through sediment mechanical reworking (e.g. dredging, shipping) and oxidation of anoxic sediments. Thus, these pollutants may continue procedures have been implemented. To reconstruct the palaeoenvironmental evolution of the Bilbao estuary since its formation following the postglacial rise of sea level, it have been analyzed the foraminiferal assemblages contained in eleven boreholes taken in the reclaimed areas of the middle and lower parts of the estuary. Integration of these results with similar data from previously studied boreholes has allowed us to reconstruct the environmental development of the Bilbao estuary during the Holocene. This environmental development has been organized into different systems tracts following a sequence-stratigraphic interpretation. Radiocarbon dating and palynological studies helped to locate in time the different palaeoenvironments and depositional episodes identified in the boreholes. Sediments that compose the estuarine infill range from basal fluvial coarse materials (Lateglacial), almost barren of foraminifera, that are interpreted as the lowstand systems tract (LST). This system tract is followed upwards by lower and middle Holocene transgressive materials (TST; 8500-3000 years cal BP), with upper Holocene regressive sediments on top (HST; 3000 years cal BP-19th century). This general sedimentary sequence is best represented in the middle estuarine area, and its sedimentary and microfaunal features are variable depending on its palaeogeographic setting: increasing muddy sediments and absence of open-marine elements are characteristic of the upper estuary, whereas increasing sandy sediments and reworking of the basal fluviatile materials are typical of the lower estuary. Comparison of these data with other sedimentary sequences from different coastal areas in the Bay of Biscay allows to reconstruct a general picture of the Holocene sea-level changes and coastal evolution in this area for the last 8500 years. On the other side, six cores retrieved from the Bilbao estuary tidal flats have been studied in order to evaluate the historical impact of the long lasting record of anthropogenic inputs, which have led to the disappearance of the indigenous microfauna and to the significant pollution of the sediments. Three different zones can be identified in the recent sedimentary record, reflecting initially the preindustrial estuarine conditions with abundant and diverse foraminiferal assemblages and baseline levels of metals, followed by the industrial-period sedimentary record, when high concentrations of metals in the estuarine environment allowed the development of abundant foraminiferal assemblages during the older industrial zone (period 1850-1950) that disappeared during the younger industrial zone (period 1950-2000) due to complete defaunation of the Bilbao estuary caused by minimum oxygen levels during this period. Obtained data provide important information in planning the restoration of the Bilbao estuary, because sediments have proven to be an important storage reservoir for pollutants and microfossils. Finally, the distribution and abundance of benthic foraminifera (together with geochemical analysis of heavy metals) from surface sediment samples (1997- 2003) and sediment cores collected from the intertidal flats of the Bilbao estuary have been studied to determine recent environmental contitions of this estuary. Furthermore a foraminiferal sampling network has been created in order to evaluate the future progress of the current regeneration schemes on a seasonal and anual basis. Pb-210 and Cs-137 determinations have also been undertaken to provide a chronology for pollutant inputs and ecological changes in the Bilbao estuary

Modern and late Holocene foraminiferal record of restricted environmental conditions in the Albufeira Lagoon, SW Portugal

Benthic foraminifera from twenty stations sampled twice were analyzed in order to examine the environmental conditions of the Albufeira coastal lagoon. Foraminiferal assemblages show an increase in the abundance, species diversity and allochthonous content seaward. Three zones have been defined: the inner and more restricted area of the lagoon where the main species are the euryhaline Ammonia tepida and Haynesina germanica; these two species together with Bulimina gibba and Brizalina britannica dominated the middle area; and, finally, in the mouth and marine- influenced back-barrier area the assemblages are made up of brackish and marine species such as A. tepida, Cribroelphidium williamsoni, Cibicides lobatulus and H. germanica. Additionally, samples from three cores were also examined. Sedimentological and micropalaeontological contents represent the last 2500 years of environmental evolution of the lagoon. Foraminiferal assemblages are not very abundant and they are dominated by H. germanica, A. tepida and Jadammina macrescens indicating very restricted conditions through time. In a regional context, and during the Late Holocene, after the development of a detrital barrier circa 5.5 cal yr BP, eustasy is considered to be a minor environmental control of the barrier-lagoonal system dynamics. Instead, environmental conditions were forced by local factors, such as frequency and duration of lagoon-ocean water exchanges, induced by both natural and artificial changes in the permeability of the sand-barrier

Transformación reciente de ambientes intermareales bajo un escenario de ascenso del nivel marino: ejemplos del norte de España

The transformation of two intertidal environments from northern Spain during the last 150 years shows an evolution from a tidal flat into a salt marsh environment, wit han intermediate transitional stage. The environment of deposition was reconstructed based on benthic foraminifera and sand content. Sediments were put into a temporal framework using short-lived radioisotope activities and heavy metal concentrations. The observed natural evolution responds to the availability of abundant sediment and the current sea-level rise scenario, where intertidal environments are trying to adapt to increasing flooding periods by accreting sediment rapidlyLa transformación de dos ambientes intermareales en el norte de España durante los últimos 150 años muestra la evolución desde una llanura intermareal a una marisma, con una etapa de transición intermedia. El paleoambiente se reconstruyó mediante el contenido en foraminíferos bentónicos y en arena. Los sedimentos fueron datados utilizando radioisótopos de vida corta y concentraciones de metales pesados. La evolución natural observada responde a la disponibilidad de abundante sedimento y al escenario actual de ascenso en el nivel del mar, donde los ambientes intermareales están tratando de adaptarse a los crecientes períodos de inundación acrecionando sedimento rápidament

Modern and late Holocene foraminiferal record of restricted environmental conditions in the Albufeira Lagoon, SW Portugal

Benthic foraminifera from twenty stations sampled twice were analyzed in order to examine the environmental conditions of the Albufeira coastal lagoon. Foraminiferal assemblages show an increase in the abundance, species diversity and allochthonous content seaward. Three zones have been defined: the inner and more restricted area of the lagoon where the main species are the euryhaline Ammonia tepida and Haynesina germanica; these two species together with Bulimina gibba and Brizalina britannica dominated the middle area; and, finally, in the mouth and marine- influenced back-barrier area the assemblages are made up of brackish and marine species such as A. tepida, Cribroelphidium williamsoni, Cibicides lobatulus and H. germanica. Additionally, samples from three cores were also examined. Sedimentological and micropalaeontological contents represent the last 2500 years of environmental evolution of the lagoon. Foraminiferal assemblages are not very abundant and they are dominated by H. germanica, A. tepida and Jadammina macrescens indicating very restricted conditions through time. In a regional context, and during the Late Holocene, after the development of a detrital barrier circa 5.5 cal yr BP, eustasy is considered to be a minor environmental control of the barrier-lagoonal system dynamics. Instead, environmental conditions were forced by local factors, such as frequency and duration of lagoon-ocean water exchanges, induced by both natural and artificial changes in the permeability of the sand-barrier

ECOESTRATIGRAFIA (FORAMINIFEROS BENTONICOS) DEL RELLENO ESTUARINO HOLOCENO EN EL LITORAL VASCO (GOLFO DE BIZKAIA)

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)