Evolution of the Aveiro Cretaceous aquifer (NW Portugal) during the Late Pleistocene and present day:: evidence from chemical and isotopic data
M. T. Condesso De Melo, P. M. M. Carreira Paquete, M. A. Marques Da Silva, 2001. "Evolution of the Aveiro Cretaceous aquifer (NW Portugal) during the Late Pleistocene and present day:: evidence from chemical and isotopic data", Palaeowaters in Coastal Europe: Evolution of Groundwater since the Late Pleistocene, W. M. Edmunds, C. J. Milne
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A combined hydrogeological, geochemical and isotopic investigation was performed in the Aveiro Cretaceous coastal aquifer in order to investigate the rock-water interaction and the evolution of palaeowaters. The results indicate an aquifer with well-defined freshwater (<50 mg l−1 Cl−) throughout most of the aquifer as far as the coastline and with very slow chemical kinetics for the water–rock interactions. The low mineralization may be explained by the mainly siliciclastic composition of the aquifer sediments, while calcite dissolution and cation exchange were also considered to be involved in the groundwater chemical evolution. This interpretation is in agreement with lithology and facies changes, and was validated by the PHREEQC-2 modelling results. Radiocarbon ages indicate a smooth gradient across the aquifer, implying continuous flow during the late Pleistocene and Holocene. Noble gas ratios indicate that the mean annual air temperatures were lower by 5–6°C at the last glacial maximum (LGM). In contrast to most areas with continental palaeowaters, the environmental isotopes indicate enrichment (0.8–1.0‰ in 18O), interpreted as reflecting the composition of the oceans at the time of the LGM at this maritime site, as well as the constancy of the air mass circulations over the period to the present day. An outlet for the aquifer is inferred offshore to account for the observed geochemical data, with the possibility that freshwater could still also be found offshore.
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Palaeowaters in Coastal Europe contains 17 contributions from an international array of authors. They discuss the history of groundwater evolution during the late Pleistocene in the coastal areas of Europe from the Baltic region to the Iberian peninsula and the Canary Islands. Geochemical and geophysical techniques for evaluating palaeowaters are reviewed. The focus of the book is on changes in the hydrogeological regime during the Quaternary and their impacts on groundwater movement and chemistry in European coastal aquifers.
The work summarized in the papers was carried out by a partnership of European scientists under the auspices of the PALAEAUX project, an EC initiative. Researchers from the fields of hydrogeology, geochemistry, isotope hydrology and Quaternary studies attempted to reconstruct the most probable movement of groundwater in the study area over the past 100 000 years and its response to climatic events of global significance during the last glacial cycle. The results of this work, summarized in this volume, allow a better understanding of the water resources found at and near the coastlines of northern and western Europe. During times of lowered sea level, it appears that groundwaters were replenished to depths greater than occur at the present day. These pristine freshwater reserves are an irreplaceable asset. Their location at coastlines where populations and water demands are high and often seasonal means that they need careful management to avoid over-exploitation or contamination. The inevitable conflicts that this resource management creates are discussed.
Palaeowaters in Coastal Europe: evolution of groundwater since the late Pleistocene will be of interest to Quarternary scientists, hydrogeologists, marine scientists engaged in coastal research and those involved in environmental science and the management of groundwater assests.