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Titre du jeu de données : CLEHA_Ethiopia_L.Abiyata_AB95II_Diatoms
Mots-clés thématiques (thesaurus du GCMD) :
Paleoclimate>
Land Records>
Microfossils
Biosphere>
Aquatic Habitat>
Lakes
Hydrosphere>
Surface Water>
Lakes
Hydrosphere>
Water Quality>
Conductivity
Paleoclimate>
Ocean/Lake Records>
Lake Levels
Personne à contacter pour obtenir les informations sur le jeu de données :
CHALIÉ
Françoise
Centre Européen de Recherche et d'Enseignement de Géosciences de l'Environnement (CEREGE)
UMR 6635
Résumé :
Diatom study of a 12.6 m long sediment core (AB95II) from Lake Abiyata (Ethiopian Rift, ~8°N) revealed large amplitude changes in the water level and chemistry over the past 13.4 cal. kyr BP. Past water conductivity, pH and water chemical facies, reflected by ionic ratios, are quantitatively reconstructed, based on diatom transfer functions previously established. Conductivity has varied from 400 to 21,500 µS.cm-1, pH from 8 to 10.5; the anion ([HCO3-+CO32-] / [Cl-+SO42-]) and cation ([Na++K+] / [Ca2++Mg2+]) ratios ranged between ~0.9-4, and 0.5-275, respectively. A high water salinity oscillation is recorded at the base of the sequence; the extrapolated age of this interval (12.7-12.0 cal. kyr BP) corresponds to the Younger Dryas Chronozone. The early-mid-Holocene registers a high-stand freshwater lake between 12 and 5.4 cal. kyr BP. Changes in diatom assemblages suggest minor changes in water depth, lake mixing and/or nutrient content, during this interval. Post 5.4 cal. kyr BP, shallow, saline conditions generally predominates. Two short-term regressive events are recorded at 5.6 and 3.0 cal. kyr BP. Our results are roughly consistent with previous works in the region. They refine the timing of the hydrochemical changes and quantify their amplitude, thus providing inputs for modelling approaches.
Format des données : MSExcel (.xls) -
Date de création :
2006-04-07
Les publications :
Chalié, F., Gasse, F.
(2002).
Late Glacial-Holocene diatom record of water chemistry and lake level change from the Tropical East African Rift Lake Abiyata (Ethiopia).
Palaeogeography, Palaeoclimatology, Palaeoecology
187,
259-283.
Date de début : 0 cal BP
Date de fin : 13000 cal BP
Méthode de datation : Radiocarbon (14C)
Coordonnées (en fraction décimale de degré) :
Coordonnée limite sud :
7.0
Coordonnée limite nord :
8.0
Coordonnée limite ouest :
38.0
Coordonnée limite est :
39.0
Altitude minimale :
1578.0
Altitude maximale :
1578.0
Pays :
Ethiopia
Region / Continent :
East Africa
Region / Continent :
Southern Hemisphere
Localité : Lake Abiyata
Etat d'acquisition : In work
Fréquence de mise à jour : As needed
Restriction sur l'accessibilité de l'ensemble des données :
restricted
Restriction / condition d'utilisation : Citation of the original publication - Password
Rapport sur la qualité :
Données publiées dans Palaeogeography, Palaeoclimatology, Palaeoecology.