Diapositive 1 - de l'Université libre de Bruxelles

Chapitre IIICHAPITRE IIISalinity effects on the Mg/Ca and Sr/Ca in starfish skeletons and the echinodermrelevance for paleoenvironmental reconstructionsCatherine Borremans 1 , Julie Hermans 1,2 , Sandrine Baillon, Luc André 3 , Philippe Dubois 1*∗Published in Geology, April 2009, 4: 351-354doi : 10.1130/G25411A.1;2ABSTRACTSkeletal Mg/Ca ratios of well-preserved fossil echinoderms have been used to reconstructpast Mg/Ca ratio in seawater up to the Phanerozoic, taking into account the knowntemperature effect on this ratio. This study investigates the effects of salinity and growthrate on Mg/Ca and Sr/Ca ratios in starfish calcite skeletons grown in experimentalconditions. Both ratios are not related to growth rate: on the contrary, both are positivelyrelated to salinity. This effect induces an error on the reconstructed Mg/Ca ratio inseawater that may reach 46%. An intriguing inverse relation between skeletal Sr/Ca ratioand temperature was recorded. The salinity effects are presumably due to physiologicalregulation processes.∗ 1Laboratoire de Biologie Marine (CP 160/15), Université Libre de Bruxelles, 50 avenue F.D. Roosevelt, B-1050 Brussels, Belgium2 Département des Invertébrés, Institut Royal des Sciences Naturelles de Belgique, 29 rue Vautier, B-1000 Brussels, Belgium3 Section de Minéralogie, Pétrographie et Géochimie, Musée Royal d’Afrique Centrale, 13 Leuvensesteenweg, B-3080 Tervuren,Belgium61