Foraminiferal shell-weight evidence for sedimentary calcite dissolution above the lysocline |
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| Institution: | 1. School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom;2. School of Earth and Environmental Science, University of Queensland, Brisbane, Queensland, Australia;3. National Institute of Water and Atmosphere, Wellington, New Zealand;4. Institut de Ciències del Mar, ICM-CSIC, Barcelona, Catalonia, Spain;5. Institute of Geological Sciences and Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland;6. Institute of Earth Sciences, University of Lausanne, 1015 Lausanne, Switzerland;7. Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Catalonia, Spain;8. Max-Planck-Institut für Chemie, (Otto-Hahn-Institut), Hahn-Meitner-Weg 1, 55128 Mainz, Germany;1. Departamento de Ciencias de la Atmósfera y los Océanos (FCEN,UBA), Capital Federal, Argentina;2. Departamento de Física, Universidad Nacional del Sur, e Instituto Argentino de Oceanografía (CONICET), Bahía Blanca, Argentina;3. Departamento Oceanografía, Servicio de Hidrografía Naval, Buenos Aires, Argentina;4. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos, CONICET/CNRS, Buenos Aires, Argentina;1. Divisão de Geologia e Georecursos Marinhos, Instituto Português do Mar e da Atmosfera (IPMA), Lisboa, Portugal;2. CIMAR Associate Laboratory, CIIMAR, Porto, Portugal;3. IPMA Collaborator;4. Instituto Dom Luiz (LA), Portugal;5. UMR-CNRS 5805 EPOC, Université de Bordeaux, Allée Geoffroy St Hilaire, 33615 Pessac, France |
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| Abstract: | Shell-weight measurements were carried out on planktonic foraminifera G. sacculifer and G. ruber specimens from coretop depth transects in the Atlantic, Indian and Pacific Ocean to investigate calcite dissolution above the lysocline. The results suggest that foraminifera deposited in sediments overlain by supersaturated bottom water undergo considerable dissolution at the sediment–water interface and that the calcite saturation state at the interface is considerably offset from that of bottom water. Also, the extent of exposure to undersaturated conditions at the interface is not constant. Rather, it increases towards the surface ocean, i.e. towards shallow marine sediments where the organic matter flux is expected to be higher. It is proposed that the benthic fluff layer at the sediment–water interface represents a zone of undersaturation through which the foraminifera pass prior to deeper burial, and that the residence time of foraminifera within this zone of intense organic matter respiration is long enough to result in significant decreases in shell weight. |
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