Benthic foraminiferal successions across Late Quaternary Mediterranean sapropels |
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| Institution: | 1. Institute of Earth Sciences, University of Graz, NAWI Graz Geocenter, Heinrichstrasse 26, 8010 Graz, Austria;2. Department of Geology, University of Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain;3. Department of Biogeosciences, JAMSTEC, Yokosuka 237-0061, Japan;4. International Ocean Discovery Program, Texas A&M University, College Station, TX 77845, USA;1. Departamento de Oceanografia Física, Química e Geológica do Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico, 191, 05508-120 São Paulo, SP, Brazil;2. Fundação de Desenvolvimento Tecnológico da Engenharia, Rua Catequese, 227, 3° andar, 0552-020 São Paulo, SP, Brazil;3. Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Departamento de Estratigrafia e Paleontologia, Av. São Francisco Xavier, 524, sala 2020A, Maracanã, 20550-013 Rio de Janeiro, RJ, Brazil;4. Universidade de Aveiro, GeoBioTec, Departamento de Geociências, Campus de Santiago, 3810-193 Aveiro, Portugal;5. Centro de Estudos do Mar, Universidade Federal do Paraná, AV. Beira Mar, s/n. Pontal do Paraná, Paraná, Brazil;6. Dipartimento di Scienze Pure e Applicate Università degli Studi di Urbino “Carlo Bo”, Piazza della Repubblica, 13, 61029 Urbino, Italy;7. Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay;8. Pontifícia Universidade Católica do Rio de Janeiro, Marquês de São Vicente, 225 – Gávea, 22451-900 Rio de Janeiro, RJ, Brazil;9. Laboratório de Ciências Ambientais, Centro de Biociências e Tecnologia, Universidade Estadual do Norte Fluminense, Av. Alberto Lamego, 2000, Campos dos Goytacazes, 28015-620 Rio de Janeiro, RJ, Brazil;10. Institut für Geowissenschaften, Universität Heidelberg, Heidelberg, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany;1. Micropaleontology Laboratory, Geological Oceanography Division, National Institute of Oceanography, Goa, India;2. National Center for Polar and Ocean Research, Goa, India;1. Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain;2. Instituto Universitario de Ciencias Ambientales, Universidad de Zaragoza, Zaragoza, Spain |
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| Abstract: | Benthic foraminiferal records across Late Quaternary Mediterranean sapropels S6, S5 and S1 are reviewed and re-considered in the light of recent advances in foraminiferal ecology. It is suggested that the main factor controlling the foraminiferal successions that occur immediately before and after sapropel deposition is the amount of time involved in the onset of anoxic conditions and in the re-oxygenation of the benthic environment. Faunas dominated by deep infaunal taxa such as Globobulimina and Chilostomella reflect a very gradual decrease or increase of bottom water oxygenation. Post-sapropel faunas dominated by small biconvex, trochospiral taxa, which are inferred to have a much more opportunistic life strategy, are typical of a very rapid re-oxygenation of the benthic environment after sapropel deposition. The time involved in re-oxygenation depends upon the mechanism causing sapropel formation. The faunal succession found above sapropel S5 suggests a basin with a strong density gradient in the upper part of the water column during sapropel deposition, followed by a rapid turnover of the following column and quick re-oxygenation of the benthic environment. In contrast, the faunal succession above sapropel S6 suggests a water column with a more gradual density gradient deeper in the basin, a progressive deepening of the halocline, and a very slow increase of bottom water oxygenation. |
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