Magnetic properties of pelagic marine carbonates

Autor(es)

Roberts, Andrew P. ^[1] ; Florindo, Fabio ^{[2, 3]} ; Chang, Liao ^[1] ; Heslop, David ^[1] ; Jovane, Luigi ; Larrasoana, Juan C. ^[4]

Afiliação do(s) autor(es)

^[1] Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 0200 - Australia

^[2] Ist Nazl Geofis & Vulcanol, I-00143 Rome - Italy

^[3] Univ Sao Paulo, Inst Oceanog, Dept Oceanog Fis, BR-05508120 Sao Paulo - Brazil

^[4] Inst Geol Miner Espana, Unidad Zaragoza, Zaragoza 50006 - Spain

• Tipo de documento: Artigo Científico
• Fonte: EARTH-SCIENCE REVIEWS; v. 127, p. 111-139, DEC 2013.
• Citações Web of Science: 53

Resumo

Pelagic carbonates are deposited far from continents, usually at water depths of 3000-6000 m, at rates below 10 cm/kyr, and are a globally important sediment type. Recent advances, with recognition of widespread preservation of biogenic magnetite (the inorganic remains of magnetotactic bacteria), have fundamentally changed our understanding of the magnetic properties of pelagic carbonates. We review evidence for the magnetic minerals typically preserved in pelagic carbonates, the effects of magnetic mineral diagenesis on paleomagnetic and environmental magnetic records of pelagic carbonates, and what magnetic properties can tell us about the open-ocean environments in which pelagic carbonates are deposited. We also discuss briefly late diagenetic remagnetisations recorded by some carbonates. Despite recent advances in our knowledge of these phenomena, much remains undiscovered. We are only at early stages of understanding how biogenic magnetite gives rise to paleomagnetic signals in sediments and whether it carries a poorly understood biogeochemical remanent magnetisation. Recently developed techniques have potential for testing how different magnetotactic bacterial species, which produce different magnetite morphologies, respond to changing nutrient and oxygenation conditions. Future work needs to test whether it is possible to develop proxies for ancient nutrient conditions from well-calibrated modem magnetotactic bacterial occurrences. A tantalizing link between giant magnetofossils and Paleogene hyperthermal events needs to be tested; much remains to be learned about the relationship between climate and the organisms that biomineralised these large and novel magnetite morphologies. Rather than being a well-worn subject that has been studied for over 60 years, the magnetic properties of pelagic carbonates hold many secrets that await discovery. (C) 2013 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 11/22018-3 - Avaliação da produtividade primária marinha através do estudo das bactérias magnetotáticas em sedimentos
• Beneficiário: Luigi Jovane
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores