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Source of the climate signal recorded by magnetic susceptibility variations in Indian Ocean sediments.

Research output: Contribution to journalJournal article

Published

Journal publication date1999
JournalJournal of Geophysical Research: Solid Earth
Volume104
Number of pages15
Pages5047-5061
Original languageEnglish

Abstract

The origins of magnetic susceptibility variations in deep-sea sediments from the Indian Ocean (ODP Leg 117) have been examined to identify the specific connections between climate shifts and sediment magnetic properties. In a previous study, the magnetic susceptibility variations in ODP Hole 722B were identified as an outstanding proxy paleoceanographic record, despite evidence of post-depositional loss of magnetic minerals through reductive diagenesis. This paradox is addressed by assessing the contributions of ferrimagnetic detrital iron oxides, bacterial magnetosomes, and paramagnetic detrital Fe-silicate minerals to the magnetic susceptibility signal. In addition to detailed magnetic analyses, mineralogical, morphological and grain size data have been obtained from representative magnetic extracts. For Hole 722B, magnetic responses to climate change result from: i) fluctuations in the volume magnetic susceptibility, which is primarily controlled by carbonate dilution; ii) a ferrimagnetic signal which is restricted to the upper 7 mbsf and which largely reflects source area aridity; and iii) a paramagnetic susceptibility record below 7 mbsf, which is coincident in frequency with variations in lithogenic grain size.

Bibliographic note

Copyright (1999) American Geophysical Union.