A Rock-Magnetic Record of Monsoonal Dust Deposition to the Arabian Sea: Evidence for a Shift in the Mode of Deposition at 2.4 Ma

Abstract

A detailed record of eolian deposition from the Asian monsoon has been determined from measurements of magnetic susceptibility at Sites 721 and 722 located on an elevated ridge in the western Arabian Sea. Susceptibility was measured at 5-cm intervals (1 k.y.) on whole-core sections (15,000 measurements) and these data were used to construct complete composite records extending to 3.2 Ma. The composite records at Sites 721 and 722 are virtually identical, suggesting that both are complete and without local hiatuses. Bulk X-ray diffraction analyses indicate that (eolian) quartz and dolomite abundances are strongly covariant with the susceptibility data {r = 0.83, 0.70; « = 172). An almost perfect correlation (r = 0.98; n = 94) between susceptibility and terrigenous percent (determined by sequential carbonate, opal, and organic carbon extraction) indicates that susceptibility is a rapid and sensitive tracer of terrigenous fraction variations. Furthermore, terrigenous and biogenic flux calculations indicate that the observed susceptibility variations are indeed the result of terrigenous accumulation rate variations and not dilution by variations in biogenic input.In the frequency-domain, variance is concentrated at orbital periodicities for the entire 3.2 Ma sequence; however, there is a shift in the dominant periodicity at ca. 2.4 Ma. From 3.2 to 2.4 Ma, the susceptibility data vary almost purely at 23-19 k.y. periodicities and coherency with the precessional insolation forcing is high (0.89). Strong and coherent variance at the 23-19 k.y. band is maintained after 2.4 Ma but there is a dramatic increase in variance at the 41 k.y. periodicity corresponding to orbital obliquity. The timing of this shift coincides with the initiation of Northern Hemisphere glaciation and suggests a linkage between high-and low-latitude climate processes. General circulation model experiments and paleoclimatological evidence from northeast Africa suggest that the increase in 41 k.y. power after 2.4 Ma may be reflecting periodic increases in monsoon dust source area aridity due to the coeval expansion of the Eurasian and/or North American ice sheets, which varied predominantly at this periodicity.

Source-to-sink magnetic properties of NE Saharan dust in Eastern Mediterranean marine sediments: review and paleoenvironmental implications

“…The areas that have provided the most outstanding records of eolian dust deposition based on magnetic properties are the equatorial Atlantic Ocean (Bloemendal et al, 1993;deMenocal, 1995;Maher and Dennis, 2001;Itambi et al, 2009;Just et al, 2012), the N Pacific Ocean (Doh et al, 1988;Yamazaki and Ioka, 1997;Yamazaki, 2009Yamazaki, , 2012Bailey et al, 2011), the eastern Mediterranean Sea (Dinarès-Turell et al, 2003;Larrasoaña et al, 2003a;Köhler et al, 2008;Liu et al, 2012b), the Arabian Sea (Bloemendal and deMenocal, 1989;deMenocal et al, 1991;Bloemendal et al, 1993;deMenocal, 1995;Hounslow and Maher, 1999), and the Red Sea Roberts et al, 2011) (for a review see Maher, 2011). Given the often discontinuous nature of the continental sedimentary record, these marine magnetic records of eolian dust deposition provide valuable sources of information on past climate variability in continental regions (Liu et al, 2012a).…”

Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

“…Variations in the concentration of magnetic minerals provide information on changing export of terrigenous sediments from land (DeMenocal et al, 1991;Just et al, 2012;Maher, 2011;Reynolds and King, 1995). Furthermore, variations in the composition of the magnetic mineral assemblages can be used for detecting changes in terrestrial climatic conditions, e.g., weathering and soil formation (Hu et al, 2015;Kämpf and Schwertmann, 1983;Larrasoaña et al, 2015;Lyons et al, 2010;Maher and Thompson, 1992).…”

Rock-Magnetic Properties of Pleistocene Passive Margin sediments: Environmental Change and Diagenesis offshore New Jersey

“…Most of the applications of environmental magnetism assume that a primary detrital magnetic signal is analyzed. This assumption is generally supported by correlating rock-magnetic parameters to more established sedimentological or geochemical parameters (e.g., Chave and Denham, 1979;Kent, 1982;Shackleton et al, 1984;Robinson, 1986;Bloemendal and DeMenocal, 1989;DeMenocal et al, 1991;Thouveny et al, 1994).…”