Abstract
As the northwest Pacific has been subject to varying terrigenous input linked to paleoclimate change, the concentration of magnetic minerals in deep-sea sediments is often utilized as a proxy to reconstruct the past atmospheric circulation in the Northern hemisphere. Volcanic materials account for a significant portion of the terrigenous input, but their contribution to sedimentary magnetic properties has not been carefully investigated. This study reveals the magnetic contribution and characteristics of volcanic materials, based on particle-size specific magnetic measurements on sediments that span the last 400 kyr for five size-fractions, including ranges typically attributed to fine eolian ( 100 mT) magnetic minerals, showing an increased portion of 32–74%. From coercivity spectra analysis, the coarse volcanic fractions are characterized by an abundance of the ~100 mT coercivity minerals, which can result in an increased average coercivity of bulk sediments. Around the study area, magnetic susceptibility records show synchronized variations with volcanic proportions in terrigenous sediments, validating their close relationship. Consequently, our results indicate that volcanic materials have a high potency of magnetic concentration, which can control bulk sedimentary signals in the northwest Pacific.
Highlights
Mineral dust in the North Pacific, including iron oxides, is transported mainly from the Asian inland by westerly winds (Rea et al, 1998)
Magnetic concentration parameters (SIRM, anhysteretic remanent magnetization (ARM), HIRM100, and HIRM300) of size-fractionated samples were normalized by mass, and multiplied by each mass fraction (f ); representing massnormalized and mass-weighted values, respectively
The massnormalized values are generally higher in coarser fractions which take small portions in total mass (Supplementary Figure S1), indicating higher magnetic concentration
Summary
Mineral dust in the North Pacific, including iron oxides, is transported mainly from the Asian inland by westerly winds (Rea et al, 1998). An increased concentration of magnetic minerals in sediments, of high coercivity minerals. Magnetic mineral concentration in North Pacific sediments shows a good correlation with the global oxygen isotope stack (e.g., LR04; Lisiecki and Raymo, 2005) during the Pleistocene, with its decrease or increase during colder or warmer periods, respectively (e.g., Yamazaki, 1999; Yamamoto et al, 2007; Kars et al, 2017). As an explanation for the cyclicity of the magnetic concentration, various factors have been suggested: glacial enhancement of dust input with high coercivity minerals (Doh et al, 1988), fossilized biogenic magnetite contribution relative to dust input (Yamazaki, 2009), and non-steady state diagenesis with glacial magnetite dissolution (Korff et al, 2016; Shin et al, 2018). The relationship between terrigenous input and magnetic concentration in orbital timescales is still unclear
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