Asian monsoon modulation of nonsteady state diagenesis in hemipelagic marine sediments offshore of Japan

Abstract

We have identified millennial-scale variations in magnetic mineral diagenesis from Pacific Ocean sediments offshore of Japan that we correlate with changes in organic carbon burial that were likely driven by Asian monsoon fluctuations. The correlation was determined by identifying offsets between the positions of fossil diagenetic fronts and climatically induced variations in organic carbon burial inferred from magnetic and geochemical analyses. Episodes of intense monsoon activity and attendant sediment magnetic mineral diagenesis also appear to correlate with Heinrich events, which supports the existence of climatic telecommunications between Asia and the North Atlantic region. Several lines of evidence support our conclusions: (1) fluctuations in down-core magnetic properties and diagenetic pyrite precipitation are approximately coeval; (2) localized stratigraphic intervals with relatively stronger magnetic mineral dissolution are linked to enhanced sedimentary organic carbon contents that gave rise to nonsteady state diagenesis; (3) down-core variations in elemental S content provide a proxy for nonsteady state diagenesis that correlate with key records of Asian monsoon variations; and (4) relict titanomagnetite that is preserved as inclusions within silicate particles, rather than secondary authigenic phases (e.g., greigite), dominates the strongly diagenetically altered sediment intervals and are protected against sulfidic dissolution. We suggest that such millennial-scale environmental modulation of nonsteady state diagenesis (that creates a temporal diagenetic filter and relict magnetic mineral signatures) is likely to be common in organic-rich hemipelagic sedimentary settings with rapidly varying depositional conditions. Our work also demonstrates the usefulness of magnetic mineral inclusions for recording important environmental magnetic signals.

Signatures of Reductive Magnetic Mineral Diagenesis From Unmixing of First‐Order Reversal Curves

“…Many studies of coastal, hemipelagic, and pelagic sediments document progressive down‐core diagenetic dissolution of detrital iron oxides in reducing environments (Bouilloux et al, ; Chang, Bolton, et al, ; Channell & Hawthorne, ; Dillon & Bleil, ; Emiroglu et al, ; Garming et al, ; Karlin, , ; Karlin & Levi, , ; Kawamura et al, ; Leslie, Hammond, et al, ; Leslie, Lund, et al, ; Liu et al, ; Mohamed et al, ; Rey et al, ; Richter et al, ; Riedinger et al, ; Roberts, ; Roberts & Turner, ; Robinson et al, ; Rowan et al, ; Yamazaki et al, ). These studies provide a common picture of surface sediments, generally with all stages of organic matter diagenesis recognized in pore water profiles (Figure ; Roberts, ).…”

Widespread occurrence of silicate‐hosted magnetic mineral inclusions in marine sediments and their contribution to paleomagnetic recording

“…LT warming of SIRM reveals a weak double Verwey transition ( T v ) signature (Figure b) that is indicative of the presence of small amounts of both biogenic and inorganic magnetite [e.g., Chang et al ., ], where the more pronounced T v at ~120 K is mostly likely to be associated with the presence of detrital magnetite. It should be noted that the double T v signature is not observed commonly for other sediment samples from core MD01‐2421 [ Chang et al ., ]. The FORC diagram for sample RR0603‐03JC‐2‐60 from the central equatorial Pacific Ocean contains a dominant central‐ridge signature associated with noninteracting SD particles, superposed on a weak background SD signal with stronger interactions (Figure c).…”

“…Our detailed TEM observations indicate that magnetic nanoparticle inclusions are widely present in marine sediments. Magnetic inclusions can even dominate the magnetic signal (Figure a) [ Chang et al ., ]. The observed magnetic mineral microstructures have two main origins due to exsolution and inclusion (see Tarduno et al [] for a discussion).…”

“…Marine sediment samples from a range of deep‐sea sediment cores and sediment outcrops were investigated in this study (Figure ). Core MD01‐2421 (36°01.4′N, 141°46.8′E; 2224 m water depth; 45.82 m long) was recovered from the North Pacific Ocean ~100 km offshore of central Japan [ Oba et al ., ; Chang et al ., ]. Sediments in this core are homogenous olive‐gray silty clays with calcareous and siliceous microfossils, with high total organic carbon (TOC) content (0.5–2.1 wt % [ Ueshima et al ., ]).…”

Measuring, Processing, and Analyzing Hysteresis Data

“…The use of magnetic hysteresis data is prevalent throughout paleomagnetic and Earth science studies. It has applications in fundamental rock magnetism (Krása et al, ; Williams et al, ), analyzing paleointensity data (Carvallo et al, ; Haag et al, ; Kissel et al, ; Paterson et al, , ), paleoclimate and paleoenvironmental studies (Chang et al, ; Hatfield et al, ; Liu et al, ; R. Zhang et al, ), biomagnetism (J. Li et al, ; Lin & Pan, ; Pan et al, ), tectonics (Jackson & Swanson‐Hysell, ; S. Li et al, ; Van Hinsbergen et al, ), pollution monitoring (Muxworthy et al, ; C. Zhang et al, ), and extraterrestrial magnetism (Muxworthy et al, ; Tikoo et al, ), among many others. Despite this widespread usage, the analysis of hysteresis data can be nontrivial, and detrimental effects on the quality and accuracy of hysteresis data, such as off‐center loops and drift are routinely unaccounted for (Jackson & Solheid, ).…”