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Although sea‐level is the primary control over sedimentary architectures on continental shelves, deciphering such changes is still challenging, except for the easily recognized transgression‐regression cycles. This problem becomes more prominent in sedimentary units with relatively homogenous and fine‐grained lithologies that have been deposited over short periods. Here, we focus on a dominantly clayey silt section of a sediment core from the outer shelf of the East China Sea. Detailed rock magnetic and electron microscopy analyses indicate that authigenic greigite (Fe3S4) is the major magnetic component in an almost 4‐m‐thick interval that was deposited during the late Marine Isotope Stage (MIS) 3, while pyrite (FeS2) is enriched in the underlying middle MIS 3 sediments. According to microfossil analyses, the identified greigite formed in a prodelta setting that was affected by cold coastal currents after the middle MIS 3, when the Taiwan Warm Current and its associated upwelling were prevailing within a middle‐outer shelf setting favorable for pyrite formation. Large‐amplitude regression occurred subsequently during the MIS 2, limiting sulfate supply and favoring the greigite preservation. Our results, along with the previous studies, demonstrate that both the material and environmental conditions that are crucial to iron sulfide survival have been largely controlled by sea‐level change. Moreover, we make a preliminary proposition that a water depth range of 30–60 m is more likely to lead to the enrichment of greigite on continental shelves. We, therefore, provide a promising avenue for the assessment of sea‐level change on continental shelves over orbital and even suborbital timescales. Key Points: Greigite was identified as the major magnetic mineral in almost 4‐m‐thick late MIS 3 sediments from the outer shelf of the East China SeaAuthigenic greigite and pyrite have great potential to indicate sea‐level change on continental shelves even on suborbital timescalesWater depths of 30–60 m are likely to be more suitable for extensive formation and preservation of greigite in continental shelf sediments [ABSTRACT FROM AUTHOR]

There are two distinctly different views on Quaternary sedimentation rates in the central Arctic Ocean, namely, that they were on cm/kyr or on mm/kyr scales, largely as a result of divergent interpretations of magnetic reversal stratigraphy. This study provides new evidence to help resolve this controversy in the form of an almost 1‐m‐thick negative polarity interval located at ~1.15 m below the seafloor in a 4.15‐m‐long sediment core from the Lomonosov Ridge, central Arctic Ocean. This thick polarity anomaly was first revealed through alternating field demagnetization of natural remanent magnetization on u‐channel samples. It was subsequently confirmed to be an authentic signal of a syndepositional geomagnetic field by integrating detailed rock magnetic studies, transmission electron microscopy with energy‐dispersive X‐ray spectroscopy analyses of magnetic extracts, and both alternating field and thermal demagnetization of discrete paleomagnetic samples. Here we conclude that it is more reasonable to interpret the reversed interval as a record of the Matuyama Chron rather than a Brunhes‐aged excursion, which yields mean sedimentation rates of ~1.5 mm/kyr and ~0.5 mm/kyr in the Brunhes and Matuyama Chrons, respectively. These estimates are remarkably lower than assumed in most recent studies, but in good agreement with both previous magnetostratigraphic and recent geochemical studies relative to the decay of Be and U‐series isotopes, which might indicate "sediment‐starved" environments at least in some parts of this region. Overall, our results not only imply that chronostratigraphy in the central Arctic Ocean remains open to debate but also warrant further investigations in this microfossil‐barren region. Key Points: The effects of self‐reversed CRM of diagenetic titanomaghemite are probably only regional in the central Arctic sedimentsThe "reversal" interpretation supports "sediment starved" environments at least in some regions of the central Arctic OceanThe chronostratigraphy and usability of paleomagnetism in the central Arctic Ocean remains open to debate and further studies are warranted [ABSTRACT FROM AUTHOR]

The anhysteretic remanent magnetization (ARM) is an important magnetic parameter for quantifying the concentration of "fine", mostly sub‐micron ferrimagnetic particles in rocks and sediments. A sound understanding of ARM carriers is needed to interpret magnetic and environmental information in sedimentary archives. This is often not achieved for marine sediments, which routinely contain several magnetic mineral components. Here, we analyze marine sediment records over different timescales for four sediment cores from the Eastern Pacific Ocean (Hole 1218A), the Antarctic margin (core P4‐1), the Arctic Ocean (core ARC5‐ICE4), and the South China Sea (core L07), using coercivity spectra analyses of ARM, first‐order reversal curve principal component analysis (FORC‐PCA), transmission electron microscopy (TEM), and unmixing of isothermal remanent magnetization (IRM) curves. By combining rock magnetic and TEM results, we find that the ARM is mainly carried by non‐interacting single domain (SD) biogenic magnetite (magnetofossils) in the studied sediments over all timescales. Low‐coercivity magnetic particles (detrital and fine‐grained extracellular magnetite) also contribute to the bulk ARM. Variable magnetofossil chain structures are detected and have a significant influence on ARM data interpretation. Quantitative FORC‐PCA endmember analyses based on quantile contours and coercivity distributions provide valuable information on the nature of endmembers and improve ARM data interpretation. We provide an integrated strategy to help reduce interpretational ambiguities related to ARM in future studies. Plain Language Summary: The anhysteretic remanent magnetization (ARM) is an important parameter that is used to assess information about Earth's magnetic field variations and environmental changes. To interpret ARM signals robustly, we must understand the sedimentary magnetic minerals that control ARM changes. However, the origin of ARM changes in marine sediments is not well understood. Here, we analyze marine sediment records from the Eastern Pacific Ocean, the Antarctic margin, the Arctic Ocean, and the South China Sea to identify the carriers of ARM in the respective sediments. Our results indicate that all of the sediments contain abundant remains of magnetotactic bacteria (known as magnetofossils). Magnetofossil abundance variations dominate ARM on both 10,000 to million‐year timescales. Part of the bulk ARM is also contributed by other low‐coercivity magnetite particles. Furthermore, ARM is influenced significantly by magnetofossil chain structure variations. Our results have important implications for future studies involving use of ARM in magnetofossil‐rich sediments. Key Points: Integrated component analyses are presented for four sediment cores to identify magnetic particle sourcesMagnetofossils are the predominant anhysteretic remanent magnetization (ARM) carrier with detrital and extracellular magnetite also contributing to the ARMQuantitative analyses provide valuable insights into the nature of components to improve ARM data interpretation of marine sediments [ABSTRACT FROM AUTHOR]

North Pacific Ocean sediments are important archives of geomagnetic field and paleoenvironmental evolutions, yet late Quaternary sedimentary sequences in the North Pacific Ocean are less explored because of generally low sedimentation rates and the challenge of dating sediments deposited below the calcite compensation depth. Core NP02 sediments from the North Pacific Ocean contain three visible tephra layers, which are identified as the To‐Of, Spfa‐1, and Kt‐3 tephra, respectively. An age model for core NP02 is established based on tephra correlation and one radiocarbon date, which gives a mean sedimentation rate of ∼11.6 cm/kyr. Magnetic analyses suggest the dominance of two remanence carriers; detrital vortex state and biogenic single domain magnetite. Variable depth offsets between the relative paleointensity (RPI) signals carried by the two remanence carriers adds a negligible age error (<0.5 kyr) to the core NP02 RPI record. Pronounced RPI amplitude variations are observed, and the Rockall and Laschamp excursions are identified in the core NP02 RPI record based on the age model. The fidelity of the core NP02 RPI record is further verified by comparison with other RPI stacks and records, and we demonstrate that the RPI variations can assist in chronology refinement. Plain Language Summary: The North Pacific Ocean is too deep to preserve materials effectively for the oxygen isotope chronology, and sediments deposit slowly in this region. Therefore, dating is a big problem for late Quaternary sedimentary cores. In this study, core NP02 sediments from the North Pacific Ocean are studied. The To‐Of, Spfa‐1, and Kt‐3 tephra layers are identified in core NP02 sediments based on the geochemical features. An age model for this core is reconstructed with the aid of tephra ages and one radiocarbon date. Magnetic analyses suggest that both small biogenic and relatively large detrital magnetite record geomagnetic information, and the two groups of magnetite deposit at about the same time. Based on the age model, core NP02 RPI record preserves the Rockall and Laschamp excursions, and the RPI pattern is consistent with other RPI stacks and records, which verifies core NP02 RPI fidelity. Therefore, we demonstrate that RPI variations is a promising dating tool for North Pacific Ocean sediments. Key Points: We use an age model based on tephra correlation and one radiocarbon date to assess the fidelity of relative paleointensity variationsDetrital vortex state and biogenic single domain magnetite are the dominant remanence carriers, and they introduced <0.5 kyr age errorAssessment of component‐specific magnetic properties should be considered to ensure the reliability of relative paleointensity variations [ABSTRACT FROM AUTHOR]