Driven by glacio-eustatic processes, the Earth has experienced a phase of large-amplitude sea-level change as intensive as any during its history since the Quaternary (Rohling et al., 2014), which has branded profound imprints in marine sediments. For example, with regard to deep-sea sediments, a remarkable feature is the variations in the oxygen isotope records of benthic foraminifera (BF), such as the well-known "LR04 stack" (Lisiecki & Raymo, 2005). Likewise, for sedimentary records on continental shelves, which serve as a link between the land and the deep ocean, sea-level fluctuations over glacial-interglacial timescales (e.g., the cycles in the Earth's orbital eccentricity of ∼100-kyr) are generally expressed as transgression-regression cycles (Shi et al., 2016). Due to their wide and gentle landforms, as well as relatively shallow water depths, continental shelves are much more sensitive to sea-level changes than abyssal regions; even trifling fluctuations in sea-level can give rise to considerable shoreline migration (Yao et al., 2020). Nevertheless, besides the easily identified transgression-regression cycles, it is difficult to trace changes in sea-level over much shorter timescales, which, however, is of great significance to human activities in coastal areas (Yang et al., 2015). This problem is more prominent in relation to sedimentary units with homogenous lithologies, especially for fine-grained sediments which are relatively poor in BF due to high sedimentation rates and
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.
While continental margins and marginal seas account for only ∼10%-20% of the global ocean area, many are located in highly dynamic regions in which elevated physical erosion, chemical weathering, and organic carbon burial play a major role in the global carbon cycle (Wan et al., 2009). Moreover, continental margins are characterized by rapid sediment accumulation, such that high-resolution records of past weathering and erosion can potentially be obtained by deciphering the geochemical and mineralogical signatures within these sedimentary
Although continental shelves account for only approximately 7.5% of the ocean's surface, they are a globally important reservoir for terrigenous sediments (Saito et al., 1998). Therefore, sedimentary records from continental shelves are ideal for high-resolution studies on geological and environmental evolutions such as local tectonic subsidence, source-sink processes, and climate changes (e.g., Knies et al., 2003). In addition, as a transitional zone between the land and deep ocean, sedimentary architectures on the continental shelf, especially in low-gradient and broad continental margins, are controlled by a range of factors including variations in sea-level
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