Magnetic Properties of a Holocene Sediment Core from the Yeongsan Estuary, Southwest Korea: Implications for Diagenetic Effects and Availability as Paleoenvironmental Proxies

Abstract

The sensitivity of magnetic properties, which characterize the mineralogy, concentration, and grain size distribution of magnetic minerals, to environmental processes may provide useful information on paleoenvironmental changes in estuarine environments. Magnetic property studies of estuaries are less common than other environments and, due to the west coast of South Korea having an abundance of estuaries, it provides a good place to study these processes. In this study, we analyzed a variety of magnetic properties based on magnetic susceptibility, hysteresis parameters, progressive acquisition of isothermal remanent magnetization and first-order reversal curve data from a Holocene muddy sediment core recovered from the Yeongsan Estuary on the west coast of South Korea. We examined diagenetic effects on magnetic properties and tested their availability as proxies of paleoenvironmental change. The presence of generally low magnetic susceptibility, ubiquitous greigite-like authigenic magnetic component, and very fine magnetic particle occurrence suggested that the analyzed sediments had undergone considerable early diagenetic alteration. Electron microscopic observations of magnetic minerals support this suggestion. Our results confirm that the use of initial bulk susceptibility as a stand-alone environmental change proxy is not recommended unless it is supported by additional magnetic analyses. We recognized the existence of ferromagnetic-based variabilities related to something besides the adverse diagenetic effects, and have examined possible relationships with sea-level and major climate changes during the Holocene. The most remarkable finding of this study is the two distinct intervals with high values in magnetic coercivity (Bc), coercivity of remanence (Bcr), and ratio of remanent saturation moment to saturation moment (Mrs/Ms) that were well coincident with the respective abrupt decelerations in the rate of sea-level rise occurred at around 8.2 and 7 thousand years ago. It is then inferred that such condition with abrupt drop in sea-level rise rate would be favorable for the abrupt modification of grain size distribution toward more single-domain-like content. We modestly propose consideration of the Bc, Bcr, and Mrs/Ms variability as a potential indicator for the initiation/occurrence of sea-level stillstand/slowstand or highstand during the Holocence, at least at estuarine environments in and around the studied area.

Study of the disaster-causing mechanism and reinforcement measures for soft rock deformation and lining cracking

“…The water-rock physicochemical reaction intensified, resulting in the strength degradation of the surrounding rock (Yang et al, 2022) and inducing uncoordinated surrounding rock deformation and cracking of the lining. Three cores were drilled in the collapsed tunnel section for laboratory tests to obtain the mineral composition and expansion (Ahn et al, 2021;. The results are shown in Table 2.…”

Control of Source‐To‐Sink Processes on the Dispersal, Fractionation, and Deposition of Magnetic Minerals in a Tropical Mesotidal Estuarine System

“…Easy detection of geological and hydrodynamic processes by magnetic methods makes magnetic minerals, an exemplary proxy to gain vital insights into the dynamics of magnetic particles in sedimentary systems (Hatfield, 2014; Kulgemeyer et al., 2017). Magnetic methods have been increasingly used to study the estuarine and coastal systems for example, to decipher the origin, and dynamics of heavy (magnetic) minerals (Gallaway et al., 2012; Hatfield et al., 2010; Kulgemeyer et al., 2017), identify the sediment accretion and erosion sites (Franke et al., 2020; Hatfield et al., 2010; Kayvantash et al., 2017; Wang et al., 2011), track changes in sediment provenance, transport pathways, and depositional system (Booth et al., 2005; Hatfield, 2014; Maher et al., 2009; Prizomwala et al., 2013), map the heavy (magnetic) mineral deposits (Badesab et al., 2012; Troch et al., 2021), reconstruct the pollution history (Blaha et al., 2011), characterize the sedimentary environment and littoral drift system (Chaparro et al., 2017; Hatfield & Maher, 2008, 2009; Kulgemeyer et al., 2016), and investigate the magnetic mineral diagenesis (Ahn et al., 2021; Zhang et al., 2001).…”

Investigations of Metal Pollution in Road Dust of Steel Industrial Area and Application of Magnetic Separation

“…These metals exist in various chemical forms, such as carbonate minerals and oxide minerals, and are adsorbed on the surface of particles and bound with organic matter. Magnetic properties are one of the major physical properties of rocks, soils, and sediments, and are widely used in geological and environmental studies, such as the determination of past climates and the origin of sediments [1][2][3]. Because some metal elements have a high correlation with magnetic susceptibility and behave with Fe-Mn oxides, these properties are actively used in environmental research, such as tracing the origin of metal contamination in the environment and the treatment of metal contamination in water and soil [4][5][6][7][8][9].…”