Holocene sedimentation in the Hupo Trough of the southwestern East Sea (Japan Sea) and development of the East Korea Warm Current

Abstract

Various sediment properties, such as mean grain size, total organic carbon, total nitrogen, C/N ratio, CaCO3, and biogenic opal content, were analyzed for a box core (BC02; 45 cm long) and a gravity core (GC02; 628 cm long), which were collected from the western margin of the Hupo Trough located off the eastern coast of Korea. The study area has been affected by the East Korea Warm Current (EKWC), a branch of the Tsushima Warm Current (TWC). The analytical results obtained for BC02 and the upper part of GC02 were in agreement, affirming the core-top preservation of GC02. Based on the corrected calibrated AMS 14C dates, the sedimentation rate of GC02 changed abruptly at ~8.2 ka from ~4.0–10.2 cm/kyr in the lower part to ~56.6–91.0 cm/kyr in the middle to upper part. This corresponds to the lithologic change from sandy mud to mud sediments showing the mean grain size change from 6.9 to 46.0 μm. Diverse paleoceanographic proxies representing the surface water condition exhibited varying degree of change at ~8.2 ka, after which all the properties remain almost unchanged, implying stable and continuous depositional conditions following the complete development of the EKWC. Furthermore, it indicated that the sediment depositional conditions in the Hupo Trough in response to the EKWC might have stabilized at ~8.2 ka since the opening of the Korea Strait during the Holocene sea level rise. Moreover, microfossil data from previous studies on the establishment of the TWC in the East Sea (Japan Sea) support our interpretation that the sediment properties revealed the Holocene development of the EKWC in the Hupo Trough.

Natural peloids originating from subsea depths of 200 m in the hupo basin, South Korea: physicochemical properties for potential pelotherapy applications

“…Previous studies on surface sediments in the Hupo Basin demonstrate agreement with our findings regarding mineral composition and particle size distribution at various locations (Fig. 1 c) (Jun et al, 2014 ; Khim et al, 2021 ; Lee et al, 2015 ). Additionally, through comparison of surface sediments at depths of 200 m and 120–170 m in the Hupo Basin, it was determined that the uppermost sediments with a minimum thickness of 4 m at both locations originated from hemipelagic sources, exhibiting similar mineralogical and geochemical features (Fig.…”

“…3 a). Compared with other peloids, the relatively small particle size of the samples was due to the geological conditions of the sedimentary environment, where the input of terrestrial sediments was strictly limited (Khim et al, 2021 ). Furthermore, as previously demonstrated, smaller clay particles are associated with slower cooling (Berbenni, 1965 ), suggesting that the studied sediment might possess improved thermal properties.…”

“…Sampling was performed by deploying the piston core at the corner points of the rectangular area and box core at the center of the rectangular area to assess the uniformity of surface sediment and distribution area of peloid deposits. The green circles represent prior research locations in the Hupo Basin (Jun et al, 2014 ; Khim et al, 2021 ; Lee et al, 2015 ) …”

“…The surface sediment in the study area was considered to originate primarily from the transport by ocean currents, particularly the East Korean Warm Current (EKWC) and North Korean Cold Current (NKCC; Fig. 2 a) (Hong et al, 2022 ; Khim et al, 2021 ) because most rivers capable of transporting sediment to the East Sea are short and small, and terrestrial sediments tend to accumulate within the shallow continental shelf, thus limiting the supply of terrestrial input (Khim et al, 2021 ).

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“…First, it is geologically isolated from various anthropogenic sources of contamination. Second, the seafloor surface sediments in the Hupo basin have previously been extensively investigated through depositional and geochemical analyses, providing valuable background information for assessing their potential application as peloids (Hong et al, 2022 ; Khim et al, 2021 ; Kim et al, 2010 ; Lee et al, 2015 ; Son et al, 2022 ). Third, box/piston core analyses have confirmed that these sediments have a consistent composition across a wide area.…”