https://repository.kopri.re.kr/handle/201206/4804 Thu, 05 Mar 2026 07:02:19 GMT 2026-03-05T07:02:19Z https://repository.kopri.re.kr/handle/201206/16471 Title: Grain-size and geochemical evidence for sediment transport mechanisms in the northeastern part of the East Siberian Sea and on the adjacent continental slope Authors: Ovsepyan Ekaterina; Dorokhova Evgeniia; Ovsepyan Yaroslav; Aliev Ramiz; Jin, Young Keun Abstract: Grain-size analyses, end-member modeling, X-ray fluorescence, and radionuclide activity measurements were conducted on sediment minicores collected from the middle-outer shelf of the East Siberian Sea (ESS) and the upper part of the adjacent continental slope to elucidate the sedimentation mechanisms in this poorly studied region. The grain-size data demonstrate that clayey silt and silt strongly dominate on the ESS shelf and the continental slope. In contrast, sandy silt has a patchy distribution. End-member modeling, applied here for the first time, indicates that sea ice (frazil and anchor ice) rafting, and nepheloid transport are the primary processes responsible for distributing sedimentary material across the ESS. The XRF data confirm the results of previous studies, reporting a predominantly lithogenic origin for ESS deposits. Combined grain size and geochemical records suggests that the shelf break area serves as a depocenter for fine silt particles, likely supplied by nepheloid flow, and represents the most productive area in the northeastern ESS. High sea surface productivity likely results from influence of nutrient-rich Pacific-derived waters, the upwelling of transformed Atlanticderived waters, or a combination of both. The accumulation of the high amount of fine silt near the shelf break is suggested to be related to relatively calm bottom-water conditions, resulting from the potential interaction of the northward-flowing cross-shelf currents and episodic southward-moving compensatory flows. Wind direction is considered a key factor controlling the intensity of fine-grained material distribution by nepheloid flows and anchor ice across the ESS shelf. Sedimentation rates derived from the radionuclide activity measurements vary from 1.3 mm yr(-1) on the outer shelf to 1.0 mm yr(-1) on the upper continental slope. Mon, 01 Dec 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16471 2025-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16482 Title: Unlocking Martian geology with Martian meteorites Authors: Park, Changkun Abstract: 화성 운석은 현재 지구에서 확보할 수 있는 유일한 화성 암석으로, 화성의 지질 진화를 해석하는 데 핵심적인 단서를 제공한다. 지금까지 보고된 화성 운석은 셔고타이트(shergottite), 나클라이트(nakhlite), 샤시그나이트(chassignite), 사방휘석암(orthopyroxenite), 다성분 표토 각력암(polymict regolith breccia)으로 구분되며, 형성 시기와 암석학적 특징이 다양해 초기 지각부터 최근의화산 활동에 이르기까지 폭넓은 지질 시대를 포괄한다. 이들 운석의 충격 용융 유리에 포획된 가스 성분, 삼중 산소 동위원소 조성비, 감람석과 휘석의 Mn/Fe 비 등이 화성 기원의 주된 증거로 사용된다. 화성 운석에 대한 단반감기 동위원소 및 미량원소 분석을통해, 화성은 태양계 초기에 빠르게 집적되고 분화되었으며, 여러 맨틀 저장소(mantle reservoir)가 장기간 유지되면서 화산 활동이수십억 년 지속되었음이 밝혀졌다. 수성 변질 광물과 수소 동위원소비는 과거 화성에 액체 상태의 물이 존재했으며, 시간이 지나면서 물이 점차 소실되었음을 보여준다. 일부 운석에서 물？암석 반응으로 생성된 유기물과 수화 광물이 보고되었으나, 현재로서는비생물적 기원의 산물로 해석된다. 우주선 노출연대와 충돌 방출 모델링은 방출 기작과 기원 충돌구를 규명하는 데 활용되며, 화성표면 지질과 운석 자료를 이어 주는 중요한 연결 고리 역할을 한다. 현재 추진 중인 화성 시료 회수 임무는 운석 기록이 지닌 불완전한 지질학적 정보와 대표성의 한계를 보완함으로써, 운석 연구 성과와 결합하여 화성의 지질 진화 과정을 보다 정밀하게 재구성하는 데 기여할 것으로 기대된다. Mon, 01 Dec 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16482 2025-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16466 Title: Genesis of shallow-water manganese nodules with uniquely high Mn/Fe ratios Authors: Koo Hyo Jin; Cho Hyen Goo; Jin, Young Keun; Lee Dong-Hun; Kim Ji-Hoon; Rhee, Tae Siek; Hong, Jong Kuk; Lee Sung Keun Abstract: While manganese (Mn) nodules are authigenic metal concretions that form predominantly on deep-sea seafloor, they have also been found along shallow seafloors. The formation environments of these nodules - deep sea vs. shallow water - often result in distinct chemical and morphological characteristics. As Mn is one of the essential components of energy-storing technologies, assessing the proper estimation of Mn and metal contents in both deep-and shallow-water Mn nodules is critical. It has been found that the Mn content of shallow-water nodules is often lower than that from deep-sea environments. Here, we report the discovery of shallow-water Mn nodules with exceptionally high Mn/Fe ratios on the continental slope of the East Siberian Sea, Arctic Ocean. Despite their shallow-water origin, Mn nodules show morphological and chemical characteristics that are typically unique to deep-sea nodules. These distinctive features, including exceptionally high Mn/Fe ratios, may reflect suboxic diagenesis and the preferential remobilization and re-precipitation of Mn from the adjacent continental shelf. The formation of high Mn/Fe nodules may reflect unique ocean circulation patterns that provided oxygenated bottom waters to the study area. Particularly, Pacific Water entering through the Bering Strait, which overlaps with the nodule formation depth (160-240 m) and is enriched in dissolved oxygen, could facilitate Mn-rich nodule growth under suboxic diagenetic conditions since the Holocene. Shallow-water Mn nodules with uniquely high Mn/Fe ratios may offer a novel paleo-environmental proxy for reconstructing paleohydrology and biogeochemical evolutions in shallow marine environments. (c) 2025 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Mon, 01 Dec 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16466 2025-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16605 Title: Early aculiferan diversification shaped by Ægir-Iapetus palaeogeography: Insights from North Greenland (Cambrian Series 2, Stage 4) Authors: Oh, Yeongju; Park, Tae-Yoon S.; Peel John S. Abstract: Aculifera, comprising Polyplacophora (chitons) and Aplacophora, is one of two major molluscan clades, characterised by a scleritome of mineralised sclerites or plates. Their early evolutionary history is poorly understood due to sparse fossil records bridging possible Terreneuvian (early Cambrian) stem-group taxa and Furongian (late Cambrian) chiton-like articulated representatives. Here, we describe seven species in five genera from the Aftenstjernes & oslash; Formation (Cambrian Series 2, Stage 4) of North Greenland, including a second species, Qaleruaqia bronlundensis sp. nov., of the oldest paleoloricate, Qaleruaqia sp.; the sachitid Hippopharangites groenlandicus, Hippopharangites? sp.; a possible intermediate plate of a chiton-like scleritome, Avannaplax midsommersoensis gen. et sp. nov.; and possible aculiferans Ocruranus? kangerluk and Xianfengella yatesi. Morphological comparisons of the North Greenland assemblage reveal strong affinities with Terreneuvian taxa, including maikhanellids and the Ocruranus-Eohalobia group, supporting their interpretation as stem-group aculiferans. A palaeobiogeographic analysis using 650 global occurrences of Cambro-Ordovician taxa shows that the AE gir Ocean as a principal dispersal corridor for early diversification of aculifera. During the Terreneuvian, aculiferans were widespread along AE gir margins but rare in Laurentia, likely due to isolation by the Iapetus Ocean. From Cambrian Series 2 onward, increased connectivity and expanded low-latitude carbonate platforms fostered diversification in eastern Laurentia, including North Greenland. This assemblage from North Greenland bridges a critical spatio-temporal and morphological gap between the earliest Cambrian taxa and Furongian paleoloricates, offering new insight into aculiferan diversification and palaeobiogeography. Mon, 01 Dec 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16605 2025-12-01T00:00:00Z