Changes in detrital sediment supply to the central Yellow Sea since the last deglaciation

Abstract

Abstract. The sediment supply to the central Yellow Sea since the last deglaciation was uncovered through clay mineralogy and geochemical analysis of core 11YS-PCL14 in the Central Yellow Sea Mud (CYSM). The core can be divided into four units based on the various proxies, such as grain size, clay mineralogy, geochemistry, and Sr and Nd isotopes: Unit 4 (700–520 cm; 15.5–14.8 ka), Unit 3 (520–310 cm; 14.8–12.8 ka), Unit 2 (310–130 cm; 12.8–8.8 ka), and Unit 1 (130–0 cm; <8.8 ka). Unit 2 is subdivided into two subunits, Unit 2-2 (310–210 cm; 12.8–10.5 ka) and Unit 2-1 (210–130 cm; 10.5–8.8 ka), according to smectite content. Comparison of the clay mineral compositions, rare earth elements, and εNd indicate distinct provenance shifts in core 11YS-PCL14. Moreover, the integration of clay mineralogical and geochemical indices show different origins according to particle size. During the late last deglaciation (Units 3 and 4, 15.5–12.8 ka), Unit 4 sediments originated from all potential provenance rivers, such as the Huanghe, Changjiang, and western Korean rivers, while the source of coarse sediments changed to the Huanghe beginning with Unit 3. Fine-grained sediment was still supplied from all rivers during the deposition of Unit 3. Early Holocene (Unit 2) sediments were characterized by oscillating grain size, clay minerals, and moderate εNd values. In this period, the dominant fine-sediment provenance changed from the Huanghe to the Changjiang, whereas coarse sediments most likely originated from western Korean rivers. The Unit 1 CYSM sediments were sourced primarily from the Changjiang, along with minor contributions from the western Korean rivers. Possible transport mechanisms concerning such changes in the sediment provenance include paleo-river pathways, tidal stress evolution, and the development of the Yellow Sea Warm Current and coastal circulation systems, depending on the sea level fluctuations.

X-ray Diffraction Analysis of Clay Particles in Ancient Baekje Black Pottery: Indicator of the Firing Parameters

“…All of the above studies on the mineral composition of ancient Baekje black pottery analyzed the bulk powder collected from pottery fragments and did not examine clay-sized particles containing minerals of small traces or weak crystallinity, such as clay minerals and iron oxides. Many geological studies have used concentrated specimens, by separating and collecting clay particles, to identify the exact composition of clay minerals in the specimens, which is difficult to identify in bulk powder [37][38][39][40]. In the case of pottery, the composition of iron oxides and clay minerals that were not detected in the bulk powder must be investigated through mineralogical research on clay particles, as clay-rich soil is the main raw material used.…”