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Magnetic minerals in sediments of the continental shelf are sensitive to environmental changes. Therefore, to determine the exact phases of magnetic minerals is the prerequisite to investigate the paleoenvironmental significances. In this study, a comprehensive rock magnetic investigation, coupled with mineralogical studies, was carried out on the long core NHH01 (with a length of 125.64 m) from the central continental shelf of the South Yellow Sea. Single-domain greigite was identified as the dominant magnetic carrier in sediments between 44.90 and 51.80 m, and terrigenous magnetite is the major magnetic phase in the adjacent layers. The existence of greigite unambiguously indicates an anoxic environment. We tentatively interpreted that such an environment could be formed by the fast sea level changes, long-existing of the cold eddies during warm stages, or in a lake which might be related to locally tectonic uplifting. Therefore, the occurrence of the thick-layer greigite could supply a new perspective to paleoenvironmental or even tectonic studies. [ABSTRACT FROM AUTHOR]

Abstract Detrital minerals in sediments can provide insight into sedimentary provenance and depositional environments. Here we report a record of heavy minerals of a 300.1 m long core recovered from the western south Yellow Sea, which was dated back to the late Pliocene (~3.5 Ma). Results of detrital mineral analysis show that sediments are dominated mainly by silicate minerals sourced from the Chinese mainland through river inputs. Heavy minerals suggest that marine transgression occurred around 76–84 m depth of the core depth, about at 792–840 ka BP. The upper part of the core (0–76 m) is dominantly marine and the lower part (below 84 m) is terrestrial. From the Miocene to Early Pleistocene, the Yellow Sea area generally subsided; the deposition center began to move from west to east, therefore the content of fine sand increased relatively in the core sediment. Meanwhile, under the influence of depression evolution in the Subei Basin, the paths of rivers were shifted, as a result the contents of augite and garnet changed, sediments in the study area were dominated by proximal sediments sourced from the Subei Basin, possibly of mixed sediments of the Yellow River and Yangtze River. The lower part of the core was characterized by a dramatic increase in augite with hornblende and epidote as dominant minerals. In the Early Pleistocene, under the background of subsidence in the Yellow Sea area, while transgression occurred, rivers shifted southward. Comparison with the mineral composition of adjacent core NHH01 and surface sediments from the region suggests the Yellow River dominated the study area, and the old Yangtze River input being occasionally dominant. The heavy mineral assemblage was dominated by hornblende and epidote, as well as mica, garnet and authigenic pyrite in some sediment layers. [ABSTRACT FROM AUTHOR]

The Yellow Sea Warm Current (YSWC) and the Yellow Sea Cold Water Mass (YSCWM) are the most significant hydrological characteristics of the Yellow Sea as they strongly influence the matter transportation, sedimentation, and the benthic and pelagic environments of the region. Previous studies focused mostly on formation and evolution of the YSWC and the YSCWM on shorter time scales (e.g., since the Holocene) and studies on longer time scales are rather sparse. This study conducted a high-resolution magnetostratigraphic investigation on core DLC70-3 (with a water depth of 71.2 m) in the northern part of the south Yellow Sea. Results show that the Brunhes/Matuyama polarity reversal boundary is located at a depth of 59.08 m. Constrained by both magnetostratigraphy and 14 C dating, three sedimentation episodes revealed by the benthic foraminifera content correspond to high sea level periods of marine isotope stage (MIS) 5–MIS9, MIS11–MIS17, and MIS19–MIS21, respectively. Cold-water benthic foraminifera species, total organic carbon, total sulfur, molybdenum element, and long-chain unsaturated alkenones index of the studied sediments show that both the YSWC and the YSCWM have evolved since the middle Pleistocene mainly due to combined effects of fluctuations of sea level and local tectonic subsidence. More specifically, both the YSWC and the YSCWM were intensified during high sea level periods of MIS5e–MIS9, MIS19 and MIS21. In addition, occurrence of the YSWC and the YSCWM are not always coeval as in the MIS5a–5d period, which is characterized by relatively stronger YSCWM but absence of the YSWC. These studies significantly improve our understanding of the evolution mechanism of both the YSWC and the YSCWM in this region. [ABSTRACT FROM AUTHOR]