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Study of sediment sources and transport pathways in the Chukchi and East Siberian Seas is vital for understanding the interaction of fluvial, ocean, and sea-ice dynamics. In this study, 42 samples were analyzed for heavy minerals and 23 were analyzed for garnet geochemistry. These analyses suggest that the surface sediment is mainly sourced from the surrounding rivers. There are distinctive performances between the heavy minerals and garnet geochemistry of sediments in the Chukchi Sea and the East Siberian Sea. The content of hypersthene increased significantly on the outer shelf of the Chukchi Sea. The garnet was derived from volcanic rocks of the Okhotsk-Chukotka volcanic province and transported from the Gulf of Anadyr by the Pacific inflow. Coastal erosion materials dominated in the inner shelf of the Chukchi Sea. A significant amount of river input occurred in the western, middle, and eastern parts of the East Siberian Sea. The inputs from the Indigirka River and Kolyma River tend to be distributed eastward. The garnet geochemistry shows that there was a mixed sedimentary zone located south of Wrangel Island. The sediments in the outer shelf of the East Siberian Sea show a stable mixed sedimentary environment. [ABSTRACT FROM AUTHOR]

Data on grain size and heavy mineral composition for surface sediments on the Prydz Bay continental shelf was analysed to identify sediment features and provenance. The grain size composition of surface sediments indicate spatial variations in the glaciomarine environment and the key factors influencing sedimentation, which on the shelf include topography/water depth, currents and icebergs. The study area was divided into two sections by Q-type factor analysis: section I included Prydz Channel, Amery Basin and Svenner Channel, and section II included Four Ladies Bank, Fram Bank and the area in front of the Amery Ice Shelf. Sedimentation in section I is mainly controlled by currents and topography/water depth. However, in section II, icebergs/floating ice masses, the Amery Ice Shelf and currents have prominent effects on sedimentation. The heavy mineral composition indicates that surface sediments on the eastern side of the bay, including Four Ladies Bank, are primarily derived from Princess Elizabeth Land. Sediments in the area in front of the Amery Ice Shelf, Svenner Channel, Amery Basin and Prydz Channel have a mixed source from the eastern regions around the bay, including the Prince Charles Mountains and Princess Elizabeth Land. The contribution from Mac. Robertson Land to sediment at Fram Bank is limited. [ABSTRACT FROM PUBLISHER]

A total of six δC minimum events, i.e., VI, V, IV, III, II, and I, were observed via a stable carbon and oxygen isotope analysis of infaunal benthic foraminifera Uvigerina spp. in gravity core OS03-1 in the southeastern Okhotsk Sea over the last 180 ka. These events occurred at 112-109, 102-90, 85-76, 57-54, 44-40, and 17-10 ka BP. The largest negative excursions reached 2.5 ‰ in event V and were greater than 1 ‰ in the other events. We proposed that all δC minimum events were caused by the increase in sea surface water productivity, the weakened formation of Okhotsk Sea intermediate water, and the enhancement of the oxygen minimum zone. The negative excursions were unaffected by methane hydrate destabilization and subsequent methane release based on the results obtained by using archaeal lipid markers. [ABSTRACT FROM AUTHOR]

Based on results of nannofossil analysis and 10Be dating in ferromanganese crusts M1-1 and A1-1 (no nannofossils were found in it), from the western and central Pacific respectively, it is found that the crust growth ages from nannofossil biostratigraphy agree well with those based on 10Be isotope analysis. Both crusts have three growth layers, and the oldest layer was deposited in Miocene at about 12.80 Ma. The maximum, minimum, and average growth rates of crust A1-1 (from the central Pacific) are 8.11, 1.92 and 3.47 mm/Ma, and those of crust M1-1 (from the western Pacific) are 2.93, 0.47, and 0.94 mm/Ma. [ABSTRACT FROM AUTHOR]

Sediment core OS03-1 retrieved from the Akademia Nauk Rise in Southern Okhotsk Sea was analyzed for the contents of rare earth elements (REEs) and combined with carbon isotope (δ 13 C) time series of benthic foraminifera to infer changes in terrigenous accumulation and bottom water ventilation on glacial–interglacial timescales in the study area. The age model of OS03-1 was constructed by a combination of foraminifer δ 18 O stratigraphy and 14 C AMS dating, revealing that the 380 cm long core provides a window on climate change in the southern Okhotsk Sea since ∼180 ka. A grain size-controlled-REE content shows strong glacial–interglacial changes. The Cerium and Europium anomalies vary from 0.89 to 1.32 and from 1.14 to 1.37, respectively. The (La/Yb) N values range between 0.55 to 0.92. Both results suggest a significant contribution of volcanic debris in the core sediments. In addition, the relationships between Sm vs. Nd suggest main contribution origin from the Amur River and sea ice during warm intervals and from the sea ice during cold intervals, indicating that the sea ice played an important role in transporting terrigenous materials to the study site in the southern Okhotsk Sea. During the last 180 ka, the mass accumulation rates (MAR) of ∑REEs are relatively higher during glacials and lower during interglacials with a peak accumulation during the early deglacial period. We infer that an intensified Mongolia High is responsible for the first-order accumulation pattern of ∑REEs in the southern Okhotsk Sea by mediating the dynamic changes in sea ice extent. Furthermore, six δ 13 C minima are associated with intensified Asian monsoon (AM) precipitation and maximum MARs of ∑REEs, indicating that the dominance of barrier layer effects by high fresh water input through sea ice melting. The maximum MAR of ∑REEs during the Marine Isotope Stage (MIS) 5c coincides with the minimum of benthic foraminiferal δ 13 C, indicating a major interruption of ventilation in the bottom water in the Okhotsk Sea. The major low ventilation event in the deep water of the Okhotsk Sea appears to be dampened by a cooling condition and a major blooming of surface productivity preceded the event. [ABSTRACT FROM AUTHOR]

Abstract: Two gravity cores collected off the modern Huanghe (Yellow River) delta in the southern Bohai Sea were analyzed for grain size, the total organic carbon (TOC)/total nitrogen (TN) ratio, color diffraction, magnetic susceptibility, 14C dating and 137Cs and 210Pb isotope contents to clarify changes in the sedimentary environment during the Holocene. In particular, the effect of natural and artificial river-course shifts of the Huanghe on the Bohai Sea sediment was investigated. A peat layer, scouring surface and sharp changes in the grain size, TOC/TN ratio, sediment color (L ⁎, a ⁎) and magnetic susceptibility were identified and are likely to be due to the early-Holocene sea-level rise resulting in environmental changes from coastal to shelf environments in the Bohai Sea. After the sea level reached its maximum at 6–7kaBP, the lateral shifts in the river course of the Huanghe formed 10 superlobes, and superlobe 7 (11–1048 AD) and superlobe 10 (1855–present) of the Huanghe delta affected the core sites. The northern site of BH-239 has been more affected by the Huanghe since the middle Holocene. Notably, in the superlobe 10 period, the reshaping of the northern Huanghe delta due to an artificial river-course shift from northward to eastward in 1976 (e.g., a∼10km shoreline retreat due to coastal erosion) was recorded in the core sediments, particularly in terms of the TOC/TN ratio, sediment color (L ⁎ and a ⁎) and magnetic susceptibility, owing to the huge sediment supply from coastal erosion of the former river mouth area. [Copyright &y& Elsevier]