(Table 1) Sediment chemistry and Sulphur isotope ratios of ODP Site 127-795

Sixty sediment samples collected every 10 m from Holes 795A and 795B in the northern Japan Sea were analyzed for 27 major and trace elements using instrumental neutron activation analysis, and for total organic carbon (TOC), total nitrogen, and total sulfur (TS). Sulfur isotope ratio (d34S CDT) was measured on sedimentary framboidal pyrite isolated from sediments with a high sulfur content. The changes in redox condition of the bottom water of the sea are estimated from vertical variations of redox sensitive elements (TOC, TS, Mn, Sb, U, and As) and from TOC-TS and TS-d34S CDT relationships. These data were compared to those from a piston core (KH77-3-L4') collected near Site 795. The estimated changes in the redox condition are: a variation between less oxic and less euxinic in Units 5,4B, 4A, and 3 (ca. 13-15 to 6-7 Ma); oxic but less so than that of the present Japan Sea with diagenetic sulfate reduction under very high biological productivity in Unit 2 (ca. 6-7 to 2.4 Ma); and a drastic variation between oxic, similar to the present bottom water, and euxinic, similar to that during the last glacial period in the sea, in Units IB (ca. 2.4-1.2 Ma) and 1A (ca. 1.2 Ma to the present)

Geochemistry on sediments in Lake Biwa

Thirty sediment cores (30-40 cm in length), 47 Ekman dredge sediments, and Mn concretions were collected from Lake Biwa. The concentrations of 36 elements in the samples were determined by instrumental neutron activation, X-ray fluorescence, atomic absorption, and colorimetric analyses. The elements determined included Mn, P, As, Sb, Fe, Ni, Co, Zn, Cu, Pb, Hg, Cr, Ti, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Hf, La, Ce, Sm, Eu, Yb, Lu, U, Th, Au, Ta, Nd, Br and N. Based on statistical considerations and calculation of the concentration factors of the elements, the features of the elemental distribution in Lake Biwa sediment were determined. The main results are summarized as follows : (1) Concentrations of Mn and As were very high in the uppermost oxidized layer of the offshore sediment and Mn concretions. This resulted from the dissolution-deposition cycles of these elements within the sedimentary column and the bottom water. The fixation of As at the sediment surface is mainly attributed to the adsorption of arsenate onto Mn (II) -rich hydrous Mn (IV) oxide. (2) There were high concentrations of Zn, Cu, Pb and Hg in the recent sediments. Although the source of these elements is attributed to human activities, the individual distributions of Zn and Cu in the sediment may result from the deposition of metal-rich planktonic debris and subsequent degradation of the debris. (3) The orders of increasing concentrations of alkali metals and lanthanides in the sediment from the central region compared with the nearshore pediment were identical to the orders of increasing atomic numbers from Na to Cs and from La to Lu, respectively

(Table 1, pages 283), Elemental concentrations of ferromanganese crusts from Lake Biwa, Japan

Ferromanganese crusts were sampled from the surface of a stone collected at a depth of 20 m in the northern part of Lake Biwa, Japan. These samples were analysed for 37 elements by neutron activation, X-ray fluorescence, and ICP-AE. The crusts were found to be enriched with Ba, P, B, As, and sometimes with Co, Ni, Cu and Sb. The elements were classified into 4 groups based on the varieties of host minerals (Fe-oxides, Mn-oxides or allochthonous materials) in which they were incorporated : elements mainly associated with 1) Mn-oxides : Ba, Ni, Cs, Sr and Co ; 2) Fe-oxides : P, B and As; 3) allochthonous materials : Na, K, Rb, Al, Ti, Sc, Hf and Th ; and 4) Mn-oxides plus allochthonous materials : rare earth elements and major heavy metals. The elemental compositions in the Lake Biwa concretions, including the crusts and Mn-deposits studied previously by these authors, were compared with those in other freshwater and oceanic concretions. As a result, the concentrations of rare earth elements and major heavy metals were found to be much lower, whereas those of B, P and As were higher in the Lake Biwa than in the oceanic concretions. These differences could be well explained in terms of the effects of sea salt, growth rates of the concretions, and pH of the formation environment