Geochemical records of sediment cores from the Sea of Japan

Intervals of organic C- and carbonate-rich laminated sediments occur in the Sea of Japan with roughly the same frequency as temperature changes observed in Greenland ice cores, providing clear evidence of rapid oceanographic change during the past 36 kyr. Planktonic foraminiferal d18O data suggest that only the laminated sediments deposited during the Last Glacial Maximum (LGM), and perhaps one other interval formed during a period of increased water column stratification. Sedimentary Re and Mo data are consistent with bottom waters that were sulfidic during the LGM and suboxic during other laminated intervals. Results of a numerical model of Corg and Re burial are consistent with a mechanism whereby an increased Corg flux to the seafloor drove oxygen concentrations toward depletion during times of deposition of the suboxic laminated intervals. Such a process could have resulted from increased upwelling driven either by increased deep water formation due to colder and/or more saline surface waters or by stronger northeasterly monsoonal winds.

Description and chemical composition of manganese nodules collected during Hakuho Maru Cruise KH-72-2, Oct-Dec, 1972 in the Southwest Japan Arc and Ryukyu Arc areas

The cores and dredges described in this report were taken on the KH-72-2 Expedition in October-December, 1972 by the Ocean Research Institute, University of Tokyo from the R/V Hakuho Maru. A total of 21 cores and dredge sites have been recovered.

Analysis of radioactive manganiferous nodules from Tanokami, Japan

Characteristic black nodules have been retrieved in 1922 from the bed of the Kichijo River, that runs along the Tanakamiyama mountain in the Oni Province and ends into Lake Biwa in Japan. Their radiocativity has been studied along with that of crusts of similar nature found covering rock formations in the vicinity overlooking the stream. The high content in radium observed may be due to the high uranium content of the granite host rock typical of the Tanakamiyama formation.

(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.

Annotated record of the detailed examination of Mn deposits recovered by the Geological Survey of Japan (GSJ) during the 1971-1974 period in the Pacific Ocean

In 1974, the Geological Survey of Japan began its systematic investigation of manganese nodules in the Central Pacific Basin on the new geological research vessel Hakurei Maru. The first cruise (GH 74-5) was carried out over an eastern part area of the Basin (6°-10°30'N, 164°30'-171°30'W), and the authors report here the preliminary results on the occurrence of manganese nodule deposits, paying particular consideration to their relationship to submarine topography and surficial and sub-bottom sedimentary facies. The surveyed area comprises a deep-sea basin at 5,000-5,400 m, defined to the north and east by the chain of seamounts and guyots of the Christmas Ridge. The deep-sea basin is divided roughly into 2 contrasting topographic features. The eastern part is characterised by flattened topography resulting from continuous deposition of turbidities; the meridian and western parts are characterised by gently rolling topography and the existence of a large number of deep-sea hills. Manganese nodules are almost lacking in the former flattened eastern area, whereas they are widely distributed in the latter rolling meridian and western parts. The population density of nodules varies from less than 1 Kg/m² to 26 kg/m² and the higher density is found in the siliceous-calcareous ooze zone of rather small, flat basins surrounded by deep-sea hills. The density is closely related to the thickness of the transparent layer obtained by 3.5 kHz PDR profiling over the whole area. Considering the various data of grab sampling, 3.5 kHz PDR profiling and to a lesser extent of deep-sea television and camera observations, the most promising manganese field in the present area seems to be confined to the north of the western sector of the area.

(Page 290) Composition of a manganese deposit sample from the Todoroki Mine, Japan

The Todoroki Mine is situated about 25 kilometers to the south-east of Ginzan railway station in Siribesi Province, Hokkaido. The author analysed an interesting specimen of black manganese-ore which had a fractured surface which looked like that of a broken piece of wood. This new manganese mineral was studied in its form, physical properties and chemical composition. The author later named this mineral form as "todorokite".

Description of manganese deposits from the Todoroki mine, Hokkaido area, Japan

Manganese deposits are abundant in various places in the Oshima Peninsula southwest of Hokkaido. This is particular the case of Todoroki Mine situated about 25 kilometers to the south-east of the Ginzan railway station in Siribesi Province. It consists of manganese beds intermixed with a tertiary volcanic tuff complex overlaying granite.

Description of manganese nodules and crust collected from the Hakuho Maru Cruise KH-69-2, April-June, 1969, in the Japan Trench and Sea of Japan areas

The cores and dredges described in this report were taken on the KH-69-2 Expedition in April-June, 1969 by the Ocean Research Institute, University of Tokyo from the Hakuho Maru. A total of 12 cores and dredges sites have been recovered.