Sulfur compounds in bottom sediments and interstitial waters of the Pacific Ocean to the east of Japan

In near-shore Pacific bottom sediments to the east of Japan unusually high content of free H2S ocurs. H2S resulting from bacterial reduction of sulfates from interstitial waters has a number of derivatives; pyrite dominates among them. Contents of other derivatives of H2S: sulfide sulfur and organic sulfur do not exceed 0,01%, content of organic sulfur does not exceed 0.1%. Due to reduction content of sulfates can reduce to 0,03% S. Capacity of the process of sulfate reduction, estimated by sum of all reduced forms of S - derivatives of H2S, is a function of organic matter content in sediments. Ability of bottom sediments to accumulate free H2S depends on content of reactive forms of Fe. Spatial distribution of reduced forms of S in the studied sediments is considered.

Chemical composition of sepiolites and palygorskites from bottom sediments of the Eastern Indian

In fault zones of the East Indian Ridge and adjacent areas of ocean floor almost monomineral sepiolite- and palygorskite clays have been found. They have been studied by a complex of optical and physical methods. Formation of authigenic sepiolites and palygorskite had occurred under influence of Mg- and Si-rich hydrothermal solutions by metasomatic replacement of montmorillonite clays, or by precipitation from saturated solutions in cracks of various rocks.

Composition of bottom sediments and serpentinites from Core PS-846

A core of foraminiferal-coccolithic oozes filling a valley of the transform fault located at 29°40'S on the South Atlantic Ridge contains layers composed of angular fragments of igneous and metamorphic rocks. They include many serpentinites deriving from serpentinized ultrabasic rocks, probably exposed on the lower section of the southern slope of the fault valley. A mineral and chemical description of these serpentinites is given.

Planktonic foraminifera stratigraphy and datums of ODP Site 184-1143 and Hole 184-1146A, South China Sea

The biostratigraphy of Miocene-age sediment samples recovered from Ocean Drilling Program Sites 1143 and 1146, South China Sea, is presented. The preservation of the planktonic foraminifers recovered from both sites varies widely, from poor to very good. The volume of biogenic sediment in the >63-µm size fraction also varies considerably, with many samples being dominated by mud. In comparison to shipboard biostratigraphy, based on core catcher analyses with a depth resolution of ~10 m, we analyzed samples from the two stratigraphic columns every 2-3 m (~45- to 93-k.y. resolution). The placement of planktonic foraminifer zonal boundaries was made at a resolution of ~1.5 m at Site 1146 and ~3.0 m at Site 1143. The higher resolution has resulted in significant changes in biostratigraphic zonal boundary locations compared to shipboard results. For the time interval of 5.54-10.49 Ma, the changes in zonation reveal similar age-depth models at both sites, with three segments of changing sedimentation rate through the upper Miocene, though the differences in sedimentation rates at Site 1146 are subtler than those at Site 1143. The boundary between lithologic Units II and III at Site 1146 corresponds to a sharp change in sedimentation rate (58 to 21 m/m.y.) at 15.1 Ma (the first occurrence of Orbulina suturalis). At this site, the interval from 16.4 to 15.1 Ma is characterized by very high mass accumulation rates in the noncarbonate fraction. Above this interval the carbonate fraction becomes increasingly important in the sediment flux to the South China Sea. At Site 1143, sedimentation rates increase from 8 to 99 m/m.y. at 8.6 Ma. This corresponds to a dramatic increase in both carbonate and noncarbonate mass accumulation rates at the site, but no change in lithology.