Contents and isotopic composition of black carbon from ODP Sites 184-1147 and 184-1148

A 30 m.y. stable isotopic record of marine-deposited black carbon from regional terrestrial biomass burning from the northern South China Sea reveals photosynthetic pathway evolution for terrestrial ecosystems in the late Cenozoic. This record indicates that C3 plants negatively adjusted their isotopic discrimination and C4 plants appeared gradually as a component of land vegetation in East Asia since the early Miocene, a long time before sudden C4 expansion occurred during the late Miocene to the Pliocene. The changes in terrestrial ecosystems with time can be reasonably related to the evolution of East Asian monsoons, which are thought to have been induced by several intricate mechanisms during the late Cenozoic and could contribute significantly to the post-Miocene marine carbonate isotope decline.

Chemical element contents and speciations in bottom sediments from the Transpacific profile

The paper deals with regularities of distribution of iron, manganese, copper, nickel, and vanadium in interstitial waters from different lithofacies types of bottom sediments on the profile from the coast of Mexico to the Wake Atoll in the Pacific Ocean. With increasing distance from the shore and with transition from reduced coastal sediments to oxidized deep-sea red clays concentration of iron and manganese in the interstitial waters greatly decreases. Elevated concentration of dissolved iron (0.34 mg/l) was observed only in highly reduced terrigenous sediments from the shelf and continental slope of Mexico. The highest concentrations of manganese (13.2 mg/l) were measured in hemipelagic carbonate-siliceous-clayey sediments. Compared to Pacific seawater interstitial waters are enriched in Fe, Mn, Cu, Ni, V. Interstitial waters contain only from 0.000004 to 1.2% of total contents of these elements in bottom sediments.

General descriptions, organic contents and geolipid ratios at DSDP Leg 72 Holes

Organic matter in sediments from Sites 515, 516, and 517 reflects a history of low marine productivity and of oxygenated bottom waters in the western South Atlantic since the Pliocene. Organic carbon contents are low, averaging 0.26% of sediment weight. Distributions of n-alkanes, n-alkanols, and n-alkanoic acids show evidence of microbial reworking, and n-alkanes contain important terrigenous contributions, presumably of eolian origin.

General descriptions, organic contents and ratios of geolipid components at DSDP Holes 75-530B and 75-532

Distributions of free and bound n-alkanes, n-alkanoic acids, and n-alkanols were determined in order to compare the character of organic matter contained in organic-carbon-rich sediments from two sites sampled by the hydraulic piston corer. Two diatomaceous debris-flow samples of Pleistocene age were obtained from Hole 530B in the Angola Basin. A sample of bioturbated Pleistocene diatomaceous clay and another of bioturbated late Miocene nannofossil clay were collected from Hole 532 on the Walvis Ridge. Geolipid distributions of all samples contain large terrigenous contributions and lesser amounts of marine components. Similarities in organic matter contents of Hole 530B and Hole 532 sediments suggest that a common depositional setting, probably on the Walvis Ridge, was the original source of these sediments through Quaternary, and possibly late Neogene, times and that downslope relocation of these biogenic deposits has frequently occurred.

(Table 3) Contents of P2O5 and total REE in phosphorites from Pacific seamonts

Changes in concentration levels and speciation of heavy metals during sedimentation on example of a typical semi-closed bay, where bottom sediments have formed due to river run-off, are under consideration. It is shown that due to desorption of mobile manganese, zinc and copper entered the bay with river suspended matter, their total contents in bottom sediments decrease and percentages of lithogenic forms increase. Contents and speciation of iron in bottom sediments are determined by its participation in coagulation of river colloids in the mixing zone and by mechanical differentiation of sedimentary material.

Contents of P2O5, Corg, Sr, and Ba in phosphorites and host sediments from the Atlantic and Pacific oceans

Sr contents in phosphorites on shelves of the Southwest Africa, and of Chile and Peru increase with degree of their lithification, from 0.05 to 0.28% and from 0.13 to 0.16% respectively. Phosphorites from Pacific submarine seamounts have the average Sr content 0.11%, and bone phosphate from Pacific floor 0.13%. Shelf phosphorites are characterized by high correlation coefficients between Sr and P2O5 (R = +0.82) and constant Sr/P2O5 ratio (0.0084). In phosphorites from submarine sea-mounts and in bones from the ocean floor Sr/P2O5 ratio is only a little higher than a half of that in shelf phosphorites. This indicates specific and different genesis of phosphorites from submarine mountains. Ba content in recent phosphorites from the shelf of the Southwest Africa changes with increasing degree of lithification. At first their Ba contents rise from 0.031 to 0.188%, then they diminish to 0.016%, and thereafter again increase to 0.070%. This is due to successive predominance of one of the following processes going in different directions: co-precipitation with phosphate gels or formation of true separate Ba phase, loss of phosphate in crystallization and "self-purification" of concentrations, and surface adsorption. In Peru-Chile shelf phosphorites the average Ba content is 0.017%, in phosphorites from Pacific seamounts 0.192%, and in fossilized bones 0.010%.

Contents of P2O5 and REE in phosphorites from shelves and Pacific seamounts

Recent phosphorites from the Namibian shelf are characterized by low REE contents, depletion in REE compared to host sediments and sharp deficiency of lanthanum and europium. In Late Quaternary and Pre-Quaternary phosphorites from ocean shelves REE contents and patterns in general are the same as in host sediments. Phosphorites from seamounts are enriched in REE compared to shelf phosphorites and their patterns are close to one of seawater. Behavior of REE in shelf phosphorites is determined by the fact that in early stages of phosphorite formation REE are associated not primarily with phosphate, but with organic matter and terrigenous impurities. Only in the later stages of diagenesis phosphate begins to play a leading role in concentration of REE. In metasomatic phosphorites on seamounts concentration of REE depends on age and depth of these rocks, i.e. it is determined by duration and conditions of contact with sea water.