ALBERT

Description: Four species of gammaridean Amphipoda are recorded from the Iberian deep sea basin at about 5000 m depth: Bathyceradocus iberiensis sp. n., Paracallisoma platepistomum sp. n., Parandaniexis cf. mirabilis Schellenberg, 1929, and Paragissa galatheae Barnard, 1961. The biology of the four species is discussed.

Description: Constants of calcium, magnesium, zinc, cobalt, copper, and nickel exchange for sodium in iron-manganese nodules taken from different parts of the Pacific Ocean were determined under static conditions at constant ionic strength (?=0.05). These determinations revealed high capacity of nodules for sorbing the referred ions (their exchange constants range from 1.93 to 20.85). Obtained data demonstrate the major role of MnO and Fe2O3 in sorption processes in iron-manganese nodules.

Description: In 1970 a large deposit of ferromanganese nodules was discovered on the floor of the Indian Ocean southwest of Cape Leeuwin by the research vessel USNS Eltanin. This discovery, which was based largely on bottom photographs from about 20 stations, was discussed by Frakes (1975) and Kennett and Watkins (1975, 1976). The photographs suggest that the deposit spreads, nearly continuously, over 900 000km^2, and cores showed that the nodules are essentially confined to the sediment surface. Kennett and Watkins (op. cit.) pointed to the abundance of ripple and scour marks and current-formed lineations on the present surface, and of extensive disconformities in the cores, as evidence of strong present and past bottom currents in the region. They suggested that the current action had resulted in very low sedimentation rates, which had allowed the nodule field, named by them (1976) the 'Southeast Indian Ocean Manganese Pavement', to develop. In early 1976 the authors used the research vessel HMAS Diamantina for a 10-day cruise in the region to sample the nodules in order to study their chemistry and mineralogy. During the cruise 9 stations were occupied, 8 of them successfully (Figure 1), and about 2000 nodules were recovered from the sea bed. The apparatus used was a light box dredge on the ships hydrowire, which had a breaking strain of about one tonne. Although an attempt was made to reoccupy Eltanin photographic stations, it should be noted that positioning was by celestial navigation, so errors of up to 10 km are possible.

Description: The major and minor element compositions of a suite of abyssal sea-floor ferromanganese nodules and associated sediments from the eastern central Pacific have been used to examine inter-element relationships and the mineralogy of the nodules, the relationship between the composition of nodules, and their associated sediments and regional variations in composition with respect to likely modes for formation of such deposits. Apart from Mn and Fe, significant proportions of the total Ti, Ca, Mg, K, Ba, Sr, Th and Y and almost all the P, As, Ce, Co, Cu, Mo, Ni, Pb, Zn and Zr are present in the oxide fractions of the nodules. The Mg, Ba, Cu, Mo, Ni and Zn contents are significantly correlated with the total Fe content. Nodules from the northeastern tropical Pacific have Mn/Fe ratios highter than those in the oxide fractions of their associated sediments, todorokite as the principal Mn phase and relatively high concns of minor elements associated with Mn. Nodules from the south central Pacific have Mn/Fe ratios similar to those in the oxide fractions of the associated sediments, {delta}-MnO Sub(2) as the only Mn-phase, and relatively high concns of minor elements associated with Fe. There appears to be a smooth gradation in composition in the tropical Pacific between these 2 end members. The retional compositional variation is interpreted as a reflection of different sources of metals for, and different growth mechanisms of, sea-floor nodules. The oxide precipitate from sea water consists of {delta}-MnO Sub(2), has a relatively low Mn/Fe ratio and minor element contents related to the total Fe and Mn({delta}-MnO Sub(2)) content. The oxide precipitate forming in areas of very low sedimentation as a result of diagenetic remobilisation in the surface sediment consists of todorokite, and has a high Mn/Fe ratio and enhanced metal content in the Mn-(todorokite) phase. Available information on the morphology and compositional variation of individual nodules from the tropical Pacific corroborates these contrasting metal sources and suggests that they can be resolved on the scale of an individual oxide concretion.

Description: Considerable regional variations in the chemical composition of manganese nodules from a wide range of the Pacific Ocean have been observed. These variations can be more exactly expressed in terms of inter-element relationships. In particular, Cu-Mn and Cu-Ni associations reveal that Cu content in pelagic nodules increases rapidly in proportion to those of Mn or Ni. In nodules from continental borderland and hemipelagic areas, even if Mn or Ni contents increase, that of Cu increases only slightly. It is suggested that the considerable chemical differences within individual nodules and between nodules from the same site, at a limited pelagic area where there is no marked change in depositional conditions of nodules, are due to the role of hydrolyzable trace elements in the formation of nodules.

Description: Bulk composition of ferromanganese nodules from the pelagic environment of the Pacific Ocean is apparently related to nodule-growth rate, sediment-accumulation rate, and biologic productivity in the overlying seawater. Nodules with a high Mn/Fe ratio and high Ni and Cu concns tend to occur in areas where primary productivity in the surface layer of the ocean is high and the sediment accumulation rate low. They may have a Mn/Fe ratio as low as one and accrete at rates as low as 1 mm/10 M yrs. Nodules with a larger Mn/Fe ratio apparently have growth rates that are greater by as much as a factor of 10.

Description: This chapter discusses the formation and distribution of some metals in ocean-floor manganese nodules in the light of the observed data in the literature and thermodynamic and kinetic considerations of the oxidation of metal ions in the oceanic environment. There are, in general, two major schools of thought on the mechanism of incorporation of the minor elements such as nickel, copper, and cobalt with the major elements such as manganese and iron. One is the lattice substitution mechanism and the other the adsorption mechanism. If the mechanism is lattice substitution, extraction of the metal ions is not possible unless the lattice of the major elements is first broken and exchanged with other ions from the bulk solution. Consequently, the leaching behavior of minor elements should display a very close relationship with that of major elements.

Description: A complete processing method has been experimentally developed at laboratory scale for the future extraction of metlas from manganese nodules. The digestion of the nodules is performed by pressured sulfuric acid leaching at 200° C., nickel, copper, cobalt, and zinc being selectively dissolved in solution along with iron and manganese. The subsequent separation and recovery of the valuable metals is carried out with a combination of ion exchange and precipitation processes. Estimates for this methodology based on an annual throughput of 2 million tonnes of manganese nodules should lead to the production of about 24000 tonnes of nickel, 20000 tonnes of copper, and 3000 tonnes of cobalt and zinc. The authors conclude that, despite all uncertainty regarding the metal processing costs and the future metal prices, the exploitation of manganese nodules is economically viable.

Description: In the summer of 1974, upon returning to Woods Hole from the Azores, the submersible Alvin had the opportunity to make brief dives on Corner Rise and the New England seamount chain. This was the first time man had directly viewed the expanse of the Earth between the Mid-Atlantic Ridge and the North of the American continent. Single dives were made on seven seamounts: Corner Rise and Nashville, Gilliss, Rehoboth, Manning, Balanus, and Mytilus.

Description: This DSDP leg was originally conceived by the Antarctic Advisory Panel in order to investigate the geologic histories of the Scotia Arc and of the Argentine Basin. Site 326 (Drake Passage) was drilled in 3812 meters of water about 150 km southeast of Cape Horn. The main objective was to check the magnetic-reversal dating of the opening of Drake Passage by determining basement age. Site 327 is in 2400 meters of water on the western nose of the elevated eastern part of the Falkland Plateau, the Maurice Ewing Bank and was chosen to examine Southern Ocean shallow-water pre-Neogene biostratigraphy. Site 328, in 5103 meters of water in the Malvinas Outer Basin immediately to the east of the Falkland Plateau and to the south of the Falkland Fracture Zone, was chosen to examine correlatives of Argentine Basin acoustic reflectors, to obtain a deep-water southerly biostratigraphic section, and if possible, to date the underlying oceanic basement. Site 330, in 2626 meters of water at the western end of the elongate rise forming the eastern end of the Falkland Plateau, the Maurice Ewing Bank, was selected to elucidate the pre-Aptian history of the Falkland Plateau and to obtain a biostratigraphic section older than that cored at Sites 327 and 329.

Description: DSDP Leg 337 was planned as an attemp at deep penetration of the igneous section of the oceanic crust on the western flank of the FAMOUS (Franco- American Mid-Ocean Undersea Study) area of the Mid-Atlantic Ridge at 36°N. Site 332 is located in Deep Drill Valley approximately 30 km west of the axis of the Mid-Atlantic Ridge at 36°52'N latitude. The principal goal at this site was deep penetration into layer 2 of the ocean crust by multiple re-entry. Site 334 was drilled on a steep east-facing slope in a small, deep basin near the middle of magnetic anomaly 5. In this area, breccias with gabbro and peridotite clasts in a nannofossil-foram ooze matrix are interlayered with the plutonic rocks and may reflect exposure of a melange in or near the Median Valley of the Mid- Atlantic Ridge prior to burial by later basaltic extrusions.

Description: Unlike most previous Deep Sea Drilling Project cruises, Leg 39 was not scientifically planned as a "theme" cruise, on which a number of sites are drilled to address a single scientific problem area, namely, to improve our knowledge of paleocirculation changes and the overall geologic history of the South Atlantic Ocean. This would be done along more specific objectives: 1) collect a biostratigraphic section on the Ceará Rise (Site 354), determine the nature and age of a prominent reflector there, and determine the nature and age of basement; 2) date basement between magnetic anomalies 32 and 33 in the Argentine Basin (Site 358), and 33 and 34 in the Brazil Basin (Site 355); obtain as complete sedimentary sections as time would permit at the Ceará Rise, Brazil Basin, the Argentine Basin and Sào Paulo Plateau (Site 356).

Description: Fragments of a hydrothermal deposit, partly moulded on pieces of basalt lava, were dredged from the edge of the median valley in the centre of the Gulf of Aden. The deposit consists of two main components, manganese oxide in the form of spongy brown to hard black lumps and coatings, and friable green massive smectite. There are smaller amounts of an iron-oxide component, and mixed manganese-oxide-smectite material. Contents of the less mobile trace elements in the smectite are too low for it to have formed by alteration of basalt glass, and it is interpreted as a direct precipitate from hydrothermal solution. None of the components is enriched in Cu or Zn, or contains appreciable amounts of sulphur. If there are sulphides in this deposit, they must lie beneath the parts sampled.

Description: Submarine photography and box cores described in this report were taken during the R/V Oceanographer Cruise RP-8-OC-76 in October 1976 over area C of the DOMES project (Deep Ocean Mining Environmental Study). This cruise was part of Phase I of the DOMES project which was conducted by the U.S. Geological Survey under the auspices of the National Oceanic and Atmospheric Administration (NOAA). The purpose of DOMES project was to acquire the information necessary to provide both a timely and an independent assessment of the impact of deep ocean manganese nodule mining on the marine ecosystem before commercial mining operations begin. It was formulated in cooperation with the academic community and the mining industry. It consisted of a two-phase study, first to obtain basic information on the deep ocean environment and then to assess the impact of prototype mining operations on that environment.

Description: Quaternary sediments cored in the northeast Pacific nodule area (DOMES site C, 14°N, 126°W) contain a significant amount of hydrothermal metalliferous mud. Water content, color, mineralogy, and chemical composition are analogous to metalliferous sediments of the subequatorial East Pacific Rise. Correction for contribution of pelagic clay indicates the metalliferous fraction to be about 40% of the sediment. SiO2 and Mg are major components in the corrected composition, as they are for other metalliferous sediments similarly corrected from a variety of East Pacific Rise and DSDP metalliferous sediments. A correlation between Mg and SiO2 for these corrected sediments could indicate a hydrothermal origin for a significant portion of the SiO2. Results from DSDP in the nodule area suggest that metalliferous globules are a ubiquitous minor component of the Clipperton Oceanic Formation, which underlies much of the Pacific ferromanganese nodule belt. This indicates that deposition of hydrothermal precipitates is not confined to spreading centers.

Description: The usually high concentrations of Zn, Pb, Cd, and Cu in the most recently accreted portions of ferromanganese nodules from the western Baltic Sea are thought to reflect increased metal input due to anthropogenic mobilization. If so, the point of increase represents a time horizon within the structure of the nodule. Similar trace metal distributions of radiometrically dated sediments from the same area suggest that the ferromanganese nodules have grown in thickness between 0.02 and 0.16 mm yr-1. From this growth rate anthropogenic Zn flux to the nodule surface was calculated to be 80 mg m-2 yr-1.

Description: Information on possible resource value of sea floor manganese nodule deposits in the eastern north Pacific has been obtained by a study of records and collections of the 1972 Sea Scope Expedition.

Description: A preliminary report on the manganese nodule field southwest of Western Australia published in this Journal recently (Frakes, Exon and Granath, 1977) quoted chemical analyses which were carried out on air-dried material. Significantly higher metal values have been recorded in some later analyses done on nodules dried at 105°C. Tests have shown that the ground, air-dried material retains considerable moisture, which accounts for the higher metal values of the later analyses. The average water content (after drying at 105°C) has been determined at 16 percent. The relevant chemical data now available on this material are summarised in the accompanying table: in this table metal values (by atomic absorption spectrophotometry) have been recalculated assuming a moisture content of 16 percent.

Description: An initial investigation has been undertaken on the chemical composition of the manganese nodules. The results of chemical analyses on each layer of single nodules reveal the periodic patterns of distribution for Mn, Fe, Cu, Pb, Zn, Ni and Co contents. The variations strongly suggest that those of the elements in nodules from this region are, at least, climatically controlled.

Description: It is the purpose of this chapter to present information available at the time of publication on the internal features of manganese nodules, to offer genetic interpretations of these features, and to suggest new lines of research. To judge from the limited data available on ocean floor crusts rich in manganese and iron (see, for example, Aumento et al., 1968, doi:10.1594/PANGAEA.862565 ), much of what is learnt about nodules may be applied eventually to an understanding of the origin of these more continuous masses. A genetic relationship between these two is likely.

Description: Two types of deep-sea dredges are currently under development for the mining of the manganese nodules, a deep-sea hydraulic dredge and a mechanical cable-bucket system. Both systems offer some advantages with the hydraulic system appearing to be advantageous in themining of a specific deposit for which it is designed while the cable-bucket system appears to be somewhat more flexible in working in a variety of deposits, topographic environments, and water depths. Environmental studies conducted in conjunction with deep-sea tests of the two types of mining systems currently indicate that substantially no environmental damage will be done in the mining of the deep-sea nodules. Because of the nature of the deposits and the way in which they can be mined, the manganese nodules appear to be a relatively pollution free and energy-saving source of a number of industrially important metals.

Description: Manganese nodules from the Suiko Seamount exhibit the significant characteristics in mineral compositions. Well crystallized todorokite and birnessite, which are principal manganese mineral phase in nodules, only occur in the oxide layer directly incasing pebbles and coarse sand. The preferential formation of todorokite or birnessite phases seem to be principally controlled by the reaction rate of iron-manganese oxides with trace elements such as Cu, Ni, Co, Zn, Pb concentrated in nodules, rather than redox characteristics of sedimentary environment or mineralogical diagenetic process.

Description: Nodule samples obtained were described and studied on board for 1) observation of occurrence and morphology in and outside samplers, size classification, measurement of weight and calculation of population density (kg/m2); 2) photographing whole nodules on the plate marked with the frames of unit areas of both 0cean-70 (0.50 m2) and freefall grab (0.13 m2), and that of typical samples on the plate with a 5 cm grid scale: 3) observation of internal structures of the nodules on cut section; and 4) determination of mineral composition by X-ray diffractometer. The relation between nodule types and geological environment or chemical composition was examined by referring to other data of related studies, such as sedimentology. acoustic survey, and chemical analysis.

Description: Basalt samples obtained from the Siqueiros transform fault/fracture zone and the adjacent East Pacific Rise are mostly very fresh oceanic tholeiite and fractionated oceanic tholeiite with Fe+3/ Fe+2 ? 0.25; however, alkali basalts occur in the area as well. The rocks of the tholeiitic suite are ol + pl phyric and ol + pl + cpx phyric basalts, while the alkali basalts are ol and ol + pl phyric. Microprobe analyses of the tholeiitic suite phenocrysts indicate that they are Fo68-Fo86, An58-An75, and augite (Ca34Mg50Fe16). The range of olivine and plagioclase compositions represents the chemical variation of the phenocryst compositions with fractionation. The phenocyrsts in the alkali basalts are Fo81 and An69. The suite of tholeiites comprises a fractionation series characterized by relative enrichment of Fe, Ti, Mn, V, Na, K, and P and depletion of Ca, Al, Mg, Ni, and Cr. The fractionated tholeiites occur on the median ridge (which is a sliver of normal oceanic crust) of the double Siqueiros transform fault, on the western Siqueiros fracture zone, and on the adjoining East Pacific Rise, while the two transform fault troughs contain mostly unfractionated or only slightly fractionated tholeiite. We suggest that the fractionated tholeiites are produced by fractional crystallization of more 'primitive' tholeiitic liquid in a crustal magma chamber below the crest of the East Pacific Rise. This magma chamber may be disrupted by the transform fault troughs, thus explaining the paucity of fractionated tholeiites in the troughs. The alkali basalts are found only on the flanks of a topographic high near the intersection of the northern transform trough with the East Pacific Rise.

Description: The eleventh research cruise of Japanese Geodynamics Project in the West Pacific was carried out by the R/V Tokaidaigaku-maru II in August, 1974. During this cruise, in which the authors participated, many traverses of echo sounding and seismic reflection profiling and frequent sampling of bottom sediments were undertaken.

Description: Chemical composition of manganese nodules and crust collected from the Hakurei Maru Cruise GH74-5, September-October, 1974, in the Eastern Central Pacific Basin by the Geological Survey of Japan according to: Analyses and sample manganese deposits data from Cruise GH74-5 (private communication) (unpublished), Scripps Institution of Oceanography. http://www.ngdc.noaa.gov/mgg_mmbib/showref.jsp?mmbib=MIZUAA7702.

Description: Marked variations in the chemical and mineralogical composition of sediments at Site 319 have occurred during the 15 My history of sedimentation at this site. The change in composition through time parallels the variability observed in surface sediments from various parts of the Nazca Plate and can be related to variations in the proportion of hydrothermal, hydrogenous, detrital and biogenous phases reaching this site at different times. Metal accumulation rates at Site 319 reach a maximum near the basement for most elements, suggesting a strong hydrothermal contribution during the early history of this site. The hydrothermal contribution decreased rapidly as Site 319 moved away from the spreading center, although a subtle increase in this source is detectable about the time spreading began on the East Pacific Rise. The most recent sedimentation exhibits a strong detritalhydrogenous influence. Post-depositional diagenesis of amorphous phases has converted them to ironrich smectite and well-crystallized goethite without significantly altering the bulk composition of the sediment.

Description: Investigations of piston cores from the Vema Channel and lower flanks of the Rio Grande Rise suggest the presence of episodic flow of deep and bottom water during the Late Pleistocene. Cores from below the present-day foraminiferal lysocline (at ~4000 m) contain an incomplete depositional record consisting of Mn nodules and encrustations, hemipelagic clay, displaced high-latitude diatoms, and poorly preserved heterogeneous microfossil assemblages. Cores from the depth range between 2900 m and 4000 m contain an essentially complete Late Pleistocene record, and consist of well-defined carbonate dissolution cycles with periodicities of ~100,000 years. Low carbonate content and increased dissolution correspond to glacial episodes, as interpreted by oxygen isotopic analysis of bulk foraminiferal assemblages. The absence of diagnostic high-latitude indicators (Antarctic diatoms) within the dissolution cyclss, however, suggests that AABW may not have extended to significantly shallower elevations on the lower flanks of the Rio Grande Rise during the Late Pleistocene. Therefore episodic AABW flow may not necessarily be the mechanism responsible for producing these cyclic events. This interpretation is also supported by the presence of an apparently complete Brunhes depositional record in the same cores, suggesting current velocities insufficient for significant erosion. Fluctuations in the properties and flow characteristics of another water mass, such as NADW, may be involved. The geologic evidence in core-top samples near the present-day AABW/NADW transition zone is consistent with either of two possible interpretations of the upper limit of AABW on the east flank of the channel. The foraminiferal lysocline, at ~4000 m, is near the top of the benthic thermocline and nepheloid layer, and may therefore correspond to the upper limit of relatively corrosive AABW. On the other hand, the carbonate compensation depth (CDD) at ~4250 m, which corresponds to the maximum gradient in the benthic thermocline, is characterized by rapid deposition of relatively fine-grained sediment. Such a zone of convergence and preferential sediment accumulation would be expected near the level of no motion in the AABW/NADW transition zone as a consequence of Ekman-layer veering of the mean velocity vector in the bottom boundary layer. It is possible that both of these interpretations are in part correct. The "level of no motion'' may in fact correspond to the CCD, while at the same time relatively corrosive water of Antarctic origin may mix with overlying NADW and therefore elevate the foraminifera] lysocline to depths above the level of no motion. Closely spaced observations of the hydrography and flow characteristics within the benthic thermocline will be required in order to use sediment parameters as more precise indicators of paleo-circulation.

Description: Eighty-seven manganese nodules, representing 6 different locations at depths ranging from 2400 to 7400 m, from the eastern edge of the Blake Plateau were studied. Most of the nodules contained secondary structural textures resulting from the apparent burrowing of marine microfauna. This biogenic activity produced modification of the original growth patterns. In many cases the burrowed zones served as favored sites for redeposition of iron-manganese material. Transmitted light and scanning electron microscope analysis revealed the presence of 3 types of organic activity: (1) agglutinated foraminiferal tests; (2) pre-bored clay particles acting as nuclei or later included during nodule growth; and (3) younger burrows that cross-cut all older structures. In many instances this cross-cutting action resulted in almost total eradication of areas of the original growth patterns. The final texture may be mistaken for a similar growth texture previously classified as mottled, but a more specific genetic term might be 'disrupted'.

Description: Oxide coatings on sediments, especially iron, are ubiquitous in the oxygenated environments of most lakes. Deposits of ferromanganese oxides are especially abundant in many lakes in the glaciated regions of North America and Europe. Iron and manganese is readily derived from weathering of mechanically ground, largely crystalline rock debris which is permeable and readily weathered under the humid coldtemperate climate and abundant vegetation. Crusts around pebbles and cobbles constitute much of the most concentrated lacustrine ferromanganese deposits yet reported: Oneida Lake, New York, and Lake Tomahawk, Wisconsin. Freshwater phases tend to be less crystalline than their marine counterparts, possibly a result of faster accretion rates and thus having less time for recrystallization. Electron probe analyses of iron and manganese phases from two nodules from Lake Tomahawk are presented.

Description: The cores and dredges described in this report were taken on the GH76-2 Expedition in March-May, 1976 by the Geological Survey of Japan from the R/V Hakurei Maru. A total of 47 cores and dredges sites have been visited. The survey covered the whole of the Pacific side of the Tohoku Arc, the southern part of the Kurile Arc and the northern margin of the Izu-Ogasawara (Bonin) Arc. The surveyed area covered the continental shelves, slopes, trenches and Pacific basin along the trenches.

Description: This report of the GH76-1 cruise mainly includes the results of the on-board observations in the survey area of the medial-eastern part of Central Pacific Basin (5 degree -10 degree N, 170 degree -175 degree W) and partly of analytical work at the on-shore laboratory. In addition, the results of some on-board optical and geophysical works along the tracks of Japan-Ogasawara-survey area-Hawaii, are described in appendices. The GH76-1 cruise of the R/V Hakurei-maru was carried out from the 10th January to the 9th March, 1976 as the second phase field work of the Geological Survey of Japan five-year research program of study on the manganese nodule deposits of the Central Pacific Basin and also as a part of the National Research Institute for Pollution and Resources research program of technological study on the exploitation of deep sea mineral resources. The GSJ research program (F.Y. 1974-F.Y. 1978) aims at providing basic information on the manganese nodule distribution and their origin on the deep sea floor of the Central Pacific Basin bounded by the Marshall Ridge to the west, the Christmas Ridge to the east, and the Mid-Pacific Mountains to the north. The first phase of investigation was carried out during the GH74-5 cruise in the eastern part of the area (6 degree -10 degree 30'W, 164 degree 30'-171 degree 30'N)(Mizuno and Chujo, eds., 1975), and the present second phase covered an areas of 5 degree square, just west of the GH74-5 area.

Description: During the "Meteor“-Expedition to the Persian Gulf in March-May 1965, approximately 300 samples were collected. Most of them have been already studied by various authors in sedimentological as well as micropaleontological respects. 49 samples were selected for ostracode studies. These samples are arranged to form a long-axis section ("Laengsprofil“), and 4 shorter cross-profiles, perpendicular to the long-axis profile in the Persian Gulf and Gulf of Oman. 52 species of ostracodes in this area were specifically determined; 39 of them are described under open nomenclature. 13 species are already known from surrounding sea areas: 2 species from the Red Sea; 2 species from the east coast of Africa; 1 species from the Mediterranean Sea; and others from the Indian and Pacific Oceans. 12 species show close relationships to species from the Indopacific Ocean. The ostracode species found in the area can be grouped after the method of BRAUN-BLANQUT into 2 bioassociations. Association 1 with the following 4 characteristic species : Cytherella cf. pulchra, Loxoconcha sp. A, Neomonoceratina sp. A, Alocopocythere reticulata. Association 2 with 1 characteristic species: Ruggieria (Ruggieria) sp. B. The association 1 is widespread in the entire studied area of the Persian Gulf, where it is considered to characterize the shallow water region down to 200 m. The association 2 is restricted to the deeper water below 200 m of the inner part of the Oman Gulf. Only a few species known from the shallow water association of the Persian Gulf are present. Within the two ostracode associations mentioned above 4 zones from the total studied area could be related to the water depth. The zones A-D are characterized more or less readily by the relative abundance of certain species: Zone A : 7-30 m depth, on substrates of poorly coarse-grained clayey marl; Zone B: 30-94 m depth, on substrates of richly coarse-grained calcareous marl; Zone C: 94-1961208 m depth, on substrates of richly coarse-grained calcareous marl; Zone D: 196/208-500 m depth, on substrates of calcareous clay, poor in benthos. The regional and bathymetric distribution of the ostracode fauna in the area studied was compared in relation to 10 environmental factors: water depth, temperature, salinity, water density, O2-concentration, phosphate-silica contents, pH-values, stratification of the water body, water currents and type of sediments. The major environmental factors which appear to control the ostracode distribution are water depth (as a complex factor), O2-concentration and the type of sediment. At 3 stations (GIK01058, GIK01074 and GIK01204) species of the shallow water association were found together with a few bathyal species. These stations are situated at the outer Biaban shelf, in an area where the bottom water of the Persian Gulf flows down the slope towards the Oman Gulf. Several samples of the Zone B in the major part of the Persian Gulf show also a high species diversity containing a high percentage of subfossil ostracode carapaces. It is probable that the recent biocoenosis has been mixed with a late quarternary thanatocoenosis.

Description: The paleo-oceanography of the southeastern North Atlantic Ocean during the last 150,000 yr has been studied using biogenous and terrigenous components of hemipelagic sediments sampled close to the northwest African continental margin. Variations of oxygen isotope ratios in shells of benthic calcareous foraminifers in two cores allow the assignment of absolute ages to these cores (in the best case at 1000 yr increments). The uncorrected bulk sedimentation rates of the longest core range from 3.4 to 7.6 cm/ 1000 yr during Interglacial conditions, and from 6.5 to 9.9 cm/1000 yr during Glacial conditions; all other cores have given results of the same order of magnitude, but with generally increasing values towards the continental edge. The distribution of sediment components allow us to make inferences about paleo-oceanographic changes in this region. Frequencies of biogenic components from benthic organisms, oxygen isotope ratios measured in benthic calcareous foraminiferal shells, the total carbonate contents of the sediment and distributions of biogenic components from planktonic organisms often fluctuate in concert. However, all fluctuations which can be attributed to changes of the bottom water masses (North Atlantic Deep Water) seem to precede by several thousand years those which can be linked to changes of the surface water mass distributions or to changes of the climate over the neighboring land masses. Late Quaternary planktonic foraminiferal assemblages in the cores from the northwest African continental margin can be defined satisfactorily in the way that distributions of assemblages found in sediment surface samples from the northeast Atlantic Ocean have been explained. The distributions of assemblages in the northwest African cores can also be used to estimate past sea surface temperatures and salinities. The downcore record of these estimates reveals two warm periods during the last 150,000 yr, the lower one corresponding to the oxygen isotope stage 5 e (equivalent to the Eemian proper in Europe), the upper one to the younger half of the Holocene. Winter surface water temperatures during oxygen isotope stages 6, 4, 3, and 2 are remarkably constant in most cores, while summer sea surface temperatures during stage 3 reach values comparable to those of the warm periods during the Late Holocene and Eemian. Estimated winter sea surface temperatures range from 〉 16 °C to 〈 11°C, the summer sea surface temperatures from 〉 22 °C to 〈 15 °C during the last 150,000 yr. Estimates of the winter sea surface salinities fluctuate between 36.6‰ and 35.5‰, the higher values being restricted to the warm periods since the penultimate Glacial. Estimates for sea surface temperatures and salinities for two cores from the center of today's coastal upwelling region show less pronounced fluctuations than the record of the open ocean cores in the case of the station 12379 off Cape Barbas, more pronounced in the case of station 12328 off Cape Blanc. Seasonal differences between winter and summer sea surface temperatures derived from the estimated temperatures are today more pronounced in the boundary region of the ocean to the continent than further away from the continent. The differences are generally higher during warm climatic periods of the last 150,000 yr than during cooler ones. The abundance of terrigenous grains in the coarse fractions generally decreases with increasing distance from the continental edge, and also from south to north. The dominant portion of the terrigenous detritus is carried out into the ocean during the relatively cool climatic periods (stage 6, 4, later part of stage 3, stage 2 and oldest part of stage 1). The enhanced precision of dating combined with the stratigraphic resolution of these high deposition rate cores make it clear that the peaks of the terrigenous input off this part of the northwest African continental margin occur simultaneously with times of rapid sea level fluctuations resulting from large volume changes of the large Glacial ice sheets.