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: From 12 radiolarian-rich claystone samples of the DSDP-Leg 25, Site 249, situated in the western Indian Ocean southwest of Madagascar 4 species of agglutinated and 38 species of calcareous benthonic foraminifera are described, 13 of them in open nomenclature. As a lot of Valanginian species and Gavelinella barremiana occur in the foraminiferal faunas described here a Valanginian-Hauterivian age is assigned to them. These microfaunas investigated here yield some index species characteristic in the Lower Cretaceous deposits of Northern Germany and also from the near-by Madagascar. Nodosariids dominate in a striking way with 36 species, especially of Astacolus, Citharina, Lenticulina, Lingulina, Marginulinopsis, Nodosaria, Saracenaria, and Vaginulina. Important Neocomian species well-known from other DSDP sites, namely Praedorothia ouachensis (SIGAL) and planktonic foraminifers, are missing. The microfaunas of Site 249 have to be derived from shelf areas.

Description: Most of the helium-3 in oceanic sediments conies from interplanetary dust particles (IDPs), and can therefore be used to infer the accretion rate of dust to the Earth through time (Ozima et al., 1984, doi:10.1038/311448a0; Takayanagi and Ozima, 1987, doi:10.1029/JB092iB12p12531; Farley, 1995, doi:10.1038/376153a0). 3He records from slowly accumulating pelagic clays indicate that the accretion rate varies considerably over millions of years, probably owing to cometary and asteroidal break-up events3. Muller and MacDonald have proposed (Muller and MacDonald, 1995, doi:10.1038/377107b0) that periodic changes in this accretion rate due to a previously unrecognized 100-kyr periodicity in the Earth's orbital inclination might account for the prominence of this frequency in climate records of the past million years (Imbrie et al., 1993, doi:10.1029/93PA02751). Here we report variations in the 3He flux to the sea floor that support this idea. We find that the flux recorded in rapidly accumulating Quaternary sediments from the Mid-Atlantic Ridge oscillates with a period of about 100 kyr. We cannot yet say, however, whether the 100-kyr climate cycle is a consequence of, a cause of, or an effect independent of these periodic changes in the rate of delivery of interplanetary dust to the sea floor.

Description: The genus Hinia is divided in 4 subgenera; other subgenera are not represented in the area studied. It was possible to find criteria for a better discrimination of the highly variable species H. (Hinia) schlotheimi and H. (Hinia) turbinella. The species "fuchsi" has been placed in the synonymy of H. (Hinia) turbinella. The species H. (Hinia) schlotheimi (BEYRICH) and H. (Telasco) schroederi (KAUTSKY) have been united under the name H. (Hinia) schlotheimi. The easily distinguishable species H. (Tritonella) tenuistriata and H. (Hinia) sulcata belong to two different genera. H. (Tritonella) cimbrica andersoni of the Viol- and Katzheide-Beds (Reinbek-stage) is separable from the population found in the Hemmoor-stage, it turned out to be a valuable guide subspecies for the Reinbek-stage. The species H. (Tritonella) serraticosta, H. (Tritonella) catulli, H. (Hinia) holsatica, and H. (Telasco) syltensis are all similar in respect to shape and ornamentation. Criteria have been found for a better discrimination of these species. The species contabulata, effusa and seminodifera described by SPEYER (1864), turned out to be contogenetic stages of H. (Tritonella) pygmaea. H. (Tritonella) cavata, previously described from the Tertiary of the North sea area, was proven to be absent from the area investigated. The forms described under that name, belong to H. (Tritonella) woodwardi.

Description: This chapter was previously intended to trace volcanic episodes through the Neogene and Pleistocene geological history recorded in the sedimentary sections drilled on the Emperor seamounts. Drilling disturbance, poor core recovery, and incomplete stratigraphic sections recovered from the seamounts have frustrated that plan, however. Moreover, the Leg 55 sedimentologists found in their smear-slide studies that transported island-arc tephra is scarce in the sediments, if present at all. So we have restricted our objective to description of the volcaniclastic admixture in sediments, as determined by mineralogical and geochemical data. We studied geochemistry of bulk samples (see Murdmaa et al., 1980), coarse-fraction mineralogy, and additional smear slides. The results obtained, however, do not tell much more about the volcaniclastic matter than did shipboard core descriptions.

Description: Investigations at a Late Weichselian freshwater basin in northwestern Jutland, Denmark, yielded a fairly rich assemblage of vertebrate remains, mostly bones and teeth of small mammals. The remains are primarily allochthonous and the bones have been subjected to different taphonomic pathways and agents. AMS 14C-dates on terrestrial organic remains provided ages of Middle to Late Allerød time. Identifications revealed the first fossil record in Scandinavia of Rana arvalis, Sorex minutus, Ochotona cf. pusilla, Microtus gregalis, Microtus oeconomus, and Sicista cf. betulinu. Spermophilus cf. major and Desmana moschata, previously found only once and twice respectively, were retrieved, and Sorex araneus and Arvicola terrestris were recovered for the first time beyond the Atlantic chronozone. Ecologically, the Nørre Lyngby small mammal fauna can be characterized by its very high and almost equal proportions of boreal forest and steppe elements followed by a relatively high proportion of tundra elements. The fossil species share a modern area of sympatry north of the Caspian Sea from the river Volga in the west to the southern and western slopes of the Urals. If, however, the large Allerød mammals are added, the fauna is without modern analogues. The Nørre Lyngby fauna can be seen as a last expansion of the North European glacial fauna. Provided that an absolute chronology and a differentiated sea-level curve for the area can be established, the Nørre Lyngby fauna could become important for studies in mammalian dispersal and migration rates.

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: The determinations of the radioactivity of a series of ferro-manganese concretions of the seas and lakes of the U.S.S.R. (especially of the Kara Sea and lakes of Karelia) have brought out certain facts which make possible the determination of the age of the concretions by the content of radium in its different layers.

Description: Manganese nodules made of radiating rods of well crystallized birnessite were sampled at 8 degree 481.2'N, 103 degree 53.8W, 1875 m below sea level by a dredge that also collected hyaloclastite and basaltic talus. The nodule field is on the floor of a caldera within a young tholeiitic seamount and was discovered and photographed during a deep-two survey. It is interpreted as a brecciated hydrothermal deposit, crystallized from an amorphous manganese oxide precipitate that formed when seawater-based hydrothermal fluids mixed with oxidized seawater. The nodules and surrounding igneous rocks have subsequently been encrusted with hydrogenous ferromanganese oxides.

Description: The successful drilling on Legs 51, 52, and 53 created a rare opportunity to investigate the long-term effects of seawater-rock interactions on the mineralogy and chemistry of basalts erupted on the sea floor. The purpose of this paper is to describe the weathering of the basalts in terms of the changes in their mineralogy and chemistry, and to compare the weathering observed in Hole 418A with that in the upper parts of Hole 417A.

Description: Two distinct sedimentary facies produced by sea-floor hydrothermal activity were cored during Deep Sea Drilling Project Leg 54. The first is equivalent to the typical basal iron- and manganese-rich, clayey mud recovered at many DSDP sites. It was sampled as a dispersed component throughout the cores taken in small sediment ponds in several sites within 120 km of the East Pacific Rise at 9°N. We infer that this component was originally deposited as iron hydroxides dispersed from high-temperature vents over the axial magma chamber of the East Pacific Rise. In the sediments, the iron hydroxides have reacted diagenetically with siliceous microfossil tests and detrital clays to form K- and Fe-rich clays with variable SiO2/Fe2O3 and Fe2O3/Al2O3, ratios.

Description: Deep sea manganese nodules from the Central Pacific Basin are mainly composed of 10Å manganite and d-MnO2 Two zones equivalent to the minerals are evidently distinguishable according to their optical properties. Microscopic and microprobe analyses revealed quite different chemical compositions and textnral characteristics of the two zones. These different feature of the two zones of nodules suggest the different conditions under which they were formed. Concentrations of 11 metal elements in the zones and inter-element relationships show that the 10Å manganite zone is a monomineralic oxide phase containing a large amount of manganese and minor amounts of useful metals, and that the d-MnO2 zone which is apparently homogeneous under the microscope is a mixture of three or more different minerals. The chemical characteristics of the two zones can explain the variation of bulk composition of deep sea manganese nodules and inter-element relationships previously reported, suggesting that the bulk compositions are attributable to the mixing of the 10Å manganite and d-MnO2 zones in various ratios. Characteristic morphology and surface structure of some types of nodules and their relationships to chemistry are also attribut able to the textural and chemical features of the above mentioned two phases. Synthesis of hydrated manganese oxides was carried out in terms of the formation of manganese minerals in the ocean. The primary product which is an equivalent to d-MnO2 was precipitated from Mn 2+ -bearing alkaline solution under oxigenated condition by air bubbling at one atmospheric pressure and room temperature. The primary product was converted to a l0Å manganite equivalent by contact with Ni 2+, Cu 2++ or CO2+ chloride solutions. This reaction caused the decrease of Ni2+, Cu2+ or CO2+ concentrations and the increase of Na+ concentration in the solution. The reaction also proceeded even in diluted solutions of nickel chloride and resulted in a complete removal of Ni2+ from the solution. Reaction products were exclusively 10Å manganite equivalents and their chemical compositions were very similar to those of 10Å manganite in manganese nodules. The maximum value of(Cu+Ni+Co)/Mn ratio of 10Å manganite zones in manganese nodules is 0.16, and the Ni/Mn ratio of synthetic 10Å manganite ranges from 0.15 to 0.18 with the average of 0.167.

Description: The cores and dredges described at this site were taken on the ANTIPROD II cruise from 21 February to 9 April 1980 by the Muséum National d'Histoire Naturelle from the R/V Marion Dufresne. A total of 10 cores were recovered and are available at MNHN for sampling and study.

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: Twenty-four manganese nodules from the surface of the sea floor and fifteen buried nodules were studied. With three exceptions, the nodules were collected from the area covered by Valdivia Cruise VA 04 some 1200 nautical miles southeast of Hawaii. Age determinations were made using the ionium method. In order to get a true reproduction of the activity distribution in the nodules, they were cut in half and placed for one month on nuclear emulsion plates to determine the alpha-activity of the ionium and its daughter products. Special methods of counting the alpha-tracks resolution to depth intervals of 0.125 mm. For the first time it was possible to resolve zones of rapid growth (impulse growth) with growth rates, s 〉 50 mm/106 yr and interruptions in growth. With few exceptions the average rate of growth of all nodules was surprisingly uniform at 4-9 mm/10 yr. No growth could be recognized radioactively in the buried nodules. One exceptional nodule has had recent impulse growth and, in the material formed, the ionium is not yet in equilibrium with its daughter products. Individual layers in one nodule from the Indian Ocean could be dated and an average time interval of t = 2600±400 yr was necessary to form one layer. The alternation between iron and manganese-rich parts of the nodules was made visible by colour differences resulting from special treatment of cut surfaces with HCl vapour. The zones of slow growth of one nodule are relatively enriched in iron. Earlier attempts to find paleomagnetic reversals in manganese nodules have been continued. Despite considerable improvement in areal resolution, reversals were not detected in the nodules studied. Comparisons of the surface structure, microstructure in section and the radiometric dating show that there are erosion surfaces and growth surfaces on the outer surfaces of the manganese nodules. The formation of cracks in the nodules was studied in particular. The model of age-dependent nodule shrinkage and cracking surprisingly indicates that the nodules break after exceeding a certain age and/or size. Consequently, the breaking apart of manganese nodules is a continuous process not of catastrophic or discontinuous origin. The microstructure of the nodules exhibits differences in the mechanism of accretion and accretion rate of material, shortly referred to as accretion form. Thus non-directional growth inside the nodules as well as a directional growth may be observed. Those nodules with large accretion forms have grown faster than smaller ones. Consequently, parallel layers indicate slow growth. The upper surfaces of the nodules, protruding into the bottom water appear to be more prone to growth disturbances than the lower surfaces, immersed in the sediment. Features of some nodules show, that as they develop, they neither turned nor rolled. Yet unknown is the mechanism that keeps the nodules at the surface during continuous sedimentation. All in all, the nodules remain the objects of their own distinctive problems. The hope of using them as a kind of history book still seems to be very remote.

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: The text studies the deep-sea red clays in the East-Central Pacific ocean (Tahiti-Touamotou Archipelago), their authigenic formation, transport and diagenetic character in particular through their composition in REE.

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: New data for the direct measurement of the isotopic composition of neodymium in Atlantic Ocean seawater are compared with previous measurements of Pacific Ocean seawater and ferromanganese sediments from major ocean basins. Data for Atlantic seawater are in excellent agreement with Nd isotopic measurements made on Atlantic ferromanganese sediments and are distinctly different from the observed compositions of Pacific samples. These results clearly demonstrate the existence of distinctive differences in the isotopic composition of Nd in the waters of the major ocean basins and are characteristic of the ocean basin sampled. The average eNd(0) values for the major oceans as determined by data from seawater and ferromanganese sediments are as follows: Atlantic Ocean, eNd(0) = -12 ± 2; Indian Ocean, eNd(0) = -8 ± 2; Pacific Ocean, eNd(0) = -3 ± 2. These values are considerably less than eNd(0) value sources with oceanic mantle affinities indicating that the REE in the oceans are dominated by continental sources. The difference in the absolute abundance of 143Nd between the Pacific and Atlantic Oceans corresponds to ab. 10**6 atoms 143Nd per gram of seawater. The correspondence between the 143Nd/144Nd in seawater and in the associated sediments suggests the possible application of this approach to paleo-oceanography. Distinctive differences in eNd(0) values are observed in the Atlantic Ocean between deep-ocean water associated with North Atlantic Deep Water and near-surface water. This suggests that North Atlantic Deep Water may be relatively well mixed with respect to Nd isotopic composition whereas near-surface water may be quite heterogeneous, reflecting different sources for surface waters relative to deep water. This suggests that it may be possible to distinguish the sources of water masses within an ocean basin on the basis of Nd isotopic composition. The Nd isotopic variations in seawater are used to relate the residence time of Nd and mixing rates between the oceans.

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: 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: From a structural and morphological point of view, the continental margin of southwestern Africa is a middle-aged "pull-apart" or "passive-type" margin which was initially created during the breakup of the supercontinent of Gondwanaland in the Mesozoic. The most important objective of the Leg 40 expedition was the attainment of strata laid down when the newly formed ocean was very young and only a few hundred kilometers wide. Site 361 was drilled at the fall of continental platform into the Cape Basin, to a sub-sea floor depth of 1314 meters and yielded sediments that range in age from upper Eocene to lower Aptian and possibly slightly older.

Description: he forty-first cruise of Glomar Challenger was devoted to the study of the evolution of the eastern basins of the North Atlantic, off the continental margin of West Africa. As the available data a the time was showing that most litho-stratigraphic units in the deep basins of the Atlantic had enough lateral extension, the drilling of a limited number of sites in key areas would allow for large-scale regional interpretation. One of the sites was loacted in the Cape Verde deep Basin (Site 367) while others were located in shallower waters such as, the Sierra Leone Rise (Site 366), the Cape Verde Rise (Site 368) or the Continental Slope off Spanish Sahara (Site 369).

Description: On cruises 10 and 15 of Academic Kurchatov (1971, 1973) at the Jan-Mayen Ridge, a large number of samples was obtained. Most of them contained sedimentary rocks. From their study, it is safe to assume that the rocks of the Jan-Mayen Ridge were, at first, subjected to subsidence to a considerable depth, and then uplifted to their contemporary position, by the ascending tectonic movements. Thus, the Jan-Mayen Ridge is in contrast to other Atlantic submarine ridges, not only in the sedimentary rock composition, but in the character of the tectonic movements.

Description: Leg 42, Part 1 of the Deep Sea Drilling Project was scheduled to continue the geological exploration of the Mediterranean. The strategy was to search for areas where the Mediterranean Evaporite formation had been largely or completely removed by erosion, such is the case for Site 372. For Leg 42, Part 2, the project entered the Black Sea. In particular, Site 379 was located the central portion of the Black Sea.

Description: The western part of the North Atlantic Ocean holds clues to some of the most intriguing questions in marine geology. But because the geologic problems are many and varied, the sites of Leg 44 were multipurpose in nature. In particular, some of the targets were : 1) the Blake Nose, a spur of the Blake Plateau, to determine the nature, age, and origin of reef-like structures recognized on seismic profiles and 2) the Blake Outer Ridge, a long low ridge of sediments that forms the eastern boundary of the Blake-Bahama Basin, where we hoped to study the stratigraphy and sample supposed clathrates.

Description: The JOIDES Paleoenvironment Panel had noted that the Neogene section had only been spot-cored on previous legs in the Western Atlantic (Legs 1, 2, 4, 11, and 43). The Panel accordingly requested that the complete section be recovered on Legs 51 through 53 in order to examine the transition from siliceous, Pacific-type Eocene sedimentation to non-siliceous sedimentation resulting from the gradual emergence of the Central American isthmus. It was also detremined to examine in detail the thick Cretaceous-Tertiary section overlying the basement.

Description: Thirty selected samples of pelagic and hydrothermal sediments retrieved on DSDP Leg 54 were chemically analyzed for major and minor oxide concentrations. Additionally, 11 samples of lithified carbonate sediments were petrologically studied. The pelagic sediments, which are described as foraminiferal biomicrite, were found to be generally higher in Fe and Zn, similar in Co content, and lower in Cu content, than the average Pacific pelagic sediments. Mineralogically, these samples are composed principally of calcite with minor amounts of quartz and clays. Hydrothermal sediments from Site 424 are divisible into three classes: (1) silica-rich, iron-poor smectites; (2) silica-poor, iron-rich mixtures of smectites and oxides; and (3) silica-poor, iron-rich materials, comprising mainly amorphous manganese oxides. Thus, two chemically distinct hydrothermal phases are recognizable: Class 1, iron-rich smectites, and Class 3, Mn-rich oxides and oxyhydroxides. Dolomite and pyrite were identified in X-ray diffraction studies of samples from Site 427.

Description: A near-bottom survey of a 24-km length of the East Pacific Rise (EPR) crest near the Leg 54 drill sites has established that the axial ridge is a 12- to 15-km-wide lava plateau, bounded by steep 300-meter-high slopes that in places are large outward-facing fault scarps. The plateau is bisected asymmetrically by a 1- to 2-km-wide crestal rift zone, with summit grabens, pillow walls, and axial peaks, which is the locus of dike injection and fissure eruption. About 900 sets of bottom photos of this rift zone and adjacent parts of the plateau show that the upper oceanic crust is composed of several different types of pillow and sheet lava. Sheet lava is more abundant at this rise crest than on slow-spreading ridges or on some other fastspreading rises. Beyond 2 km from the axis, most of the plateau has a patchy veneer of sediment, and its surface is increasingly broken by extensional faults and fissures. At the plateau's margins, secondary volcanism builds subcircular peaks and partly buries the fault scarps formed on the plateau and at its boundaries. Another deep-tow survey of a patch of young abyssal hills 20 to 30 km east of the spreading axis mapped a highly lineated terrain of inactive horsts and grabens. They were created by extension on inward- and outwardfacing normal faults, in a zone 12 to 20 km from the axis. Sediments sampled on the rise crest and flanks are mixtures of calcareous ooze and metalliferous precipitates, and they have been redistributed by southerly currents with average velocities of 9 cm/s.

Description: A submersible dive on a turbidite-covered spreading axis in Guaymas Basin photographed and sampled extensive terraces and ledges of talc. The rock contains siliceous microfossils, smectite, and euhedral pyrrhotite as well as rather pure iron-rich talc. Sulfur and oxygen isotopes indicate precipitation around a hydrothermal vent, at about 280°C.

Description: Leg 55 was conceived as part of the decade-long experiment to test the kinematic hot-spot hypothesis and several of its more imporant corollaries for the origin of the Hawaiian-Emperor chain. Also of particular importance was the question of whether the Hawaiian hot spot has remained fixed in the mantle. The specific primary objectives of Leg 55, were to determine (1) whether the known increase in the age of the volcanoes on the Hawaiian chain with distance from Kilauea continues northward along the Emperor Seamounts; (2) whether the lavas of the Emperor volcanoes are of the same chemical composition and were erupted in the same sequence as those of Hawaiian volcanoes; (3) the latitude of formation of Suiko Seamount as a test of hot-spot fixity; and (4) whether the Emperor Seamounts were once islands and, if so, to determine their post-volcanic and subsidence history.

Description: Aragonite mineralization was observed in serpentinized peridotites from the Romanche and Vema Fracture Zones in the Atlantic and the Owen Fracture Zone in the Indian Ocean, either in veins or as radial aggregates in cavities within the serpentinites. Evidence of incipient dissolution of the aragonite crystals was observed in one case. The aragonites tend to have lower Mg content (〈 0.03%) and higher Sr content (〉 0.95%) relative to other marine aragonites. Their 18O16O, 13C12C and 87Sr86Sr isotopic ratios suggest the aragonite was deposited at ocean floor temperatures from solutions derived from sea water circulating in fissures and fractures within the ultramafic rocks. The 18O16O ratios of the serpentines indicate serpentinization occurred at higher temperatures, probably deeper in the crust. Low-T reactions between circulating seawater and Mg-silicates (primarily serpentine and pyroxenes) caused high pH and enrichment of Mg and Ca in the solution, conditions favoring carbonate precipitation. Aragonite was formed rather than calcite presumably because the high Mg2+ concentration in the solution inhibited calcite precipitation. The high Sr content of the aragonites is probably related, at least in part, to their low temperature of formation. Opaque mineral grains containing over 8% NiO and over 40% MnO were observed concentrated along the margins of some of the aragonite veins, suggesting that Ni is one of the elements mobilized during reactions between ultramafic rocks and circulating seawater.

Description: The JOIDES Active Margin Panel for Leg 58 decided that the drilling would occur in the north Philippine Sea, namely, the Shikoku Basin, the Daito Ridge and Basin province. The Shikoku Basin sites were selected to solve several problems concerning back-arc basins formed by ocean-floor spreading. The main objectives were: (1) to determine the age of the oldest sediment, so as to calibrate magnetic-anomaly ages and to provide a test for various spreading models suggested for the basin; (2) to investigate the mineralogy, petrology, and chemistry of basalt samples recovered by drilling, and to compare there basalts with those of midocean ridges, so as to understand the nature and source of magmatic materials in these basins; (3) to determine the distribution of sediment types in time, and to relate that distribution to the tectonic history of the basin.

Description: The Japan Trench area was identified a favorable place for studying convergent margins during the initial deliberations of the IPOD Active Margins Panel. The Leg 56-57 DSDP drill sampling along the Japan Trench transect has indicated that material tectonically accreted during the present convergent episode is limited to a surprisingly small zone. The limits seem well established by the seaward extent of crust with continental thickness and lithologies and by the age and thickness of a terrigenous slope apron covering the presumed but probably unsampled accreted oceanic material.

Description: 40Ar/39Ar incremental heating experiments on three samples dredged from Jingu Seamount indicate that Jingu is 55.4 ± 0.9 m.y. old — older than the Hawaiian-Emperor bend and younger than the two dated Emperor Seamounts to the north. Major-oxide chemistry and petrography show that the samples are similar to hawaiites and mugearites from the Hawaiian Islands. By analogy with Hawaiian alkalic volcanic rocks, groundmass plagioclase compositions (An40-47) indicate that the three Jingu samples are probably mugearites. These results suggest that Jingu is a Hawaiian-type volcano and that the Emperor volcanoes become progressively older from south to north, as predicted by the hot-spot hypothesis.

Description: Forty basaltic rocks collected by submersible during the Cyamex expedition (1978) on the East PacifIc Rise at 21°N, a moderately fast spreading segment (6 cm/year opening rate) of the mid-ocean ridge, consist of angular pillow fragments and glass buds, sheet-flow slabs and samples of columnar pillars standing in collapsed fossillava pools. Most of the rocks are from the crestal are a of the Rise. The collection shows a striking petrographic homogeneity wh en compared with the range of basalts found on other segments of midocean ridges: olivine-phyric, or highly plagioclase-phyric rocks, so common in the slowspreading Famous are a in the Atlantic, are absent. All samples are typical lowpotassium oceanic tholeiites with a limited fractionation trend. Pillow-lavas, thin and thick sheet-flows cannot be distinguished by their major element compositions, as in the Galapagos rift which has the same spreading rate as the EPR at 21°N. Further, ferrobasalts have been described from the Galapagos rift, but do not appear in the Cyamex rocks. In the Cyamex area, olivine and plagioclase are the main silicate phases, and clinopyroxene is absent. In the pillows and sheet-flow samples, four generations of olivine and plagioclase crystals are distinguished. Samples from the fossillava pools are aphyric. The corresponding magma batches are presumed to have migrated rapidly through the magma chamber, and to have been extruded in large volumes, possibly during episodes ofhigh instantaneous opening rate. Fe-Ni and Fe-Cu-rich sulphide phases are common in an lava types as massive globules scatterred through the glass, or as microglobules decorating the walls of empty vesicles. Palagonite and Fe-Mn oxide thicknesses across the strike of the Rise indicate relative ages compatible with successive extrusions at the Rise axis.

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: Methods of estimating manganese nodule grade and concentration were investigated using bottom photographs from a well-explored east-central Pacific manganese nodule deposit.

Description: Three ferromanganese nodules handpicked from the tops of 2500 cm**2 area box cores taken from the north equatorial Pacific have been analysed for their U-Th series nuclides. 230Thexc concentrations in the surface 1-2 mm of the top side of the nodules indicate growth rates of 1.8-4.6 mm/10**6 yr. In two of the nodules a significant discontinuity in the 230Th exc depth profile has been observed at ~0.3 m.y. ago, suggesting that the nodule growth has been episodic. The concentration profiles of 231Pa exc (measured via 227Th) yield growth rates similar to the 230Th exc data. The bottom sides of the nodules display exponential decrease of 230Th exc/232Th activity ratio with depth, yielding growth rates of 1.5-3.3 mm/10**6 yr. The 230Th exc and 231Pa exc concentrations in the outermost layer of the bottom face are significantly lower than in the outermost layer of the top face. Comparison of the extrapolated 230Thexc/232Th and 230Th exc/231Pa exc activity ratios for the top and bottom surfaces yields an "age" of (5-15) x 10**4 yr for the bottom relative to the top. This "age" most probably represents the time elapsed since the nodules have attained the present orientation. The 210Pb concentration in the surface ~0.1 mm of the top side is in large excess over its parent 226Ra. Elsewhere in the nodule, up to ~1 mm depth in both top and bottom sides, 210Pb is deficient relative to 226Ra, probably due to 222Rn loss. The absence of 210Pbexc below the outermost layer of the top face rules out the possibility of a sampling artifact as the cause of the observed exponentially decreasing 230Thexc and 231Paexc concentration profiles. The flux of 210Pbexc to the nodules ranges between 0.31 and 0.58 dpm/cm**2/yr. The exhalation rate of 222Rn, estimated from the 226Ra-210Pb disequilibrium is ~570 dpm/cm**2/yr from the top side and 〉2000 dpm/cm**2/yr from the bottom side. 226Ra is deficient in the top side relative to 230Th up to ~0.5-1 mm and is in large excess throughout the bottom. The data indicate a net gain of 226Ra into the nodule, corresponding to a flux of (24-46) x 10**-3 dpm/cm**2/yr. On a total area basis the gain of 226Ra into the nodules is 〈20% of the 226Ra escaping from the sediments. A similar gain of 228Ra into the bottom side of the nodules is reflected by the high 228Th/232Th activity ratios observed in the outermost layer in contact with sediments.

Description: Determination of radium, thorium, uranium isotopes, and 210Pb in sediments and sediment pore waters from North Equatorial Pacific deep-sea clay-silicous oozes shows that the radium and uranium isotopes are mobile in the pore water. The concentration-depth profiles of radium can be understood in terms of a diagenetic model which takes into account mixing of sediment particles by bioturbation, molecular diffusion in the pore water, adsorption onto particle surfaces, as well as radioactive production and decay. The 234U/238U activity ratios in several samples are higher than the seawater value, indicating some enrichment of 234U in the pore water. However, the absolute concentrations of 238U and 234U are 25% lower than those in seawater, suggesting that the sediments form a sink for uranium isotopes. 210Pb is present in the pore water at concentrations approx. 20% that of 226Ra. The origin of 210Pb in the pore water is uncertain and could be due either to its in situ mobilization in the sediments or subsequent production in the laboratory from the decay of 222Rn. 230Th is present in measurable concentrations in the pore waters, but its distribution does not show any systematic trend with depth or other parameters. The most likely source of 230/Th appears to be minute amounts of sediment particles collected in the pore waters during the squeezing operation.

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: We report here that a manganese nodule from the Central Pacific manganese nodule province has been dated by fossil diatoms found in mud scraped from near the nodule's centre. The nodule was taken at DOMES Site B from Core B55-56 at 11°50.3'N and 137°28.2'W in a water depth of 4,892 m. It was resting on the sediment surface, with about 1.5 cm of the nodule bottom (of a total nodule height of 4.2 cm) buried in the mud. The top surface of the nodule was covered with a smooth manganese coating, but the bottom had a very rough, crusty texture. It was found that recent mud had leaked in through cracks in the nodule bottom, but that there were no pre-Pleistocene diatoms in this material. The date obtained was compared with the growth rate determined by the 230Th excess method and found to be in reasonable agreement. This study adds to the work of Harada1,2 on the biostratigraphy (mainly coccoliths) of manganese nodules.

Description: The bulk chemical compositions of ferromanganese nodules recovered from 14 of 38 sediment cores collected from a 230 km2 area of abyssal hill topography in the northern equatorial Pacific (8° 20'N, 153° 0'W; regional depth 5000 m) vary nonrandomly between fairly wide limits. The nodules have Mn/Fe ratios ranging from 2.60 to 5.38 and all samples contain todorokite and delta-MnO2 . The variation in the Mn/Fe ratio is governed by the total Fe contents of the nodules; Mn varies to a much smaller extent. Cu and Ni contents average about 1% and vary independently of the Mn contents. The compositional variation in the nodules is related to two features of the associated sediments, which are siliceous pelagic clays. The total Fe contents correlate positively with the oxalate-soluble Fe contents of the surface (0-2 cm) sediments; and their Mn/Fe ratios correlate negatively with the accumulation rates of the sediments. It is suspected that the composition of the nodules is influenced to a considerable extent by diagenetic reactions in the sediments, the clearest manifestation of this being the transformation of oxyhydroxide Fe into an insoluble form, possibly by the formation of smectite. This in turn leads to the formation of relatively Fe-poor ferromanganese nodules. Such nodules occur on slowly accumulating sediments where relatively more diagenetic reaction in the sediments has taken place.

Description: Excess 230Th dominates the alpha activity of the surface regions of manganese nodules and deep sea sediments. If uranium series eguilibrium is maintained, total alpha activity depth profiles should be as useful in determining sedimentation rates as are 230Th measurements. We have used cellulose nitrate alpha track recorders pressed against manganese nodule slabs to record high resolution alpha activity "maps' of a large number of nodules. Total alpha activity profiles have also been obtained for several sediment cores. From the approximately 90 nodule profiles measured to date, 73 show simple, approximately exponential depth dependence; about 2/3 of these have inferred deposition rates of 4-10 mm/10power6 yr. Ten profiles show statistically significant breaks in slope, suggesting growth rate changes. Within single dredge hauls there is little variation in growth rates, although different portions of the same nodule sometimes exhibit different growth rates. There is no correlation between depth and measured growth rate, except for a general tendency for the few Atlantic Ocean nodules we have measured to have slightly lower rates than Pacific or Indian Ocean samples. For a number of nodules and sediments the alpha track results have been compared with 230Th-based deposition rates measured by other workers. Two nodules have 230Th rates (W. S. Broecker et al., pers. comm.) identical within errors to the alpha track determinations. A third nodule (S. Krishnaswami, pers. comm. ) and two sediment cores previously measured by Goldberg and Koide (E. Sci. and Meteoritics, 1963, p. 90} all have much slower rates based on 230Th measurements compared with the alpha track results.

Description: This report presents megascopic descriptions of deep-sea sediment cores obtained by personnel of the Hawaii Institute of Geophysics on cruises of the R/V Kana Keoki in the eastern Pacific Ocean during the year 1978.

Description: The extent of substitution of Fe by Al in goethite in 32 lake ore samples collected from 11 lakes in Finland varied between 0 and 23 mol-%. The data indicated a negative relationship between Al-substitution and the particle size of lake ore. Differences in the Al-substitution were apparent between sampling sites, suggesting that kinetic and environmental variation in lake ore formation influences the substitution. Non-substituted goethite is formed in coarse-grained sediments with locally high concentrations of Fe due to iron-rich springs. Unit cell edge lengths and volumes of goethite varied as function of Al-subsitution but deviated from the Vegard relationship towards higher values.

Description: Fossil Mn nodules of Cretaceous age from western Timor exhibit chemical, structural and radioisotope compositions consistent with their being of deep-sea origin. These nodules show characteristics similar to nodules now found at depths of 3,500-5,000 m in the Pacific and Indian Oceans. Slight differences in the fine structure and chemistry of these nodules and modern deep-sea nodules are attributed to diagenetic alteration after uplift of enclosing sediments.

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.