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: 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: The lipids and kerogens of 15 sediment samples from Site 547 (ranging from Pleistocene to Early Jurassic/Triassic) and 4 from Site 545 (Cretaceous) have been analyzed. A strong terrestrial contribution of organic matter was found, and significant autochthonous inputs were also present, especially at Site 545. Both strongly reduced and highly oxidized sediments have been found in the Cenozoic and Jurassic samples of Site 547. On the contrary, all the Cretaceous sections of Sites 547 and 545 are anoxic. Sediments from anoxic paleoenvironments are immature and have a high content of sterenes, diasterenes, steradienes, hopenes, and ßß hopanes. Samples from oxic paleoenvironments are mainly mature and their content of hopenes and steriod structures is below the detection level. Nevertheless, their hopane distributions have the immature ßß homologs as the predominant molecular markers. For Site 545 the most abundant molecular markers are ring A monoaromatic steranes, and their presence is attributed to microbial and chemical transformations during early diagenesis.

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 occurring within marine sediments of presumably Upper Miocene-Lower Pliocene age from cores obtained by the Argentine oceanographic vessel ARA Islas Orcadas in 1977 on the Malvinas (Falkland) Plateau and neighbouring Scotia Sea were studied with the aim of comparing them with other fossil nodules found on the mainland of Argentina that were also ascribed to the marine environment. After optical mineralogical, chemical, X-ray and trace element analysis, the studied "nodules" proved to be actually wacke clasts cemented by manganese oxides with a high Fe/Mn ratio corresponding to a continental environment. The studied "nodules" thus differ from the Argentine mainland nodules and are supposed to have been transported from continental environments and then deposited in the marine realms. The wacke clasts became then nuclei for the deposition of the marine manganese oxides of the coatings. The proportion of trace elements, which is high, suggests the growth of the nodules in the marine environment.

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: Manganese nodules have been analysed at the Scripps Institution of Oceanography after having been ground to to a diameter less than 74 microns. Some analysises were performed on pellets by X-ray Emission Spectroscopy for 1000 Seconds. All concentrations have been corrected to 110 degrees Celsius drying conditions (see: https://doi.pangaea.de/10.1594/PANGAEA.854202).

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: Morphological, mineralogical and chemical analysis are reported for a metalliferous encrustation from a seamount in the Gulf of Guinea, South Atlantic. The results are compared with published data on encrustation from similar environments. The morphology and mineralogy indicate a crust formed on the exposed rock surface with some agglutination of foram debris. Comparison of the abundance patterns for transition elements with that of known data suggests that some enrichment had resulted from the high primary productivity at this site.

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: 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: Mesozoic benthic foraminifers, recovered from five single-bit holes drilled in the southern Gulf of Mexico on Deep Sea Drilling Project Leg 77 are rare, poorly preserved, and scattered throughout the dominantly redeposited sediments. The Mesozoic sequence at basin Sites 535 and 540 consists largely of laminated limestone with smaller amounts of skeletal limestone and pure pelagic limestone, whereas the Mesozoic sediments at basement Sites 536, 537, and 538 (Hole 538A) consist largely of oolitic-oncolitic limestone.

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: 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: The main objective of the cruise was to study the sediments and sedimentary processes in an area known as Great Meteor East (GME) - part of a feasibility study into the ocean disposal of high-level radioactive waste commissioned by the Department of the Environment. Previous cruises (Discovery 118, 126, 134 and Farnella 3/81) had done much of the ground work, consequently the area was already well known but not necessarily well understood for the purposes of our investigation.

Description: The drilling plan for Leg 74 of the Deep Sea Drilling Project was designed to address three main scientific topics: (1) the history of the deep-water circulation in the southeastern Atlantic, (2) the nature and geologic evolution of the Walvis Ridge, and (3) the biostratigraphy and magnetic stratigraphy of this region. In order to study these subjects, a suite of five sites was drilled on the Walvis Ridge that extended from its crest (near 1000 m water depth) down its northwest flank into the Angola Basin to a depth of 4400 m.

Description: Leg 73 was the middle of five legs on South Atlantic paleoenvironments planned by the JOIDES Ocean Paleoenvironment (OP) Panel during the years from 1975 to 1980. The idea of drilling a transect of holes across the 30°S parallel was entertained soon after the drilling on Leg 3, during the first phase of the Deep Sea Drilling Project (1968/69), when the surprising discovery was made that the middle Miocene sediments of the South Atlantic were largely marls and red clays. The deposition of the red clays was obviously related to the intense dissolution of calcite during the middle Miocene, when the calcite-compensation level was elevated. The objectives and tactical planning for a transect across the east flank of the Mid-Atlantic Ridge just north of 30°S were outlined by the OP Panel more fully to the Planning Committee in July of 1978. After a piston core containing Paleocene sediments was taken in 1979 at the site in the Cape Basin at the foot of the Walvis Ridge this area was designated for DSDP Leg 73 and 74.

Description: Site 530 is located in the southeastern corner of the Angola Basin, about 20 km north of the Walvis Escarpment, near the eastern end of the easternmost (or Frio) segment of the Walvis Ridge. It lies on the abyssal floor of the Angola Basin and exhibits a seismic stratigraphic sequence typical for the entire deep part of the basin. It was selected because it appears to have the oldest strata in the region preserved in a sediment pond between low basement rises.

Description: The drilling of Leg 77 is part of an overall program by the JOIDES Passive Margin Panel to study the evolution of the western North Atlantic passive margin. The history of the central North Atlantic is probably the best known of all ocean basins, but the origin and history of the neighboring Gulf of Mexico are very much uncertain. Some geologists consider it the oldest ocean basin still in existence (Paleozoic), but others doubt the existence of "true" oceanic crust under the central Gulf. The nature and origin of the transitional crust and the overlying Mesozoic sedimentary sequences in the southeastern Gulf, therefore, was the main objective of Leg 77.

Description: The principal goal of Site 543 was definition of an oceanic reference section. One of the specific objectives was to provide a physical-property profile through the undisturbed oceanplate section and thereby a basis for measuring the tectonic consolidation of any offscraped rocks of similar lithology in the area of the Tiburon and Barracuda rises which constitute prominent highs emerging from the Atlantic abyssal plain and presently intersecting the deformation front of the Barbados Ridge complex.

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: 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: 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 major and minor element composition of ferromanganese nodules from DOMES Site A has been determined by X-ray fluorescence methods. Three phases appear to control the bulk compositions: Mn and Fe oxyhydroxides and aluminosilicates. Relatively wide compositional variations are evident throughout the area. Nodules with high Mn/Fe ratios, high Cu, Mg, Mo, Ni and Zn concentrations and high todorokite/-MnO2 ratios have gritty surface textures and are confined to an east-west trending depression with thin Quaternary sediment cover. Nodules with low Mn/Fe ratios, high concentrations of As, Ca, Ce, Co, La, P, Sr, Ti, V, Y and Zr and low todorokite/-MnO2 ratios have smooth surfaces and are confined to shallower areas with relatively thick Quaternary sediment to the north and south of the depression. All nodules in the area have compositions which are influenced by diagenesis, but those with the most marked diagenetic signature (high Mn/Fe and Cu/Ni ratios, low Ce/La ratios and more todorokite) are found in areas of very slow or non-existent sedimentation; many of these nodules are actually in contact with outcropping Tertiary sediment. This paradox may be resolved by postulating, by analogy with some shallow-water occurrences, that the nodules accrete from bottom waters which have enhanced particulate and dissolved metal contents derived from diagenetic reaction in areas remote from the site of nodule formation. The metals are supplied in a bottom flow (probably Antarctic Bottom Water) which also erodes, or prevents modern sedimentation in, the depression. Nodules on the flanks of the depression are not evidently affected by this flow and derive at least pan of their constituent metals from diagenetic reaction in the underlying Quaternary sediment. Apparently, abyssal diagenetic nodules can have an immediate and a remote diagenetic metal source. Metal fluxes derived from pore water dissolved metal gradients may not be relevant to particular accreting nodules if a significant fraction of their metals is derived from outside the area in which they form.

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: Measurements of Pb-210 activities, in conjunction with micropaleontological, geotechnical and sedimentological observations, on sediment cores have been used to characterize two distinctive bioturbation regimes on the continental slope and rise east of Newfoundland. On the rise (2600 m), excess Pb-210 is confined to the upper few centimeters of the coarser-grained sediments underlying the axis of the Western Boundary Undercurrent. The geological and geochemical evidence for a low rate of bioturbation in this high bottom current regime is consistent with a reduced population of deeper burrowing macrofauna, particularly the species Maldane sarsi. In contrast, a higher flux of organic-rich, fine-grained particulate material to the middle slope (1500 m water depth), and the comparatively stable sedimentological conditions that prevail in this low bottom current regime, have led to the active colonization of the sediment substrate by bioturbating organisms. Enhanced mixing of middle slope deposits is reflected by comparatively lower shear strengths within the upper 30 cm of the sediment column, and by the reduced variability of the sediment-depth distribution of the most abundant species of foraminifera. Excess Pb-210 has been transported downward from the sediment-water interface to depths greater than 12 cm. Some Pb-210 profiles from the middle slope can be interpreted in terms of a diffusion mixing model for which the biological mixing coefficients are of the order of 0.10-1.0 cm2/yr.Measurements of the two and three dimensional distribution of excess Pb-210 in one middle slope box core indicate that the mixing process in these sediments has a pronounced heterogeneous component on time scales of the same order as the half life of Pb-210 (22.3 yr). Spatial correlations between Pb-210 anomalies and artifacts of bioturbation observed in x-radiographs of the core suggest that Pb-210 maxima observed at depth may be the result of an inclined orientation of burrow structures which have introduced a significant lateral component to the downward transport of surficial sediments.

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.

Description: Manganese nodules are considered to have accumulated in general very slowly: surface layers of nodules contain a large excess of 230Th, more than would be produced by uranium decay. The decrease of excess 230Th with depth within a nodule is generally interpreted to be due to the radioactive decay, and nodule accumulation rates were then estimated from this to be a few mm/Myr. How then do these nodules escape from burial by associated marine sediments which accumulate 3 orders of magnitude faster than the nodules? One possible explanation is that the radionuclides of interest were not incorporated in the nodule matrix during its growth but were adsorbed later. Subsequent inward diffusion of the radionuclides might result in an apparent radioactive decay. We have tested this hypothesis by measuring simultaneously two radionuclides of different half lives. If the gradients of the radionuclides are really due to the radioactive decay, then, assuming a constant growth rate for a nodule, we expect the profile of the shortlived nuclide to be steeper (because of its faster decay) than that of the longlived nuclide.

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: Relationships among Th and Ra isotopes in nodule, sediment and water phases at MANOP Site S establish the most likely source for Th in the nodules, the frequency of nodule turning, and the similarity of micro and macro nodules. Manganese nodules and bottom waters have 230Th/232Th activity ratios considerably higher than other phases at this site suggesting that sea water is the likely source of Th for the nodules. Similar 230Th/232Th activity ratios in nodule tops and bottoms and in certain cases departure from expected 226Ra/230Th activity ratios in nodule tops and bottoms indicate that the nodules rotate every one to ten thousand years. The micro nodules have diffusion coefficients of Ra similar to macro nodule bottoms. I suggest that they may act as a carrier phase for transporting metals through oxic sediments to nodules.