ALBERT

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: 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: 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: 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: 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: 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: 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: Cores, submarine photography and dredges described in this report were taken during the R/V Melville Cruise Vulcan-1 in September 1980 by the School of Oceanography, Oregon State University. This cruise was part of the International Decade of Ocean Exploration (IDOE) Manganese Nodule Program (MANOP). It surveyed MANOP Sites H and M in the Pacific Ocean.

Description: The oxide portion of marine manganese nodules deserves intensive study because it probably reflects directly the conditions under which nodules form in the Bea. A better understanding of the nature of the oxides in nodules should therefore throw new light on basic problems of nodule origin.

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: 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: 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: 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: An area of about 22,000 km² on the northern Blake Plateau, off the coast of South Carolina, contains an estimated 2 billion metric tons of phosphorite concretions, and about 1.2 billion metric tons of mixed ferromanganese-phosphorite pavement. Other offshore phosphorites occur between the Blake Plateau and known continental deposits, buried under variable thicknesses of sediments. The phosphorite resembles other marine phosphorites in composition, consisting primarily of carbonate-fluorapatite, some calcite, minor quartz and other minerals. The apatite is optically pseudo-isotropic and contains about 6% [CO3]**2- replacing [PO4]**3- in its structure. JOIDES drillings and other evidence show that the phosphorite is a lag deposit derived from Miocene strata correlatable with phosphatic Middle Tertiary sediments on the continent. It has undergone variable cycles of erosion, reworking, partial dissolution and reprecipitation. Its present form varies from phosphatized carbonate debris, loose pellets, and pebbles, to continuous pavements, plates, and conglomeratic boulders weighing hundreds of kilograms. No primary phosphatization is currently taking place on the Blake Plateau. The primary phosphate-depositing environment involved reducing conditions and required at least temporary absence of the powerful Gulf Stream current that now sweeps the bottom of the Blake Plateau and has eroded away the bulk of the Hawthorne-equivalent sediments with which the phosphorites were once associated.

Description: Methods of estimating manganese nodule grade and concentration were investigated using data from a well-explored east-central Pacific manganese nodule deposit. Bulk chemical analyses of 159 nodules recovered from 21 box cores show that the range in metal values between nodules from a single box core is commonly small but may be greater than the range in mean metal content of nodules from widely separated box cores. The metal exhibiting the greatest variability in the 21 box cores is Zn, followed in decreasing order by Cu, Mn, Co, Ni, and Fe. Approximately half of the box cores required analysis of 11 nodules or more to predict metal content within plus or minus 10 percent of the mean value.

Description: A model that predicts the flux of 222Rn out of deep-sea sediment is presented. The radon is ultimately generated by 230Th which is stripped from the overlying water into the sediment. It is shown that the continental contribution of ionium is not significant, and that at low sedimentation rates, biological mixing and erosional processes strongly affect the surface concentration of the ionium. Two cores from areas of slow sediment accumulation, one from a manganese nodule region of the central Pacific and one from the Rio Grande Rise in the Atlantic were analyzed at closely spaced intervals for 230Th, 226Ra, and 210Pb. The Pacific core displayed evidence of biological mixing down to 12 cm and had a sedimentation rate of only 0.04 cm/kyr. The Atlantic core seemed to be mixed to 8 cm and had a sedimentation rate of 0.07 cm/kyr. Both cores had less total excess 230Th than predicted. Radium sediment profiles are generated from the 230Th model. Adsorbed, dissolved, and solid-phase radium is considered. According to the model, diffusional losses of radium are especially important at low sedimentation rates. Any particulate, or excess radium input is ignored in this model. The model fits the two analyzed cores if the fraction of total radium available for adsorption-desorption is about 0.5-0.7, and if K, the distribution coefficient, is about 1000. The flux of radon out of the sediments is derived from the model-generated radium profiles. It is shown that the resulting standing crop of SUP-222 Rn in the overlying water may be considered as an added constraint in budgeting 230Th and 226Ra in deep-sea sediments.

Description: In 1972, the Sea Scope Expedition was commissioned by Hughes Tool Company and carried out by Global Marine Development, Inc. The object was to gather detailed information on manganese nodules, including distribution, metallic content, methods of recovery, and sea floor bathymetry in noduliferous areas. Five of six planned cruise legs were successful. The resulting report is divided into three sections.

Description: Specimens dredged from within the summit of a volcanic seamount during an oceanographic cruise in the Eolian Island Arc (South Tyrrhenian Sea) where examined. Mineralization, which forms veins and pockets within a silty-clayey material, consists mainly of todorokite with scarce birnessite. The chemistry (Mn 48%, Fe 0.26 %, Ni 249 ppm, Co 223 ppm) and the mineralogy of the deposit are discussed; the findings, compared with data from some of the literature, suggest a hydrothermal genesis with extreme fractionations of Mn from Fe. A process explaining the anomalous Cu content (8 200 ppm) of the deposit is also suggested.

Description: The purpose of this volume, the eighth in a series of similar publications (Goodell, 1964, 1965, 1968; Frakes 1971, 1973 ; Cassidy et al., 1977a, 1977b), is to continue a presentation to the research community of sediment core descriptions and attendant data of cored and otherwise obtained sediments retrieved in waters of the Southern Ocean aboard the research vessel, ARA Islas Orcadas (formerly, USNS Eltanin), as a part of the circumpolar survey begun by Eltanin in 1962 (see issue of Antarctic Journal of the United States, Vol. 8, No. 3, 1973). The data presented herein are concerned with the results of coring activities aboard cruise 1176 of Islas Orcadas, the second marine geology coring cruise of this vessel under the terms of the present United States-Argentine agreement. The core descriptions are organised as follows: 1) a brief summary of the coring objectives of the cruise, together with a discussion of core recovery; 2) a table and map of station location data for materials retrieved; 3) a table of tentative age-dates for each piston core; 4) an explanation of the laboratory procedures and descriptive criteria used in the description of the sediments, and 5) lithologic descriptions of the piston and trigger cores, and the piston and trigger core bag samples.

Description: The purpose of this volume, the seventh in a series of similar publications (Goodell, 1964, 1965, 1968; Frakes 1971, 1973 ; Cassidy et al., 1977), is to continue a presentation to the research community of sediment core descriptions and attendant data of cored and otherwise obtained sediments retrieved in waters of the Southern Ocean aboard the research vessel, ARA Islas Orcadas (formerly, USNS Eltanin), as a part of the circumpolar survey begun by Eltanin in 1962 (see issue of Antarctic Journal of the United States, Vol. 8, No. 3, 1973). The data presented herein are concerned with the results of coring activities aboard cruise 0775 of Islas Orcadas, the second marine geology coring cruise of this vessel under the terms of the present United States-Argentine agreement. The core descriptions are organised as follows: 1) a brief summary of the coring objectives of the cruise, together with a discussion of core recovery; 2) a table and map of station location data for materials retrieved; 3) a table of tentative age-dates for each piston core; 4) an explanation of the laboratory procedures and descriptive criteria used in the description of the sediments, and 5) lithologic descriptions of the piston and trigger cores, and the piston and trigger core bag samples.

Description: The purpose of this volume, the tenth in a series of similar publications (Goodell, 1964, 1965, 1968; Frakes 1971, 1973 ; Cassidy et al., 1977), is to continue a presentation to the research community of sediment core descriptions and attendant data of cored and otherwise obtained sediments retrieved in waters of the Southern Ocean aboard the research vessel, ARA Islas Orcadas (formerly, USNS Eltanin), as a part of the circumpolar survey begun by Eltanin in 1962 (see issue of Antarctic Journal of the United States, Vol. 8, No. 3, 1973). The data presented herein are concerned with the results of coring activities aboard cruise 1578 of Islas Orcadas, the fourth marine geology coring cruise of this vessel under the terms of the present United States-Argentine agreement. The core descriptions are organised as follows: 1) a brief summary of the coring objectives of the cruise, together with a discussion of core recovery; 2) a table and map of station location data for materials retrieved; 3) a table of tentative age-dates for each piston core; 4) an explanation of the laboratory procedures and descriptive criteria used in the description of the sediments, and 5) lithologic descriptions of the piston and trigger cores, and the piston and trigger core bag samples.

Description: Chemical analyses of manganese nodules from the Central Pacific Basin show that their chemical composition varies regionally, although that of the associated sediments is markedly uniform throughout the basin. Mn content varies from 16 to 32% in average. Its higher value is generally found in nodules from siliceous clay and a few from deep-sea clay. Fe content tends to enrich in nodules from deep-sea clay area. Most manganese nodules, except those from deep-sea clay, are remarkably depleted in Fe compared with ones from the other Pacific regions. Mostly, Cu and Ni contents exceed 1% in nodules from siliceous clay, and decrease towards the northwest of the basin where deep-sea clay is distributed. The inter-element relationship between manganese nodules and associated sediments suggests that the mechanism of incorporation of major and minor elements in nodules is apparently different from that of the associated sediments. This finding seems to provide a new interpretation on the problem why manganese nodules having low accumulation rate are not buried by the associated sediments with greater sedimentation rate and then occur on sediment-seawater interface.