ALBERT

Description: Sediments in the area of the Galapagos hydrothermal mounds are divided into two major categories. The first group, pelagic sediments, are nannofossil oozes with varying amounts of siliceous microfossils. The second group are hydrothermal sediments consisting of manganese-oxide crust fragments and green nontronitic clay granules. Hydrothermal sediments occur only in the upper half to two-thirds of the cores and are interbedded and mixed with pelagic sediments. Petrologic evidence indicates that hydrothermal nontronite forms as both a primary precipitate and as a replacement mineral of pre-existing pelagic sediment and hydrothermal manganese-oxide crust fragments. In addition, physical evidence supports chemical equations indicating that the pelagic sediments are being dissolved by hydrothermal solutions. The formation of hydrothermal nontronite is not merely confined to the surface of mounds, but also occurs at depth within their immediate area; hydrothermal nontronite is very likely forming today. Geologically speaking, the mounds and their hydrothermal sediments form almost instantaneously. The Galapagos mounds area is a unique one in the ocean basins, where pelagic sediments can be diagenetically transformed, dissolved, and replaced, possibly within a matter of years.

Description: Clay minerals recovered from the Galapagos hydrothermal mounds (Holes 506C, 507D, and 509B) are mainly iron-rich nontronite-like minerals enriched in potassium. Nontronites from Hole 509B show a distinct tendency to become micaceous toward the lower beds of clay sediments. Mn-crusts consist mainly of todorokite or a mixture of todorokite and nontronite. Minerals of clay and Mnrich sediments in the mounds originated from hydrothermal solutions of uncertain origin. Pelagic oozes from hydrothermal mounds and from areas between mounds (Hole 506D) consist mainly of calcite. In the carbonate beds on or near the hydrothermal mounds an admixture of smectite is often found.

Description: Depth profiles of 10Be and 9Be concentrations have been measured in five manganese nodules from widely varying locations of the Pacific Ocean. Mean accumulation rate of these manganese nodules ranges from 2.7 to 8.0 mm/m.y.. The variation of 10Be and 10Be/9Be with depth or time is found to be less than ±30% for periods from 0.4-1.0 m.y. back to 6 m.y. B.P. Surface 10Be/9Be atomic ratio is found to be (9-13) x 10**-8, that shows authigenic nature of manganese nodule acuumulation by comparison with (12-31) x 10-8 for deep-sea water, (2-7) x 10**-8 for clay sediments and (7-9) x 10**-8 for fossil-rich sediments.

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.

Description: The D'Entrecasteaux Zone (Southwest Pacific) is an arched submarine horst- and graben structure, which extends from the northern end of the New Caledonia ridge to the western border of the New Hebrides island arc. A review of the bathymetry, seismic-reflection data, paleomagnetism, gravimetry, seismology and DSDP data available for this area is combined with a study of basaltic samples dredged along the horsts of this regional fracture zone. These basalts show strong petrographic and chemical affinities with MORB. Their fissiontrack ages range between 56 Ma (Paleocene-Eocene boundary) and 36 Ma (Eocene-Oligocene boundary). It is suggested that the D'Entrecasteaux Zone represents the northern arcuate extension of the northeast-dipping Eocene subduction/obduction zone, located along the New Caledonia/Loyalty Islands ridge, while its present morphology appeared from post-obduction extensional movements, resulting in a progressive uplift of basaltic ocean floor since Middle Miocene times.

Description: Manganese nodules collected from three areas (C, F, and G) on a N-S equatorial Pacific transect at 134° W by R. V. Sonne show differences in size, morphology, surface density and composition which can best be interpreted in terms of the biogenic theory of nodule formation. These data indicate that the biogenic hypothesis is central to an understanding of manganese nodule genesis in the equatorial Pacific and in particular influences the nodule shape, surface texture, rate of growth, composition, and mineralogy. The nodule characteristics in this region are also influenced by the hydrological characteristics of the bottom water, sedimentation rates, local geological and tectonic conditions (including seeding eflects) and topography.

Description: Ferromanganese micronodules have been found on Georges Bank, off the U.S. northeast coast, distributed throughout the surficial sediments within an area about 125 km long and at least 12 km wide. These coarse, sand-sized concretions have precipitated from metal-rich interstitial waters and contain many of the textural and structural features common to other neritic nodules. Most of the nodules have accreted around detrital grains, and X-ray powder diffraction analyses indicate the presence of geothite and vernadite ( delta -MnO sub(2)) in the ferromanganese layers. Chemical analyses of the micronodules, when compared with similar data on deep-sea manganese nodules, reveal lower Mn/Fe ratios, significantly higher concentrations of V and As, comparable values of Mo, and an order of magnitude less of Co, Ni, Ce and most other, metals.

Description: We analyzed the oxygen and carbon isotopic composition of planktonic and benthic foraminifers picked from 13 late Eocene to late Oligocene samples from DSDP Site 540 (23°49.73'N, 84°22.25'W, 2926 m water depth) from the Gulf of Mexico. An enrichment occurs in 18O of about 0.5 to 0.8 per mil in both benthic foraminifers and surface-dwelling planktonic foraminifers between the latest Eocene and early Oligocene. This early Oligocene maximum is followed by lower 18O values. A 1.2 per mil d13C decrease in both benthic and planktonic foraminiferal data occurs from the late Eocene to the late Oligocene. There is a correspondence of the 13C signal to deep-sea records; however, the amplitude of this change is greater than previously seen in deep-sea cores, possibly as a result of proximity to terrestrial sources of carbon. The covarying isotopic changes in both benthic and planktonic foraminifers suggest global causes, such as ice volume increases and increased terrestrial carbon input to the ocean. However, during the latter part of the record (early-late Oligocene), the increases in the benthic 18O without accompanying increases observed with planktonic foraminifers suggest that changes in only one part of the system occurred; one potential explanation being a decrease in bottom-water temperatures without concomitant changes in the surface waters. The 18O differences between species of planktonic foraminifers and the difference between planktonic and benthic 18O data indicate that diagenesis problems are minimal. These preliminary results are encouraging given that these cores are partially lithified.

Description: Characteristic black nodules have been retrieved in 1922 from the bed of the Kichijo River, that runs along the Tanakamiyama mountain in the Oni Province and ends into Lake Biwa in Japan. Their radiocativity has been studied along with that of crusts of similar nature found covering rock formations in the vicinity overlooking the stream. The high content in radium observed may be due to the high uranium content of the granite host rock typical of the Tanakamiyama formation.

Description: In recent years, metalliferous sediments have been discovered overlying newly generated oceanic crust in the East Pacific, North Atlantic, Indian Ocean, Red Sea, Gulf of Aden, and elsewhere (e.g., Boström, 1973; Lalou et al., 1977; Bischoff, 1969; Boström and Fisher, 1971; Cann et al., 1977, respectively). Such material has also been recovered by drilling from sediments lying upon older oceanic crust (Boström et al., 1972, 1976; Horowitz and Cronan, 1976). Hydrothermal circulation of seawater at a spreading ridge results in the leaching of Fe, Mn, and possibly other elements from the basaltic volcanic layer and their transport and discharge into ocean bottom waters, whereupon fine-grained Fe-Mn-rich precipitates form and settle into the ambient sediment (cf. Corliss, 1971; Dasch et al., 1971; Spooner and Fyfe, 1973; Bischoff and Dickson, 1975; Heath and Dymond, 1977; Corliss et al., 1979, Edmond et al., 1979). Mn-rich crusts have also been recovered from active ridges and are inferred to have formed in the vicinity of hydrothermal discharge areas (Scott et al., 1974; Moore and Vogt, 1976; Corliss et al., 1978; Hoffert et al., 1978). The source of the trace elements in the metalliferous deposits is generally not clear. They may be derived from seawater by adsorption onto the precipitates or crusts, or from hydrothermal solutions which have leached them from the basalts. Pb, however, can be used as a geochemical tracer because of the known isotopic compositional differences between oceanic basalts and seawater. Isotopic investigations of Pb in ferruginous sediments from the East Pacific have shown that it has been derived partly or mostly from a basaltic source (Bender et al., 1971; Dasch et al., 1971; Dymond et al., 1973). In the present study, Pb isotopic analyses have been made of a suite of metalliferous sediments (nontronite, Mn-oxide crust, Mn-Fe-oxide mud), pelagic sediments, and basalts from the Galapagos mounds area. The main purposes of the Pb study were to determine the source or sources of Pb in the metalliferous sediments, and whether or not stratigraphic variations exist in the isòtopic composition of Pb in the sediments.

Description: Basalt samples recovered during DSDP Legs 68, 69, and 70 from a 550-meter-thick section in two holes near the Costa Rica Rift (Holes 501 and 504B) were found to contain the following secondary minerals: trioctahedral and dioctahedral smectite, chlorite, mixed-layer clays, talc, hematite, pyrite, foujasite, phillipsite, analcime, natrolite, thomsonite, gyrolite, aragonite, calcite, anhydrite, chalcocite, Fe-hydrosilicate, okenite, apophyllite, actinolite, cristobalite, quartz, and magnesite. A less positive identification of bismutite was made. A mineral rich in Mn and minerals with strong reflections at 12.9 Å and 3.20 Å remain unidentified. Trioctahedral smectite replaces glass and olivine in the basalt groundmass. The other secondary minerals occur in veins. The distribution of the secondary minerals in the basalt section shows both hydrothermal and oxidizing-nonoxidizing zonation. Most of the secondary minerals formed under alkaline, nonoxidizing conditions at temperatures up to 120° C. An acidic regime probably existed in the lowest portion of basalt. Oxidative diagenesis followed nonoxidative diagenesis in the upper part of the section. Oxidative diagenesis is characterized by the absence of celadonite, rare occurrences of dioctahedral smectite, and widespread hematite and phillipsite.

Description: The cores and dredges described at this site were taken on the DRAKAR cruise from 1 March until 1 April 1983 by the Muséum National d'Histoire Naturelle from the R/V Marion Dufresne. A total of 45 cores and dredges were recovered along with underwater camera runs. They are available at MNHN for sampling and study.

Description: The cores and dredges described at this site were taken on the RIDA cruise from 1 May until 25 May 1984 by the Muséum National d'Histoire Naturelle from the R/V Marion Dufresne. A total of 45 cores and dredges were recovered along with underwater camera runs. They are available at MNHN for sampling and study.

Description: Basalt samples recovered during DSDP Legs 68, 69, and 70 from a 550-meter-thick section in two holes near the Costa Rica Rift (Holes 501 and 504B) were found to contain the following secondary minerals: trioctahedral and dioctahedral smectite, chlorite, mixed-layer clays, talc, hematite, pyrite, foujasite, phillipsite, analcime, natrolite, thomsonite, gyrolite, aragonite, calcite, anhydrite, chalcocite, Fe-hydrosilicate, okenite, apophyllite, actinolite, cristobalite, quartz, and magnesite. A less positive identification of bismutite was made. A mineral rich in Mn and minerals with strong reflections at 12.9 Å and 3.20 Å remain unidentified. Trioctahedral smectite replaces glass and olivine in the basalt groundmass. The other secondary minerals occur in veins. The distribution of the secondary minerals in the basalt section shows both hydrothermal and oxidizing-nonoxidizing zonation. Most of the secondary minerals formed under alkaline, nonoxidizing conditions at temperatures up to 120° C. An acidic regime probably existed in the lowest portion of basalt. Oxidative diagenesis followed nonoxidative diagenesis in the upper part of the section. Oxidative diagenesis is characterized by the absence of celadonite, rare occurrences of dioctahedral smectite, and widespread hematite and phillipsite.

Description: ree types of concretions were recovered during Leg 81 from Holes 552A, 553A, and 554A, located on the west margin of the Rockall Plateau. In the sedimentary section, these concretions are located at the level of major unconformities, in condensed sequences representing a period from early Eocene to Miocene. This study is a detailed mineralogical and geochemical investigation that permits comparison among the three holes and between the fossil Leg 81 concretions and recent polymetallic nodules found on the ocean floor.

Description: From the study of the ostracodes of Sites 516, 517, and 518 in comparison with those of Sites 21, 22, and 357, we can show that a time lag (early to late Oliogene) existed between the formation of the deep water masses (mid-bathyal ± 2000 m) and those of intermediate depths (upper bathyal ± 1000 m). The ostracode faunas suggest that while the Antarctic Intermediate Water (O2 = 4.5 to 5 ml/l) was flowing through the Vema Trough to fill the northern basins, the returning less-dense, warmer water (O2 = 3.5 to 5 ml/l) originating in Tethys was being gradually displaced upslope. Efforts to identify shallow (less than 200 m) faunas were unsuccessful. No evidence of significant changes in paleodepth or close proximity to islands could be found that could not be better explained by water-mass changes. Studies of the genera Poseidonamicus and Krithe suggest an important water mass change at about 14 Ma (late-middle Miocene), but the cause of this event is not yet understood.

Description: From 661 to 880 m beneath the seafloor at DSDP Sites 370 and 416 are Albian to Barremian claystone with some limestone, sandstone, and siltstone. Compressional-wave velocities ranged from 1.70 to 4.37 km/s, with an average in situ vertical velocity of 1.93 km/s. From 880 to 1430 m are Hauterivian to Valanginian turbidites of alternating graded calcareous and quartzose cycles from siltstone or fine sandstone to mudstone. Compressional-wave velocities range from 1.80 to 4.96 km/s with an average in situ velocity of 2.61 km/s. From 1430 to 1624 m are early Valanginian to Tithonian (Kimmeridgian?) turbidites, with alternating quartzose siltstone grading to mudstone cycles with hard micritic limestone and calcarenite (calciturbidites). Compressional-wave velocities range from 2.26 to 5.7 km/s, with an average in situ vertical velocity of 3.25 km/s. Acoustic anisotropy is 0 to 30% faster parallel to bedding in Cretaceous to Tithonian sandstone-siltstone turbidites in mudstone and minor limestone from 661 to 1624 m below the seafloor. Between 2.0(?) km/s and 4.2(?) km/s, anisotropy becomes particularly significant (below 1178 m), where the anisotropy is about + 0.4 km/s or greater. The mudstone, softer sandstone, and softer siltstone tend to have velocities around 2.0 to 2.5 km/s; the cemented sandstone and limestone cluster around 2.5 km/s to 4.2 km/s; thus the relative percentage anisotropy is greater for lower-velocity lithologies. Above 4.2(?) km/s, the well-cemented sandstone and limestone tend to have a smaller (less than + 0.4 km/s) absolute anisotropy, and many samples are nearly isotropic. These physical property data are separated into depth plots for (1) mudstone, (2) siltstone (3) sandstone, (4) marlstone, and (5) limestone. The mudstone's porosity and wet-bulk density curves versus depth are slightly higher and lower, respectively, than similar porosity and wet-bulk density curves summarized in Hamilton (1976). These differences could be some combination of (1) differences in laboratory methods; (2) age, lithologic, and cementation differences; or (3) overconsolidation created by a geological sequence which has been eroded away. If the average in situ vertical velocities calculated by Boyce (1980b) for Hole 416A are correct, then the 1.43-s (round-trip) reflector (blue) discussed by Lancelot and Winterer (1980) and Lancelot, Winterer et al. (1980b), would correlate to about 1500 m in Hole 416A, and not below 1624 m as suggested by Lancelot and Winterer. There appears to be a significant change in the acoustic character at or around that depth (1500 m) to a more lithified, calcareous, and cemented lithology. This does not prove Lancelot and Winterer (1980) and Lancelot, Winterer et al. (1980b) to be incorrect, but only suggests another possible interpretation.

Description: During an IPOD site survey at the mouth of the Gulf of California, an axial valley about 50 km long and 600 meters deep was found on the East Pacific Rise (EPR) south of the Tamayo Fracture Zone. Magnetic anomalies along the axis of the rise change character from the axial valley to normal sections of the EPR, and off-axis anomalies tend to meander slightly with age, probably indicating that the axial injection zone wanders slightly with time. Along the Baja California margin the magnetic lineations cut across the bathymetric expression of the margin, suggesting that the original rifting of Baja from the mainland occurred along a roughly linear zone. A decrease of heat flow and an increase in sediment thickness and water depth with age from 0 to 3.5 m.y. are consistent with concepts of plate tectonics. Seismic refraction data across and adjacent to the axis of spreading suggest the presence of low-velocity material under the axis, possibly the result of a magma chamber, and a crust which thickens rapidly away from the axis.

Description: Copper porphyrins have been recognized as natural constituents of marine sediments only within the past 5 years (Palmer and Baker, 1978, Science201, 49–51). In that report it was suggested that these pigments may derive from and be markers for oxidized terrestrial organic matter redeposited in the marine environment. In the present study we describe the distribution of copper porphyrins in sediments from several north Pacific and Gulf of California DSDP/IPQD sites (Legs 56,63,64). These allochthonous pigments have now been found to be accompanied by identical arrays of highly dealkylated nickel etioporphyrins. Evaluation of data from this and past studies clearly reveals that there is a strong carbon-number distribution similarity betweeen coincident Cu and Ni etioporphyrins. This homology match is taken as reflecting a common source for the tetrapyrrole ligands of this population of Cu and Ni chelates. Predepositional generation of these highly dealkylated etioporphyrins is concluded from the occurrence of these pigments in sediments continuing essentially all stages of in situ chlorophyll diagenesis (cf. Baker and Louda, 1983). That is, their presence is not regulated by the in situ diagenetic continuum. Thus, the highly dealkylated Cu and Ni etioporphyrins represent an 'allochthonous' background over which 'autochthonous' (viz. marine produced) chlorophyll derivatives are deposited and are undergoing in situ diagenesis.

Description: Results of a clinoptilolite study of Jurassic and Lower Cretaceous sediments from the North Atlantic recovered in DSDP holes are under discussion in the paper.

Description: The monograph has been written on the base of data obtained from samples and materials collected during the 19-th cruise of RV ''Akademik Vernadsky'' to the Northern and Equatorial Indian Ocean. Geological features of the region (stratigraphy, tectonic structure, lithology, distribution of ore-forming components in bottom sediments, petrography of igneous rocks, etc.) are under consideration. Regularities of trace element concentration in Fe-Mn nodules, nodule distribution in bottom sediments, and engineering-geological properties of sediments within the nodule fields have been studied. Much attention is paid to ocean crust rocks. The wide range of ore mineralization (magnetite, chromite, chalcopyrite, pyrite, pentlandite, and other minerals) has been ascertained.

Description: Shear-wave and compressional-wave velocities of 26 basalt samples collected at Site 504 during Deep Sea Drilling Project Legs 69 and 70 were measured at elevated confining pressures. The young basalts have higher velocities than average DSDP basalts, because of their lack of alteration. Measurements of sample porosity are combined with laboratory and in situ velocity measurements to yield estimates of total crustal porosity: 13% at the top of Layer 2, and very low porosity below a depth of 2.0 km.