ALBERT

Beschreibung: Analysis of individual laminae in Recent sediments from the slopes of the Guaymas Basin indicates an increased abundance of the larger sizes (〉60 µm) of Coscinodiscus nodulifer when upwelling conditions persist over the depositional site and an increase of the smaller sizes (〈60 µm) when nonupwelling conditions exist. The size distributions of C. nodulifer in 10-cm composite samples from Hole 480 show a greater abundance of the large sizes (〉60 µm) associated with well-laminated sections and more of the smaller sizes (〈60 µm) in samples from the homogeneous sections. We have tentatively correlated the pronounced homogeneous zones with late Pleistocene glacial periods. These results indicate a persistence of nonupwelling conditions over Hole 480 during glacial periods (homogeneous zones) and a predominance of upwelling conditions during interglacial periods (laminated zones). Other evidence from diatom and silicoflagellate floral analysis seems to support these preliminary conclusions.

Beschreibung: In the present paper, the ecology and feeding habits of euphausiids are described. The samples were taken at the time of the NE-monsoon (1964/65) by R. V. "Meteor" in the Arabian Sea and adjacent waters. 24 species were determined. According to distribution of the species, the following marine areas can be distinguished: Arabian Sea: 24 species, dominant are Euphausia diomedeae, E. tenera, E. distinguenda, Stylocheiron carinatum. Gulf of Aden: 10 species, dominant are Euphausia diomedeae, E. distinguenda. Red Sea: 6 species, dominant are Euphausia diomedeae, E. distinguenda. Gulf of Oman : 5 Species, dominant are Euphausia distinguenda, Pseudeupbaufia latifrons. Persian Gulf: 1 species - Pseudeuphausia latifrons. The total number of euphausiids indicate the biomass of this group. High densities of euphausiids (200-299 and 〉 300 individuals/100 m**3) occur in the innermost part of the Gulf cf Aden, in the area south of the equator near the African east coast, near Karachi (Indian west coast) and in the Persian Gulf. Comparison with data relating to production biology confirms that these are eutrophic zones which coincide with areas in which upwelling occurs at the time of the NE-monsoon. The central part of the Arabian Sea differs from adjacent waters by virtue of less dense euphausiid populations (〉 199 individuals/100 m**3). Measurements relating to production biology demonstrate a relatively low concentration of primary food sources. Food material was ascertained by analysis of stomach content. The following omnivorous species were examined: Euphausia diomedeae, E. distinguenda, E. tenera, Pseudeuphausia latifrons and Thysanopoda tricuspidata. Apart from crustacean remains large numbers of Foraminifera, Radiolaria, tintinnids, dinoflagellates were found in the stomachs. Quantitatively crustaceans form the most important item in the diet. Food selection on the basis of size and form appears to be restricted to certain genera of tintinnids. The genera Stylocheiron and Nematoscelis are predators. Only crustacean remains were found in the stomachs of Stylocheiron abbreviatum, whereas Radiolaria, Foraminifera and tintinnids occurred to some extent in Nematasceli sp. Different euphausiids in the food chain in the Arabian Sea. In omnivorous species the position is variable, since they not only feed by filtering autotrophic and heterotrophic Protista, but also by predation on zooplankton. Carnivorous species without filtering apparatus feed exclusively on zooplankton of the size of copepods. Only these species are well established as occupying a higher position in the food chain. The parasitic protozoan Tbalassomyces fagei was found on Euphausia diomedeae, E. fenera, E. distinguenda and E. sanzoi.

Beschreibung: 15 samples obtained with Beyer's epibenthic closing net were studied quantitatively. The numbers of epi- and endobenthic animals were found to be correlated with the volume of sediment in the samples. Among the planktonic components, calanoid copepodes were strongly predominant. In the samples obtained on the Great Meteor Seamount, very much larger numbers of these animals were caught in the daytime than at night. Possible explanations for this difference are suggested.

Beschreibung: Analyses of stable isotopes of monospecific planktonic foraminifers (G. quadrilobatus group) and monogeneric benthic foraminifers (Cibicidoides spp.) from late Neogene Atlantic Site 502 and Pacific Site 503 were conducted in order to determine the paleoceanographic changes resulting from the late Neogene uplift of the Panama Isthmus and from climatic cooling. In general, results at each site are similar to those from previous studies for the late Miocene and late Pliocene time interval, documenting the late Miocene (6 Ma) shift in carbon isotopes and the inferred growth of permanent Northern Hemisphere continental ice sheets beginning about 3.2 Ma. Comparison of Atlantic-Pacific planktonic-benthic isotope data for four stratigraphic intervals (~6-8, ~5-6, ~3-5, and ~2-3 Ma) suggests that increasing isolation of Atlantic and Pacific low-latitude waters may be related to the emergence of the Panama Isthmus. The contrast between Atlantic and Pacific benthic foraminiferal d13C increased in two steps from 0.60 per mil to 1 per mil (the modern contrast) at about 6 Ma and 3 Ma. The first increase (0.15 per mil) may represent the end of previously limited deep-water communication between the Atlantic and Pacific at the present location of Panama. The second increase (0.25 per mil) may be due to increased production of North Atlantic Deep Water. This probably reflects the development of modern deep-sea circulation. The d18O of planktonic foraminifers begins to increase in Atlantic Site 502 at 4.2 Ma and may reflect the increasing salinity of the North Atlantic Ocean arising from diminishing surface-water exchange across Panama. This increase is clearly shown by contrasting the d18O of Atlantic and Pacific planktonic foraminifers, as well as the d18O of planktonic and benthic foraminifers at Site 502. This inferred increase in surface-water salinity begins at the time of increasing provinciality of Atlantic and Pacific planktonic foraminifers.

Beschreibung: Heavy and light minerals were examined in 29 samples from Sites 494, 498, 499, 500, and 495 on the Deep Sea Drilling Project Leg 67 Middle America Trench transect; these sites represent lower slope, trench, and oceanic crust environments off Guatemala. All samples are Quaternary except those from Hole 494A (Pliocene) and Hole 498A (Miocene). Heavy-mineral assemblages of the Quaternary sediments are characterized by an immature pyroxene-amphibole suite with small quantities of olivine and epidote. The Miocene sediments yielded an assemblage dominated by epidote and pyroxene but lacking olivine; the absence of olivine is attributed to selective removal of the most unstable components by intrastratal solution. Light-mineral assemblages of all samples are predominantly characterized by volcanic glass and plagioclase feldspar. The feldspar compositions are compatible with andesitic source rocks and frequently exhibit oscillatory zoning. The heavy- and light-mineral associations of these sediments suggest a proximal volcanic source, most probably the Neogene highland volcanic province of Guatemala. Sand-sized components from Site 495 are mainly biogenic skeletons and volcanic glass and, in one instance (Section 495-5-3), euhedral crystals of gypsum.

Beschreibung: A study was made of mineral composition of sand- and silt-sized fractions of recent clastic (riftogenic) sediments and solidified deposits collected from the bottom of the Romanche Trench during the first voyage of R/V Akademik Kurchatov. Similarity between mineral compositions of sediments and bedrocks (ultrabasites, gabbroids, diabases) was established. This similarity is a basis for considering the mineral complex of the deposits that have been derived from the bedrocks of the trench slopes, and have formed due to their submarine denudation accompanied by tectonic crushing. The same mineral composition was found in pieces of older consolidated deposits; this suggests that conditions of sedimentation similar to those at recent times have existed for a long time in the Romanche Trench.

Beschreibung: Mineralogical and oxygen isotopic analyses of samples from Deep Sea Drilling Project Sites 477, 481, and 477 in the Guaymas Basin indicate the existence of two distinct hydrothermal systems. In the first, at Sites 481 and 478, hot dolerite sills intruded into highly porous hemipelagic siliceous mudstones that were moderately rich in organic matter, thermally altered the adjacent sediments, and expelled hydrothermal pore fluids. The second, at Site 477 and active at present, is most probably caused by a recent igneous intrusion forming a magma chamber at shallow depth. In the first hydrothermal system, the main thermal reactions above and below the sills are dissolution of opal-A and formation of quartz, either directly or through opal-CT; formation of smectite; formation of analcime only above the sills; dissolution and recrystallization of calcite and occasional formation of dolomite or protodolomite. The d18O values of the hydrothermally altered sediments range from 9.9 to 12.2 per mil (SMOW). The d18O values of recrystallized calcites above the first sill complex, Site 481, indicate temperatures of 140° to 170°C. No fluid recharge is required in this system. The thickness of the sill complexes and the sequence and depth of intrusion into the sediment column determine the thickness of the alteration zones, which ranges from 2 or 3 to approximately 50 meters. Generally, the hydrothermally altered zone is thicker above than below the sill. In the second type, the sediments are extensively recrystallized. The characteristic greenschist-facies mineral assemblage of quartz-albite-chlorite-epidote predominates. Considerable amounts of pyrite, pyrrhotite, and sphene are also present. The lowest d18O value of the greenschist facies rocks is 6.6 per mil, and the highest d18O value of the associated pore fluids is +1.38 per mil (SMOW). The paragenesis and the oxygen isotopes of individual phases indicate alteration temperatures of 300 ± 50°C. On the basis of the oxygen isotopes of the solids and associated fluids, it is concluded that recharge of fluids is required. The water/rock ratio in wt.% is moderate, approximately 2/1 to 3/1 - higher than the calculated water/rock ratio of the hydrothermal system at the East Pacific Rise, 21 °N.

Beschreibung: Nontronite, the main metalliferous phase of the Galapagos mounds, occurs at a subsurface depth of ~2–20 m; Mn-oxide material is limited to the upper 2 m of these mounds. The nontronite forms intervals of up to a few metres thickness, consisting essentially of 100% nontronite granules, which alternate with intervals of normal pelagic sediment. The metalliferous phases represent essentially authigenic precipitates, apparently formed in the presence of upwelling basement-derived hydrothermal solutions which dissolved pre-existent pelagic sediment. Electron microprobe analyses of nontronite granules from different core samples indicate that: (1) there is little difference in major-element composition between nontronitic material from varying locations within the mounds; and (2) adjacent granules from a given sample have very similar compositions and are internally homogeneous. This indicates that the granules are composed of a single mineral of essentially constant composition, consistent with relatively uniform conditions of solution Eh and composition during nontronite formation. The Pb-isotopic composition of the nontronite and Mn-oxide sediments indicates that they were formed from solutions which contained variable proportions of basaltic Pb, introduced into pore waters by basement-derived solutions, and of normal-seawater Pb. However, the Sr-isotopic composition of these sediments is essentially indistinguishable from the value for modern seawater. On the basis of 18O/16O ratios, formation temperatures of ~20–30°C have been estimated for the nontronites. By comparison, temperatures of up to 11.5°C at 9 m depth have been directly measured within the mounds and heat flow data suggest present basement-sediment interface temperatures of 15–25°C.

Beschreibung: The usefulness of cosmogenic beryllium-10 (half life = 2.5 Ma) for studying the rates of accumulation of ferromanganese nodules is reported based on its measured depth distribution in the top 20 mm of these deposits. Accumulation rates have been obtained in the range of 1 to 4 mm/Ma, which are in good agreement with rates determined using the 230Th method on the same nodules. The use of 10Be offers promise in extending the dating to the outer few cm of the nodules. This contrasts with conventional methods using 230Th and 231Pa isotopes which, due to their comparatively short half lives, are limited to a few mm at the surface of the nodules. Detailed studies of 10Be in the manganese deposits coupled with other trace element analyses should prove valuable in understanding the processes of formation of these deposits and the chronology of events recorded by them.

Beschreibung: Nodules occur in the siliceous calcareous ooze and siliceous marl at Site 503 in the eastern equatorial Pacific. They are present below a depth of about 11 meters throughout the green-colored reduced part of the section down to 228 meters, although they are most abundant between 30 and 85 meters. They are cylindrical or barrel-shaped, up to 70 mm long, and usually have an axial channel through them or are hollow. They appear to have formed around and/or within burrows. XRD studies and microprobe analyses show that they are homogeneous and consist of calcian rhododrosite and minor calcite; Mn is present to the extent of about 30%. Isotopic analyses of the carbonate give carbon values which range from -1.2 per mil to -3.8 per mil, and oxygen isotope compositions vary from +4.0 per mil to +6.0 per mil. These values are different from those for marine-derived carbonates as exemplified by the soft sediment filling of a burrow: d13C, -0.26 per mil; d18O, +1.05 per mil. The carbon isotope data indicate that carbonate derived (possibly indirectly) from seawater was mixed with some produced by organic diagenesis to form the nodules. The d18O values suggest that although they formed near the sediment surface, some modification or the introduction of additional diagenetic carbonate occurred during burial.

Beschreibung: Ferromanganese concretions from Grand Lake and Ship Harbour Lake in Nova Scotia and Mosque Lake in Ontario are most common in water 0.5 to 2 m deep. X-ray diffraction studies show the ferromanganese portions of the concretions to he amorphous. Petrographic and electron probe studies of the ferromanganese material reveal chemical banding of iron and manganese. Bulk chemical analyses indicate that the Fe:Mn ratios of concretions from different sites within a single lake are similar, whereas concretions from different lakes have characteristic Fe:Mn ratios. Trace element concs are different in different lakes and are generally several orders of magnitude less than those of oceanic nodules.

Beschreibung: Samples of ferromanganese nodules from several localities in Lake Michigan have been analyzed for their minor element content utilizing neutron activation techniques. The thorium and uranium levels in Lake Michigan nodules exhibit marked dissimilarities with marine nodules. The radium content of these freshwater nodules is substantially higher than the reported marine values. The concentrations of barium in the Lake Michigan nodules appear to be abnormally high. Although barium could be present as minute segregations of the mineral barite, patterns obtained using the electron microprobe suggest it is evently dispersed throughout the nodules. The average arsenic content of these freshwater nodules is at least twice as great as that reported for highly oxidized marine sediments. If all this arsenic is dissolved and released into Green Bay as a result of changing environmental conditions (eutrophication), the concentration in the water of Green Bay would be several times the maximum permissible level for drinking water.

Beschreibung: The cores and dredges described in this report were taken on Cruise 128 of the R.R.S. "Discovery" in May 1982 by the National Institute of Oceanography, Wormley, United Kingdom. A total of 12 cores were recovered and are available through the British Oceanographic Data Centre for sampling and study.

Beschreibung: The cores described in this report were taken on the SEVENTOW Expedition in February-September 1970 by the Scripps Institution of Oceanography from the R/V Thomas Washington. A total of 193 cores and dredges were recovered and are available at Scripps for sampling and study.

Beschreibung: The Atlantic Advisory Panel proposed that Site 8 should be drilled on the rise between the Hatteras and Sohm Abyssal Plains (lat 35° 2l'N., long 67° 3l'W.) This location was considered to offer the best opportunity for realizing two primary objectives. The first of these objectives was to sample and date the oldest available rock in a region adjacent to the North American continent and as far as possible from the Mid-Atlantic Ridge. The second objective relates to the potential paleobiological and paleoecological information that could be derived from the sedimentary column in this general area.

Beschreibung: Site 12 of this report formerly was designated 14 by the Atlantic Advisory Panel. It was drilled in the Cape Verde Basin (latitude 19° 42'N, longitude 26° 01'W), which is underlain by 2000 to 2100 feet (0.9 to 1.1 seconds reflection time) of sediment. The bottom topography of the basin is fairly smooth but not to the degree of an abyssal plain. Site 12 was selected to provide material for paleontological investigations.

Beschreibung: The preliminary planning and approach to site 13 were taken from the JOIDES Atlantic Advisory Panel Report and from a previous detailed survey of the site by R/V Vema of the Lamont Geological Observatory. Several CSP profiles crossing the selected site in various directions show an uplifted portion of the sea floor roughly circular in shape of about 10 kilometers in diameter. In contrast to the smooth bottom of the surrounding abyssal plain, the topography of the small rise selected for the site has a small-scale roughness of amplitude of 40 to 80 meters. The work reported here is a biostratigraphic summary of available samples. Only the most important and biostratigraphically significant components of the faunas have been noted. No attempt has been made to give an exhaustive faunal analysis of the samples seen.

Beschreibung: The Atlantic Advisory Panel proposed that Site 9 should be drilled on the northeastern flank of the Bermuda Rise (lat. 32° 37' N., long. 59° 10' W.), which is about 100 miles west of the Sohm Abyssal Plain. The bottom of this region consists of low linear ridges that are roughly parallel and oriented in a northwest-southeasterly direction. Scattered seamounts, some of which have peaks 2000 fathoms (3660 meters) below sea level, arise from the otherwise featureless sea floor between the ridges. The primary purpose in drilling Site 9 was to examine a sedimentary column where seismic reflectors were largely absent and to determine the age of sediments overlying acoustical basement in the examination of sea floor spreading.

Beschreibung: Prior to arrival on this site, the only survey data available was from the Vema-20 crossing of the area. The recommended site location was over a relatively smooth valley in the bottom topography at about 4750 meters (15,580 feet) depth (uncorrected), about 10 kilometers wide E-W between peaks (or ridges) on either side. Sediment thickness was unknown. The center of the valley is near the peak of a wide (40 to 50 kilometers) positive magnetic anomaly, identified as Magnetic Anomaly 30 in the hypothesized geomagnetic time scale with an age of 72 million years.

Beschreibung: The drilling objectives at this site were to complete the cored section begun at Site 23 in accordance with the recommendations of the JOIDES Atlantic Advisory Panel, presented in the Site 23 report. The location coincides with a position on the southeastern side of the elevated portion of basement in this area.

Beschreibung: At the Leg 4 pre-cruise meeting in Miami, Florida, in January 1969, the Ridge site was proposed as an additional site to be investigated, if possible. Since the water depth and sediment thickness at this site were both minimal (2000 meters and less than 100 meters, respectively) and the location was not far from the track between initially planned sites, the shipboard party decided, upon completion of work at Site 24, to make a 24-hour drilling effort on the North Brazilian Ridge. The drilling objectives at this location were to sample and date the sediments atop the Ridge crest and to determine the nature, age and origin of the consolidated material beneath the thin mantle of sediment.

Beschreibung: The northern margin of the Demerara Abyssal Plain is bordered by a low ESE-WNW trending rise known as the Barracuda Ridge. North of South America, the eastern margin of the Demerara Abyssal Plain is formed by the Barbados Ridge. An extensive sedimentary section of the Barbados Ridge is exposed on the island of Barbados and consists of a series of radiolarian to planktonic foraminiferal and calcareous nannofossil biogenic sediments interlayered with ash beds. To determine the nature of the sediments and "basement," Site 27 was selected on the northern margin of the Demerara Abyssal Plain, south of the Barracuda Ridge.

Beschreibung: The southern Caribbean basins are thought to be part of a relatively old and geologically stable crustal plate. Although surrounded by belts of high earthquake activity, the central Caribbean is seismically quiet. The region also constitutes a quiet magnetic zone and appears to have resisted all of the surrounding forces related to ocean floor spreading. In addition to providing considerable information on the general geologic history of the Caribbean region, paleontologic studies on cores at Site 29 were expected to provide valuable data on phylogenetic trends within the planktonic foraminifera and calcareous nannoplankton, furnishing more accurate criteria for intercontinental stratigraphic correlation. The work reported here is a biostratigraphic summary of available samples. only the most important and biostratigraphically significant components of the faunas have been noted. No attempt has been made to give an exhaustive faunal analysis of the samples seen.

Beschreibung: Site 26 was selected on the crest of the Mid-Atlantic Ridge between 15°N and 5°S is offset to the east nearly 4000 kilometers through a series of fracture zones. One of the most prominent of these is the Vema Fracture Zone, a narrow east-west trending trough which cuts through the Mid-Atlantic Ridge at latitude 11°N.

Beschreibung: Site 32 was proposed by the Pacific Advisory Panel at a location over a strong positive magnetic anomaly (Number 13 on the Pittman-Heirtzler scale, 38 million years) where samples of the basement and the basal sediment would be of value in testing hypotheses for origin of the linear magnetic anomalies from this part of the Pacific. Comparison of this site, south of the Pioneer Fracture Zone, with later sites north of the Fracture Zone would be the basis for evaluating the discontinuity formed by the Pioneer.

Beschreibung: The proposed location of Site 33 was over north-south Magnetic Anomaly 10 (Pittman-Heirtzler, 32 million years) in order (a) to provide a basis for comparison of the age of the basal sediments with the age based on the magnetic anomaly, (b) to provide a basis for evaluation of relative movement along the Pioneer and Mendocino Fracture Zones, and (c) by being paired with Site 34, to provide comparison of basement materials for adjacent positive and negative magnetic anomalies.

Beschreibung: Site 34 had been located by the JOIDES Pacific Advisory Panel to be over a negative magnetic anomaly (31 million years B.P.) immediately to the east of Anomaly 10 (Site 33). The primary objective was to obtain samples of basement and basal sediment to provide comparison between adjacent positive and negative magnetic anomalies. A second objective was to obtain samples which would permit an analysis of the variability in sediment over relatively short distances (about 10 miles). Although basement had not been reached at Site 33 because of the unexpected chert, the use of a massive diamond bit at Site 34 permitted coring through the chert to basement at 383 meters below the sea floor. Even though the near basement sections of the paired sites (33 and 34) could not be compared, comparison would be possible above the chert layer.

Beschreibung: The JOIDES Pacific Advisory Panel proposed Site 37 to meet two principal objectives: to determine the significance of the magnetic anomaly pattern, and the longitudinal profile of the sediment sequence in the eastern Pacific. Site 37 was to be located on the same magnetic anomaly as was Site 33 (#10, 32 million years age), for comparison across the intervening Mendocino Fracture Zone. As basement had not been reached at Site 33, this objective could not be met specifically. However, sediment comparison across the fracture zone was possible.

Beschreibung: The nonfossiliferous nature of most of the thin sediment sequence at Site 37 had provided little biostratigraphic information for the northern end of the proposed section of sites along 140°W longitude. In an attempt to provide a biostratigraphically more meaningful hole as the high latitude terminus of the meridional section, an additional site (Site 38) was drilled between the Mendocino and Pioneer Fracture Zones.

Beschreibung: Site 39 was located in the region between the Pioneer and Murray Fracture Zones, with the objective of recovering a continuous sediment core for paleontologic and stratigraphic study of the longitudinal variations in sediment components in the eastern Pacific. This site was selected, together with the adjacent ones in the north-south line along 140°W, to provide information on the geologic history of the North Pacific gyral, insofar as this might be recorded in the sediments.

Beschreibung: Site 41 marks the transition from the North Pacific gyral to the Equatorial Current System. The JOIDES Pacific Advisory Panel selected a site at this latitude along the longitudinal profile of 140°W in order to obtain information on the history of migrations of these current systems.

Beschreibung: Site 40 was located by the JOIDES Pacific Advisory Panel in the region between the Molokai and Clarion Fracture Zones with the objective of recovering a continuous sediment core for the paleontologic and biostratigraphic study of the variation in sediment components at the transition between the North Pacific gyral and the Equatorial Current System.

Beschreibung: Site 42 is one of the series of sites selected by the Pacific Advisory Panel along the 140th meridian to sample the longitudinal variation in sediment composition in the eastern Pacific. The site is located in an area of abyssal hills between the Clarion and Clipperton Fracture Zones, and is at the northern margin of the thick development of acoustically transparent sediment extending along the equator.

Beschreibung: Deep-sea echinoderms of the Tongue of the Ocean, Bahama Islands, have been studied, using trawled collections made by the University of Miami together with observations from the deep submersible Alvin. Transect runs in the submersible permitted studies of population densities and behaviour of approximately 38 species of larger invertebrates, of which 27 were echinoderms. Several echinoderm species show a patchy distribution pattern which is apparently not related to available food resources. Some species are exclusively herbivores, feeding on fragments of turtle grass, Thalassia testudinata and sargassum weed, Sargassum spp. Feeding habits of some Tongue of the Ocean echinoderms are compared with those of the same species from further north, where supplies of plant material are not nearly so abundant.

Beschreibung: The data presented in this report is the result of investigations carried out by a number of laboratories on a suite of rocks dredged from the Mid - Atlantic Ridge at 45°N by F. Aura en to and K. S. Manchester during the three Bedford Institute cruises BI 19-66 Hudson, BI 22-68 Hudson, and BI 23-68 Theta.

Beschreibung: Scientists from the Woods Hole Oceanographic Institution, the U.S. Navy, the State University of New York at Albany, Wesleyan University, Nine dives in the research submersible ?Alvin? were made into Great Abaco Submarine Canyon to depths ranging from 1850 to 3666 m. Our observations indicate that the walls of this canyon are distinctly terraced, consisting of nearly vertical to overhanging rock cliffs and intervening, less steep sediment-covered slopes. The wall rock consists mostly of massive, shallow-water limestones and dolostones of Cretaceous age, coated on exposed surfaces with manganese oxides. These rocks are heavily jointed/fractured and thus very blocky to angular in appearance, with sponges and other sessile organisms commonly attached. Talus slopes and sedimentary breccia deposits containing angular boulders are present at the base of these steep escarpments. Short-term bottom current measurements in the axis of the eastern part of the canyon indicate that currents are relatively weak, reaching velocities of only 10 cm/sec. This relatively placid setting is further corroborated by the abundance of turtle grass (Thalassia) found along the canyon axis. However, abundant subdued, symmetrical ripple marks and large scour depressions at the base of boulders, indicate that high-energy events sporadically impact the canyon axis. Contemporary erosional activity along the axis of the western (headward) part of the canyon appears to be more significant, as evidenced by asymmetrical ripple marks, sand waves and bioerosion. Great Abaco Canyon has evolved with time via a variety of processes, including: (1) faulting: (2) subsidence; (3) defacement; and (4) erosional down-cutting. The location, orientation and initiation of this canyon appear to be structurally controlled by the Great Abaco Fracture Zone during pre-Santonian time. Regional subsidence during the Mesozoic allowed the walls of Great Abaco Canyon to build vertically by accretion of shallow-water limestones, whereas joint-controlled defacement has widened the canyon while maintaining steep walls. Erosional down-cutting in the canyon axis by carbonate sediment gravity flows also appears to have been important episodically, particularly during the Miocene and Pleistocene.

Beschreibung: Two consecutive drilling legs (Legs 59 and 60) were assigned to drill an east-west transect of sites along latitude 18°N, from the Mariana Basin of the Pacific Ocean to the oldest inactive island arcs and back-arc spreading basins of the Philippine Sea. The western (older, inactive) half of this transect (Philippine Sea, Palau-Kyushu Ridge, Parece Vela Basin, and the West Mariana Ridge-Sites 447-451) was drilled during Leg 59. The objective of Leg 60 was to sample the tectonically active eastern portion of the transect in a closely spaced series of holes across the presently opening back-arc basin (Mariana Trough, Site Survey Target SP-4: Sites 453-456), the Mariana arc itself (Site Survey Target SP-3b: Site 457), the Mariana fore-arc region (Site Survey Target SP-3, Sites 458 and 459), and deep within the Mariana Trench (Site Survey Target SP-2: Sites 460 and 461). In addition, one site (Site Survey Target SP-1: Site 452) was drilled on the Pacific plate seaward of the trench to obtain a reference section of sediments and oceanic crust being delivered to the trench.

Beschreibung: The origin and evolution of passive continental margins are of great scientific interest and economic importance. During DSDP Leg 64 the Glomar Challenger drilled at eight sites (474-481) in the Gulf of California region. The Gulf of California presented a singular example of tectonics and sedimentation in a very young ocean, being formed by translation and oblique rifting. The sedimentation of the region is hemipelagic, rapid, and largely dominated by siliceous microfossils.Sites 474, 475, and 476 form a transect from oceanic crust to continental crust at the southern tip of Baja California in order to define passive-margin subsidence during the early post-rifting phase. Sites 477, 478, and 481 investigate of the nature of young ocean crust in the Guaymas Basin, where high accumulation rates are common and variable high heat flow indicates active rifting and hydrothermal activity. Sites 479 and 480, are situated on the Guaymas Basin Slope above the proto-Gulf sequences. Interest focused on the paleoceanography of laminated, homogeneous diatom-rich, anoxic sediments within the zone of low oxygen.

Beschreibung: Leg 66 was part of two broader investigations of subduction complexes and convergent margin geology, one led by the Active Margin Panel (AMP) of the International Phase of Ocean Drilling (IPOD) to drill selected convergent margins to elucidate structure and evolution and the other, led by the University of Texas Marine Science Instituted (UTMSI) Galveston Geophysical Laboratory (GGL) to investigate the tectonics of the Middle America Trench from the Cocos Fracture Zone to the Riviera Fracture Zone. In this context, the specific objective at Site 487 was the coring of pelagic and hemipelagic sediment section and underlying oceanic basement. It is the farthest offshore site off the Cocos Fracture Zone.

Beschreibung: The Oaxaca transect, located off southern Mexico and drilled during Leg 66, sampled a truncated margin and subduction complex. In contrast, the Guatemala transect was selected because accretion was thought to have continued in this area during most of the Tertiary. Site surveys conducted by the University of Texas Marine Science Institute provided multichannel seismic records, among which profile GUA-13 was chosen as the location for Leg 67 drill holes. Selection of this transect arises in part from the fact that it includes a portion of the San José Canyon, thus layers of hemipelagic drape may have been stripped away by erosion, allowing quicker access to deep horizons. By studying the continental margin off Guatemala it was hoped to strengthen the tie between offshore and onshore geology, to describe the stratigraphic sequence from the continental slope to the subducting oceanic plate beneath, to recover in ash layers a record of Central American volcanism.

Beschreibung: The general objectives of this cruise were to use the newly developed HPC to recover two undisturbed, continuous records of the late Neogene and Quaternary, one from the western Caribbean and the other from the eastern equatorial Pacific, and to test the coring capabilities of the HPC. At site 502 in the Caribbean an hemipelagic facies with accumulation rates of about 3 cm/k.y near site 154 were a coarse-grained volcanogenic turbidite sequence had been recovered at a depth equivalent to a strong seismic reflector. Site 503 was located as close as possible to previously rotary-drilled Site 83 in the eastern equatorial Pacific.

Beschreibung: The recovery of hydrothermal sediments at depth beneath the mounds of hydrothermal origin during a brief period of drilling on Deep Sea Drilling Project (DSDP) Leg 54 provided some evidence suggesting that hydrothermal material may be pervasive over a relatively large region inclusive of the mounds but also incorporating adjacent seafloor presently covered by pelagic sediments. As a result of the incomplete recovery of sediments at some sites and the poor recovery of basement rocks during Leg 54, it was suggested that a more carefully planned program be designed to drill a broader range of sites in the Galapagos mounds field. The major objectives of the first part of Leg 70 were to collect data and sediment representative of the hydrothermal mounds and ridges located about 20 km south of the Galapagos spreading axis.

Beschreibung: he three-site Leg 64 Deep Sea Drilling transect at the tip of the Peninsula of Baja California straddled the transition from continental to oceanic crust. The outer site, 474, penetrated mainly mud turbidites and bottomed in "middle" Pliocene oceanic crust about 3 m.y. old. Two sites on the lower continental slope penetrated hemipelagic muddy sediments, a thin section of low-oxygen, phosphoritic, and glauconitic sediments, and a metamorphic cobble conglomerate; one of the sites, 476, bottomed in deeply weathered granite. The oldest marine sediments at this site are early Pliocene, about 4.5 m.y. old. Depth indicators in these holes suggest that all sites were in almost 1000 meters of water by the time oceanic crust was first generated and sea-floor spreading began. Block faulting, subsidence, and deposition of marine sediments on continental crust had preceded the start of sea-floor spreading. Close examination of lineated magnetic anomalies demonstrates that the transition from continental to oceanic crust in this region is diachronous, as early as 4.9 m.y. in some places, but as young as 3.2 m.y. along the line of the transect. We propose a geological history scenario which involves termination of subduction along the western margin of Baja California at 12.5 Ma, a period of transform motion between the Pacific and North American plates along the Tosco Abreojos Transform Fault zone along the west side of Baja California, and a jump of the Pacific-North American plate edge to the alignment of the Gulf at 5.5 Ma. Between 5.5 Ma and about 3.2 Ma, separation of the blocks occurred locally by sea-floor spreading, but elsewhere by "diffuse extension", largely involving listric normal faulting and thinning of the continental crust, accompanied by subsidence and marine inundation. Thus, the plate edge system in the mouth and southern part of the Gulf evolved as early as 5.5 Ma, but the transition from rifting to drifting was diachronous, starting only 3.2 Ma along the line of the transect.

Beschreibung: This report represents the first in a projected series reporting core descriptions and their physical properties, to be made available through routine core handling procedures instituted at the Hawaii Institute of Geophysics in 1968 to keep pace with the capability to take long (120-foot) piston cores from the University of Hawaii's R/V MAHI. The data reported herein cover sediment cores collected during 1967, 1968, and 1969 in the region of the Solomon Islands and the Darvir. Rise, and along the central portion of the Murray Fracture Zone.

Beschreibung: A detailed geophysical and geological survey of the Mariana Trough, an actively extensional back-arc basin, was conducted in 1976 and 1977 to provide data for selection of drilling sites for DSDP Leg 60. These surveys revealed large-scale bathymetric trends, sediment distribution, crustal seismic veolocity structure, and earthquake activity that suggest the basin is opening around an axial spreading center tectonically similar to the slowly spreading Mid-Atlantic Ridge. There are, however, significant differences in the character of the trough, such as poorly defined magnetic anomalies, extreme bathymetric relief, and the frequent occurrence of low-magnitude earthquakes but absence of larger seismic events. Seafloor spreading in the Mariana Trough may be characteristic of the initial opening stages of any oceanic rift system, whether or not it is in a back-arc setting.

Beschreibung: The American Deep Sea Drilling Project (JOIDES) has agreed to drill several holes into the deep sea sediments at sites in the NE Atlantic suggested by UK and French scientists. These sites have been chosen on the basis of data collected over several years in the areas of Rockall, the Bay of Biscay and King's Trough. On Cruise 33 we undertook to make more detailed seismic reflection surveys of three of these sites in order to guide the choice of the exact hole position and to provide supplementary data. The following three sites were surveyed: Site A in the Hatton-Rockall Basin, Site B in Rockall Trough, Site C on the Azores-Biscay Rise. (2) The southeast end of King's Trough (Peake and Freen Deeps) was studied in detail in Cruises 4 and 11 of R. R. S. 'Discovery' in 1965 and 1966. The results of this work (Matthews et al. , 1969) were not conclusive about the origin of King's Trough. The major part of Cruise 33 was concerned, therefore, with obtaining more geological and geophysical data about King's Trough and its relationship to sea floor spreading occurring to the west on the mid-Atlantic Ridge.

Beschreibung: Mineralogical (microprobe) and geochemical (X-ray fluorescence, neutron activation analyses) data are given for 18 samples of volcanic rocks from the Guatemala Trench area (Deep Sea Drilling Project Leg 67). Typical fresh oceanic tholeiites occur in the trench itself (Hole 500) and in its immediate vicinity on the Cocos Plate (Site 495). Several samples (often reworked) of "spilitic" oceanic tholeiites are also described from the Trench: their mineralogy (greenschist facies association - actinolite + plagioclase + chlorite) and geochemistry (alteration, sometimes linked to manganese and zinc mineralization) are shown to result from high-temperature (300°-475°C) hydrothermal sea water-basalt interactions. The samples studied are depleted in light rare-earth elements (LREE), with the exception of the slightly LREE-enriched basalts from Hole 500. The occurrence of such different oceanic tholeiites in the same area is problematic. Volcanic rocks from the Guatemala continental slope (Hole 494A) are described as greenschist facies metabasites (actinolite + epidote + chlorite + plagioclase + calcite + quartz), mineralogically different from the spilites exposed on the Costa Rica coastal range (Nicoya Peninsula). Their primary magmatic affinity is uncertain: clinopyroxene and plagioclase compositions, together with titanium and other hygromagmaphile element contents, support an "active margin" affinity. The LREE-depleted patterns encountered in the present case, however, are not frequently found in orogenic samples but are typical of many oceanic tholeiites.

Beschreibung: Chemical and X-ray analyses were performed on the fifteen manganese nodules collected from the Pacific Ocean floor. The results were discussed compared with the previous data on the manganese nodules. Minerals were found to be todorokite, delta-MnO2 and other silicates, montmorillonite, illite, phillipsite and alpha-Si02. Average composition shows that copper is concentrated on the deep sea nodules more than the shallow ones, and that the todorokite rich nodules contain more copper and nickel than the delta-MnO2 rich ones. The analyses of fresh water iron-manganese precipitates by bacterial activity suggest that biological process is one of the important factors on the genesis of the sedimentary iron-manganese deposits, in¬cluding the manganese nodule.

Beschreibung: Manganese nodules from 36 stations in the Cape Leeuwin field were analyzed for Mn, Fe, Ni, Cu and Co and the results were combined with earlier work to demonstrate quantitative and geographic variations. Nodules in this field are moderately enriched in Ni, moderately depleted in Cu, and contain intermediate values of Co. The sum of Ni + Cu vs. Mn/Fe plots along a hyperbolic regression line derived from nodules of the southeastern Pacific, suggesting that this relationship has general applicability. Regional variations in nodule grade (Ni + Cu + Co) assist in defining pathways of Antarctic Bottom Water between the Southeast Indian Ridge and the Wharton basin.

Beschreibung: The purpose of the expedition was to test new techniques to determine thickness, distribution and quality of mineral deposits on the Blake Plateau with special reference to manganese nodules and manganese-phosphate pavements.

Beschreibung: Sample preparation technique is critical for valid chemical analyses. A main source of error comes from the fact that the great specific surface area of crusts or nodules enhances their tendency to retain or attract hygroscopic moisture. Variable treatment of this moisture can in extreme cases lead to analytical value differences as great as 40-50 %. In order to quantify these influences, samples of ferromanganese oxide-phosphorite pavement from the Blake Plateau have been subjected to various drying techniques before analysis using X-ray fluorescence.

Beschreibung: Bowie Seamount, a submerged volcano situated off the west coast of Canada at 53° 18; N, 135° 39' W, has a relief of 10,000 ft. and comes to within 100 ft. of the ocean surface. It is made up of a series of intersecting ridges which together give the mountain an overall northeast - southwest elongation. It appears to be a combination central and fissure type volcano which has been built up over a system of intersecting fractures in the oceanic crust. Two terraces form the flattened summit of the volcano at approximate depths of 45 and 130 fathoms. These are thought to be the remains of platforms produced by combined wave erosion and shallow-water vulcanism during late Quaternary time when sea level was lower than it is today. The last phase of volcanic activity on the summit occurred after the formation of the upper terrace no more than 18,000 years ago. Samples dredged from the upper half of the volcano include: pillow fragments, fragments of non-pillowed flows, pillow breccias, bombs, tuffs, ash, and unsorted tephra. The rocks are mainly alkali olivine basalts, accompanied by rare andesites which, presumably, were derived by differentiation of the basaltic magma. Feldspathic and gabbroic inclusions, many of which appear to be cumulates, are common in the basalt. Ice-rafted rocks are rare on the summit of Bowie Seampunt but are common on its nearest neighbour - Hodgkins Seamount. A ferro-manganese deposit, apparently over 1 million years old, that exists on the summit of Hodgkins Seamount, suggests that this peak is relatively much older than the summit area of Bowie Seamount. Palagonite appears to form as the initial phase of weathering of glassy basalts in the area of study but the products of more advanced weathering are montraorillonite and zeolites. Rock fragments that have been rounded by chemical weathering are common.

Beschreibung: Manganese-iron oxide concretions are presently forming on Patrick Sill in upper Jervis Inlet. The marine geology of Patrick Sill and the adjoining basins (Queen's Reach and Princess Royal Reach) was studied to define the environment in which the concretions form. The river at the inlet head is the principal source of sediment to the upper basin. The average grain size of surficial bottom sediments within this basin decreases uniformly with distance from the source. Patrick Sill separates the upper from the lower basin. The sediment distribution pattern within the lower basin differs markedly from the upper basin as there is no dominant source of material but rather many localized sources. Abundant shallow marine faunal remains recovered in deep water sediment samples indicate that sediments deposited as deltas off river and stream mouths periodically slump to the basin floors. Geologic and optical turbidity information for the upper basin can best be explained by slumping from the delta at the inlet head with the initiation of turbidity or density currents. Patrick Sill appears to create a downstream barrier to this flow. The mineralogy of the bottom sediments indicates derivation from a granitic terrain. If this is so, the sediments presently being deposited in both basins are reworked glacial materials initially derived by glacial action outside the present watershed. Upper Jervis Inlet is mapped as lying within a roof pendant of pre-batholithic rocks, principally slates. Patrick Sill is thought to be a bedrock feature mantled with Pleistocene glacial material. The accumulation rate of recent sediments on the sill is low especially in the V-notch or medial depression. The manganese-iron oxide concretions are forming within the depression and apparently nowhere else in the study area. Also forming within the depression are crusts of iron oxide and what are tentatively identified as glauconite-montmorillonoid pellets. The concretions are thought to form by precipitation of manganese-iron oxides on pebbles and cobbles lying at the sediment water interface. The oxide materials are mobile in the reducing environment of the underlying clayey-sand sediment but precipitate on contact with the oxygenating environment of the surficial sediments. The iron crusts are thought to be forming on extensive rocky surfaces above the sediment water interface. The overall appearance and evidence of rapid formation of the crusts suggests they formed from a gel in sea water. Reserves of manganese-iron concretions on Patrick Sill were estimated to be 117 metric tons. Other deposits of concretions have recently been found in other inlets and in the Strait of Georgia but, to date, the extent of these has not been determined.

Beschreibung: Ferromanganese deposits, mostly manganese crusts, are common in elevations along the northeastern Brazilian continental margin. Association of the deposits with more or less altered basaltic rock can be observed. On the Pernambuco Plateau and Ceara Guyot, ferromanganese deposits occur associated with phosphatic material and nodules. The mineralogical composition of the ferromanganese deposits indicates a predominance of the manganese oxide phase dMnO2. Low contents of Mn and Cu are characteristic of their chemical composition. Fe and Mn in the deposits probably precipitated from the sea water.

Beschreibung: Manganese nodules from a wide range of marine environments have been analysed for a series of elements by optical spectrography,atomic absorption spectrophotometry and mass spectrometry to assess the influence of the environment of deposition on the trace element assemblage of nodules and a more detailed assessment has been made of the trace element geochemistry of nodules from area 4C on the flanks of the Carlsberg Ridge in the Indian Ocean. The mineralogical characteristics of the nodules are described and a detailed petrographic and Mass spectrometry (A.E.I. MS7) analysis of three selected specimens presented. Finally, a method is developed for the oxygen isotope analysis of manganese nodules and the application to the problems of paleoclimatology discussed. To investigate the correlation of trace element geochemistry of nodules with depth as suggested by Cronan (1967) and Barnes (1967), a detailed comparison of the trace element geochemistry of nodules from shallow water and deep sea environments was undertaken. The results show a fundamental difference in the trace element assemblage of nodules from continental margin environments compared with those from deep sea and seamount environments. The marked enrichment of Mn and consequent depletion of Fe and trade elements in nodules from continental margin environments indicates the influence of diagenetic remobilisation of manganese in reducing environments on the trace element assemblage of manganese nodules. Variations in the mineralogical characteristics of nodules are attributed to variations in the redox conditions at the sediment-water interface and a correlation between nodule mineralogy and trace element geochemistry becomes apparent. The application of these concepts to the assessment of the paleoenvironmental characteristics of deposition of sedimentary manganese ore bodies is discussed. On the Carlsberg Ridge, the distribution of manganese crusts away from the belt of maximum seismicity along the axis of the mid-Ocean Ridge argues strongly against the influence of submarine vulcanism on nodule formation. A consideration of the ocean floor spreading rate indicate5that the thickness of the manganese crusts on the flanks of the Carlsberg Ridge is related to the length of time the nodule has been in contact with seawater. This suggests that, although submarine vulcanicity may have contributed to the overall mass balance of the oceans, manganese nodules form by the direct precipitation of trace elements from sea water. A consideration of the trace element distribution in a series of sediment cores from the flanks of the Carlsberg Ridge indicates that sediment diagenesis plays only a minor role in influencing the trace element distribution in nodules from this environment. Finally, a discussion of the thermodynamics of nodule precipitation is given and the need for a more detailed assessment of the kinetics of uptake of trace elements in nodules stressed.

Beschreibung: The report is divided into three sections: morphology, mineralogy and elemental composition. The nodule morphology section defines what is considered a nodule for the study, and details the external characteristics and internal structure. Nodule mineralogy is discussed in three sections: manganese minerals, iron oxide minerals, and accessory minerals. The major manganese minerals discussed are todorokite, birnessite, and vernadite. The iron oxide minerals are less well known and include feroxyhyte, goethite, and lepidocrocite. Accessory minerals present include quartz, clays, and other silicates and nonsilicates. A discussion on moisture content is also included. The elemental composition section presents data on 74 elements occurring as cations or anions. Summary data, histograms, and interelement correlation coefficients are presented.

Beschreibung: A large deposit of ferromanganese oxide concretions has been found in the northern portion of Lake Ontario. The concretions occur mainly in the form of coatings on sand grains but manganese nodules are present at several localities. Mineralogically, the ferromanganese oxide phases are amorphous, and their Fe and Mn contents are similar to those in concretions from other environments. However, their Ni, Co, and Cu contents are significantly higher than those reported in previously described North American lacustrine ferromanganese concretions, and this may, in part, be a reflection of their probable low rates of accumulation.

Beschreibung: Fossil ferromanganese crusts, nodules and pavements are contained in stratigraphically condensed pelagic limestones from the Middle Jurassic of western Sicily; and a similar association of iron-manganese deposits with condensed pelagic sequences is notable throughout the Tethyan region. The west Sicilian concretions contain goethite, haematite and todokorite as fine-grained phases; their internal structure consists of iron-manganese segregations in a calcite matrix. Electron-microprobe study indicates that the amount of iron and manganese varies considerably in nodules from different localities, notwithstanding the disparity in carbonate content; and the same is true of the minor elements. The most consistently established inter-element relationships are Ni, Ba with Mn, and Ti with Fe - but these associations are by no means invariably developed. For western Sicily, submarine volcanism seems to have been the most immediate source of supply for the formation of the concretions; and this may well have been the case elsewhere in the Alpine- Mediterranean region; however, the Jurassic was a time of widespread sedimentary iron-ore formation in epicontinental northern Europe, and river drainage must have also supplied some manganese to the Tethyan Ocean. These mineral concretions are interpreted as being formed on ancient limestone (non-volcanic) seamounts. The presence of algal stromatolites in many of the condensed sequences suggests formation within the photic zone; and this relatively shallow-water origin may have affected the minor-element composition of the concretions, particularly with reference to copper and vanadium.

Beschreibung: The dredges described in this report were taken during the TR-079 Expedition in March 1970 by the University of Rhode Island from the R/V Trident. A total of 12 grabs were recovered and are available at the University of Rhode Island for sampling and study.

Beschreibung: Isolation and analysis of the eolian component of late Cenozoic pelagic sediments from the North Pacific provides direct information concerning changes in atmospheric circulation. A 50% increase in intensity of both the prevailing westerlies and the tradewinds coincides with increasing pole-to-equator temperature gradients resulting from the onset of northern hemisphere glaciation. At the same time, the mass flux of dust from continents to the North Pacific increased by a factor of 4.5, apparently reflecting significantly increased continental aridity associated with the late Cenozoic glacial ages.