ALBERT

Description: Triassic through Lower Cretaceous deposition along the Moroccan continental margin was controlled by Triassic rifting and subsequent continental drift associated with the formation of the Atlantic Ocean. During Triassic rifting, basement-involved normal faults formed half-grabens which filled with continentally derived shales and sandstones. In northern Moroccan basins, early rifting intensity was mild to moderate. Distant highlands provided only minor clastic input to these subsiding Triassic-Lower Jurassic half-grabens; instead, evaporite sequences developed during the invasion of the proto-oceanic basin by the Tethys Sea. Evaporite precipitation kept pace with basin subsidence. In southern Moroccan basins, rifting intensity was moderate to strong. Thick Upper Trias ic-Lower Jurassic terrigenous clastic successions were deposited into rapidly subsiding half-grabens. Movement along the South Atlas fault zone accommodated the extensional strain between northern and southern Morocco. Postrift or passive-margin sedimentation characterized the Middle Jurassic through Cretaceous rocks along the Moroccan margin. Less restrictive marine conditions prevailed as drifting progressed, resulting in increased carbonate deposition during the remainder of the Jurassic. Middle to Upper Jurassic reefs and carbonate platforms developed both over and landward of the deforming evaporites. With further drifting, the rifted continental margin subsided, "drowning" the Jurassic reefs. With erosional base level lowered and onshore highlands exposed, large amounts of clastic material were shed into the offshore basins. At least two Lower Cretaceous depocenters received clastic sediments in southern Morocco. Growth faulting in the Lower Cretaceous deltaic clastics created the large offsho e deep-water slope anticline. During the Late Cretaceous, pelagic limestones and shales were deposited over Lower Cretaceous deltaic and paralic sediments.

Description: The Teahitia-Mehetia hot spot region located in the southeastern extension of the Society Islands chain, near 18° S–148° W consists of several active volcanoes. The distribution of recent volcanic activity correlates with seismic epicenters, and covers an area of more than 1000 km2. Intermittent volcanic activity has given rise to large (〉1000 m high) and small (〈500 m high) edifices composed of various types of flows. Several recent volcanic events have produced a suite of alkalic rocks ranging from ankaramites, through alkali basalts to trachy-phonolites. The presence of altered MORB-like tholeiites on one small seamount suggests that a different mantle source material was involved in forming some of the crust in this hot spot region.

Description: In a midoceanic region of the northeast Atlantic, patches of freshly deposited phytodetritus were discovered on the sea floor at a 4500 m depth in July/August 1986. The color of phytodetritus was variable and was obviously related to the degree of degradation. Microscopic analyses showed the presence of planktonic organisms from the euphotic zone, e.g., cyanobacteria, small chlorophytes, diatoms, coccolithophorids, silicoflagellates, dinoflagellates, tintinnids, radiolarians, and foraminifers. Additionally, crustacean exuviae and a great number of small fecal pellets, “minipellets,” were found. Although bacteria were abundant in phytodetritus, their number was not as high as in the sediment. Phytodetrital aggregates also contained a considerable number of benthic organisms such as nematodes and special assemblages of benthic foraminifers. Pigment analyses and the high content of particulate organic carbon indicated that the phytodetritus was relatively undegraded. Concentrations of proteins, carbohydrates, chloroplastic pigments, total adenylates, and bacteria were found to be significantly higher in sediment surface samples when phytodetritus was present than in equivalent samples collected at the same stations in early spring prior to phytodetritus deposition. Only the electron transport system activity showed no significant difference between the two sets of samples, which may be caused by physiological stress during sampling (decompression, warming). The chemical data of phytodetritus samples displayed a great variability indicative of the heterogeneous nature of the detrital material. The gut contents of various megafauna (holothurians, asteroids, sipunculids, and actiniarians) included phytodetritus showing that the detrital material is utilized as a food source by a wide range of benthic organisms. Our data suggest that the detrital material is partly rapidly consumed and remineralized at the sediment surface and partly incorporated into the sediment. Incubations of phytodetritus under simulated in situ conditions and determination of the biological oxygen demand under surface water conditions showed that part of its organic matter can be biologically utilized. Based on the measured standing stock of phytodetritus, it is estimated that 0.3–3% of spring primary production sedimented to the deep-sea floor. Modes of aggregate formation in the surface waters, their sedimentation, and distribution on the seabed are discussed.

Description: Back-scattered electron investigations of Argille Scagliose, mudstones from the Barbados forearc sampled during Ocean Drilling Program Leg 110, and the matrix of the Okitsu melange, southwest Japan, indicate a variety of microfabric geometries and deformation mechanisms despite the similarity of their mesoscopic scaly fabrics. In the Okitsu melange, the scaly fabric is the mesoscopic expression of an anastomosing microfabric, whereas the detailed geometry of scaly fabrics is unrelated to the microfabric in the Argille Scagliose and Leg 110 mudstones. Care must be taken in the classification and interpretation of scaly fabrics in light of these data, and future studies should focus on microstructural investigations.

Description: Hydrothermal fluids responsible for the formation of volcanogenic massive sulfides may transport gold in solution as Au(HS) 2 (super -) at low temperatures (〈350 degrees C), near neutral pH, and high concentrations of H 2 S (10 (super -3) -10 (super -2) m). To a lesser extent gold may be transported as AuCl 2 (super -) at higher temperatures (〉 or =350 degrees C), low pH, and elevated salinities (〉 or =1 m NaCl). The documented fluid chemistry of active hydrothermal vents on the modern seafloor confirms that gold transport is mainly due to Au(HS) 2 (super -) , and the calculated solubility of gold as Au(HS) 2 (super -) is highest in low-temperature (150 degrees -250 degrees C) vent fluids at elevated oxygen and sulfur activities. Sulfides which coprecipitate with gold commonly have properties which can be related to the temperature and sulfidation state of the hydrothermal fluids and therefore reflect conditions which were favorable for the transport or deposition of gold as Au(HS) 2 (super -) .A comparison of gold grades with sulfide mineral equilibria and the FeS contents in sphalerite from a variety of deposits indicates that gold enrichment is closely related to the temperature-a (sub S 2 ) conditions in the ore-forming fluids. Sea-floor sulfides range from sulfur-rich, pyrite-marcasite assemblages to relatively sulfur-deficient, pyrrhotite-isocubanite assemblages, with coexisting sphalerite containing 0 to 55 mole percent FeS. Significant gold enrichment occurs exclusively in low-temperature (〈300 degrees C) pyritic sulfides, together with sulfur-rich trace minerals and Fe-poor sphalerite. Bulk gold contents range from 〈0.5 ppm Au in sulfides with sphalerite containing 10 to 55 mole percent FeS up to 6.7 ppm Au in sulfides with sphalerite containing 〈10 mole percent FeS. Fluid inclusions in Fe-poor sphalerite (〈5 mole % FeS) from one gold-rich deposit (avg 4.9 ppm Au) have trapping temperatures of 235 degrees + or - 13 degrees C (Hannington and Scott, 1988). Low-temperature ores with high gold contents are also common in Phanerozoic Zn-Cu-Pb deposits in Japan (Kosaka, Furutobe, Shakanai) and similar deposits in British Columbia (HW mine, Lynx, Seneca). Gold-bearing polymetallic sulfides contain sulfur-rich mineral assemblages (e.g., bornite + pyrite) and recognizable trace mineral equilibria which indicate a high a (sub S 2 ) (e.g., argentite-electrum, tennantite-enargite, covellite-digenite). Zn-Cu-Pb ores formed at 200 degrees to 300 degrees C typically contain Fe-poor sphalerite (〈1 mole % FeS) and gold grades of i to 3 ppm Au, whereas Cu-rich ores formed at 〉300 degrees C contain Ferich sphalerite (1-5 mole % FeS) and gold grades 〈 1 ppm Au. Archean Cu-Zn deposits at Noranda, Quebec, consist mainly ofpyrite-pyrrhotite ores containing 0.5 to 1 ppm Au together with Fe-rich sphalerite (10-12 mole % FeS). However, pyritic ores which occur stratigraphically up-section commonly contain 1 to 3 ppm Au and relatively Fe-poor sphalerite (5 mole % FeS). Different sulfide mineral equilibria and FeS contents in sphalerite are interpreted to reflect the same physical and chemical conditions which influence gold grades and suggest that petrologic indicators of the sulfidation state may be useful guides to gold mineralization in volcanogenic massive sulfides.

Description: Hole 504B is by far the deepest hole yet drilled into the oceanic crust in situ, and it therefore provides the most complete “ground truth” now available to test our models of the structure and evolution of the upper oceanic crust. Cored in the eastern equatorial Pacific Ocean in 5.9-m.y.-old crust that formed at the Costa Rica Rift, hole 504B now extends to a total depth of 1562.3 m below seafloor, penetrating 274.5 m of sediments and 1287.8 m of basalts. The site was located where the rapidly accumulating sediments impede active hydrothermal circulation in the crust. As a result, the conductive heat flow approaches the value of about 200 mW/m² predicted by plate tectonic theory, and the in situ temperature at the total depth of the hole is about 165°C. The igneous section was continuously cored, but recovery was poor, averaging about 20%. The recovered core indicates that this section includes about 575 m of extrusive lavas, underlain by about 200 m of transition into over 500 m of intrusive sheeted dikes; the latter have been sampled in situ only in hole 504B. The igneous section is composed predominantly of magnesium-rich olivine tholeiites with marked depletions in incompatible trace elements. Nearly all of the basalts have been altered to some degree, but the geochemistry of the freshest basalts is remarkably uniform throughout the hole. Successive stages of on-axis and off-axis alteration have produced three depth zones characterized by different assemblages of secondary minerals: (1) the upper 310 m of extrusives, characterized by oxidative “seafloor weathering“; (2) the lower extrusive section, characterized by smectite and pyrite; and (3) the combined transition zone and sheeted dikes, characterized by greenschist-facies minerals. A comprehensive suite of logs and downhole measurements generally indicate that the basalt section can be divided on the basis of lithology, alteration, and porosity into three zones that are analogous to layers 2A, 2B, and 2C described by marine seismologists on the basis of characteristic seismic velocities. Many of the logs and experiments suggest the presence of a 100- to 200-m-thick layer 2A comprising the uppermost, rubbly pillow lavas, which is the only significantly permeable interval in the entire cored section. Layer 2B apparently corresponds to the lower section of extrusive lavas, in which original porosity is partially sealed as a result of alteration. Nearly all of the logs and experiments showed significant changes in in situ physical properties at about 900–1000 m below seafloor, within the transition between extrusives and sheeted dikes, indicating that this lithostratigraphic transition corresponds closely to that between seismic layers 2B and 2C and confirming that layer 2C consists of intrusive sheeted dikes. A vertical seismic profile conducted during leg 111 indicates that the next major transition deeper than the hole now extends—that between the sheeted dikes of seismic layer 2C and the gabbros of seismic layer 3, which has never been sampled in situ—may be within reach of the next drilling expedition to hole 504B. Therefore despite recent drilling problems deep in the hole, current plans now include revisiting hole 504B for further drilling and experiments when the Ocean Drilling Program returns to the eastern Pacific in 1991.

Description: In an attempt to create a scenario for the cause of the glacial to interglacial CO2 change recorded in air trapped in polar ice, we call on an increase in the alkalinity of polar surface waters. In this way we circumvent a major deficiency of the polar nutrient scenarios of Sarmiento and Toggweiler (1984), Siegenthaler and Wenk (1984) and Knox and McElroy (1984). Namely, our scenario does not require a drop in the nutrient content of polar surface waters in conformity with the demonstration by Boyle (1988a, b) that the cadmium content of planktonic foraminifera from polar regions did not decrease from late glacial to Holocene time. The rise in alkalinity required by our model is a natural consequence of the demise, during glacial time, of North Atlantic Deep Water as a major force in ocean circulation and of the nutrient maximum deepening of Boyle (1988b). Rather than being original, our hypothesis builds on the concept basic to the polar nutrient hypotheses, namely that the CO2 partial pressure in polar waters controls that for both the atmosphere and warm surface ocean. It also requires the alkalinity increase in surface waters produced by Boyle's nutrient deepening.

Description: Drilling at ODP Sites 642 and 643 revealed a 250 m-thick section of diatomaceous Pliocene to Miocene sediments on the outer Velring Plateau, eastern Norwegian Sea. These biogenic silica-rich sediments have a significantly lower saturated bulk density than the surrounding sediments, causing a decrease in acoustic impedance, which is seismically expressed as a negative polarity reflection. Variations in sonic velocity, the other key parameter in seismic analysis, is only of secondary importance in creating impedance contrasts in our study. Synthetic seismograms were produced from shipboard physical property measurements corrected for in situ conditions. These synthetic seismograms are in good agreement (:s6 m) with high-resolution air-gun seismic profiles shot during extensive seismic surveys on the Velring Plateau and provide the basis for CQrrelations between the seismic record and the borehole. The ability to unambiguously identify seismic horizons associated with biogenic silica deposits on the Velring Plateau will permit the mapping of Miocene productivity patterns.

Description: In the Antarctic there are large unexploited stocks of cephalopods with high potential commercial value and there are two important fisheries for squid in the cool temperate waters of the Southern Ocean, adjacent to the Antarctic, in the Atlantic and Pacific sectors. Squid fisheries can develop very rapidly, and if this were to happen in the Antarctic before adequate management plans could be established, there would be serious consequences for the squid stocks, and also for the vertebrate predator populations which depend on them. It is especially important to increase our knowledge of the Antarctic cephalopod species, their distribution and role in the food chain, and to understand their life cycles

Description: Loligo forbesi Steenstrup is a commercially and biomedically important species raneing from Scotland to North Africa and from the Azores Islands in the central Atlantic east through the Mediterranean Sea and Red Sea. Eggs were collected from Plymouth. England and from the Azores and the hatchlings were reared to adult size in recirculating seawater systems. Growth data were obtained primarily from mortalities during the course of three culture experiments which lasted 360, 240 and 480 days. Loligo forbesi hatched at a size of 5–9mg (3.0–4.6mm mantle length, ML) and grew to a maximum size of 124g (155 mm ML) in 413 days. In all experiments, growth was exponential in form for at least the first 3 months at rales of 5.8, 5.1 and 3.6% body weight per day (BW/d) at mean temperatures of 14.1, 14.0 and 13.1°C respectively. In one short-term experiment, month-old squids grew at 8.0% BW/d at 17.4°C. Growth beyond 3 months was slower and either logarithmic (as described by the power function) or exponential in form. Growth rates gradually declined to 1–2% BW/d, Analyses of mantle length growth confirmed the wet weight results. There was no evidence of sexual dimorphism in the laboratory populations, which were of small size, and the length-weight (L-W) relationships were found to be similar to those of field populations. Growth rates during the exponential growth phase appeared very sensitive to temperature, with a 1°C difference changing growth rate by 2% BW/d and producing a three-fold difference in weight at 90 days post-hatching. These dramatic effects of temperature on adult size and lifespan in nature are discussed. It is hypothesized that the small size of mature laboratory-reared squids was due to low culture temperatures during the first 3 months.

Description: Sinking and sedimentation rates of a natural phytoplankton community were simultaneously measured during the course of a diatom winterkpring bloom in a 13m3 experimental mesocosm. Sinking rate was determined directly in settling columns and was calculated from sediment trap catches. The 2 methods yielded significantly different results. Whole-community as well as speciesspecific sinking rates varied over time. These variations were related to changes of the environmental conditions. Over a 26d study period, a total of 7.5g cm-' was collected in the sediment traps. Viable phytoplankton cells were the primary component of the sedimented matter while zooplankton fecal pellets contributed on average less than 10 %. Assuming the Redfield atomic ratio for the collected material, the amount of carbon which sedimented during the winterkpring bloom could be predicted from pre-bloom nutrient concentrations. The daily sedimentation rate varied considerably over time and displayed a characterisbc pattern. This pattern is evidently a function of both suspended phytoplankton biomass and the temporal variation in whole-community sinking rate.

Description: During the Anglo-German Antarctic expedition in February 1982 macroplankton was collected in the waters off the Antarctic Peninsula. Macroplankton compos~tions at 36 stations were compared and degrees of similarity submitted to hierarchical cluster analysis. Results demonstrate strong spatial heterogeneity, which could be attributed to the different water masses in this region. These dissimilarities demarcate 4 provinces, each characterized by a distinct macroplankton community: (l) The 'Oceanic Community' comprises the stations influenced by the Westwind Drift; oceanic forms are typical (e.g. the hyperiid amphipod Vibilia antarctica, and the polychaete Vanadis antarctica). (2) The 'Bellingshausen Water Community' is influenced by Bellingshausen Sea water and oceanic specles are scarce; large numbers of Antarctic krill Euphausja superba occur but shallow water forms are also abundant. (3) The 'Nentic Community' consists of stations in the shelf water of the southern Bransfield Strait; it is charactenzed by postlarvae of several fish species, and meroplanktonic larvae of benthic forms. Large krill concentrations, however, are also encountered. (4) A 'Transitional Community' exists in environments where various water masses mingle (e.g. at shelf slopes). This community lacks typical forms.

Description: Phytoplankton production, standing crop, and loss processes (respiration, sedimentation, grazing by zooplankton, and excretion) were measured on a daily basis during the growth, dormancy and decline of a winter-spring diatom bloom in a large-scale (13 m3) marine mesocosm in 1987. Carbonspecific rates of production and biomass change were highly correlated whereas production and loss rates were unrelated over the experimental period when the significant changes in algal biomass characteristic of phytoplankton blooms were occurring. The observed decline in diatom growth rates was caused by nutrient limitation. Daily phytoplankton production rates calculated from the phytoplankton continuity equation were in excellent agreement with rates independently determined using standard 14C techniques. A carbon budget for the winter bloom indicated that 82.4% of the net daytime primary production was accounted for by measured loss processes, 1.3% was present as standing crop at the end of the experiment, and 16.3% was unexplained. Losses via sedimentation (44.8%) and nighttime phytoplankton respiration (24.1%) predominated, while losses due to zooplankton grazing (10.7%) and nighttime phytoplankton excretion (2.8%) were of lesser importance. A model simulating daily phytoplankton biomass was developed to demonstrate the relative importance of the individual loss processes.

Description: A 4-year expendable bathythermograph data set (1984–1987) from the area between southern Brazil and the Antarctic Peninsula provides information on the interannual variability of front locations. Two boundaries of subtropical water at different depths are identified north and south of the Brazil Current-Falkland (Malvinas) Current confluence zone. The northern Subtropical Front is displaced over a large part of the Argentine Basin from one observational period to the other. The shallow southern Subtropical Front appears fixed to the Falkland Escarpment. The Polar Front and Subantarctic Front locations do not vary much, except for one case where a cold core eddy in the Polar Frontal Zone causes a large northward displacement of the Subantarctic Front.

Description: The Azores Current, south of the Azores Archipelago, is part of the subtropical North Atlantic gyre. Using an international hydrographic data set, we analyze mean and seasonal geostrophic transport fields in the upper 800 m of the ocean in order to determine the origin of the Azores Current in the western basin and seasonal changes in the related flow. Geostrophic currents are obtained by using the method applied by Stramma (1984) in the eastern basin. The Azores Current is found to originate in the area of the Southwest Newfoundland Rise (Figure 10). In winter an almost uniform current connects this region of origin with the Azores Current, while a branching into two current bands is observed in summer, with the southern band forming a marked cyclonic loop. Within the upper 800 m, all of the transport in the northern band and about 70% of the transport in the southern band recirculates in the eastern basin. Additionally, expendable bathythermograph data from the Azores Current region indicate an increase of eddy potential energy from winter to summer.

Description: Measurements in the mixing zone of the Elbe estuary were performed during three consecutive tidal cycles with three types of instruments—a moored tripod with velocity and temperature/conductivity/light attenuation sensors, a profiling sonde with similar sensors lowered from an anchored vessel, and instrumented moorings. Acoustic-travel-time sensors were used for velocity measurements. Spectral analysis of 12·8 min pieces of the obtained time series gives results that are consistent with isotropic turbulence for part of the frequency space. Temporal changes of turbulent kinetic energy are correlated with tidal current velocity. A retardation is found between changes in tidal current and turbulent energy. Not all shear stress terms are in similar phase with tidal flow. Mean gradients, Reynolds stress terms, and turbulent salt flux terms are combined to determine eddy viscosity and eddy diffusion coefficients.

Description: To estimate the importance of starvation induced mortality for recruitment of marine fish larvae three distinct methods were applied to determine the nutritional condition of fish larvae in situ. In addition to highly sensitive fluorescence techniques for analysing RNA/DNA ratios and tryptic enzyme activities histological standard methods were used to compare the nutritional status of fish larvae of the genus Vinciguerria (Photichthyidae) caught in two ecologically different areas of the Indian Ocean: In the central Arabian Sea and on the continental shelf of Pakistan. A comparison of the results elaborated by the distinct methods shows a trend towards better nutritional conditions for fish larvae from the offshore region.

Description: Two buoy types have been tested with respect to their drift performance under drogued and undrogued conditions. Additionally, forces acting on the buoys were measured directly. Quadratic drag laws have been confirmed for the drag in water and the combined drag of wind and waves. Stokes drift contributes about one half to the wind factor of 0.023, which is obtained for undrogued buoys in the Atlantic. The forces on a windowshade drogue are given by a linear relation between force and water velocity for speeds exceeding 10 cm/s. They have been extrapolated to speeds of less than 10 cm/s by both a linear and a quadratic relationship. Correlations between drift and wind speed in the Atlantic suggest that the linear law is a better approximation under realistic conditions. According to these measurements in the Atlantic the described buoy-drogue system with a windowshade drogue in 100-m depth is a good current-measuring device. Slippage is negligible for wind speeds of less than 15 m/s and is less than 2 cm/s under gale conditions. Undrogued buoys are strongly affected by wind and cannot be used for the analysis of currents without correction, even under light winds.

Description: ROOTH proposed that the Younger Dryas cold episode, which chilled the North Atlantic region from 11,000 to 10,000 yr BP, was initiated by a diversion of meltwater from the Mississippi drainage to the St Lawrence drainage system. The link between these events is postulated to be a turnoff, during the Younger Dryas cold episode, of the North Atlantic's conveyor-belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the North Atlantic region2. This turnoff is attributed to a reduction in surface-water salinity, and hence also in density, of the waters in the region where North Atlantic Deep Water (NADW) now forms. Here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from Orca Basin core EN32-PC4 which reveal a significant reduction in meltwater flow through the Mississippi River to the Gulf of Mexico from about 11,200 to 10,000 radiocarbon years ago. This finding is consistent with the record for Lake Agassiz which indicates that the meltwater from the southwestern margin of the Laurentide Ice Sheet was diverted to the northern Atlantic Ocean through the St Lawrence valley during the interval from ~11,000 to 10,000 years before present (yr BP).

Description: Radiocarbon ages on handpicked foraminifera from deep-sea cores are revealing that areas of rapid sediment accumulation are in some cases subject to hiatuses, reworking and perhaps secondary calcite deposition. We present here an extreme example of the impacts of such disturbances. The message is that if precise chronologies or meaningful benthic planktic age differences are to be obtained, then it is essential to document the reliability of radiocarbon ages by making both comparisons between coexisting species of planktomc foraminifera and detailed down-core sequences of measurements.

Description: The west Galicia margin (Spain) is a typical passive margin. During the Mesozoic, the continental crust of the margin experienced several episodes of extension. The main stage was during the Berriasian-late Aptian interval (140-114 Ma). The stretching of the lithosphere resulted in (a) the thinning of the continental crust, testified by superficial extensional structures (normal faults, tilted fault blocks) and rapid subsidence, and (b) the emplacement of mantle rocks (peridotite) at the continental rift axis. The crustal thinning and the final emplacement of peridotite onto the seafloor are explained by asthenosphere diapirism succeeded by uniform, normal, simple shear of the thinned continental lithosphere.

Description: Compressional-wave (P-wave) velocities and magnetic susceptibilities were measured on gravity (GGC) and piston cores (PC) and Ocean Drilling Program (ODP) Leg 108 advanced piston cores (APC) from the equatorial Atlantic to test our hypothesis that climatically driven changes in terrigenous and biogenic fluxes, and in carbonate dissolution control the interrelationships between the two signals. In Pleistocene sediments deposited above the calcium compensation depth (CCD) we observed changes in P-wave velocity and magnetic susceptibility that are (1) inversely correlated, and (2) coherent to changes in glacial-interglacial climate. Glacials show low P-wave velocities and relatively high magnetic susceptibilities. In contrast, interglacials show high P-wave velocities and relatively low magnetic susceptibilities. These temporal changes in P-wave velocity and magnetic susceptibility reflect the climatic history recorded in the sediments and are related to: (1) the production of biogenic carbonate, mainly planktonic foraminifera, and (2) the terrigenous sediment supply that contains magnetic minerals. Below the CCD this pattern disappears and consistently low P-wave velocities and distinctly higher magnetic susceptibilities prevail. The distinct decrease of large P-wave velocity fluctuations is due to the dissolution of carbonate sediments which cause a distinct decrease in sand grain sizes and a consistently low carbonate content (〈 10%). Dilution of magnetic material by the carbonate fraction is minor and the high magnetic susceptibility values and the relatively high amplitude variations in magnetic susceptibility are due to changes in the magnetic mineral concentration of the terrigenous (non-carbonate) fraction. In early Pliocene sediments we also observed covarying velocity and magnetic susceptibility signals that may reflect a predominatly terrigenous control on sedimentation. Our preliminary results demonstrate that a combined use of non-destructive measurements of acoustic and rock-magnetic signals provides a potential paleoceanographic tool for characterizing: (1) glacial-interglacial pelagic sedimentation, (2) pelagic sedimentation above the CCD, (3) increases in carbonate dissolution, and (4) areas below the CCD. Furthermore, rock magnetic fluctuations in sediments below the CCD may provide an important stratigraphic tool for the deep carbonate-free basins of the world's oceans.

Description: Mass-balanced paleogeographic maps are quantitative reconstructions of the earth’s surface at times in the past. They are based on the principle of mass balance: tectonic, erosion and Sedimentation processes acting on the reconstructed surface over a given interval of time cause the mass of Sediment eroded to be equal to the mass of Sediment deposited. Input files consist of: 1) defini tion of the unit areas to form a grid within aregion that has acted as aclosed source-sink System with respect to detrital Sediment; 2) present average elevation of each unit area; 3) representative lithostratigraphic columns for each unit area keyed to a chronostratigraphic framework; 4) a regional mass-age distribution of the Sediment; 5) an estimate of the mass of sediment that was deposited during each time interval; 6) age of ocean crust and age assignments for the contracting material beneath thinned passive Continental margins; 7) a regional sea-level curve; and 8) specifi cation of an appropriate time Step. These data are then manipulated by the program through process constants to produce mass-balanced paleogeographic maps (Shaw and Hay, this volume). The mass-age distributions have a high information content and provide a summary of the geologic history of the region.

Description: Paleogeography, paleotopography, and paleobathymetry of a closed erosion-depositional system can be reconstructed by restoring sedimentary masses to elevated surfaces in a drainage basin based on the inverse of present erosion equations and adjusting for isostasy, sea level changes, sediment compaction, and thermal subsidence. The erosion-deposition history of the northwestern Gulf of Mexico margin and its western-central North American source area during the Cenozoic is used to explore the sensitivity of mass balance reconstructions, and changes in assumptions concerning erosion rate parameters and sea level. Analysis of the distributions of sedimentary material and mass-balanced paleogeographic reconstructions of the study area indicate the following specific results: 1) most of the Pleistocene sediment in the Gulf of Mexico is not of glacial origin but is derived from the high plains and reflects uplift of the Rocky Mountains and High Plains since the Late Pliocene; and 2) paleoshorelines predicted from mass-balanced reconstructions using theHaq et al. (1987) global sea level curve do not match the shoreline indicated by sedimentary sequences and suggest that the amplitude of sea level changes in the Gulf coast is between one-fourth and three-fourths, most likely one-half, that of the published eustatic sea level curve.

Description: The life cycle of loliginid squids has been completed in recirculating seawater systems. Two systems were required: a 2 m diameter circular culture tank (CT) with adjoining 2 m circular filter tank (3000 liters total volume of natural seawater) for culture of hatchlings, 1–60 days old; and a 6 × 2·6 × 1 m raceway culture tank (RW) with a smaller adjoining rectangular filter tank (14 850 liters total volume of artificial seawater) for the grow-out of adults. Both systems were equipped with temperature control apparatus, modular filter units (particle filters and activated carbon), foam fractionators, biological filters (crushed oyster shell) and UV sterilizers. The systems carried low bioloads, 〈 1·0 g/m3 and as high as 0·8 kg/m3, respectively. Water quality was excellent: NH4N was below 0·01 mg/liter in the CT and 0·10 mg/liter in the RW: NO2N was below 0·01 mg/liter in the CT and 0·03 mg/liter in the RW; NO3N was below 12 mg/liter in the CT and below 50 mg/liter in the RW; and pH was above 8·0 in both systems. The design of the systems proved to be behaviorally and physiologically suitable for squids and two species grew to adult size and produced viable young. These systems are compared to other squid maintenance and rearing systems and marine recirculating seawater systems.

Description: An atmospheric general circulation model (GCM) was forced with the observed near-global sea surface temperature (SST) pattern for the period January 1970-December 1985. Its response over the Pacific Ocean is compared with Tahiti and Darwin station sea-level pressure and wind stress analyses obtained from Florida State University. The time-dependent SST clearly induces in the model run a Southern Oscillation that is apparent in the time series of all considered variables. The phase of the GCM Southern Oscillation is as observed but its low-frequency variance is too low and the spatial pattern is confined mainly to the western Pacific. The model is successful in reproducing the warm events of 1972-73 and 1982-83 and the cold event 1970-71, but fails with the cold events 1973-74 and 1975-76 and with the warm event 1976-77. Because the GCM is used as the atmospheric component in a coupled model, the response of an equatorial oceanic primitive equation model to both the modelled and observed wind stress is examined. The ocean model responds in essentially the same way to forcing with the observed wind stress and to forcing that corresponds to the first two low-frequency empirical orthogonal functions (EOFS) of the wind variations. These first two EOFS describe a regular eastward propagation of the so signal from the western Pacific to the central Pacific within about one year. The ocean model's response to the modelled wind stress is too weak. It is similar to the response to the first observed wind stress EOF only. That is, the observed Southern Oscillation appears as a sequence of propagating patterns but the simulated Southern Oscillation appears as one standing pattern. The nature of the deviation of simulated wind stress from observations is further analysed by means of model output statistics.

Description: Maximal growth rates of 15 Antarctic phytoplankton species at 0 degree C ranged from 0.32 to 0.72/d, showing only a weak dependence on cell size. Comparisons were made with two models for size dependence of temperature-corrected rates of maximal growth. Schlesinger's general phytoplankton model predicts a strong size dependence of growth rates and grossly underestimates the maximal growth rates of the larger species, but gives reasonable estimates for the smallest ones. Banse's marine diatom model assumes a weak size dependence of growth rates and gives generally better predictions.

Description: The nutritional status of phytoplankton in a shallow, hypertrophic lake was analyzed by stoichiometry of seston and by enrichment bioassays during a 6-month period. Both methods suggested moderate and temporally interrupted nutrient limitation of reproductive rates. Nitrogen was the most frequently limiting nutrient, phosphorus was next, and silicate limitation of three diatom species occurred only once. The nutritional status of the most abundant individual species could be described by the Monod equation. The nutritional status of the entire phytoplankton assemblage could be described by a modified version of the Droop equation. In accordance with competition theory, phytoplankton species were arrayed along resource ratio gradients. These results are consistent with ecophysiological models derived from culture experiments.

Description: A comparative study of isodideimnine-1 and didemnin B is presented using spcctroecopic methods, partial degradation and partial synthesis. This leads to the conclusion of the presence of a single depsipeptide, namely didemnin B, with (3S,4R,5S) isostatine instead of the previous statine residue. An attempt to determine the whole conformation in solution of didemnin B by using 2D-NMR is also described.

Description: Seismic refraction investigations along a 440-km long profije on the northern Baltic Shield have resolved the crustal structure in this area of Archaean to Early Proterozoic lithosphere formation. The profile, called the POLAR Profile, extends approximately along a SW-NE-oriented line from the Karelian Province in northern Finland across the Lapland Granulite Belt and the Kola Peninsula Province to the Varanger Peninsula in northeastern Norway. At six shotpoints, large explosions (200–1680 kg), and at three shotpoints, small explosions (80 kg) were detonated and recorded at an average station spacing of 2 km, providing high-quality record sections. A two-dimensional cross section of the crust was obtained by forward modelling using ray-tracing techniques. High-velocity bodies are found in the upper crust related to the Karasjok-Kittilä Greenstone Belt and the Lapland Granulite Belt. They extend to a depth of 6–13 km. In the Karelian Province in the southwest, a low-velocity zone was found between the depths of 8 and 14 km. The middle crust shows a slight increase in the average velocities from the southwest to the northeast, and a small velocity jump is found along a mid-crustal boundary between 18 and 21 km. The thickness of the middle crust varies between 16 and 18 km. The lower crust and the crust-mantle boundary (Moho) show considerable lateral variation. The top of the lower crust lies between 26 and 33 km, while its thickness decreases from 21 km in the southwest to 10–14 km beneath the Lapland Granulite Belt and the Inari Terrain, reaching 20 km again in the extreme northeast. The velocities also change laterally. The thin lower crust is characterized by rather low velocities (6.8–6.9 km/s), whereas in the southwest and northeast the velocities (6.9–7.3 km/s) resemble more typical shield structures. The Moho is found at 47 km in the Karelian Province, rises to 40 km beneath the Lapland Granulite Belt and descends to 46 km in the northeastern part of the Kola Peninsula Province. The upper mantle velocities at the Moho range from 8.1 km/s in the region of the thin crust, to 8.5 km/s and more beneath the Karelian Province. It is tempting to suggest that the anomalous lower crust underlying the Lapland Granulite Belt and the Inari Terrain may represent the remnants of an Early Proterozoic back-arc basin that was active prior to the 2.0 to 1.9 Ga plate convergence event, during which the Lapland Granulite Belt was thrust onto the Archaean basement of the Karelian Province. Another explanation is to assume that the velocity reduction in the anomalous lower crust was caused by a rather pronounced uplift of this region following the 1.9-Ga collision event.

Description: Pore fluid venting associated with subduction-induced sediment deformation causes precipitation of calcium carbonate as prominent carbonate chimneys or cement in the accreted sediments across the active continental margin off Oregon and Washington. A depletion of interstitial Ca2+ with a maximum decrease of 50% relative to seawater Ca2+ over only 1.5m depth and reduction in porosity in the deformed sediments suggest that interstitial Ca2+ is removed to form calcium carbonate cement. In contrast, the pore waters of the undeformed abyssal plain sediments show no depletion in dissolved Ca2+. They are either enriched to a maximum of 5% or show no change in dissolved Ca2+. Here the background level of CaCO3 content in the sediment is only 0.1 to 1%. Calcium carbonate precipitation in the deformed sediments probably occurs as the result of upward migration and oxidation of biogenic methane and of the increase in carbonate saturation due to release of excess pore pressure during fluid venting. Upward advection of fluids at rates of 1–28 cm y−1 is predicted from diffusion-advection-reaction models applied to the downcore concentration profiles of dissolved Ca2+ and NH4+ in the tectonically-deformed sediments. The range of predicted flow rates is related to the type of calcium carbonate lithification; i.e. slow rates generate cement and fast rates generate chimneys. Carbonate mineral precipitation associated with pore fluid venting requires direct transfer of Ca2+ from the oceanic basement to the accretionary complex. Such a mechanism leads us to propose that the accretionary complexes of the global plate subduction zones are a major sink for crustal Ca2+. A global flux of crustal Ca2+ that is removed by carbonate mineral precipitation may be as muc3 as the hydrothermal Ca-input. This significant Ca-flux, not previously considered in the global geochemical budget, implies that pore fluid venting in subduction zones may also act as a global sink or source for other elements.

Description: Ocean crustal carbon uptake during seafloor alteration at DSDP Sites 417A, 417D, and 418A exceeds the estimated loss of carbon during magmatic ridge outgassing. If these sites are representative for oceanic crust in general, 2.2–2.9 × 1012 moles of carbon are removed from the oceans per year as a net flux of carbon between the oceanic crust and seawater. Although most of this carbon occurs as calcium carbonate, this ocean crustal carbonate probably cannot be considered part of the marine calcium carbonate sink since much of the Ca in these carbonates must be derived from basalt alteration that is not balanced by a concomitant uptake of seawater Mg. Our present estimate cannot be satisfactorily applied to global carbon budgets, because of uncertainties in the bulk budget of ocean floor alteration and because of the uniqueness of our estimate. Yet, our data document that the formation of ocean crust provides a significant sink for carbon that should be included in models of the global cycling of carbon. Furthermore, magmatic outgassing during ocean crust emplacement and seafloor basalt alteration may provide a buffering mechanism for atmospheric carbon.

Description: The long-term record of glacial/interglacial cycles indicates three major paleoceanographic regimes in the Norwegian Sea. The period since the first major glaciation over Scandinavia at 2.56 Ma is characterized by high-frequency, low-amplitude oscillations of ice-rafted debris inputs, a lowered salinity, and decreased carbonate shell production in surface waters as well as overall strong carbonate dissolution at the sea floor. These conditions indicate a more zonal circulation pattern in the Northern Hemisphere and a relative isolation of surface and bottom waters in the Norwegian Sea. The generally temperate glacial climate was only interrupted by episodic weak intrusions of warm Atlantic waters. These intrusions have been detected in considerable magnitude only at Site 644, and thus are restricted to areas much closer to the Norwegian shelf than during earlier periods. The interval from 1.2 to 0.6 Ma is characterized by an increase in carbonate shell production and a better preservation, as well as a change in frequency patterns of ice-rafted debris inputs. This pattern reflects increasing meridionality in circulation-strengthening contrasts in the Norwegian Sea between strong glaciations and warm interglacials. The past 0.6 Ma reveal high-amplitude oscillations in carbonate records that are dominated by the 100-k.y. frequency pattern. Glacial/interglacial sedimentary cycles in the ODP Leg 104 drill sites reveal a variety of specific dark lithofacies. These dark diamictons reflect intense iceberg rafting in surface waters fed by surges along the front of marine-based parts of the continental ice sheets in the southeastern sector of the Norwegian Sea and are associated with resuspension of reworked fossil organic carbon and strong dissolution at the sea floor. Piling up of huge iceberg barriers along the Iceland-Faeroe-Scotland Ridge might have partially blocked off surface water connections with the North Atlantic during these periods.

Description: Coarse-fraction studies of sediments recovered during ODP Leg 104 are used to reconstruct paleoclimatic and paleoceanographic environments on a time scale of 0.1 to 0.5 m.y. for the past 20 Ma. These investigations suggest that relatively warm climates and isolated deep water conditions prevailed prior to 13.6 Ma and between 5.6-4.8 Ma. The first major deep water outflow from the Norwegian-Greenland Sea into the North Atlantic took place at about 13.6 Ma. Progressive cooling linked to increased deep water renewal in the Norwegian-Greenland Sea appears to have occurred between 13.6-5.6 Ma and 4.8-3.1 Ma. A major onset of ice-rafted debris is recorded at 2.56 Ma. Terrigenous coarsefraction components show important fluctuations with two major peaks during the past 0.8 Ma.

Description: Sites 642, 643, and 644 were investigated for planktonic foraminifers. Frequent occurrences of barren intervals caused by dissolution as well as low- diversity and long-ranging assemblages reduce the stratigraphic resolution of these records. Based on Neogloboquadrina species a local zonation, correlated with high-latitude North Atlantic schemes, is proposed for the middle Miocene to Quaternary and correlated with paleomagnetic records. The middle to late Miocene boundary is defined by the last appearance datum of Neogloboquadrina mayeri and the first appearance datum of Neogloboquadrina acostaensis. Late Miocene age is defined by a N. acostaensis zone, whereas latest Miocene to Pliocene zones are defined by dextral and sinistrally coiling Neogloboquadrina atlantica. The top of the Pliocene is characterized by dextral and sinistrally coiling Neogloboquadrina pachyderma. The Pleistocene is defined by a nearly monospecific assemblage of Neogloquadrina pachy derma in its sinistrally coiled and encrusted variety.

Description: Different generations of complex authigenic carbonates formed in siliceous muds (lithologic Unit IV) and hemipelagic clays (lithologic Unit V) of ODP Site 643, Leg 104 Norwegian Sea. The dominant phase in Unit IV is an early diagenetic Mn, Fe-calcite with a strong negative 5 13C (- 14 to - 16 %o) signature, and slightly negative 8 180 values. The strong negative 8 13C results from extensive incorporation of 12C-enriched C02 derived from bacterial degradation of marine organic matter into early Mn, Fe—calcite cements. Concomitant framboidal pyrite precipitation and abundant SEM microtextures showing excellent preservation of delicate structures of fragile diatom valves by outpourings with early Mn-calcites strongly support their shallow burial formation before the onset of compaction. Later generations of authigenic mineralizations in lithologic Unit IV include minor amounts of a second generation of calcite with platy crystals, possibly precipitated along with opal-A dissolution, and finally opal-CT crystallization in deeper seated environments overgrowing earlier precipitates with films and lepispheres. The last mineralization is collophane (fluor apatite) forming amorphous aggregates and tiny hexagonal crystals. Authigenic mineral assemblages in lithologic Unit V consist of rhodochrosites, transitional rhodochrosite/manganosiderites, and apatite. A negative 8 13C (- 7.1 to - 15.6 %o) and a fluctuating 8 180 signal indicates that the micritic to sparitic rhodochrosites, transitional rhodochrosites/manganosiderites were formed at various burial depths. C02 resulted from organic matter degradation in the lowermost sulfate reduction zone and from biogenic methane generation in the lowermost sediments, resulting in variable and negative 8 13C signals. The change in carbonate mineralogy reflects major compositional differences compared to sediments in Unit IV. Most prominent is an increase in altered ash as a primary sediment component and a sudden decrease of siliceous microfossils. Upward diffusion of cations, lowered salinities in pore waters, and elevated temperatures provide diagenetic environments favoring increased remobilization processes.

Description: Atlantic salmon (Salmo salar) from Little Gull Lake on the Gander River system of central Newfoundland were found to be electrophoretically polymorphic at 5 of 20 protein loci screened. Four of the polymorphic loci were structural and one was regulatory. Major heterozygote deficiencies relative to Castle–Hardy–Weinberg expectations were detected at the two most polymorphic loci, Aat-3 and Mdh-3,4, and significant nonrandom associations between genotypes at these loci and the other polymorphic loci, Sdh-1, Me-2, and Pgm1-t, were also found. The heterozygote deficiencies and the nonrandom genotype associations were attributable to the admixture of genetically distinct gene pools of resident and anadromous salmon in the lake. This is the first documented case of coexistence of reproductively separated populations of Atlantic salmon of the two life history types, and shows that the sympatric occurrence of the two forms can represent between-population variation.

Description: Manganese nodules from the Kane Gap (a deep sea channel connecting the Sierra Leone and Gambia Basins off West Africa) were investigated chemically and dated by10Be along cross-sections. Comparing the nodule structure with the stratigraphy of the related sediments, the following conclusions are drawn concerning the sedimentation processes during the last 4 to 6×106 years: The growth of the nodules started about 4 to 4.5 Ma before present during or near to the end of a period of erosion on a fossil-free, probably Miocene sediment. During the first phase of only a few hundred thousandyears, the nodules grew very quickly (7 to 〉18 mm/Ma). Fe-rich hydrogenetic material formed the internal sections of the nodules during this time. Slowing down of the bottom currents, resulting in deposition of thin sediment covers for short intervals, caused the character of the nodules to change to a more diagenetic composition. The growth rates were reduced to about 1 to 2 mm/Ma. The time of slowing is roughly 3 to 4 Ma BP. Probable uncertainties of the dating and growth rates resulting from supposed changes of the10Be supply to the nodules due to variations of the near bottom environment are discussed.

Description: Numerous fresh ash layers comprise about 0.3% by volume of Neogene to Holocene sediments drilled at Leg 104 Sites 642 and 643 (Wring Plateau, North Atlantic). Median grain sizes of the ashes are about 100 /xm and maximum grain sizes range up to 1200 fim. Rhyolitic pumice shards dominate, with minor bubble wall shards. Basaltic shards are poorly vesicular and blocky or round. Phenocrystic plagioclase, zircon, and clinopyroxene occur in the rhyolitic, plagioclase, and clinopyroxene phenocrysts and basaltic lithics in the basaltic tephra. Quartz, amphibole, clinozoisite, and rutile are interpreted as xenocrysts. All ash layers are well-sorted and represent distal fallout from major explosive eruptions. Most ashes are rhyolitic (high-K and low-K) in composition, some are bimodal (tholeiitic and rhyolitic). Early Miocene tephra is dominantly basaltic. Iceland is inferred to be the likely source region for most ashes. Late Miocene high-K rhyolites may have originated from the K-rich Jan Mayen magmatic province. One Quaternary layer with biotite and alkali feldspar phenocrysts may have been derived from Jan Mayen Island. Four individual Pliocene to Holocene ash layers from Sites 642 and 643 can be correlated fairly well. Upper Miocene layers are tentatively correlated as a sequence between Sites 642 and 643. Average calculated layer frequencies are about three layers/m.y. through the Pliocene and Pleistocene and five to eight layers per m.y. through the middle and late Miocene, suggesting rather continuous volcanic activity in the North Atlantic. Episodic magmatic activity during Neogene epochs in this part of the North Atlantic, as postulated in the literature, cannot be confirmed.

Description: A global compositional dichotomy for N-MORB magma (N1/N2) is recognized on the basis of Na2O, TiO2, CaO, and Al2O3 contents, and their respective ratios. We have characterized the two magma sub-types by means of their trace element patterns, and attempted to explain the differences in major and trace element contents in terms of a partial melting model, using data from DSDP/IPOD Leg 82. Mass balance calculations for N-MORB glass and rock compositions indicate that differences between N1-and N2-MORB are consistent with simple differences (5%–10%) in the degree of partial melting of a plagioclase-(±spinel) lherzolite, at pressures 〈10 kbar, rather than their respective derivation from plagioclase- and spinel-lher-zolite sources. Based on published and calculated partition coefficients, and calculated source magmaphile trace element compositions, the calculations indicate that the overall range of N-MORB compositions may be derived by between approximately 8% and 20% partial melting of a fertile lherzolite source. Fluid dynamic and melt kinematic considerations will probably necessitate refinement of the model, but should also take account of its qualitative precepts.

Description: Along the continental margin of northern Peru, Sea Beam bathymetry and seismic reflection records reveal features from mass wasting in the middle and lower slope areas. A curved scarp cuts the middle slope and marks a slip surface seaward of which a 20 by 33 km block was displaced 800 m and back rotated 5° as it moved downslope. The front of that block is itself marked by a 1‐km‐high curved scar where the block failed and created a ∼30‐km debris flow avalanche. The avalanche morphology of closed highs and lows without directional fabric covers the lower slope and trench axis seaward of the detached block. If the slip was catastrophic, a local ∼50‐m‐high tsunami was generated. This example documents the type of slope failure commonly inferred as a source of destructive tsunamis. Since the block was detached along faults that displace beds 3–5 km deep, it represents more than a superficial slide where sediment was locally oversteepened. The detached block includes rocks that were part of the continental margin since at least Eocene time in front of which a 15‐km‐wide accretionary complex subsequently developed. Apparently, only low levels of horizontal compression could be transmitted into the upper plate because of weak coupling across the Benioff zone. This may have permitted detachment and mass movement of the block despite the long history of plate convergence here. Tsunamogenic slides and mass wasting at trench depths are difficult to detect without modern high‐resolution techniques.

Description: The imaging of a multichannel seismic record was improved by reprocessing using pre-stack techniques. The reprocessed record shows structures that indicate tectonic erosion and gravity collapse at the front of the Japan Trench margin. Much of the lower slope appears to be underlain by a detached, coherent block of continental crust. The lower slope has failed by mass wasting and the resulting apron of slump debris at the base of the slope has become involved in thrust faulting at the front of the subduction zone. Slumping continues as long as debris is removed from the front of the margin by subduction, and the apron cannot build up sufficiently to stabilize the failing lower slope. Truncated beds at the base of the upper plate indicate subcrustal erosion as well, this probably being the main cause of massive subsidence of the margin. Subsidence was the cause of oversteepening, destabilization and subsequent gravity collapse of the leading edge of the upper plate.

Description: Authigenic carbonates were recovered in lower to middle Eocene claystones at Ocean Drilling Program Site 647 in the Labrador Sea. Detailed chemical, petrographic, and X-ray investigations reveal that these diagenetic carbonates have a complex mineralogical composition. At least five different carbonate phases are identified: calcium-rich rhodochrosite, rhodochrosite, manganosiderite, siderite, and calcite. Manganese carbonates are the dominant carbonate phases formed throughout the section. Textural analyses show two major generations of carbonate formation. Early cementation of micritic carbonate in burrow structures was followed by carbonate cementation forming microsparry to sparry crystals. At approximately 620 meters below seafloor (mbsf), three concretions of iron carbonates occur, which indicates a special pore-water chemistry. Thin section analyses from this level show (1) several generations of diagenetic carbonates, (2) widespread secondary cavity formation in burrow structures, and (3) various cement precipitations in voids. We suggest that this level represents a hiatus or highly condensed sequence, as indicated by (1) the low carbonate content in host sediments, (2) carbonate dissolution reflected by the high ratio of benthic to planktonic foraminifers, and (3) complex diagenetic alteration in the carbonate concretions. Iron and manganese enrichments observed in lithologic Unit IV may have been derived from a hydrothermal source at the adjacent, then active, Labrador Sea mid-ocean ridge. Authigenic smectites forming numerous pseudomorphs of siliceous microfossils are precipitated in burrow structures. We propose that diagenetic smectite formation from biogenic opal and iron oxyhydroxide (analogous to smectite formation in surface sediments of the East Pacific area) occurred in the Labrador Sea during the early and middle Eocene.

Description: Continuous sediment sections spanning the last 2.8 Ma have been studied using stable isotope stratigraphy and sedimentological methods. By using paleomagnetic reversals as a chronostratigraphic tool, climatic and paleoceanographic changes have been placed in a time framework. The results show that the major expansion of the Scandinavian Ice Sheet to the coastal areas occurred in the late Neogene period at about 2.8 Ma. Relatively high-amplitude glacials appeared until about 2 Ma. The period between 2.8 and 1.2 Ma was marked by cold surface water conditions with only weak influx of temperate Atlantic water as compared with late Quaternary interglacials. During this period, climatic variations were smaller in amplitude than in the late Quaternary. The Norwegian Sea was a sink of deep water throughout the studied period but deep water ventilation was reduced and calcite dissolution was high compared with the Holocene. Deep water formed by other processes than today. Between 2 and 1.2 Ma, glaciations in Scandinavia were relatively small. A transition toward larger glacials took place during the period 1.2 to 0.6 Ma, corresponding with warmer interglacials and increasing influx of temperate surface water during interglacials. A strong thermal gradient was present between the Norwegian Sea and the northeastern Atlantic during the Matuyama (2.5-0.7 Ma). This is interpreted as a sign of a more zonal and less meridional climatic system over the region as compared with the present situation. The transition towards more meridionality took place over several hundred thousand yr. Only during the last 0.6 Ma has the oceanographic and climatic system of the Norwegian Sea varied in the manner described from previous studies of the late Quaternary.

Description: The ice-proximal environment of the Nordaustlandet tidewater ice cap, Svalbard Archipelago, is one of the best analogues for understanding glacial geologic processes of northern continental shelves during initial Pleistocene deglaciation. Investigations of the proglacial region in 1980–1983 showed that the sedimentary environment is dominated by numerous meltwater outflows which discharge sediment-laden water from subglacial meltwater streams during the summer. Two large, stable meltwater outflows were observed in embayments along the southern part of the ice front. Landsat images show that both outflows have been in approximately the same position since at least 1976. They are located at the intersection of glacial drainage basins and centered over depressions in the underlying bedrock. An “outflow valley” extending away from the ice front was observed in front of the western meltwater outflow. Sidescan sonar profiling along the glacier front showed a 200 m wide gap in acoustic reflection at the base of the western meltwater outflow, probably caused by meltwater effluence. Enhanced sediment accumulations in this region, observed as a ≈ 3 ms sediment drape in front of the outflow, and large arcuate ridges in the outflow valley, testify to the transport efficiency of the subglacial meltwater stream. Several mounds, up to about 25 m high and 200 m wide, are observed on sidescan and 3.5 kHz profiles directly in front of the outflow. Although samples from these structures are absent, they are most likely composed of sediment and are similar to beaded eskers observed in Pleistocene glacimarine sequences indicating locally very high sedimentation rates. Fine-grained components of the subglacial discharge incorporated in the buoyant meltwater plume are usually entrained in a westerly coastal current. Elevated suspended particulate material concentrations are observed within the coastal waters in a region extending about 15 km perpendicular to the glacier front and at least 60 km along the ice front extending into the northwestern Barents Sea.

Description: During the summer 1987 expedition of the polar research vessel‘Polarstern’in the Eurasian Basin of the Arctic Ocean, sea ice at about 84-86°N and 20-30°E was found to have high concentrations of particulate material. The particle-laden ice occurred in patches which often darkened more than half the ice surface at our northernmost positions. Much of this ice appeared to be within the Siberian Branch of the Transpolar Drift stream, which transports deformed, multi-year ice from the Siberian shelves westward across the Eurasian Basin. Lithogenic sediment, which is the major component of the particulate material, may have been incorporated during ice formation on the shallow Siberian seas. Diatoms collected from the particle-rich ice surfaces support this conclusion, as assemblages were dominated by a marine benthic species similar to that reported from sea ice off the coast of northeast Siberia. Based on drift trajectories of buoys deployed on the ice it appears that much of the particle-laden ice exited the Arctic Ocean through the Fram Strait and joined the East Greenland Current. Very different sea ice characteristics were found east of the Yermak Plateau and north of Svalbard and Frans Josef Land up to about 83-84°N. Here sea ice was thinner, less deformed, with lower amounts of lithogenic sediment and diatoms. The diatom assemblage was dominated by planktonic freshwater species. Trajectories of buoys deployed on sea ice in this region indicated a tendency for southward transport to the Yermak Plateau or into the Barents Sea.

Description: Ice-rafted fossils of late Cretaceous and Tertiary age were detected in Pleistocene-Pliocene glacially influenced sediments of the Vdring Plateau, eastern Norwegian Sea. The ice-rafted associations contain frequent Inoceramus (Bivalvia) prisms and rare occurrences of both benthic and planktonic foraminifers of Miocene, Oligocene, and Maastrichtian to Campanian age. As source areas, shallow outcrops on the Norwegian Continental Shelf as well as the Greenland Shelf and the North and Baltic Seas have to be considered.

Description: We examine the closure of the current plate motion circuit between the African, North American, and Eurasian plates to test whether these plates are rigid and whether the Gloria fault is an active transform fault. We also investigate the possible existence of microplates that have been previously proposed to lie along these plate boundaries, and compare the predicted direction of motion along the African‐Eurasian plate boundary in the Mediterranean with the direction of slip observed in earthquakes. From marine geophysical data we obtain 13 transform fault azimuths and 40 3‐m.y.‐average spreading rates, 34 of which are determined from comparison of synthetic magnetic anomaly profiles to ∼140 observed profiles. Slip vectors from 32 earthquake focal mechanisms further describe plate motion. Detailed magnetic surveys north of Iceland provide 11 rates in a region where prior plate motion models had few data. Magnetic profiles north of the Azores triple junction record a rate of 24 mm/yr, 4 mm/yr slower than used by prior models. Gloria and Sea Beam surveys accurately measure the azimuths of seven transform faults; our plate motion model fits six of the seven within 2°. Two transform faults surveyed by Gloria side scan sonar lie near FAMOUS area transform faults A and B and give azimuths 13° clockwise of them. Because recent studies show that short‐offset transforms, such as transforms A and B, are in many places oblique to the direction of plate motion, we exclude azimuths from transforms with less than 35‐km offset. The best fitting and closure‐enforced vectors fit the data well, except for a small systematic misfit to the slip vectors: On right‐lateral slipping transforms, slip vectors tend to be a few degrees clockwise of plate motion and mapped fault azimuths, whereas on left‐lateral slipping transforms, slip vectors tend to be a few degrees counterclockwise of plate motion and mapped fault azimuths. We search the long Eurasia‐North America boundary for evidence of an additional plate, but find no systematic misfits to the data. In particular, if a Spitsbergen plate exists and moves relative to Eurasia, its motion is less than 3 mm/yr. An Africa‐Eurasia Euler vector determined by adding the Eurasia‐North America and Africa‐North America Euler vectors is consistent with the Gloria fault trend and with slip vectors from eastern Azores‐Gibraltar Ridge focal mechanisms. A small circle, centered at the Africa‐Eurasia closure‐enforced pole, fits the trace of the Gloria fault. The model in which closure was enforced predicts ∼4 mm/yr slip across the Azores‐Gibraltar Ridge, and west‐northwest convergence near Gibraltar, ∼45° more oblique than suggested by a recent model based on compressive axes of focal mechanisms. Moreover, our model predicts directions of plate motion that agree well with northwest trending slip vectors from thrust earthquakes between Gibraltar and Sicily. Because closure‐enforced vectors fit the data nearly as well as the best fitting vectors, we conclude that the data are consistent with a rigid plate model and with the Gloria fault being a transform fault.

Description: Many physical properties of silicate minerals can be modeled as a combination of basic polyhedral units (Hazen, 1985, 1988). It follows that their thermodynamic properties could be modeled as the sum of polyhedral contributions. We have determined, by multiple regression, the contribution of the [4]A12O3,[6]A12O3, [6]Al(OH)3, [4]SiO2, [6]MgO, [6]Mg(OH)2,[6]CaO, [8-z]CaO, [6−8]Na2O, [8−12]K2O, H2O, [6]FeO, [6]Fe(OH)2, and [6]Fe2O3 components to the total ΔG0f and ΔH0f of a selected group of silicate minerals. Using these data we can estimate the ΔG0f and ΔH0f of other silicate minerals from a weighted sum of the contribution of each oxide and hydroxide component: ΔG0f = Σnigi ,  and ΔH0f = Σni hi, where ni is the number of moles of the oxide or hydroxide per formula unit and gi and hi, are the respective molar free energy and enthalpy contribution of 1 mol of each oxide or hydroxide component. The technique outlined here can be used to estimate the thermodynamic properties of many silicate phases that are too complex or too impure to give reliable calorimetric measurements. Experimentally measure ΔG0f and ΔH0f vs. predicted ΔG0f and ΔH0f for the minerals used in the model have associateda verager esiduals of 0.26% and 0.24% respectively. Thermodynamic properties of minerals not used in the model but for which there are experimentally determined calorimetric data have average differences between measured and predicted values of 0.25% for ΔG0f or 18 minerals and 0.22% for ΔH0f for 20 minerals.

Description: Nine specimens of a cirrate octopod were captured during the "Valdivia" exploratory oceanographic trawl survey cruise (May and June 1981) conducted by the Spanish research ship CHICHA TOUZA in the southeastern Atlantic on the Valdivia Bank, approximately 600 kilometers west of coast Namibia. Upon examination, the specimens were found to represent a new species of the genus Opisthoteuthis Verrill, 1883, the second species of the genus described or recorded from the Atlantic Ocean. The measurements and indices used are those defined by Voss (1963, 1982) and Roper and Voss (1983). The holotype and one paratype are deposited in the United States National Museum of Natural History (USNMNH). The other paratypes are deposited in the Instituto de Ciencias del Mar de Barcelona (ICMB), and the Instituto de Investigaciones de Vigo (IIMV). The following indices were used: Mantle with index (MWI): greatest width of mantle measured between the bases of the fins as a precentage of dorsal mantle length. Head width index (HWI): greatest width of head measured across eyes as a percentage of dorsal mantel length. Fin length index (FLI): length of fins measured from the midpoint of the base of the fin to the fin tip as a percentage of the head width. Fin width index (FWI): greatest fin witdh as a percentage of fin length. Mantle arm index of the deepest sector of the web as a percentage of the length of the longest arm. Sucker diameter index (SI): diameter of largest sucker as a percentage of mantle length. Cirrus length index (CiLI): length of the longest cirrus as a percentage of mantle length.

Description: Cephalopods are exclusively marine molluscs and should be included among the organisms that are of general interest to marine biologists. As to experimental embryology, Naef has already stressed the suitability of cephalopod embryos for experimental work. The whole body of information accumulated in this field during the past half century since Naef published his monograph was reviewed by Marthy. This field of research is clearly underrated by many developmental biologists who could profit by the topological simplicity of the blastulation pattern in cephalopods, which contrasts with the spiralian mode of other molluscs. Questions raised by comparative/evolutionary embryology, following the tradition of descriptive developmental morphology, are truly stimulating to the field of experimental embryology, and vice versa. However, experimental studies are generally possible with only a limited number of models, which, in the case of cephalopods, appear to be embryos of medium to small size. On the other hand, some of the most intriguing questions in cephalopod biology are related to those forms that produce eggs of extremely large size. This chapter gives a brief overview of these recent studies placing them in the chronological sequence of embryogenesis. Studies covering early stages of embryonic development as well as later ones will be cited at least once in the section dealing with the earliest stage considered. Most of these investigations ultimately rest on the basic work by Naef.

Description: Detailed studies of benthonic foraminifera, stable isotopes, and lithofacies in cores from the southeastern Alpha Ridge, central Arctic Ocean, reveal some new aspects of Arctic Ocean paleoceanography. High ratios of benthonic to planktonic foraminifera are found in most of the Quaternary sediment units, and ratios of 1:1 appear to characterize the Arctic deep-water sediments. Benthonic foraminifera in the carbonate mud unit M show a succession of calcareous species reflecting increased influx of Norwegian Sea bottom water to the Arctic Ocean during the past 0.4 m.y. Foraminiferal and lithological data indicate less-uniform sedimentation during a warmer interval from 0.4 to 0.6 Ma, when most of the silty lutite unit L was deposited at the CESAR site. Lower Pleistocene units J to I contain less limestone and more dolomite, and they contain a uniform faunal assemblage with low numbers of calcareous foraminifera. Upper Pliocene units H to AB contain rare limestone and relatively large amounts of do-lomite and quartz sand. Middle to upper Pliocene units AB to A3 are marked by abundant sand-sized ferromanganese-coated particles, which in many cases have a silt nucleus; hence, much of the coarse sand in these units does not indicate increased ice rafting. The Pliocene sediments mostly contain a low-diversity assemblage of agglutinated foraminifera, but a mixed calcareous/arenaceous fauna occurs in a short interval above the Matuyama-Gauss boundary (2.4 Ma). Stable-isotopic curves occur within sequences which broadly correspond to stages 1-9 of the global record; below stage 9, the record is discontinuous. Strong vertical mixing apparently prevailed during most of the Pliocene and early Pleistocene, then decreased during the past 0.4 m.y. owing to damping by a perennial ice cover. Isotopic and foraminiferal data, however, suggest that an interval of perennial sea ice also occurred during the late Pliocene at the time of the earliest glacial event recorded in the North Atlantic.

Description: Durch in-situ Experimente wurden die Abbaugeschwindigkeiten toter Aalmuttern Zoarces viviparus und Dreistachliger Stichlinge Gasterosteus aculeatus im küstennahen Flachwasserbereich der westlichen Ostsee untersucht. Die Abbaustadien wurden photographisch dokumentiert, und durch Gewichtsverlustmessungen quantitativ erfasst. Es zeigte sich, daß der Abbau in drei Phasen unterteilt ist und innerhalb 12-16 Tagen stattfindet. Die Größe der Fischkadaver und die Zusammensetzung der aasfressenden Makrofauna haben nur einen geringen Einfluß auf die Abbaudauer. In-situ Untersuchungen zum Verhalten von Z.viviparus und G.aculeatus bei Sauerstoffmangel wurden durchgeführt. G.aculeatus zeigte ausgeprägte Fluchtreaktionen bei 70% Sauerstoffsättigung, verhaltensphysiologische Störungen wurden unterhalb 60% Sättigung deutlich. Z.viviparus reagierte auf Sauerstoffmangel mit frühzeitiger Reduktion der lokomotorischen Aktivität und überlebte 60 Minuten in sauerstoffreiem Wasser.

Description: Flume experiments were conducted to determine how a pervasive rain of sand might affect the development of bedforms, internal structures, and grain fabric in a bed aggrading from this fallout. During otherwise standard flume runs, sediment similar to that in the bed (M z = 2.13 phi ; sigma (sub phi ) = 0.63 phi ) rained from overhead bins extending the length of the 9-meter recirculating flume. Consequent rates of bed aggradation ranged to 4.2 cm min (super -1) . The experiments are viewed as having particular relevance to deposition from turbidity currents. Under upper-plane-bed conditions, so long as low rates of sediment feed prevailed, parallel lamination developed from rapidly migrating, millimeter-scale bed-load sheets. At high rates of feed, lamination was suppressed, suggesting that rapid aggradation can account for the "massive" structure characteristic of Bouma A divisions of turbidites. When flow conditions were maintained within the dune stability field for clear-water runs, established dunes persisted at all sediment fallout rates examined (bed aggradation 〈= 4.0 cm min (super -1) ), apparently contradicting a suspicion that the underrepresentation of medium-scale cross-bedding in turbidites might be attributable to suppression of dunes by sediment rain. It was not feasible to test whether sediment rain might inhibit development of nascent dunes, however. Ripples proved stable across the range of fallout rates examined. Depositional fabrics, deduced from anisotropy of magnetic susceptibility, confirmed that under upper-plane-bed conditions (representative of Bouma divisions A and B) grain orientation is current-parallel and equally well developed for all sedimentation rates. Up-current imbrication, consistently steeper than what is typically found in upper-plane-bed stream deposits, increased in steepness in direct proportion to sediment fallout and may provide a useful basis for estimating aggradation rates during deposition of divisions A and B of ancient turbidites.

Description: For the three Northern Atlantic weatherships C, L and K, profiles of humidity are investigated with the help of empirical orthogonal functions (EOF's) for the period April 22 and October 11 1979. The EOF's are eigenfunctions of the coveriance mntrix of the humidity values at different pressure levels. With the aid of such functions and the connected time dependent coefficients the original humidity profilcs can be approximated. Each of these EOF's contains independent information about the various physical proccsses influencing the humidity profiles. Thus the first EOF represents dry or moist air in the whole troposphere. A positiv second EOF characterizes a stable troposphere with a boundary layer present (typical for a high pressure area), a negativ second EOF marks unstable conditions without a boundary layer (typical of low pressure area). The zero-crossing of the second EOF represents the average heigth of the boundary layer. Criteria are discussed, which can be used to determine the number of orthogonal functions which are relevant and significant to describe the humidity profiles. The temporal developments of the EOF's are analysed. The errors of the reproduced vertical profiles and of the nearsurface humidity are calculated and discussed. The nearsurface humidity can be connected with an error of 0.66 g/Kg if two EOF's are used. Whilst no trend is found for the EOF's of the two northern weatherships (C+L), a rise could be determined of the zero-crossing of the second EOF (mean boundary layer heigth) towards midsummer at weathership K. The EOF's are derived with SST taken into considaration, to investigate its effect on the vertical humidity profile. An experiment is carried out with data ensembles of different time periods to find out whether the EOF's are constant during the whole period of consideration. The errors of the calculated near surface humidity are compared using the EOF's derived for the different periods. An investigation did not reveal strong correlation between the time coefficients and synoptical observations as cloud cover, wind speed and direction.