Analysis of elements at DSDP Holes 70-506 and 70-509B

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

Illustrations of manganese nodules dredged from the Upper Jarvis Inlet

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.

Minerals, geochemistry and x-ray power characteristics at DSDP Sites 54-424, 60-458 and 60-459

Secondary minerals filling veins and vesicles in volcanic basement at Deep Sea Drilling Project Sites 458 and 459 indicate that there were two stages of alteration at each site: an early oxidative, probably hydrothermal, stage and a later, low-temperature, less oxidative stage, probably contemporaneous with faulting in the tectonically active Mariana forearc region. The initial stage is most evident in Hole 459B, where low-Al, high Fe smectites and iron hydroxides formed in vesicles in pillow basalts and low-Al palygorskite formed in fractures. Iron hydroxides and celadonite formed in massive basalts next to quartz-oligoclase micrographic intergrowths. Palygorskite was found in only one sample near the top of basement in Hole 458, but it too is associated with iron hydroxides. Palygorskite has previously been reported only in marine sediments in DSDP and other occurrences. It evidently formed here as a precipitate from fluids in which Si, Mg, Fe, and even some Al were concentrated. Experimental data suggest that the solutions probably had high pH and somewhat elevated temperatures. The compositions of associated smectites resemble those in hydrothermal sediments and in basalts at the Galapagos mounds geothermal field. The second stage of alteration was large-scale replacement of basalt by dioctahedral, trioctahedral, or mixed-layer clays and phillipsite along zones of intense fracturing, especially near the bottom of Holes 458 and 459B. The basalts are commonly slickensided, and there are recemented microfault offsets in overlying sediments. Native copper occurs in one core of Hole 458, but associated smectites are dominantly dioctahedral, unlike Hole 459B, where they are mainly trioctahedral, indicating nonoxidative alteration. The alteration in both holes is more intense than at most DSDP ocean crust sites and may have been augmented by water derived from subducting ocean crust beneath the fore-arc region.

Composition of drilled sediments and pore waters from the continental slope of the Northern Gulf of Mexico

Pore waters were analyzed from 6 holes drilled from M.V. "Eureka" as a part of the Shell Oil Co. deeper offshore study. The holes were drilled in water depths of 600-3000 ft. (approximately 180-550 m) and penetrated up to 1000 ft. (300 m) of Pliocene-Recent clayey sediments. Salt and anhydrite caprock was encountered in one diapiric structure on the continental slope. Samples from holes drilled near diapiric structures showed systematic increases of pore-water salinity with depth, suggestive of salt diffusion from underlying salt plugs. Anomalous concentrations of K and Br indicate that at least one plug contains late-stage evaporite minerals. Salinities approaching halite saturation were observed. Samples from holes away from diapiric structures showed little change in pore-water chemistry, except for loss of SO4 and other variations attributable to early-stage diagenetic reactions with enclosing sediments. Thus, increased salt concentrations in even shallow sediments from this part of the Gulf appear to provide an indicator of salt masses at depth.

Seawater carbonate chemistry in Kongsfjorden, Svalbard, May 2009

Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels of 280, 380, 550, 760 and 1020 µatm and at control (0°C) and elevated (4°C) temperatures. The respiration rate was unaffected by pCO2 at control temperature, but significantly increased as a function of the pCO2 level at elevated temperature. pCO2 had no effect on the gut clearance rate at either temperature. Precipitation of CaCO3, measured as the incorporation of 45Ca, significantly declined as a function of pCO2 at both temperatures. The decrease in calcium carbonate precipitation was highly correlated to the aragonite saturation state. Even though this study demonstrates that pteropods are able to precipitate calcium carbonate at low aragonite saturation state, the results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems.

Seawater carbonate chemistry and biological processes during experiments with Limacina helicina, 2009

Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels of 280, 380, 550, 760 and 1020 µatm and at control (0°C) and elevated (4°C) temperatures. The respiration rate was unaffected by pCO2 at control temperature, but significantly increased as a function of the pCO2 level at elevated temperature. pCO2 had no effect on the gut clearance rate at either temperature. Precipitation of CaCO3, measured as the incorporation of 45Ca, significantly declined as a function of pCO2 at both temperatures. The decrease in calcium carbonate precipitation was highly correlated to the aragonite saturation state. Even though this study demonstrates that pteropods are able to precipitate calcium carbonate at low aragonite saturation state, the results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems.

(Table 1) Sr and S isotope compositions of marine barites from ODP Hole 123-765C

Barite can precipitate in microenvironments in the water column (marine barite), from supersaturated pore fluids at the oxic-anoxic boundary within marine sediments and where Ba-rich pore fluids are expelled and come into contact with sulfate-rich seawater (diagenetic barite), or from hydrothermal solutions (hydrothermal barite). Barite is relatively resistant to alteration after burial and has been used in paleoceanographic studies to reconstruct seawater chemistry and productivity through time. For such applications it is very important to determine the origin of the barite used, because both diagenetic and hydrothermal barite deposits may not accurately record the open-ocean contemporaneous seawater chemistry and productivity. We show here that it is possible to distinguish between the different types of barite by using Sr and S isotopes along with crystal morphology and size characteristics.

Decline in growth of foraminifer Marginopora rossi under eutrophication and ocean acidification scenarios

The combination of global and local stressors is leading to a decline in coral reef health globally. In the case of eutrophication, increased concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) are largely attributed to local land use changes. From the global perspective, increased atmospheric CO2 levels are not only contributing to global warming but also ocean acidification (OA). Both eutrophication and OA have serious implications for calcium carbonate production and dissolution among calcifying organisms. In particular, benthic foraminifera precipitate the most soluble form of mineral calcium carbonate (high-Mg calcite), potentially making them more sensitive to dissolution. In this study, a manipulative orthogonal two-factor experiment was conducted to test the effects of dissolved inorganic nutrients and OA on the growth, respiration and photophysiology of the large photosymbiont-bearing benthic foraminifer, Marginopora rossi. This study found the growth rate of M. rossi was inhibited by the interaction of eutrophication and acidification. The relationship between M. rossi and its photosymbionts became destabilized due to the photosymbiont's release from nutrient limitation in the nitrate-enriched treatment, as shown by an increase in zooxanthellae cells per host surface area. Foraminifers from the OA treatments had an increased amount of Chl a per cell, suggesting a greater potential to harvest light energy, however, there was no net benefit to the foraminifer growth. Overall, this study demonstrates that the impacts of OA and eutrophication are dose dependent and interactive. This research indicates an OA threshold at pH 7.6, alone or in combination with eutrophication, will lead to a decline in M. rossi calcification. The decline in foraminifera calcification associated with pollution and OA will have broad ecological implications across their ubiquitous range and suggests that without mitigation it could have serious implications for the future of coral reefs.

Data compilation of ESOP

The work in this sub-project of ESOP focuses on the advective and convective transforma-tion of water masses in the Greenland Sea and its neighbouring areas. It includes observational work on the sub-mesoscale and analysis of hydrographic data up to the gyre-scale. Observations of active convective plumes were made with a towed chain equipped with up to 80 CTD sensors, giving a horizontal and vertical resolution of the hydrographic fields of a few metres. The observed scales of the penetrative convective plumes compare well with those given by theory. On the mesoscale the structure of homogeneous eddies formed as a result of deep convection was observed and the associated mixing and renewal of the intermediate layers quantified. The relative importance and efficiency of thermal and haline penetrative convection in relation to the surface boundary conditions (heat and salt fluxes and ice cover) and the ambient stratification are studied using the multi year time series of hydro-graphic data in the central Greenland Sea. The modification of the water column of the Greenland Sea gyre through advection from and mixing with water at its rim is assessed on longer time scales. The relative contributions are quantified using modern water mass analysis methods based on inverse techniques. Likewise the convective renewal and the spreading of the Arctic Intermediate Water from its formation area is quantified. The aim is to budget the heat and salt content of the water column, in particular of the low salinity surface layer, and to relate its seasonal and interannual variability to the lateral fluxes and the fluxes at the air-sea-ice interface. This will allow to estimate residence times for the different layers of the Greenland Sea gyre, a quantity important for the description of the Polar Ocean carbon cycle.

Chemical composition and solubility of ocean phosphatized rocks in seawater

In order to elucidate possibility of limestone phosphatization during contact with seawater two sets of experiments were carried out: that of solubility of natural phosphates in seawater and that of deposition of phosphorus onto calcareous phase. Concentration of phosphorus in seawater used for solubility experiments varied from 39 to 338 µ/l, temperature was 5.5-17.5°C and pH 7.8-7.9. The lowest solubility was characteristic of ancient crystallized samples. The deposition experiments showed that in case when concentration of dissolved phosphate in seawater reaches 3 mg/l it might be sorbed on solid CaCO3 phase without forming its own mineral. The latter is able to form rapidly but only if magnesium is not present in solution. In magnesium-free water calcium phosphates precipitate when concentration of dissolved phosphorus is higher than 0.9-1.2 mg/l. These results show that phosphatization of limestones in marine environment takes place during their contact with pore water but not with marine bottom water.

Description of the fossil manganese nodules found in the Oligocene clay deposits of Moravia, Brno area, Czech Republic

In the green Oligocene clay of Krizanovice (former Krzyzanowicz) the author found numerous black nodules. In the 3-4 centimeter thick black crust of a particular specimen the concentration in MnO2 is evaluated at 46.6% MnO2. The determination was done using the Volhard's method (precipitation of Fe by ZnO and titration with KMnO4). Only the dissoleved part in HCL was analysed. The non soluble residue was essentially a silica precipitate in the form of many gray flakes. The specific gravity of the crust was evaluated at 3.8. In the internal yellow core the amount of manganese is about 2.39% MnO2. Due to the light color it is judged to probably be in the form of Mn2O3.

Geochemistry of nodules from a young seamount

Manganese nodules made of radiating rods of well crystallized birnessite were sampled at 8 degree 481.2'N, 103 degree 53.8W, 1875 m below sea level by a dredge that also collected hyaloclastite and basaltic talus. The nodule field is on the floor of a caldera within a young tholeiitic seamount and was discovered and photographed during a deep-two survey. It is interpreted as a brecciated hydrothermal deposit, crystallized from an amorphous manganese oxide precipitate that formed when seawater-based hydrothermal fluids mixed with oxidized seawater. The nodules and surrounding igneous rocks have subsequently been encrusted with hydrogenous ferromanganese oxides.

(Table 1) Mean sizes of Hydrobia ulvae juveniles in the littoral zone of the Chernaya Inlet (Kandalaksha Bay, White Sea) in July-September 1995

Based on observations and experiments carried out within the White Sea silty-sandy littoral zone in 1994-1997 data on biology of development and behavior of Hydrobia ulvae juveniles over water column and in sediments were obtained. Hydrobiid juveniles 0.125-0.150 mm in size appear in plankton during the second half of June and in two to three weeks they precipitate on sediments reaching 0.300-0.350 mm in size. Specific biological features of the White Sea hydrobiids are a short reproductive period and a short period of juvenile growth related to long under-ice time and decelerated warming of shallow waters. Distribution of juvenile individuals of H. ulvae is primarily determined by hydrodynamics and microtopography of the littoral zone. Redistribution of the juveniles permanently takes place, since all size groups of the juveniles are equally subjected to migration. During the first few weeks after settling mortality of juvenile mudsnails is 85%.