Annotated record and spectrochemical analyses of Mn nodules from Georgia Strait, British Columbia obtained during CNAV Laymore in 1970

A study of the distribution, dispersal and composition of surficial sediments in the Strait of Georgia, B.C., has resulted in the understanding of basic sedimentologic conditions within this area. The Strait of Georgia is: a long, narrow, semi-enclosed basin with a restricted circulation and a single, main, sediment source. The Fraser. River supplies practically all the sediment now being deposited in the Strait of Georgia, the bulk of it during the spring and summer freshet. This river is building a delta into the Strait from the east side near the south end. Ridges of Pleistocene deposits within the Strait and Pleistocene material around the margins, like bedrock exposures, provide local sources of sediment of only minor importance. Rivers and streams other than the Fraser contribute insignificant quantities of sediment to the Strait. Sandy sediments are concentrated in the vicinity of the delta, and in the area to the south and southeast. Mean grain size decreases from the delta toward the northwest along the axis of the Strait, and basinwards from the margins. Silts and clays are deposited in deep water west and north of the delta front, and in deep basins northwest of the delta. Poorly sorted sediments containing a gravel component are located near tidal passes, on the Vancouver Island shelf area, on ridge tops within the Strait, and with sandy sediments at the southeastern end of the study area. The Pleistocene ridges are areas of non-deposition, having at most a thin veneer of modern mud on their crests and upper flanks. The southeastern end of the study area contains a thick wedge of shandy sediment which appears to be part of an earlier delta of the Fraser River. Evidence suggests that it is now a site of active submarine erosion. Sediments throughout the Strait are compositionally extremely similar, with-Pleistocene deposits of the Fraser River drainage basin providing the principal, heterogeneous source. Gravels and coarse sands are composed primarily of lithic fragments, dominantly of dioritic to granodloritlc composition. Sand fractions exhibit increasing simplicity of mineralogy with decreasing grain-size. Quartz, felspar, amphibole and fine-grained lithic fragments are the dominant constituents of the finer sand grades. Coarse and medium silt fractions have compositions similar to the fine sands. Fine silts show an increase in abundance of phyllosilicate material, a feature even more evident in the clay-size fractions on Montmorillonite, illite, chlorite, quartz and feldspar are the main minerals in the coarse clay fraction, with minor mixed-layer clays and kaolinite. The fine clay fraction is dominated by montmorillonite, with lesser amounts of illite and chlorite. The sediments have high base-exchange capacities, related to a considerable content of montmorillonite. Magnesium is present in exchange positions in greater quantity in Georgia Strait sediments than in sediments from the Fraser River, indicating a preferential uptake of this element in the marine environment. Manganese nodules collected from two localities in the Strait imply slow sediment accumulation rates at these sites. Sedimentation rates on and close to the delta, and in the deep basins to the northwest, are high.

Benthic and substrate cover data derived from a time series of photo-transect surveys for the Eastern Banks, Moreton Bay Australia, 2004-2015

This paper describes seagrass species and percentage cover point-based field data sets derived from georeferenced photo transects. Annually or biannually over a ten year period (2004-2015) data sets were collected using 30-50 transects, 500-800 m in length distributed across a 142 km**2 shallow, clear water seagrass habitat, the Eastern Banks, Moreton Bay, Australia. Each of the eight data sets include seagrass property information derived from approximately 3000 georeferenced, downward looking photographs captured at 2-4 m intervals along the transects. Photographs were manually interpreted to estimate seagrass species composition and percentage cover (Coral Point Count excel; CPCe). Understanding seagrass biology, ecology and dynamics for scientific and management purposes requires point-based data on species composition and cover. This data set, and the methods used to derive it are a globally unique example for seagrass ecological applications. It provides the basis for multiple further studies at this site, regional to global comparative studies, and, for the design of similar monitoring programs elsewhere.

(Table 1) Lithium contents and isotopic composition in sediments from DSDP Holes 64-477 and 64-477A

Lithium isotopic compositions of hydrothermally altered sediments of Deep Sea Drilling Project (DSDP) site 477/477A, as well as high temperature vent fluids of the Guaymas Basin, have been determined to gain an understanding of lithium exchange during fluid-sediment interaction at this sediment-covered spreading center. Unaltered turbidite of the basin has a d6Li value of -10%, 5-7% heavier than fresh oceanic basalts. Contact metamorphism induced by a shallow sill intrusion results in a decrease of the lithium content of the adjacent sediments and a lighter isotopic value (-8%). Below the sill, sediments altered by a deep-seated hydrothermal system show strong depletions in lithium, while lithium isotopic compositions vary greatly, ranging from -11 to +1%. The shift to lighter composition is the result of preferential retention of the lighter isotope in recrystallized phases after destruction of the primary minerals. The complexity of the isotope profile is attributed to inhomogeneity in mineral composition, the tortuous pathway of fluids and the temperature effect on isotopic fractionation. The range of lithium concentration and d6Li values for the vent fluids sampled in 1982 and 1985 overlaps with that of the sediment-free mid-ocean ridge systems. The lack of a distinct expression of sediment input is explained in terms of a flow-through system with continuous water recharge. The observations on the natural system agree well with the results of laboratory hydrothermal experiments. The experimental study demonstrates the importance of temperature, pressure, water/rock ratio, substrate composition and reaction time on the lithium isotopic composition of the reacted fluid. High temperature authigenic phases do not seem to constitute an important sink for lithium and sediments of a hydrothermal system such as Guaymas are a source of lithium to the ocean. The ready mobility of lithium in the sediment under elevated temperature and pressure conditions also has important implications for lithium cycling in subduction zones.

(Table 3, page 373) Chemical composition of manganese nodules from the Komahashi-Daini Seamount in the Northern Philippine Sea

Petrological, mineralogical and chemical investigations of marine manganese nodules from the West Pacific revealed the intimate relation between the chemical and mineral compositions and the remarkable preferential partitioning of metal elements in the ferromanganese minerals. The microscopic observations of textures of manganese nodules tell the growth history of manganese nodules and the formation conditions of ferromanganese minerals. Chemical compositions of nodules from Komahashi-Daini Seamount are very similar to those of the nodules from marginal banks and seamounts. Compositional variations in the bulk composition of nodules collected from the same dredge haul are considerably small, suggesting the similarity of the growth history of individual nodules, although the contents of metal elements vary remarkably from layer to layer in a single nodule.

Benthic and substrate cover data derived from photo-transect surveys in Lizard Island Reef conducted on December 10-15, 2011

Underwater georeferenced photo-transect surveys were conducted on December 10-15, 2011 at various sections of the reef at Lizard Island, Great Barrier Reef. For this survey a snorkeler or diver swam over the bottom while taking photos of the benthos at a set height using a standard digital camera and towing a GPS in a surface float which logged the track every five seconds. A standard digital compact camera was placed in an underwater housing and fitted with a 16 mm lens which provided a 1.0 m x 1.0 m footprint, at 0.5 m height above the benthos. Horizontal distance between photos was estimated by three fin kicks of the survey diver/snorkeler, which corresponded to a surface distance of approximately 2.0 - 4.0 m. The GPS was placed in a dry-bag and logged the position as it floated at the surface while being towed by the photographer. A total of 5,735 benthic photos were taken. A floating GPS setup connected to the swimmer/diver by a line enabled recording of coordinates of each benthic photo (Roelfsema 2009). Approximation of coordinates of each benthic photo was conducted based on the photo timestamp and GPS coordinate time stamp, using GPS Photo Link Software (www.geospatialexperts.com). Coordinates of each photo were interpolated by finding the GPS coordinates that were logged at a set time before and after the photo was captured. Benthic or substrate cover data was derived from each photo by randomly placing 24 points over each image using the Coral Point Count for Microsoft Excel program (Kohler and Gill, 2006). Each point was then assigned to 1 of 78 cover types, which represented the benthic feature beneath it. Benthic cover composition summary of each photo scores was generated automatically using CPCE program. The resulting benthic cover data of each photo was linked to GPS coordinates, saved as an ArcMap point shapefile, and projected to Universal Transverse Mercator WGS84 Zone 55 South.

Benthic and substrate cover data derived from photo-transect surveys in Lizard Island, Great Barrier Reef conducted on October 3-7, 2012

Underwater georeferenced photo-transect surveys were conducted on October 3-7, 2012 at various sections of the reef and lagoon at Lizard Island, Great Barrier Reef. For this survey a snorkeler swam while taking photos of the benthos at a set distance from the benthos using a standard digital camera and towing a GPS in a surface float which logged the track every five seconds. A Canon G12 digital camera was placed in a Canon underwater housing and photos were taken at 1 m height above the benthos. Horizontal distance between photos was estimated by three fin kicks of the survey snorkeler, which corresponded to a surface distance of approximately 2.0 - 4.0 m. The GPS was placed in a dry bag and logged the position at the surface while being towed by the photographer (Roelfsema, 2009). A total of 1,265 benthic photos were taken. Approximation of coordinates of each benthic photo was conducted based on the photo timestamp and GPS coordinate time stamp, using GPS Photo Link Software (www.geospatialexperts.com). Coordinates of each photo were interpolated by finding the GPS coordinates that were logged at a set time before and after the photo was captured. Benthic or substrate cover data was derived from each photo by randomly placing 24 points over each image using the Coral Point Count for Microsoft Excel program (Kohler and Gill, 2006). Each point was then assigned to 1 of 79 cover types, which represented the benthic feature beneath it. Benthic cover composition summary of each photo scores was generated automatically using CPCE program. The resulting benthic cover data of each photo was linked to GPS coordinates, saved as an ArcMap point shapefile, and projected to Universal Transverse Mercator WGS84 Zone 55 South.

Observation of manganese nodules and crusts recovered during the CHAIN 115 cruise from Nov 1973 until June 1974 in the Atlantic Ocean

Investigations of piston cores from the Vema Channel and lower flanks of the Rio Grande Rise suggest the presence of episodic flow of deep and bottom water during the Late Pleistocene. Cores from below the present-day foraminiferal lysocline (at ~4000 m) contain an incomplete depositional record consisting of Mn nodules and encrustations, hemipelagic clay, displaced high-latitude diatoms, and poorly preserved heterogeneous microfossil assemblages. Cores from the depth range between 2900 m and 4000 m contain an essentially complete Late Pleistocene record, and consist of well-defined carbonate dissolution cycles with periodicities of ~100,000 years. Low carbonate content and increased dissolution correspond to glacial episodes, as interpreted by oxygen isotopic analysis of bulk foraminiferal assemblages. The absence of diagnostic high-latitude indicators (Antarctic diatoms) within the dissolution cyclss, however, suggests that AABW may not have extended to significantly shallower elevations on the lower flanks of the Rio Grande Rise during the Late Pleistocene. Therefore episodic AABW flow may not necessarily be the mechanism responsible for producing these cyclic events. This interpretation is also supported by the presence of an apparently complete Brunhes depositional record in the same cores, suggesting current velocities insufficient for significant erosion. Fluctuations in the properties and flow characteristics of another water mass, such as NADW, may be involved. The geologic evidence in core-top samples near the present-day AABW/NADW transition zone is consistent with either of two possible interpretations of the upper limit of AABW on the east flank of the channel. The foraminiferal lysocline, at ~4000 m, is near the top of the benthic thermocline and nepheloid layer, and may therefore correspond to the upper limit of relatively corrosive AABW. On the other hand, the carbonate compensation depth (CDD) at ~4250 m, which corresponds to the maximum gradient in the benthic thermocline, is characterized by rapid deposition of relatively fine-grained sediment. Such a zone of convergence and preferential sediment accumulation would be expected near the level of no motion in the AABW/NADW transition zone as a consequence of Ekman-layer veering of the mean velocity vector in the bottom boundary layer. It is possible that both of these interpretations are in part correct. The "level of no motion'' may in fact correspond to the CCD, while at the same time relatively corrosive water of Antarctic origin may mix with overlying NADW and therefore elevate the foraminifera] lysocline to depths above the level of no motion. Closely spaced observations of the hydrography and flow characteristics within the benthic thermocline will be required in order to use sediment parameters as more precise indicators of paleo-circulation.