ALBERT

Description: Volcanic ash layers, which represent the products of volcanic activity within the ocean basins, are common in sedimentary cores taken near Cobb Seamount and on the actively spreading Gorda and Juan de Fuca Ridges. Petrographic and chemical analyses of the glass shards from these deposits have revealed that they are unaltered and are as chemically representative of local volcanic events as are the glassy margins of fresh pillow basalts recovered from the same areas. The presence of unhydrated glass shards in samples as old as 3.8 my is in direct conflict with published hydration rates of both terrestrial and submarine volcanic glasses. A study of a sequence of ash layers from Cobb Seamount, which spans in time much of the Seamount's history, indicates that the volcanic products from Cobb Seamount have had alkaline affinities and that its eruptions have been becoming progressively enriched in Al2O3. Recent experimental petrological evidence and the data on the chemical compositions of Cobb Seamount and the adjacent Juan de Fuca Ridge magmas are in agreement with the hypothesis that magmas are being generated at progressively greater depths beneath Cobb Seamount as it migrates away from the Juan de Fuca Ridge.

Description: Nine semipurified diets containing protein/energy ratios that ranged from 73 to 162 mg protein/kilocalorie were fed to young rainbow trout for 18 weeks. A casein-gelatin (70–30) mixture and herring oil were each fed at three levels in a factorial type of experiment. Each of the casein-gelatin levels (36, 44 and 53%) was fed at each of the fat levels (8, 16 and 24%). Cornstarch was added at the expense of the casein-gelatin mix to adjust dietary protein levels. Caloric intake regulated feed consumption; and except for diets low in both fat and protein, no significant differences in weight gains were noted, although feed and energy conversions were markedly influenced. Higher protein/calorie ratios were positively correlated with liver size, level of liver sugars, percentage body fat, percentage body protein, and negatively correlated with percentage liver lipids, size of gastrointestinal tract and gain/gram ingested protein. These correlations were observed for similar protein/calorie ratios regardless of the dietary levels of protein and lipid.

Description: Four palaeogeographical reconstructions are presented for the southern Cape covering the period Late Permian to Late Cretaceous. This time spans the commencement to an advanced stage of breakup of Gondwanaland, during which the area moved from a mid-continental, high latitude, to an ocean-dominated, middle latitude position. These movements can be traced in facies changes and erosional cycles associated with the rift between West Gondwana and Antarctica (proto southwest Indian Ocean) and the later rift between South America and Africa (proto southeast Atlantic Ocean).

Description: The Agulhas Bank, which forms the continental margin on the southern tip of Africa, consists of a thick Meso-Cainozoic sedimentary sequence (up to 6.2 km) resting on and behind pre-Mesozoic continental acoustic basement. The stratigraphy of this sequence is outlined and its history and facies variations mentioned where they are known. Refraction seismic velocity and bottom sample data indicate a basic three-fold subdivision of the Mesozoic sequence, which can be correlated with the onshore succession in the Algoa Basin. It is separated by a major hiatus from the Cainozoic sediments, which consist of a Palaeogene and Neogene sequence subdivided by another well-defined level of erosion. Various formations within the Cainozoic are defined and named. An outline of the bathymetry of the eastern Agulhas Bank is also given.

Description: Typical results of continuous temperature-salinity measurements from stations west of Gibraltar are presented. Special features of the structure of the Mediterranean Water in this area in relation to the corresponding turbulent mixing and salt-fingering process are discussed: the two maxima in the vertical profiles, the variation in time of small-scale phenomena, and the step-like structure at the lower boundary of the Mediterranean Water.

Description: Two thousand and twenty well-characterized coral specimens from 17 localities have been analyzed for Sr. Seventy-three genera and subgenera, mostly hermatypic scleractinians, are represented. For some genera, specimens living in surface reef environments are compared with those from 18.3 m depths on the same reefs. Growth rates for some species have also been measured at these depths at one of the sampling sites. Skeletal strontium for a given genus decreases with increasing water temperature, a relationship which previously eluded detection. Aragonite deposited by corals living on the reef at a depth of 18.3 m contains more strontium than the skeletal aragonite of the same coral genera from shallow-water, surface environments. Quantitative treatment of the data for Acropora, one of the most abundant and widely distributed of the reef-building corals, suggests that the observed strontium variations may reflect variations in the rate of skeletal calcification, rather than direct dependence upon temperature or water depth. There is evidence for ‘species effects’, apparently unrelated to growth rate differences, in that certain coral genera are consistently enriched or depleted in skeletal strontium content relative to other genera living in the same reef environments under identical ambient conditions. Temperature, salinity, water depth, seawater composition, and/or other such parameters may in part determine the levels of trace element concentration in carbonates deposited by corals and other marine invertebrates, but it would appear that these variables more directly affect physiological processes which in turn control skeletal chemistry.

Description: Surface area measurements as well as organic carbon, nitrogen and phosphorus analyses on various grain size fractions of carbonate mud samples confirm that in natural environments of carbonate deposition, surface sorption processes take place which are similar to those described earlier for dissolved organics and artificially suspended calcite particles in both seawater and synthetic solutions. The specific surface area of the sediment increases from 1.8m2/g for the coarse-grained fraction to 12.5 m2/g for the fine material; likewise organic carbon, nitrogen and phosphorus increase with increasing surface area so that there are 1.20 mg C, 0.175 mg N and 0.06–0.20 mg P associated with every square meter of carbonate surface irrespective of the mineralogy of the sediment particles. It appears that the organic matter in these sediments is similar in composition, structure and quantity to the organic layers produced in sorption experiments. With their apparently defined structure and ubiquitous nature, these layers could determine the mineralogy and orientation of submarine carbonate cement or could even be a prerequisite to calcification in general.