ALBERT

Description: In Moreton Bay, Queensland, the catch obtained using monofilament polyamide (PA) otter trawl-nets with multifilament polyethylene (PE) cod ends was compared with that obtained using multifilament PE trawl-nets of identical mesh opening (38 mm). Monofilament PA otter trawl-nets retained fewer small prawns ( 〈 24 mm carapace length) than conventional multifilament PE nets, but both nets caught similar quantities of larger prawns ( 〉 24 mm carapace length). The higher retention rate of small prawns by multifilament PE gear was reflected in the greater catch weights of Peraeus plebejus, Metapenaeus bennettae and Metapenaeopsis novaeguineae in those nets. Catch weights of larger prawn species such as Penaeus esculentus and Metapenaeus endeavouri did not differ between nets. Winter whiting (Sillago maculata) and squid (Loligo spp.) were trawled in similar abundance in both nets, although the monofilament retained fewer squid 〈 50 mm mantle length. More marketable ( 〉 15 cm carapace width) sand crabs (Portunus pelagicus) were caught in the monofilament net. There was not significant difference in the trash (noncommercial component) weight caught in both nets. Over the range of towing speeds tested (1.7–2.3 kn), use of monofilament nets significantly reduced total gear drag.

Description: The nature of subsidence near the ridge crest of the intermediate and fast spreading mid-ocean ridges of the Indian and Pacific Oceans is investigated using surface-ship bathymetry and magnetics profiles. The ridge can be divided into discrete sections, apparently bounded by distinct structural features such as major fracture zones, in which bathymetry plotted against crustal age forms a well-defined envelope with a width roughly the amplitude of the local bathymetry. The averaged bathymetry in all of the regions studied follows closely a square root of age subsidence curve which in most regions has a subsidence coefficient, C1, in the range of 340–390 m Myr−1/2. The best fitting subsidence curve, however, never reproduces the amplitude of the axial topographic high. The most notable region displaying unusual behaviour is the East Pacific Rise between 9°S and 22°S. In this region, the western flank of the ridge is subsiding at 200–225 m Myr−1/2 while the eastern flank is subsiding at ‘normal’ rates of 350–400 m Myr−1/2. Other anomalous areas include the region between the Easter Island hot spot and the Chile Rise triple junction in which the ridge crest is shallow and which is subsiding at rates of about 290 m Myr−1/2, and the region east of the Australia-Antarctic Discordance in which the northern flank is subsiding at 440 m Myr−1/2. This area may also be subsiding asymmetrically although there is not much data from the southern flank. The asymmetric subsidence in the 9°S-22°S region of the East Pacific Rise begins immediately at the ridge crest and the low subsidence rates on the west flank continue to at least 12 Myr old crust. Oligocene-aged crust on the western flank is subsiding at more normal rates, but is 500 m shallow with respect both to the world-wide average and to the conjugate crust on the eastern flank. The simplest model to explain these observations is that the western flank is underlain by a hotter mantle, perhaps as the result of upwelling resulting from the large-scale return circulation from the trenches. Depending on the depth of compensation, the observed asymmetry could result from a lateral temperature gradient of 0.05–0.10°C km−1 and a total lateral temperature variation of under 100°C.

Description: A survey of the ecology of the octopus Eledone cirrhosa in Scottish waters is compiled from structured interviews with fishermen, records of occurrence in traps (for lobster and crab), and a research vessel survey. This species is widespread and common throughout the inshore waters covered by fishing activity (shoreline- 140 m) on bottom types ranging through rock, stones, sand and mud. It is caught in all months of the year but is especially common inshore in the summer (July-September) and further offshore on trawling grounds in October-December. The octopus is a normal and regular predator of large Crustacea (Hotnarus, Nephrops, Cancer) caught in commercial traps but gut contents yield little identifiable dietary remains.

Description: ln the past, analysis of habitat choice by marine nekton has been hampered by limited access to its environment. We suggest a method to facilitate study of habitat choice, using data gathered from videotapes. The aims of this study were (a) to identify members of a particular nekton assemblage, and (b) to identify environmental variables important to the assemblage as a whole. Data on species and environmental variables came from Videotapes of a sandy-bottom shelf area (60m depth) in the Gulf of Mexico off Pensacola, Florida, taken by a remote-controlled submersible travelling along defined transects. We analyzed these Videotapes to derive Information on habitat use of several species of fishes and large invertebrates. We divided the transects into sections which were homo· geneaus for bottom type and algal coverage, and in each section measured habitat variables and abundances of the most common and reliably identifiable species of demersal nekton. Factor analysis of species' means for environmental variables identified patterns of habitat use among these species. The analysis identified these patterns by generating axes that represented environmental gradients. The patterns of habitat use by these species related to their preferences for different amounts of three·dimensional structure, algae, and infaunal and epifaunal organisms. We compared species distributions and habitat distributions on these axes to find which environmental gradients were of most importance in habitat selection by these species. We found that more species selected habitats on the basis of particular amounts of structure, fewer selected on the basis of algal coverage and infaunal organisms. Only one species seemed to select habitats on the basis of types or abundances of epifaunal organisms. Thus, amount of three-dimensional structure seemed an important variable to the sandy·bottom assemblage overall, followed by amount of algal coverage and types of infaunal organisms.

Description: We compared the diets of 4 CO-occurring species of penguin at sub-Antarctic Marion Island in light of mechanlsn~s thought to result in dietary differentiation. Calculation of overlap indices and correspondence analyses indicated a clear separation in the diets of the 3 penguin genera but considerable similarity between the congeneric species pair The pelagic foraging king penguin Aptenodytes patagonicus consumed mainly myctophid fish, whereas the near-to offshore foraging macaroni penguin Eudyptes chrysolophus and rockhopper penguin E. chrysocome both consumed predominantly small pelagic crustaceans, although in different proportions. The inshore foraging gentoo penguin Pygoscelis papua fed largely on benthic nototheniid fish. Although king penguins rarely take small prey, differences in diet cannot be accounted for solely on the basis of prey size selection. Different diving capabilities may have some role in dietary differentiation, however, we consider prey availability in the apparently distinct feeding zones to explain most of the differences in the diets of the 4 species of penguins at Marion Island. The daily population food requirements of the respective penguin species at the Prince Edward Islands (comprising Marion and Prince Edward islands) increased with Increasing species foraging range. The mainly benthic nature of the prey in the inshore area, compared with the more easily replenished pelagic food stocks, probably explains the differences in food ava11abi.lity that sustain the greater food demands of the large populations of pelagic and offshore foragers.

Description: Sperm whales Physeter macrocephalus were observed off the Galapagos Islands between late February and April 1985, a year of cool sea-surface temperatures (SST), and January to June 1987, an 'El Nino' year of warm SST Distribu- tlon, abundance and diet of sperm whales were similar in both years. However, in 1987 they appeared to have a lower feeding success, as ind~cated by a reduced rate of observing faeces, and dived to shallower depths. Excretion rates were negatively correlated with sea-surface temperatures.

Description: Experimental fishing for flying squid (Ommastrephes bartrami) was continued in 1987 from both a Japanese vessel and a Canadian vessel in northeastern Pacific Ocean waters off the coast of British Columbia. Average squid catch rates (383 kg km-1) for the Japanese vessel was the highest obtained over the 3-yr experimental study period. Pomfret and blue shark remained the major by catch species, but as in 1986, marine mammal catch rate increased substantially over the previous year's level. A total of 90 marine mammals were caught by the two vessels combined, and while the average length of net required to catch one mammal was similar for the Canadian vessel over the past two years, catch rate increased (i.e., the average net length required to catch one mammal decreased) for the Japanese vessel in 1987.

Description: The cuttlefish ingests much skeleton from the crustaceans and fish it preys upon. The skeletal pieces are relatively large and their dimensions bear a close relationship to the length of the buccal mass and diameter of the oesophagus. The structures of the buccal mass are instrumental in the breakdown of prey and orientation of long pieces of skeleton to ensure their entry into the oesophagus. Many pieces of skeletal material present in the stomach contents still have attached muscles, showing that there is little, or no, external digestion. Skeletal material may be important for long-term maintenance of young Sepia in captivity.

Description: Thirteen types of octopodid paralarvae are recognized from Hawaiian waters, although the adults of only seven species (three are undescribed) are currently known from this area. The most common 11 paralarval types are described; five types can be identified with known adults. Stage II paralarvae differ from Stage I paralarvae by the presence of sucker buds on their arms. The number of suckers in Stage I paralarvae is characteristic for a species, as are their chromatophore patterns. Hatchlings have a high density of integumental pores containing secretory granules that may produce a mucous “drogue” to assist in offshore transport.

Description: Food samples from 27 Buller’s mollymawks Diomedea bulleri from the New Zealand region showed that cephalopods were, by frequency of occurrence and by mass, their preferred food. Fish, crustaceans, and tunicates, in decreasing order of importance, also were taken. Seventeen species of Cephalopoda were identified by their beaks, with 78.5% of individuals belonging to the Ommastrephidae (77% Nototodarus spp.) and 10% to the Histioteuthidae. The diet was compared with that of four other small species of Diomedea, and found to be similar to that of D. chrysostoma, D. irrorata, and D. cauta, but different from that of D. melanophris, whose preferred food is euphausiids. Squid-fishing operations around New Zealand may come into competition with Buller’s mollymawk.

Description: The squid Nototodarus gouldi (McCoy, 1888) was caught by bottom trawl in Port Phillip Bay, Australia in February 1985. The squid accumulates in its digestive gland high levels of trace metals, with up to 100 μg Cd g-1 dry tissue, 1 200 μg g-1 copper and 1 500 μg g-1 zinc and up to 24 Bq g-1 of the naturally occurring radionuclide polonium-210. The molecular binding of these elements in six squid was investigated using column chromatography. Two poorly resolved copper peaks were associated with proteins of average molecular weights of 11 500 and 18 000. The two squid containing the highest levels of cadmium in their digestive glands (44 and 88 μg g-1) had cadmium associated with a peak of molecular weight intermediate between the copper-binding peaks, but this peak was absent from squid containing lower levels of cadmium. Zinc was associated with ligands of less than 1 500 molecular weight. The 210Po eluted with proteins of greater than 70 000 molecular weight, and there was no evidence of binding to low molecular weight proteins. Different mechanisms appear to be involved in the binding and control of the four elements.

Description: Methods of collecting, analysing and presenting data on the diets of seabirds are reviewed, with consideration of methods employed in diet studies of other organisms. Killing of birds continues to be the primary source of dietary information from birds at sea but is no longer necessary for studies on land. Stomach pumps obtain complete stomach evacuation with low mortality. Stomach samples should be examined as soon as possible after collection, to avoid biases caused by preservation. Presentation of data is best done by rank-order to facilitate comparison between studies, but as many data should be provided as possible. Future work on diets will be strengthened through knowledge of digestion rates and nutritional values of food.

Description: An overview is given of the natural systems of the North Sea: water-circulation, topography and geology of the sea floor, sediment transport, influx of trace constituents (nutrients, trace metals, organic compounds), biological systems and their interrelations. The effects of pollution and other human activities are discussed as well as the difficulties in assessing them where they are obscured by natural changes.

Description: AGU considers only original scientific contributions that have not been accepted or published elsewhere and are not under consideration by another publisher. A contribution is considered previously published if its data and conclusions are offered for sale or are generally available in other ways to the public. Regardless of the original publication medium, including print, magnetic tape, or microform, such contributions are not eligible for republication in AGU journals or books.

Description: The early breakup of western Pangea has been investigated by mapping the pattern of fracture zones and distribution of seismic reflectors within the sedimentary cover of the Atlantic between the Cape Verde Islands and the equator. Two distinct sets of transverse oceanic lineaments are present, separated by the Guinea Fracture Zone near lat 10°N. Lineaments to the north are associated with the formation of the central Atlantic in the Late Jurassic and Early Cretaceous; those in the south relate to the Cretaceous opening of the South Atlantic. The Guinea Fracture Zone is thus the conjugate of the Jurassic transform boundary under peninsular Florida, which linked the Atlantic with the Gulf of Mexico. The distribution of dated seismic reflectors suggests that deposition of deep-water sediments was confined to the region north of the Guinea transform until Aptian time, when the Sierra Leone Basin began to open. The latter started to widen at least 15 m.y. after the initiation of the Cape Basin off southwest Africa, an age difference that can be explained if a short-lived plate boundary developed in either Africa or South America during the Early Cretaceous. Neither the trends of the equatorial fracture zones nor the seismic stratigraphy supports the existence of a predrift gap between west Africa and Brazil.

Description: Characteristics of water masses were analyzed to study the Kuroshio intrusion into the sea southwest of Taiwan. Hydrographic data were obtained from CTD (conductivity, temperature, and depth) casts during two cruises in May and August 1986. In May, remnants of water intruding from the Kuroshio were found on the continental slope south of the Penghu Channel. By August, these were replaced by water from the South China Sea. During this period, water from the Kuroshio also appeared near the southern tip of Taiwan. The intrusion current reached a depth of at least 500 m and was probably part of a cyclonic circulation in the northern South China Sea. The results support the hypothesis of a seasonal pattern of the intrusion process: intrusion of water from the Kuroshio begins in late summer, intensifies in winter, and ceases by late spring when South China Sea waters again enter this region.

Description: A geological and geophysical study of active submarine volcanoes offshore of Epi Island and between Epi and Efate Islands, New Hebrides Arc, has delineated five large, mainly submerged, calderas over a 90-km length of the arc. These vary in diameter from 15 to 30 km, and the two northern calderas have active post-caldera basaltic cones. Karua volcano lies on the submerged northern rim of the caldera northwest of Tongoa, and has periodically erupted medium-K20 basaltic andesite in this century. Submarine cones Epia, Epib, and Epic are aligned east-west and spaced 3.5 km apart on the rim of the northernmost caldera. Rocks dredged from these cones include basalt, dacite, and cognate gabbroic inclusions with magmatic affinities similar to those of the Karua lavas. A pronounced bimodal Si02 content is noted for the large caldera volcanoes in the New Hebrides and other oceanic arcs. This bimodality has important implications for physical processes of magma differentiation within arc-volcano magma chambers. The bulk of the uppermost level of the surficial (and seafloor) dacite pumiceous pyroclastics in the area of northeast Epi and Tongoa was derived from cataclysmic eruptions of more than one of the now largely submerged calderas.

Description: Kurzfassung eines Vortrages zum Polartag in Bremerhaven am 23.2.1988

Description: Taken from a lecture given at the Fisheries Centennial Celebration (1985) by William F. Royce

Description: The active tectonic setting of the southwest coast of Canada and the Pacific northwest coast of the United states is dominated by the Cascadia subduction zone. The zone can be divided into four segments where oceanic lithosphere is converging independently with the North American plate: the Winona and the Explorer segments in the north, the larger Juan de Fuca segment that extends into both Canada and the United States, and the Gorda segment in the south. The oceanic lithosphere entering the Cascadia subduction zone in all segments is extremely young, less than 10 Ma. Of the other six zones around the Pacific where young (〈 20 Ma) lithosphere is being subducted, five have had major thrust earthquakes (megathrust events) on the subduction interface in historic time. An estimation based on potential area of rupture gives maximum possible earthquake magnitudes along the Cascadia subducting margin of 8.2 for the Winona segment, 8.5 for the Explorer segment, 9.1 for the Juan de Fuca segment, and 8.3 for the South Gorda segment. Repeat times for maximum earthquakes, based on the ratios of seismic slip to total slip observed in other subduction zones, are predicted to be up to several hundred years for each segment, well beyond recorded history of the west coast, which began about 1800. Thus the lack of historical seismicity information provides a few constraints on the assessment of the seismic potential of the subduction zone.

Description: Combined Sr-Nd-Pb isotope and trace-element data for St Helena are interpreted in terms of changing thermal and chemical fluxes impinging on and interacting with the base of the lithosphere over a period of 6 Ma. The data reveal the existence of two geochemically distinct components in the St Helena source region: (i) a HIMU (high U/Pb) component which has extremely radiogenic lead isotopes (206Pb/204Pb 〉20.8) with 87Sr/86Sr and 143Nd/144Nd ratios displaced below the mantle array; (ii) a component with less radiogenic lead and strontium isotopic compositions and more radiogenic neodymium compositions. Coupled trace-element and isotope variations are evident during the activity of each volcano. During shield development an increase in incompatible-trace-element enrichment occurs. This is coupled to a decrease in 143Nd/144Nd, whilst strontium and lead isotope ratios become progressively more radiogenic with time. The time-dependent variations are thought to be consistent with high-level processes occurring at the base of, or within, the lithosphere. A decrease in the signature of the depleted component with time is shown to be the result of a decreasing thermal flux acting on the base of the lithosphere. As a consequence the degree of partial melting of the depleted component (which may reside in the lithosphere or asthenosphere) is reduced, increasing the signature of the HIMU component in the erupted magmas.

Description: Temperature and sensory indices of human responsee to the thermal environment are often expressed in terms of the known in a controlled laboratory environment, as a standard. The three rational indices of this type to be considered are (1) ASHARE's Standard Effective Temperature (SET*) Index, defined as the equivalent dry bulb temperature of an isothermal environment at 50% RH in wich a subject, while wearing clothing standardized for activity concerned, would have the same heat stress (skin temperature Tsk) and thermoregulatory strain (skin wettedness, w) as in the actual test environment; (2) Fanger's Predicted Mean Vote (PMV) Index, defined in terms of the heat load that would be required to restore a state of "Comfort" and evaluated by his Comfort Equation; and (3) Winslow's Skin Wettedness Index of "Thermal Discomfort" (DISC) defined in terms of the fraction of the body surface, wet with perspiration, required to regulate body temperature by evaporative cooling. The classic difference between PMV and DISC as predictors of warm discomfort occurs at very high and very low humidity but both lead to essentially the same judgment at average humidities (40-60% RH or 1-2 kPa). A new index PMV* is proposed for any dry or humid environment by simply replacing operative temperature To in Fanger's Comfort Equation with SET*. The use of PMV* as a sensor of heat stress and strain, is illustrated for typical HVAC situations and with a new Comfort-Humidity psychometric chart for indoor environments.

Description: The importance of feeding pattern is well documented in fish (Jenkins & Green, 1977; Simenstad & Cailliet, 1986) but there are not many reported studies in cephalopods. Feeding patterns, as defined by Jenkins & Green (1977) have been studied, to our knowledge, only in Todarodes pacificus (Okiyama, 1965), Loligo pealei (Vovk, 1972), Loligo opalescens (Karpov & Cailliet, 1978), Illex illecebrosus (Amaratunga et ah, 1979; Amaratunga, 1980) and Nototodarus gouldi (O'Sullivan & Cullen, 1983). Boyle (1983) dealt with aspects of feeding in several cephalopod species but not specifically with feeding pattern. Aspects of feeding in Sepia officinalis have been reviewed by Nixon (1987). The present work describes the daily feeding pattern in Sepia officinalis from data collected in the field.

Description: A culture of juvenile Sepia officinalis L. was kept during summer 1985 in the aquaria of the “Station Marine”, Wimereux, France. During the first four months of juvenile development, oxygen consumption under increasing hypoxia was measured with a closed respirometer. The experiments revealed a high regulatory capacity of juvenile S. officinalis. The critical oxygen concentrations were calculated and their ontogenetical evolution was studied. The critical oxygen concentration increased with increasing development. A linear relationship emerged between the critical oxygen concentration and the logarithm of the wet weight [COc (mg O2 l-1)=-0.393+0.893×log10(Ww)]. The decreasing regulatory capacity of growing S. officinalis is most probably related to adaptations to a changing ecological environment during development. Another possibility is a physiological change, most probably related to the shift from embryonic to adult hemocyanin.

Description: The diets of five breeding seabird species were investigated on Adélie Land in January–February 1982. Stomach contents of Adélie penguins, Pygoscelis adeliae, were sampled by a water off-loading method and of Procellariiformes by spontaneous regurgitation. Diet compositions by mass were: Adélie penguin (79% euphausiid, 18% fish, 3% squid); Cape pigeon, Daption capense, (64% euphausiid, 29% fish, 7% carrion); Antarctic fulmar, Fulmarus glacialoides, (64% euphausiid, 20% carrion, 16% fish); snow petrel, Pagodroma nivea, (95% fish, 2% euphausiid, 1% carrion) and Wilson's stormpetrel, Oceanites oceanicus, (39% fish, 37% euphausiid, 13% carrion, 12% various crustaceans). The present Adélie penguin diet is consistent with those reported in other studies, given our knowledge of geographical variation in food availability. Differences in the diets of fulmarine petrels appear to relate to differences in foraging areas. The snow petrel is a fish-eating bird associated with pack-ice. Cape pigeon and Antarctic fulmar are mainly krill-eaters and we infer segregation along a neritic/oceanic gradient because of the importance of the neritic Euphausia crystallorophias in the former and the oceanic E. superba in the latter.

Description: Squid regurgitated by Greyheaded and Yellownosed Albatrosses at the Prince Edward Islands were predominantly two onychoteuthid species, Kondakovia longimana and Moroteuthis knipovitchi. Both squid are characteristic of cold, Antarctic waters and may have been caught south of the Antarctic Convergence, some 350 km to the south of the breeding station. Both albatross species regurgitated similar squid (by species and size), and these squid were similar to those found in previous studies of the diet of Wandering, Sooty and Lightmantled Sooty Albatrosses at the Prince Edward Islands

Description: The carbon isotope signal in deep-sea sediments reflects a mix of (1) global changes in the rates of exchange of the ocean's carbon reservoir with biosphere, soil, and sediments, (2) global and regional changes in surface water productivity, (3) internal shifts in water-mass structure and circulation (basin-basin fractionation, oxygen minimum development), and (4) organism-specific fractionation effects due to changes in micro-habitat and/or ontogenic fractionation (»vital effects«). Additional complications arise from differential preservation. It is impossible to entirely isolate these various factors. As a rule of thumb, long period signals that are parallel for planktonic and benthic data reflect external (global) fractionation patterns, whilst short-period signals are more likely tied to internal patterns (water-mass fractionation). The various approaches to interpretation are illustrated with three case studies: the Glacial-Holocene transition, the Messinian Carbon Shift, and the Miocene Monterey Excursion.

Description: Se describen los resultados del estudio ecolögico de las especies mäs abundantes pertenecientes a las familias Ommastrephidae y Loliginidae del A tlä n tic o Sudoeste. Las investigaciones fueron (levadas a cabo por cienti'ficos sovieticos entre 1981 y 1987. Se presta especial atencion a Ille x argentinus. Se presenta informaciön sobre la frecuencia biotöpica, ciclos de vida, duraciön de vida, biologia reproductiva y fauna de los paräsitos. Asimismo se discute el problema de su estructura intraespeci'fica.

Description: Faecal material of leopard, crabeater and elephant seals was collected from the vicinity of Davis station, Antarctica. Very few identifiable remains were found in elephant seal droppings. Fish remains, mainly of Pleuragramma antarcticum, were found in both leopard and crabeater seal droppings. The mysid Antarctomysis maxima was also found in crabeater seal droppings and amphipods and decapod crustaceans in leopard seal droppings.

Description: A collection of 130 specimens of Sepiola (ligulata, robusta, rondeletii, intermedia), 115 Rondeletiola minor, 90 Sepietta ( obscura, neglecta) and more abundant samples of S. oweniana obtained by trawl fishing in the Ligurian Sea are briefly illustrated in terms of depth distribution, sex ratio and maturity stages.

Description: New description of Euprymana stenodactyla (Grant, 1833) and description of Euprymana hoylei sp. nov. (= E. stenodactyla Hoyle, 1904 and Voss, 1954, 1963 (non Grant, 1833)

Description: What is the relationship between volcanic eruptions and climate change? More than 200 years after the connection was first proposed, it remains a thorny question. This article provides a brief historical overview of the problem and a review of the various data bases used in evaluating volcanic events and associated climatic change. We use the term “climate” to describe changes in the atmosphere over wide regions for periods of several months and longer. We use “weather” to describe shorter-term, variable atmospheric fluctuations experienced over more restricted areas. We appraise the present state of knowledge and highlight some pitfalls involved in using available information. Cautiously, we suggest future avenues for study, including the possibility of “volcanic winters,” or severe eruption-induced coolings.

Description: The Stratigraphie record from both deep-sea and shallow-water depositional environments Indicates that during late Aptian through Cenomanian time (1) global climates were considerably warmer than at present; (2) latitudinal gradients of atmospheric and oceanic temperatures were considerably less than at present; (3) rates of accumulation of organic matter of both marine and terrestrial origin were as high as or higher than during any other interval in the Mesozoic or Cenozoic; (4) the rate and volume of accumulation of CaC02 in the deep sea were reduced in response to a marked shoaling of the carbonate compensation depth; (5) seafloor spreading rates were somewhat more rapid than at any other time in the Cretaceous or Cenozoic; (6) off-ridge volcanism was intense and widespread, particularly in the ancestral Pacific Ocean basin; and (7) sea level was relatively high, forming widespread areas of shallow shelf seas. A marked increase in the rate of C02 outgassing due to volcanic activity between about 110 and 70 m.y. ago may have resulted in a buildup of atmospheric C02. A significant fraction of this atmospheric C02 may have been reduced by an increase in the production and burial of terrestrial organic carbon. Some excess C02 may have been consumed by marine algal photosynthesis, but marine productivity apparently was low during the Aptian-Albian relative to terrestrial productivity. Terrestrial productivity also may have been stimulated by increased rainfall that resulted from a warm global climate and increased marine transgression as well as by the higher C02.

Description: Santorini volcanic field has had 12 major (1–10 km3 or more of magma), and numerous minor, explosive eruptions over the last ~ 200 ka. Deposits from these eruptions (Thera Pyroclastic Formation) are well exposed in caldera-wall successions up to 200 m thick. Each of the major eruptions began with a pumice-fall phase, and most culminated with emplacement of pyroclastic flows. Pyroclastic flows of at least six eruptions deposited proximal lag deposits exposed widely in the caldera wall. The lag deposits include coarse-grained lithic breccias (andesitic to rhyodacitic eruptions) and spatter agglomerates (andesitic eruptions only). Facies associations between lithic breccia, spatter agglomerate, and ignimbrite from the same eruption can be very complex. For some eruptions, lag deposits provide the only evidence for pyroclastic flows, because most of the ignimbrite is buried on the lower flanks of Santorini or under the sea. At least eight eruptions tapped compositionally heterogeneous magma chambers, producing deposits with a range of zoning patterns and compositional gaps. Three eruptions display a silicic–silicic + mafic–silicic zoning not previously reported. Four eruptions vented large volumes of dacitic or rhyodacitic pumice, and may account for 90% or more of all silicic magma discharged from Santorini. The Thera Pyroclastic Formation and coeval lavas record two major mafic-to-silicic cycles of Santorini volcanism. Each cycle commenced with explosive eruptions of andesite or dacite, accompanied by construction of composite shields and stratocones, and culminated in a pair of major dacitic or rhyodacitic eruptions. Sequences of scoria and ash deposits occur between most of the twelve major members and record repeated stratocone or shield construction following a large explosive eruption. Volcanism at Santorini has focussed on a deep NE–SW basement fracture, which has acted as a pathway for magma ascent. At least four major explosive eruptions began at a vent complex on this fracture. Composite volcanoes constructed north of the fracture were dissected by at least three caldera-collapse events associated with the pyroclastic eruptions. Southern Santorini consists of pryoclastic ejecta draped over a pre-volcanic island and a ridge of early- to mid-Pleistocene volcanics. The southern half of the present-day caldera basin is a long-lived, essentially non-volcanic, depression, defined by topographic highs to the south and east, but deepened by subsidence associated with the main northern caldera complex, and is probably not a separate caldera.

Description: The antarctic krill Euphausia superba forms abundant, well-organized schools in the waters off the Antarctic Peninsula. Mean avian density is 2.6 times greater in waters where krill schools are present than in waters without krill schools. Seabird density is a good predictor of the presence of krill. Seabird density did not correlate with krill density or krill school depth. Disoriented krill routinely were observed swimming near the surface above submerged schools, providing potential prey for surface-feeding birds. Responses of seabird species to the distribution of krill schools varied. The small to medium-size procellariiform species were the best indicators of krill schools; large procellariiforms and coastal species were poor indicators. Pygoscelis penguins occurred at high densities only in the presence of krill schools. These responses are consistent with the constraints imposed by the metabolic requirements and reproductive strategies of each of these groups. Krill schools were detected near the sea surface throughout the day. Correlations between seabird density and the presence of krill during daylight hours suggest that diurnal foraging is important to the seabirds of this region.

Description: Magnesium chloride is an effective anaesthetic and narcotizing agent for cephalopod molluscs. Individuals belonging to five genera (decapod and octopod) were anaesthetized and subsequently revived at temperatures ranging from 13 to 22°C. At no stage of anaesthesia does MgCl2 appear to cause any trauma. There is evidence that MgCl2 acts centrally on the nervous system to induce anaesthesia. This salt, cheap, readily available and convenient to use, is recommended over urethane or ethanol as a suitable anaesthetic or narcotic for use with cephalopods.

Description: Between September 1987 and February 1988, Antarctic fur seals Arctocephalus gazella (Peters) at Heard Island fed mainly on fish with an average 95.2% of scats in monthly collections containing fish remains. Pelagic myctophids constituted more than 50% of fish taken by fur seals at the beginning of the summer season and again at the end when there was an influx of non-breeding male seals. During the middle period from October to December, fish from the surrounding shelf area comprised the bulk of the diet. These included various benthic nototheniid species, the bentho-pelagic ice fish Champsocephalus gunnari Lönnberg and skate (Bathyraja spp.), the latter being found in over 60% of scats in October and November. The population of Antarctic fur seals at Heard Island is increasing at about the same rate as at South Georgia. There the increase is thought to be due to the high availability of krill E. superba, but in the present study no euphausiid remains were found, so the increasing population at Heard Island has been supported on a diet of fish. Whether this population increase can be sustained in future on a diet of fish is arguable. Trial fishing around Heard Island indicates that one of the major dietary items of the seals (C. gunnari) is of probable commercial importance and therefore any plans for the establishment of a fishery on Heard Island grounds must be considered in this light.

Description: Metabolism not only affects the acid–base status of an animal by means of proton stoichiometries but, by feedback regulation, acid–base parameters (pH, , bicarbonate) influence metabolic rates and the pathways used. This leads to a significant contribution of metabolism to acid–base regulation under both aerobic and anaerobic conditions. The relationship between amino acid metabolism, urea synthesis, and excretion is discussed as an example important for steady-state metabolic acid–base regulation during aerobiosis. Generally, acid–base relevant metabolism may be regulated through the effect of acid–base disturbances on hormonal mediation, allosteric modulation of enzyme proteins, pH optima, and the levels of substrates or products, some of these being acid–base relevant substances like bicarbonate, CO2, inorganic phosphate, and NH3. During functional or environmental anaerobiosis the same relationships prevail. Metabolic proton accumulation is counterbalanced by phosphagen depletion and ammonia accumulation in adenylate catabolism. In addition, in integrated control of metabolic and acid–base status, long-term (mitochondrial) anaerobiosis leads to reductions in metabolic rate and increased removal of acidic groups. The importance of metabolic processes in acid–base methodology is discussed in terms of traditional concepts and recent developments.

Description: 40Ar/39Ar age spectrum analysis of phengite separates from Naxos, part of the Attic Cycladic Metamorphic Belt in Greece, indicates that cooling following high-pressure, low- to medium-temperature metamorphism, M1, occurred about 50 Ma ago. Phengite has 40Ar* gradients that suggest that part of the scatter observed in conventional K–Ar ages was caused by diffusion of radiogenic argon from the minerals during a younger metamorphism, M2. In central Naxos, this metamorphism (M2) has overprinted the original mineral assemblages completely, and is associated with development of a thermal dome. Excellent 40Ar/39Ar plateaus at 15.0 ± 0.1 Ma, 11.8 ± 0.1 Ma, and 11.4 ± 0.1 Ma, obtained on hornblende, muscovite and biotite, respectively, from the migmatite zone, indicate that relatively rapid cooling followed the M2 event, and that no significant thermal overprinting occurred subsequent to M2. Toward lower M2 metamorphic grade, 40Ar/39Ar plateau ages of hornblendes increase to 19.8 ± 0.1 Ma; concomitantly the proportion of excess 40Ar in the spectra increases as well. We propose that the peak of M2 metamorphism occurred beween 15.0 and 19.8 Ma ago. K–Ar ages of biotites from a granodiorite on the west coast are indistinguishable from those found in the metamorphic complex, and hornblende K–Ar ages from the same samples are in the range 12.1–13.6 Ma. As the latter ages are somewhat younger than most ages obtained from the metamorphic complex, intrusion of the granodiorite most likely followed the peak of the M2 metamorphism. The metamorphic evolution of Naxos is consistent with rapid crustal thickening during the Cretaceous or early Tertiary, causing conditions at which supracrustal rocks experienced pressures in the range 900–1500 MPa. Transition to normal crustal thicknesses ended the M1 metamorphism about 50 Ma ago. The M2 metamorphism and granodiorite intrusion occurred during a period of heat input into the crust, possibly related to the migration of the Hellenic volcanic ar°C in a southerly direction through the area.

Description: Magnetic lineation mapping in the western central Pacific has revealed a pair of opposite-sensed, fanned lineation patterns that define the accretionary boundaries of the fossil Magellan microplate. This tectonic synthesis results from extensive magnetic mapping of two new lineation patterns over a large area and extended mapping of previously identified lineations. The entire evolutionary history of the Magellan microplate is well constrained to a 9-m.y. period in the Early Cretaceous by synchronous spreading patterns and associated geologic data. During this period the microplate grew and evolved as a generally rectangular structure to a final size of 700 km×600 km with spreading centers on two opposing sides and transform faults on the other two sides. The lifetime and size of the Magellan microplate are somewhat longer and larger, respectively, than presently active microplates on the East Pacific Rise. However, these modern structures are still evolving and growing, and the tectonic behavior of the modern and Cretaceous systems appears to be similar. Study of both active and fossilized microplates should provide additional insights on their common tectonic histories. In particular, we show that the Magellan Trough spreading center behaved as an asymmetric accretionary plate boundary that can be described with two separate poles of motion very close to this spreading center during much of its history. The Magellan Trough spreading center then failed as a result of a larger ridge reorganization at the triple junction of the Pacific, Farallon, and Phoenix plates at Ml0N time. Microplate activity ceased when the microplate became welded to the Pacific plate at M9 time.

Description: The Fifteen Twenty Fracture Zone offsets the Mid-Altantic Ridge over 195 km in a sinistral sense. It was surveyed in 1982 between 30°W and 60°, i.e. from anomaly 34 on the African plate to anomaly 34 on the American plate where it disappears as the Barracuda Ridge into the Caribbean subduction zone. The fossil limbs of the Fifteen Twenty Fracture Zone show a remarkable symmetry to both sides of the Mid-Atlantic Ridge. Barracuda Ridge appears to have undergone a later deformation. The sections of the Fifteen Twenty FZ between 49°W and 54°W to the west of the Mid-Atlantic Ridge and between 37.5°W and 42.5°W to the east do not exhibit the normal characteristics of a fracture zone but have elongate and extremely narrow transverse ridges (dykes) along the fracture zone axis. The present transform domain shows signs of leaking. This is interpreted as a result of a fairly recent (about 7 Ma bp) change in spreading direction of the area. This change in spreading direction seems to have affected only the area south of 17°50′N. It may have resulted from a northward migration of the plate boundary between the North American and South American plates and the coming into existence of a triple point near 16°N. From this reconstruction, the location of the differential pole between the North American and South American plates is 16°N/53.5°W. This location leads to increasing compression from 53.5° to 60°W, affecting the Barracuda Ridge and Trough with a N–S shortening of about 16 km in 7 Ma. From 53.5° to 45°W, N–S extension occurred (about 19 km near the Mid-Atlantic Ridge), which led to the origin of the volcano–tectonic complex of Researcher Ridge, Researcher Trough and Royal Trough to the west of the Mid-Atlantic Ridge.

Description: Der Einfluß lateralen Stresses auf die mechanische Diagenese von marinen Sedimenten kann mithilfe sedimentphysikalischer Daten quantifiziert werden. Beispielhaft wurde dies anhand von Daten aus dem Deep Sea Drilling Project (DSDP) und Ocean Drilling Project (ODP) für den Akkretionskeil des Barbados Ridge Complex durchgeführt. Die Untersuchung erfolgte in drei Schritten. (1) In einer statistischen Untersuchung der umfangreichen sedimentologischen und sedimentphysikalischen Datenbank des DSDP wurden tief enabhängige Funktionen der mechanischen Diagenese für eine Reihe von lithologischen Standardtypen definiert. Diese, als Referenzgröße zur Quantifizierung der tektonischen KonsoHdation in einem rezenten Akkretionskeil benötigten Funktionen, wurden in erster Linie für pelitische und psammitische Sedimente mit geringen Karbonatgehalten entwickelt. Zwei verschiedene Verfahren zur Auswahl von entsprechenden Datensätzen werden beschrieben und die Ergebnisse der statistischen Untersuchung mit den in der Literatur beschriebenen Funktionen verglichen. (2) Die entwickelten Typfunktionen wurden bei der Durchführung eines palinspastischen Rekonstruktionsverfahrens benutzt, mit dem die Entwicklung sedimentphysikalischer Parameter während der initialen Deformationsphase in rezenten Akkretionssystemen modelliert werden konnte. Diese Untersuchung basierte im wesentlichen auf sedimentphysikalischen Daten der DSDP- und ODP-Legs 78A und J 10 (Barbados Ridge Komplex, Kleine Antillen). Durch palinspastische Entzerrung der imbrikierten Schuppung und stratigraphische Rekonstruktion akkretierter "thrust slices" im untersuchten Bereich, entsprechender Relozierung der zugehörigen sedimentphysikalischen Daten und dekompaktive Anpassung an die rekonstruierte Position konnte ein synthetisches prä-akkretionäres Profil der ursprünglichen Porosität rechnerisch modelliert werden. (3) Der Vergleich dieses synthetischen Porositäts-Tiefen-Profils mit charakteristischen Referenzprofilen aus undeformierten Sequenzen unmittelbar vor der Deformationsf ront zeigt eine systematische, lithologisch bestimmte Divergenz. Durch Überarbeitung des Rekonstruktionsverfahrens mithilfe von Stress-PorositätsBeziehungen konnte der relative und absolute Einfluß der lateralen Stresskomponente auf die Konsolidation hemipelagischer Sedimente in diesem Teil des konvergenten Plattenrandes quantifiziert werden.

Description: Petrographic and petrochemical study of igneous rocks of the Sierra Leone rise indicate that trachytes, trachyandesites, trachybasalts, and tuffs derived from them occur there. The absolute age of the rocks as indicated by K-Ar method is 36-43 million years. Alkalic igneous activity is associated with the activity of bot spots.

Description: One method of testing the concept of sequence stratigraphy is to compare it to Quaternary sediments in which chronology, stratigraphic relations, and facies geometry are more clearly understood than in older rocks. Rapid deposition rates during Quaternary glacial-eustatic cycles in large deltaic depocenters generate sequences comparable to those in the ancient stratigraphic record. In the northern Gulf of Mexico, the late Wisconsinan-Holocene Mississippi River has deposited a Type 1 sequence that includes lowstand, transgressive, and high-stand systems tracts. Characteristics of modern Mississippi River sedimentary environments support the methodology used in sequence analysis, but the short time taken for sequence generation here raises important questions about sequence time scales, correlation, and driving mechanisms.

Description: The magnetic anomaly pattern over the Red Sea can be modeled as a continuous system of sea-floor spreading from the early Miocene to the present by using a time-varying process filter. The half spreading rate is approximately 1 cm/yr (0.4 in./yr) since initial rifting. The parameters that determine the process filter and development of the transition zone are the intrusion parameter (a measure of the dispersion of feeder dikes or horizontal strain about the rift axis), a flow parameter (a measure of the average flow width), and the effusion parameter (a measure of the volcanic effusion and thickness of layer 2). Application of a time-varying process filter appears to be a powerful tool in analyzing magnetic anomalies over passive continental margins. We estimate the flow parameter to be 2.7 km (1.7 mi) and the intrusion parameter to be 7.5 km (4.7 mi) at early rifting. These values suggest that a wide distribution of axial dikes or horizontal strain is the dominant factor in forming the magnetic anomaly pattern. Reduction in the width of the intrusion parameter and the effusion rate as rifting proceeded resulted in focusing of the strain, thinning of layer 2, and formation of the Red Sea deeps. The interpretation of the anomaly pattern implies that basement within the main trough of the Red Sea is composed of a thick accumulation of volcanic sills and flows deposited during early rifting. Extrusion of the lavas occurred over a wide (up to 60 km or 37 mi) zone of strain distributed about the rift axis. The development of this thickened zone of igneous crust is the second of three successive stages of extension for the Red Sea basin. These stages are as follows. (1) An initial stage of crustal stretching or listric faulting in the Oligocene accompanied by probable regional uplift. (2) A period of high volcanic effusion accompanied by the emplacement of stratoid basalts. The stratoid volcanics form overlapping flows and sills with intercalated sediments within the main trough. The spreading center narrowed from the early Miocene to the present. (3) Steady-state sea-floor spreading from Pliocene to present south of a transitional zone near 22°S. The process filter width derived from the magnetic anomaly pattern at earliest rifting can be used to estimate the lateral variation from igneous to continental-type crust in a statistical sense. Our data suggest that the transition from 100% continental crust to 100% igneous or stratoid-type crust should occur within an interval of approximately 32 km (20 mi). Our modeling suggests that phase 2, or the stratoid phase, began about the time of anomaly 5C or chron C5C approximately 16 Ma. This age is compatible with geologic estimates of the initial rifting at the late Oligocene to early Miocene (Coleman, 1974; Gass, 1977). The opening rate for Africa-Arabia plate motion has remained relatively constant since early rifting although the African margin appears to be accreting faster than the Arabian plate.

Description: RECENT advances in 40Ar/39Ar dating1,2 have made it possible to date individual K-feldspar grains from Pleistocene tephra, a capability that greatly improves the reliability and temporal resolving power of the method. Here we apply these new techniques to the dating of a phonolite tephra from the East Eifel volcanic field in West Germany, which is sandwiched between loess and palaeosol (alfisol) deposits, and which was therefore erupted during the transition from a glacial to an interglacial period. Our age estimate for this transition is 215±4 kyr (1 σ), which has important implications for the marine δ18O timescale and for models of global climate change during the Pleistocene. The results show that single-grain dating can detect and compensate for the large quantities of xenocrystic contaminants which are found in many tephra deposits. This technique could be used to date the tephra layers found in marine sediment cores and the results could greatly enhance the reliability of the marine δ18O timescale for more rigorous Fourier analysis testing of the Milankovitch hypothesis.

Description: A seismic refraction profile recorded along the geologic strike of the Chugach Mountains in southern Alaska shows three upper crustal high-velocity layers (6.9, 7.2, and 7.6 km/s) and a unique pattern of strongly focussed echelon arrivals to a distance of 225 km. The group velocity of the ensemble of echelon arrivals is 6.4 km/s. Modeling of this profile with the reflectivity method reveals that the echelon pattern is due to peg-leg multiples generated from with a low-velocity zone between the second and third upper crustal high-velocity layers. The third high-velocity layer (7.6 km/s) is underlain at 18 km depth by a pronounced low-velocity zone that produces a seismic shadow wherein zone peg-leg multiples are seen as echelon arrivals. The interpretation of these echelon arrivals as multiples supersedes an earlier interpretation which attributed them to successive primary reflections arising from alternating high- and low-velocity layers. Synthetic seismogram modeling indicates that a low-velocity zone with transitional upper and lower boundaries generates peg-leg multiples as effectively as one with sharp boundaries. No PmP or Pn arrivals from the subducting oceanic Moho at 30 km depth beneath the western part of the line are observed on the long-offset (90-225 km) data. This may be due to a lower crustal waveguide whose top is the high-velocity (7.6 km/s) layer and whose base is the Moho. A deep (~54 km) reflector is not affected by the waveguide and has been identified in the data. Although peg-leg multiples have been interpreted on some long-range refraction profiles that sound to upper mantle depths, the Chugach Mountains profile is one of the few crustal refraction profiles where peg-leg multiples are clearly observed. This study indicates that multiple and converted phases may be more important in seismic refraction/wide-angle reflection profiles than previously recognized.