ALBERT

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: 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: 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: 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: 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: 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: 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: From 1325 specimens of S. officinalis, 612 males and 713 females, caught in 572 trawl hauls from April 1982 to February 1987 in the ria de Vigo, it is inferred that this species lives and spawns throughout the ria, including the inner part where there are large fluctuations in salinity (20-35.5 %). It is distributed preferentially along the shores of the central and outer basins of the ria. The highest frequency of apparition occurs in autumn. The main spawning season covers spring and summer, but winter spawning was also observed. Females larger than 120 mm ML were more abundant than males of these size. Males are more precocious than females. Mature and immature animals of both sexes were found in the population the year round.

Description: The flying behavior of neon flying squid was observed at 8 different locations in the subtropical region between long. 160°E and 172°W along lat. 37°N (surface temperature: 17-24°C), on board the R/V Omi-Maru in the period from July to August, 1984. Roughly 10-300 squids (estimated mantle length: 14-18cm) flew a distance of 10-20m at a height of 1-2 m above the sea surface in the same direction both by day and by night. The form of squid in flight closely resembled that of purpleback flying squid. Judging from these results, it is beleived that the smaller individuals under about 18cm in mantle length of neon flying squid live mainly near the surface of the sea, by day and night, and that they have a gliding-type flying behavior like flying fish, mainly to escape from their enemies.

Description: Stratigraphic units representing high-sea-level events in Britain, northern France, Belgium, The Netherlands, northwest Germany, Denmark, Sweden and Norway, are correlated by aminostratigraphy (D (alloisoleucine)/L (isoleucine) (ratios from Littorina littorea, Macoma balthica, Macoma calcarea and Arctica islandica). The eight sea-level events recognized are modelled with the constraints provided by the oxygenisotope signal of sea-level variability, and available geochronometric age determinations for calibrating the D/L data. These data are used to constrain the timing and extent of glaciations in the British Isles and Scandinavia during the Middle and Late Pleistocene.

Description: Résumé Le présent travail est consacré à l'étude de la maturation sexuelle d'une cohorte née en 1977 d'Eledone cirrosa dans le golfe du Lion en Méditerranée. Plusieurs indices de maturation tel que le rapport gonado-somatique, l'indice de Guerra pour les deux sexes, l'indice du pénis pour les mâles ainsi que l'indice de la glande de l'oviducte sont examinés en vue de choisir le meilleur moyen d'exprimer numériquement les différents stades de maturation de l'espèce pour des études de populations. Dans ce but, l'on suggère d'utiliser l'indice de Guerra pour les mâles et l'indice de la glande de l'oviducte pour les femelles pour lesquels trois phases de maturation (immature, intermédiaire et mature) peuvent être différenciées. Les clefs numériques correspondant à trois phases de maturation avec les indications des observations du développement de la gonade sont établies. Abstract The present paper deals with the sexual maturation of Eledone cirrosa studied on a cohort born in 1977 in the Gulf of Lions, Mediterranean Sea. Several maturity indices such as gonadosomatic index and Guerra's index for both sexes, penis index for male and oviducal gland index for female were examined in order to choose the best method to express numerically different maturity stages of the species for population studies. Guerra's index for male and oviducal gland index for female were defined as appropriate indices to distinguish three different maturity stages (immature, intermediate and mature) in Eledone cirrosa. A key for determination of three maturation stages by the numerical values of the maturity indices chosen with observations of the development of genital organ was established.

Description: Reproductive maturity and morphometric characteristics were compared for two samples of the octopus Eledone cirrhosa from geographically widely separated sites, Aberdeen, Scotland (320) and Banyuls, France (285).At the two locations the collecting period was synchronized (13 months) and laboratory procedures standardized. In both samples the sex ratio was strongly biased to females, which were about twice the body size of the males. Both sexes were significantly larger in the northern population. Analysis of a limited selection of morphometric characters (mantle, arms, brain and body weight) showed significant differences, but these were insufficient to confirm any divergence in body shape between the two populations.

Description: The diet of Northern Rockhopper Penguins Eudyptes chrysocome moseleyi breeding on Gough Island, south Atlantic Ocean was studied, during November 1984, 1985 and 1986 by stomach content analysis. Rockhopper Penguins fed chiefly on the euphausiids Thysanoessa gregaria, Euphausia lucens and E. similis. Fish and squid were of minor importance by mass but constituted the largest individual prey items.

Description: Microborings are found in virtually any exposed carbonate substrate in the tropical waters of the Bahamas. Previous investigations of microborers have concluded that substrate type plays little or no role in their distribution. However, our preliminary scanning electron microscope (SEM) study of microboring casts in six common genera of foraminifera from San Salvador island demonstrates that host taxa differ with respect to extent of infestation and location of infestation within the test. We suspect, but can not yet prove, that different assemblages of microboring organisms are also involved. The primary differences exist at the suborder level; members of the Suborder Rotaliina are not as bored as specimens of the Miliolina taken from the same sample. Rotaliids are infested almost exclusively in the outer margin of the test, whereas miliolids vary from taxon to taxon. Differences in infestation at the suborder level may be controlled, at least in part, by the fundamental differences in wall microstructure between the Rotaliina and the Miliolina, and may have important implications for their relative preservation potentials.

Description: New Ireland is dissected by northeasterly and northwesterly-trending normal faults, which have fragmented the island into a series of northeasterly-tilted fault blocks. An exception to this regional pattern is the Weitin Fault Zone, which appears to represent the onshore extension of a ridge-trench transform fault system. Basement in New Ireland is formed by the Eocene(?} to Oligocene Jaulu Volcanics, and the Oligocene to middle Miocene Lemau Intrusive Complex. The basement rocks are unconformably overlain by the Miocene Lelet Limestone and the Lelet's partial lateral equivalents, the Tamiu siltstone and Lossuk River beds. In northwestern New Ireland, the lower Lelet Limestone and Lossuk River beds are succeeded conformably by the middle to late Miocene Lumis River volcanics. To the south, where the Lelet Limestone has a longer age range, the formation is overlain by the late Miocene to early Pliocene Punam Limestone, and the Pliocene to earliest Pleistocene Rataman Formation. The youngest rock units on New Ireland are Pleistocene limestones (Qc) and their lateral equivalent, the Maton Conglomerate. The Jaulu Volcanics and Lemau Intrusive Complex are the products of island arc volcanism associated with subduction along the Manus-Kilinailau Trench. Uplift and erosion of the arc was followed by widespread carbonate platform sedimentation during the early Miocene (Lelet Limestone). At the same time, fine-grained elastic sediment accumulated in adjacent, deep water areas (Tamiu siltstone and Lossuk River beds). Local volcanism, accompanied by marked subsidence, ended carbonate sedimentation in northwestern New Ireland during the middle Miocene. Bathyal pyroclastic and epiclastic sediment accumulated in that area until the late Miocene or early Pliocene (Lumis River volcanics). To the south, carbonate platform sedimentation probably continued unabated until the late Miocene, when rapid regional subsidence drowned the platform. This event appears to have coincided with reversal of the New Ireland portion of the original island arc system. Bathyal pelagic deposition subsequently became established over a wide area (Punam Limestone). Regional volcanism commenced in the early Pliocene, probably in response to subduction along the newly-formed New Britain Trench. During the remainder of the Pliocene, bathyal sedimentation continued as pyroclastic and epiclastic sediment was deposited on submarine fans (Rataman Formation). Rapid regional uplift of the southwestern margin of the New Ireland Basin followed during the early Pleistocene. Coarse-grained terrigenous sediment accumulated against active fault scarps {Maton Conglomerate), while neritic carbonates were deposited nearby {Qc).

Description: In the Middle Miocene, two halotectonic depressions were formed in the German Bight. While the western depression, Helgoland Hole, still exists more or less intact today, the Eastern Depression persisted as a palimpsest structure only through the Pleistocene into the Early Holocene. About 8,000 years B.P., as sea level rose to about -40 m, a small embayment formed east and southeast of Helgoland. It was bounded to the north by the Steingrund ridge which stretched from Eiderstedt Peninsula to the Helgoland platform, so that water circulation in the north-south direction was highly restricted. The Elbe and Weser were deflected to the west to deposit their suspended material and bed load in the Eastern Depression. Before this depression could be completely filled up about 1,500 years B.P., however, the Steingrund ridge was breached with rising sea level, and the modern, basically northsouth current pattern was established. Simultaneously, the filled Eastern Depression (the Mud Area) became progressively more distal, so that sedimentation came to a halt. Today, sediment deposition is largely controlled by anthropogenic activities, in particular by the dumping of dredged fine harbour mud. This material forms a small lenticular body superimposed on the coarser, larger sediment lens of fine sand and silt.

Description: Thirty-nine food samples were collected from Salvin’s prions Pachyptila salvini at sub-Antarctic Marion Island, Prince Edward Islands. The diet was dominated by crustaceans which formed 44,2% of the mass, 99,7% of prey items and occurred in 97,4% of the samples. Amphipods were of particular importance, the most abundant species being Themisto gaudichaudii. There was a marked absence of copepods which are an important element in the diets of both the dove P. desolata and broad-billed prions P. vittata. Prey included fish (41,9% by mass) and cephalopods. The results are compared with published data for dove, Salvin’s and broad-billed prions collected at other islands, and with data from Marion Island for blue petrels Halobaena caerulea. Nege-en-dertig voedselmonsters is van mediumbekwalvisvoels Pachyptila salvini by sub-Antarktiese Marioneiland, Prince Edward-Eilande, versamel. Die dieet is deur skulpdiere oorheers, wat 44,2% van die massa en 99,7% van die prooi-items gevorm het en met ’n frekwensie van 97,4% voorgekom het. Amphipoda was van besondere belang, met Themisto gaudichaudii die belangrikste soort. Daar was ’n merkbare afwesigheid van Copepoda, wat ’n belangrike element in die dieet van duifwalvisvoels P. desolata en breebekwalvisvoels P. vittata is. Prooi-items het vis (41,9% volgens massa) en koppotiges ingesluit. Die resultate word met gepubliseerde data vir duifwalvisvoels, mediumbekwalvisvoels en breebekwalvisvoels wat by ander eilande versamel is, vergelyk asook met data van bloustormvoels Halobaena caerulea wat by Marioneiland versamel is.

Description: The Imperial Cormorant Phalacrocorax atriceps is an inshore foraging, diving seabird (Cooper 1985) distributed throughout the southern hemisphere south of 45°S (Watson 1975). A brief description of the diet of the Imperial Cormorant at Marion Island has been published (Blankley 1981). We present here a more comprehensive report based on food samples collected throughout the year.

Description: A new squid subspecies, Todarodes pacificus pusillus, is described from northern Australian continental shelf and upper slope waters on the basis of morphological differences and apparent geographic isolation from northern hemisphere populations of T. pacificus Steenstrup, 1880. Basic life history information is presented. The subspecies reaches maturity at less than 80 mm mantle length compared with greater than 200 mm ML for T. pacificus from Japanese waters.

Description: Marine geophysical surveys employing Seabeam, multi- and single-channel seismic reflection, gravity and magnetic instruments were conducted at two locations along the continental slope of the Peru Trench during the Seaperc cruise of the R/V “Jean Charcot” in July 1986. These areas are centered around 5°30′S and 9°30′S off the coastal towns of Paita and Chimbote respectively. These data indicate that (1) the continental slope off Peru consists of three distinct morpho-structural domains (from west to east are the lower, middle and upper slopes) instead of just two as previously reported; (2) the middle slope has the characteristics of a zone of tectonic collapse at the front of a gently flexured upper slope; (3) the upper half of the lower slope appears to represent the product of mass wasting; (4) thrusting at the foot of the margin produces a continuous morphologic feature representing a deformation front where the products of mass-wasting are overprinted by a compressional tectonic fabric; (5) a change in the tectonic regime from tensional to compressional occurs at the mid-slope-lower slope boundary, the accretionary prism being restricted to the very base of the lower slope in the Paita area. The Andean margin off Peru is an “extensional active margin” or a “collapsing active margin” developing a subordinated accretionary complex induced by massive collapse of the middle slope area.

Description: The Pacific seafloor is littered with small fragments of lithosphere captured from adjacent plates by past plate boundary reorganizations. One of the clearest examples of such a reorganization is documented in the Mathematician Seamounts region, where a distinctive geomorphology and well-developed magnetic anomalies are present. This reorganization involved a short-lived microplate between the failing Mathematician Ridge and a new propagating spreading center: the East Pacific Rise. It produced a transfer of a fragment of lithosphere from the Farallon to the Pacific plate, and also created a number of landforms and magnetic patterns, within and on the margins of the captured fragment; these make up the Mathematician paleoplate. In many cases, two sides of a microplate are active spreading ridges. A microplate evolves into a paleoplate when dual spreading ceases and full spreading resumes at the prevailing spreading ridge. We define a paleoplate as the area of the seafloor, from the axis of a failed rift to the boundary of resumed, full spreading. It includes a fragment of captured lithosphere and the lithosphere slowly accreted to it during the period of dual spreading, prior to complete abandonment of the failed rift. The Mathematician paleoplate has the following boundaries and components from west to east: the axis of the Mathematician failed rift, the fragment of captured Farallon plate, a complex rift initiation site at the Moctezuma Trough, a zone of slow spreading, and an as yet ill-defined eastern boundary where dual spreading stopped and full spreading resumed. The northern boundary of the paleoplate is the Rivera fracture zone; its southeastern boundary a now-inactive transform fault, the West O'Gorman fracture zone. In this case, as well as in other more poorly documented ones, relict landforms and magnetic patterns are carried on the aging lithosphere, away from the spreading ridge, recording a former geometry.

Description: Methane carbon isotopic composition ranged from −76.9 to −62.6‰ in a tidal freshwater estuary (the White Oak River, North Carolina, United States) with site specific seasonal variations ranging from 6 to 10‰. During warmer months, tidally induced bubble ebullition actively transported this methane to the atmosphere. At two sites, these seasonally varying fluxes ranged from 1.2 ± 0.3 to 1.3 ± 0.3 mol CH4 m−2yr−1 (19.2 to 20.8 g CH4m−2yr−1), with flux-weighted average isotopic compositions at two sites of −66.3 ± 0.4 and −69.5 ± 0.6‰. The carbon isotopic composition of naturally released bubbles was shown to be indistinguishable from the sedimentary methane bubble reservoir at three sites, leading to the conclusion that isotopic fractionation did not occur during the ebullition of methane. The hypothesis was developed that ebullitive methane fluxes are depleted in 13CH4 relative to fluxes transported via molecular diffusion or through plants, as zones of 13C enriching microbial methane oxidation are bypassed.

Description: Petrographical and petrochemical study of the Sierra Leone Rise magmatic rocks. showed that trachytes, trachyandesites, trachybasalts and their tuffs are developed there. The absolute age of the Sierra Leone Rise magmatic rocks as determined by K-Ar method, is 36-43 mln. yrs. Alkaline magmatism is related to the hot spots activity.

Description: Existing information is synthesized and new data presented to describe the flow of near-bottom water from the Weddell Sea into the Scotia Sea and westward through Drake Passage along the continental slope. The water characteristics and currents along the northern margins of the South Sandwich Island Arc are examined. Long-term current measurements in the bottom waters at locations over the outer shelf and slope and along the continental rise show persistent flow from Atlantic to Pacific along isobaths at speeds of 10–20 cm s−1. Three sources for the waters in these currents are identified and discussed. At the deepest levels, Weddell Sea Deep Water enters the Scotia Sea near 40°W through a depression in the South Scotia Arc and then flows westward, constrained by the bottom topography. This cold, fresh, oxygenated bottom water then flows west to enter Drake Passage via a gap in the Shackleton Fracture Zone at the base of the continental slope northwest of Elephant Island. Mid-depth water may flow from the Weddell Sea to the Scotia Sea through the Powell Basin (sill depth approximately 2000 m) located west of South Orkney Island near 48°W. The westward flowing waters along the shelf and upper continental slope, which are denser than those immediately offshore, may be a continuation of the Polar Slope Current from the Weddell Sea or may be derived principally by convection from the shelves of the South Sandwich Island Arc. A vertical section north of Elephant Island shows downslope convection off the shelf, analogous to the observed at many locations around Antartica.

Description: In der Mitte (Atlantik) oder am Rand (Pazifik) der großen Ozeanbecken wird durch Intrusion und Extrusion basaltischer Magmen ständig neue Ozeankruste gebildet. Diese geodynamischen Prozesse, bei denen mit Abstand die meisten Vulkane auf der Erde entstehen, haben in den letzten Jahren unsere Aufmerksamkeit auf submarine vulkanische Vorgänge gelenkt. Wir haben zwar durch die Ergebnisse der Tauchfahrten der ALVIN und die Bohrungen der GLOMAR CHALLENGER viel über den Aufbau der Ozeankruste gelernt; aber die dreidimensionale Rekonstruktion submariner Vulkane und ihre detaillierte Erforschung sind anhand von Landaufschlüssen erheblich einfacher und aussagekräftiger. Die paläozoischen Vulkanitserien im Lahn-Dillgebiet sind seit Jahrzehnten Gegenstand zahlreicher erdwissenschaftlicher Untersuchungen, überwiegend lagerstättenkundlicher, regionalgeologischer und stratigraphischer Zielrichtung. Petrographisch-vulkanologische Aspekte sind vor allem von HENTSCHEL(1970) behandelt worden. Eine Zusammenfassung der bisherigen Arbeiten im Bereich des Blattes Dillenburg findet sich in LIPPERT et al.(1970).

Description: Continuous current measurements at the 1000 m level were obtained in the central Canary Basin of the northeast Atlantic near 33°N, 22°W for 2398 days. Even with this very long time series no statistically significant mean current could be estimated at that level, because the energetic fluctuations are large compared to the weak mean. In the eddy scale range, i.e. at current fluctuations are scales between 47 and 455 days, a pronounced anisotropy between zonal and meridional components is apparent. For the first time in the subtropical North Atlantic gyre our data allow confirmation of the expected spectral decrease beyond the eddy scale peak in an eastern basin. With respect to future global experiments we wonder if our results from an eastern basin location are representative for the general circulation at mid-ocean sites?

Description: Aquatic animals directly influence the cycling of phosphorus in lakes through feeding and excretion. Traditionally, animals (zooplankton, benthic invertebrates and fish) have been assigned only minor roles in the process of freshwater phosphorus cycling. They were regarded as consumers without much regulating influence. Today there is growing evidence that animals, predators and herbivores, directly or indirectly can control biomass of primary producers and internal cycling of phosphorus. This paper summarizes different mechanisms of transformation and translocation of phosphorus via different groups of organisms.

Description: We examine the diffusive behavior of the flow field in an eddy-resolving, primitive equation circulation model. Analysis of fluid particle trajectories illustrates the transport mechanisms, which are leading to uniform tracer and potential vorticity distributions in the interior of the subtropical thermocline. In contrast to the assumption of weak mixing in recent analytical theories, the numerical model indicates the alternative of tracer and potential vorticity homogenization on isopycnal surfaces taking place in a nonideal fluid with strong, along-isopycnal eddy mixing. The eastern, ventilated portion of the gyre appears to be sufficiently homogeneous to allow the concept of an eddy diffusivity to apply. A break in a random walk behavior of particle statistics occurs after about 100 days when along-flow dispersion sharply increases, indicative of mean shear effects. During the first months of particle spreading, eddy dispersal and mean advection are of similar magnitude. Eddy kinetic energy is of O(60–80 cm2 s−2) in the model thermocline, comparable to the pool of weak eddy intensity found in the eastern parts of the subtropical oceans. Eddy diffusivity in the model thermocline (Kxx = 8 × 107, Kyy = 3 × 107 cm2 s−1) seems to be higher by a factor of about 3 than oceanic values estimated for these area. Below the thermocline, model diffusivity decreases substantially and becomes much more anisotropic, with particle dispersal preferentially in the zonal direction. The strong nonisotropic behavior, prominent also in all other areas of water eddy intensity, appears as the major discrepancy when compared with the observed behavior of SOFAR floats and surface drifters in the ocean.

Description: Replacement dolomitization by seawater has been modeled in order to quantify the Sr-isotope signature in Cenozoic dolomites as a function of precursor mineralogy and 87Sr/86Sr ratio, reaction stoichiometry and 87Sr/86Sr ratio of the dolomitizing fluids. High Sr carbonates, such as aragonite, may introduce a significant precursor memory into an otherwise seawater dominated Sr-isotope signature if small quantities of seawater per unit volume of precursor carbonate are involved. Dolomitization of low Sr carbonates (i.e. low-Mg calcite) are shown to create an isotopic signature indistinguishable from that of the seawater involved in the reaction. Therefore, by comparison with the Sr-isotope evolution curve of seawater, the- 87Sr/86Sr ratios of the dolomites can be used to record the oldest possible age of dolomitization and the youngest age of deposition. The implications for this approach have been applied to data obtained from a dolomitized core from Little Bahama Bank, Bahamas. Two periods of dolomitization are recognized, one in the early Late Miocene involving Middle Miocene or older rocks, and a second one around 2.4 Ma ago affecting early Pliocene carbonates.

Description: The lower Malm (Oxfordian to lower Klmmeridgian) of southern Germany contains rich and diversified dinoflagellate assemblages. In addition to samples collected from surface outcrops the material of KLEMENT (1960) are revised. Lost holotypes are replaced with lectotypes , and if necessary redescribed. Based on morphological observations, the dlnoflagellate cyst genera Acanthaulax, Eplplosphaera und s.vstematophora have been emended. Lithodlnla arcanltabulata n. sp., Scriniodinium bucinatum bucinatum n. sp. n. subsp., Scriniodinium bucinatum labyrinthum n. sp. n. subsp. and Systemstophora varispinosa n. sp. are described as new. In the Upper Jurassie of southern Germany, the occurence of a large part of the dinoflagellate cysts is strongly facies-controlled. As in recent dinoflagellates, their distribution is much less governed by geographical latitude (provincialism) than by other systems (salinity, water depth, chemical composition ot the water mass). In the Upper Jurassic. at least two s ystems could be recognized: (1) marl-limestone alternation (small cycles, Milankovich cycles?) and (2) larger lithological units (Malm Alpha, Beta, Gamma). The "standard-zonatlon of dinoflagellates" published by WOOLLAM & RIDING (1983) for NW- Europe can also be applled in S-Germany. but a few modifications are necessary for ecological reasons. The dinoflagellates allow to correlate the Upper Jurassie of N-Europa and S-Germany independently from ammonites.

Description: The Central Indian Ridge between 21°- 24°S, near the RodriguezT riple Junction, was investigatedb y RV SONNE during the 1983 and 1986 cruises of the GEMINO project (Geothermal Metallogenesis Indian Ocean) for the purpose of locating sites of hydrothermal activity. In response to reconnaissance data of conductive heat flow, sediment cores, and hydrocasts, two intermediate spreading ridge segments at 2l.5°S (area EX,/FX) and 23°S (area JX) were selected for detailed exploration including mapping, sampling and visual seafloor observation. Hydrothermally influenced sediment cores and altered basalts were found in both study areas. Total dissolvable Mn concentrations up to 27.5 nmol/kg and CHa values up to 45.6 nL/L occur within 450 m above bottom in the northern and southern overlapping propagators in area EX/FX. In addition, 63He values up to 18.6% and a potential temperature anomaly (0.01°C) were found. In area JX, maximum concentrations of 36.1 nL/L CHa and 10.7 nmol,/kg total dissolvable Mn in the water column seem to be related to a central neovolcanic ridge close to a ridge-transform intersection. At the eastern flank of this ridge, a significant potential temperature anomaly of 0.04°C was measured. The results obtained in areas EX/FX and JX provide evidence for hydrothermal activity. However, in comparison to the TAG hydrothermal field at the Mid-Atlantic Ridge at 26°N, the data indicate a more restricted and probably lower temperature hydrothermal discharge.

Description: A radiocarbon-calibrated box model for today's ocean suggests that a lag of about 1750 years should exist between the arrival of the midpoint of the deglaciation 18O signal in the deep Atlantic Ocean and its arrival in the deep Pacific Ocean. In order to assess the actual lag, we have carried out accelerator radiocarbon measurements on two cores from the Atlantic Ocean and one core from the Pacific Ocean. Although the results are not definitive, there is a suggestion that the actual time lag was about 1000 years.

Description: In ecological studies, especially in those dealing with energy circulation in nature, determinations of the energy content of organisms are inevitable. Energy determinations are, however, laborious and time-consuming. Average conversion factors based on different species form various areas and seasons may often be a shortcut for overcoming this problem. To establish general energy conversion factors for aquatic invertebrate groups, we used 376 values of J · mg−1 DW and 255 values of J · mg−1 AFDW, representing 308 and 229 species, respectively. The dry-weight-to-energy factors were highly variable both within and between taxonomic groups, e.g.: Porifera, 6.1 J · mg−1 DW; insect larvae, 22.4 J · mg−1 DW (median values). The energy-conversion factors related to AFDW showed a much smaller dispersion with a minimum median value of 19.7 J · mg−1 AFDW (Ascidiacea) and a maximum of 23.8 J · mg−1 AFDW (insect larvae). Within taxonomic groups, the 95% confidence intervals (AFDW) were only a few percent of the median values. The use of energy-conversion factors based on AFDW is preferable due to their lower dispersion. For aquatic macrobenthic invertebrates, a general conversion factor of 23 J · mg−1 AFDW can be used.

Description: Helium data from the waters of the Bransfield Strait, the southern Drake Passage and the northwestern shelf of the Weddell Sea are presented. The 3He profiles from the eastern and central basins of the Bransfield Strait show maxima (δ3He ≈ 7%) below the sill depths that separate the strait from the surrounding open ocean. The 3He excess is interpreted as a local injection of a 3He-rich helium component into the deep waters of the Bransfield Strait from backarc rifting. Tritiogenic 3He and excess 3He from mixing with Circumpolar Deep Water are excluded as possible sources. The estimated 3He/4He ratio of the injected helium component (2.4–5.0 × 10−6) is less than that of pure mantle helium and may contain radiogenic helium from continental crustal material which underlies the Bransfield Strait.

Description: A study of the Cenozoic deep-sea benthic Foraminifera from Deep Sea Drilling Project Sites 208, 289, 305, 357, 360 and 369 shows that Oligocene and post-Oligocene faunas differ little from Recent assemblages, this entire inten•al being characterized by slow and gradual faunal replacements: tlie most important faunal turnover recorded in these cores took place below the Eocene-Oligocene boundary. Within the Oligocene-Pliocene interval, most of the overall foraminiferal changes defined are not correlated between sites : faunal similarities are significantly and consistently greater between the stratigraphic units of the same site, than between coeval stratigrapllic units of different sites; the makeup and relative proportions of foraminiferal assemblages are much more influenced by geographie location and by ecological factors than by their evolutionary history. Enhanced similarities between Sites 208, 289 and 357 (as compared with Sites 305, 360 and 3(i9) during this same period are most probably due to bathymetric differences between the locales involved. The usefulness of deep-sea benthic Foraminifera for biostratigraphic interpretations is strongly restricted by their spotty occurrence, their long time-ranges, and their markedly local qualitative and quantitative character and variations.

Description: Paleoceanographic and stratigraphic methods, based on high-resolution compressional wave (p-wave) velocity measurements, have been applied to the studies of late Quaternary deep-sea carbonates in the western and eastern equatorial Atlantic. The measurements provide sonostratigraphic records in which changes in p-wave velocity parallel the changes from a glacial to an interglacial climate: Maxima in p-wave velocity (greater than 1540 m/s) occur during interglacial oxygen isotope stages 1, 5 and 7. Minima (1490 m/s) occur during glacial oxygen isotope stages 2, 4 and 6. Changes in p-wave velocity parallel past changes in carbonate accumulation and sediment coarse fraction, and allow a detailed core to core correlation. From these results two main patterns emerge: (1) In cores from shallower than 4300 m and from well above the present lysocline, large temporal changes in p-wave velocity parallel the production of planktonic foraminifera and the climatic history recorded in the sediments, and (2) below 4300 m, the position of the foraminiferal lysocline in the western equatorial Atlantic, large downcore p-wave velocity fluctuations gradually disappear due to dissolution of carbonate sediments. Dissolution also causes a distinct decrease in p-wave velocity and acoustic reflectivity in surface sediments across the present foraminiferal lysocline. Thus, past changes in the position of the foraminiferal lysocline or calcite compensation depth that caused distinct changes in reflectivity of sediments should lead to distinct reflectors within sediment columns. Their distribution can be utilized to map paleowater masses with different degrees of carbonate saturation.

Description: Based on detailed reconstructions of global distribution patterns, both paleoproductivity and the benthic δ13C record of CO2, which is dissolved in the deep ocean, strongly differed between the Last Glacial Maximum and the Holocene. With the onset of Termination I about 15,000 years ago, the new (export) production of low- and mid-latitude upwelling cells started to decline by more than 2-4 Gt carbon/year. This reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric CO2 as recorded in ice cores and, with a slight delay of more than 1000 years, to a large-scale gradual CO2 depletion of the deep ocean by about 650 Gt C. This estimate is based on an average increase in benthic δ13C by 0.4–0.5‰. The decrease in new production also matches a clear 13C depletion of organic matter, possibly recording an end of extreme nutrient utilization in upwelling cells. As shown by Sarnthein et al., [1987], the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades, which in turn was linked via a shrinking extent of sea ice to a massive increase in high-latitude insolation, i.e., to orbital forcing as primary cause.

Description: At Site 658, and especially at Site 660, sediments rich in biogenic opal were recovered. The fractions of biogenic silica, biogenic carbonate, and terrigenous material vary throughout the entire sequence at these sites (see chapters for Sites 658 and 660, this volume). At Site 660, biogenic-opal contents up to 100% are common in Eocene sediments. In studying these opal-rich sediments, a rapid method for estimating biogenic opal published by Mann and Muller (1980) was found useful. These authors applied an X-ray method which measures the height of a broad, diffuse reflection band of opal extending from about 15° to 32° 20, with a maximum at about 22° 20 (i.e., 4.04A) (Fig. 1, IB). Furthermore, this paper describes another method for estimating variations in the biogenic-opal content by using grain density. Grain density (p) can easily be determined by measuring the weight (G) and the volume (V) of the dry sediment, where p = G/P7g/cm3).

Description: The "Discovery" collections contain 51 specimens ot Alluroteuthis antarct,cus from the Southern Ocean 0'"-30°E, S of the Antarctic Polar Front. Of these, 45 specimens were caught during "Discovery" Cruise 100 with the open1ng-clos1ng "RMT 8" net. Capture rate of the species was highest in the 800-900 m depth layer. At night. Alluroteuthis appears to spread vertically and there is evidence of ontogenetic descent. When vertical distribution of A. antarcticus is plotted as a tunclion of mantle length and compared with the distribution of the cranchi1d Galiteuthis glac,alis apparently there is spacial separation between the two species in the water column. The degree of ecological separation cannot be determined in the absence of information on the trophic ecology of these squids.

Description: The subgenera in three genera of oegopsid squid family Enoploteuthidae (Enoploteuthis, Abralia and Abraliopsis) are revised. The genus Enoploteuthis contains two subgenera, Enoploteuthis s. str. and Paraenoploteuthis nov. The former subgeneric arrangement of the genus Abralia is changed. It is divisible into five subgenera, namely, Abralia s. str., Astrabralia, Asteroteuthis, Pygmabralia, and Heterabralia nov. The genus Abraliopsis consists of four subgenera. Abraliopsis s. str., Micrabralia, Boreabraliopsis nov. , and Pfefferiteuthis nov. Relationships among genera and subgenera of the family are discussed.

Description: The present paper describes composition and abundance of meso- and macrozooplankton in the epipelagic zone of the Weddell Sea and gives a systematic review of encountered species regarding results of earlier expeditions. Material was sampled from 6 February to 10 March 1983 from RV Polarstern with a RMT 1+8 m (320 and 4500 μm mesh size). In agreement with topography and water mass distribution three distinct communities were defined, clearly separated by cluster analysis: The Southern Shelf Community has lowest abundances (approx. 9000 ind./1000 m3). Euphausia crystallorophias and Metridia gerlachei are predominating. Compared with the low overall abundance the number of regularly occurring species is high (55) due to many neritic forms. Herbivores and omnivores are dominating (58% and 35%). The North-eastern Shelf Community has highest abundances (about 31 000 ind./1000 m3). It is predominated by copepodites I–III of Calanus propinquus and Calanoides acutus (61%). The faunal composition is characterized by both oceanic and neritic species (64). Fine-filter feeders are prevailing (65%). The Oceanic Community has a mean abundance of approximately 23 000 ind./1000 m3, consisting of 61 species. Dominances are not as pronounced as in the shelf communities. Apart from abundant species like Calanus propinquus, Calanoides acutus, Metridia gerlachei, Oithona spp. and Oncaea spp. many typical inhabitants of the Eastwind Drift are encountered. All feeding types have about the same importance in the Oceanic Community.

Description: The eastern part of the North Atlantic subtropical gyre is found in the region between the Azores and the Cape Verde Islands. A study of the gyre structure in the area east of 35°W between 8°N and 41°N is presented. The geostrophic flow field determined from historical temperature-salinity data sets by objective analysis indicates seasonal variations in shape but no significant changes in the magnitude of volume transports. The eastern part of the gyre has a larger east-west and smaller north-south extension in summer compared with the winter season. The center shifts by about 2° latitude to the south from winter to summer. Long-term temperature time series (6.5 years) from a mooring near the Azores are consistent with these results, showing always a consistent temperature increase at the beginning of the year which is apparently due to the displacement of the northeastern part of the gyre. A comparison between the mean flow fields and fields obtained from individual zonal sections indicates large deviations north and south of the gyre but small deviations within the gyre.

Description: 2. Auflage

Description: The western margin of the Tauera Window (Eastern Alps) is defined by a low angle westward dipping fault zone of potently We disp lacement. Ductile deformation of the fault rocks results in a carpet of mylonites up to 400 metres thick. Evidence from shear criteria and the excision of part of the Cretaceous-Tertiary metamorphic edifice both indicate normal displacements, and relative movement of Austroalpine nappe complex towards the west. The Sterzing-Steinach mylonite zone overprints the Alpine nappe edifice. Movements occurred on the cooling path of the Tauern metamorphism, and may be as recent as Middle Miocene. The Kinematics and geometry of the mylonite zone constrain two likely t ectonic explanations that are both compatible with secondary thining of a thick orogenic wedge. (1) Ute the Austroalpine nappe pile due to tectonic unroofing of the Tauern window. (2) Continental escape by east-west stretching of the Alpine orogenic wedge in response to continental collision.

Description: The microstructures and crystal fabrics associated with the development of an amphibolite facies quartzo-feldspathic mylonitic shear zone (Torridon, NW Scotland) have been investigated using SEM electron channelling. Our results illustrate a variety of microstructures and fabrics which attest to a complex shear zone deformation history. Microstructural variation is particularly pronounced at low shear strains: significant intragranular deformation occurs via a domino-faulting style process, whilst mechanical incompatibilities between individual grains result in characteristic grain boundary deformation accommodation microstructures. A sudden reduction in grain size defines the transition to medium shear strains, but many of the boundaries inherited from the original and low shear strain regions can still be recognized and define distinctive bands oriented at low angles to the shear zone margin. Grains within these bands have somewhat steeper preferred dimensional orientations. These domains persist into the high shear strain mylonitic region, where they are oriented subparallel to the shear zone margin and consist of sub-20 μm grains. The microstructures suggest that the principal deformation mechanism was intracrystalline plasticity (with contributions from grain size reduction via dynamic recrystallization, grain boundary migration and grain boundary sliding). Crystal fabrics measured from the shear zone vary with position depending on the shear strain involved, and are consistent with the operation of several crystal slip systems (e.g. prism, basal, rhomb and acute rhomb planes) in a consistent direction (probably parallel to a and/or m). They also reveal the presence of Dauphine twinning and suggest that this may be a significant process in quartz deformation. A single crystal fabric evolution path linking the shear zone margin fabric with the mylonitic fabric was not observed. Rather, the mylonitic fabric reflects the instantaneous fabric which developed at a particular location for a particular shear strain and original parental grain orientation. The mature shear zone therefore consists of a series of deformed original grains stacked on top of each other in a manner which preserves original grain boundaries and intragranular features which develop during shear zone evolution. The stability of some microstructures to higher shear strains, the exploitation of others at lower shear strains, and a continuously evolving crystal fabric, mean that the strain gradient observed across many shear zones is unlikely to be equivalent to a time gradient.

Description: The spatial distribution of the subtropical salinity maximum is identified using historical and recent data from the eastern North Atlantic. In the regions with high frequency of occurrence of the salinity maximum, the relative contributions of advection, eddy diffusion and double diffusion to the salt balance below the maximum salinity layer are determined. McDougall's (1984, Journal of Physical Oceanography, 14, 1577–1589) salt balance equation for neutral surfaces is used in this analysis. The data base consists of two meridional CTD sections along 33° and 27°W between 10° and 35°N, mean temperature-salinity profiles in 5° × 5° squares presented by Emery and Dewar (1982), and mean velocity profiles in 3° × 3° squares evaluated by Stramma (1984, Journal of Marine Research, 42, 537–558). The tropical salinity maximum tongue is found to be quite persistent in its salinity value and its geographic distribution, but less clearly in its vertical or isopycnal position. Double diffusion due to salt-fingering appears to be an important process for the salt balance below the salinity maximum layer. An approximate estimate of the double-diffusive salt flux is obtained. Near the subtropical source region, the double-diffusive salt flux is balanced primarily by isopycnal advection; further to the south it is also balanced by isopycnal eddy diffusion. Maximum double-diffusive fluxes correspond in magnitude to the mean salt flux caused by the excess in evaporation at the surface in the central subtropics. The resulting isopycnal and diapycnal eddy-mixing coefficients derived by a linear inversion technique have the reasonable values of Ki = (11 ± 5) × 102 m2 s−1 and Kd = (4 ± 2) × 10−5 m2 s−1. Considering the intermittency of the double-diffusive process, limiting values for the mean eddy-mixing coefficients are determined by neglecting the contribution of the double-diffusive salt fluxes. This leads to Ki = (5 ± 2) × 102 m2 s−1 and Kd = (5 ± 1) × 10−5 m2 s−1 for the isopycnal and diapycnal mixing coefficients, respectively.