ALBERT

Description: Dates of Cruise: 18.7.96 - 4.8.96. General Subject of Research: Sampling of active volcanism on the middle Kolbeinsey Ridge and the Eggvin Bank. Port Calls: Kiel, Reykjavik.

Description: The rigid, polycrystalline otolith of teleosts is a side-branch of the general evolution of endolymphatic otoconia that extends from the sharks and rays to the higher vertebrates including man. The transition from the otoconial mass found in the endolymphatic sac of sharks and rays to the rigid polycrystalline otolith of teleosts probably occurred by progressive fusion of otoconia from a loose aggregate to a semi-rigid mass. Traces of the primitive fused otoconia type of otolith still occur in the otherwise polycrystalline otoliths of some teleosts, and a few species of fish retain otoliths that are probably similar to the primitive fused otoconia type of otolith. The morphology of the fusion of otoconia varies according to the polymorph of calcium carbonate that is involved, as well as the particular crystal habit of the polymorph. Analyses of the size distributions of the polymorph-specific morphologies and crystal structure of otoconia suggest that three physical chemical processes, Ostwald ripening, Keith-Padden spherulitic growth and carbonate cementation are significant in the chemistry of fusion of otoconia in the evolution of the aragonite teleost otolith. Predictions of otoconia growth rate from the theory of Ostwald ripening can be compared with predictions from the Keith-Padden theory of spherulitic growth.

Description: One of the most puzzling characteristics of sea-floor morphology is the occurrence of anomalously shallow, fracture-zone–parallel, oceanic transverse ridges. A model is proposed for the formation of transverse ridges near lat 21° and 24°N on the Mid-Atlantic Ridge in which the differential responses of large-offset and small-offset fracture zones to recent changes in spreading direction result in the generation of normal faults that coincide with the off-axis traces of fracture zones. Numerical models of the flexural response of the lithosphere to normal faulting suggest that modest amounts of extension (〈5 km) along low-angle faults (〈45°) are responsible for the transverse ridges.

Description: This study experimentally examines potential shifts in epilithic bacterial biomass and productivity in response to variations in epilithic algal biomass and labile dissolved organic carbon (DOC) during stream biofilm colonization. I predicted that epilithic bacteria would respond positively to allochthonous DOC early in biofilm colonization and respond positively to increased algal biomass late in biofilm colonization. Using once-through, experimental-stream channels, a 2 × 2 factorial design was employed in which light (shaded vs. non-shaded) and labile DOC (glucose-amended vs. ambient) were manipulated. Ceramic tiles were used as substrates for biofilm colonization and were sampled at different colonization stages. Shading significantly reduced chlorophyll a, live-algal bio-volume, and ash-free dry mass throughout colonization. Bacterial biomass increased significantly during biofilm colonization, but was not significantly different among treatments. Incorporation of [〈sup〉3〈/sup〉H]thymidine into bacterial DNA, which was measured as a surrogate for bacterial productivity, was significantly greater in the glucose-amended channels throughout colonization, but it increased in the unshaded, ambient treatment in late colonization as well. These results suggest that labile DOC in the water column can potentially function as a control for epilithic bacteria throughout biofilm colonization, whereas epilithic algae can stimulate bacteria late in biofilm colonization in productive stream ecosystems.

Description: The Sula Ridge Reef complex, a large cold-water coral reef structure on the mid-Norwegian shelf built mainly by Lophelia pertusa, was mapped entirely using a high-resolution sidescan sonar. In addition, a dense echosounding grid, underwater vide observations and dives using the manned research submersible Jago, provided precise high-quality ground-truthing, and allowed a detailed interpretation of the reef structure and its surrounding geological features. The result of this visual sidescan sonar interpretation is a facies map that delineates different potential habitats within the coral reef environment, e.g. live coral reef, dead coral structure and sediment-covered coral/rubble, etc. In an attempt to improve this interpretation, computer-assisted image analysis was applied to a representative section of the sonar data to try to reveal patterns 'invisible' to the human eye (using the TexAn software). Texture analysis uses Grey-Level Cooccurrence Matrices (GLCMs) to calculate statistical indices quantifying the distribution of grey levels and their spatial relationship within the image. For example, regions of rough textures (coral mounds) can be distinguished from areas of smooth background sediment or zones of heterogeneous texture resulting from sediment-covered coral debris and dropstones colonized by sponges. The results of the computer-assisted approach were carefully compared with the earlier visual interpretation ro identify the differences and to see where the interpretation could be improved. Overall, it shows that texture analysis is a useful tool to make facies/habitat mapping from sidescan sonar easier and faster, revealing details overlooked during visual interpretation. However, validation of certain details by an experienced interpreter is still necessary, and therefore visual and computer-assisted interpretation should be used as complementary tools.

Description: Knowledge of ambient optical noise is essential for designers of free space optical links, for designing resilient circuits. An experimental characterisation of the most commonly encountered ambient optical radiation is presented. The study includes tungsten filament sources, low and high frequency fluorescent lights, IR headphones, TV remote controls and daylight. Practical means to reduce their influence on the performance of the links are also given. The results are also valuable for setting a standard way of comparing wireless IR links, based on testing their performance under such ambient noise.

Description: Rates of petroleum seepage must ultimately be related to the rate of supply from below. This could be either from a leaking accumulation or directly from the source rock itself. However, many things can happen during migration to the surface, such that the relationship between trap leakage rates and surface seep rates remains obscure. We calculate the potential flux rates of gas leakage across seals and compare these with measurements of fluxes for three seepage sites on the European continental shelf. We conclude that seepage flow rates can be modeled effectively by assuming Poiseuille flow through the matrix of mudstone seals. Flow rates calculated in this way are about 0.4-1.0 m3 gas/m2/year, consistent with field observations.

Description: Most highly fecund marine fish show a steep decline in natural death rate from egg to first maturity, after which the natural mortality rate remains constant, or may even increase with age for old animals. Relatively few investigations have quantified early life-history mortality vectors for short-lived invertebrate stocks, but this overall picture is also true here for species with planktonic life stages such as penaeid shrimps, and for squids. If M decreases rapidly with age, one logical approach to demographic analysis is by subdividing the lifespan into intervals which increase in duration in proportion to the age up to the start of each interval. This time subdivision strategy is referred to as `gnomonic’. Earlier work (Caddy, 1990) showed that if a reciprocal mortality function applies with age, the product of the instantaneous annual rate of natural mortality and interval duration should be roughly constant for gnomonic intervals. This working hypothesis is shown to produce similar results to the reciprocal function for Mt, but allows a simpler approach to generating realistic life history Mt vectors in the absence of direct estimates of M for stock assessment. Values of a constant probability of death, G = Mt Δt, were used to generate vectors of M-at-age for a gnomonic series of intervals from hatching up to the mean parental age. The value of G is found by iteration that results in 2 survivors from the mean population fecundity by 1 year of age, under the assumption of steady-state population replacement for an unexploited stock. The natural mortality rate in the final, longest interval was assumed to correspond to the ‘constant adult M’ value used in stock assessment. Two extremes of reproductive strategy were chosen by comparison with data from for annual species of cephalopods or penaeid shrimps: cephalopods such as Sepia sp. and Rossia sp., with few, large yolky eggs (and/or parental care), occupy one extreme, and are contrasted with high fecundity penaeid shrimps and at least some Illex squids. The first category has a low fecundity (130–150 eggs, and a K-selected reproductive strategy). Values of ‘adult M’ of the order of 1.0–1.3 are predicted for the last 60–80% of the annual life span. The high fecundity category (200 000 eggs or more) are opportunistic spawners such as many penaeids and some oceanic squids, and follow an r-selected reproductive strategy. An instantaneous value for pre-spawning M of the order of 2.8–3.4 is predicted for the same period mentioned above. Neither range of values falls outside those in the literature, for which a brief summary is presented. An important research question relates to the order of magnitude of post-hatching mortality under population stability: it is suggested that irrespective of the specific model used for changes in M with age, this falls rapidly from an initial rate of some 50–75% per day for short-lived, high fecundity species in the 2 days following hatching, unless adult M values are much higher than above, and of the order of 25–40% for the low fecundity organisms over the same initial interval.

Description: Some aspects of the atmospheric chemistry of methyl thiolformate (CH3SCHO), a recently detected intermediate in the oxidation of dimethyl sulfide, have been investigated at 298 K and 1000 mbar total pressure in large reaction chambers using long path in situ FTIR absorption spectroscopy for the analysis. Rate coefficients of (1.11 ± 0.22) × 10-11 and (5.80 ± 0.80) × 10-11 cm3 molecule-1 s-1 have been determined for its reaction with OH radicals and Cl atoms, respectively. The UV spectrum of CH3SCHO has been measured in the range 220−355 nm and a lower limit of 5.4 days determined for its atmospheric photolytic lifetime. Detailed product analyses have made for the OH and Cl initiated photooxidation of CH3SCHO. Strong SO absorption bands observed in both systems are tentatively assigned to CH3SOCHO in the OH system and to CH3SOCl in the Cl system. The first gas-phase spectra of CH3SCl and CH3SOCl are also presented. The results are discussed with respect to the atmospheric chemistry of CH3SCHO and possible consequences for the photooxidation mechanism of dimethyl sulfide.

Description: Abstract The famous association of metagabbros, eclogites, glaucophanites, jadeite rocks and ultramafics from the island of Syros forms a distinct lithostratigraphic or tectonic unit. It is interpreted as a high-pressure metamorphic ophiolite suite. This paper provides geochemical and Sr-isotope constraints on the geotectonic setting in which the magmatic protoliths of the Syros metabasites were formed. A compositional gap exists between the metagabbros with Mg-numbers [Mg# = Mg/(0.85Fetot + Mg) atomic ratio] of 0.75-0.88 on the one hand and eclogites and garnet-glaucophanites on the other hand with Mg# of 0.35-0.62, and maximum total iron contents of up to 18 wt.% FeOtot. Metagabbros from various localities and glaucophanites collected around Manna form geochemically coherent groups with smooth correlations between compatible as well as immobile incompatible elements and Mg#. By contrast, the behaviour of immobile incompatible elements, and to some extent also of compatible elements, is highly unsystematic in the eclogites and garnet-glaucophanites. Also, the more mobile elements display a wide scatter in all rocks. This, in conjunction with the unsystematic variation of Sr-isotopes, is thought to be due to secondary alteration. From the strong correlation of Ni and Cr with Mg# and the flat REE patterns lacking Eu-anomalies, a cumulus nature is inferred for olivine, clinopyroxene, and spinel, associated with intercumulus formation of plagioclase in the magmatic protoliths of the metagabbros. There is no direct genetic link between these rocks and the precursors of the Manna-type glaucophanites with REE characteristics typical of N- to T-type MORB. The extremely high geochemical diversity of the eclogites and garnet-glaucophanites from Syros favours individual evolution of their protoliths in small magma bodies as suggested for superferric eclogites from the Western and Ligurian Alps, as well as the ferrogabbros from the ophiolites of the Northern Apennines. From the geochemistry of the Syros metabasites along with the initial 87Sr/86Sr ratios of the metagabbros between 0.7031 and 0.7033, as well as an eNd value of 7.7 from a garnet glaucophanite, the magmatic protoliths are inferred to have formed in a back-arc setting. By analogy to the association of gabbros and ferrogabbros adjacent to the Atlantis II fracture zone of the SW Indian Ridge, we further suggest an origin at a spreading ridge in proximity to a transform fault.

Description: Statolith morphology and microstructure were studied in two common species of panktonic cranchiid squids, Belonella borealis [four juveniles with mantle length (ML) 375–450 mm] and Galiteuthis phyllura (13 paralarvae and juveniles, ML 9–235mm), caught near the bottom and in pelagic layers over the continental slope of Siberia in the northwest Bering Sea. The total number of growth increments within the statoliths ranged from 277 to 294 in B.borealis and from 10 to 209 in G.phyllura. Assuming that these increments were produced daily, both species grow rapidly in length (daily growth rate = 1.13mm day−1 during the first 8–10 months of their juvenile phase in the mesopelagic layers, prior to migration into deeper waters for maturation.

Description: Climate changes since AD 1200 have been of high magnitude. Significant lowering of temperatures occurred during the neoglacial (‘Little Ice Age’), between AD 1200–1400 and AD 1600–1800 with maximum cooling in the mid-late eighteenth century. At this time many European valley/cirque glaciers reached their maximum extent since the late Pleistocene. Neoglaciation was followed by an overall warming trend, although with significant reversals superimposed. Alongside these temperature changes were variations in the nature and amount of precipitation, and in consequence, river basins in north, west and central Europe experienced enhanced fluvial activity between 1250 and 1550 and particularly between 1750 and 1900. These phases coincide with periods of climatic transition; cooling after the Medieval optimum and warming during the latter stages of the Little Ice Age respectively. In contrast, the intervening period (1550–1750), which corresponds with the most severe phases of the last neoglacial, was associated with lower rates of fluvial activity.

Description: The natural feeding of the two most abundant ommastrephid squid (Cephalopoda: Ommastrephidae) in Galician waters was studied and compared. A sample of 334 stomach contents of Todaropsis eblanae (34–222 mm ML) and 267 stomach contents of Illex coindetii (50–379 mm ML) caught by commercial trawlers was examined. A total of 21 (T. eblanae) and 23 (I. coindetii) different prey items, belonging to three zoological groups (Teleostei, Crustacea and Cephalopoda), were taken by these cephalopods. However, 43% of the T. eblanae diet comprised only one fish species, Micromesistius poutassou. The diet of these squid species was significantly influenced by the geographical area (both species), size (T. eblanae) and maturation (I. coindetii). Feeding rate of both species decreased with size, but the percentage of stomachs with food remains increased in maturing and mature females. Weight of prey captured was dependent on available prey sizes and, in small individuals, maximum prey weight was very close to the squid weight. Both squid species are mainly neritic nekto-benthic predators, but I. coindetii seems to have a broader and more pelagic diet.

Description: Distribution, abundance, and length-frequency composition of schoolmaster gonate squid, Berryteuthis magister, were studied during seven trawl surveys in the western Bering Sea between June and November 1993. Statolith age analysis was undertaken for 1,381 B. magister to estimate age, stock structure, and both growth and maturation rates. Three kinds of growth increments were revealed in B. magister statoliths. Daily periodicity of the second-order increments was confirmed by two independent, indirect methods. According to our data, B. magister live 〉1 yr; the oldest specimen was about 16 months old. Berryteuthis magister is a slow-growing and slow-maturing squid, and males exhibit slower growth and earlier maturation than do females. Growth in length was best described by a logistic curve, with a larger asymptotic parameter for females. In summer, concentrations of B. magister were low within the whole region, whereas in September-October squids aggregated into dense shoals over the continental slope of the Navarin-Olyutorsky region and Olyutorsky Bay. Stock structure of B. magister was complicated: each month, from 5 to 12 (usually 7-8) monthly classes of squid were encountered in the western Bering Sea. Three seasonal groups of B. magister occurred in the region: winter-, summer- and fall-hatched squids utilizing resources of the continental slope in different ways. A possible life cycle for the B. magister fall-hatched group includes a longevity of ca. 2 yr: 6 mo of embryonic development and 18 mo of postembryonic growth.

Description: Malaysia has a climate of high humidity, high temperature and abundant rainfall. Rivers supply about 97% of the country's total water needs while ground water accounts for the rest. About 40% of the treated water is lost through man-caused leakages. With a population of 18.3 million people, the total annual domestic, industrial and irrigation water demand is about 11.6 x 106 MI. This figure is projected to rise to 15.2 x 106 MI by year 2000. At present, the total daily water demand is about 4,979 MI and the production capacity is 6,513 MI. Water use and misuse now strain the nation's fragile aquatic environment and natural ecosystems. Current water resource management priorities include water quality improvement, river rehabilitation to restore over-channalized or polluted rivers and development of the inland fisheries potential especially in large man-made reservoirs. A River Basin Information System has been developed to provide integrated information on catchment characteristics, landuse, population and socio-economic profile, river flow, pollution sources, water quality classification, and aquatic biota. Vision 2020 challenges call for a long-term perspective in inland water resource management. Critical post-audits of largescale development and strategic research aimed at alternative and interacting patterns of landwater use are urgently needed.

Description: Major plate tectonic, climatic and oceanographic changes occurred during the Cretaceous. They led to paleoecological rearrangements within the frameworks of bioconstructions and in the composition of benthic associations of the pelagic shelf seas. Based on recently published rotations the plate tectonic movement of the continents and terranes was simulated and paleogeographical changes during Early and Late Cretaceous were illustrated. The application of the new paleogeographic maps increases the information value of biogeographic data. The biogeography of Late Cretaceous inoceramids and framebuilding rudists was used as an example to test their suitability as indicators for paleooceanographic changes in the context of plate tectonic, sealevel and climate changes as well as the position of climate zones.

Description: This paper reviews research, development and design aspects of recent technologies for deep-ocean mining systems to recover manganese nodules and cobalt-rich manganese crusts from the seafloor at an 800-6,000-m depth. It also discusses selective technological challenges. The manganese crust is characterized on the basis of preliminary data. Development of more sophisticated instruments and an extensive survey are required to determine its accurate distribution, abundance and physical characteristics. The technical challenges particularly in the fluid-structure interactions of the pipe systems and the miner track-keeping for production are yet to be defined. The United States has a greater geological emphasis, while Japan places a greater emphasis on engineering. In the last 15 years, few significantly new technologies appear to have evolved in the nodule mining system, system integration and integrated system control. However, subsystems have been designed and tested systematically in Japan. As the technologies of the past 30 years age, the mining systems and technologies need to be upgraded, with advancements in new sensors, control and data acquisition technologies.

Description: BP/Chevron well 14/6–1 drilled in the East Orkney Basin has penetrated Devonian sedimentary rocks which can be dated palynologically as within the latest Givetian to early Frasnian interval. This microflora contains the first substantiated record in Western Europe of Archaeoperisaccus, a spore hitherto regarded as restricted to northern Laurasia. Three grey-green intervals within the well contain marine microfossils which provide the first direct evidence for the movement of marine waters into the northern part of the Old Red Sandstone continent. Onshore an Eday Marls section in the Bay of Berstane, Orkney contains a marine microfauna which demonstrates the presence of a marine incursion of mid––late Givetian age. This is the first record of a Devonian marine incursion in Scotland. Combination of this palaeontological data with sedimentological studies of the Eday Marls and Upper Old Red Sandstone suggests that a wide flat sabkha plain extended eastwards from the onshore Orcadian Basin during the later stages of its infill, and was subjected to episodic marine incursions. These incursions are tentatively linked with marine transgressions into the Argyll area of the Central North Sea. Two orders of cyclicity occur within the dated Devonian interval of 14/6–1, and are interpreted as resulting from orbital cyclicity (at periodicities of 39.5 and 413.9 ky). This indicates that the control on the Devonian sea level maxima may have been orbital cyclicity. These marine incursions are speculatively correlated to high-stands on the Devonian sea-level curve. The Bay of Berstane marine incursion representing the Taghanic Onlap whilst those in 14/6–1 are the Rhinestreet, Middlesex and Genundewa transgressions. Reconsideration of the palaeogeography of the northern margin to the marine Devonian indicates that the sea entered the Orcadian Basin from the east along the Tornquist Zone at the margin of the Fenno-Scandian High.

Description: Introduction: The new Arctic Challenge Not counting the geographic exploration of the Arctic coast lines by fishermen, commercial traders and a few explorers it is only little more than 100 years ago that systematic investigations of the natural properties of the Arctic Ocean began. It was the German Carl Koldewey who sailed to Fram Strait in 1868 to study the nature of the ice margin, and he was followed by the famous Norwegian Fridtjof Nansen who drifted 1893-1 895 (Nansen, 1904) along with the central eastern Arctic Transpolar Drift - on his newly built polar research vessel FRAM - in his attempt to reach the North Pole (Fig. 1). Both men and their Crews were driven by the desire to understand the special oceanographic properties of the Arctic Oceans as well as the climatic variability and significance of the Arctic sea ice and its distribution. The motive of modern Arctic research is much the Same as more than 100 years ago, but Part of our tools and approaches have been improved over the past 100 years in such a way that we stand a much greater chance to succeed than these scientific pioneers. (...)

Description: Fossil coelacanths, and their only living representative Latimeria chalumnae, possess a small, supplementary epicaudal fin of unknown function at the tip of the large tail. Movements of this fin were analyzed on film sequences taken with submersibles in the fish's natural habitat off Grande Comore, Indian Ocean. Epicaudal fin beats were not coordinated with strokes of paired and unpaired lobed fins, and the epicaudal fin did not move continuously. When in action, successive fin beats were performed more-or-less rhythmically but varied considerably in duration. Epicaudal fin beats occurred mainly in three different situations: during curve swimming, with slow forward motion of the body; during narrow turns on a point without significant forward motion of the body; and during station holding without forward, backward, or sideward motion of the body. In the latter case, the fin regularly stood still at maximum deflexion for several seconds. In turns and curves, epicaudal fin beats appeared to have a locomotory function, whereas during hovering, with standstills of the fin at maximum deflexion, beats presumably have a sensory function. The lateral-line canal extends to the very tip of the epicaudal lobe. If the lobe is held laterally at an angle to a local current parallel to the main body axis or to a current resulting from backward motions, water displacement in front of the lobe could be detected by the lateral line on the lobe.

Description: A new species of the holopodid genus Cyathidium was found on rocks off Grande Comore in a depth of around 200 m. Based on external morphology of resting animals, the new species Cyathidium plantei sp. n is described, with emphasis on comparison to the only other extant species (C. foresti) as well as to the four extinct representatives of the genus. Concerning morphological characters, the new species is almost identical to the Cretaceous C. depressum. A cladistic analysis of the entire family, including the genus Holopus, shares a peculiar pattern of bending of the arms, which in principle is an apomorphic character of the family and in detail shows variations within the family. In addition, stratigraphic data are used for the determination of the evolutionary direction. This analysis reveals that the two recent species are closely related to each other, and to the fossil C. depressum. from which the entire family is probably derived.

Description: The steep Continental slope of the Red Sea beyond the euphotic zone contains the least known biota of the Red Sea. More knowledge exists on the Red Sea’s deep sea than on this transitional zone between photic and aphotic depth. Since 1981, with the help of the research submersibles "Geo" and" Jago", over 430 dives to a maximum depth of 402 m were carried out at various locations off Djibouti, Sudan, Egypt, and Israel; the topics covered include biology, microbiology, physiology, geology, geophysics, and oceanography. The submersible exploration of the Red Sea’s twilight zone is a new, modern step continuing the classical surface-bound deep-sea expeditions which started in the 19lh Century - of which the Austro-Hungarian "Pola" expeditions were among the first.

Description: A protein unique to phosphorus stress observed in Dunaliella tertiolecta Butcher was studied in the context of phosphate‐limited cell physiology and is a potential diagnostic indicator of phosphate deficiency in this alga. Cells were grown over a range of limited, steady‐state growth rates and at maximum (replete) and zero (phosphate‐starved) growth rates. The stress protein, absent in nutrient‐replete cells, was produced under all steady‐state phosphate‐limited conditions and increased in abundance with increasing limitation (decreasing growth rate). Cellular carbon: phosphorus ratios and the maximum uptake rate of phosphate (Vm) increased with increasing limitation, whereas the ratio of chlorophyll a: carbon decreased. Alkaline phosphatase activity did not respond to limitation but was measurable in starved, stationary‐phase cells. Fv/Fm, a measure of photochemical efficiency, was a nonlinear, saturating function of p, as commonly observed under N limitation. The maximum Fv/Fm of 0.64 was measured in nutrient‐replete cells growing at μmax, and a value of zero was measured in stationary‐phase starved cells. When physiological parameters were compared, the P‐stress protein abundance and Fv/Fm were the most sensitive indicators of the level of deficiency. The stress protein was not produced under N‐ or Fe‐limited conditions. It is of high molecular weight (〉200) and is associated with internal cell membranes. The stress protein has several characteristics that make it a potential diagnostic indicator: it is 1) unique to phosphorus limitation (i.e. absent under all other conditions), 2) present under limiting as well as starved conditions, 3) sensitive to the level of limitation, and 4) observable without time‐course incubation of live samples.

Description: Dissolved and atmospheric nitrous oxide (N2O) were measured on the legs 3 and 5 of the R/V Meteor cruise 32 in the Arabian Sea. A cruise track along 65°E was followed during both the intermonsoon (May 1995) and the southwest (SW) monsoon (July/August 1995) periods. During the second leg the coastal and open ocean upwelling regions off the Arabian Peninsula were also investigated. Mean N2O saturations for the oceanic regions of the Arabian Sea were in the range of 99–103% during the intermonsoon and 103–230% during the SW monsoon. Computed annual emissions of 0.8–1.5 Tg N2O for the Arabian Sea are considerably higher than previous estimates, indicating that the role of upwelling regions, such as the Arabian Sea, may be more important than previously assumed in global budgets of oceanic N2O emissions.

Description: A three meter thick horizon in the white chalk of the Lägerdorf-Kronsmoor-Hemmoor section (northwestern Germany), biostratigraphically characterized by the co-occurrence of Belemnella gracilis, Belemnella sumensis, Belemnitella pulchra, Bolivinoides draco miliaris, Bolivinoides draco draco and the recognitionn of the Standard Nannofossil Zone CC24 can be correlated precisely with 7 m in the succession at DSDP Site 548 (northeastern Atlantic) and the 2 m belemnite horizon of the Inoceramus-Marls (Ultrahelveticum) near Siegsdorf (Bavaria).

Description: Aus dem in 36 m Mächtigkeit erschlossenen miozänen Glimmertonprofil von Groß Pampau wird das Vorkommen der Mollusken und Bolboformen beschrieben. Die durch Mollusken definierten regionalen Unterstufen der Zeitspanne spätes Reinbekium bis spätes Langenfeldium werden über die Bo/boforma-Biostratigraphie mit der Nannoplankton-Giiederung korreliert und nach BERGGREN et al. (1995) datiert. Neu eingeführt werden die Mollusken Periploma ariei und Ringicu/a tiedemanni sowie Bolboforma robustabadenensis und Bolboforma contorta.

Description: The interrelation between deformation styles and behavior of fluids in accretionary prisms is under debate, particularly the possibility that overpressuring within the basal decollement may enable mechanical decoupling of the prism from the subducting material. Anisotropy of magnetic susceptibility (AMS) data from sediments spanning the basal decollement of the Barbados accretionary prism show a striking progression across this structure that strongly supports the hypothesis that it is markedly overpressured. In the accretionary prism, above the decollement, the minimum AMS axes are subhorizontal and oriented nearly east-west, whereas the maximum AMS axes are oriented nearly north-south and shallowly inclined. At the top of the decollement, the minimum AMS axes orientations abruptly change to nearly vertical; this orientation is maintained throughout the decollement and in the underthrust sediments below. The AMS orientations in the prism sediments above the decollement are consistent with lateral shortening due to regional tectonic stress, as the minimum axes generally parallel the convergence vector of the subducting South American plate and the maximum axes are trench-parallel. Because the orientations of the AMS axes in deformed sediments usually parallel the orientations of the principal strains, the AMS results indicate that the incremental strain state in the Barbados prism is one dominated by subhorizontal shortening. In contrast, the AMS axes within and below the decollement are consistent with a strain state dominated by vertical shortening (compaction). This abrupt change in AMS orientations at the top of the decollement at Site 948 is a direct manifestation of mechanical decoupling of the off-scraped prism sediments from the underthrust sediments. The decoupling horizon occurs at the top of the decollement zone, coinciding with the location of flowing, high-pressure fluids.

Description: Phylogenetic relationships within a group of budding purple nonsulfur bacteria of the genus Rhodopseudomonas were studied by DNA-DNA hybridization. Most of the strains were new isolates from natural environments with a wide ränge of physicochemical conditions.A total of 32 strains were analyzed, includ- ing the type strains of Rhodopseudomonas palustris, Rps. rutila, Rps. marina, and Rps. acidophila. Nine phylo- genetically remote clusters were revealed, showing an average DNA-DNA horaology of 15%. One of the Clusters contained the type strain of Rps. marina, isolated front marine habitats, and two new isolates from hot ffeshwater springs. These new isolates tumed out to be facultative halophiles with a salinity Optimum of 1-3% and were assigned to Rps. marina on the basis of their phenotypic characteristics and DNA-DNA homology of 60% with the type strain of this species. The type strain of Rps. acidophila was not specifically related to any other strain used during this investigation. The remaining 26 isolates and the type strains of Rps. palustris and Rps. rutila were very similar phenotypically, but formed seven phylogenetically remote clusters including 13 genospecies; none of the new isolates were closely related to the type strains of Rps. palustris and Rps. rutila, which also proved to be phylogenetically distinct. Thus, the Rps. palustris-like bacteria, which are widespread in nature and comprise phenotypically a homogeneous group, appear to be phylogenetically diverse. The prospects for developing a Classification system for these budding purple nonsulfur bacteria that would be in agreement with their phylogenetic relationships are discussed. Possible correlation between the phylogenetic relationships of these bacteria and the ecological peculiarities of their natural habitats is also considered.

Description: A predictive model of carbon isotope fractionation (sigma p) and abundance (delta13C phyto) is presented under circumstances where photosynthesis is strictly based on CO2(aq) that passively diffuses into marine phytoplankton cells. Similar to other recent models, the one presented here is based on a formulation where the expression of intracellular enzymatic isotope fractionation relative to that imposed by CO2(aq) transport is scaled by the ratio of intracellular to external [CO2(aq)], ci/ce. Unlike previous models, an explicit calculation of ci is made that is dependent on ce as well as cell radius, cell growth rate, cell membrane permeability to CO2(aq), temperature, and, to a limited extent, pH and salinity. This allows direct scaling of ci/ce to each of these factors, and thus a direct prediction of sigma p and delta13C phyto responses to changes in each of these variables. These responses are described, and, where possible, compared to recent experimental and previous modeling results.

Description: The conventional model whereby plume volcanism forms linear age-progressive volcanic chains, with the youngest activity occurring nearest a spreading axis (at a 'hotspot'), has been challenged for the Easter seamount chain1–4. Whereas early work suggested the existence of a linear melting anomaly (a 'hotline')1,2, more recent studies3,4 have proposed a hotspot near Salas y Gomez island, connected with the Easter microplate spreading system by an ~800-km-long, volcanically active plume channel. Here we use geochemical, geological and geochronological data to argue that the hotspot lies close to Easter Island. Moreover, new isotopic data for lavas from the seamount chain provide evidence for bidirectional flow between the spreading axis and the plume, thus supporting geophysical and fluid-dynamical models of mantle flow in a plume/spreading axis system5–7. Material balance and flux considerations show the Easter plume to be weak and cool compared with those beneath larger features such as Iceland, Hawaii and the Galápagos islands.

Description: Two newly designed underway systems for the measurement of CO2 partial pressure (pCO2) in seawater and the atmosphere are described. Results of an intercomparison experiment carried out in the North Sea are presented. A remarkable agreement between the two simultaneously measured (pCO2) data sets was observed even though the spatial variability in surface pCO2 was high. The average difference of all l -min averages of the seawater pCO2 was as low as 0.15 μatm with a standard deviation of 1.2 μatm indicating that no systematic difference is present. A closer examination of the profiles shows that differences tend to be highest during maxima of the pCO2 gradient (up to 14 μatm/min). The time constants of both systems were estimated from laboratory experiments to 45 s, respectively, 75 s thus quantitatively underlining their capability of a fast response to pCO2 changes

Description: Fahrtgebiet: Irmingersee und Ausgang Dänemarkstraße Zweck: Hydrographische Aufnahme im Ausbreitungsgebiet des Overflow-Wassers, Auslegung einer Inverted Echo Sounder Verankerung (I.E.S), Auslegung von satelliten-georteten Driftbojen, Schleppen eines neuen geomagnetischen Elektrokinetographs (TTM3), Erprobung eines GPS-Arrays zur hochgenauen Ortsbestimmung Wiss. Ziele: Ermittlung mesoskaliger Strukturen im Overflow als Eingangsdaten für Simulationsrechnungen

Description: Heat production and nitrate respiration rates were measured simultaneously in the gill tissue of Lucinoma aequizonata. This marine bivalve contains chemoautotrophic, intracellular, bacterial symbionts in its gill tissue. The symbionts show constitutive anaerobic respiration, using nitrate instead of oxygen as a terminal electron acceptor. An immediate increase in heat production was observed after the addition of nitrate to the perfusion medium of the calorimeter and this was accompanied by the appearance of nitrite in the effluent sea water. The nitrate-stimulated heat output was similar under aerobic and anaerobic conditions, which is consistent with the constitutive nature of nitrate respiration. The amount of heat released was dependent on the concentration of nitrate in the perfusion medium. At nitrate concentrations between 0.5 and 5 mmol l-1, the total heat production was increased over twofold relative to unstimulated baseline values. A mean (±s.e.m.) experimental enthalpy of -130±22.6 kJ mol-1 nitrite (N=13) was measured for this concentration range.

Description: Evolution of the Caribbean Plate can be modeled by motions about six successive rotation poles. Opening of Cayman Trough has occurred since 49.5 Ma through westward motion of the Caribbean Plate, eastern Greater Antilles and Chortis Block. Before 49.5 Ma, the eastern Greater-Antilles were west of Cuba, and the southeastern margins of Yucatan and the Nicaragua Rise (Chortis) were aligned. From 67.5 to 49.5 Ma the Caribbean Plate rotated clockwise, opening the Yucatan Basin. From 100 Ma to 67.5 Ma, the Caribbean Plate, with Cuba attached, moved along the southeastern margin of Yucatan-Chortis. At 130 Ma it was attached to northwestern South America.

Description: The late Eocene through Oligocene changes in the paleoceanography of the southernmost Indian Ocean have been reconstructed by means of a coarse fraction analysis of closely spaced samples (20 cm = about 20 kyr) from ODP Site 744, Kerguelen Plateau. Surface water productivity, reconstructed from accumulation rates of opal skeletons and benthic foraminifers is low in the early late Eocene, increases at about 36 Ma and shows a sharp increase to maximum values in the earliest Oligocene. In the early late Oligocene it decreases gradually to a minimum and increases again to a maximum in the latest Oligocene. Beside this general trend productivity varies in short-term cycles of a duration of about 400 kyr (340 kyr in the latest Oligocene) with maxima in productivity in warmer Oligocene periods. These productivity variations are reflected by strong variations in carbonate dissolution. Changes in bottom water mass chemistry have been deduced from the degree of carbonate dissolution and it's relation to productivity proxies. Following Kennett and Stott (1990), it is suggested that a proto-antarctic bottom water (proto-AABW) and an overlying warm, saline deep water (WSDW) from low latitudes shifted vertically and latitudinally with time and exerted their influence on the sediments of Site 744. Proto-AABW is detected by means of strong carbonate dissolution when productivity is low. WSDW is detected by means of an excellent carbonate preservation despite high productivity. Terrigenous material occurs as very coarse ice-rafted detritus (IRD) in the late Eocene (167–168.5 mbsf) and after a main shift in oxygen isotopes in the early Oligocene. Very low amounts of 40–125 μm sized mica and very few quartz grains occur only in high productivity periods and at the transition from low to high productivity periods. These occurrences are attributed to wind/current supply during warmer Oligocene intervals.

Description: Studies on core samples of the genus Porites in the northern Gulf of Aqaba revealed marked short-term variations in the growth rate of this coral over the last 20 years, Individual growth rates show high variations, even among colonies growing next to each other, These variations might be attributed to locally restricted differences in the reef environment, or to endogenous differences between the individual colonies, A general increase in linear extension rate was observed for colonies situated in a relatively undisturbed reef area between 1 m and 15 m water depth. Over the time period 1972–1992, major variations in climate conditions that could have affected coral growth were not observed. Reduction of terrestrial sediment influx is a possible reason for the accelerated growth rates. The effect of intense sediment loading on the rate of coral growth within a stressed environment is demonstrated for one Porites-core taken from a colony growing in the vicinity of the phosphate loading berth at Aqaba. The drastic decrease in growth rate at this location during the observed time span stands in contrast with the general development of Aqaba's reefs and is most probably the result of sediment stress.

Description: Climatic events are imprinted on the sedimentary record of the Baltic Sea. In these sediments, storm events are documented by sandy horizons within the mud sequences which dominate the deeper basins. The spectral characteristics of the storm layer sequences were determined through analyses of the optical density of sediment X-radiographs. Previously the evaluation of X-radiographs was done visually and provided qualitative rather than quantitative information. In order to enable a more objective analysis, an optical scanner was developed. Subsequently the digitized sequence was analysed using Fast Fourier Transformation procedures. The results show that the observed cycles which lead to the formation of alternating layers can be attributed to calendar and solar band frequency variations.

Description: Microfaunal studies of planktic foraminifera carried out on 21 sediment cores from the Norwegian-Greenland Sea (NGS) reveal the spatial and lateral distribution as well as meltwater implication of today's non-polar/subpolar species Beella megastoma (Earland). Previous findings are verified in that this foraminifera is characteristic only of the deglaciation phases of Termination II, III, and VI and not the ensuing interglacial optima, thus, rendering this species a ‘meltwater’ indicator. Its distribution is restricted to cores from the central, i.e., more ‘pelagic’, part of the NGS covering an area as far north as 77 ° latitude. A detailed investigation of Termination II indicates that B. megastoma first appeared in the southwest of the NGS at ~131 ka and then about 6 kyr later in the eastern and northern parts of the NGS. For the entire duration B. megastoma always coincided with the deposition of distinct ice-rafted detritus (IRD) suggesting the presence of drifting icebergs during this period. Two different oceanographic models, each with a two-stepped evolution of the post-Saalian surface water circulation, are proposed to account for this time transgressive character. The mechanism of brine formation as possible oceanic phenomenon forcing Atlantic water northwards is suggested for being responsible for the occurrence of B. megastoma in the NGS during early Termination II. The presence of B. megastoma always ceased with the culmination of the interglacial optimum, oxygen isotopic Substage 5.51 (Eemian), when the subpolar foraminiferal fauna reached highest abundances and a general lack of IRD is observed.

Description: A mineralogical and 4OAr/39Ar study of 13 amphibole samples in the Kamila Amphibolite Belt and Kamila Shear Zone in northern Pakistan has found a correlation between the degree of greenschist facies alteration and quantity of excess 40Ar. Additionally, there is a north–south divide with amphibole samples from the northern region showing larger degrees of gree schist facies alteration, brittle deformation, and excess 40Ar incorporation compared to the predominantly plastically deformed, less altered, amphibole samples from the Kamila Shear Zone in the south. Acid leaching of two amphiboles from the Kamila Amphibolite Belt indicates that a large proportion of the excess 40Ar is correlated with later greenschist facies alteration hases, and can be easily removed by acid etching, thus revealing acceptable regional 40Ar/39Ar plateau ages.

Description: The East Greenland continental margin between c.66 and 68° N consists of a major fjord/trough system that extends from Kangerdlugssuaq Fjord, along Kangerdlugssuaq Trough to Denmark Strait. Measurements of the temperature and salinity of the water column along this transect indicates that ‘warm’ water (0–2°C) underlies the surface Polar Water of the East Greenland Current. A series of short (1–3 m) gravity cores along the fjord/trough transect have sufficient numbers of foraminifera that a suite of AMS 14C dates has been obtained, including both basal and core-top age estimates. Rates of sediment accumulation vary through space and time; over the last 1 ka estimates vary from c. 3 to 0.1 m. These dates and measurements of sediment density, together with measurements of the percentages by weight of total organic carbon and biogenic silica, are used to show graphs of fluxes of the organic and inorganic sediment components over the last 1–14 ka. An analysis of the net flux of foraminifera indicates a reduction in numbers during the Younger Dryas chronozone and a general similarity with data from the Renland (East Greenland) ice core data.

Description: Fish-apatite (teeth and bone fragments) of early Eocene age from Ocean Drilling Program Hole 913B (Greenland Basin) was analyzed, in the absence of biogenic calcite, for stable isotopic (δ1 8θco,2~, δ13C) composition to determine paleosalinity. Comparisons are made with isotopic results for early Eocene fish-apatite from Deep Sea Drilling Project (DSDP) Hole 550 (northeastern Atlantic) and the R0snaεs Clay Formation (Denmark). These two sites represent fully marine and semimarine conditions, respectively. The δ^Ocα,2- values of the fish-apatite from Hole 913B are 4.3%o to 8.1%c more negative than the fish-apatite values from DSDP Hole 550, and 1.9%o to 6.1%o more negative than the values from the R0snses Clay Formation. The results indicate reduced salinity in the early Eocene Greenland Basin relative to the open ocean. Using the present salinity/ δ'8O relationship in the North Atlantic, the salinity in the Greenland Basin was 22 ppt to 28 ppt. The reduced salinity is in agreement with an isolated early Eocene Greenland Basin, as suggested in earlier geophysical and paleontological studies. It is also likely that other parts of the Norwegian-Greenland Sea, such as the Lofoten Basin, exhibited brackish water conditions. Because of similar oxygen-isotopic composition of fish-apatite and excellently preserved foraminifer tests in the samples from the R0snaεs Clay Formation as well as DSDP Hole 550, we consider the fish-apatite δ1 8θco,2 - t o be a reliable instrument for paleosalinity determination. It is possible that the fish-apatite was exposed to diagenesis and isotopic reequilibration shortly after deposition on the seafloor. This should not, however, reduce the possibility of using δ1 8θco,2 - as an indicator of paleosalinity, because both δ1 8θ and salinity usually are very similar in the uppermost pore water and the overlying water mass. The fish-apatite δ13C values may support that early diagenesis has affected the original isotopic signal. The values seem to be related to the organic carbon content of the sediment as the lowest δ13C values, -4.6%c to -10.5%o, are found in the fish-apatite from the very dark sediment of Hole 913B, whereas the highest δ13C values, +0.6‰ to -1.7%o, are found in the pale, oxidized sediment of DSDP Hole 550.

Description: Ir concentrations and mass accumulation rates from nine deep-sea cores, one from the Atlantic Ocean and eight from the Pacific Ocean, were compiled to evaluate a new technique for determining mass accumulation rates. The technique is based on the large difference of the high Ir abundance in extraterrestrial matter versus the low Ir contents in terrestrial material. Assuming a constant flux of cosmic matter, this difference leads to high Ir concentrations in slowly accumulating sediments, versus low Ir concentration in rapidly accumulating sediments. The method is independent of stratigraphic control, and does not require knowledge of age of the deposit. We note that Ir concentrations in some slowly accumulating sediments are of the same order of magnitude as some of those reported for the Cretaceous-Tertiary boundary event.

Description: Ice rafted debris in high latitude ocean sediments represent a complex record of the changing paleoenvironment of the oceans and, in particular, of the growth and decay of ice sheets along the margins of high latitudes. Physical properties measured on sediment cores taken from the Rockall Plateau were examined to determine the distribution of ice rafted debris layers and Heinrich events in the northeastern North Atlantic. These sediment core records may provide one of the keys to reconstruct the iceberg flow between the northeastern Atlantic and the Norwegian Sea. Magnetic susceptibility (MS) and Gamma Ray Attenuation Porosity Evaluator (GRAPE) density changes of these cores revealed that since about 65 ka, dropstone layers are recorded in both MS and GRAPE data of Rockall Plateau sediments. Rockall Plateau sediments show peaks in physical properties that correlate with Heinrich events (H1, H2, H4, H5, H6). Heinrich layer 3 was not observed. The stratigraphy and physical properties represent the Heinrich layers: H1 = 14–15 ka (MS = 52 μcgs, ϱ = 1.64 g/cm3), H2 = 23 ka (MS = 64 μcgs, ϱ = 1.8 g/cm3), H4 = 41 ka (MS = 53 μcgs, ϱ = 1.75 g/cm3), H5 = 50 ka (MS = 53 μcgs, ϱ = 1.75 g/cm3), H6 = 64 ka (MS = 100 μcgs, ϱ = 1.69 g/cm3). Heinrich events at Rockall Plateau sites point to a northward flow of icebergs in the northeastern Atlantic which may indicate a flow pattern to regions north of 54 °N.

Description: Stable isotope and faunal records from the central Red Sea show high-amplitude oscillations for the past 380,000 years. Positive δ18O anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the Arabian Sea was reduced due to a reduced geometry of the Bab el Mandeb Strait. Salinities as high as 53‰ and 55‰ are inferred from pteropod and benthic foraminifera δ18O, respectively, for the last glacial maximum. During this period all planktonic foraminifera vanished from this part of the Red Sea. Environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level. The foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka. Spectral analysis of the planktonic δ18O record documents highest variance in the orbital eccentricity, obliquity, and precession bands, indicating a dominant influence of climatically - driven sea level change on environmental conditions in the Red Sea. Variance in the precession band is enhanced compared to the global mean marine climate record (SPECMAP), suggesting an additional influence of the Indian monsoon system on Red Sea climates.

Description: Predatory fishes that consume cephalopods have broad spectrum diets that include other groups, such as fishes and crustaceans. Extremely few fish predators feed on cephalopods to the virtual exclusion of other prey, although the tawny nurse shark Nebrius ferrugineus and the sicklefin weasel shark Hemigaleus microstoma may be exceptions, and some deep-living spiny dogfish may feed largely on cephalopods when they are available. Cephalopods are rarely taken in estuaries but they become more important prey on continental shelves and squids may be more dominant prey during their spawning aggregations. Cephalopods generally become more important components of the diets of larger predatory fishes, such as sharks, that inhabit the continental slope and rise. They may be important to pelagic fishes, such as swordfish and tunas in some parts of the oceans. Cephalopods are rarely taken by benthic Antarctic fishes but they are important prey of some pelagic fishes in the Arctic. Abundance and size of potential prey is critical, and the behaviour of both predator and potential prey is decisive, in prey choice. Factors such as prey switching with growth, between areas and at different times, have major influences on the diets of predators. There are extremely few studies that obtain rigorous enough data to allow quantitative analysis of the significance of cephalopods (or other prey) in the diets of predatory fishes and even the most comprehensive studies are not predictive because findings relate only to the time period of each study. Nevertheless, cephalopods are important components of most marine food webs and, furthermore, may play an indirect role in facilitating prey capture to secondary predators, and in providing rejecta to benthic scavengers.

Description: Long-range side-scan sonar (GLORIA) imagery of over 600,000 km² of the Polar North Atlantic provides a large-scale view of sedimentation patterns on this glacier-influenced continental margin. High-latitude margins are influenced strongly by glacial history and ice dynamics and, linked to this, the rate of sediment supply. Extensive glacial fans (up to 350,000 km³) were built up from stacked series of large debris flows transferring sediment down the continental slope. The fans were linked with high debris inputs from Quaternary glaciers at the mouths of cross-shelf troughs and deep fjords. Where ice was slower-moving, but still extended to the shelf break, large-scale slide deposits are observed. Where ice failed to cross the continental shelf during full glacials, the continental slope was sediment starved and submarine channels and smaller slides developed. A simple model for large-scale sedimentation on the glaciated continental margins of the Polar North Atlantic is presented.

Description: High-resolution reflection seismic data obtained around Gran Canaria allow a detailed and consistent correlation of seismic reflectors of the northern and southern Canary Basins with the lithology drilled by DSDP Leg 47A SSE of Gran Canaria, as well as with major phases of volcanic activity on Gran Canaria as mapped onshore. Two prominent reflectors were chosen as marker horizons and correlated with the drilled lithology. the results indicate that reflector R7 above the Miocene volcaniclastic debris flows V1-V3 reflects the shield-building phase of Gran Canaria. Reflector R3 is interpreted as corresponding with the Pliocene Roque Nublo formation. The top of the massive island flank of Gran Canaria, defined by seismically chaotic facies, extends 44 to 72 km off the coast of Gran Canaria. West of Gran Canaria the flank of Tenerife onlaps the steeper and older flank of Gran Canaria, which, in turn, is onlapping the older flank of Fuerteventura to the east in a similar way. Erosional channels, which can also be traced up to 50 km from the area between Gran Canaria and Fuerteventura into the deeper northern basin, have been identified in the bathymetry. The data presented provide new detailed information for modelling the submarine and subaerial evolution of the central Canary Islands of Gran Canaria and Tenerife, i.e. the timing of their shield-building phases and later stages of major volcanic activity, as reflected by the position of prominent seismic reflectors in the seismic stratigraphy.

Description: Colonization structures of the large parasitic foraminifer Hyrrokkin sarcophaga Cedhagen, 1994 on Lophelia pertusa, Acesta excavata and Delectopecten vitreus are described from a deep-water coral reef mound on the mid-Norwegian shelf at 240 to 300 m water depth. Hyrrokkin sarcophaga is the only epibiont which is capable of attaching itself on the soft tissue-protected coral skeleton where it tends to form clusters of 3 to 8 specimens close to the tentacles of Lophelia. The foraminifer excavates a pit up to 1.5 mm deep and etches a straight channel through the skeleton of the host which ends within the soft tissue. In contrast to Lophelia, infested bivalves show a strong wound repair reaction and seal the etched channels by intense calcification. The etching is only performed by adult specimens. Substrate pitting is considered to improve the attachment strength while boring enables the parasite to secure a persistent nutrient source.

Description: Scaled sandbox experiments with high basal friction, simulating the growth of accretionary wedges, display cycles alternating between frontal imbricate thrusting and underthrusting of long, undeformed sheets. By contrast, low basal friction experiments with otherwise similar and constant, initial conditions produce a classic frontal imbricate fan through repeated failure along frontal thrusts. The cyclical behavior observed in high basal friction experiments is expressed by three quantities: (1) the average spacing between frontal thrusts, (2) the advance and retreat of the deformation front, and (3) the frontal slope (Alpha) of the actively deforming wedge. As a long sheet is underthrust, the front is steepened through slumping until the maximum critical angle is reached. Then frontal thrusting resumes and the accretion of imbricate slices builds the wedge forward, thereby lowering the taper to the minimum critical angle. At shallow tapers, a long unit is underthrust and subsequently uplifts, shortens, and steepens the overlying wedge through backthrust deformation, thus completing the cycle. Underthrusting of long units offers a simple mechanism for underplating overlying units. It also provides a possible explanation for temporally and spatially varying wedge geometries in nature, when basal frictions attain 80%–90% of the internal friction.

Description: A knowledge of past changes in the biological productivity of the oceans is important for understanding the interactions between carbon cycling and climate. Phytoplankton productivity in today's oceans can be estimated from the concentrations of chlorophyll in sea water1, but chlorophyll is not preserved in the sediments. Existing proxies for past algal productivity do not represent total productivity; for example, biogenic opal2 reflects the contribution of only part of the phytoplankton community, and the organic carbon record can be subject to contamination from terrestrial inputs2,3. Although chlorins, the pigment-transformation products of chlorophyll, are widespread in Quaternary marine sediments, their potential as proxy measures of past variations in primary productivity has not been convincingly demonstrated. Here we report a high-resolution molecular stratigraphic record of chlorin concentrations over the past 350,000 years in a sediment core from the subtropical Atlantic continental margin. Maxima in the chlorin accumulation rate coincide with significant peaks in the accumulation rates of biogenic opal (at the end of glacial terminations) and organic carbon (between terminations). These results suggest that chlorins, unlike other proxies, can serve as a measure of total primary productivity variations.

Description: Sediment cores containing up to twenty-five ash layers were taken at three sites close to Vesterisbanken Seamount in the Greenland Basin. These ash layers imply frequent eruptions of the volcano within the last 60 ka. The eruptions led to airborne transport and volcaniclastic turbidity flows which transported volcanic glassy and crystalline material from the volcano into the surrounding basin. During the eruption and the transport the glass and the crystal particles were mixed. The glasses range in composition between basanites and phonolites/benmoreites with MgO contents of 8 to 0.65%. The glass analyses follow a distinct trend of fractionation suggesting the crystallization of the phases olivine, clinopyroxene, plagioclase, kaersutite, Cr-spinel, Ti-magnetite and apatite. A strong zonation of clinopyroxene and kaersutite phenocrysts implies mixing processes in the magma system although the liquid compositions do not lie on mixing trends. A geochemical study of the bulk ashes shows that some ash layers possess distinct chemical compositions. The ashes are more evolved than the lavas of the volcano, suggesting fractionation of liquid from crystallized material during the eruption or transport of the ashes. Sixteen layers are statistically combined into four groups, of which several can be correlated from core to core reflecting individual eruptive events.

Description: Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses. The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary. Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts of illite, chlorite, and kaolinite characterize ice-rafted sediments of the “Heinrich layers”. In these sediments smectite crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order, similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase in fine-grained quartz (〈2µm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated at around 10 ka, where a strong increase in smectite of low crystallographic order is detected.

Description: Stable isotope records of demosponges from the Caribbean and Coral Sea are described for the purpose of studying the influence of fossil fuel CO2 on the carbon isotopic composition of dissolved inorganic carbon (DIC) in surface water. The slow-growing sponges precipitate calcium carbonate in isotopic equilibrium with ambient sea water and are used to detect changes in δ13CDIC from pre-industrial times (early 19th century) to the present. We observed similar shapes and ranges in δ13C curves measured on Caribbean specimens collected from water depths of 25, 84 and 91 m as well as a specimen collected in shallow waters off New Caledonia. The records reveal a highly significant correlation with atmospheric δ13CCO2. δ13CDIC values for Caribbean and Coral Sea surface waters were calculated using the δ13C sponge records. While δ13C of atmospheric CO2 decreased by about 1.4‰ from the early 19th century to 1990, δ13CDIC of Caribbean and Coral Sea surface waters decreased by 0.9±0.2‰ and 0.7±0.3‰, respectively. No isotopic equilibrium between surface water DIC and atmospheric CO2 was observed, either during the pre-industrial steady state or during the last 100 years. The lower amount of depletion in the surface water δ13CDIC with respect to the atmospheric anthropogenic signal is explained by the dilution of the surface waters by biologically altered subsurface water DIC. The lower δ13C decrease in the Coral Sea points to a stronger influence of the subsurface water source compared to the Caribbean.

Description: Cruise GOBEX-III was the second expedition mounted by the IOW Marine Geology Group under Project GOBEX to investigate the geochemical and sedimentological environment in the Gotland Basin of the Central Baltic Sea. The cruise concentrated on improving the coverage with shallow seismic profiles (GEOCHIRP sonar), shallow sediment cores (Multicorer) and long gravity and Kasten cores of various depths in the Gotland Deep and adjacent basins. Using acoustic methods, we mapped the local accumulations of mud (Schlick) in basin-normal and along-strike profiles. The accumulations of mud and underlying lacustrine clays were sampled by shallow multi-coring and gravity coring (to 12 m, maximum or 10.5 m recovery). Cores were subsampled onboard ship for porewater, sedimentolngical, and magnetic analyses in shorebased laboratories. A first exploratory survey of sediments was carried out in the Gdansk Basin by seismic soLmdings, surface sediment sampling, and gravity coring. Two gravity cores were taken in the Arkona Basin.

Description: Climatic reconstruction of glacial to interglacial episodes from oxygen isotopes in sediment cores from the Nordic seas is complicated by strong local meltwater contributions to the oxygen isotope changes. Combination of benthic and planktic foraminiferal isotope data with foraminiferal abundances and ice-rafted debris (IRD) allows separation of local and global effects and subdivision of the marine oxygen isotope events 6.2–5.4, which include the last interglaciation, into: (1) a meltwater phase after glacial stage 6, recorded by large amounts of IRD and low foraminiferal abundance, indicating surface water warming; (2) an IRD-free period with high deposition rates of subpolar foraminifera and other CaCO3pelagic components, recognized here as the “full” interglaciation; and (3) a phase with the recurrence of IRD and the demise of subpolar species. Comparison of ice-core records and marine data implies that the global climate during the last full interglaciation and that during the postdeglacial Holocene were similar. The records show no significantly different variations in the proxy data. In contrast, the oxygen isotopes of planktic foraminifera and ice cores indicate significant differences during each of the deglacial transitions (Terminations I and II) that preceded these two interglaciations. These suggest that during Termination II the climatic evolution in the Nordic seas was less affected by abrupt changes in ocean–atmosphere circulation than during the last glacial to interglacial transition.

Description: Microspectralphotometric examinations of various recent pollen point to a different sporopollenin chemistry of the different taxa which is distinguishable by the UV-VIS absorptionspectra. The measurement areas have a diameter of 6 micron, by which several measurements for the spectra control in one pollen grain are possible. Labaratory experiments with chemical treatments as used by palynological preparation, show a clear change in the sporopollenin chemistry whichcould be identified by the absorption spectra. Therefore a new preparation technique for fossil and recent palynomorphs has to be developed to avoid chemical changes. First investigations of recent and fossil Pinus pollen have been clone on material from various facies types and a sediment core. The variations in the absorption spectra of the pollen indicate the different chemical influence of different facies types which could be used for facies analyses. Furthermore, significant changes in the absorption spectra are useful to identify reworked pollen or pollen with a different burial history. Zusammenfassung: Vergleichende mikrospektralphotometrische Untersuchungen der UV-VIS Absorptionsspektren verschiedener rezenter Pollen-Taxa zeigen, daß die Zusammensetzung bzw. Struktur des Sporopollenins bei verschiedenen Taxa variiert und daß diese anhand der Absorptionsspektren klar unterschieden werden kann. Die gemessene Fläche auf den jeweiligen Pollen hat einen Durchmesser von 6 j.lm, so daß mehrere Kontrollmessungen an einem Pollen möglich sind. Laborversuche an rezenten Pollen zeigen, daß chemische Einflüsse (z. B. HN03, Acetolyse) deutlich meßbare Veränderungen in der Struktur des Sporopollenins verursachen. Um Veränderungen des Sporepollenins durch die chemische Probenaufbereitung auszuschließen, wurde eine neue Präparationsmethode für fossile und rezente Palynomorphen entwickelt.

Description: The late Eocene through Oligocene changes in the paleoceanography of the southernmost Indian Ocean have been reconstructed by means of a coarse fraction analysis of closely spaced samples (20 cm = about 20 kyr) from ODP Site 744, Kerguelen Plateau. Surface water productivity, reconstructed from accumulation rates of opal skeletons and benthic foraminifers is low in the early late Eocene, increases at about 36 Ma and shows a sharp increase to maximum values in the earliest Oligocene. In the early late Oligocene it decreases gradually to a minimum and increases again to a maximum in the latest Oligocene. Beside this general trend productivity varies in short-term cycles of a duration of about 400 kyr (340 kyr in the latest Oligocene) with maxima in productivity in warmer Oligocene periods. These productivity variations are reflected by strong variations in carbonate dissolution. Changes in bottom water mass chemistry have been deduced from the degree of carbonate dissolution and it's relation to productivity proxies. Following Kennett and Stott (1990), it is suggested that a proto-antarctic bottom water (proto-AABW) and an overlying warm, saline deep water (WSDW) from low latitudes shifted vertically and latitudinally with time and exerted their influence on the sediments of Site 744. Proto-AABW is detected by means of strong carbonate dissolution when productivity is low. WSDW is detected by means of an excellent carbonate preservation despite high productivity. Terrigenous material occurs as very coarse ice-rafted detritus (IRD) in the late Eocene (167–168.5 mbsf) and after a main shift in oxygen isotopes in the early Oligocene. Very low amounts of 40–125 μm sized mica and very few quartz grains occur only in high productivity periods and at the transition from low to high productivity periods. These occurrences are attributed to wind/current supply during warmer Oligocene intervals.

Description: High-resolution records of carbon and oxygen isotopes and benthic foraminiferal accumulation rates for the Eocene-Oligocene section at Ocean Drilling Program Site 689(Maud Rise, Weddell Sea; paleodepth about 1500 m) were used to infer variations in paleoproductivity in relation to changes in climate and ventilation of the deeper-water column. The benthic foraminiferal abundance and isotope records show short-term fluctuations at periodicities of 100 and 400 ka, implying orbitally driven climatic variations. Both records suggest that intermediate-depth water chemistry and primary productivity changed in response to climate. During the Eocene, productivity increased during cold periods and during cold-to-warm transitions, possibly as a result of increased upwelling of nutrient-rich waters. In the Oligocene, in contrast, productivity maxima occurred during intervals of low d18O values (presumably warmer periods), when a proto–polar front moved to the south of the location of Site 689. This profound transition in climate-productivity patterns occurred around 37 Ma, coeval with rapid changes toward increasing variability of the oxygen and carbon isotope and benthic abundance records and toward larger-amplitude d18O fluctuations. Therefore, we infer that, at this time, temperature fluctuations increased and a proto–polar front formed in conjunction with the first distinct pulsations in size of the Antarctic ice sheet. We speculate that this major change might have resulted from an initial opening of the Drake Passage at 37 Ma, at least for surface- and intermediate-water circulation.

Description: High resolution interdisciplinary analyses of the clay and coarse (〉40 μm) fractions of ODP Leg 113 Site 690 Eocene-Oligocene sediments on the flank of the Maud Rise, provide information on paleoproductivity, water masses, paleoclimate and erosion in the Antarctic range as well as on the cyclicity of these processes. Three time intervals are distinguished: 1. (1) The middle Eocene, characterized by (a) nearly pure smectites, (b) productivity varying between relatively high values in the 42–44 Ma interval to very low values after 42 Ma, and (c) cyclic variations which correspond to changes in clay mineral associations. A warm saline deep water mass is inferred to have protected carbonate shells against dissolution at Site 690. We interpret the abundant mica in the coarse fraction as distributed by intermediate currents. 2. (2) The latest middle Eocene-late Eocene, characterized by low productivity values increasing with time. Kaolinite and illite concentrations also increase. Since the middle/late Eocene boundary mixing in the water column, which starts during a cooling event, causes similar clay mineral assemblages at Site 690 and at Site 689 on top of Maud Rise. 3. (3) The Oligocene, separated from the Eocene by a hiatus, is characterized by high productivity, highly increased amounts of illite and other minerals originating from erosion and physical weathering of Antarctica, and by cyclic variations of clay mineral indices which appear to be synchronous with productivity variations with a 400–450 kyr cyclicity. Six periods of strong carbonate dissolution associated with low productivity levels are attributed to incursions of cold carbonate aggressive bottom water of a “Proto-AABW” type.

Description: The mode of crustal thinning in the southwestern margin of the Iberian Peninsula is investigated along a transect that extends from onshore Iberia to the eastern end of the Horseshoe Abyssal Plain. On onshore areas, the crustal structure has been deduced using wide-angle seismic reflection data, whereas offshore we have used coincident steep and wide-angle reflection data along a NE-SW oriented seismic profile that extends from Cape San Vicente to the Horseshoe Abyssal Plain. In addition, 2D gravity modelling has been performed to validate the crustal structure deduced from seismic data. Our model results reveal that the crust undergoes a strong but continuous thinning from 31 km onshore Iberia to less than 15 km in the Horseshoe Abyssal Plain and that thinning occurs over horizontal distances of about 120 km.