ALBERT

Beschreibung: 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.

Beschreibung: There has been concern about recent temperature trends and the future effects of CO2 concentrations in the atmosphere1,2; but instrumental records only cover a few decades to a few centuries and it is essential that proxy data sources, such as pollen spectra from peats and lake sediments, be carefully interpreted as climate records. Several workers have shown statistically significant associations between the modern pollen rain and climatic parameters, an approach that by-passes the recognition of pollen/vegetation units. Statistically defined equations that associate abiotic and biotic elements are called transfer functions. We report here on the application of transfer function equations to nine middle and late Holocene peat and lake sediment sequences from northern Canada (Fig. 1).

Beschreibung: Organic detritus passing from the sea surface through the water column to the sea floor controls nutrient regeneration, fuels benthic life and affects burial of organic carbon in the sediment record. Particle trap systems have enabled the first quantification of this important process. The results suggest that the dominant mechanism of vertical transport is by rapid settling of rare large particles, most likely of faecal pellets or marine snow of the order of 〉200 μm in diameter, whereas the more frequent small particles have an insignificant role in vertical mass flux4–6. The ultimate source of organic detritus is biological production in surface waters of the oceans. I determine here an empirical relationship that predicts organic carbon flux at any depth in the oceans below the base of the euphotic zone as a function of the mean net primary production rate at the surface and depth-dependent consumption. Such a relationship aids in estimating rates of decay of organic matter in the water column, benthic and water column respiration of oxygen in the deep sea and burial of organic carbon in the sediment record.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: The oligochaete fauna (mainly tubificids and naidids) of a freshwater tidal flat, the "Fiihrmannssand", in the freshwater part of the Elbe Estuary was investigated. The distribution patterns in relation to sediment structure and food availability are discussed. The population dynamics of tubificids and naidids differ significantly. The standing stock of tubificids remains fairly constant throughout the year. Breeding activities take place during the whole year. These data are discussed and compared with those of other surveys where seasonal reproduction activities of tubificids were reported. The naidid population fluctuates considerably in size throughout the year. Abundance maxima are mainly found in spring (Nais spp., Paranais frio). Two annual maxima, in early spring and autumn, are exhibited by Amphichaeta leydigii. Some data are presented on oligochaete endoparasites, especially on Caryophyllaeus laticeps (Cestoda).

Beschreibung: ana marit., 27 (3/6): 145-150, 2 figs.; Frankfurt a. M.] According to the (neo-)Darwinian theory of evolution the appearance of "design" and optimization of biological properties are the results of natural selection and not of teleology. An opti· mization by selection is only possible for entities which are able to reproduce ("units of selection"). The "unit-of-selection"-problem will be discussed in relation to the atomism-holism-continuum of ecological and evolutionary concepts which range from Dawkins' "selfish gene" to LoveJock's "Gaia". Special emphasis will be given to the discussion of the group-selection problem which seems to be the critical breakpoint along this continuum. It will be shown that optimization through natural selection is only possible for units which can multiply and preserve their identity to a sufficient degree through multiplications. Such units are called replicators. Associations, communities, ecosystems and the biosphere do not qualify as replicators.

Beschreibung: Analysis of aeolo-marine dust deposits in the subtropical eastern Atlantic enables the strength of the major wind patterns during the late Quaternary to be evaluated and gives an insight into the climate of North Africa.

Beschreibung: A fundamental issue in marine science is the identification of the factors controlling biological uptake of CO2, in high-nitrate, low-chlorophyll regions. A recent in situ iron fertilization experiment demonstrated that iron limitation is responsible for low phytoplankton stocks in the equatorial Pacific4. Here we show that flavodoxin, a biochemical marker of iron limitation, can be used to map the degree of iron stress in natural populations. Flavodoxin assays along a 900-km east-west transect in the northeastern subarctic Pacific revealed a pronounced increase in iron stress in the region west of the 135° W meridian. Addition of dissolved iron alleviated this stress. Immunostaining of single cells from the most western station showed that flavodoxin is present specifically within the chloroplasts of diatoms. Our approach provides a rapid means of defining the extent of iron stress in the ocean5 and supports the hypothesis that diatoms are iron stressed in the northeast Pacific.

Beschreibung: In Sedimenten aus flachen Bohrungen in der Nordsee wurden gasförmige Kohlenwasserstoffe gefunden. Kohlenstoff- (Methan bis Propan) und Wasserstoff-Isotopanwerte lassen auf eine Mischung von Gasen bakterieller und thermischer Entstehung schließen. Die thermischen Gase sind in größerer Tiefe aus überwiegend mariner organischer Substanz entstanden und in die oberflächennahen Sedimente migriert. [Methane through pentane have been found in sediments from shallow North Sea boreholes. Carbon (methane through propane) and hydrogen (methane) isotope ratlos indicate both bacterial and thermal origins. The gases of thermal origin are interpreted as having been generated at considerable depth from predominantly marine source rocks and then to have migrated into the overlying sediments.]

Beschreibung: Statoliths of cephalopods are small, hard calcareous stones which lie within the cartilaginous skulls of octopods, sepioids and teuthoids1. Fossil statoliths, clearly belonging to genera which are alive today, have previously been described from 11 Cenozoic deposits spanning from the Eocene to the Pleistocene in North America2–5. Such statoliths are of particular interest because they provide a means of studying the evolution of living cephalopod groups which have no calcareous shells, including the cosmopolitan and numerous teuthoids and octopods. Here, the first cephalopod statoliths to be recognized in European deposits are described and identified as Loligo sp. They are compared with the North American fossil Loligo species and statoliths removed from the two living Loligo species of Europe.

Beschreibung: Die "Siegener" und die "Mayener Hauptüberschiebung", die in der Umgebung des Laacher Sees von mächtigem Bims überdeckt sind, gehören zu einer steil einfallenden, ca. 120 km langen Aufschiebung, die als "Siegener Hauptaufschiebung" bezeichnet wird. An ihr sind hier Hunsrückschiefer s.l. auf Serien der sandigen Siegener Normalfazies aufgeschoben worden. Ihr Verlauf wurde rekonstruiert anhand einer gezielten Analyse von Einzelaufschlüssen des paläozoischen Sockels und von Xenolithen der jungquartären Laacher Bimstuffe. Diese enthalten Auswürflinge von Gesteinen der sandigen Siegener Normalfazies einerseits und der Hunsrückschiefer andererseits. Daraus ergibt sich, daß die Bimstuffe aus mehreren Eruptionszentren nördlich und südlich der Hauptaufschiebung und nicht nur aus dem Laacher Vulkan gefördert wurden.

Beschreibung: The dye Sirius Red binds to collagens types I, II and III, giving red-colored products in which the bound dye is proportional to the amount of collagen present. Several other proteins also bind Sirius Red, in amounts 30-50 times less than collagen, on a weight basis. Because of this preferential binding to collagen, Sirius Red may be used for its quantitation even in presence of other proteins, as it occurs, for instance, in the culture medium of various types of cultured cells. When incubated at room temperature with bacterial collagenase, the Sirius Red-collagen complex is rapidly degraded while it is resistant to mammalian collagenase, trypsin and pepsin. Thus, the release of the bound dye may be used for quantitation of bacterial collagenase activity.

Beschreibung: Pteropod shell morphologies can be explained by neotenic extension of larval features observed in benthic forms, such as the sinistral coiling of Architectonacea and the ornamentation patterns of Tonnacea, into the adult shell of permanently planktonic living snails. Presented models suggest derivation of pteropods from primitive prosobranch mesogastropods of the Late Paleozoic, rather than from opistobranchs.