ALBERT

Description: The internal and external North Atlantic Sector variability is investigated by means of a multimillennial control run and forced experiments with the Kiel Climate Model (KCM). The internal variability is studied by analyzing the control run. The externally forced variability is investigated in a run with periodic millennial solar forcing and in greenhouse warming experiments with enhanced carbon dioxide concentrations. The surface air temperature (SAT) averaged over the Northern Hemisphere simulated in the control run displays enhanced variability relative to the red background at decadal, centennial, and millennial timescales. Special emphasis is given to the variability of the Meridional Overturning Circulation (MOC). The MOC plays an important role in the generation of internal climate modes. Furthermore, the MOC provides a strong negative feedback on the Northern Hemisphere SAT in both the solar and greenhouse warming experiments, thereby moderating the direct effects of the external forcing in the North Atlantic. The implications of the results for decadal predictability are discussed.

Description: The distribution of tunnel valleys in the German North Sea is mapped from more than 25 000 km of 2D and 3000 km2 of 3D seismic data. The number of identified tunnel valleys is much higher than previously known from former studies. Areas which could not be mapped so far because of a lack of data are now studied. The new map reveals that tunnel valleys are common features in the German North Sea, but areas remain where they are absent. At least three different generations of valley formation can be differentiated in the 3D seismic data sets. The mapped valleys have widths of up to 8 km and lengths of up to 66 km. They are incised down to 400 m into the Neogene sediments and cut-and-fill structures within the tunnel valleys are imaged by high-fold 2D seismic data indicating a re-use of existing tunnel valleys during subsequent ice advances and retreats. The fill of large tunnel valleys shows a typical pattern with a chaotic seismic facies at the bottom overlain by a high amplitude reflector and sub-horizontal to inclined low amplitude reflectors. This pattern correlates with results from on- and offshore studies of tunnel valley infills and suggests coarse-grained sediments at the base overlain by fine-grained glaciomarine and/or glaciolacustrine sediments. The tunnel valleys in the eastern and central German North Sea are probably of Elsterian age, because the surrounding Dutch, Danish and onshore German tunnel valleys are of inferred or proven Elsterian age.

Description: The Cenomanian–Turonian Boundary Event (CTBE) is reflected by one of the most extreme carbon cycle perturbations in Earth's history and is characterized by the widespread occurrence of sediments indicating oxygen deficiency in oceanic waters (Oceanic Anoxic Event 2 = OAE 2). At Wunstorf (northern Germany) the CTBE is represented by a 26.5 m thick sedimentary succession consisting of rhythmically bedded laminated black shales, dark organic-rich marls and marly limestones yielding abundant micro- and macrofossils, making the locality particularly well suited to serve as an international standard reference section for the CTBE. In 2006 a newly drilled continuous core recovered 76 m of middle Cenomanian to middle Turonian sediments. A high-resolution carbonate δ13C curve derived from core samples resolves all known features of the positive δ13C anomaly of OAE 2 with high accuracy. Throughout the middle Cenomanian – middle Turonian succession, the δ13C curve shows numerous small-scaled positive excursions, which appear to be cyclic. High-resolution borehole geophysics and XRF core scanning were performed to generate two time series of gamma-ray data and Ti concentrations for the CTBE black shale succession. Hierarchical bundling of sedimentary cycles as well as spectral analysis and Gaussian filtering of dominant frequencies reveal cycle frequency ratios characteristic for short eccentricity modulated precession (100 kyr, 21 kyr). This new orbital time scale provides a time estimate of 430–445 kyr for the duration of OAE 2 and refines the existing orbital age models developed at localities in the English Chalk, the Western Interior Basin and the Tarfaya Basin. Based on the new age model and high-resolution carbon isotope correlation, our data allow for the first time a precise basin-wide reconstruction of the palaeoceanographic modifications within the European shelf sea during OAE 2.

Description: Sky observations by means of digital full sky imagers enable a continuous monitoring and archiving of the state of the atmosphere. A direct application is the estimation of the total amount of clouds with a very high temporal resolution. From simple methods of image analysis, we used the full sky imager additionally as a sunshine recorder to replace complex pyrheliometric and pyranometric measurements for detecting direct solar irradiation. The Meridional Ocean Radiation Experiment MORE has realized four transatlantic research cruises with a special focus on the surface radiation budget, remote sensing of clouds and automated sky monitoring. This dataset was used to study different parametrizations of solar downward radiation at the sea surface based on standard meteorological measurements. It was found that the parameterization by Zillman (1972) provided the best performance for the use with operational meteorological data. Furthermore, this parametrization was modified to create a fast responding parametrization to reproduce short-term fluctuations of the insolation. This new parametrization has been applied to independent datasets. It is shown that based on measurements of a few weeks it was not possible to reduce the overall bias of parameterized insolation significantly due to the fact that the parametrization does not consider the optical thickness of clouds. The standard deviation between calculated and measured flux has been reduced by 4%. The performance for separated broken cloud conditions was improved significantly.

Description: The impact of cloudiness on the shortwave downwelling radiation (SDR) at the surface is investigated by means of collocated pyranometer radiation measurements and all-sky imager observations. The measurements have been performed in Westerland, a seaside resort on the North Sea island of Sylt, Germany, during summer 2004 and 2005. A main improvement to previous studies on this subject resulted from the very high temporal resolution of cloud images and radiation measurements and, therefore, a more robust statistical analysis of the occurrence of this effect. It was possible to observe an excess of solar irradiation compared to clear sky irradiation by more than 500 W/m2, the largest observed excess irradiation to our knowledge so far. Camera images reveal that largest excess radiation is reached close to overcast situations with altocumulus clouds partly obscuring the solar disk, and preferably with cumulus clouds in lower levels. The maximum duration of the enhancements depends on its strength and ranges from 20 seconds (enhancements 〉 400 W/m2) up to 140 seconds (enhancements 〉 200 W/m2).

Description: Devonian-Carboniferous sedimentary and volcanic rocks are exposed in the Badenweiler-Lenzkirch Zone (BLZ) of the Southern Schwarzwald and in the Southern Vosges (Central Europe). Several lithostratigraphic units are recognized. Sedimentary or tectonic relations between some of the units can be realized by comparing sedimentary and volcanic facies associations as well as petrographic and geochemical datasets. During the Variscan orogenesis the sediments were deposited in different kinds of basins along an active margin setting. Their deformation was studied in the Markstein area of the Southern Vosges and is presented here in detail. Some arguments favour a northward underthrusting of a narrow and oceanic pre-Upper Devonian back-arc basin beneath the crystalline units of the Central Vosges and Schwarzwald. Accretion of continental crust continued from the Upper Devonian to the late Lower Carboniferous along with a characteristical evolution of a deep marine retro-arc foreland basin. It has accumulated about 3500 m of turbidite sandstones, shales and conglomerates of volcano-plutonic origin, assembling now the Markstein Group in the Southern Vosges. To the south of the Markstein Group, deep marine mud-rich turbidite systems and a shallowing-upward succession of fluvio-deltaic sediments filled in the Oderen Basin, which subsided in the late Tournaisian and early Viséan. A subduction type volcanism occurred in form of tholeiitic basalts, K-calcalkaline island arc andesites and continental arc sandstones. In contrast to former models, a genetical relationship between the Markstein and the Oderen Group is rejected here. Instead, different subduction systems in space and time have caused the development of the active margin basins. The Variscan deformation of the exposed sedimentary units started in the upper Viséan. Structural analysis of kinematic indicators and macroscopic fabrics in the Markstein Group give evidence for thrusting and dextrally transpressive shearing, forming a positive flower structure along the southern border of the Central Vosges crystalline units. This was broadly synchronous with dextrally transpressive deformation along the Lalaye-Lubine/Baden Baden fault at the northern border of the Central Vosges and Schwarzwald and along the "Transition Complex" between the Central and the Southern Schwarzwald. The high-K-calcalkaline Metzeral granite intruded postkinematically into the principal displacement zone and has a position similar to the dextrally sheared Randgranite association along the northern border of the BLZ. A juxtaposition between the Oderen and the Markstein Groups was achieved in the upper Viséan due to the dextral transpressive motion along the ESE-trending Markstein Fault. The exhumation of high grade metamorphic rocks of the Central Vosges and Schwarzwald during the upper Viséan is discussed in the context of long lasting accretionary tectonics and the two-sided dextral transpression, favouring crustal extrusion as a main exhumation process. A thorough examination of the supracrustal rocks and their mode of deformation in the Southern Vosges helps us to determine the relationships with the BLZ and contributes also to the paleogeographic reconstruction of the Armorica - Proto-Alpine - Gondwana connection.

Description: Like the larger Cyclades Islands (e.g. Naxos, Paros, Ios) the Small Cyclades Islands form part of the Attic-Cycladic crystalline basement belt. Subduction in the Paleogene was associated with high-pressure metamorphism, followed by a Barroviantype overprint, local partial melting and granitic plutonism in the Neogene. On the islands of Iraklia and Schinoussa Neogene metamorphism did not exceed mid-greenschist grade, and there are some well preserved older high-pressure/low temperature metamorphic assemblages. The rocks and structural geology of both islands had previously not been analysed in detail. Rocks present are calcite and dolomite marbles, in part with preserved paleosoils (metabauxites and metalaterites), and a suite of metapelitic schists with associated glaucophane schists and piemontite quartzites. There is a ductile deformation history comprising four events. The two older ones (D1, D2) are associated with high strains, and have resulted in a subhorizontal foliation, a N-S trending stretching lineation, and recumbent isoclinal folds with variable axial orientations. At least D1 is bracketed by the growth of glaucophane, with uncertain kinematics. D2, syn-blueschist grade on Iraklia, however, has a clear top-to-north sense of shear. D3 and D4 caused upright folds with N-S and E-W trending fold axes, respectively. This is evidence for late, two-phase horizontal shortening. As the deformed rocks show only a slight static metamorphic overprint, we have estimated flow stresses from dynamically recrystallized grain sizes of quartz and calcite. Coincident flow stress estimates are 28-62 MPa in quartzites, and 31-56 MPa in the marbles. Together with syntectonic temperature extimates, and applying published flow laws, this leads to estimated deformation rates on the order of 10−12 to 10−14 sec−1. Even though deformation history and kinematics is very similar to that on Naxos Island, the clear relation of the earlier part to high-pressure metamorphism on Iraklia and Schinoussa speaks in favour of a subduction-related setting here. This is in contrast to the later formation of metamorphic core complexes in the north (Naxos) and south (Ios).

Description: The control exerted by some invertebrates on the calcium carbonate polymorph produced is intriguing but not understood. Mytilus edulis shells, with the abrupt polymorph switch within their valves from an outer calcite to inner aragonite layer, are excellent examples of this phenomenon. Detailed crystallography of intact valves using Electron Backscatter Diffraction (EBSD) is considered in the context of quantitative chemical analyses by electron microprobe. Apart from the outer 40 μm, individual crystals that comprise the calcite layer of M. edulis differ from each other in terms of misorientation by less than 10°. Similar uniformity occurs in the inner aragonite layer with notable 'mineral bridging' between tablets of aragonite nacre. The first-formed aragonite laminae are submicron thickness and the subsequent laminae of uniform 1 μm thickness.Variations in chemical composition through the two valves correspond in part with the distribution of the two polymorphs. Magnesium is present in notably higher concentrations within calcite than aragonite. However, the Mg2+ concentration in calcite is not uniform and increases with growth before decreasing at the polymorph switch. Sodium concentrations decrease steadily through the calcite layer. The aragonite layer is compositionally more uniform. Sulphur is not a good proxy for organic content in this system because it does not reflect the higher organic content of the aragonite. Sector zoning is not responsible for the element distribution seen here while differences in crystal size and association with organic components remain as possible explanations.

Description: Currently it is still extremely difficult to adequately sample populations of microalgae on sediments for large-scale biomass determination. We have now devised a prototype of a new benthic sensor (BenthoFluor) for the quantitative and qualitative assessment of microphytobenthos populations in situ. This sensor enables a high spatial and temporal resolution and a rapid evaluation of the community structure and distribution. These determinations are based on the concept that five spectral excitation ranges can be used to differentiate groups of microalgae, in situ, within a few seconds. In addition, because sediments contain a lot of yellow substances, which can affect the fluorescence and optical differentiation of the algae, the device was equipped with a UV-LED for yellow substances correction. The device was calibrated against HPLC with cultures and tested in the field. Our real-time approach can be used to monitor algal assemblage composition on sediments and is an ideal tool for investigations on the large-scale spatial and temporal variation of algal populations in sediments. Apart from the differentiation of algal populations, the BenthoFluor allows instantaneous monitoring of the chlorophyll concentrations and determination of which algae are responsible for this on the uppermost surface of sediments in the field and in experimental set-ups.

Description: Investigations on the littoral microphytobenthos populations of lakes are very rare. Based on new sampling techniques, allowing the undisturbed sampling of sublittoral sediments, we present information on limnic microphytobenthos populations of the Schöhsee in Northern Germany (10° 26′ E, 54° 13′ N). Investigations on microphytobenthic communities at a sandy and a muddy site provided new insights into the community structure and seasonal variations of limnic benthic microalgae. The microphytobenthos was characterised by low chlorophyll-a contents (0.16 μg cm−2 to 0.74 μg cm−2) and low cell numbers (25 cells cm−2 to 266 cells cm−2). Both sites showed similar patterns in terms of algal biomass and seasonality; no site-specific characteristics were observed. The productivity of the sediment microflora in the Schöhsee was low and most likely related to the mesotrophic lake character and to reduced light conditions in the near-shore sublittoral. The algal communities at both sites showed high diversity, distinct seasonality and succession patterns with shifts in community composition in spring, summer and autumn. The community was dominated by Fragilaria spp., Navicula spp., Nitzschia spp., and Stauroneis spp. in spring shifting to a Stauroneis spp.-dominated community in summer. In autumn the populations were dominated by Navicula spp., Nitzschia spp., and Stauroneis spp. Overall, the taxonomic composition showed a dominance of prostrate diatoms, whereas cyanobacteria, green algae and erect diatoms occurred rarely and with low abundance. Thus, the sediment microflora of the Schöhsee can be characterized as a flat, two-dimensional community.

Description: One important pathway of the nitrogen cycle in aquatic environments is the oxidation of ammonia to nitrite by ammonia-oxidizing bacteria (AOB). In this study the composition of AOB communities was compared between fresh (lakes Plusssee and Schöhsee) and brackish (Baltic Sea) water at two different levels: i) between environments and ii) within different depths in each environment. Changes in the community structure were studied by denaturing gradient gel electrophoresis (DGGE) and clone libraries of PCR products of 16S rRNA genes (rDNA) from AOB of the beta subclass of proteobacteria. Each environment displayed a particular DGGE band pattern. In Plusssee and the Baltic Sea, the differentiation of communities in epi- and metalimnion from those in hypolimnion coincided with a distinct stratification of the water column. In Schöhsee with an aerobic hypolimnion, the communities at all depths were similar. AOB communities in sediments were different from those in the water column. The composition of clone libraries showed the presence of specific Nitrosomonas and Nitrosospira-like sequences in each environment and habitat.

Description: The global sediment mass-age distribution indicates large variations in the rates of carbonate sedimentation through time. The largest mass of carbonate deposited during the entire history of the earth was produced during the Cambrian, possibly following on an episode of phosphogenesis in the Late Precambrian. A second major episode occurred during the Late Devonian, probably reflecting the invasion of land by plants that altered the rock-weathering and soil-forming regimes. Other lesser pulses of carbonate deposition occurred in the Late Permian, Triassic, and Cretaceous. A shift in the locus of carbonate deposition from shallow waters to the deep sea occurred during the Cretaceous.

Description: At Aqaba in the Northern Gulf of Aqaba, Red Sea, the stable oxygen isotope record of a Por#es lutea coral colony was studied. From a vertical and a horizontal core two parts from the base of the colony (10 years of coral growth), and two parts from the living surface (12 years of coral growth) were analysed with a monthly sampling resolution. The results show that seasonality of sea surface temperatures (SST) in the northem GulfofAqaba has increased since the early 19th century, mainly due to higher summer temper- atures. 8~80-ratios indicate that SST increased by at least 1.3~ Horizontal and vertical cores display dif- ferent variations in the modern parts, probably caused by the very shallow water depth of the youngest part of the vertical core.

Description: Repeatable species dominance patterns across nutrient ratio gradients are found both in culture competition experiments and in natural waters. However, the mechanisms behind these similar patterns need not to be identical. In chemostat experiments, such patterns are caused by the two-way competitive interactions between contemporaneously occurring organisms. Nutrient competition may be important in situ too, but there is an additional effect of early successional species influencing the nutrient environment for later successional species, without being influenced themselves by their successors.

Description: Cyanobacteria are important constituents of most aquatic ecosystems on earth, and planktonic forms frequently show mass development in lakes and estuaries. Despite extensive scientific efforts directed towards research on cyanobacteria, a comprehensive theory explaining their success is lacking. Because cyanobacteria comprise a diverse group of organisms, it is concluded that any analysis of the conditions leading to cyanobacterial dominance in pelagic ecosystems should consider at least three different subgroups, classified based on presence or absence of (i) buoyancy regulation and (ii) the ability to fix molecular nitrogen. In this review, nine single-factor hypotheses regarding regulation of cyanobacterial development are examined against the background of physiological and ecological characteristics of these organisms. Special emphasis has been put on understanding differences in nitrogen metabolism between cyanobacteria and algae which directly relate to a hypothesis conceming inorganic nitrogen forms and cyanobacterial success previously presented by our research group. The review lends support to the theory that cyanobacteria have a low competitive ability for nitrate compared with algae and a high ability to compete for ammonium, particularly under nitrogen-limiting conditions. Finally it is concluded that to understand cyanobacterial devlopment and how high Standing Stocks in pelagic ecosystems are maintained requires parts o f all the single-factor hypotheses initially presented.

Description: The density of seawater is a complex function of temperature, salinity, and pressure. Because of the non-linearity of the equation of state of seawater, the densities of sea waters having the same temperature and the same salinity differences (with respect to the mean salinity of the ocean) will vary with the mean salinity of the ocean. Although this strange property of seawater is evident in a plot of the equation of state, it has never been considered in trying to reconstruct ancient ocean circulation. These differences in the density field may have caused the ocean to respond differently to atmospheric forcing in the past. The different response may hold the key to understanding "ocean anoxic events" and episodes of large-scale burial of organic carbon and production of petroleum source rocks.

Description: The Late Cretaceous was much warmer than today. There was no significant ice at high latitudes, meridional thermal gradients were low, and continental interiors remained warm during winter. Late Cretaceous atmospheric C02 concentrations were about four times greater than today and an enhanced "greenhouse" effect contributed to the overall warmth of the Late Cretaceous. However , increases in atmospheric C02 tend to increase temperatures at all latitudes and do not explain the very low thermal gradients recognized in the geologic record. Increased poleward ocean heat transport has been cited as a mechanism for maintaining low meridional thermal gradients during the Cretaceous. However , ocean heat transport values larger than the present day are difficult to reconcile. In addition, low meridional thermal gradients suggest sluggish atmospheric circulation, implying that the advection of heat from the warm oceans into the continental interiors was limited. In general, paleoclimate simulations using Atmospheric General Circulations Models (AGCMs) have not been successful in simulating the low meridional thermal gradients and warm winter continental interiors of the Cretaceous, forcing the concept of "equability" to be questioned. Until recently, the physical effects of vegetation on pre-Quaternary climates have largely been ignored. Terrestrial ecosystems influence global climate by affecting the exchange of energy, water, and momentum between the land surface and the atmosphere. In a new approach to pre-Quaternary paleoclimate modeling, Campanian (80 Ma) climate and vegetation have been simulated using a global climate model (GENESIS Version 2.0), coupled to a predictive vegetation model (EVE), resulting in a realistic simulation of Late Cretaceous climate. The predicted distribution of Late Cretaceous vegetation played an important role in the maintenance of low meridional thermal gradients, polar warmth, and equable continental interiors. High latitude forests reduced albedo, especially during snowcovered months, and increased net surface radiation and latent heat flux.

Description: In this study, the impact of oceanic data assimilation on ENSO simulations and predictions is investigated. The authors’ main objective is to compare the impact of the assimilation of sea level observations and three-dimensional temperature measurements relative to each other. Three experiments were performed. In a control run the ocean model was forced with observed winds only, and in two assimilation runs three-dimensional temperatures and sea levels were assimilated one by one. The root-mean-square differences between the model solution and observations were computed and heat content anomalies of the upper 275 m compared to each other. Three ensembles of ENSO forecasts were performed additionally to investigate the impact of data assimilation on ENSO predictions. In a control ensemble a hybrid coupled ocean–atmosphere model was initialized with observed winds only, while either three-dimensional temperatures or sea level data were assimilated during the initialization phase in two additional forecast ensembles. The predicted sea surface temperature anomalies were averaged over the eastern equatorial Pacific and compared to observations. Two different objective skill measures were computed to evaluate the impact of data assimilation on ENSO forecasts. The authors’ experiments indicate that sea level observations contain useful information and that this information can be inserted successfully into an oceanic general circulation model. It is inferred from the forecast ensembles that the benefit of sea level and temperature assimilation is comparable. However, the positive impact of sea level assimilation could be shown more clearly when the forecasted temperature differences rather than the temperature anomalies themselves were compared with observations.

Description: This paper presents trace element and Sm-Nd isotope data on the Mönchalpgneiss in order to compare the geochemistry of the two polymetamorphic igneous suites that comprise over 30% of the Austroalpine Silvretta nappe. The first are the so-called "Younger Orthogneisses" of the "Fliielagranitic Association" and the second are the "Older Orthogneisses" including the Mönchalpgneisswhich are associated with metagabbros, metadiorites, metatonalites and metagranitoids. U-Pb zircon results from the Mönchalpgneiss are indicative of anatectic processes in late Cambrian to Ordovician times. A volcanic-arc (VA) tectonic environment during intrusion explains the direct association of gabbroic and metagranitoid rocks in the Engadine area. This model is in line with the distribution of major, trace and rare earth elements in these anatectic rocks. However, the significance of the geochemical results remains ambiguous, since the average continental crust and paragneisses of the Silvretta also show VA-type signatures in the respective diagrams. Nd model ages on four Mönchalpgneiss whole-rock samples from the type locality are closely grouped around 1.70 Ga, which is a commonly obtained value for European continental crust. This age is interpreted to be the result of a homogeneous mixture of different crustal components

Description: In this paper the performance of the global coupled general circulation model (CGCM) ECHO-2, which was integrated for 10 years without the application of flux correction, is described. Although the integration is rather short, strong and weak points of this CGCM can be clearly identified, especially in view of the model's performance of the annual cycle in the tropical Pacific. The latter is simulated with more success relative to the earlier version, ECHO-I. A better representation of the low-level stratus clouds in the atmosphere model associated with a reduction in the shortwave radiative flux at the air-sea interface improved the coupled model's performance in the southeastern tropical oceans, with a strongly reduced warm bias in these regions. Modifications in the atmospheric convection scheme also eliminated the AGCM's tendency to simulate a double ITCZ, and this behavior is maintained in the CGCM simulation. Finally, a new numerical scheme for active tracer advection in the ocean model strongly reduced the numerical mixing, which seems to enhance considerably the level of interannual variability in the equatorial Pacific. One weak point is an overall cold bias in the Tropics and midlatitudes, which typically amounts to 1°C in open ocean regions. Another weak point is the still too strong equatorial cold tongue, which penetrates too far into the western equatorial Pacific. Although this model deficiency is not as pronounced as in ECHO-1, the too strong cold tongue reduces the level of interannual rainfall variability in the western and central equatorial Pacific. Finally, the interannual fluctuations in equatorial Pacific sea surface temperatures (SSTs) are too equatorially trapped, a problem that is also found in ocean-only simulations. Overall, however, the authors believe that the ECHO-2 CGCM has been considerably improved relative to ECHO-1.

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: 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: 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: 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.

Description: 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.]

Description: The chemical composition of sediments from the Reykjanes Ridge is controlled by allochthonous and autochthonous processes. The surface sediments are characterized by relatively high contents of calciumoxide and strontium. Calcium and strontium dominate in the carbonate phase due to the high content of biogenic carbonate. A high percentage of iron and manganese are bound to oxides and hydroxides. An indication of hydrothermal activity was not observed. A considerable portion of adsorbed barium is transported in clay minerals. The higher amounts of aluminium in glacial sequences indicate an enhanced input of terrigenous material; the increase of stable bonding elemen~s points toward the large influence of detrital minerals. The distinct differences in the bonding characteristics of elements in these marine sediments in comparison to fluvial and coastal - deposits could be due to the different environmental conditions.

Description: The seasonal cycle over the tropical Pacific simulated by 11 coupled ocean–atmosphere general circulation models (GCMs) is examined. Each model consists of a high-resolution ocean GCM of either the tropical Pacific or near-global means coupled to a moderate- or high-resolution atmospheric GCM, without the use of flux correction. The seasonal behavior of sea surface temperature (SST) and eastern Pacific rainfall is presented for each model. The results show that current state-of-the-art coupled GCMs share important successes and troublesome systematic errors. All 11 models are able to simulate the mean zonal gradient in SST at the equator over the central Pacific. The simulated equatorial cold tongue generally tends to be too strong, too narrow, and extend too far west. SSTs are generally too warm in a broad region west of Peru and in a band near 10°S. This is accompanied in some models by a double intertropical convergence zone (ITCZ) straddling the equator over the eastern Pacific, and in others by an ITCZ that migrates across the equator with the seasons; neither behavior is realistic. There is considerable spread in the simulated seasonal cycles of equatorial SST in the eastern Pacific. Some simulations do capture the annual harmonic quite realistically, although the seasonal cold tongue tends to appear prematurely. Others overestimate the amplitude of the semiannual harmonic. Nonetheless, the results constitute a marked improvement over the simulations of only a few years ago when serious climate drift was still widespread and simulated zonal gradients of SST along the equator were often very weak.