Petrographische und magnetische Untersuchungen an einem Vorkommen von Basalt und einem genetisch damit verbundenen Quarzit im Mittleren Buntsandstein der Eifel

Zusammenfassung Die plateauf?rmige Kuppe des Stromberges südlich von Blankenheim (Eifel) wird als lokal begrenzter Einkieselungshorizont im Mittleren Buntsandstein erkannt. Die zur Kl?rung seiner Genese durchgeführten petrographischen und magnetischen Untersuchungen haben ergeben, da? der Stromberg von einem ann?hernd pilzf?rmigen Vorkommen von Olivin-Nephelinit unterlagert ist. Es wird wahrscheinlich gemacht, da? über dem fast zentral gelegenen Zufuhrkanal durch Einwirkung von postvulkanischen alkalischen L?sungen und erh?hter W?rmeausstrahlung im Buntsandstein eine L?sung von Kiesels?ure erfolgte, die nach Abklingen dieser Einwirkungen im Grundwasserbereich dann zur Bildung eines Einkieselungshorizontes führte. Herrn Prof. Dr.Carl W. Correns zum 70. Geburtstag gewidmet.     

Phase equilibria and compositions of Fe-Mg-Al minerals and melts in water-saturated peraluminous granitic systems

Phase assemblages and phase compositions were studied experimentally in water-saturated, biotite-bearing peraluminous granitic melts as a function of alumina excess and temperature. The runs were performed at 2 and 5 kbars under NNO buffer. Biotite was stable only in composition containing 5% of normative corundum; it coexisted with cordierite and hercynite at 2 kbars and with hercynite at 5 kbars. In composition containing 10% of normative corundum biotite was not observed; abundant cordierite and hercynite were the only Fe-Mg-Al minerals. These relationships show that, at constant pressure, the amount of cordierite increases with increasing excess of alumina. Simultaneously the stability of biotite decreases due to preferential partitioning of Mg into cordierite and Fe into biotite. Besides the distribution of Fe, Mg and Al among the coexisting solid phases, solubility of these elements in the melts is given. Below 900° C melts are poor in iron and magnesium and correspond, in terms of these elements, to leucogranites. It is suggested that the leucogranitic magmas, such as parental magmas of European Hercynian and Himalayan leucogranites, must have been formed through highly efficient separation of partial melt from restite, in which ferromagnesian components are concentrated. Peraluminous granites rich in ferromagnesian minerals originate supposedly from restite-bearing magmas.     

Sidescan sonar imagery of widespread fossil and active cold seeps along the central Chilean continental margin

The central Chilean subduction zone between 35°S and 37°S was investigated in order to identify, document and possibly understand fluid flow and fluid venting within the forearc region. Several areas were mapped using multibeam bathymetry and backscatter, high-resolution sidescan sonar, chirp subbottom profiling and reflection seismic data. On a subsequent cruise ground-truthing observations were made using a video sled. In general, this dataset shows surprisingly little evidence of fluid venting along the mid-slope region, in contrast to other subduction zones such as Central America and New Zealand. There were abundant indications of active and predominantly fossil fluid venting along the upper slope between 36.5°S and 36.8°S at the seaward margin of an intraslope basin. Here, backscatter anomalies suggest widespread authigenic carbonate deposits, likely the result of methane-rich fluid expulsion. There is unpublished evidence that these fluids are of biogenic origin and generated within the slope sediments, similar to other accretionary margins but in contrast to the erosional margin off Central America, where fluids have geochemical signals indicating an origin from the subducting plate.     

Gedrillte Asteriten im Rosenquarz und Granat

Ohne Zusammenfassung     

I. Erdöl Ergebnisse der erdölgeologischen Erforschung Nordwestdeutschlands 1932–1947, ein Überblick

Ohne Zusammenfassung     

Lineament-Tektonik in Nordost-Brasilien

Zusammenfassung An Hand einer Struktur-Karte von Nordost-Brasilien wird die tektonische Entwicklung des ostbrasilianischen und von Teilen des zentralbrasilianischen Schildes sowie der zwischen beiden gelegenen Sedimentärbecken dargestellt. Es wird die Bedeutung aufgezeigt, die mehrere Lineamente auf die Streichrichtungen des Grundgebirges haben. Im ostbrasilianischen Schild riefen sie Virgationen hervor, die den Raum für die zentralen Sediment-Becken ausweiteten. Andere Lineamente begünstigten die Umbiegung des S-N gerichteten zentralbrasilianischen in das E-W gerichtete Süd-Amazonas-Grundgebirge, und wiederum andere die des ostbrasilianischen in das Nord-Amazonasbzw. Guayana-Grundgebirge. Infolge dieser Umbiegungen ergibt sich ein Parallelismus des zentralen und Orientalen Grundgebirges mit dem Verlauf der Nordost- und Nordküste Brasiliens. An strukturell besonders bedeutsamen Umbiegungen formten sich Blockfalten-Orogene, so in dem Gebiet von Cabrobo am São Francisco und in der Küstenregion von Ceará.

---

A structural map of the north-east of Brazil shows the tectonic evolution of the eastern and part of the central Brazilian shield and the sedimentary basins enclosed by them. Some lineaments are a very important factor of the strike of the crystallin basement. On the eastern shield they formed virgations enlarging the sedimentary basin of the center. — Other lineaments promoted the curvations of the precambrian central shield from the direction S-N to the direction E-W, the Amazonian, some other promoted the curvations of the precambrian of the eastern shield into the Guiana direction. In consequence of these curvations results a parallelism of the direction of the central and eastern shield to the N-E and N coast of Brazil. There were formed folded blocks on structural very important points of the curvations, so at Cabrobó, situated at the riverbasin of Rio São Francisco and in the coast region of Ceará.

---

Resumo Apresentamos um mapa estrutural do Nordeste brasileiro que mostra a situação tectônica do trecho oriental e de parte do central do escudo brasileiro, e das bacias sedimentárias nêstes intercaladas. Releva-se o efeito importante de alguns lineamentos em relação à direçâo do embasamento cristalino. No escudo oriental criaram virgações, que alargaram as bacias sedimentárias no centro. Outros lineamentos favoreceram a curvatura do pré-cambriano do escudo central da direção S.-N. à direção E.-W., amazônica, e outros a curvatura do précambriano do escudo oriental à direção guianense. Em consequência dêsse movimento resulta certo paralelismo das direções dos escudos central e oriental com a costa nordeste e norte do Brasil. Nas curvaturas mais importantes formaram-se blocos dobrados e falhados, como p.ex. na área de Cabrobó no ponto mais setentrional do rio São Francisco e na região norte do Ceará.

---

, . . - , - - . .

     

Comparing an estimate of seabirds at risk to a mortality estimate from the November 2004 Terra Nova FPSO oil spill

On 21 November 2004, about 1000 barrels of crude oil were accidentally released from the Terra Nova FPSO (floating production, storage and offloading) onto the Grand Banks, approximately 340 km east-southeast of St. John's, Newfoundland. We estimated the number of vulnerable seabirds (murres (Uria spp.) and dovekies (Alle alle)) at risk from this incident by multiplying observed densities of seabirds with the total area covered by the slick, estimated at 793 km(2). A mean density of 3.46 murres/km(2) and 1.07 dovekies/km(2) on the sea surface was recorded during vessel-based surveys on 28 and 29 November 2004, with a mean density of 6.90 murres/km(2) and 13.43 dovekies/km(2) combining those on the sea and in flight. We calculated a mean of 9858 murres and dovekies were at risk of being oiled, with estimates ranging from 3593 to 16,122 depending on what portion of birds in flight were assumed to be at risk. A mortality model based on spill volume was derived independently of the risk model, and estimated that 4688 (CI 95%: 1905-12,480) birds were killed during this incident. A low mortality estimate based strictly on spill volume would be expected for this incident, which occurred in an area of relatively high seabird densities. Given that the risk and mortality estimates are statistically indistinguishable, we estimate that on the order of 10,000 birds were killed by the Terra Nova spill.     

Re-evaluating the use of beached bird oiling rates to assess long-term trends in chronic oil pollution

The oiling rate (oiled birds/total birds) has become the international standard to analyze beached bird survey data. However, this index may not reliably track long-term changes in marine oil pollution in regions where other activities that kill seabirds vulnerable to oil, such as hunting and gill-netting, are also changing. We compare the oiling rate from beached bird surveys conducted in southeastern Newfoundland between 1984 and 2006 to an alternative approach, namely trends derived from a model examining the linear density of oiled birds (birds/km). In winter, there was no change in the oiling rate since 1984, while in summer oiling rates significantly increased. In contrast, the number of oiled birds/km showed a significant decline in both winter and summer. The discrepancy in these trends was attributed to steep declines in the number of unoiled birds found in both seasons. In winter, the decline in unoiled birds/km was related to a reduction in the legal murre hunt and less onshore winds, while in summer a reduced cod fishery resulting in fewer murres drowning in nets and warming summers may have lead to the decline. The significant declines in oiled birds/km over the past three decades are hopefully an indication of less oil being present in the marine environment. Although oiled bird densities since 2000 have remained relatively low for the region (winter: 0.58 birds/km, summer: 0.27 birds/km), they still exceed densities reported elsewhere in the world.