Prismatine and Ferrohogbomite-2N2S in Granulite-Facies Fe-Oxide Lenses in the Eastern Ghats Belt at Venugopalapuram, Vizianagaram District, Andhra Pradesh, India: Do Such Lenses Have a Tourmaline-Enriched Lateritic Precursor?

Fluorine-rich prismatine, (square,Fe,Mg)(Mg,Al,Fe)(5)Al-4(Si,B,Al)(5)O-21(OH,F), with F/(OH+F) = 0.36-0.40 and hercynite are major constituents of a Fe-Al-B-rich lens in ultrahigh-temperature granulite-facies quartz-sillimanite-hypersthene-cordierite gneisses of the Eastern Ghats belt, Andhra Pradesh, India. Hemo-ilmenite. sapphirine, magnetite, biotite and sillimanite are subordinate. Lithium, Be and B are concentrated in prismatine (140 ppm Li, 170 ppm Be, and 2.8-3.0 wt.% B2O3). Another Fe-rich lens is dominantly magnetite, which encloses fine-grained zincian ferrohogbomite-2N2S, (Fe2+ Mg,Zn,Al)(6) (Al,Fe3+,Ti)(16)O-30(OH)(2), containing minor Ga2O3 (0.30-0.92 wt.%). Fe-Al-B-rich lenses with prismatine (or kornerupine) constitute a distinctive type of B-enrichment in granulite-facies rocks and have been reported from four other localities worldwide. A scenario involving a tourmaline-enriched lateritic precursor affected by dehydration melting is our preferred explanation for the origin of the Fe-Al-B-rich lenses at the five localities. Whole-rock analyses and field relationships at another of these localities, Bok se Puts, Namaqualand, South Africa, are consistent with this scenario. Under granulite-facies conditions, tourmaline would have broken down to give korner-upine-prismatine ( other borosilicates) plus a sodic melt containing H2O and B. Removal of this melt depleted the rock in Na and B, but the formation of ferromagnesian borosilicate phases in the restite prevented total loss of B.

On the Co-Occurrence of Warm Conveyor Belt Outflows and PV Streamers*

The co-occurrence of warm conveyor belts (WCBs), strongly ascending moist airstreams in extratropical cyclones, and stratospheric potential vorticity (PV) streamers, indicators for breaking Rossby waves on the tropopause, is investigated for a 21-yr period in the Northern Hemisphere using Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) data. WCB outflows and PV streamers are respectively identified as two- and three-dimensional objects and tracked during their life cycle. PV streamers are more frequent than WCB outflows and nearly 15% of all PV streamers co-occur with WCBs during their life cycle, whereas about 60% of all WCB outflows co-occur with PV streamers. Co-occurrences are most frequent over the North Atlantic and North Pacific in spring and winter. WCB outflows are often located upstream of the PV streamers and form earlier, indicating the importance of diabatic processes for downstream Rossby wave breaking. Less frequently, PV streamers occur first, leading to the formation of new WCBs.

Association of optical tracklets from a geosynchronous belt survey via the direct Bayesian admissible region approach

The direct Bayesian admissible region approach is an a priori state free measurement association and initial orbit determination technique for optical tracks. In this paper, we test a hybrid approach that appends a least squares estimator to the direct Bayesian method on measurements taken at the Zimmerwald Observatory of the Astronomical Institute at the University of Bern. Over half of the association pairs agreed with conventional geometric track correlation and least squares techniques. The remaining pairs cast light on the fundamental limits of conducting tracklet association based solely on dynamical and geometrical information.

The tectonometamorphic evolution of the Sesia–Dent Blanche nappes (internal Western Alps): review and synthesis

This study reviews and synthesizes the present knowledge on the Sesia–Dent Blanche nappes, the highest tectonic elements in the Western Alps (Switzerland and Italy), which comprise pieces of pre-Alpine basement and Mesozoic cover. All of the available data are integrated in a crustal-scale kinematic model with the aim to reconstruct the Alpine tectono-metamorphic evolution of the Sesia–Dent Blanche nappes. Although major uncertainties remain in the pre-Alpine geometry, the basement and cover sequences of the Sesia–Dent Blanche nappes are seen as part of a thinned continental crust derived from the Adriatic margin. The earliest stages of the Alpine evolution are interpreted as recording late Cretaceous subduction of the Adria-derived Sesia–Dent Blanche nappes below the South-Alpine domain. During this subduction, several sheets of crustal material were stacked and separated by shear zones that rework remnants of their Mesozoic cover. The recently described Roisan-Cignana Shear Zone of the Dent Blanche Tectonic System represents such a shear zone, indicating that the Sesia–Dent Blanche nappes represent a stack of several individual nappes. During the subsequent subduction of the Piemonte–Liguria Ocean large-scale folding of the nappe stack (including the Roisan-Cignana Shear Zone) took place under greenschist facies conditions, which indicates partial exhumation of the Dent Blanche Tectonic System. The entrance of the Briançonnais micro-continent within the subduction zone led to a drastic change in the deformation pattern of the Alpine belt, with rapid exhumation of the eclogite-facies ophiolite bearing units and thrust propagation towards the foreland. Slab breakoff probably was responsible for allowing partial melting in the mantle and Oligocene intrusions into the most internal parts of the Sesia–Dent Blanche nappes. Finally, indentation of the Adriatic plate into the orogenic wedge resulted in the formation of the Vanzone back-fold, which marks the end of the pervasive ductile deformation within the Sesia–Dent Blanche nappes during the earliest Miocene.

Early-Holocene afforestation processes in the lower subalpine belt of the Central Swiss Alps as inferred from macrofossil and pollen records

To reconstruct the vegetation history of the Upper Engadine, continuous sediment cores covering the past 11 800 years from Lej da Champfer and Lej da San Murezzan (Upper Engadine Valley, c. 1800 m a.s.l., southeastern Switzerland) have been analysed for pollen and plant macrofossils. The chronologies of the cores are based on 16 and 22 radiocarbon dates, respectively. The palaeobotanical records of both lakes are in agreement for the Holocene, but remarkable differences exist between the sites during the period 11 100 to 10 500 cal. BP, when Lej da Champfer was affected by re-sedimentation processes. Macrofossil data suggest that Holocene afforestation began at around 11400 cal. BP. A climatic deterioration, the Preboreal Oscillation, stopped and subsequently delayed the establishment of trees until c. 11000 cal. BP, when first Betula, then Pinus sylvestrislmugo, then Larix 300 years later, and finally Pinus cembra expanded within the lake catchment. Treeline was at c. 1500 m during the Younger Dryas (12 542- 11 550 cal. BP) in the Central Alps. Our results, along with other macrofossil studies from the Alps, suggest a nearly simultaneous afforestation (e.g., by Pinus sylvestris in the lower subalpine belt) between 1500 and 2340 m a.s.l. at around 11 400 to 11 300 cal. BP. We suggest that forest-limit species (e.g., Pinus cembra, Larix decidua) could expand faster at today's treeline (c. 2350 m a.s.l.), than 550 m lower. Earlier expansions at higher altitudes probably resulted from reduced competition with low-altitude trees (e.g. Pinus sylvestris) and herbaceous species. Comparison with other proxies such as oxygen isotopes, residual A14C, glacier fluctuations, and alpine climatic cooling phases suggests climatic sensitivity of vegetation during the early Holocene.

Grain size distribution and percentiles of the sand component from sediments obtained in the southern Great Belt, Baltic Sea

Im Sedimentationsraum der südwestlichen Ostsee verdient der nordöstliche Teil der Kieler Bucht besonderes Interesse. Dort öffnet sich die wichtigste Verbindung zwischen Ostsee und Nordsee. Von den Austauschvorgängen, durch welche diese Meeresräume aufeinander Einfluß nehmen, ist gerade jenes Gebiet entscheidend betroffen. Die Beobachtung der Dynamik des Austausches, die Beobachtung der Transportlast, welche von den Wassermassen bewegt wird, und schließlich auch die Beobachtung der Beziehungen, welche sich zwischen dem Zusammentreffen von Wassermassen unterschiedlicher physikalischer Eigenschaften und der Sedimentbildung ergeben, läßt deshalb vor allem dort wesentliche Hinweise zum Verständnis der Sedimentationsvorgänge in der südlichen Ostsee erhoffen. In der vorliegenden Arbeit wurden an 49 Durchschnittsproben die Korngrößenverteilungen und Schwermineralgehalte von Sedimenten aus dem Südausgang des Großen Beltes untersucht. 1. Es wurden sechs in sich morphologisch etwa gleichwertige Gebiete ausgegliedert, die jeweils durch Sedimente mit ähnlichen Korngrößenverteilungen ausgezeichnet sind. Nach Lage, Typ und genetischer Ausdeutbarkeit fügen sich diese Gebiete dem von O. PRATJE (1939, 1948) gegebenen Modell der Sedimentationszonen gut ein. 2. Innerhalb dieser Gebiete ergibt sich für Sande in mehr als 20 m Wassertiefe südwärts gerichteter Transport. Oberhalb dieser Tiefe läßt sich stellenweise nordwärts gerichteter Transport nachweisen. 3. Der Schwermineralgehalt der Sedimente bleibt immer unter zwei Prozent. Die höchsten Anteile (1,7 bzw. 1,9%) werden in den Sedimenten der Tiefen Rinne und der ufernahen Bereiche des Großen Beltes angetroffen. 4. Die Korngrößenverteilungen der Sedimente werden nach der Lage der Modi in bis zu drei (Kies-, Sand-, Silt-) Komponenten zerlegt. Die Beteiligung der Silt-Komponente wird entscheidend von der Salzgehaltssprungschicht beeinflußt. 5. Es bestehen offensichtlich Zusammenhänge zwischen der Schlicksedimentation und der Salzgehaltsschichtung auch in der weiteren südlichen Ostsee.