Detecting ancient wild rice (Zizania spp. L.) using phytoliths: a taphonomic study of modern wild rice in Minnesota (USA) lake sediments

Wild rice (Zizania spp. L.) is a North American native grain with spiritual and dietary significance to many native people. Wild rice is also an important aquatic plant that provides critical habitat to wetland and aquatic wildlife. Past distribution of wild rice in North America is poorly understood, largely because of the limited taxonomic resolution of Poaceae pollen. A novel technique for detecting diagnostic Zizania silica phytoliths allows unambiguous identification of this taxon in lake sediments. We need to better understand modern depositional patterns of phytoliths in lake sediments, however, before attempting detailed paleoreconstructions. We analyzed distributions of diagnostic Zizania and other Poaceae phytoliths in modern sediments from three lakes with variable percent cover of wild rice and a non-wild rice control lake in central Minnesota. Absolute counts of phytoliths per gram sediment were achieved using an exotic diatom marker. Non-Zizania short-cell phytoliths, i.e. phytoliths from wetland grasses Phragmites australis and Muhlenbergia glomerata, dominate the assemblages in all lakes. Most Poaceae short-cell phytoliths appear to be derived locally, with little evidence for regional inheritance from eolian or alluvial processes. Because of anatomical differences in decay of plant debris and other taphonomic issues, Zizania inflorescence rondel phytoliths were most abundant, with morphotypes from other parts rarely encountered. Even in sediments under the densest wild rice stands, Zizania phytoliths contributed a maximum of 9 % to total Poaceae phytolith abundance. Lake morphology also affects the depositional pattern of phytoliths in modern sediments, so coring locations should be considered carefully. At least 500 phytoliths should be counted to detect a sufficient number of wild rice phytolith morphotypes. Diagnostic Zizania phytoliths are a reliable tool for wild rice detection in paleolake sediments.     

Observation impact analysis methods for storm surge forecasting systems

This paper presents a simple method for estimating the impact of assimilating individual or group of observations on forecast accuracy improvement. This method is derived from the nsemble-based observation impact analysis method of Liu and Kalnay (Q J R Meteorol Soc 134:1327–1335, 2008). The method described here is different in two ways from their method. Firstly, it uses a quadratic function of model-minus-observation residuals as a measure of forecast accuracy, instead of model-minus-analysis. Secondly, it simply makes use of time series of observations and the corresponding model output generated without data assimilation. These time series are usually available in an operational database. Hence, it is simple to implement. It can be used before any data assimilation is implemented. Therefore, it is useful as a design tool of a data assimilation system, namely for selecting which observations to assimilate. The method can also be used as a diagnostic tool, for example, to assess if all observation contributes positively to the accuracy improvement. The method is applicable for systems with stationary error process and fixed observing network. Using twin experiments with a simple one-dimensional advection model, the method is shown to work perfectly in an idealized situation. The method is used to evaluate the observation impact in the operational storm surge forecasting system based on the Dutch Continental Shelf Model version 5 (DCSMv5).     

Spectrum of the Sunyaev-Zel'dovich effect for high electron temperatures

We analyse in detail the spectral shape of the Sunyaev-Zel'dovich effect in the cosmic background radiation, taking into account the relativistic corrections for a hot electron gas. We calculate the displacement of the zero-signal frequency, which is especially informative in a new method for measuring the millimetric temperature of the background radiation; we also present a simple analytical expression, to be used to fit the experimental data in spectral measurements of the effect in very hot cluster gases.     

Neue Ergebnisse der Geschiebeforschung im norddeutschen Diluvium (kristalline Geschiebe)

Zusammenfassung Die neuen Geschiebeuntersuchungen bestätigen die Erfahrung, daß jede Vereisung ihren besonderen Geschiebeinhalt besitzt. Für die Elster-Vereisung spielen ostfennoskandische, für die Saale-Vereisung westfennoskandische Geschiebe die Hauptrolle. Im jüngeren Diluvium sind alle Geschiebegruppen etwa gleich stark an der Zusammensetzung des Geschiebeinhaltes beteiligt. Das Ostseebecken tritt besonders in der Warthe-Vereisung als Hauptlieferant von Geschieben auf. Von der Pommerschen Phase ab ergeben sich stark differenzierte Geschiebeverhältnisse.Von einer Gleichartigkeit des Geschiebebestandes von Holland bis Ostpreußen, wieKummerow meint, kann man demnach nicht sprechen. Scharf abgetrennte Sonderungen des Geschiebeinhaltes nach Gesteinsprovinzen oder sogar noch kleineren Heimatgebieten haben sich für kristalline Geschiebe in Norddeutschland nicht ergeben. Sie waren nach den mehrfach richtungswechselnden Gletscherbahnen und bei der Rolle des norddeutschen Diluviums als Randbildung einer großen fennoskandischen Eismasse auch nicht zu erwarten. Die Unterschiede in der Beteiligung von 4 großen Geschiebegruppen genügen aber, um das Alter von Diluvialablagerungen an ihren Geschieben zu erkennen. Die Durchführung derartiger stratigraphischer Aufgaben ist durch die Heranziehung von 80 neuen kristallinen Leitgeschieben verbessert. Auf der verbreiterten Grundlage ist natürlich auch eine verfeinerte Analyse der Gletscherbahnen und des Vereisungsmechanismus überhaupt im großen und kleinen Maßstabe möglich. Man darf sich allerdings dabei nicht verhehlen, daß nun zwar die Grundzüge, aber noch längst nicht die Einzelgeschehnisse des Eiszeitalters geklärt sind. An dieser Aufgabe mitzuwirken, ist auch die Geschiebeforschung berufen und in vielen, oben dargetanen Fällen durch keine andere Forschungsart zu ersetzen. Daß Untersuchungen kristalliner Geschiebe je nach Neigung nebenbei oder hauptsächlich petrographisch, paläogeographisch oder rein sammlungsmäßig-heimatkundlich dankbare Objekte abgeben, dafür sind aus den Arbeiten der letzten 5 Jahre ebenfalls einige Beispiele angeführt.     

Growth fault on insular slope/rise of western Iceland; comparison with SE Greenland canyons and slumps

A recently active normal fault and extensional crevasse on the western insular slope/rise boundary of Iceland adjoins a rotational slump that moved as the lower block of an active growth fault. A slump off SE Greenland is contrasted to the western Iceland slope/rise feature in translational movement and slump morphology. Bergschrund-like extensional cracks and valleys at the heads of slumps serve as troughs channeling gravity flows into established canyons on the midrise. Distinctive characteristics of buried canyons and levees may be confused with slump or slide surfaces and related subbottom features that have similar seismic reflection qualities. Examples are defined forGrowth Fault/Rotational Slumps, andTranslational Displacement Slumps.     

Relationships between magmatism and extension along the Autun–La Serre fault system in the Variscan Belt of the eastern French Massif Central

The ENE–WSW Autun Shear Zone in the northeastern part of the French Massif Central has been interpreted previously as a dextral wrench fault. New field observations and microstructural analyses document a NE–SW stretching lineation that indicates normal dextral motions along this shear zone. Further east, similar structures are observed along the La Serre Shear Zone. In both areas, a strain gradient from leucogranites with a weak preferred orientation to highly sheared mylonites supports a continuous Autun–La Serre fault system. Microstructural observations, and shape and lattice-preferred orientation document high-temperature deformation and magmatic fabrics in the Autun and La Serre granites, whereas low- to intermediate-temperature fabrics characterize the mylonitic granite. Electron microprobe monazite geochronology of the Autun and La Serre granites yields a ca. 320 Ma age for pluton emplacement, while mica ⁴⁰Ar-³⁹Ar datings of the Autun granite yield plateau ages from 305 to 300 Ma. The ca. 300 Ma ⁴⁰Ar-³⁹Ar ages, obtained on micas from Autun and La Serre mylonites, indicate the time of the mylonitization. The ca. 15-Ma time gap between pluton emplacement and deformation along the Autun–La Serre fault system argue against a synkinematic pluton emplacement during late orogenic to postorogenic extension of the Variscan Belt. A ductile to brittle continuum of deformation is observed along the shear zone, with Lower Permian brittle faults controlling the development of sedimentary basins. These results suggest a two-stage Late Carboniferous extension in the northeastern French Massif Central, with regional crustal melting and emplacement of the Autun and La Serre leucogranites around 320 Ma, followed, at 305–295 Ma, by ductile shearing, normal brittle faulting, and subsequent exhumation along the Autun–La Serre transtensional fault system.     

A composed index of critical accessibility (CICA) to healthcare services in a traditional African City

While empirical works that analyse rural–urban differentials in accessibility to health services are common in the developing countries, systematic studies focusing on intra-urban variations in accessibility to overall healthcare resources remain scant. Yet, many urban dwellers especially in the Sub-Saharan Africa have to travel long distances within the urban space to access basic health services. This study employs composed index of critical accessibility (CICA) to analyse differentials in access to health resources in Ibadan, a traditional African City. Data on healthcare centre location, ownership, doctors’ population were collected through field survey while spatial data on the administrative units and populated places were obtained from archival sources. Also, data on road networks was collected. Results show that the distribution of health facilities across local administrative units varies. In terms health facilities, Ibadan South West has 26 (36 %) of the total number while Ibadan South east has only 7 (9.8 %). The Doctor-Population Ratio also exhibits similar variations as Ibadan North has 20.5 as against 2.2, 1.9 and 0.3 for Ibadan SW, Ibadan NW and Ibadan NE respectively. The CICA analysis shows that 228,938 inhabitants are in high risk of negative accessibility while 49,234 are faced with condition of low risk of negative accessibility, which implies that a significant proportion of the population still finds it difficult to access basic health services as and when needed. The variations in the distribution of this deprived population are also noteworthy as the largest proportion of this group was localized in Ibadan NW. This has grave implication for the health and wellbeing of the population and raises once again the question of spatial equity in the delivery of urban public service. Curiously, these differences in the level of accessibility cut across administrative boundaries which brings to the fore the role of jurisdictional partitioning in ensuring equity in the delivery of urban public services. This opens a vista of research opportunity into the role jurisdictional partitioning in service provision in the urban centres.     

Pseudotachylytes in the Balmuccia peridotite (Ivrea Zone) as markers of the exhumation of the southern Alpine continental crust

Two types of pseudotachylytes are observed in the Balmuccia peridotite of the Ivrea zone (Southern Alps, Italy). A-type pseudotachylytes correspond to previously studied occurrences and were formed under temperatures comprising between 550 and 900 °C and pressures comprising between 0.6 and 1.2 GPa. These conditions were met in the Ivrea crust between 350 and 270 Ma, suggesting that A-type pseudotachylytes were formed during Variscan tectonics or Permian transtensional tectonics. B-type pseudotachylytes post-date A-type pseudotachylytes. Textural characteristics of B-type veins suggest a formation in the upper continental crust, at depths of about 5–10 km or less. Petrological constraints indicate that the exhumation of the Ivrea crust at such shallow depths was achieved later than c.  70 Ma, thus providing a maximum age of 70 Ma for B-type veins. Pseudotachylytes appear as markers of the poly-orogenic evolution of the Alpine belt.