Reconstruction of Middle to Late Quaternary sea level using submerged speleothems from the northeastern Yucatán Peninsula

We examined 14 subaerially deposited speleothems retrieved from submerged caves in the northeastern Yucatán Peninsula (Mexico). These speleothems grew during the Middle to Late Quaternary and were dated by ²³⁰Th-U techniques to provide upper depth limits for past sea levels. We report the first relative sea-level limits for Marine Isotope Stages (MIS) 11 and 6, and present new evidence for sea-level oscillations during MIS 5 and early MIS 1. For the latter periods, the origin of growth interruptions is evaluated by combining petrographic methods with trace element analyses. The MIS 5c sea-level highstand probably occurred between 103.94 ± 0.58 ka and 96.82 ± 0.42 ka and must have exceeded -10.8 m (relative to present-day local sea level). The minimum average rate of sea-level fall over a 9.4 ka-long period during the MIS 5e/5d transition is calculated from stalagmite and published coral data at 1.74 ± 0.37 m/ka. For the early Holocene, previous discrepancies with respect to a potential multimetre oscillation of local sea level were found to be challenging to reconcile with the existing speleothem data from the area.     

Mulching as a means of exploiting dew for arid agriculture?

A traditional mulching technique used in Lanzarote, Canary Islands, allows dry farming as well as pronounced water savings in irrigation. It is known to reduce evaporational losses, but is also supposed to enhance the nocturnal condensation of water vapour from the atmosphere. The mulch layer consists of porous volcanic rock fragments abundantly available on the island. The mulched surface is believed to cool rapidly and to be more hygroscopic than a bare soil surface. This was investigated during a field experiment conducted over 68 nights during different seasons in 2001 and 2002, as well as some simple laboratory measurements. It was found that nocturnal condensation on the mulch surface (max 0.33 mm) was lower than on the bare soil surface (max 0.57 mm) or any one of three alternative mulch substrates. However, a slightly stronger nocturnal cooling of the mulched as compared to the bare surface was present. It is shown that these contrary findings can be explained by the higher hygroscopicity of the dry loam soil, resulting in condensation gains beyond the strict definition of dew. Differences in plant-availability of non-hygroscopic dew water and hygroscopic water uptakes are discussed, and conditions under which mulching would show positive condensation effects are defined. This includes a theoretical section demonstrating that non-hygroscopic mulch layers of a proper thickness can provide small amounts of dew to plant roots at the mulch–soil interface. This condensation could also happen during the day and would be favoured by a high amplitude of the diurnal atmospheric moisture cycle.     

Structural diversity and fate of intact polar lipids in marine sediments

Marine sediments harbor an enormous quantity of microorganisms, including a multitude of novel species. The habitable zone of the marine sediment column begins at the sediment-water interface and probably extends to depths of several thousands of meters. Studies of the microbial diversity in this ecosystem have mostly relied on molecular biological techniques. We used a complementary method - analysis of intact polar membrane lipids - to characterize the in-situ microbial community in sediments covering a wide range of environmental conditions from Peru Margin, Equatorial Pacific, Hydrate Ridge, and Juan de Fuca Ridge. Bacterial and eukaryotic phospholipids were only detected in surface sediments from the Peru Margin. In contrast, deeply buried sediments, independent of their geographic location, were dominated by archaeal diether and tetraether lipids with various polar head groups and core lipids. We compared ring distributions of archaeal tetraether lipids derived from polar glycosidic precursors with those that are present as core lipids. The distributions of these related compound pools were distinct, suggestive of different archaeal sources, i.e., the polar compounds derive from sedimentary communities and the core lipids are fossil remnants from planktonic communities with possible admixtures of decayed sedimentary archaea. This in-situ production of distinct archaeal lipid populations potentially affects applications of the TEX86 paleotemperature proxy as demonstrated by offsets in reconstructed temperatures between both pools. We evaluated how varying cell and lipid stabilities will influence the sedimentary pool by using a box-model. The results are consistent with (i) a requirement of continuous inputs of freshly synthesized lipids in subsurface sediments for explaining the observed distribution of intact polar lipids, and (ii) decreasing lipid inputs with increasing burial depth.     

The Sunyaev-Zel'dovich effect in the millimetric region

We analyse the spectral shape and possible spurious distortions of the Sunyaev-Zel'dovich effect, arising from the interaction of the cosmic background radiation with hot gases of rich clusters, in the millimetric region. We show that one can measure this effect with high accuracy with present-day infrared detectors, obtaining a larger amount of information than by using radio systems. In particular, one can accurately measure the temperature of the cosmic background radiation without the usual absolute calibration of the detector.     

Validation of Spatial Prediction Models for Landslide Hazard Mapping

This contribution discusses the problemof providing measures of significance ofprediction results when the predictionswere generated from spatial databases forlandslide hazard mapping. The spatialdatabases usually contain map informationon lithologic units, land-cover units,topographic elevation and derived attributes(slope, aspect, etc.) and the distributionin space and in time of clearly identifiedmass movements. In prediction modelling wetransform the multi-layered databaseinto an aggregation of functional values toobtain an index of propensity of the landto failure. Assuming then that the informationin the database is sufficiently representativeof the typical conditions in which the massmovements originated in space and in time,the problem then, is to confirm the validity ofthe results of some models over otherones, or of particular experiments that seem touse more significant data. A core pointof measuring the significance of a prediction isthat it allows interpreting the results.Without a validation no interpretation is possible,no support of the method or of theinput information can be provided. In particularwith validation, the added value canbe assessed of a prediction either in a fixedtime interval, or in an open-ended time orwithin the confined space of a study area.Validation must be of guidance in datacollection and field practice for landslidehazard mapping.     

Late Palaeozoic NE–SW ductile–brittle extension in the La Serre horst,eastern France

In the La Serre horst of the Alpine foreland, the pre-Triassic La Serre median fault zone separates a Late Devonian–Early Carboniferous granite from an ignimbrite of unknown age and from Permian deposits. Motion along this fault zone took place first in ductile conditions and then evolved in brittle conditions. Both ductile and brittle shear criteria indicate a top-NE normal-dextral displacement. Similar motions are reported along faults bounding Late Palaeozoic intramontane coal basins located in the Massif Central and correspond to a widespread NE–SW Late to Post-Orogenic extension that affected the Variscan basement during Late Carboniferous to Early Permian times. To cite this article: G. Coromina, O. Fabbri, C. R. Geoscience 336 (2004).     

A HIGH RESOLUTION MODEL FOR CHEMICAL SPECIES EXCHANGE IN TROPOSPHERE

Based on the regional acid deposition model(RADM),a high resolution model for species exchange in thetroposphere(EM3)is designed.EM3 differs considerably in the following 5 aspects from RADM.First,the vertical gridlevels in the planetary boundary layer(PBL)are increased.Second,layered vertical eddy diffusivity patterns in thetroposphere(TL)are considered.Third,layered horizontal eddy diffusivity patterns within TL is used.Fourth,new drydeposition velocity pattern including the effect of plant canopy layer(CL)vertical structure is adopted.Fifth,advectivescheme of second-order moment conservation with less numerical diffusion is used.OSCAR 4 case is comparativelysimulated with both EM3 and RADM.The results show that 3-D distribution laws of chemical species in whole TL areforecasted by EM3 better than by RADM.Under the same conditions,all ratios of the central concentrations simulatedwith both models in lower PBL are more than 1.8,the maximum can be more than 3.     

Das Glazialdiluvium Dänemarks,Hollands und Norddeutschlands vom geschiebekundlichen Standpunkt aus

Zusammenfassung Die Geschiebeführung des Diluviums in Dänemark, Holland und Norddeutschland bezüglich der kristallinen Geschiebe und des Flintgehaltes wird besprochen und daraus die Hauptbewegungsrichtung des Eises während der einzelnen Vereisungen abgeleitet. Da die Ablagerungen jeder Vereisung durch ihren Geschiebeinhalt identifiziert werden können, ergeben sich interessante Anwendungsmöglichkeiten für das Diluvium Dänemarks und des Hohen Flämings, für den Odergletscher usw.Zwei große Gletscher, aus der Verschmelzung der skandinavischen Einzelgletscher hervorgegangen, überziehen von Norwegen und von der Ostsee her Norddeutschland. Der Ostseegletscher drängt den norwegischen Gletscher zunächst allmählich, von der Pommerschen Phase ab endgültig von Dänemark und Deutschland ab.Für den Geschiebebestand Norddeutschlands und Hollands gelten folgende Verhältnisse: In den Ablagerungen der Elster-Vereisung dominieren die ostfennoskandischen, in denen der Saale-Vereisung die westlichen Geschiebegruppen. Das jüngere Diluvium enthält alle nordischen Geschiebe zu etwa gleichen Anteilen, demgegenüber die Geschiebeverhältnisse des Odergletschers und Dänemarks durchweg abweichende, aber erklärbare Züge aufweisen.     

Zur Berechnung der Abgaskonzentration am Boden im Lee isolierter Industrieschornsteine

Zusammenfassung Im Falle homogener Turbulenz läßt sich bei höhenkonstantem Wind die Konzentration im Lee einer punktförmigen Gasquelle über dem Boden in einfacher Weise berechnen. Die Formel ist bei geeigneter Parameterwahl auch auf die natürlichen Verhältnisse anwendbar. — In der vorliegenden Arbeit werden die effektiven Mittelwerte der in die Konzentrationsformel eingehenden Turbulenzparameter so ermittelt, daß eine weitgehende Übereinstimmung mit der Natur gewährleistet ist. Es zeigt sich, daß dieSuttonsche Diffusionsformel die maximale Gaskonzentration mit den geringsten Fehlern (ca.+10%) bei lebhaften Winden und kräftiger Einstrahlung wiedergeben kann, diese aber bei extrem stabiler Schichtung und turbulenter Strömung von geringer Geschwindigkeit um mehr als 100% überschätzt. — Die Theorie liefert eine gute Übereinstimmung mitPasquills Kurven für die Rauchwolkenhöhe, sofern man Fälle extremer Abweichungen vom adiabatischen Zustand ausschließt.

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Summary It is not difficult to calculate the gas concentration at ground level in the lee of a point source, if the turbulence is homogeneous and the windspeed is assumed to be constant with height. With a suitable choice of the parameters, however, the derived formula can be applied to real conditions, too. — In the present paper the necessary parameters are chosen as mean values in such a manner, that best agreement with nature is guaranted. It is found, thatSuttons diffusion formula overestimates the maximum gas concentration about 10 per cent in case of strong winds and strong insolation, but more than 100 per cent in case of light turbulent winds and extreme stability. Our theory is in good accordance withPasquills different curves for the vertical spread of smoke as a function of distance, if cases of extreme diabatic conditions are excluded.

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