Effects of three oil spill dispersants on marine bacterial populations: I. Preliminary Study. Quantitative Evolution of Aerobes

The effects of three hydrocarbon dispersant agents (Corexit 9527, Hydrogamosol LT and OSR LT 126) on the bacterial flora of the marine environment are analysed in 20-square-metre basins filled with lagoon seawater.Four months after the first treatment, oil slicks were no longer visible, whereas the appearance of the untreated reference slick had hardly changed. The treatment of 10-litre crude-oil slicks causes an appreciable and long lasting increase in the bacterial population.     

Deccan flood basalts at the Cretaceous/Tertiary boundary?

Joint consideration of new paleomagnetic, paleontological and geochronological data from the Deccan continental flood basalts in India and critical discussion of earlier results lead us to suggest that volcanic activity may have lasted less than 1 Ma, thus possibly ranking as one of the largest volcanic catastrophes in the last 200 Ma. Available data are best satisfied if volcanism spanned the Cretaceous/Tertiary boundary, followed shortly afterwards by rifting of the Arabian Sea. These results point out the need for further work which may help in choosing between “external” and “internal” models of the Cretaceous/Tertiary boundary events.     

An insight into grain interaction in bentonite/claystone mixtures

Acta Geotechnica - This paper investigates the swelling mechanism of Callovo-Oxfordian (COx) claystone grain in its mixtures with bentonite which are potential candidate for engineered barriers in...     

Osmium isotopes as petrogenetic and geological tracers

Using terrestrial osmium-enriched samples of known ages, we have shown that¹⁸⁷Os/¹⁸⁶Os varies with time in result of the¹⁸⁷Re β^? radioactivity. Such a variation in the earth's mantle can be fitted by a straight line corresponding to¹⁸⁷Re/¹⁸⁶Os = 3.15 for the mantle, comparable to C1 carbonaceous chondrites. Using this result and the Re and Os contents of various rocks, several theoretical considerations and predictions can be deduced for the chemical evolution of the earth, such as a method for distinguishing between different processes of development of the continental crust. The special result of¹⁸⁷Os/¹⁸⁶Os from Bushveld is discussed with respect to the possible existence of an “enriched” subcontinental mantle.     

The Japan Trench and its juncture with the Kuril Trench: cruise results of the Kaiko project, Leg 3

This paper presents the results of a detailed survey combining Seabeam mapping, gravity and geomagnetic measurements as well as single-channel seismic reflection observations in the Japan Trench and the juncture with the Kuril Trench during the French-Japanese Kaiko project (northern sector of the Leg 3) on the R/V “Jean Charcot”. The main data acquired during the cruise, such as the Seabeam maps, magnetic anomalies pattern, and preliminary interpretations are discussed. These new data cover an area of 18,000 km² and provide for the first time a detailed three-dimensional image of the Japan Trench. Combined with the previous results, the data indicate new structural interpretations. A comparative study of Seabeam morphology, single-channel and reprocessed multichannel records lead to the conclusion that along the northern Japan Trench there is little evidence of accretion but, instead, a tectonic erosion of the overriding plate. The tectonic pattern on the oceanic side of the trench is controlled by the creation of new normal faults parallel to the Japan Trench axis, which is a direct consequence of the downward flexure of the Pacific plate. In addition to these new faults, ancient normal faults trending parallel to the N65° oceanic magnetic anomalies and oblique to the Japan trench axis are reactivated, so that two directions of normal faulting are observed seaward of the Japan Trench. Only one direction of faulting is observed seaward of the Kuril Trench because of the parallelism between the trench axis and the magnetic anomalies. The convergent front of the Kuril Trench is offset left-laterally by 20 km relative to those of the Japan Trench. This transform fault and the lower slope of the southernmost Kuril Trench are represented by very steep scarps more than 2 km high. Slightly south of the juncture, the Erimo Seamount riding on the Pacific plate, is now entering the subduction zone. It has been preceded by at least another seamount as revealed by magnetic anomalies across the landward slope of the trench. Deeper future studies will be necessary to discriminate between the two following hypothesis about the origin of the curvature between both trenches: Is it due to the collision of an already subducted chain of seamounts? or does it correspond to one of the failure lines of the America/Eurasia plate boundary?     

Dynamics and behaviour of suspended sediment in macrotidal estuaries along the south coast of the English Channel

A review is given of suspended sediment dynamics in macrotidal regimes using examples of estuaries situated along the French coast of the English Channel. Characteristic features of estuarine turbidity maxima are described over a range of time-scales, which includes semidiurnal and neap-spring tidal cycles, and seasonal fluctuations of river discharge. The present behaviour of the fluvial sediment influx within these systems is described, taking into account the geological history of estuarine infilling.     

Dynamical-statistical methods of meso-scale precipitation forecasting over mountainous terrain

Summary Two diagnostic fine-mesh models for the determination of the vertical wind component over mountainous terrain have been developed. Both models rely on large-scale grid-point data. The first is based on the equivalent-barotropic scheme and uses 500 mbar heights as input data; the second model is built on the omega-equation and makes use of four input levels. Large-scale terms are interpolated from the large-scale grid to a fine-mesh grid with tenfold smaller mesh-width, while orographic terms are computed in the fine-mesh grid only. The slope of the model-topography and frictional effects are taken into consideration. Humidity and thermal convection are ignored. From computed vertical velocities and observed precipitations, an approximate prediction of precipitation is inferred by a regression technique. In the majority of cases, the baroclinic model gave slightly better results than the barotropic model.     

New terrestrial heat flow measurements on the Nazca Plate

Sixty-seven new heat flow measurements on the Nazca Plate are reported, and the thermal regimes of three specific areas on the plate are examined. The Nazca Ridge is an aseismic ridge which may have been generated as an “island trail” from the Easter Island “hot spot” and/or may be a fossil transform fault. The Nazca Ridge has lower heat flow than the surrounding sea floor implying that the ridge might have low “effective” thermal conductivity causing heat to preferentially flow or refract to surrounding ocean crust which has higher conductivity, or, the low heat flow values may be caused by hydrothermal circulation on the ridge. The Carnegie Plateau is an elevated region south of the Carnegie Ridge on the northeastern Nazca Plate with high heat flow and shallow topography consistent with an age of less than 20 m.y. B.P. The central Nazca Plate is an area of highly variable heat flow which is possibly related to thin sediment and to rough regional topography.     

Hailstone trajectories determined from crystallography,deuterium content and radar backscattering

Time-resolved hailstone samples have been collected in the region of maximum radar echo (=10 cm) from four severe hailstorms in Central Switzerland. Thin sections of 1220 hailstones have been prepared and their embryos were classified according to their bubble structure and crystallography. From this embryo trajectories were deduced. Thick sections of seven hailstones were then prepared in order to measure the deuterium content of the different growth layers. This allows an independent check of the embryo and hailstone trajectories as well as an approximate calculation of the updraft velocities. The deuterium content of the vapor feeding the cloud (R ₀) has been determined from structural features of the stones as well as from the heightH _–10: in this latter, new method the lowest deuterium values are attributed to those isotherms at which the top of the region of high radar reflectivity (Z _m–10 dBZ) is observed. It is shown that both embryo and hailstone trajectories determined by the two methods are generally in good agreement and that deuterium measurements in conjunction with structural analyses and radar data result in realistic updraft velocities which are in substantial agreement with results from a numerical cloud model. In the temperature interval –10<T _c<–25C upward motion of the hailstones generally corresponds to accretion of clear layers and downward motion to accretion of opaque layers at the same temperature. This is thought to be due to higher liquid water contents in the stronger updrafts resulting in growth near the wet limit.Dedicated to Prof. H. U. Dütsch on the occasion of his 60th anniversary.     

Relative Sea‐Level Changes During Roman Times in the Northwest Mediterranean: The 1st Century A.D. Fish Tank of Forum Julii,Fréjus,France

Fish tanks become fashionable throughout the Mediterranean area between the 1st century B.C. and the 1st century A.D. Because of this narrow chronological window, and their link to former sea level, they constitute precious archives to investigate relative sea level (RSL) since the Roman period, especially when combined with fossilized marine benthos found attached to the fish tank walls. Here, we present new results from an integrated analysis of a fish tank located in the Roman colony of Fréjus, Southeastern France. The well‐preserved biological remains on the fish tank wall allow us to estimate an RSL rise of 40 ± 10 cm at Fréjus since Roman times, consistent with a recently published range of −32 to −58 ± 5 cm for the Northwestern Mediterranean for the same time. By contrast, the findings contradict the ∼150 cm of RSL change since Roman times reported for the Northwestern Mediterranean by some authors. © 2013 Wiley Periodicals, Inc.