A sampler-based technique for the study of near-bed sediment dynamics: application in the eastern English Channel

A simple technique for studying near-bed hydrodynamics and sediment dynamics is presented. The method combines the use of (1) a benthic tripod hosting a series of electromagnetic current meters, and (2) a newly developed near-bed multi-level water-sediment mixture sampler. The instrument package was deployed successfully at a shallow water station in the eastern English Channel. The currents at elevation 0.9 m above the bottom were asymmetrical, the flood current peak being slightly stronger than the ebb current peak. At elevation 0.3 m above the bottom, the ebb/flood current peak asymmetry vanished. The observed SSCs (suspended sediment concentrations) were tidally modulated, with a contrasting vertical distribution over the ebb and flood phases of the tidal current: the profile was uniform in the ebb phase whereas a stratification appeared in the flood phase. The depth dependence and time evolution of the SSCs are attributable to a combination of local resuspension and advection-dispersion of remotely suspended fine sediment by ebb currents. Suspended sediment fluxes were uniform during the ebb phase and increased with elevation above the bottom during the flood phase.     

Technopoles, high-tech industries and regional development: A critical review

Technologies have played an important role in the restructuring of the productive system in the last quarter of the 20th century. The article looks at the macroeconomic context and at the transformation of the industrial organization. It then defines the concept of technopole. The author traces the principal elements of the different attempts of theorization with a critical angle, shows the logic of contemporary industry localisation, as well as the role of technopoles in regional development. Regional and industrial policy are then seen as the basis of the process of industrialization and of the technological transfer.     

AMS radiocarbon dating and varve chronology of Lake Soppensee: 6000 to 12000 14C years BP

For the extension of the radiocarbon calibration curve beyond 10000 ¹⁴C y BP, laminated sediment from Lake Soppensee (central Switzerland) was dated. The radiocarbon time scale was obtained using accelerator mass spectrometry (AMS) dating of terrestrial macrofossils selected from the Soppensee sediment. Because of an unlaminated sediment section during the Younger Dryas (10000–11000 ¹⁴C y BP), the absolute time scale, based on counting annual layers (varves), had to be corrected for missing varves. The Soppensee radiocarbon-verve chronology covers the time period from 6000 to 12000 ¹⁴C y BP on the radiocarbon time scale and 7000 to 13000 calendar y BP on the absolute time scale. The good agreement with the tree ring curve in the interval from 7000 to 11450 cal y BP (cal y indicates calendar year) proves the annual character of the laminations. The ash layer of the Vasset/Killian Tephra (Massif Central, France) is dated at 8230±140 ¹⁴C y BP and 9407±44 cal y BP. The boundaries of the Younger Dryas biozone are placed at 10986±69 cal y BP (Younger Dryas/Preboreal) and 1212±86 cal y BP (Alleröd/Younger Dryas) on the absolute time scale. The absolute age of the Laacher See Tephra layer, dated with the radiocarbon method at 10 800 to 11200 ¹⁴C y BP, is estimated at 12350 ± 135 cal y BP. The oldest radiocarbon age of 14190±120 ¹⁴C y BP was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile. For the late Glacial, the offset between the radiocarbon (10000–12000 ^14C y BP) and the absolute time scale (11400–13000 cal y BP) in the Soppensee chronology is not greater than 1000 years, which differs from the trend of the U/Th-radiocarbon curve derived from corals.     

Free networks: minimum norm solution as obtained by the inner adjustment constraint method

The main goal of this paper is to show that the solution obtained by adjusting a free network via the inner adjustment constraint method is the minimum norm solution. The latter is a special case of the class of “minimum trace” solutions, where the trace of the variance-covariance matrix for the adjusted parameters is a minimum. The derivations are carried out in terms of pseudo-inverses, the various other forms of generalized inverses having been left out of consideration.     

Le Trias comme période salifère

1. In the Earth history not a system probably comprises so many evaporites than Triassic. They are not restricted to such or such protoocean but cover huge epicontinental cratonic plateforms with very finely bedded deposits as well as they fill rifts located in very diversified geodynamic areas. The first condition in order that such deposits can exist is a severe aridity.
2. Triassic corresponds to an extraordinary transgression in the sense of a new onlap of the sedimentary realm, a reconquest of ancient areas by new deposits, however their facies may be. In that general setting evaporites are themselves remarkably transgressive and from two points of view a) they sometimes onlap directly — that is to say without any basal detritic intercalation — different terms of peneplaned basement, b) these evaporites often succeed Permian emersion or continental detritic deposits of lower parts of Triassic. They extract their salts from Ocean. They often underlie pure marine Jurassic facies. For all these reasons evaporites appear as the first emissaries of oceanic realm and so as the first witnesses of a marine transgression.
3. Evaporites occur in Triassic, particularly in the Middle East, North Africa, on the two present margins of North Atlantic, on Western and Northern Europe, etc. The whole constitutes a huge saline ring round the western part of Triassic Tethysian sea. In that area, on the less tectonized plateforms a grandiose facies distribution pattern appears clearly: going farther from open sea in a centrifugal way, there are salts more and more soluble, until detritic deposits from continent. The pellicular sheets of water which covered the large plateforms resulting from late permian peneplanation should be favourable to modification of chemism, very gradual and at last very total, producing a geographical distribution of salt deposits. The most probable mover of these “floods” could be a very likely multiphase rise of eustatic level, the effects of which we cannot imagine because they occured on plateforms unknown in the geography of recent world. Effects of local morphology which induced a pecular distribution of salts can modify the general plateform distribution pattern.

     

Seismotectonics of the Papua New Guinea—Solomon Islands region

Earthquakes for the period 1964–1973 are relocated by the method of Joint Hypocenter Determination in order better to resolve the configuration and the structure of the New Guinea—New Britain—Solomon Islands region. Focal mechanism solutions are integrated with the seismicity and interpreted closely with it. A zone of subduction exists beneath New Britain and the Solomon Islands, a zone of left-lateral strike-slip movement extends from New Ireland to New Guinea. The zone of seismicity in northern New Guinea has developed as a result of a continent—island-arc collision in late Oligocene—Miocene times and does not exhibit a well-developed inclined seismic zone. It is proposed that plate tectonics theory does not apply rigorously, but slip-line field theory allows the presentation of a new geodynamic model for this region.