The age of the Lower Carboniferous conglomerate at Lligwy Bay,Anglesey

The Lower Carboniferous conglomerate at Lligwy Bay, Anglesey, is shown to be underlain as well as overlain by limestones of D₁ age so that the conglomerate is of intra-D₁ age. It is considered to have been deposited very close to a coastline.     

Reconstruction of palaeosalinity using carbon isotopes and benthic associations: a comparison

Carbon and oxygen isotopes were determined on 40 recrystallized shells of Late Jurassic bivalves from the Lusitanian Basin of Portugal. In contrast with the oxygen isotopes, which exhibited considerable diagenetic distortion, the carbon isotopes are thought to preserve a record of the salinity of the Jurassic marginal marine seas in which these bivalves lived. The reconstructed palaeosalinities range from 35%o (euhaline) to 5% (oligohaline). Comparing these values with the palaeosalinity reconstructed from a palaeoecological analysis of 17 stratigraphic levels within the basin, the independently derived values agree in most cases. Strongly differing values are explained as being due to biotic factors and to diagenetic distortion of the isotopic signal; they are less likely to be due to smallscale time-averaging or insufficient microstratigraphic sampling. On the whole, the carbon isotope analyses are thought to produce reasonable palaeosalinity values, although data from infaunal, originally aragonitic bivalves appear to be less reliable than those from epifaunal bivalves with a predominantly or exclusively calcitic shell. As diagenetic alteration of the carbon isotope signal is, however, unpredictable and biotic effects on the isotopic composition are insufficiently known, palaeosalinity reconstructions based on stable isotope data should be supported by palaeoecological data.     

Geotechnical assessment of the bearing capacity of coal mine floors

Summary This investigation concerns 3 longwall faces having variable strata and mining conditions, but supported by 202 tonnes hydraulic 6-leg chocks. Bearing capacity tests along the faces were conducted to evaluate the factors influencing floor deformation and failure. The effect of size, shape and perimeter of the base plates, thickness of the floor layer, time and moisture on the ultimate bearing capacity of the floor was measured and discussed. Application of this work is the prediction of stability and support performance of face ends, as well as the design of support systems and ground control on production faces.     

Arsenic anomalies in shallow Venetian Plain (Northeast Italy) groundwater

A pilot area within the Venetian Plain was selected to assess the arsenic (As) contamination of groundwater. The area represents a typical residential, industrial and agricultural organization representative of most western countries, and is also devoid of lithologies with high or anomalous As content. Hydrogeological and chemical data have been collected, the latter spatialized by a geostatistical approach. The unconfined aquifer reservoir varies from a predominantly gravel composition in the north to a sandy and silt–clay composition further south, including peat layers. The hydrochemical features of the waters are rather homogeneous, featuring low mineral content and a Ca-bicarbonate signature. In contrast, the redox state is highly variable; oxidizing conditions are predominant in the northern and coarse parts of the aquifer, whereas reducing potentials prevail in the southern and silt–clay parts. Several well waters contain arsenic in excess of drinkable limits (=10 ppb), and most of these wells are located in the southern area. A large portion of the studied area has a high probability of containing non-potable water (up to 150 ppb As). Remarkably, As “hot spots” (As > 300 ppb, up to 431 ppb) were identified at the transition from gravel to silt–clay sediments. No industrial or agricultural source of As has been found.     

Sea-level rise impacts on longitudinal salinity for a low-gradient estuarine system

Climatic Change - Salinity response to sea-level rise is evaluated for a low-gradient, tidally active estuary, the lower St. Johns River, Florida. A high-resolution numerical model is forced by...     

Saturn's electrostatic discharges: Could lightning be the cause?

It is proposed that Saturn's electrostatic discharges (SED) might be generated in the planet's equatorial atmosphere, perhaps as lightning from a storm system. The 10^h10^m periodicity of the signal envelope duplicates that of Saturn's equatorial jet. The rings shield the atmosphere from solar EUV photons, and thereby substantially reduce the local ionospheric cutoff frequency to allow low-frequency SED to leak out. Many of the unusual properties of SED could be explained in terms of changes in the storm system, the relative spacecraft position in the beaming pattern of the source, local refraction of the signal by the highly disturbed ionosphere, and the influence of the ring particles on the highest frequency component of SED. A comparison of SED with planetary lightning on other planets shows that the two are similar in general character and some time behavior; the power output of SED may be higher than most planetary lightnings but that is unclear because of uncertainties in the measurements and variations in the signal's spectrum. Our simple discussion suggests that lightning could be a viable source for SED and that exotic ring mechanisms are not necessarily required.