Benthic Metabolism and Standing Stock in the Central and Northern Deep Red Sea

Abstract. Benthic metabolism and standing stocks were investigated in the deep Red Sea between 21^o and 27^oN, Activity was assessed by the determination of respiration rates with a shipboard method and by calculating oxygen consumption from the activity in the electron transport system. We attempted to compare results from different latitudes within the warm Red Sea and with data from cold Atlantic environments. Our investigations were part of an environmental risk assessment to evaluate future mining of metalliferous sediments from the Atlantis II Deep.     

Researching the South African tourism and development nexus

Under apartheid, tourism was essentially anti-developmental in focus and tourism research largely centred on the recreation of white South Africans. Since the 1994 democratic transition tourism has become recognised as an increasingly important sector for South Africa's economy and for achieving the government's goals for reconstruction and development. In this paper a review and critical analysis is presented of the changing directions and foci of tourism scholarship in South Africa. It is shown that South African scholars are beginning to respond to the challenges posed by tourism as a developmental focus. This revised version was published online in August 2006 with corrections to the Cover Date.     

Large-scale dune erosion tests to study the influence of wave periods

Large-scale physical model tests were performed to quantify the effects of the wave period on dune erosion. Attention was focussed on 2D cross-shore effects in a situation with sandy dunes and extreme water levels and wave conditions. Besides profile measurements, detailed measurements in time and space of water pressure, flow velocities and sediment concentrations were performed in the near near-shore area. It was concluded that a longer wave period leads to a larger dune erosion volume and to a larger landward retreat of the dune face. Tests with double-peaked wave spectra showed that the influence of the spectral shape on dune erosion was best represented by the T_m − 1,0 spectral mean wave period, better than the peak wave period, T_p. The effect of the wave period on dune erosion was implemented in a dune erosion prediction method that estimates erosion volumes during normative storm conditions for the Dutch coast. More details of the measurements and additional analyses of physical processes are described in an accompanying paper by Van Thiel de Vries et al. [Van Thiel de Vries, J.S.M., van Gent, M.R.A., Reniers, A.J.H.M. and Walstra, D.J.R., submitted for publication. Analysis of dune erosion processes in large scale flume experiments, In this volume of Coastal Engineering.].     

Resistance of a soil layer to horizontal vibration of a pile

The resistance of a soil to horizontal harmonic vibration of a vertical, end bearing pile with circular cross-section is theoretically investigated. The soil is considered to be a continuum with material damping of the hysteretic type. The motions of the soil and pile are expressed as series, and a resistance coefficient on each term in the series of the pile motion is found. The resistance is found to depend on the excitation frequency, the pile slenderness and on the material properties of the soil. Finally a study of the influence of the parameters is carried out.     

Cold seep deposits of Beauvoisin (Oxfordian; southeastern France) and Marmorito (Miocene; northern Italy): microbially induced authigenic carbonates

The relation of two well-known ancient carbonate deposits to hydrocarbon seepage was confirmed by this study. Archaea are found to be associated with the formation of Oxfordian seep carbonates from Beauvoisin and with a Miocene limestone from Marmorito ("tube-worm limestone"). Carbonates formed due to a mediation by archaea exhibit extremely positive or extremely negative δ¹³C_carbonate values, respectively. Highly positive values (+15‰) reflect the use of ¹³C-enriched CO₂ produced by methanogenesis. Low δ¹³C values of the Marmorito carbonates (–30‰) indicate the oxidation of seepage-derived hydrocarbons. Likewise, the δ¹³C content of specific tail-to-tail linked isoprenoids, biomarkers for archaea, was found to be strikingly depleted in these samples (as low as –115‰). The isotopic signatures corroborate that archaea were involved in the cycling of seepage-derived organic carbon at the ancient localities. Another Miocene limestone ("Marmorito limestone") shows a strong imprint of methanotrophic bacteria as indicated by δ¹³C values of carbonate as low as –40‰ and biomarker evidence. Epifluorescence microscopy and field-emission scanning electron microscopy revealed that bacterial biofilms were involved in carbonate aggregation. In addition to lucinid bivalves previously reported from both localities, we infer that sponges from Beauvoisin and tube worms from Marmorito depended on chemosynthesis as well. Low δ¹³C values of nodules related to sponge taphonomy (–27‰) indicate that sponges might have been linked to an enhanced hydrocarbon oxidation. Tube worm fossils from Marmorito closely resemble chemosynthetic pogonophoran tube worms from Recent cold seeps and are embedded in isotopically light carbonate (δ¹³C –30‰). Received: 13 October 1998 / Accepted: 5 February 1999     

Cosmic-ray-induced fission of heavy nuclides: Possible influence on apparent U-fission track ages of extraterrestrial samples

The rates of cosmic-ray-induced fission of U, Th, Bi, Pb, and Au in mineral samples as a function of burial depth in the lunar surface layer are calculated using the available experimental particle flux and cross section data. Theoretical correction factors are given for apparent fission track ages of extraterrestrial samples of different burial depths which were exposed to cosmic rays for various time fractions of their solidification age. Samples having typical lunar heavy element contents can yield apparent fission track ages which are too high by a factor of up to 13 due to cosmic-ray-induced fission. The interference may be neglected, if the ratio of exposure age to solidification age remains 5 × 10⁻³. The calculations show, that the induced fission of Bi, Pb, and Au which are known to have high meteoritic abundances may dominate spontaneous ²³⁸U-fission in long-time exposed meteorites of low U and Th contents.     

Pore-water pressure development in a frozen saline clay under isotropic loading and undrained shearing

Acta Geotechnica - A systematical testing program on frozen Onsøy clay under isotropic loading and undrained shearing at different temperatures...     

Tectonic evolution of the southern Gawler Craton,South Australia,from electromagnetic sounding

Long-period natural-source electromagnetic data have been recorded using portable three-component magnetometers at 39 sites in 1998 and 2002 across the southern Eyre Peninsula, South Australia that forms part of the Gawler Craton. Site spacing was of order 5 km, but reduced to 1 km or less near known geological boundaries, with a total survey length of approximately 50 km. A profile trending east – west was inverted for a 2D electrical resistivity model to a depth of 20 km across the southern Eyre Peninsula. The main features from the models are: (i) on the eastern side of the Gawler Craton, the Donington Suite granitoids to the east of the Kalinjala Shear Zone are resistive (>1000 Ωm); (ii) the boundary between the Donington Suite granitoids and the Archaean Sleaford Complex, which has much lower resistivity of 10 – 100 Ωm, is almost vertical in the top 10 km and dips slightly westwards; and (iii) two very low resistivity (<1 Ωm) arcuate zones in the top 3 km of Hutchison Group sediments correlate with banded iron-formations, and are probably related to biogenic-origin graphite deposits concentrated in fold hinges. Such features suggest an extensional regime during the time period 2.00 – 1.85 Ga. We suggest that the resistivity boundary between the Donington Suite and the Archaean Sleaford Complex represents a growth fault, typical for rift systems that evolve into a half-graben structure. In the graben basin, low-resistivity shallow-marine Hutchison Group sediments were deposited. Folding of the sediments during the Kimban Orogeny between 1.74 and 1.70 Ga has led to migration of graphite to the fold hinges resulting in linear zones of very low resistivity that correlate with banded iron-formation magnetic anomalies.     

Relating remotely sensed forest damage data to wind data: storms Lothar (1999) and Vivian (1990) in Switzerland

This study compares the surface wind speed and forest damage data of two exceptionally severe winter storms, Vivian 1990 and Lothar 1999. The study area comprises the region that suffered damage in Switzerland. The wind speed data were derived from simulations of MeteoSwiss (Federal Office of Meteorology and Climatology), measurements during the storm periods and expert analyses of the data. The remotely sensed forest damage data were provided by the Federal Office for the Environment and the forest cover data by Swiss Federal Statistical Office. We compared data on the peak gust and maximum average wind speed, with data on the spatially related forest area and forest damage area, and found some clear differences in the correlations between the different wind data and forest damage. Our results point generally to the damage-causing role of near-surface gusts at maximum wind speeds during the storm. These tended to be spatially distributed on a fine scale. In only a few cases were the results statistically significant. However, these results could probably be improved with better wind data. For example, gust measurements spatially closer to forests or simulations of gusts at maximum wind speed could be produced with a spatially higher resolution.