Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): Sediment accumulation rates, trawling and winnowing effects

Four cores recovered within the framework of the INTERPOL Project have been analysed for their grain size and geochemistry; sediment accumulation rates (SARs) were also determined from ²¹⁰Pb and ¹³⁷Cs profiles. Two cores are representative of the Axios and Aliakmon Rivers depositional environment, whilst the third core represents the Pinios River province; the fourth core represents an environment of outer shelf relict sands. Apparent SARs ranged between 0.667 g cm⁻² yr⁻¹ (Axios and Aliakmon Rivers) and 0.414 g cm⁻² yr⁻¹ (Pinios River). Trawling activities and biomixing are critical processes that may be responsible for the mixing of the surface sediments, as observed from the excess ²¹⁰Pb profiles. The thickness of the surface mixed layer was 4.5 cm in the vicinity of Axios and Aliakmon Rivers and in the area of Pinios River, 3.75 cm on the outer shelf and 1 cm in the area where no trawling was observed. Sediment accumulation appeared to be regulated by variations in the riverine discharge, shelf transport pathways and winnowing processes. Major element variations, such as Si, Al, Ti, V and Ni, were dominated by terrigenous supply as aluminosilicate minerals and quartz, whereas most Ca and Sr were biogenic. Si/Al and Ca/Al ratios have been used to express changes in sediment accumulation and winnowing. Redox processes were depicted by Mn, which showed an increase in the depth of its redoxcline, from 1 cm in inshore stations to 2 cm on the outer shelf. Si/Al ratios follow the Ca/Al ratios and can be used to assess percentage winnowing in the sediment. Increases in these ratios indicate a decrease in sediment input rates and are seen in the upper parts of most of the cores. Anthropogenic or ‘excess’ metal contents have been calculated from Zn/V and Pb/V ratios. Their distributions in the cores showed that by far the highest contamination is associated with the Axios River output, whilst sediments influenced by the Pinios River were relatively uncontaminated.     

The microfossils from the proterozoic Urquhart Shale,Mount Isa,Queensland, and their significance in relation to the depositional environment,diagenesis, and mineralisation

The Urquhart Shale from Mount Isa, Queensland, hosts major lead-zinc and copper orebodies. Re-examination of organic matter from the lead-zinc ore bodies has shown that abundant microfossils characteristic of lacustrine environments are present, and substantiates earlier results of Love and Zimmerman (1961). The framboid residues described by these authors are not microfossils but nevertheless the occurrence of framboidal pyrite has important implications for the timing of lead-zinc mineralisation. A diagenetic model is proposed for the lead-zinc ore bodies, and a later transgressive event accounts for the mode of occurrence of the copper ore bodies.     

Trace element chemistry of Apollo 14 lunar soil from Fra Mauro

Analytical data are presented for Apollo 14 fines ( < 1 mm) sample 14163,136 for 31 trace elements. The heavy REE are enriched monotonically by factors of 105 ± 10 over chondrites. Eu shows a large depletion (30 × chondrites) and the light REE show a smooth progressive enrichment with a slight fall at La. Ba, Cs, Th, U, Nb, Zr and Hf are strongly enriched, relative to chondritic abundances. Thus the outer portions of the moon sampled by the Imbrium event, and now represented by the Fra Mauro Formation, possessed high concentrations (100–200 × chondrites) for many elements, prior to the excavation of the mare basins. A correlation may exist between Gd/Eu and Zr/Hf ratios in lunar materials.     

Analysis of coupled axial and lateral deformation of roots in soil

Plant roots can help to stabilise slopes. Existing analytical models to predict their mechanical contribution are however limited: they typically focus on the ultimate limit state, employ various empirical factors, and ignore much of the underlying root-soil interaction. A new model was developed based on large deflection Euler-Bernoulli elastic beam theory that can be used to study the mobilisation of root strength under various loading conditions (direct shear and pull-out). Both lateral and axial loading of the root by the soil were incorporated, based on existing methodologies for foundation piles (p-y and t-z curves). The model is able to take the key parameters into account (root biomechanical properties, root architectural properties, and soil properties) while remaining quick to solve using a numerical boundary value problem solver. The model was compared with experimental direct shear test data using various root analogues (rubber, plastic, and wood) in dry sand with various densities and effective stress levels and was able to accurately predict the measured shear force-displacement behaviour. Comparison with experimentally measured pull-out force-displacement curves using rubber and wooden root analogues with various architectures in dry and partially saturated sands was also satisfactory. In the future, this model can aid with addressing long-standing problems in the root-reinforcement community: quantifying the effect of (sequential) mobilisation of root strength in direct shear, the effect of the angle at which the root crosses a shear plane, the effect of root topology on root-reinforcement or the effect of root bending, and root shear shear forces on root-reinforcement.