U-series chronologies of the emerged coral limestone terraces on Barbados, West Indies, together with those of the terraces from New Guinea, have formed the basis for most late Pleistocene eustatic models. The so-called “Barbados sea level model” has been challenged in recent years, however. A major issue is whether during oxygen isotope stage 5e, when Rendezvous Hill reef complex on Barbados Island formed, the sea rose above the present position for one relatively brief period of <10,000 yr, or for two or more periods spanning approximately from 140,000 to 115,000 yr B.P. Evidence for the latter scenario has not come from initial studies of Barbados but from elsewhere; it is also inconclusive because of the dating uncertainties involved. We have carried out careful redeterminations of U-series ages on a suite of 29 Acropora palmata samples systematically collected from four of the lowest terraces on the island. Diagenetic disturbance may have caused the age spreads at some sampling outcrops. A model for the diagenetic exchange of uranium isotopes in coral samples with those in groundwater explains the anomalous 234U/238U ratios in samples with apparently unaltered mineralogy (aragonite) and trace element (Mg and Sr) chemistry. It shows that age dispersions of 5–10% can be engendered by a U exchange coefficient of the order of 10−6 yr−1. The lower-limit terrace ages, estimated from averaging the multiple measurements, are 81,000 ± 2000 yr (Worthing), 105,000 ± 1000 yr (Ventnor), 120,000 ± 2000 yr (Maxwell), and 117,000 ± 3000 yr (Rendezvous Hill). No evidence was found of previously inferred bipartite sea levels centering around 118,000 and 135,000 yr ago. This study documents the need of dating coral with the high precision/sensitivity mass-spectrometric techniques for future resolution of the temporal relationships among sea level changes, climate oscillations, and astronomical forcing—relationships originally addressed by the Barbados sea level model.

We have recently developed a set of equations of state based on the nuclear energy density functional theory providing a unified description of the different regions constituting the interior of neutron stars and magnetars. The nuclear functionals, which were constructed from generalized Skyrme effective nucleon-nucleon interactions, yield not only an excellent fit to essentially all experimental atomic mass data but were also constrained to reproduce the neutron-matter equation of state as obtained from realistic many-body calculations.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

El Berrocal is an abandoned uranium mine in a mineralised quartz vein hosted by a Hercynian granite in central Spain. This mine is the focus of an international project to characterise and model natural elemental migration in a fractured-rock environment as an aid to understanding and predicting processes that may occur in a geological repository for radioactive wastes.

Uranium in the mineralised quartz vein has been shown to have originated from the orthomagmatic uraninite in the granite with the elemental removal and migration occurring predominately by hydrothermal fluids. Mobilisation of uranium from the mineralised quartz vein and from granite adjacent to hydraulically-active fractures away from the vein occurred over the geologically-recent past and in the present-day. The most recent mobilisation is evidenced by dissolution features seen in SEM photomicrographs; mineral growth and sorption signatures identified by enhanced uranium concentrations on the surfaces of preexisting minerals; and measured disequilibrium in the uranium series for whole rock close to fracture walls.

Present-day groundwaters in the studied area are young meteoric waters. They are generally calcium-sulphate enriched, oxidising and mildly acidic near the surface, becoming more bicarbonate-rich with near neutral pH in the deeper zones, except around the mineralised vein where the waters are acid (pH around 3) due to oxidisation of the sulphide minerals. No deep, chemically-reducing groundwaters have yet been identified in the El Berrocal boreholes.

This paper discusses some of the results from a natural geochemical analogue study on the Krunkelbach mine, F.R.G. These data, based largely on uranium series disequilibrium measurements, are used to compare the results of groundwater modelling programmes with observations made in the mine.

This paper presents the results of a physical, chemical and actinide characterisation of the groundwater in a shallow glacial sand aquifer, in which tracer tests aie currently being conducted by t lu- British Geological Survey (BGS).

Uranium Series disequilibrium measurements have been used to determine the partition of natural actinide activities betueen the particulate, colloid and solution phases of the groundwnters from sevpral geologically dissimilar sites. The activity fractions associated with the colloid phase were found to be (0.1–0.52) for uranium and (1–52) for thorium.

Scanning electron microscopy analysis yielded values of 103−101 particles/litre for the colloid concentration. Mean mobilities for the colloids determined by electrophoresis were in the range -(1–2) × 10−6 m2S−1v−1.