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The effectiveness of ocean–colour data assimilation in providing robust biological–parameter estimates for basin–scale ecosystem models is investigated for a phytoplankton–zooplankton–nutrient model using North Atlantic satellite chlorophyll data. The model is forced by annual cycles of mixed–layer depth, day length, photosynthetically available radiation and a temperature–dependent phytoplankton maximum growth rate.Although ocean–colour data are potentially limited in their ability to constrain model parameters because they provide information about the phytoplankton component only, this limitation is offset by the volume of data available covering the range of possible biogeochemical responses to similar and widely varying physical conditions. The results are improved by applying wintertime nutrient estimates based on in situobservations as an additional constraint.Repeatability of parameter estimates obtained from independent samples is examined. Results obtained using regional and basin–wide sampling strategies for obtaining the optimization dataset are compared and the geographic applicability of the calibrated models is assessed.

The discovery of evidence to suggest that copper ore was exploited at the Great Orme on a considerable scale in prehistory is of great significance in our understanding of the development of metalworking technology in the British Isles.In the past, the apparent absence from the archaeological record of a contemporaneous native mineral source for the production of copper and copper alloy artefacts during the Bronze Age has led to the assumption that raw materials, as well as metal technology, were imported from abroad. Alternatively, whilst accepting that local resources could have been exploited, it was assumed that these would have been obliterated by the mining operations of later centuries.There are now several sites on the British mainland and in Ireland which have been identified and dated as having been exploited for copper ores during the Bronze Age, of which a number, as on the Great Orme, had since seen intensive working during the 18th and 19th centuries AD. AS yet, much of the evidence has come essentially from surface excavations, but at the Great Orme surface excavation combined with underground exploration has revealed a system of workings of truly remarkable size. A series of 10 radiocarbon dates has been obtained from within the mine complex, indicating that working was carried out for over a thousand years spanning the Early to Late Bronze Age.The true extent of the surviving prehistoric workings is yet to be realized but present evidence indicates mining activity covering an area in excess of 24,000 square metres, incorporating passages totalling upwards of 5 km, penetrating to a vertical depth of 70 m.Much of the archaeological evidence contained within this report has been gained from detailed excavation carried out within surface workings, which in their own right constitute a sizeable part of the prehistoric mine. From the surface area presently exposed it is conservatively estimated that 40,000 cubic metres of material was removed during the Bronze Age. Much of the early technology represented within the surface workings reflects the technology employed in the deep workings, with the additional evidence of ancillary operations which would seem to relate solely to surface locations.Whilst the excavations reported in this paper relate to surface, or near surface, workings, they must be seen in the context of a labyrinthine complex of prehistoric workings recorded at depths of over yom (Jenkins & Lewis 1991; Lewis 1994). These deep workings are the subject of parallel studies to be reported elsewhere. The known underground and surface prehistoric workings are on a scale so far unparallelled in Britain and are of international significance. Elsewhere in Europe there is evidence for the mining of copper ores at Ai Bunar in Bulgaria dated to 5840 BC (Cernych 1978) and at Rudna Glava in former Yugoslavia dated to 4715 BC (Jovanovic 1979). Evidence for subsequent copper mining has been dated to 3785 BC in southern Spain (Rio Tinto area: Rothenburg & Blanco Freijeiro 1980) and to 3330 BC in Austria (Mitterberg; Pittioni 1951), marking an apparent development and extension westwards and northwards of copper technology. More recently, the dating of two sites in the south of France to around 3330 BC, at Cabrieres (Ambert et al. 1990) and Bouche Payrol, near Brusque (Barge 1985), has confirmed another area of Bronze Age working.

In recent years increasing attention has been focused on the palaeoeconomic interpretation of prehistoric sites, and a number of projects have been carried out both in Britain and abroad on plant and animal remains from archaeological sites with a view to interpreting subsistence patterns and activities of early communities. Though large-scale, systematic sampling and recovery of palaeoethnobotanical data has been carried out on several sites in the last ten years, the practice is still not widespread and has yet to be judged by its results. Fundamental issues relating to sampling, recovery and data presentation still require attention. Although studies of palaeoeconomic material have been done on Iron age sites in southern Britain, for example at Portway (Murphy 1977a) and Abingdon (Parrington 1978), as yet little evaluation of this evidence has taken place. The aim of this paper is to present, assess and compare the evidence from two such studies of different types of Iron Age site.

AbstractThe excavation of a multi-tumped oval barrow led to the discovery of a post-barrow flint industry, which utilized flint nodules incorporated in the mounds, thus damaging the original profile of the monument. 16,030 pieces of worked flint were recovered, 10,539 from the industrial levels. The material was analyzed by computer making use of programmes already developed for daily use by the M3 Archaeological Rescue Committee.

An empirically based mathematical model is presented which can simulate the major features of the interactions between ammonium and nitrate transport and assimilation in phytoplankton. The model (ammonium-nitrate interaction model), which is configured to simulate a generic microalga rather than a specified species, is constructed on simplified biochemical bases. A major requirement for parametrization is that the N:C ratio of the algae must be known and that transport and internal pool sizes need to be expressed per unit of cell C. The model uses the size of an internal pool of an early organic product of N assimilation (glutamine) to regulate rapid responses in ammonium-nitrate interactions. The synthesis of enzymes for the reduction of nitrate through to ammonium is induced by the size of the internal nitrate pool and repressed by the size of the glutamine pool. The assimilation of intracellular ammonium (into glutamine) is considered to be a constitutive process subjected to regulation by the size of the glutamine pool. Longer term responses have been linked to the nutrient history of the cell using the N:C cell quota. N assimilation in darkness is made a function of the amount of surplus C present and thus only occurs at low values of N:C. The model can simulate both qualitative and quantitative temporal shifts in the ammonium-nitrate interaction, while inclusion of a derivation of the standard quota model enables a concurrent simulation of cell growth and changes in nutrient status.

SummaryA detailed gravity survey, carried out to determine the thickness of the Bovey Tracey beds, is described. After removal of the regional gradient a residual gravity anomaly of ? 15 mgal can be attributed to the Bovey beds. This has been interpreted assuming that the clay density increases with depth and a maximum Bovey bed thickness of 1245 m is predicted. The western contact of the basin is shown to be faulted with dips of up to 63? and is possibly an extension of the Lustleigh?Sticklepath fault system.