U and Th zonation in Fish Canyon Tuff zircons: Implications for a zircon (U-Th)/He standard

The inability to accurately determine the distribution of U and Th in zircon crystals analysed using (U-Th)/He is a major source of error, and limits the confidence in subsequent data interpretation. The Fish Canyon Tuff (FCT) zircon standard shows (U-Th)/He age reproducibility in excess of ±10%. We have tested the extent to which this is due to U and Th zonation using a combination of cathodoluminescence and ion probe analysis of a population of FCT zircons. Primarily we find that FCT zircons exhibit extreme U and Th zonation, and the population has large inter-crystalline variability. Furthermore, the net cathodoluminescence intensity from the FCT zircons is negatively correlated with U and Th concentration, allowing cathodoluminescence emission to be used as a proxy for U and Th zonation. This correlation was exploited to constrain the U and Th zonation within the crystal population, and to show that the poor age reproducibility of the FCT zircons is consistent with the observed zonation.     

From smallholders to transnationals: The impact of changing consumer preferences in the EU on Ghana’s pineapple sector

This paper explores the impact that a new type of pineapple, and subsequent changing consumer preferences in the Global North, has had on the livelihoods of pineapple growers in Ghana. The paper starts by tracing how research and development in Costa Rica by the world’s largest producers of pineapple, Del Monte and Dole, have resulted in a new variety MD2. This new pineapple type has been marketed in the EU through campaigns carried out by plantation companies via supermarkets. Consumer preferences have subsequently switched to MD2 away from the varieties which previously dominated the market, including the Ghanaian grown Smooth Cayenne. Ghanaian smallholders have experienced a dramatic drop in the demand for Smooth Cayenne and are unable to switch to growing MD2. The Ghanaian pineapple sector is consequently being restructured with large-scale pineapple farms, principally run by transnational companies, growing large quantities of MD2 for export. Through a detailed empirical study of the changing livelihoods of pineapple growers in two settlements in Ghana, we show how smallholders have been affected in differing ways as transnational companies have increasingly entered the market. Recent attempts to incorporate smallholders as producers of niche pineapple products are discussed. The paper illustrates the mutual benefits of linking global value chain analysis with livelihood analysis.     

Fish remains from the Formative Period (1000 BC–AD 400) of Lake Titicaca, Bolivia: Zooarchaeology and taphonomy

This paper presents a detailed zooarchaeological study of fish remains from the site of Kala Uyuni, Bolivia. The fish remains of 31 flotation samples from different archaeological contexts and dated to the Formative Period (1000 BC–AD 400) are described in terms of frequency, weight, taxa distribution, sizes, skeletal representations, and exposure to heat. The results confirm the importance of fish in the diet of the inhabitants of the site and provide insights about the particularities of their exploitation, consumption, and differential discard across the site throughout time. A strong decline in the procurement and consumption of fish is observed for the Late Formative which seems to be a consequence of both environmental and social processes.     

The effect of African growth on future global energy,emissions, and regional development

Today Africa is a small emitter, but it has a large and faster-than-average growing population and per capita income that could drive future energy demand and, if unconstrained, emissions. This paper uses a multi-model comparison to characterize the potential future energy development for Continental and Sub-Saharan Africa under different assumptions about population and income. Our results suggest that population and economic growth rates will strongly influence Africa’s future energy use and emissions. We show that affluence is only one face of the medal and the range of future emissions is also contingent on technological and political factors. Higher energy intensity improvements occur when Africa grows faster. In contrast, climate intensity varies less with economic growth and it is mostly driven by climate policy. African emissions could account for between 5 % and 20 % of global emissions, with Sub-Saharan Africa contributing between 4 % and 10 % of world emissions in 2100. In all scenarios considered, affluence levels remain low until the middle of the century, suggesting that the population could remain dependent on traditional bioenergy to meet most residential energy needs. Although the share of electricity in final energy, electric capacity and electricity use per capita all rise with income, even by mid-century they do not reach levels observed in developed countries today.     

Sequence stratigraphy of the Mancos Shale,lower Tres Hermanos Formation,and coeval middle Cenomanian to middle Turonian strata,southern New Mexico,USA

Sequence stratigraphic analysis of four widely spaced outcrops of middle Cenomanian to middle Turonian strata deposited in the Western Interior foreland basin in southern New Mexico, USA, defines ten sequence boundaries in a marine shale‐rich interval ca 200 m thick. The majority of sequence boundaries are based on basinward shifts in lithofacies characterized by either a non‐Waltherian contact between distal‐bar or lower shoreface sandstone and underlying lower offshore shale, or an erosional contact between distal‐bar or lower shoreface sandstone and underlying upper offshore shale. The sequence boundaries commonly correlate basinward to packages of storm‐deposited sandstone and to beds of sandy grainstone composed of winnowed inoceramid shell fragments. In several cases, however, the sequence boundaries pass basinward into presumably conformable successions of lower offshore shale. Maximum flooding surfaces within the sequences are represented by one or more beds of locally phosphatized globiginerid wackestone and packstone or exist within a conformable succession of lower offshore shale. Following initial south/south‐westward transgression into the study area, the regional trend of palaeoeshorelines was north‐west to south‐east, although isopach data indicate that lobes of sandstone periodically spread south‐eastward across the study area. The ten sequences in the study area are arranged into a third‐order composite megasequence that is characterized by overall upward‐deepening followed by upward‐shallowing of sequences. The composite megasequence is similar but not identical to the previously established T‐1 transgression and R‐1 regression in New Mexico. Based on radioisotopic dates of bentonites, the average frequency of the sequences within the study area was ca 327 kyr, which is consistent with fourth‐order cycles of ca 400 kyr interpreted in coeval marine strata elsewhere in the world.     

Relative sea‐level change and postglacial isostatic adjustment along the coast of south Devon,United Kingdom

Previous sea‐level studies suggest that southwest Britain has the fastest subsiding coastline in the United Kingdom, but tide‐gauge data, GPS and gravity measurements and geophysical models show little evidence of anomalous subsidence in this region. In this paper we present 15 new sea‐level index points from four coastal barrier systems in south Devon. Eight are from compaction‐free basal sediments and others were corrected for autocompaction. Our data suggest that relative sea level along the south Devon coastline has risen by 21 ± 4 m during the past 9000 years. Sea‐level rise slowed during the middle and late Holocene and a rise of 8 ± 1 m has occurred since ca. 7000 cal. yr BP. Anomalous ages for many rejected points are attributed to sediment reworking during barrier transgression. The relative sea‐level history during the early and middle Holocene shows a good fit with geophysical model predictions, but the geological and modelled data diverge in the later Holocene. Unlike the geophysical models, sea‐level index points cannot differentiate between late Holocene relative sea‐level histories of south Devon and southwest Cornwall. It is suggested that this discrepancy can be resolved by obtaining additional high‐quality sea‐level index points covering the past 4000 years. Copyright © 2008 John Wiley & Sons, Ltd.     

Geology of London,UK

The population of London is around 7 million. The infrastructure to support this makes London one of the most intensively investigated areas of upper crust. However construction work in London continues to reveal the presence of unexpected ground conditions. These have been discovered in isolation and often recorded with no further work to explain them. There is a scientific, industrial and commercial need to refine the geological framework for London and its surrounding area. This paper reviews the geological setting of London as it is understood at present, and outlines the issues that current research is attempting to resolve.     

Three-dimensional numerical simulations of the Downie Slide to test the influence of shear surface geometry and heterogeneous shear zone stiffness

Massive slow-moving landslides often exhibit deformation patterns which vary spatially across the landslide mass and temporally with changing boundary conditions. Understanding the parameters controlling this behaviour, such as heterogeneous material properties, complex landslide geometry and the distribution of groundwater, is fundamental when making informed design and hazard management decisions. This paper demonstrates that significant improvements to the geomechanical analysis of massive landslides can be achieved through rigorous, three-dimensional numerical modelling. Simulations of the Downie Slide incorporate complex shear zone geometries, multiple water tables and spatial variation of shear zone stiffness parameters to adequately reproduce real slope behaviour observed through an ongoing site monitoring program. These three-dimensional models are not hindered by shortfalls typically associated with two-dimensional analysis, for example the ability to accommodate lateral migration of material, and they out-perform more simplified three-dimensional models where bowl-shaped shear geometries are incapable of reasonably reproducing observed deformation patterns.