Mass spectrometric dating of flowstones from Stump Cross Caverns and Lancaster Hole,Yorkshire: palaeoclimate implications

A terrestrial flowstone sequence 97 cm thick from Stump Cross Caverns, Yorkshire, has been dated by both mass spectrometric and alpha spectrometric ²³⁸U-²³⁴U-²³⁰Th dating, and is demonstrated to have been deposited predominantly during interstadial periods over the last 170 ka, with no growth in periods of glaciation or within the Oxygen Isotope Stage 5 interglacial. Growth also occurs within Oxygen Isotope Stages 4 and 6, the former possibly correlating with interstadials recognised in high-resolution ice and ocean-core records. Comparison with the timing of growth of a mass spectrometrically dated Lancaster Hole flowstone, also from the same region, demonstrates only limited agreement. These differences are due to two factors limiting deposition at Stump Cross: flooding of the cave passage in warm periods, and the development of continuous permafrost or glacier cover in periods of severe climatic deterioration. Deposition at Lancaster Hole was controlled by limitations in ground-water supply rather than flooding of the cave passage. The results presented here demonstrate that in addition to regional palaeoclimate factors, local site conditions may limit speleothem growth. We conclude that in future palaeoclimate studies, the growth record from several coeval speleothem samples must be considered before a regional palaeoclimate interpretation can be made.     

Late Devensian river and floodplain dynamics and related environmental change in northwest Europe,with particular reference to a site at Woolhampton,Berkshire, England

Marked fluctuations in Late-glacial climate are correlated with significant changes in river behaviour and floodplain environment across much of northwest Europe. Evidence from a new site in the Kennet Valley provides a rare comprehensive picture of varying fluvial regime and local vegetation during this interval. Chronological control for the site is provided by biostratigraphical and morphostratigraphical correlations with other sites in the region, and by radiocarbon dating of carefully selected material. Preservation of the sedimentary sequence was facilitated by its occurrence within a large depression in the underlying bedrock. The origin of this depression is uncertain, perhaps reflecting subsidence or scour. Following the Last Glacial Maximum, a nival regime braided river dominated by floods deposited sandy gravels under stadial conditions. A large channel infilled by fine sediments during the latter part of the Windermere Interstadial indicates a fall in flow competence at a time of increased floodplain vegetation, most notably the appearance of tree birch. Variations in sediments and vegetation suggest fluctuations in the floodplain environment, reflecting complex vegetation dynamics and possibly climate forcing. During the Loch Lomond/Younger Dryas Stadial, a nival, braided regime was re-established, accompanied by the disappearance of tree birch.     

REGIONAL IDEAS AND THE MONTANA-ALBERTA BORDERLANDS*

ABSTRACT. The borderland concept is not often applied to the U.S. West's northern boundary, but the northwestern Great Plains have been the subject of at least two border-straddling regional conceptions: Whoop-Up Country, based on a shared regional history; and Chinook Country, based on a shared natural environment. Both ideas can be found to varying degrees in northern Montana and southern Alberta, but as expressions of regional distinction, their significance and meaning differ sharply north and south of the international boundary. In borderlands such as these, nationalism and regionalism intersect.     

Subduction Style Magmatism in a Non-subduction Setting: the Colville Igneous Complex, NE Washington State, USA

The Colville Igneous Complex is located within the Eocene MagmaticBelt of the North American Cordilleran interior. It straddlesthe US–Canadian border in northeast Washington and southernBritish Columbia. The complex consists of three intrusive andtwo extrusive phases, the first extrusive phase being contemporaneouswith the latter two intrusive phases. As a consequence of sub-solidusre-equilibration in the plutonic rocks, this study concentrateson the two extrusive phases, the Sanpoil Volcanic Formationand the Klondike Mountain Formation. The Sanpoil Volcanic Formationconsists of andesites, dacites and rare trachyandesites (SiO₂= 55–70 wt %) exhibiting a slight decrease in total alkalis(Na₂O + K₂O) with increasing silica. The Klondike Mountain Formationconsists of basalts, basaltic andesites, andesites, dacitesand rhyolites (SiO₂ = 51–75 wt %) with total alkalis increasingwith increasing silica. The calc-alkaline affinity of the rocksof the Colville Igneous Complex, coupled with the presence ofa ‘subduction signature’ of enriched large ion lithophileelements (LILE) and depleted high field strength elements (HFSE),has traditionally been attributed to petrogenesis in a subduction-relatedmagmatic arc, the ‘Challis Arc’. New trace and rareearth element and isotopic data (⁸⁷Sr/⁸⁶Sr_i,     

A recent build-up of atmospheric CO2 over Europe. Part 1: observed signals and possible explanations

We analysed interannual and decadal changes in the atmospheric CO₂ concentration gradient (ΔCO₂) between Europe and the Atlantic Ocean over the period 1995–2007. Fourteen measurement stations are used, with Mace-Head being used to define background conditions. The variability of ΔCO₂ reflects fossil fuel emissions and natural sinks activity over Europe, as well as atmospheric transport variability. The mean ΔCO₂ increased by 1–2 ppm at Eastern European stations (∼30% growth), between 1990–1995 and 2000–2005. This built up of CO₂ over the continent is predominantly a winter signal. If the observed increase of ΔCO₂ is explained by changes in ecosystem fluxes, a loss of about 0.46 Pg C per year would be required during 2000–2005. Even if severe droughts have impacted Western Europe in 2003 and 2005, a sustained CO₂ loss of that magnitude is unlikely to be true. We sought alternative explanations for the observed CO₂ build-up into transport changes and into regional redistribution of fossil fuel CO₂ emissions. Boundary layer heights becoming shallower can only explain 32% of the variance of the signal. Regional changes of emissions may explain up to 27% of the build-up. More insights are given in the Aulagnier et al. companion paper.     

Geological investigation and optical dating of Quaternary siliciclastic sediments near Apalachicola,North‐west Florida,USA

Ground penetrating radar and single‐aliquot regenerative‐dose optically stimulated luminescence were used to determine the depositional environments and age of unconsolidated siliciclastic sediments near Apalachicola, Florida. Five direct‐push cores, five vibracores and 28 optically stimulated luminescence samples were collected, as well as 7 km of ground penetrating radar data. A new model of cosmic dose rate calculation, which removes the effect of a much younger aeolian cap, was utilized to calculate more representative optically stimulated luminescence ages. Five radar facies were identified based on reflector amplitude and orientation. The resulting data indicate that the Tertiary/Quaternary Shelly Sediments were deposited before marine isotope stage 6, the Quaternary Alluvium was deposited during marine isotope stage 6 and the Quaternary Beach Ridge and Dune was deposited during the marine isotope stage 5e sea‐level highstand, which peaked at approximately 2·5 m above present sea‐level in this area.     

Facies architecture of individual basin‐plain turbidites: Comparison with existing models and implications for flow processes

Current understanding of submarine sediment density flows is based heavily on their deposits, because such flows are notoriously difficult to monitor directly. However, it is rarely possible to trace the facies architecture of individual deposits over significant distances. Instead, bed‐scale facies models that infer the architecture of ‘typical’ deposits encapsulate current understanding of depositional processes and flow evolution. In this study, the distribution of facies in 12 individual beds has been documented along downstream transects over distances in excess of 100 km. These deposits were emplaced in relatively flat basin‐plain settings in the Miocene Marnoso Arenacea Formation, north‐east Italy and the late Quaternary Agadir Basin, offshore Morocco. Statistical analysis shows that the most common series of vertical facies transitions broadly resembles established facies models. However, mapping of individual beds shows that they commonly deviate from generalized models in several important ways that include: (i) the abundance of parallel laminated sand, suggesting deposition of this facies from both high‐density and low‐density turbidity current; (ii) three distinctly different types of grain‐size break, suggesting waxing flow, erosional hiatuses and bypass of silty sediment; (iii) the presence of mud‐rich debrites demonstrating hybrid flow deposition; and (iv) dune‐scale cross‐lamination in fine‐medium grained sandstones. Submarine sediment density flows in basin‐plain settings flow over relatively simple topography. Yet, their deposits record complex flow events, involving transformation between different flow types, rather than the simple waning surges often associated with the distal parts of turbidite systems.     

Comparative evolution of statewide Geographic Information Systems in Ohio

Abstract

This paper describes four autonomous Geographic Information Systems operating at a statewide level in Ohio (USA). All were initiated at various times in the 1970s and 1980s. They are operated by branches of state government, namely the Department of Natural Resources, the Ohio Environmental Protection Agency, the Ohio Department of Transportation, and the Public Utilities Commission of Ohio. A critical review of the operations and institutional contexts of these four systems shows evolution from in-house software development to third party suppliers, from coarse resolution grid cells to high accuracy vector data, from large dedicated GIS staffs to application-specific users augmented by smaller GIS support staffs, and from agency-dependent databases to inter-agency database sharing as technology improves and user needs and databases increase.     

The Thailand Land Titling Project First steps in a parcel-based LIS†

Abstract

This paper describes the progress of the Land Titling Project in Thailand, the objectives of which are to issue titles to all eligible landholders, to improve land administration, to remap all urban areas and to establish a land valuation system. The significance of this project in the context of land information systems (LIS) is that its operations are essential preliminary steps in the development of an effective information system and its experience will therefore be of value in the many countries which are contemplating the establishment of such a system. Special features of the project which contribute to its success are outlined. The project will take twenty years and LIS will be a major activity in the second five-year phase (1990-1994), involving a multi-layer LIS in the Bangkok metropolis and parcel databases in provincial Land Offices.