Patterns of development in tourist accommodation enterprises on farms in England and Wales

The spatial distribution of UK farm-based tourist accommodation is not known in detail, although this type of facility has been an important element in the growth of rural tourism and the most common option for farm diversification. A database of farms in England and Wales offering tourist accommodation has been prepared and the individual entries georeferenced to enable their locations to be determined with respect to selected Scenic Areas (Areas of Outstanding Natural Beauty, Heritage Coasts and National Parks). Exploratory analysis of this database indicates a possible ‘neighbourhood effect’ in which the provision of farm-based accommodation within buffer zones immediately surrounding these designated areas has a higher level of penetration in the farming community than in more distant areas. Further research is outlined to examine the interaction between actors in farming and planning communities using the geographical framework presented here.     

Flood hazard management in the United States and the National Flood Insurance Program

The National Flood Insurance Program (NFIP) both provides flood insurance to floodplain occupants and encourages local communities to adopt floodplain land-use regulations. As well as providing the core of the federal non-structural flood hazard management effort, the NFIP is a central element in both state and local activities. A major issue influencing the success of the NFIP in curbing flood damages is its treatment of properties built before the adoption of floodplain regulations. The potential for using the NFIP to encourage floodproofing and influence post-flood hazard mitigation must be fully explored.     

Magnetohydrodynamics of stellar interiors

David Hughes, Robert Rosner and Nigel Weiss describe what was achieved during a programme on stellar magnetic fields at the Isaac Newton Institute in Cambridge. Over a four-month period more than 90 participants visited the Institute for a mixture of structured workshops and informal collaboration.     

Structural identification and mass spectral interpretation of C3n highly branched alkanes in sediment and aquatic extracts and evidence for their anthropogenic origin

The structures of two distinctive series of C_3n highly branched alkanes (HBAs), previously detected in sedimentary and aquatic extracts, were identified as polypropylene (PP) oligomers with different end groups, using gas chromatography (GC) and mass spectrometry (MS) correlation with diastereoisomeric mixtures of authentic C₁₅ and C₁₈ standards. A C₁₅ member of the earlier eluting series was assigned as 2,4,6,8-tetramethylundecane and a C₁₅ member of the later eluting series as 4,6,8-trimethyldodecane. The C_3n HBA GC–MS profiles of extracts from a typical PP GC sample vial lid were also shown to closely match those previously detected in sediment and water extracts, providing convincing evidence that the purported environmental occurrences are a result of PP contamination. Both C_3n series correspond to the first eluting diastereoisomer of the respective standards, also consistent with an industrial isotactic PP source. Mass spectra of all five standards are presented to help assignment of new polymethyl alkanes.     

40Ar-39Ar and Rb-Sr geochronology of high-pressure metamorphism and exhumation history of the Tavsanli Zone, NW Turkey

Geochronological investigations in high- and ultra-high-pressure metamorphic rocks are problematic since firstly the low temperatures lead to fine grain size and disequilibrium assemblages, and secondly the problem of “excess argon” affects ⁴⁰Ar-³⁹Ar systematics, the most commonly used isotopic system. The Tavsanli Zone is a belt of high-pressure low-temperature (HP-LT) rocks spanning NW Turkey and is one such region where previous geochronological studies have produced a range of estimates for the age of HP-LT metamorphism, raising the question of whether they are geologically significant. This study presents new data from the Tavsanli Zone; ⁴⁰Ar-³⁹Ar ages are in the range 60 Ma to 175 Ma, whilst Rb-Sr ages are restricted to 79.7 Ma to 82.8 Ma, confirming the presence of excess argon. Detailed ultra-violet laser ablation microprobe (UVLAMP) studies have revealed younger ⁴⁰Ar-³⁹Ar ages in the cores of coarser white micas, which in conjunction with ⁴⁰Ar-³⁹Ar ages from the finest grained lithologies and the Rb-Sr white mica crystallisation ages, constrain the post-HP-LT metamorphism exhumation rates of these rocks. Petrological and regional constraints suggest that syn-subduction exhumation and cooling took place initially by synchronous subduction and exhumation by underplating. This is followed by a phase of syn-continent-continent collision at a rate of approximately 1.5 mma⁻¹ and exhumation to the surface via thrusting. The ⁴⁰Ar-³⁹Ar hornblende data from a granodiorite intruding the HP-LT rocks constrain the later parts of exhumation path. This study highlights the importance of a multi-system geochronological approach when attempting to determine the history of HP-LT rocks. Received: 12 May 1998 / Accepted: 21 April 1999     

Geological interpretation of current subsidence and uplift in the London area,UK, as shown by high precision satellite-based surveying

Long term planning for flood risk management in coastal areas requires timely and reliable information on changes in land and sea levels. A high resolution map of current changes in land levels in the London and Thames estuary area has been generated by satellite-based persistent scatterer interferometry (PSI), aligned to absolute gravity (AG) and global positioning system (GPS) measurements. This map has been qualitatively validated by geological interpretation, which demonstrates a variety of controlling influences on the rates of land level change, ranging from near-surface to deep-seated mechanisms and from less than a decade to more than 100,000 years’ duration.     

Post-collision magmatism and tectonics in northwest Anatolia

A suite of biotite-hornblende granodiorite intrusions has been emplaced into blueschist-facies metasediments in northwest Anatolia, following collision between two continental margins, now represented by the Tavanli and Sakarya zones. The ⁴⁰Ar/³⁹Ar ages of phengites and glaucophanes from the blueschists, metamorphosed under unusually high P-low T conditions (P=20±2 kbar, T=430±30° C), suggest that metamorphism apparently occurred over a period spanning at least 20 Ma from 108 to 88 Ma. Post-tectonic granodiorites were emplaced during the Eocene (53 to 48 Ma) resulting in a cordierite and andalusite-bearing thermal aureole, indicative of pressures of 3 kbar. Trace-element systematics of the granodiorites are consistent with a derivation either from mantle-derived magmas by fractional crystallisation in shallow magma chambers, or from anatexis of crustal lithologies of internediate composition at pressures <10 kbar. The preservation of high P-low T assemblages in the blueschists together with the range of ages determined for blueschist-facies metamorphism are indicative of rapid exhumation of delaminated fragments from a subducted continental margin. However decompression melting of the crust is unlikely to have been a significant cause of magmatism, both because exhumation of the blueschists from deep crustal levels predated magmatism by at least 25 Ma, and because of the small melt fraction (<0.1) that may be generated in crustal lithologies by this process. Melting in the mantle wedge is required either to generate a primary melt for the derivation of magmas of intermediate composition or to provide an advective heat source for crustal melting. The cause of melt formation in the upper mantle may be related to the termination of subduction following collision during the Mid-Eocene.     

Syn‐sedimentary salt diapirism as a control on fluvial‐system evolution: an example from the proximal Permian Cutler Group,SE Utah,USA

Loading of subsurface salt during accumulation of fluvial strata can result in halokinesis and the growth of salt pillows, walls and diapirs. Such movement may eventually result in the formation of salt‐walled mini‐basins, whose style of architectural infill may be used to infer both the relative rates of salt‐wall growth and sedimentation and the nature of the fluvial‐system response to salt movement. The Salt Anticline Region of the Paradox Basin of SE Utah comprises a series of elongate salt‐walled mini‐basins, arranged in a NW‐trending array. The bulk of salt movement occurred during deposition of the Permian Cutler Group, a wedge of predominantly quartzo‐feldspathic clastic strata comprising sediment derived from the Uncompahgre Uplift to the NE. The sedimentary architecture of selected mini‐basin fills has been determined at high resolution through outcrop study. Mini‐basin centres are characterized by multi‐storey fluvial channel elements arranged into stacked channel complexes, with only limited preservation of overbank elements. At mini‐basin margins, thick successions of fluvial overbank and sheet‐like elements dominate in rim‐syncline depocentres adjacent to salt walls; many such accumulations are unconformably overlain by single‐storey fluvial channel elements that accumulated during episodes of salt‐wall breaching. The absence of gypsum clasts suggests that sediment influx was high, preventing syn‐sedimentary surface exposure of salt. Instead, fluvial breaching of salt‐generated topography reworked previously deposited sediments of the Cutler Group atop growing salt walls. Palaeocurrent data indicate that fluvial palaeoflow to the SW early in the history of basin infill was subsequently diverted to the W and ultimately to the NW as the salt walls grew to form topographic barriers. Late‐stage retreat of the Cutler fluvial system coincided with construction and accumulation of an aeolian system, recording a period of heightened climatic aridity. Aeolian sediments are preserved in the lees of some salt walls, demonstrating that halokinesis played a complex role in the differential trapping of sediment.     

Anatomy and facies distribution of terminal lobes in ephemeral fluvial successions: Jurassic Tordillo Formation,Neuquén Basin,Argentina

In terminal fluvial-fan systems, characteristic proximal to distal variations in sedimentary architectures are recognized to arise from progressive downstream loss of water discharge related to both infiltration and evaporation. This work aims to elucidate downstream trends in facies and architecture across the medial and distal zones of terminal-fan systems, which record transitions from deposits of channel elements to lobe-like and sheet-like elements. This is achieved via a detailed characterization of ancient ephemeral fluvial deposits of the well-exposed Kimmeridgian Tordillo Formation (Neuquén Basin, Argentina). The fine sand-prone and silt-prone succession associated with the medial to distal sectors of the system has been studied to understand relationships between depositional processes and resulting architectures. Facies and architectural-element analyses, and quantification of resulting sedimentological data at multiple scales, have been undertaken to characterize sedimentary facies, facies transitions, bed types, architectural elements and larger-scale architectural styles. Eight bed types with distinct internal facies transitions are defined and interpreted in terms of different types of flood events. Channelized and non-channelized architectural elements are defined based on their constituent bed types and their external geometry. The most common elements are terminal lobes, which are composite bodies within which largely unconfined sandy deposits are stacked in a compensational manner; a hierarchical arrangement of internal components is recognized. Proximal feeder-channel avulsion events likely controlled the evolution of terminal-lobe elements and their spatiotemporal shifts. Stratigraphic relations between architectural elements record system-wide trends, whereby a proximal sector dominated by channel elements passes downstream via a gradational transition to a medial sector dominated by sandy terminal-lobe elements, which in turn passes further downstream to a distal sector dominated by silty terminal lobe-margin and fringing deposits. This work enhances current understanding of the stratigraphic record of terminal fluvial systems at multiple scales, and provides insight that can be applied to predict the facies and architectural complexity of terminal fluvial successions.