Reconceptualising local community: environment, identity and threat

Summary Economic 'development' driven by global economic forces produces specific expressions of 'community' in places where large new economic projects are to be located. This paper draws on contemporary geopolitical literature to theorise community identity as partly formulated in response to external 'threats'. A comparative study of community mobilisation in response to proposals to locate coastal superquarries on the Isle of Harris, Outer Hebrides, Scotland, and Cape Breton, Nova Scotia, Canada, suggests the applicability of this theoretical framework for extending geographical analysis of community identity and the politics of place.     

Metamorphic an magmatic events in the Uweinat — Bir Safsaf Uplift (Western Desert/Egypt)

The Uweinat — Bir Safsaf Uplift, Western Desert/Egypt, four episodes of deformation and related metamorphism and anatexis occurred until the final cratonisation during the Late Pan-African event was completed. From that time on, probably six independent (Table 4) magmatic episodes can be recognized up to the Quaternary. This anorogenic type of magmatism is mainly related to a fracture system which originated in the Late Precambrian as a result of intraplate block faulting. Periodical reactivation of these older fracture zones throughout the Phanerozoic gave way to the different types of plutonic and volcanic rock assemblages.

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Zusammenfassung Die Grundgebirgsschwelle zwischen Gebel Uweinat und Bir Safsaf (Western Desert/ Ägypten) war während des Präkambriums durch vier Episoden von Deformation, Metamorphose und Anatexis gekennzeichnet. Die endgültige Kratonisierung erfolgte im Jungproterozoikum im Verlauf eines Pan-Afrikanischen Thermalereignisses. Die während des Jungproterozoikums als Folge großräumiger Intraplattentektonik entstandenen Bruchsysteme wurden während des Phanerozoikums periodisch reaktiviert. Die Platznahme anorogener Magmen erfolgte in mindestens sechs verschiedenen Zeiträumen hauptsächlich entlang dieser Bruchstrukturen.

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Résumé Le massif soulevé compris entre le Gebel Uweinat et Bir Safsaf, dans le Désert occidental de l'Egypte, a été le siège de 4 épisodes de déformations avec métamorphisme et anatexie jusqu'à sa cratonisation finale au cours de la Phase Pan-africaine tardive. A partir de ce moment, probablement six épisodes magmatiques indépendants peuvent être reconnus jusqu'au Quaternaire. Ce type anorogénique de magmatisme est principalement en relation avec un système de fractures qui a pris naissance au Précambrien supérieur comme le résultat d'une régime de fracturation intraplaque. La réactivation périodique des ces zones de fractures anciennes durant le Phanérozoïque a conduit à la formation de ces différents types d'associations de roches volcaniques et plutoniques.

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An OSL, radiocarbon and tephra isochron-based chronology for Birdlings Flat loess at Ahuriri Quarry, Banks Peninsula, Canterbury, New Zealand

OSL, radiocarbon dating of pedogenic carbonate and tephrochronology have been used in an attempt to provide a detailed and reliable chronology for Birdlings Flat loess, a thick, proximal loess found on the lower flanks of Banks Peninsula, Canterbury, New Zealand. In a ca 15 m thick section at Ahuriri Quarry the Kawakawa tephra isochron of 26,500 cal. yr BP is identified at a depth of ca. 1.35 m on the basis of glass counting and electron microprobe fingerprinting. Radiocarbon ages of filamentous or root pseudomorph carbonate increase down section from ca. 10,000 cal. yr BP at 2.80 m to ca. 30,000 ¹⁴C yr BP at 10.90 m. Ages from carbonate lining cracks are often out of sequence, indicating deep percolation by bypass flow down preferential flow paths. OSL ages show reversals with respect to each other, carbonate radiocarbon ages, and with the position and accepted age of Kawakawa tephra. Coincident radiocarbon and OSL ages at 3.85 m depth indicate that OSL ages are underestimates by at least 20%. Before OSL can be deemed a high accuracy dating method of the quatzo-feldspathic loess of South Island, New Zealand, more research into the causes of age underestimation and age reversals must be carried out. The last major episode of loess accumulation on the flanks of Banks Peninsula in Canterbury began before ca. 30,000 ¹⁴C yr BP (ca. 35,000 cal. yr BP) and possibly before 43,000 yr based on OSL.     

Ice, moraine, and landslide dams in mountainous terrain

We review recent work on ice, moraine, and landslide dams in mountainous terrain, thus complementing several comprehensive summaries on glacier dams in intracontinental and Arctic areas of low relief. We discuss the roles of tectonic and climatic forcing on ice-, moraine-, and landslide-dam formation and sudden drainage, and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel-bed rivers.Despite numerous reported failures of natural dams in mountain belts throughout the world, their relevance to long-term dynamics of mountain rivers remains poorly quantified. All types of dams exert local base-level controls, thus trapping incoming sediment and inhibiting fluvial bedrock incision. Pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates, suggesting that sudden dam failures are characterized by processes of catastrophic valley-floor aggradation, active-channel widening, and downstream dispersion of sediment, during which little bedrock erosion seems to be achieved.We find that, in the absence of direct evidence of former dams, a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam-forming process. This is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice, moraine, landslide, and polygenetic dams concomitant with climatic oscillations or earthquake disturbance. Hence, the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant.We recommend that future research on natural dams in mountainous terrain addresses (a) climate- and earthquake-controlled systematics in the pattern of formation and failure; (b) quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences; (c) elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams; (d) physical-based modelling of dam formation, failure, and routing of water and sediment outbursts; and (e) quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain.     

Wetter isn't better: global warming and food security in the Congo Basin

Over 20 million forest farmers practice slash and burn agriculture in the forests of the Congo Basin (Bahuchet and de Maret, 1995. State of Indigenous Populations Living in Rainforest Areas, European Commission DG XI Environment, Brussels). They rely on the long dry season (December–February north of the equator) to ensure that their new fields, cleared from regrowth forest, burn sufficiently well to deposit nutrients into the soil and to minimize the labor required to prepare the field for planting. Data from the Ituri forest in northeastern Democratic Republic of Congo show that the strength of the annual dry season (a) has a direct positive impact on the size of fields cleared each year by slash and burn farmers, and consequently on food production and the severity of the subsequent year's pre-harvest hunger period; and (b) is inversely related to total annual rainfall. These results suggest that the 1 mm/d increase in rainfall predicted for much of the Congo Basin by the 2050s may cause a basin wide increase in the frequency of heavy rains during the dry season, causing a reduction in the size of slash and burn farmers’ fields, and potentially a substantial increase in the food insecurity of poor rural families across the region.     

Sacred ground; the Maipés necropolis of north‐west Gran Canaria

Gran Canaria, like most of the Canary Islands, shows evidence for young basaltic volcanism in the form of cinder cones and valley‐hugging lava flows. These landforms were of no particular use to the aboriginal population, nor to the subsequent Spanish settlers, and young lava flows and lava fields are still referred to as ‘malpaís’ (badlands) in the Canary Islands. In north‐west Gran Canaria, one such lava flow fills the bottom of a steep‐sided valley, which reaches the sea at the present day village of Agaete. The lava flow erupted c. 3030 ± 90 yr bp and displays a total length of ～ 11 km. At its distal end, just outside Agaete, it hosts one of Europe’s largest and most important pre‐historic burial sites constructed of volcanic rock: the Maipés necropolis. Over 700 pre‐historic tombs (or tumuli) constructed from the aa‐type clinker materials have been identified on top of the valley‐filling lava flow. The up to soccer‐ball sized vesicular clinker fragments are sufficiently low in density to provide abundant, workable basalt blocks for the construction of the tumuli, allowing the pre‐hispanic aboriginal population to create a large and magnificent ‘sacred ground’ in an otherwise barren landscape.