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This digital document is a journal article from Biological Conservation, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The Albertine Rift is one of the most important regions for conservation in Africa. It contains more vertebrate species than any other region on the continent and contains more endemic species of vertebrate than any other region on mainland Africa. This paper compiles all currently known species distribution information for plants, endemic butterfly species and four vertebrate taxa from the Albertine Rift. The literature on fish species richness and endemism is also reviewed to assess the importance of the larger lakes in the Rift for conservation. We use data from 38 protected and unprotected areas to prioritise sites within the Albertine Rift for conservation based upon their numbers of endemic and globally threatened species. Virunga and Kahuzi Biega National Parks and Itombwe Massif in Democratic Republic of Congo, Bwindi Impenetrable and Kibale National Parks in Uganda, and Nyungwe National Park in Rwanda rank highest in terms of numbers of both endemic and globally threatened species. Six conservation landscapes are described that include most of these sites and it is argued that a focus on these landscapes may be a more holistic method to ensure the safety of the priority areas of the Albertine Rift.

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This digital document is a journal article from Palaeogeography, Palaeoclimatology, Palaeoecology, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The Pliocene-Pleistocene Konso Formation defined here is >180 m thick and is extensively exposed in the Konso area at the southernmost part of the Ganjuli graben of the Main Ethiopian Rift. The Konso area is known for its abundant vertebrate fossils, including those of Homo erectus and Australopithecus boisei, and its rich Acheulean archaeological assemblages. The fluvial, floodplain, lake margin, and lacustrine sediments of the formation were mostly deposited between 1.9 and 1.4 Ma, based on single-crystal ^4^0Ar/^3^9Ar ages of interbedded marker tuffs. The formation is subdivided into the Sorobo, Turoha, Kayle, and Karat Members, in ascending stratigraphic order. Each member contains dark brown or dark grey clay beds of lake margin and/or lacustrine origin, suggesting the recurrence of lake environments. Most of the fossils and artifacts derive from whitish grey or brown silt, sand, and gravel beds widely exposed between the finer sediments. These beds appear to have been deposited in an emerging marginal floodplain following repeated recession of the palaeo-lake. The depositional history of the Konso Formation reveals aspects of Quaternary rifting at the southern terminus of the Main Ethiopian Rift. Rifting, subsidence, and sedimentation in the Ganjuli graben occurred in the Konso area mainly between 1.9 and 1.4 Ma, while active faulting with associated volcanism during the Pleistocene was mostly confined to the middle part of the graben between Lakes Abaya and Chamo and to the Segen basin east of Konso. A shift of rift-related faulting and subsidence from the Konso area eastward to the Segen basin is likely to have resulted in the erosion and exposure of the fossiliferous Konso Formation.

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This digital document is a journal article from Earth Science Reviews, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The ‘Snowball Earth’ model of Hoffman et al. [Science 281 (1998) 1342] has stimulated renewed interest in the causes of glaciation in Earth history and the sedimentary, stratigraphic and geochemical response. The model invokes catastrophic global Neoproterozoic refrigerations when oceans froze, ice sheets covered the tropics and global temperatures plummeted to -50 ^oC. Each event is argued to be recorded by tillites and have lasted up to 10 million years. Planetary biological activity was arrested only to resume in the aftermath of abrupt and brutal volcanically generated ‘greenhouse’ deglaciations when global temperatures reached +50 ^oC. The ‘Cambrian explosion’ is regarded by some as a consequence of post-Snowball glacioeustatic flooding of continental shelves. We shall show by a systematic review of the model that it is based on many long standing assumptions of the character and origin of the Neoproterozoic glacial record, in particular, ’tillites’, that are no longer valid. This paper focusses on the sedimentological and stratigraphic evidence for glaciation in the light of current knowledge of glacial depositional systems. By integrating this analysis with recent understanding of the tectonic setting of Neoproterozoic sedimentary basins, an alternative ‘Zipper-rift’ hypothesis for Neoproterozoic glaciations is developed. The ‘Zipper-rift’ model emphasises the strong linkage between the first-order reorganisation of the Earth’s surface created by diachronous rifting of the supercontinent Rodinia, the climatic effects of uplifted rift flanks and the resulting sedimentary record deposited in newly formed rift basins. Initial fragmentation of Rodinia commenced after about 750 Ma (when the paleo-Pacific Ocean started to form along the western margin of Laurentia) and culminated sometime after 610 Ma (with the opening of the paleo-Atlantic Ocean on the eastern margin of Laurentia). Breakup is recorded by well-defined ‘tectonostratigraphic’ successions that were deposited in marine rift basins. The base of each succession is characterised by coarse-grained synrift strata consisting of mass flow diamictites and conglomerates (many of the ’tillites’ of the older literature). These facies are interbedded with large olistostromes and contain clastic carbonate debris derived from landsliding of fault scarps along rifted carbonate platforms. Diamictites and conglomerates are dominantly the product of subaqueous mass flow and mixing of coarse and fine sediment populations (the term mixtite has been used in the past). These facies are not uniquely glacial and are produced regardless of climate and latitude. Synrift deposits commonly pass up into thick slope turbidites recording enhanced subsidence and are capped by uppermost shallow marine strata that record a reduction in subsidence rates and overall basin shallowing. Tectonostratigraphic ‘cycles’ can attain thicknesses of several kilometres, but have been commonly misinterpreted as recording globally synchronous ‘glacioeustatic’, falls and rises in sea level. In fact, eustatic sea-level changes in rift basins are suppressed as a result of a strong tectonic control on relative water depths. The great length of newly formed rifted margins around the long perimeter of Laurentia (<20,000 km) ensured that deposition of tectonostratigraphic successions occurred diachronously as in the manner of a zipper between approximately 740 and 610 Ma. Some successions show a definite glacial influence on sedimentation as a consequence of latitude or strong tectonic uplift, but many do not. Regardless, all deposits record a fully functioning hydrological cycle entirely at odds with a supposed fully permafrozen planet. Mapping of those deposits where a definite glacial imprint is apparent indicates that Neoproterozoic glaciation(s) were likely regional or hemispheric in scope and latitudinally constrained. They were perhaps no more severe than other glaciations recorded in Earth history. The regional distribution of ice centres is argued to have been influenced by tectonic topography created by large mantle plumes and by rift shoulder uplift. Paleomagnetic data indicative of tropical glaciation are, in our view, ambiguous because of uncertainty as to when such paleomagnetic characteristics were acquired. A lower solar luminosity may have played a role in lowering snow line elevations and displacing glaciation into latitudes lower than those of Phanerozoic glaciations. Global tectonic and volcanic activity, especially the rapid burial or organic carbon in new rift basins, may explain extreme shifts in C-isotopic values evident in late Neoproterozoic strata.

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This digital document is a journal article from Remote Sensing of Environment, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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During the rainy season the abundance of mosquitoes over the Ferlo region (Senegal) is linked to dynamic, vegetation cover and turbidity of temporary and relatively small ponds. The latter create a variable environment where mosquitoes can thrive and thus contribute to diffusion and transmission of diseases such as the Rift Valley Fever (RVF, with Aedes vexans arabiensis and Culex poicilipes mosquitoes) in the Ferlo. The small size and complex distribution of ponds require the use of high-spatial resolution satellite images for adequate detection. Here the use of SPOT-5 images (10 m-resolution) allows for detailed assessment of spatio-temporal evolution of ponds, through two new indices: i.e., the Normalized Difference Pond Index (NDPI), and the Normalized Difference Turbidity Index (NDTI). Small ponds less than 0.5 ha dominate whatever the time period. For example they represent nearly 65% of the total ponds during the peak of the rainy season, up to 90% at the end of the same season. Moreover, another product is proposed: the Zone Potentially Occupied by Mosquitoes (ZPOM). During the apex of the summer monsoon, it is found that RVF mosquitoes occupy 25% of the Ferlo region, while only 0.9% of the same area is covered by ponds. Overlapping areas occupied by grazing cattle and mosquitoes, enhance RVF virus transmission. The remotely sensed operational indices and products presented here are meant to better understand the mechanisms at stake and to contribute to the development of early warning systems in a changing climate and environment.

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This digital document is a journal article from Palaeogeography, Palaeoclimatology, Palaeoecology, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The shallow marine, early, syn-rift, Miocene, Nukhul Formation, Suez Rift, Egypt, is highly bioturbated and allows relationships between changes in trace fossils and ichnofabrics within a shallow marine depositional system to be documented and placed in a high resolution sequence stratigraphic framework. Seven ichnofabrics are present in a succession of interfingering, calcareous mudstones and calcarenites forming coarsening-up units of up to 30 m thick, bounded by marine flooding surfaces. The units grade upwards from a basal mudstone package with bed parallel concretions and a Planolites-Chondrites ichnofabric (offshore), through a coarsening-up succession of alternating calcarenites and mudstones with Thalassinoides-mottled sediment (offshore transition), Ophiomorpha irregulaire (lower shoreface), Ophiomorpha nodosa-Thalassinoides (lower middle shoreface), Thalassinoides-Taenidium (middle shoreface) and O. nodosa (upper shoreface) ichnofabrics. Gastrochaenolites (hardground) ichnofabric is separate, as it is not genetically related to the other ichnofabrics. Ichnofabric development is primarily controlled by depositional environment, e.g. bottom water oxygenation, sediment type, food abundance and energy level, which control substrate colonisation, sedimentation rate. Marine flooding surfaces are generally well-cemented and marked by distinctive epifaunal and infaunal colonisation and can be traced out from proximal to distal settings over distances of >5 km. The epifaunal colonisation in proximal settings consists of abundant oysters and corals with the substrate below marine flooding surfaces containing abundant Thalassinoides and Ophiomorpha isp. Abundance and diversity of epifauna and trace fossils and burrow size decreases distally into the basin. In the most distal settings, epifaunal colonisation is absent and only Planolites and Chondrites colonise the basinal mudstone. Marine flooding surfaces in the most distal settings are poorly cemented, but are marked by carbonate concretions 10-15 cm below the surface.

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This digital document is an article from World Literature Today, published by University of Oklahoma on June 22, 1994. The length of the article is 584 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

Citation Details
Title: The Rift.
Author: Kenneth Harrow
Publication: World Literature Today (Refereed)
Date: June 22, 1994
Publisher: University of Oklahoma
Volume: v68 Issue: n3 Page: p626(1)

Article Type: Book Review

Distributed by Thomson Gale

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This digital document is a journal article from Journal of Arid Environments, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The Rift Valley has diverse soil types with different fertility potential. The climate of the Rift Valley is also diverse. Five major soil types that lie in the humid, sub-humid, and semi-arid parts of the Rift Valley were studied. Total sulfur (S) in the subsoil of the Solonetz and Andosol approximates total S contents of similar soils in other parts of the world. Organic matter is the major source of total sulfur for the soils in the humid parts (Nitisol, Andosol and Vertisol), whereas gypsum is the major source for the soils in the drier parts (Fluvisol and Solonetz). The Nitisol has the lowest soluble sulfate, which is below the critical level for crop production. All other soils contain soluble sulfate which is adequate for crop production. Land degradation, crop residue removal, clearing and burning of forests and other vegetation, crop uptake, and use of non-S fertilizers are major causes of sulfur deficiency in the Rift Valley. Maintenance of the soil organic matter, utilization of subsurface inorganic S and proper management of soils should maintain the S status of the soils in the future.
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