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Temporal and spatial sources of silica for chert remain poorly constrained. Modern sources to the worlds oceans include silica in rivers > aeolian (dust) deposition > sea floor vents and submarine weathering. However, changes in aridity and dust flux during the Phanerozoic may explain variations in the ocean silica cycle and times and places of chert formation. The chemistry of fine quartz dust (FQD) provides a chemical mechanism for the transformation of FQD to polymorphs of silica in chert; FQD is readily dissolved, then reprecipitated as Opal-A by either biotic or abiotic processes. An unequivocal relation between increases in dust flux and biogenic opal-A in the western Pacific Ocean during the past 200 kyr...
Extensive nucleotide changes and deletions within the envelope glycoprotein gene of Euro-African West Nile viruses
Forests and food security in Africa: the place of forestry in FAO's Special Programme for Food Security
Central-place analysis and modeling of landscape-scale resource use in an East African agropastoral system
Survival, longevity and fecundity of overwintering Mesoplatys ochroptera Staal (Coleoptera: Chrysomelidae) defoliating Sesbania sesban (Leguminosae) and implications for its management in southern Africa
Regional marine environmental management and the GPA-LBA: perspectives and the need for scientific support
Advances and review of strategies for red locust plague prevention: The control of red locust, Nomadacris septemfasciata (Serville) into the 21st century