Climatic control of fluvial-lacustrine cyclicity in the Cretaceous Cordilleran Foreland Basin, western United States

Tectono-stratigraphic models of foredeep sedimentation have generally presumed a direct link between changing rates of tectonism and concomitant sedimentological response as manifested by change in thickness, composition or depositional environment of sediment accumulating in adjacent basins. Lacustrine limestone units within the early Cretaceous fluvial/lacustrine Gannett Group of western Wyoming exhibit systematic variation in several geochemical proxies of relative rates of precipitation and evaporation, indicating that lakewater chemistry was controlled by variation in regional climate. Change in proportion of allochthonous terrigenous clastic vs. autochthonous carbonate deposition, as well as carbonate Mg/Ca ratio and stable isotopic composition, occurs at two scales. Metre-scale alternation of micritic limestone and argillaceous marl is accompanied by mineralogical and isotopic variation within individual beds, indicating preferential carbonate accumulation during intervals of decreased regional meteoric precipitation relative to lake-surface evaporation. Limestone deposition began during intervals of maximum aridity, and decreased as increased meteoric precipitation-driven flux of terrigenous clastic sediment overwhelmed sites of carbonate accumulation. Similar upsection variation in limestone mineralogy and isotopic composition at a scale of tens of metres reflects the multiple processes of long-term increase in meteoric precipitation and lakewater freshening prior to influx of terrigenous sediment, across-basin fluvial-deltaic progradation, and renewed accumulation of riverine terrigenous units. Such trends suggest that formation-scale alternation between fluvial clastic and lacustrine carbonate deposition was controlled by climate change.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75290/1/j.1365-3091.1996.tb02020.x.pd

Mass treatment for intestinal helminthisis control in an Amazonian endemic area in Brazil Tratamento em massa para controle das helmintíases intestinais em área endêmica na Amazônia Brasileira

The objective of the present study was to estimate the prevalence of soil-transmitted helminthiasis and evaluate the sanitary conditions and the role of a mass treatment campaign for control of these infections in Santa Isabel do Rio Negro. A cross-sectional survey was carried out in 2002, to obtain data related to the sanitary conditions of the population and fecal samples for parasitological examination in 308 individuals, followed by a mass treatment with albendazole or mebendazole with coverage of 83% of the city population in 2003. A new survey was carried out in 2004, involving 214 individuals, for comparison of the prevalences of intestinal parasitosis before and after the mass treatment. The prevalences of ascariasis, trichuriasis and hookworm infection were 48%; 27% and 21% respectively in 2002. There was a significant decrease for the frequency of infections by Ascaris lumbricoides (p < 0.05; OR / 95% CI = 0.44 / 0.30 - 0.65), Trichuris trichiura (p < 0.05; OR / 95% CI = 0.37 / 0.22 - 0.62), hookworm (p < 0.05; OR / 95% CI = 0.03 / 0.01 - 0.15) and helminth poliparasitism (p < 0.05; OR / 95% CI = 0.16 / 0.08 - 0.32). It was also noticed a decrease of prevalence of infection by Entamoeba histolytica / dispar (p < 0.05; OR / 95% CI = 0.30 / 0.19 - 0.49) and non-pathogenic amoebas. It was inferred that a mass treatment can contribute to the control of soil-transmitted helminthiasis as a practicable short-dated measure. However, governmental plans for public health, education and urban infrastructure are essential for the sustained reduction of prevalences of those infections.<br>O presente trabalho objetivou avaliar a prevalência e o papel de um tratamento em massa das helmintíases intestinais em Santa Isabel do Rio Negro, Estado do Amazonas, Brasil. Foi realizado em 2002 um estudo seccional, incluindo inquérito copro-parasitológico, objetivando a obtenção das prevalências das parasitoses intestinais e dados sobre as condições sanitárias do local, estudando-se uma amostra de 308 indivíduos. Em 2003 foi realizada intervenção para tratamento em massa das helmintíases intestinais com administração de albendazol (ou mebendazol para crianças entre 12 e 24 meses) na sede do município, alcançando-se 83% de cobertura. Novo inquérito copro-parasitológico foi realizado em 2004, para comparação das prevalências antes a após o tratamento. As prevalências das infecções por Ascaris lumbricoides, Trichuris trichiura e ancilostomídeos foram 48%, 27% e 21%, respectivamente em 2002. Em 2004 observou-se redução significativa das infecções por Ascaris lumbricoides (p < 0,05; OR / 95% IC = 0,44 / 0,30 - 0,65), Trichuris trichiura (p < 0,05; OR / 95% IC = 0,37 / 0,22 - 0,62), ancilostomídeos (p < 0,05; OR / 95% IC = 0,03 / 0,01 - 0,15) e poliparasitismo por helmintos intestinais (p < 0,05; OR / 95% IC = 0,16 / 0,08 - 0,32). Foi também observada redução da prevalência de infecção por Entamoeba histolytica/dispar (p < 0,05; OR / 95% CI = 0,30 / 0,19 - 0,49). Concluiu-se que o tratamento em massa pode auxiliar o controle das helmintíases intestinais, porém ações governamentais em infraestrutura urbana e educação são essenciais para uma redução sustentada das prevalências destas infecções