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Selected AbstractsSpatial and temporal evaluation of metal concentrations in soils and sediments from new orleans, louisiana, USA, following hurricanes Katrina and RitaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2007Michael T. Abel Abstract During January 2006, soil and sediment samples from 75 sites in the New Orleans (LA, USA) area were collected and tested for 26 inorganic elements. The study design was intended to provide a spatial pattern of metal concentrations within the city following hurricanes Katrina and Rita. The sampling design included four transects that traversed the city in a north,south direction and three transects that traversed the city in an east,west direction. Contaminant concentrations were determined at multiple sites within each transect and compared to U.S. Environmental Protection Agency soil screening criteria pertaining to human health. Concentrations of Pb and As exceeded the criteria indiscriminately throughout the city. Of the 75 sites, 14 (19%) exceeded the soil screening criteria for Pb, and 73 (97%) exceeded the criteria for As. Forty-three of the 75 sites coincided with a previous sampling event in October 2005. Metal concentrations were evaluated for temporal comparisons using a pair sampled t test. Arsenic concentrations differed significantly over time, but Pb concentrations did not. [source] Geophysical investigation of the site of the former monastic settlement, Clonard, County Meath, IrelandARCHAEOLOGICAL PROSPECTION, Issue 1 2006Paul J. Gibson Abstract Clonard, in County Meath, Ireland was a major ecclesiastical centre from the early sixth century to the twelfth century and buildings associated with the monastery were in existence until the late eighteenth century. However, today no extant buildings or features associated with the monastery are known. The geophysical investigation undertaken in this project has uncovered many anomalies which may be related to the monastic settlement at Clonard. A significant number of linear anomalies have been detected east of St Finian's church using magnetic gradiometry and twin electrode resistance surveying. Many of these anomalies are probably field boundaries; however, a much greater diversity of geophysical responses is located south and west of St Finian's church. A subsquare enclosure of 60,m sides is adjacent to a 300,m long palaeochannel. A fine network of intersecting low resistance anomalies probably represent former artificial drainage channels. Three large areas associated with anomalous magnetic readings were located which might indicate sites of human activity. In addition, there are four distinct zones which have large concentrations of high resistance values suggesting the presence of walls or buildings. Resistivity and ground-penetrating radar depth slices show that one of these zones has characteristics which indicate the presence of an east,west aligned building approximately 7,m wide in a north,south direction and about 15,m long in an east,west direction. Copyright © 2005 John Wiley & Sons, Ltd. [source] Linkage of Sevier thrusting episodes and Late Cretaceous foreland basin megasequences across southern Wyoming (USA)BASIN RESEARCH, Issue 4 2005Shao-Feng Liu ABSTRACT Deposition and subsidence analysis, coupled with previous structural studies of the Sevier thrust belt, provide a means of reconstructing the detailed kinematic history of depositional response to episodic thrusting in the Cordilleran foreland basin of southern Wyoming, western interior USA. The Upper Cretaceous basin fill is divided into five megasequences bounded by unconformities. The Sevier thrust belt in northern Utah and southwestern Wyoming deformed in an eastward progression of episodic thrusting. Three major episodes of displacement on the Willard-Meade, Crawford and ,early' Absaroka thrusts occurred from Aptian to early Campanian, and the thrust wedge gradually became supercritically tapered. The Frontier Formation conglomerate, Echo Canyon and Weber Canyon Conglomerates and Little Muddy Creek Conglomerate were deposited in response to these major thrusting events. Corresponding to these proximal conglomerates within the thrust belt, Megasequences 1, 2 and 3 were developed in the distal foreland of southern Wyoming. Two-dimensional (2-D) subsidence analyses show that the basin was divided into foredeep, forebulge and backbulge depozones. Foredeep subsidence in Megasequences 1, 2 and 3, resulting from Willard-Meade, Crawford and ,early' Absaroka thrust loading, were confined to a narrow zone in the western part of the basin. Subsidence in the broad region east of the forebulge was dominantly controlled by sediment loading and inferred dynamic subsidence. Individual subsidence curves are characterized by three stages from rapid to slow. Controlled by relationships between accommodation and sediment supply, the basin was filled with retrogradational shales during periods of rapid subsidence, followed by progradational coarse clastic wedges during periods of slow subsidence. During middle Campanian time (ca. 78.5,73.4 Ma), the thrust wedge was stalled because of wedge-top erosion and became subcritical, and the foredeep zone eroded and rebounded because of isostasy. The eroded sediments were transported far from the thrust belt, and constitute Megasequence 4 that was mostly composed of fluvial and coastal plain depositional systems. Subsidence rates were very slow, because of post-thrusting rebound, and the resulting 2-D subsidence was lenticular in an east,west direction. During late Campanian to early Maastrichtian time, widespread deposits of coarse sediment (the Hams Fork Conglomerate) aggraded the top of the thrust wedge after it stalled, prior to initiation of ,late' Absaroka thrusting. Meanwhile Megasequence 5 was deposited in the Wyoming foreland under the influence of both the intraforeland Wind River basement uplift and the Sevier thrust belt. [source] Distance Decay of Tree Species Similarity in Protected Areas on Terra Firme Forests in Colombian AmazoniaBIOTROPICA, Issue 5 2009Álvaro Duque ABSTRACT In this study, we investigated the pattern of floristic similarity as a function of geographical distances and environmental variability in well-drained uplands (terra firme) in Colombian Amazonia. The study site comprised three National Natural Parks, Tinigua, Chiribiquete, and Amacayacu, located in different geological units that represent a soil fertility gradient linked to parental materials. Differences in species richness between sites were compared using rarefaction analysis. A clear floristic transition appeared in the east,west direction following a soil fertility gradient along the first PCoA axis. In multiple regression analyses based on distance matrices, both geographical distances and geology explained 64 percent of the total floristic variation. Geographical distances alone accounted for 12 percent of variation in floristic similarities among plots, while geology alone accounted for 1 percent, and the joint effect of both explained 51 percent of the floristic variation. The species richness trend supports the existence of a latitudinal corridor southward of the geographical Equator in the Amazon basin, where tree diversity reaches the maximum expected values. A coupled effect of stochastic dispersal limitation and habitat specialization would certainly appear to be an appropriate explanation for tree species turnover in terra firme forests in Colombian Amazonia, strongly emphasizing that competition and neutrality must be supplementary rather than mutually exclusive processes. This result pinpoints the effect of dispersal on floral mixing as an ongoing active process for structuring tree communities in NW Amazonia, and the size of the reserves as a relevant issue to protect rare species from extinction by chance. [source] | |||||||||||||