Rotation history of Alaskan tectonic blocks

Alaska is considered to be tectonically comprised of five elongate blocks separated by transcurrent faults formed prior to rotation which enter the state from the southeast and continue westward to the edge of the Bering Sea continental shelf. We propose an additional, inactive fault, indicated by gravity and magnetic data and other observations, to extend between the Bering Strait and the Arctic Ocean continental shelf east of the Northwind escarpment, separating northern Alaska from northeast Siberia. Near the center of the state the faults are bent, concave to the south, about the north-south axis of the so-called Alaska orocline. In our reconstruction the blocks have rotated from a position whereby the north slope was adjacent to Banks Island of the Canadian basin. During the rotation the northernmost, or Brooks block, was squeezed, up to 15% in the western end, to its present width. After rotation, when the three southern blocks were in their present position, the Brooks block and the next block to the south were pushed eastward by North America moving against Siberia, forming the bend in the British-Richardson-Ogilvie Mountains we call the Ogilvie orocline.     

Environmental magnetic indicators of the sedimentary context of archaeological sites in the Shangqiu area of China

Environmental magnetic techniques provide significant potential for characterizing sediments and soils and inferring their sources. This article discusses the application of environmental magnetic techniques in the study of an evolving landscape in the Shangqiu area, China, an archaeologically important region for investigating the origin of Shang civilization. Two magnetic parameters—anhysteretic remanent magnetization (ARM) and low-field magnetic susceptibility (χ)—are employed to discriminate the pre-Neolithic paleosol from the historic alluvium. In order to quantitatively interpret magnetic measurements, ARM versus χ plots are utilized with rigorous statistical analyses including group comparison and discriminant classification. With the ARM/χ classification model defined by the pre-Neolithic paleosol and historic alluvium, the sediment sources of three anthropogenic deposits (A-1, A-2, and A-3 from oldest to youngest) are addressed. Magnetic data clearly show that A-1 and A-3 are closely associated with the pre-Neolithic paleosol and historic alluvium, respectively. Cultural mixing processes might be partially responsible for the formation of A-2. © 1998 John Wiley & Sons, Inc.     

Variational stabilization of the ionic charge densities in the electron-gas theory of crystals: Applications to MgO and CaO

The electron-gas theory of crystals is extended to include the effects of many-body forces that arise from both electrostatic and overlap interactions. These effects are incorporated through a self-consistent spherical relaxation of the ionic charge distributions such that the crystal binding energy is minimized. This variational model is used to compute the elastic constants and equations of state of MgO and CaO, and we compare its results to those derived from earlier electron-gas models. In the variational model, the anion charge distributions are markedly more sensitive to the local crystal environment than they are in the PIB or other electron-gas models. We find that for these oxides the variational model gives the best overall agreement with experiment for lattice constants, equations of state, dissociation energies, and elastic moduli.     

Silver and copper accumulation in two estuarine bivalves,the eastern oyster (Crassostrea virginica) and the hooked mussel (Ischadium recurvum) in the Patuxent River estuary,Maryland

In order to assess the source of trace elements and to compare uptake between different bivalve species, oysters and mussels were transplanted to five sites in the upper Patuxent River estuary during 1988. Transplant sites were located above and below the discharge of Chalk Point Steam Electric Station (CPSES)—a historic point source for copper. Organisms were sampled approximately monthly for 1 yr and analyzed for copper and silver. During spring and summer, concentrations of silver and copper increased in oysters at the upstream stations. There was very little change in silver and copper concentrations in the mussels with either time or among stations. Copper concentrations accumulated by oysters approached those found during previous periods when CPSES used Cu?Ni alloy condenser tubes (1966–1987), suggesting that corrosion from the Cu?Ni condenser tubes was only a minor contributor to the copper burdens of oysters in the river nearby. The lack of accumulation by mussels at the same sites suggests that part of the reason for the accumulation by oysters may be a taxonomically specific physiological effect caused by the salinity regime in the upper Patuxent.     

Lake Koronia, Greece: Shift from autotrophy to heterotrophy with cultural eutrophication and progressive water-level reduction

Lake Koronia, a Ramsar site, is shallow, polymictic, hypertrophic and until recently was aerially the fourth largest lake in Greece. Although exceeding 5 m in the past, lake depth has declined progressively from 3.8 m in 1980 to < 1 m in 1997, reducing surface area and water volume by 50% and 80%, respectively. Specific conductivityincreased from 1300 μS cm⁻¹ in 1977 to >6000 μS cm⁻¹ in 1991. Increased phosphate concentrations from the late 1970's (8–45 μg L⁻¹) to the late 1990's (100–1000 μg L⁻¹) document that the previously eutrophic system with a limited littoral zone switched to hypertrophy dominated by massive cyanobacteria blooms. Oxygen saturation of the water column increased progressively from about 80% in 1983 to full saturation about 1993, after which it decreased progressively to only 20% saturation in 1997. In spite of cyanobacteria dominance, community metabolism of the lake switched from progressively increasing autotrophy to rapidly advancing heterotrophy associated with progressive water-level reduction leading to fish extirpation in the lake.     

Preliminary Interlaboratory Trial for ISO/DIS 12010: Determination of Short Chain Polychlorinated Alkanes (SCCP) in Water

A first preliminary interlaboratory trial was planned to prepare ISO/DIS 12010: Water quality – determination of short chain polychlorinated alkanes (SCCP) in water – method using GC/MS and electron capture negative ionisation (ECNI). The task was to determine the sum of short chain polychlorinated n‐alkanes with carbon chain lengths of C₁₀–C₁₃ and a chlorine content between 49 and 67% in water by GC‐ECNI‐MS and quantification by multiple linear regression described in ISO/DIS 12010 as the compulsory method. Distributed samples were obtained from a real water extract spiked with a target concentration of 0.4 µg/mL sum of SCCP, i.e. the environmental quality target level according to the Water Framework Directive. The interlaboratory trial included the calibration, a column chromatographic clean up, a concentration step and an integration of chromatographic unresolved humps as well as the quantification with multiple linear regression. Reproducibility standard deviations between 21.5 and 22.9% were achieved by 17 participating laboratories from four countries. The method outlined no significant difference of the results between the standard solution and a real water matrix extract. On the basis of this succeeded preliminary interlaboratory trial the final interlaboratory trial for validation of ISO 12010 was prepared in autumn 2010.     

Coastal habitat degradation and green sea turtle diets in Southeastern Brazil

To show the influence of coastal habitat degradation on the availability of food for green turtles (Chelonia mydas), we assessed the dietary preferences and macroalgae community at a feeding area in a highly urbanized region. The area showed low species richness and was classified as degraded. We examined stomach contents of 15 dead stranded turtles (CCL = 44.0 cm (SD 6.7 cm)). The diet was composed primarily of green algae Ulva spp. (83.6%). In contrast, the macroalgae community was dominated by the green alga Caulerpa mexicana. We found a selection for red algae, seagrass and Ulva spp., and avoidance for C. mexicana and brown alga Dictyopteris delicatula. The low diversity of available food items, possibly a result of environmental degradation, likely contributed to the low dietary diversity. The nutritional implications of this restricted diet are unclear.