Late Quaternary climate change record from two long sediment cores from Guaymas Basin,Gulf of California

Modern Guaymas Basin (Gulf of California, Mexico) is a region of high diatom productivity where exceptional preservation factors maintain biannually alternating sediment deposition as annual varves. New sediment cores from Guaymas Basin (MD02‐2512 and MD02‐2515) present the opportunity to construct climate records from below the last glacial period. A low‐resolution age model has been constructed from oxygen isotope analysis, correlation with other dated short piston cores from Guaymas Basin and an estimate of sedimentation rate. MD02‐2512 from eastern Guaymas Basin has an age range from the Holocene to late marine isotope stage 6 (MIS 6); MD02‐2515 from western Guaymas Basin has an age range from ～8000 to 40 000 yr. Shipboard analyses of colour reflectance, magnetic susceptibility and sediment density are combined with continuous X‐ray fluorescence scans to reconstruct a picture of glacial climate in the Gulf of California. Eastern Guaymas Basin is affected by glacial sea level fall, which results in a drastic change in productivity rates and sediment type. The laminated record of MIS 5 allows comparison with the Holocene, showing a similarity of sedimentation patterns during deglaciation and a series of very rapid variations just prior to the last glaciation. In western Guaymas Basin there are a series of Younger Dryas‐like events during the glacial, typified by low productivity and high terrigenous input. Long‐term climate and productivity changes appear to be caused by the southward displacement of the Subtropical High pressure zone. Copyright © 2005 John Wiley & Sons, Ltd.     

The possible hydrologic effects of the proposed lignite open‐cast mining in Drama lignite field,Greece

The present study investigates the possible hydrologic effects of the proposed lignite open‐cast mining in Drama lignite field (north Greece). Recent years have seen a rapid increase in surface mining. This activity has generated a growing concern for the potential environmental impacts associated with large scale surface mining. In order to achieve a safe mine operation and allow extraction of lignite to considerable depths, extensive dewatering by pumping will be necessary, while at the same time it is desirable to avoid presence of overpumping conditions in the broader area. Based on stratigrafic, hydrologic and hydrogeologic data, a three‐dimensional finite difference model was developed in order to simulate the dewatering process of the western part of the lignite open‐cast mine in Drama and to predict both spatially and temporally the decline of ground water level down to the lignite surface. The dewatering of the part of the aquifer which underlies the mine area will influence the hydrological conditions of the broader region. The most important anticipated effects will be the abandonment of shallow wells as well as the decrease of ground water pumping rates of deep wells. Aquifer discharge towards the ditches of the study area will cease and there will be an inversion of ground water flow from the ditches towards the underlying aquifer. Dewatering activities will probably result in minor subsidence of the nearby peat deposits of Drama Philippi marshes. Moreover, sand pumping as well as the presence of gasses is likely to cause local subsidence phenomena, mainly in the pit slopes. Copyright © 2007 John Wiley & Sons, Ltd.     

Enthalpy of formation of sulfate green rusts

As a contribution to the systematic study of iron oxide thermodynamics, this work reports enthalpies of formation of green rust, a double layered (Fe^II, Fe^III) hydroxide with the ideal stoichiometry , with sulfate as the anion in the interlayer. Samples were characterized by X-ray powder diffraction, thermogravimetric analysis, infrared spectroscopy, and Mössbauer spectroscopy. Full chemical analysis was performed. Contents of Fe^II, Fe^III, water, and sulfate were obtained. We report standard enthalpies of formation for green rust with different Fe^II/Fe^III ratios. Enthalpies of formation from single cation compounds, namely, Fe(OH)₂, Fe(OH)₃, FeSO₄ and H₂O show reasonable agreement with Gibbs free energies of formation from single cation compounds recalculated from the reported literature values. These values show that green rust has little stabilization over a mechanical mixture of these single cation compounds and there is no thermodynamic preference for any particular Fe^II/Fe^III ratio.     

Predicting monthly precipitation along coastal Ecuador: ENSO and transfer function models

Theoretical and Applied Climatology - It is well known that El Niño-Southern Oscillation (ENSO) modifies precipitation patterns in several parts of the world. One of the most impacted areas is...     

Nanogeochemistry of hydrothermal magnetite

Magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million (ppm) of elements such as Ti, Si, V, Al, Ca, Mg, Na, which tend to either structurally incorporate into growth and sector zones or form mineral micro- to nano-sized particles. Here, we report micro- to nano-structural and chemical data of hydrothermal magnetite from the Los Colorados iron oxide–apatite deposit in Chile, where magnetite displays both types of trace element incorporation. Three generations of magnetites (X–Z) were identified with concentrations of minor and trace elements that vary significantly: SiO₂, from below detection limit (bdl) to 3.1 wt%; Al₂O₃, 0.3–2.3 wt%; CaO, bdl–0.9 wt%; MgO, 0.02–2.5 wt%; TiO₂, 0.1–0.4 wt%; MnO, 0.04–0.2 wt%; Na₂O, bdl–0.4 wt%; and K₂O, bdl–0.4 wt%. An exception is V₂O₃, which is remarkably constant, ranging from 0.3 to 0.4 wt%. Six types of crystalline nanoparticles (NPs) were identified by means of transmission electron microscopy in the trace element-rich zones, which are each a few micrometres wide: (1) diopside, (2) clinoenstatite; (3) amphibole, (4) mica, (5) ulvöspinel, and (6) Ti-rich magnetite. In addition, Al-rich nanodomains, which contain 2–3 wt% of Al, occur within a single crystal of magnetite. The accumulation of NPs in the trace element-rich zones suggest that they form owing to supersaturation from a hydrothermal fluid, followed by entrapment during continuous growth of the magnetite surface. It is also concluded that mineral NPs promote exsolution of new phases from the mineral host, otherwise preserved as structurally bound trace elements. The presence of abundant mineral NPs in magnetite points to a complex incorporation of trace elements during growth, and provides a cautionary note on the interpretation of micron-scale chemical data of magnetite.     

The psychology of beach users: importance of confirmation bias,action, and intention to improving rip current safety

Natural Hazards - The rip current hazard on beaches is a global public health issue. While physical controls on rip current formation and flow behavior are relatively well understood, there has...     

Accurate Ocean Bottom Seismometer Positioning Method Inspired by Multilateration Technique

The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data.     

The use of bioluminescent dinoflagellates as an environmental risk assessment tool

A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the bioluminescence output from marine dinoflagellates has been developed and tested over the course of 16 years. The toxicity system, QwikLite™, was developed for the sole purpose of evaluating the potential toxicity of various materials used in bay sediments, storm water discharges, industrial discharges from Naval facilities, and antifoulant paints. Bioluminescence inhibition was observed in the following dinoflagellates: Lingulodinium polyedrum (formerly known as Gonyaulax polyedra), Ceratocorys horrida, Pyrocystis noctiluca, Pyrocystis lunula, Pyrocystis fusiformis, and Pyrophacus steinii. Cultured cells were exposed to various concentrations of contaminants from hours through 10 days. Further application with bioluminescent dinoflagellates in a variety of toxicity testing schemes have shown that these species can be used as a screening assay organism in lieu of the more costly, labor intensive bioassays presently in use.