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Stewart, A.G.; Carter, J.; Parker, A.; Alloway, B.J.
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The distribution of endemic goitre in England and Wales was compared with the distribution of environmental iodine (atmospheric deposition, soil, surface water). Despite a very clear goitre belt through the west of England and Wales there was no patterning in the environmental iodine distribution. A clear seasonal variation in depositional iodine exists, with an unusually high concentration of iodine in March 1997. The temporal variation in iodine concentration is determined at the monthly and not the annual level. The presence of endemic goitre is no indicator of how iodine is distributed in the environment or vice versa!
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Tarasov, P.; Granoszewski, W.; Bezrukova, E.; Brewer, S.; Nita, M.; Abzaeva, A.; Oberhänsli, H.
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Changes in mean temperature of the coldest (Tc) and warmest month (Tw), annual precipitation (Pann) and moisture index (α) were reconstructed from a continuous pollen record from Lake Baikal, Russia. The pollen sequence CON01-603-2 (53°57′N, 108°54′E) was recovered from a 386 m water depth in the Continent Ridge and dated to ca. 130–114.8 ky BP. This time interval covers the complete last interglacial (LI), corresponding to MIS 5e. Results of pollen analysis and pollen-based quantitative biome reconstruction show pronounced changes in the regional vegetation throughout the record. Shrubby tundra covered the area at the beginning of MIS 5e (ca. 130–128 ky), consistent with the end of the Middle Pleistocene glaciation. The late glacial climate was characterised by low winter and summer temperatures (Tc ~ −38 to −35°C and Tw~11–13°C) and low annual precipitation (Pann~300 mm). However, the wide spread of tundra vegetation suggests rather moist environments associated with low temperatures and evaporation (reconstructed α~1). Tundra was replaced by boreal conifer forest (taiga) by ca. 128 ky BP, suggesting a transition to the interglacial. Taiga-dominant phase lasted until ca. 117.4 ky BP, e.g. about 10 ky. The most favourable climate conditions occurred during the first half of the LI. Pann reached 500 mm soon after 128 ky BP. However, temperature changed more gradually. Maximum values of Tc ~ −20°C and Tw~16–17°C are reconstructed from about 126 ky BP. Conditions became gradually colder after ca. 121 ky BP. Tc dropped to ~ −27°C and Tw to ~15°C by 119.5 ky BP. The reconstructed increase in continentality was accompanied by a decrease in Pann to ~400–420 mm. However, the climate was still humid enough (α~0.9) to support growth of boreal evergreen conifers. A sharp turn towards a dry climate is reconstructed after ca. 118 ky BP, causing retreat of forest and spread of cool grass-shrub communities. Cool steppe dominated the vegetation in the area between ca. 117.5 ky and 114.8 ky BP, suggesting the end of the interglacial and transition to the last glacial (MIS 5d). Shift to the new glaciation was characterised by cool and very dry conditions with Tc ~ −28 to −30°C, Tw~14–15°C, Pann~250 mm and α~0.5.
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Morey, Anthony A.; Weinberg, Roberto F.; Bierlein, Frank P.
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The Bardoc Tectonic Zone (BTZ) of the late Archaean Eastern Goldfields Province, Yilgarn Craton, Western Australia, is physically linked along strike to the Boulder-Lefroy Shear Zone (BLSZ), one of the richest orogenic gold shear systems in the world. However, gold production in the BTZ has only been one order of magnitude smaller than that of the BLSZ (∼100 t Au vs >1,500 t Au). The reasons for this difference can be found in the relative timing, distribution and style(s) of deformation that controlled gold deposition in the two shear systems. Deformation within the BTZ was relatively simple and is associated with tight to iso-clinal folding and reverse to transpressive shear zones over a <12-km-wide area of high straining, where lithological contacts have been rotated towards the plane of maximum shortening. These structures control gold mineralisation and also correspond to the second major shortening phase of the province (D2). In contrast, shearing within the BLSZ is concentrated to narrow shear zones (<2 km wide) cutting through rocks at a range of orientations that underwent more complex dip- and strike-slip deformation, possibly developed throughout the different deformation phases recorded in the region (D1–D4). Independent of other physico-chemical factors, these differences provided for effective fluid localisation to host units with greater competency contrasts during a prolonged mineralisation process in the BLSZ as compared to the more simple structural history of the BTZ.
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Marianelli, Paola; Métrich, Nicole; Sbrana, Alessandro
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During the 1944 eruption of Vesuvius a sudden change occurred in the dynamics of the eruptive events, linked to variations in magma composition. K-phonotephritic magmas were erupted during the effusive phase and the first lava fountain, whereas the emission of strongly porphyritic K-tephrites took place during the more intense fountain. Melt inclusion compositions (major and volatile elements) highlight that the magmas feeding the eruption underwent differentiation at different pressures. The K-tephritic volatile-rich melts (up to 3 wt.% H2O, 3000 ppm CO2, and 0.55 wt.% Cl) evolved to reach K-phonotephritic compositions by crystallization of diopside and forsteritic olivine at total fluid pressure higher than 300 MPa. These magmas fed a very shallow reservoir. The low-pressure differentiation of the volatile-poor K-phonotephritic magmas (H2O<1 wt.%) involved mixing, open-system degassing, and crystallization of leucite, salite, and plagioclase. The eruption was triggered by intrusion of a volatile-rich magma batch that rose from a depth of 11–22 km into the shallow magma chamber. The first phase of the eruption represents the partial emptying of the shallow reservoir, the top of which is within the volcanic edifice. The newly arrived magma mixed with that resident in the shallow reservoir and forced the transition from the effusive to the lava fountain phase of the eruption.
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Davison, Leslie; Fookes, Peter; Baynes, Fred
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The concern is with the effective use of computers to assist site investigation where subsurface conditions must be predicted. It deals with qualitative rather than quantitative aspects of investigation, utilising the numerous case histories which suggest that failure to anticipate leads to failure to observe and understand. Following (2000) it is argued that the geological model is the key to predicting subsurface conditions.
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Wendt, Chris K.; Beringer, Jason; Tapper, Nigel J.; Hutley, Lindsay B.
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Fire scars have the ability to radically alter the surface energy budget within a tropical savanna by reducing surface albedo, increasing available energy for partitioning into sensible and latent heat fluxes and increasing substrate heat flux. These changes have the potential to alter boundary-layer conditions and ultimately feedback to local and regional climate. We measured radiative and energy fluxes over burnt and unburnt tropical savanna near Howard Springs, Darwin, Australia. At the burnt site a low to moderate intensity fire, ranging between 1,000 and 3,500 kW m−1, initially affected the land surface by removing all understorey vegetation, charring and blackening the ground surface, scorching the overstorey canopy and reducing the albedo. A reduction in latent heat fluxes to almost zero was seen immediately after the fire when the canopy was scorched. This was then followed by an increase in the sensible heat flux and a large increase in the ground heat flux over the burnt surface. Tethered balloon measurements showed that, despite the presence of pre-monsoonal rain events occurring during the measurement period, the lower boundary layer over the burnt site was up to 2°C warmer than that over the unburnt site. This increase in boundary-layer heating when applied to fire scars at the landscape scale can have the ability to form or alter local mesoscale circulations and ultimately create a feedback to regional heating and precipitation patterns that may affect larger-scale processes such as the Australian monsoon.
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Schuster, Robert L.; Highland, Lynn M.
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As a result of population pressures, hillsides in the world’s urban areas are being developed at an accelerating rate. This development increases the risk for urban landslides triggered by rainfall or earthquake activity. To counter this risk, four approaches have been employed by landslide managers and urban planners: (1) restricting development in landslide-prone areas; (2) implementing and enforcing excavation, grading, and construction codes; (3) protecting existing developments by physical mitigation measures and (4) developing and installing monitoring and warning systems. Where they have been utilized, these approaches generally have been effective in reducing the risk due to landslide hazards. In addition to these practices, landslide insurance holds promise as a mitigative measure by reducing the financial impact of landslides on individual property owners. Until recently, however, such insurance has not been widely available and, where it is available, it is so expensive that it has been little used.
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Yao, Wensheng; Millero, Frank J.
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In the summer of 1993, a number of chemical parameters (H2S, O2, pH, TA, TCO2, NH
4+
, PO
43−
, SiO2, Mn2+ and Fe2+) were measured in the Framvaren Fjord, a permanently super-anoxic fjord in southern Norway. The extremely steep gradient of sulfide near the interface suggests that other than downward flux of oxygen, three other possible oxidants, particulate manganese and iron oxides, phototrophic sulfur oxidation bacteria and horizontally transported oxygen account for the oxidation of the upward flux of H2S. Water intrusion through the sill accounts for the temperature inflection above the interface, which, together with internal waves (Stigerbrandt and Molvaer, 1988), may cause fluctuations of the depth of interface. Significant gradients of hydrographic properties and chemical species between 80–100 m suggest that there is a “second interface” at about 90 m that separates the deep and older bottom waters. A stoichiometric model is applied to examine the biogeochemical cycles of S, C, N and P in the Framvaren. High C:S, C:N and C:P ratios are found while the nutrients (N, P) have Redfield ratio. Based on the C:N:P ratio of 155:16:1 in organic matter, about 30% of sulfide produced by sulfate reduction is estimated to be removed by processes such as oxidation, formation of FeS2, degassing and incorporation into organic matter. The rates of oxidation of H2S by Mn and Fe oxides in the water near the interface were slightly faster than the observed values in the laboratory, probably due to the presence of bacteria.
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