Late Quaternary sea‐level change and evolution of Belfast Lough,Northern Ireland: new offshore evidence and implications for sea‐level reconstruction

The interplay of eustatic and isostatic factors causes complex relative sea‐level (RSL) histories, particularly in paraglacial settings. In this context the past record of RSL is important in understanding ice‐sheet history, earth rheology and resulting glacio‐isostatic adjustment. Field data to develop sea‐level reconstructions are often limited to shallow depths and uncertainty exists as to the veracity of modelled sea‐level curves. We use seismic stratigraphy, 39 vibrocores and 26 radiocarbon dates to investigate the deglacial history of Belfast Lough, Northern Ireland, and reconstruct past RSL. A typical sequence of till, glacimarine and Holocene sediments is preserved. Two sea‐level lowstands (both max. ?40 m) are recorded at c. 13.5 and 11.5k cal a bp . Each is followed by a rapid transgression and subsequent periods of RSL stability. The first transgression coincides temporally with a late stage of Meltwater Pulse 1a and the RSL stability occurred between c. 13.0 and c. 12.2k cal a bp (Younger Dryas). The second still/slowstand occurred between c. 10.3 and c. 11.5k cal a bp . Our data provide constraints on the direction and timing of RSL change during deglaciation. Application of the Depth of Closure concept adds an error term to sea‐level reconstructions based on seismic stratigraphic reconstructions.     

OIB-type basalts of the Irbistu River basin (Southeast Mountain Altai): Evidence for the HIMU component in the magmatic source

It has been found that basalts of the Irbistu River basin (southeast Altai Mountains) belong to the intraplate OIB type. The peculiarities of their material composition do not indicate interaction effects between the basic melt and continental crust, and signifies that there was a magmatic source in the moderately depleted mantle comparable to the HIMU domain. It is suggested that basalts of the Irbistu River basin, along with other manifestations of similar volcanites in the Altai Mountains, reflect the Neoproterozoic-Early Paleozoic stage of the North Asian plume’s activity during closure of the Paleoasian Ocean.     

Geochemical processes controlling arsenic mobility in groundwater: A case study of arsenic mobilization and natural attenuation

The behavior of As in the subsurface environment was examined along a transect of groundwater monitoring wells at a Superfund site, where enhanced reductive dechlorination (ERD) is being used for the remediation of groundwater contaminated with chlorinated solvents. The transect was installed parallel to the groundwater flow direction through the treatment area. The ERD technology involves the injection of organic C (OC) to stimulate in situ microbial dechlorination processes. A secondary effect of the ERD treatment at this site, however, is the mobilization of As, as well as Fe and Mn. The concentrations of these elements are low in groundwater collected upgradient of the ERD treatment area, indicating that, in the absence of the injected OC, the As that occurs naturally in the sediment is relatively immobile. Batch experiments conducted using sediments from the site inoculated with an Fe(III)- and As(V)-reducing bacterium and amended with lactate resulted in mobilization of As, Fe and Mn, suggesting that As mobilization in the field is due to microbial processes.     

Crustal impurities and the internal temperature of a neutron star crust

When the upper part of a neutron star crystallizes to form the crust, the constituting ions are trapped in the lattice as a result of the low diffusion rates in the solid phase. As a consequence, the local composition of the crust corresponds to the equilibrium condition at the melting point and not at the present internal temperature. The inclusion of the small entropic contribution to the free energy does not lead to marked changes in our view of the microscopic structure of a neutron star crust, because the melting temperature is much smaller than the typical energies at play in the crystal cell. However, mixing between layers characterized by different nuclear species is found to be an important effect for the production of impurities. We show that one should expect an increase of the thermal diffusion time through the crust at small temperatures, because of the decrease of thermal conductivity in relatively thin impurity-rich layers acting as isolating shields.     

A SIMPLE SOIL MOISTURE INDEX TO FORECAST CROP YIELDS

Neutron probe soil moisture measurements obtained biweekly during the growing season between 1982 and 1991 from multiple depths under grass-covered plots at 17 Illinois Climate Network sites are used to forecast crop yields. A Soil Moisture Index (SMIX) that combines the effect of intensity, duration, and timing of drought or excessively wet conditions was computed by integrating the quantity of available soil moisture throughout the rooting zone over the growing season. Relationships between the SMIX values and crop yields are evaluated at county, regional, and statewide scales. Coefficients of determination (r ²) for relationships between the SMIX values and maize, soybeans, and hay yields at the statewide level are 0.88, 0.74, and 0.81, respectively, when the period of integration is terminated at the end of the growing season. This new soil index can be employed to forecast yields as early as 12 weeks before harvest for the state of Illinois. However, predictions with RMSE ≤ 10% of the mean yield can be achieved only for SMIX integration periods ending 5, 9, and 6 weeks before harvest for maize, soybeans, and hay, respectively. Nomograms are presented for using the relationships between the SMIX values and crop yields to forecast Illinois's major crops well before harvest.     

Origin of the salt valleys in the Canyonlands section of the Colorado Plateau: Evaporite-dissolution collapse versus tectonic subsidence

The salt valleys over the axis of the salt-cored anticlines in the Paradox fold and fault belt (Canyonlands, Utah and Colorado) are created by subsidence of the anticline crests. Traditionally, the collapse of the anticlinal crests was attributed to dissolution of the salt walls (diapirs) forming the anticline cores. Recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions. This paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation.The development of contractional structures in salt dissolution experiments led the advocates of the tectonic interpretation to reject the dissolution-induced subsidence explanation. However, these salt dissolution models do not reproduce the karstification of salt walls in a realistic way, since their analog involves removal of salt from the base of the diapirs during the experiments. Additionally, numerous field examples and laboratory models conducted by other authors indicate that brittle subsidence in karst settings is commonly controlled by subvertical gravity faults.Field evidence against the regional extension model includes (1) a thick cap rock at the top of the salt walls, (2) the concentration of subsidence deformation structures along the crest of the anticlines (salt walls), (3) deformational structures not consistent with the proposed NNE extension, like crestal synforms and NE–SW grabens, (4) dissolution-induced subsidence structures controlled by ring faulting, revealing deep-seated dissolution, (5) large blocks foundered several hundred meters into the salt wall, (6) evidence of recent and active dissolution subsidence, and (7) the aseismic nature of the recently active collapse faults. Although underground salt dissolution seems to be the main cause for the generation of the salt valleys, this phenomenon may have been favored by regional extension tectonics that enhance the circulation of groundwater and salt dissolution.     

A multi-proxy record of the Last Glacial Maximum and last 14,500?years of paleoenvironmental change at Lone Spruce Pond, southwestern Alaska

Sediment cores from Lone Spruce Pond (60.007°N, 159.143°W), southwestern Alaska, record paleoenvironmental changes during the global Last Glacial Maximum (LGM), and during the last 14,500 calendar years BP (14.5?cal?ka). We analyzed the abundance of organic matter, biogenic silica, carbon, and nitrogen, and the isotope ratios of C and N, magnetic susceptibility, and grain-size distribution of bulk sediment, abundance of alder shrub (Alnus) pollen, and midge (Chironomidae and Chaoboridae) assemblages in a 4.7-m-long sediment sequence from the depocenter at 22?m water depth. The basal unit contains macrofossils dating to 25?C21?cal?ka (the global LGM), and is interpreted as glacial-lacustrine sediment. The open water requires that the outlet of the Ahklun Mountain ice cap had retreated to within 6?km of the range crest. In addition to cladocerans and diatoms, the glacial-lacustrine mud contains chironomids consistent with deep, oligotrophic conditions; several taxa associated with relatively warm conditions are present, suggestive of relative warmth during the global LGM. The glacial-lacustrine unit is separated from the overlying non-glacial lake sediment by a possible disconformity, which might record a readvance of glacier ice. Non-glacial sediment began accumulating around 14.5?cal?ka, with high flux of mineral matter and fluctuating physical and biological properties through the global deglacial period, including a reversal in biogenic-silica (BSi) content during the Younger Dryas (YD). During the global deglacial interval, the ??¹³C values of lake sediment were higher relative to other periods, consistent with low C:N ratios (8), and suggesting a dominant atmospheric CO₂ source of C for phytoplankton. Concentrations of aquatic faunal remains (chironomids and Cladocera) were low throughout the deglacial interval, diversity was low and warm-indicator taxa were absent. Higher production and air temperatures are inferred following the YD, when bulk organic-matter (OM) content (LOI 550?°C) increased substantially and permanently, from 10 to 30?%, a trend paralleled by an increase in C and N abundance, an increase in C:N ratio (to about 12), and a decrease in ??¹³C of sediment. Post-YD warming is marked by a rapid shift in the midge assemblage. Between 8.9 and 8.5?cal?ka, Alnus pollen tripled (25?C75?%), followed by the near-tripling of BSi (7?C19?%) by 8.2?cal?ka, and ??¹⁵N began a steady rise, reflecting the buildup of N and an increase in denitrification in soils. Several chironomid taxa indicative of relatively warm conditions were present throughout the Holocene. Quantitative chironomid-based temperature inferences are complicated by the expansion of Alnus and resulting changes in lake nutrient status and production; these changes were associated with an abrupt increase in cladoceran abundance and persistent shift in the chironomid assemblage. During the last 2,000?years, chironomid-assemblage changes suggest cooler temperatures, and BSi and OM values were generally lower than their maximum Holocene values, with minima during the seventh and eighth centuries, and again during the eighteenth century.     

Identification and delineation of saline soils using aerial photographs in Yamuna Alluvial plain,Haryana

Salinity is creating great problems in the Yamuna Alluvial Plain. State Government is taking steps for reclaiming these lands to increase agricultural production. Impeded drainage, excess canal irrigation, topography parent material, shallow depth and bad quality of ground water are the main factors which are responsible for the genesis of saline soils in the alluvial plains of Haryana. On the arial photographs tonal differences on account of salt concentration in the soil are clearly seen. These differences are aslo associated with physiography and soil conditions which can be easily delineated. The information thus; collected can be used for reclamation of saline soils.     

Refined relationship between the position of the fundamental OH stretching and the first overtones for clays

The aim of this paper is to determine a relationship between the wavenumbers of the first OH-stretching overtones (W_2OH) and the wavenumbers of the OH-stretching fundamentals (W_OH) to help to interpret the near-infrared (NIR) spectra. The first overtone (2OH) bands appear at wavenumbers less than twice those of the fundamental bands (OH), due to the anharmonic character of vibrations, X = W_2OH/2 - W_OH, with X being the anharmonicity constant. Talc samples with various crystal chemistries are used to solve the equation and the experimental data are well fitted with X = –85.6 cm^–1. As far as the authors are aware, it is the first time that the anharmonicity constant for the OH-stretching vibrations is determined for phyllosilicates. The anharmonicity constant remains almost unchanged for several types of clay samples. Therefore the relation, established from talc samples because their absorption bands are narrow and their wavenumber range of OH vibrations is wide, can be used for any other clay minerals.