Granitic magmatism,basement ages,and provenance indicators in the Malay Peninsula: Insights from detrital zircon U–Pb and Hf-isotope data

The Malay Peninsula lies on two continental blocks, Sibumasu and East Malaya, which are intruded by granitoids in two provinces: the Main Range and Eastern. Previous models propose that Permian–Triassic granitoids are subduction-related and syn-to post-collisional. We present 752 U–Pb analyses that were carried out on zircons from river sands in the Malay Peninsula; of these, 243 grains were selected for Hf-isotope analyses. Our data suggest a more complex Sibumasu–East Malaya collision history. ¹⁷⁶Hf/¹⁷⁷Hf_i ratios reveal that Permian–Triassic zircons were sourced from three magmatic suites: (a) Permian crustally-derived granitoids, (b) Early-Middle Triassic granitoids with mixed mantle–crust sources, and (c) Late Triassic crustally-derived granitoids. This suggests three Permian–Triassic episodes of magmatism in the Malay Peninsula, two of which occurred in the Eastern Province. Although the exact timing of the Sibumasu–East Malaya collision remains unresolved, current data suggest that it occurred before the Late Triassic, probably in Late Permian–Early Triassic. Our data also indicate that Sibumasu and East Malaya basements are chronologically heterogeneous, but predominantly of Proterozoic age. Some basement may be Neoarchaean but there is no evidence for basement older than 2.8 Ga. Finally, we show that Hf-isotope signatures of Triassic zircons can be used as provenance indicators.     

Water Flows Toward Power: Socioecological Degradation of Lake Urmia,Iran

Water is an invaluable resource, and equitable access to it is a fundamental human right. Disenfranchised groups often lose access to water resources because their interests are not well represented by decision makers. Excluding these groups from resource management policy often results in myopic decisions that contribute to further ecosystem damage. We describe the ecological degradation of Lake Urmia in Iran, which has recently experienced increased salinity and declining water quantity. The lake is a UNESCO Biosphere Reserve and Ramsar site, and supports unique biodiversity in the region. The lake's decline is driven by the destruction of Zagros forests and the government's water policies, which diverted water to more politically connected agricultural land users, increasing social inequity and prompting more deforestation. The most straightforward restoration solution is to discontinue the diversions and allow critical inflows to recharge Lake Urmia, preserving the lake and wetlands for migratory birds, tourists, and local communities.     

Spatial analysis weighting algorithm using Voronoi diagrams

Data layers that represent geographical constraints in a multidimensional GIS model must be appropriately weighted to effectively account for the diversity as well as the functional and spatial interrelationships between the constraints. This paper presents a spatial analysis weighting algorithm (SAWA) using Voronoi diagrams. The basic functions of the SAWA are defined so that the spatialization of weights is done according to two approaches: a global spatialization method based on the statistical distribution of the original data and a contextual approach where neighbourhood defined by Voronoi diagrams is integrated into the weighting functions. Different simulations on artificial and real maps applied to the problem of shortest path optimisation are analysed. The results show that the effective integration of the spatial dimension in a weighting process is not only possible but also improves the optimisation of shortest paths. Research is continuing to improve the contextual phase of the algorithm.     

The increasing CO2 concentration in the atmosphere and its implication on agricultural productivity II. Effects through CO2-induced climatic change

In a prior paper (Part I), the point was made that, assuming an unchanged climate, water use efficiency in agricultural crop production will likely be favored by the increase in CO₂ concentration projected to occur within the next half century. Since climatic changeis likely to result from the CO₂ concentration increase, its possible impacts on agricultural productivity must also be considered. An attempt to do so, using the Great Plains region of North America as a case study, is reported in this paper (Part II). A number of climatic models predict significant increases in surface temperature. Manabe and Wetherald's (1980) model provides the most specific projections for a hypothetical Northern hemisphere continent. That model also predicts an intensification of the hydrologic cycle with rainfall distribution altered so that some zones will receive more and some less as a result of a doubling in the atmospheric CO₂ concentration. The zone between 37 and 47° N latitude will suffer a reduction in availability of soil moisture. A number of regression models of grain yield as a function of temperature and precipitation have been used to anticipate the impacts of the projected climatic changes. The value of this approach is questioned. An alternative approach - the study of the migration of major agricultural crops across strong climatic gradients - is proposed. Changes in the geographical distribution of the hard red winter wheat zone in North America provide an example. The point is also made that factorscurrently limiting food production must be considered in order to predict the possible impacts of any given climatic change. In the central Great Plains today, the energy consumed by evapotranspiration often exceeds that supplied by net radiation since sensible heat advection from dryer regions to the south and west provides a major additional input of energy. If, as models project, the excess of precipitation over evaporation increases south of 37° N, the advection of sensible heat and, hence, the rates of evapotranspiration and degree of water stress on growing plants could be reduced in the adjacent regions to the north. Published as Paper No. 6123, Journal Series, Nebraska Agricultural Experiment Station. The work reported was conducted under Regional Research Project 11-033 and Nebraska Agricultural Station Project 11-049. George Holmes Professor of Agricultural Meteorology, Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, Nebraska, 68583-0728.     

SOIL VARIATION ON NORTH AND SOUTH SLOPE CATENAS ON A KAME IN SOUTHEAST WISCONSIN

Soils from two catenas on north-and south-facing slopes of a kame were analyzed to determine the effect of lithology, topography, and microclimate on profile development. In loess on the north-facing slope, where microclimate favored CaCO₃ dissolution and clay translocation, pedogenesis was rapid and an A-E-Bt-C profile developed. In contrast, an A-Bt-C profile developed on the south-facing slope. In gravel where limestone/dolostone dissolution was slow, A-C profiles were found and CaCO₃ was depleted to a ≤ 25-cm depth, 20± cm less than reported for similar Michigan soils. Slopewash and runoff are inferred to have caused silt accumulations and greater infiltration at the base of ≥ 20° slopes, resulting in a thicker solum in foot-and toe-slope positions, whereas on slopes of ≤ 7° infiltration and interflow are the dominant processes, resulting in a thicker solum on the transportational midslope. The differences in soil profile development are attributed to sediment facies changes at 25- to 50-cm depth and resulting groundwater movement. [Key words: soil development, soil spatial variability, kame slope catena, Wisconsin.]     

Occurrence and significance of a cold-water carbonate pseudomorph in microbialites from a saline lake

Micron-scale pseudomorphs of calcite after ikaite were discovered in microbialites from Manito Lake, a large hypersaline lake in the Great Plains of western Canada. Although environmental conditions in the lakes of this region (seasonally cold temperatures, high salinities and elevated productivity) suggest that ikaite should be common, this is the first documentation of lacustrine ikaite in Canada and the Great Plains region of North America. The calcite pseudomorphs form a porous dendritic fabric, comprise the interiors of massive shoreline microbialite mounds and pinnacles, and are encased in centimeter-scale, laminated dolomite-aragonite rinds. Because of the limited thermodynamic stability of ikaite at or near freezing temperatures, the psuedomorphs of this mineral provide evidence of an extended cold episode during the first millennium AD. The Manito deposits also show high δ¹³C values, indicating elevated productivity and δ¹⁸O signatures are consistent with precipitation in a cold, somewhat fresher lake than present.