Isotopic constraints on Columbia River flood basalt genesis and the nature of the subcontinental mantle

Pb, O, Nd, and Sr isotopic data for the Columbia River basalts paint a complex picture for the origin of this flood basalt province. At least 3 distinct mantle sources appear to have been involved, superimposed upon which are the effects of crystal fractionation and mass exchange with evolved crustal wallrocks. To a large degree, the initiation of Columbia River volcanism and the geochemical characteristics of the basalts appear to have been influenced by subduction of the Juan de Fuca plate beneath the North American plate in a manner analogous to the origin of back-arc basins. The physical structure of the crust appears to have influenced the late stage evolution of the magmas by directing the locus of eruption to the border between the ancient continental interior and much younger crust to the south and west. This proximity to the continental interior also allowed old enriched subcontinental mantle to become involved in the very late stages of Columbia River volcanism. An important consequence of the existence of enriched mantle regions beneath continents is that the combination, crust plus enriched mantle, requires more incompatible elements to have been extracted from the remainder of the mantle than would be the case if no enriched mantle existed.     

pp′-DDT adsorption to suspended particulate matter in sea water

A procedure was devised to study pp′-DDT [2,2-bis($\text{p-}\text{chlorophenyl}$)-1,1,1-trichloroethane] adsorption and desorption to suspended particulates in aqueous solutions. DDT adsorption to a marine sediment, sediment fractions, clay and humic acid suspended in sea water was investigated and the humic fraction was found to have a greater adsorbing capacity than the clay or sediment. Removal of the humic fraction from sediment reduced the adsorption capacity to less than 60 per cent of the original sediment sample. It was concluded that suspended humic particulates may be important agents for transporting chlorinated hydrocarbons through the water column and for concentrating them in sediments and in detritus-feeding organisms.     

The effect of annealing on the luminescence decay-time of synthetic calcite:Mn

Calcite was synthesized by four methods, and the luminescence decay-time was measured for nine samples before and after heating hydrothermally in the temperature range 200–400°C. Decay-time data were collected between room temperature and approximately 15 K. The decay time at room temperature is approximately 50 ms, with little difference between a given calcite before and after hydrothermal treatment. The decay time at 15 K is always greater than at room temperature as the effect of thermal quenching diminishes. Differences in decay time before and after heating are more apparent at low temperature owing to this reduction in thermal quenching. The decay time decreased significantly in two samples, and an increase in decay time was observed in the remaining seven samples following heating. Among the latter group, the change in decay time was insignificant in three samples. The results are compared with previous data in which it was shown that the effect of heating is to increase the intensity of luminescence.     

An Anatomy of Adaptation to Climate Change and Variability

Adaptation to climate variability and change is important both for impact assessment (to estimate adaptations which are likely to occur) and for policy development (to advise on or prescribe adaptations). This paper proposes an "anatomy of adaptation" to systematically specify and differentiate adaptations, based upon three questions: (i) adapt to what? (ii) who or what adapts? and (iii) how does adaptation occur? Climatic stimuli include changes in long-term mean conditions and variability about means, both current and future, and including extremes. Adaptation depends fundamentally on the characteristics of the system of interest, including its sensitivities and vulnerabilities. The nature of adaptation processes and forms can be distinguished by numerous attributes including timing, purposefulness, and effect. The paper notes the contribution of conceptual and numerical models and empirical studies to the understanding of adaptation, and outlines approaches to the normative evaluation of adaptation measures and strategies.     

RESEARCH ON THE RELATIONSHIP BETWEEN FRACTAL FACTORS AND TECTONIC ACTIVITY——A CASE STUDY OF SOUTHWESTERN YUNNAN BLOCK

Geomorphology could record long-term accumulation of tectonic movement and quantify it by relevant parameters.But because the influences of other factors such as climate and lithology,how to use the relevant parameters to reveal the relationship between geomorphology and tectonics is a research hot spot.In this paper,we utilize the variogram method and the cellular fractal model to estimate parameters such as the fractal dimension (D) and ordinate intercept (γ) from the SRTM3 DEM using a moving window operation.We compare the distribution characteristics of the parameters in different climate and lithology.The results indicate that the correlation between the parameters and lithology or climate is very poor.The fractal dimension (D) reveals a very good correlation with tectonics,which is low in tectonically inactive areas and high in active areas.It implies that fractal dimension (D) may be a new method for research of regional tectonic movement.     

Methane Emission Reduction: An Application of FUND

Methane is, after carbon dioxide, the most important anthropogenic greenhouse gas. Governments plan to abate methane emissions. A crude set of estimates of reduction costs is included in FUND, an integratedassessment model of climate change. In a cost-benefit analysis, methane emission reduction is found to be instrumental in controlling the optimal rate of climate change. In a cost-effectiveness analysis, methane emission reduction largely replaces carbon dioxide emission reduction. Methane emission reduction reinforces the case for international cooperation in climate policy, but complicates the efficient allocation of emission reduction efforts. Methane emission reduction at the short run does not help to achieve the ultimate objective of the Framework Convention on Climate Change.     

Middle Paleolithic occupation on a Marine Isotope Stage 5 lakeshore in the Nefud Desert,Saudi Arabia

Major hydrological variations associated with glacial and interglacial climates in North Africa and the Levant have been related to Middle Paleolithic occupations and dispersals, but suitable archaeological sites to explore such relationships are rare on the Arabian Peninsula. Here we report the discovery of Middle Paleolithic assemblages in the Nefud Desert of northern Arabia associated with stratified deposits dated to 75,000 years ago. The site is located in close proximity to a substantial relict lake and indicates that Middle Paleolithic hominins penetrated deeply into the Arabian Peninsula to inhabit landscapes vegetated by grasses and some trees. Our discovery supports the hypothesis of range expansion by Middle Paleolithic populations into Arabia during the final humid phase of Marine Isotope Stage 5, when environmental conditions were still favorable.     

A framework of Holocene and Late Pleistocene environmental change in eastern Iran inferred from the dating of periods of alluvial fan abandonment,river terracing,and lake deposition

We review studies of the Holocene and Late Pleistocene stratigraphy of eastern Iran to infer past changes in the environment within this presently arid region. We build a scenario of widespread, and presumably climatically driven, evolution of the landscape through the Holocene. Six sites, covering a 10° range in latitude, indicate a regional abandonment of alluvial fan surfaces at ～10 ± 3 ka, with the younger (～9 ka) end of this age range supported by several of the best-constrained studies. Incision of rivers into the fan surfaces has occurred in discrete stages in the early to mid-Holocene (～9–7 ka) leading to the formation of flights of river terraces. Detailed records of lakebed deposition in the presently arid interior of Iran are rare, though the available data indicate lake highstand conditions at <7.8 ka at South Golbaf in SE Iran and at < 8.7 ± 1.1 ka at the Nimbluk plain in NE Iran. The major periods of Holocene landscape development hence correlate with a period of time where water was more abundant than at present, with incision of rivers into thick alluvial deposits possibly occurring due to a combination of decreased sediment supply and high levels of precipitation, and with the formation of inset river terraces possibly responding to century-scale fluctuations in precipitation. No major geomorphic changes are identified within the later part of the Holocene, from which we infer that increased aridity has slowed evolution of the landscape. A decrease in precipitation in the mid-Holocene may have had a detrimental effect on bronze age societies in eastern Iran as has been inferred elsewhere in the eastern Mediterranean region. The pre-Holocene environmental changes in eastern Iran are less well constrained, though there are suggestions of alluvial fan abandonment at 40–60 ka, at ～80 ka, and at ～120 ka.