Measurements of thermal conductivities in a fresh water lake

Summary Thermal conductivities at various depths are estimated from the conduction of heat in a freshwater lake during a period of rapid heating leading to the formation of a thermocline. The values obtained can be related to the difference between density at the depth involved and that at the surface.Now with the Shell Petroleum Company.     

THE REFRACTION OF MICROSEISMS ON APPROACHING THE COAST OF THE BRITISH ISLES

Summary. Refraction diagrams are drawn for 6-sec microseisms when they approach the British Isles from the SW, WSW, W, WNW and NW directions. Refraction diagrams are also drawn for 4-^s and 8-^s microseisms approaching from a westerly direction. The diagrams show that all the westerly microseisms are very much reduced. This effect is confirmed by measurement of the vertical component of the microseisms due to sixteen storms which occurred during the period 1945–53.     

Evolution of the Neoproterozoic Delgo suture zone and crustal growth in Northern Sudan: geochemical and radiogenic isotope constraints

In the Delgo basement area of northern Sudan, low to medium grade metamorphosed volcanic, sedimentary and plutonic rocks are surrounded by high grade gneisses. A NNE-SSW trending suture zone can be defined by the lithological, chemical and structural characteristics of several distinct units. The early Proterozoic gneiss terrain is overlain by metasedimentary units, the metamorphism of which has been dated by the Sm-Nd whole rock-mineral technique (702 ± 27 Ma in the west, 592 ± 16 Ma in the east). In the central part, the Abu Sari volcanic rocks show geochemical signatures of formation at an arc, with a protracted tholeiitic, calc-alkaline and shoshonitic evolution. The overlying El Hamri ophiolite contains chemical features of a back-arc tectonic environments. The ophiolite was dated by the Sm-Nd whole rock method on metagabbros at 752 ± 48 Ma. The further extension of this oceanic basin into the Jebel Rahib in the south-west was dated at 707 ± 54 Ma (Sm-Nd whole rock and minerals).Widespread suite of syn-tectonic granitoid intrusives displays subduction-related characteristics. They where emplaced between 650 to 760 Ma (Pb-zircon evaporation method). Their Nd and Sr isotopic compositions indicate a changing pattern of island arc to active continental margin character along an east-west transect and suggest a west to north-west dipping subduction zone. All units were juxtaposed at the minimum age of 600 Ma and rearranged during an extensional event, which was dated by the Rb-Sr thin slab technique (546 ± 19 Ma) on a migmatite. The Delgo suture provides evidence of a complex terrane pattern in north-east Africa and crustal growth during the Pan-African event by the addition of oceanic material to pre-existing continental crust.     

A conceptual framework for multi-regional climate change assessments for international market systems with long-term investments

A conceptual framework for climate change assessments of international market systems that involve long-term investments is proposed. The framework is a hybrid of dynamic and static modeling. Dynamic modeling is used for those system components for which temporally continuous modeling is possible, while fixed time slices are used for other system components where it can be assumed that underlying assumptions are held constant within the time slices but allowed to vary between slices. An important component of the framework is the assessment of the “metauncertainty” arising from the structural uncertainties of a linked sequence of climate, production, trade and decision-making models. The impetus for proposing the framework is the paucity of industry-wide assessments for market systems with multiple production regions and long-term capital investments that are vulnerable to climate variations and change, especially climate extremes. The proposed framework is pragmatic, eschewing the ideal for the tractable. Even so, numerous implementation challenges are expected, which are illustrated using an example industry. The conceptual framework is offered as a starting point for further discussions of strategies and approaches for climate change impact, vulnerability and adaptation assessments for international market systems.     

Sr isotopes in natural waters: Applications to source characterisation and water–rock interaction in contrasting landscapes

Strontium isotopes (⁸⁷Sr/⁸⁶Sr) are routinely measured in hydrochemical studies to determine sources and mixing relationships. They have proved particularly useful in determining weathering processes and quantifying end-member mixing processes. A number of routine case studies are presented which highlight that Sr isotopes represent a powerful tool in the geochemists toolbox helping to constrain weathering reactions, weathering rates, flow pathways and mixing scenarios. Differences in methodologies for determining the weathering component in natural environments, inherent differences in weathering rates of different minerals, and mineral heterogeneity often cause difficulties in defining the weathering component of different catchments or aquifer systems. Nevertheless, Sr isotopes are useful when combined with other hydrochemical data, to constrain models of water–rock interaction and mixing as well as geochemical processes such as ion-exchange. This paper presents a summary of recent work by the authors in constraining the sources of waters and weathering processes in surface catchments and aquifers, and indicates cases where Sr isotopes alone are insufficient to solve hydrological problems.