Curie Temperature Analyses of Upper Jurassic and Lower Cretaceous Pelagic Limestones

Summary. Magnetic extracts were prepared from samples of Upper Jurassic and Lower Cretaceous pelagic limestones from France and Spain. Thermomagnetic analysis of the magnetic extracts using a microbalance required careful monitoring of base weight changes during heating. Heating in argon gas atmosphere induced production of magnetite during heating while slight oxidation occurred during heating in air. the dominant Curie temperature detected by the thermomagnetic analyses was the 585°C Curie temperature of magnetite. the 680°C Curie temperature of haematite was only detected when isothermal remanent magnetism (IRM) data indicated large concentrations of haematite. Even when IRM data indicated its presence, the thermomagnetic analyses did not detect the Neel temperature of goethite. Although thermomagnetic analyses of magnetic extracts provide more direct identification of the dominant, strongly ferromagnetic minerals, IRM acquisition and subsequent thermal demagnetization is a superior technique in detecting high coercivity, weakly ferromagnetic minerals such as goethite and haematite.     

Measurements of the Natural Remanent Magnetism and Anisotropy of Susceptibility of some Swedish Glacial Silts

Summary. This paper describes the results of measurements of the magnetic remanence and anisotropy of susceptibility of some Swedish varved silts. An attempt has been made to observe in nature the effects, which have been demonstrated in the laboratory, of water currents on these properties and to obtain new data on the effects of slopes on the direction of remanence.
It was not possible to obtain quantitative confirmation of the effects of water currents though it is shown that the field results fit qualitatively with those from the laboratory and that the effects of currents may in favourable circumstances be neglected or corrected for. By combining the new data on the effects of slopes with those previously published it has been found possible to demonstrate the importance of grain size in determining the magnitude of the bedding error correction and an expression has been found which gives this correction to an accuracy comparable with the error of measurement of remanence direction.
It is concluded that, since all known systematic deviations of the remanence direction may now be corrected for, it should be possible, in suitable circumstances, to obtain reliable estimates of field directions over the last 10,000 years from measurements on the Swedish varves.     

湘桂黔滇藏红色岩溶风化壳发育模式

基于对湘，桂、黔，滇，藏等地岩溶区红色风化壳的野外和室内研究，从表生地貌学，粘土矿物学和地球化学角度分析红色石灰土性质与地貌演化的关系，提出红色岩溶风化壳发育的二阶段模式；1）地貌夷平-风化物质积累阶段，在地貌演化过程中溶蚀残余物质不断积累，最后在夷平面上形成厚层连续的泥质风化壳，夷平面的地貌水文条件有利于粘粒的形成和保存，但限制了富铝化作用的有效进行，造就了岩溶风化壳粘粒含量高，富铝化程度低的特点，这与研究区23个红色岩溶风化壳剖面化学，粒度特征和粘土矿物组合特点一致。2）地貌切割-风化壳淋溶阶段，原始夷平面上的风化壳大多呈灰色，只有在构造隆升和地表微切割导致地下水位降低，淋溶条件开始改善的情况下，风化壳才有可能枞根本上转为红色。     

Urbanization and depopulation in the Alps

Demographic developments in the European Alpine region are analyzed over the period 1870-1990. The region is defined as including parts of Germany, France, Italy, Liechtenstein, Austria, Switzerland, and Slovenia. "Studies of growth, stagnation, decline, commune size, and altitude in almost 6,000 communes are presented on three colored maps.... It is apparent that two highly divergent processes are at work and, accordingly, statistical mean values reveal little of importance. Approximately one-half of Alpine Europe is undergoing general economic and demographic growth and has experienced significant increase in population since the end of the agricultural era. This development has taken place primarily in low-lying valleys and basins and in areas bordering the Alps that have good access to transport routes. Tourism is not as widespread as generally assumed and is usually characterized by a punctate pattern. Only in the western part of the Eastern Alps does tourism account for widespread population growth at higher altitudes; elsewhere the Alps have not been affected by modern development and the economy and population are declining, with some areas in danger of becoming completely abandoned. The results challenge the earlier concept of the Alps as a rural region, once populated by peasants, where tourism now plays a major role." (EXCERPT)     

Remanent magnetization of Precambrian and Cretaceous kimberlites in South Africa

Summary. Middle Precambrian and Cretaceous kimberlites were collected from three sites (Premier, Montrose and National) and two sites (Wesselton and Koffyfontein) in South Africa respectively. The natural remanent magnetization of these rocks remains stable to both alternating field and thermal demagnetization. The virtual geomagnetic pole-positions derived from the directions of stable remanence of the Precambrian rocks can be correlated with palaeomagnetic poles obtained from other Middle-Late Precambrian rocks in Africa. The Cretaceous poles for the Wesselton and the Koffyfontein rocks coincide with other Cretaceous poles.     

Demographic trends in the Austro-German Alps

Population trends in the German and Austrian Alps between 1971 and 1981 are described. The effects of commune size, tourism, and altitude on population dynamics are considered.     

Foraminiferal morphogroups in dysoxic shelf deposits from the Jurassic of Spitsbergen

Analysis of benthic foraminiferal assemblages was performed in Bathonian to Kimmeridgian deposits through a section covering the lower half of the Agardhfjellet Formation in central Spitsbergen. The section consists mainly of organic-rich shales, which contain low-diversity agglutinated assemblages. In this foraminiferal succession five morphogroups were differentiated according to shell architecture (general shape, mode of coiling and number of chambers), integrated with the supposed microhabitat (epifaunal, shallow infaunal and deep infaunal) and feeding strategy (suspension-feeder, herbivore, bacterivore, etc.). The environmental evolution of the analysed section is interpreted by using the stratigraphic distribution of morphogroups, combined with species diversities and sedimentary data, in a sequence stratigraphic framework. The section comprises two depositional sequences, which demonstrate that species diversity and relative frequency of morphogroups are correlative with transgressive–regressive trends controlling depth and oxygenation of the water column. In both sequences, the maximum flooding interval is characterized by increased organic carbon content, dominance of the epifaunal morphogroups and reduced species diversity: features reflecting the increased degree of stagnation separating the transgressive phase from the regressive phase.