摘要:

The author demonstrates in different profiles originating from Hungary that the influence of the glaciations in the various phases of the Pleistocene on the small vertebrates is manifested in diverse forms. From the results of complex investigations, we can establish the effect of cold waves on the Pleistocene—Holocene boundary and also in various sections of the Middle Pleistocene. In faunas deriving from the Lower Pleistocene, the ecological demands of different (chiefly extinct) species seem to have been very different from those of their recent relatives and therefore the reflection of the climatic fluctuations in these animal associations is not unambiguous. The regional distribution of different elements of such faunas (e.g.Allophalomysfaunas with and without lemmings) shows the same evidence of spatial climatic changes as we have seen in different younger profiles in time.

ISSN:0016-786X    

DOI:10.1080/11035897609454388

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

As the result of palaeobiological investigation of the oldest sedimentary rocks of the earth's crust from different regions of the globe, it has been established that the rocks of the Archaean, Proterozoic and Palaeozoic, which differ in their lithological compositions and degrees of metamorphism, contain, in more or less quantity, the original algae-like micro-structures characterized by granular structure and a relatively low specific weight. The presence of these microstructures in the sedimentary rocks has been successively traced practically along the whole sequence of the Precambrian and Palaeozoic, including the oldest sediments of the Aldan Shield, the Kolsky peninsula, the Ukraine, the classic Archaean of India and the South-African Platform. Microstructures were also discovered in the Proterozoic of the Canadian Shield, Australia, North-Western Africa and Eurasia. The examination of microstructures under a light microscope has shown the stability of the morphological and structural peculiarities of these algae-like remains during the whole Precambrian and Palaeozoic. Morphological and structural evidences, characteristic differentiation of distribution in the rocks according to the facial type of sediments, general spreading on all continents and some other factors define the possibility of finding algae-like rock formed from the microstructures under study.

ISSN:0016-786X    

DOI:10.1080/11035897609454389

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Spinels, in which chromium is a major component, occur in impact melt rocks of rhyolitic composition and low chromium content in the Mien astrobleme. Chromium-rich spinels are zoned and become progressively poorer in Cr, Al, and Mg and enriched in Fe3+and Ti and change from normal to inverted spinel structure from core to margin. There is some evidence that the components of the spinel were derived from the decomposition and melting of a mafic mineral of the target rocks.

ISSN:0016-786X    

DOI:10.1080/11035897609454390

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Using Late Campanian subsurface data from western Nigeria, the frequencies of species of foraminifers and ostracods were weighed against 14 trace elements of the enclosing sediments (Si, Fe, Mg, Ca, Na, K, Ti, P, Mn, V, Mo, Sr, Pb and Zn) by standard methods of multivariate analysis. The method of canonical correlation requires the interpretation of two canonical variates. The first of these suggests a dipolar relationship between carbonate sediment and clastic components. The method of principal coordinates for Euclidean distances produces meaningful clusters, grouping the organisms into environmentally significant subsets. A largely unidirectional, ecological trend could be identified.

ISSN:0016-786X    

DOI:10.1080/11035897609454391

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

A Pre-Boreal water-level lowering in Lake Lyngsjö, central Halland, is described. During the culmination of the lowering, the water level may have been 4–5 m lower than it is nowadays, and Lyngsjö was then a closed lake with no outlet. The lowering indicates a distinct decrease in humidity during the later part of the Pre-Boreal period. Its recording in some other lakes is discussed.

ISSN:0016-786X    

DOI:10.1080/11035897609454392

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

A micro-probe study of six pairs of co-existing garnet and biotite samples from a polymetamorphic migmatite in the Göteborg area of Sweden demonstrated similar mineral compositions in the neosome and paleosome. Distribution equilibrium was closely approached, the distribution coefficient KDFeCa-Hihaving a mean value of 4.5 (one deviating value excluded). This indicated the occurrence of intermediate-to-high-grade regional metamorphism. Application of the distribution thermometer, as developed by Perchuk, yielded a temperature of 580±20°C. Comparatively high contents of Ca and Mn in the garnets suggested that this was a minimum estimate. The thermometrical estimates were in accordance with the general impression of low almandine—amphibolite-facies metamorphism, which was derived from the overall rock paragenesis in the region.

ISSN:0016-786X    

DOI:10.1080/11035897609454393

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Geomorphological studies carried out on West Spitsbergen in the neighbourhood of Van Mijenfjorden, the dating of deposits by the radiocarbon method, and chemical analyses have enabled us to reconstruct the geological evolution of this area in the Holocene. During this period, the Paula glacier repeatedly crossed Van Mijenfjorden and formed a complex of glacial deposits on the ancient sea terraces on the northern coast of the fiord. One of the most significant advances of the Paula glacier took place 7800–7600 years ago. As this advance was for the first time reliably differentiated on Spitsbergen, it would be expedient to call it the Damesmorenen stage. Among the latest advances of the Paula glacier, the advance during “the little ice age” was dated. On the basis of the results obtained, it is possible to assume that the advances of the Paula glacier were of the nature of surges.

ISSN:0016-786X    

DOI:10.1080/11035897609454394

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The Biot—Ramberg equation for the dominant wavelength of buckle folds was experimentally tested by deforming models in simple shear. The simplified equation seems to be a good approximation for large viscosity contrasts but has to be modified somewhat to correspond to smaller viscosity contrasts.

ISSN:0016-786X    

DOI:10.1080/11035897609454395

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Most of the 2.2-m-long sediment core from Lake Rudetjärn proved to be distinctly laminated. A preliminary report is presented on the nature of the laminations—varves-and their variability.

ISSN:0016-786X    

DOI:10.1080/11035897609454396

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The results of a magnetometric survey of the Alnö Complex suggest that it consists of the main intrusion in the north-eastern part of Alnö Island, a satellite intrusion of mainly carbonatite at Söråker (measuring about 1 × 1.4 km) and the earlier recognized satellite vent at Båräng. The new picture of the Alnö Complex, which is in striking contrast to the views of von Eckermann, is discussed.

ISSN:0016-786X    

DOI:10.1080/11035897609454397

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor