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| Registros recuperados: 19 | |
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| Sitter, L.U. de. |
| § 1. Plastic deformation of solid matter under high confining pressures has been insufficiently studied. Jeffreys 1) devotes a few paragraphs to deformation of solid matter as a preface to his chapter on the isostasy problem. He distinguishes two properties of solid matter with regard to its behaviour to external forces: the Rigidity and the Strength. The rigidity being the resistance to elastic stresses, the strength the resistance to shearing forces. The strength has been surpassed when a differential force results in a permanent deformation. Therefore the strength equals the differential pressure necessary to effect shearing or plastic deformation. |
| Tipo: Article / Letter to the editor |
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| Ano: 1937 |
URL: http://www.repository.naturalis.nl/record/505930 |
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| Sitter, L.U. de; Sitter-Koomans, C.M. de. |
| In the Bergamasc Alps we have observed one major unconformity between the Basement rock and the overlying Permian. The total absence of any recognisable Palaeozoic sedimentary rocks accentuates this unconformity, and moreover this enormous hiatus makes the dating of any Palaeozoic event impossible. However, by comparison with the Central Alps and Kärnten, we learned that the Asturian orogenitic phase precedes the deposition of the first volcanic sediments. In analogy with the Aar and Gotthard masses we presumed the intrusion of the less metamorphic ortho rocks of the Basement, the granodiorite and the gneiss chiaro, to be of Upper Carboniferous age. The close resemblance of the chemical composition and differentiation of the Permian volcanic rocks and the... |
| Tipo: Article / Letter to the editor |
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| Ano: 1949 |
URL: http://www.repository.naturalis.nl/record/505987 |
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| Sitter, L.U. de; Zwart, H.J.. |
| The geology of the map sheets 1:50.000, 1 Garonne and 2 Salat of the Geological map of the Central Pyrenees is described. The stratigraphic sequence consists of Paleozoic rocks from the Cambro-Ordovician to the Carboniferous, and of Mesozoic rocks from the Trias up to the Tertiary. Hercynian and Alpine orogenies have acted on this intercontinental mountain chain. The Hercynian orogeny is accompanied by epi-to cata-zonal metamorphism in which several successive stages can be recognized. The Alpine orogenesis consists also of successive stages of which the Pre-Cenomanian one has been accompanied by basic rock intrusion and a particular kind of metamorphism. In the structure presented on these sheets a stretch of the axial zone is represented and a part of... |
| Tipo: Article / Letter to the editor |
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| Ano: 1962 |
URL: http://www.repository.naturalis.nl/record/505981 |
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| Sitter, L.U. de. |
| § 1. In this study only those folds as observed in the upper sedimentary layers of the Earth’s crust will be treated. Even with this restriction the subject is still so complicated, that we must narrow the scope to be able to treat it from a theoretical point of view. Hence we will confine ourselves to simple folds as synclines and anticlines, leaving alone those intricate structures generally known as Alpine folding. On the other hand faults connected with folding are such a common feature that any theory that does not take them into account will be valueless. Folding is the result of tangential forces acting at unknown depth. Only in very few instances we have some idea at what depth the force is active. In the Jura mountains for instance we know that... |
| Tipo: Article / Letter to the editor |
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| Ano: 1936 |
URL: http://www.repository.naturalis.nl/record/505733 |
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| Sitter, L.U. de. |
| The construction of block diagrams is a very lengthy procedure if use be not made of one of the apparatuses described in Lit. 1 and 3. The non-mechanical construction can be effected in various ways: 1. By constructing a large number of parallel profiles, which are drawn usually in isometric projection where the length in the direction of the profiles, the distance between them, and the vertical scale remain similar. Cf. fig. 1a and 1c (the vertical scale of fig. 1c is increased to twice its size). |
| Tipo: Article / Letter to the editor |
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| Ano: 1937 |
URL: http://www.repository.naturalis.nl/record/505810 |
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| Sitter, L.U. de; Zwart, H.J.. |
| In 1958 werden de karteringen in de Centrale Pyreneeën en in het noorden van de provincie Leon (zuidrand Ast.-Cantabrisch Gebergte) voortgezet, het werk in Galicië niet. In de Centrale Pyreneeën werd een eerste verkenning in het Ribagorzana dal aangevangen, waarover hier nog niet gerapporteerd wordt. Het werk in het Segre dal werd voortgezet, terwijl de kartering van een klein ingewikkeld gebied in een oostelijk zijdal van de Pallaresa werd begonnen en beëindigd. De karteringen in het noorden van Andorra en over de grens in Frankrijk werden eveneens voortgezet. |
| Tipo: Article / Letter to the editor |
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| Ano: 1959 |
URL: http://www.repository.naturalis.nl/record/505780 |
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| Sitter, L.U. de. |
| Depuis 1948 des groupes d'étudiants en géologie de l'Université de Leiden sous ma direction, plus tard assisté par M. Zwakt, se sont occupés de la géologie du Primaire des Pyrénées centrales. Le levé s'est déplacé graduellement du Nord vers le Sud et de l'Est vers l'Ouest, de sorte qu'en 1953 nous avons dépassé la frontière franco-espagnole et entrepris la cartographie du Val d'Aran et de la Haute Pallaresa. Evidemment nous nous sommes basés largement sur les travaux de nos prédécesseurs, français surtout, et sur les feuilles au 80.000ième de la carte géologique, dont surtout les nouvelles éditions des feuilles de Foix et de Bagnères de Luchon ont été un precieux appui. Tous les noms des grands géologues pyrénéens, de Leymerie, Caralp, Mussy, Dalloni, Léon... |
| Tipo: Article / Letter to the editor |
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| Ano: 1953 |
URL: http://www.repository.naturalis.nl/record/505772 |
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| Sitter, L.U. de; Zwart, H.J.. |
| In 1957 werden de karteringen in twee gescheiden gebieden in de Pyreneeën voortgezet, verder in een gebied in N.-Leon aansluitend aan het N.-Palenciagebied begonnen en in Galicia eveneens voortgezet. In de Spaanse Pyreneeën werd dit jaar begonnen met gebieden, die uit het Segredal te bereiken zijn en op de duur zullen aansluiten met het Pallaresagebied. In de Franse Pyreneeën werd het onderzoek aan het massief van Aston voortgezet. |
| Tipo: Article / Letter to the editor |
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| Ano: 1957 |
URL: http://www.repository.naturalis.nl/record/505968 |
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| Sitter, L.U. de; Bosch, W.J. van den. |
| The present map is the continuation of the map published by De Sitter in 1962. The folded Precambrian basement in this area is overlain unconformably by Cambrian up to Carboniferous strata. The Palaeozoic has been uplifted during the Bretonic phase, and folded during the Sudetic, Asturian, and Saalic phases. In the western end of the Leónides the structures known from the eastern part of the Luna unit do not continue but are replaced bij one syncline and a number of thrusts. Major block faulting of the basement determined the curved structure of the ""Asturian Knee"" and also the diverse contemporaneous directions of thrusting and folding. Thinly developed Devonian of the Caldas Formation demonstrates the presence of a structural ridge early during the... |
| Tipo: Article / Letter to the editor |
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| Ano: 1969 |
URL: http://www.repository.naturalis.nl/record/505645 |
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| Sitter, L.U. de. |
| Serrant de près le lac de Lugano, se trouve un vieux pays volcanique, environné de montagnes calcaires escarpées, qui, malgré son peu d'étendue a une histoire géologique des plus intéressantes. Les laves et les tufs de ces volcans anciens sont d’une grande diversité et ont fourni en ces derniers temps la matière de recherches récemment couronnées par les analyses chimiques de Mlle Koomans (1937). A peu près au même temps que les étudiants en géologie de Leyde s’appliquaient à l’étude de cette région volcanique ceux de Bâle exploraient les roches sédimentaires environnantes. Grâce à ces différentes recherches conduites tant sur le terrain qu’en laboratoire, l’histoire géologique de ce complèxe nous est devenue familière. Cependant il nous manquait encore... |
| Tipo: Article / Letter to the editor |
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| Ano: 1939 |
URL: http://www.repository.naturalis.nl/record/505831 |
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| Sitter, L.U. de. |
| Le terrain exploré est limité au Nord par une ligne droite, qui va de Ghirla en passant par Marzio à Brusimpiano. La limite Est est formée par le lago di Lugano et par la vallée de Porto Ceresio jusqu’à Pogliana. La limite Sud est plus irrégulière; elle passe au Sud de Pogliana vers le sommet de la Poncione di Ganna et descend après vers S. Gemolo. La limite Ouest est formée par le Valganna. La surface de tout le terrain exploré est à peu près de 24,5 km2. Les limites Nord et Sud sont formées par des sédiments mésozoïques, que je n’ai point examinés. Les récentes recherches de M. A. Senn nous ont fait connaître les formations mésozoïques au Sud de mon terrain. Les mêmes formations au Nord constituent le sujet d’une étude déjà entreprise. |
| Tipo: Article / Letter to the editor |
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| Ano: 1925 |
URL: http://www.repository.naturalis.nl/record/505846 |
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| Sitter, L.U. de; Zwart, H.J.. |
| Mapping of the Paleozoic of the Central Pyrenees by students in geology of Leiden University under the directorship of Prof. Dr L.U. de Sitter started in 1948 with the Arize massif. Since then the survey has shifted first eastwards, 1949 St. Barthélemy massif; then westwards, 1950 Salat valley; 1951 Riberot valley (sheet 2); 1952, Garonne valley (sheet 1), and then southwards, 1953 and 1954 Valle de Arán, then south again to the Pallaresa and the Sègre (1955—1957). The survey has been restricted almost exclusively to the Paleozoic because the Mesozoic had been mapped by Casteras (1933) in the north and by Misch (1934), in the south, therefore only the Paleozoic rocks in their nonmetamorphic and metamorphic state have been differentiated on the map, whereas... |
| Tipo: Article / Letter to the editor |
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| Ano: 1957 |
URL: http://www.repository.naturalis.nl/record/505682 |
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| Sitter, L.U. de. |
| Un des plus grands phénomènes structuraux des Pyrénées est sans doute la faille Nord-Pyrénéenne qui longe la zone axiale depuis la Méditerranée jusqu'à la côte atlantique. Elle est caractérisée par plusieurs particularités exceptionelles, dont le métamorphisme des terrains jurassiques et crétacés inf., accompagné d'intrusions de roches basiques est le plus important. |
| Tipo: Article / Letter to the editor |
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| Ano: 1953 |
URL: http://www.repository.naturalis.nl/record/505720 |
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| Sitter, L.U. de; Zwart, H.J.. |
| In 1956 werden de karteringen in de Pyreneeën, N.-Palencia (Asturië) en Galicië voortgezet. Geen nieuwe gebieden werden in het onderzoek betrokken, die niet direct aansloten bij die van vorige jaren. In de Pyreneeën werd als nieuw werk voornamelijk uitgegaan van de kartering in het zuidelijk gedeelte van de Noguera Pallaresa tussen Llavorsi en Pobla de Segur. De Flamisell en de Mañanet werden in het onderzoek betrokken. Bovendien werd door Dr. Zwart en de Heer Allaart samen met de Heer Verspijck de metamorfe zone rond de Ariège opnieuw in studie genomen. |
| Tipo: Article / Letter to the editor |
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| Ano: 1957 |
URL: http://www.repository.naturalis.nl/record/505779 |
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| Sitter, L.U. de. |
| In a very simplified form one could say that with the exception of the Undation theory of van Bemmelen (1933a—d, 1948, 1952) and suggestions by Glangeaud (1947, 1948) the orogenic forces are generally sought in a lateral compression either by contraction due to cooling (Jeffreys, 1952) or under the influence of convection currents (Vening Meinesz, 1934, 1950; Griggs, 1939; Hess, 1948, etc.) below the crust. In the original conception of Vening Meinesz the buckling started as an elastic deformation but since Bijlaard (1938) showed that plastic buckling oblique to the main stress direction was more probable, Vening Meinesz changed over to this view. The difficulty in the elastic buckling hypothesis was the enormous stress (40—50.000 kg/cm²) needed to buckle... |
| Tipo: Article / Letter to the editor |
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| Ano: 1955 |
URL: http://www.repository.naturalis.nl/record/505800 |
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| Sitter, L.U. de; Boschma, D.. |
| The Carboniferous Pisuerga basin developed north of the León line and as such is the most eastern one of the Asturide basins. The Carboniferous sequence is subdivided into Ruesga Group (roughly Lower Carboniferous + Namurian), Yuso Group (roughly Westphalian) and Cea Group (roughly Stephanian). Since the beginning of the Yuso Group the Pisuerga basin became subdivided into a western and eastern basin and since the beginning of the Cea Group the western basin became subdivided into two separate basins. The main folding started during the Stephanian. A remarkable interaction of epeirogenic and orogenic movements leads to the analysis of a close relation between sedimentological and structural features. Several pronounced structural lineaments can be traced... |
| Tipo: Article / Letter to the editor |
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| Ano: 1965 |
URL: http://www.repository.naturalis.nl/record/505953 |
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| Sitter, L.U. de. |
| Sedert 1951 werden in de vorm van gestencilde jaarverslagen de wetenschappelijke resultaten van het veldwerk in de Pyreneeën, in Asturië en elders aan geïnteresseerden, voornamelijk de medewerkers, uitgereikt Deze jaarverslagen, en ook dit verslag, werden door de eerst genoemde auteur samengesteld uit de verzamelde verslagen van alle medewerkers. Teneinde een betere vorm en een grotere verspreiding mogelijk te maken werd besloten deze jaarlijkse wetenschappelijke verantwoording in de L.G.M. op te nemen. De hier bijgevoegde kaartjes van de Pyreneeën en van het Asturische gebied (fig. 1 en 2) geven de ontwikkeling van de karteringen in tijd en ruimte weer. Enkele gebieden werden door verschillende opeenvolgende onderzoekers in studie genomen (alleen de... |
| Tipo: Article / Letter to the editor |
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| Ano: 1956 |
URL: http://www.repository.naturalis.nl/record/505752 |
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| Kuenen, Ph.H.; Sitter, L.U. de. |
| The investigation of geological structures due to folding led de Sitter to form an opinion on the mechanical problems involved (Bibl. 7). His principal contention is that in simple cases the relative movements of particles with respect to eachother during deformation leading to a fold, have been purely concentric. During such concentric deformation all layers maintain their original thickness and length over the whole profile. All differential movements of neighbouring particles are parallel and therefore concentric. Towards the core of the anticlines and deeper down in the crust the geometrical relations, as construction will show, necessitate a deviation from this principle and either thrusting or plastic thickening of the rocks must take place. The... |
| Tipo: Article / Letter to the editor |
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| Ano: 1938 |
URL: http://www.repository.naturalis.nl/record/505864 |
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| Registros recuperados: 19 | |
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