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| Titel: |
Fossil palynomorph deformation and its relationship to sedimentary deposition |
| Auteur: |
Guy-Ohlson, Dorothy Ohlson, Nils Gunnar Lindqvist, Bengt |
| Verschenen in: |
GFF |
| Paginering: | Jaargang 110 (1988) nr. 2 pagina's 111-119 |
| Jaar: |
1988 |
| Inhoud: |
Toarcian bore core samples of siltstones from Vilhelmsfalt, Skåne, Sweden contain large numbers of algal cysts of the genus Tasmanites. The cysts are preserved as complete and deformed spheres at different stages of development. They are often filled with diagenetic pyrite, varying in habit from spheres to octahedral crystals. A comparison of the degree of deformation is made between cysts found in situ in thin section and cysts extracted chemically for palynological investigation. In order to express and evaluate more precisely the deformations, methods developed in solid mechanics have been applied. The palynomorph is regarded as a spherical shell subjected to a sedimentation load which is mainly uniaxial. The assumptions are made that the spheres remain complete if the shell is filled so that an interior pressure can balance the exterior, and that if deformation does occur it is purely elastic. The fraction of deformed shells is an estimate of the probability of shells lacking interior counter pressure. A probabilistic strength analysis is utilised for the purpose of calculating a parameter which is a measure of the material's strength, expressed in terms of maximum stress obtained due to the load on the shell. The strength is a decreasing function of the age of each specimen in the population. The rigidity of the material is evaluated and expressed in terms of the modulus of elasticity (Young's modulus). Results show that rigidity decreases with increasing shell diameter in such a way that it can be interpreted as an ageing effect, similar to the one noticed for the strength. Computer processing of the measurements shows good agreement of results observed for cysts in situ and for those chemically extracted, thus suggesting that the deformations in the latter have not been produced during preparation. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 6 van 17 gevonden artikelen
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