Physical properties of Vendian to Devonian sedimentary rocks in Estonia
Titel:
Physical properties of Vendian to Devonian sedimentary rocks in Estonia
Auteur:
Joeleht, Argo Kukkonen, Ilmo T.
Verschenen in:
GFF
Paginering:
Jaargang 124 (2002) nr. 2 pagina's 65-72
Jaar:
2002-06-01
Inhoud:
Measurements of petrophysical properties of sedimentary rocks in Estonia are reported. We measured 364 samples in order to find out how the rock properties vary between and within the rock types, and which factors control these rock properties. The sampled boreholes cover different strata ranging from Vendian to Devonian in age, and represent Estonia laterally as well. Lithologically the analysed samples mainly represent carbonate rocks (limestone, dolomite, marl), but terrigeneous rocks (sandstone, siltstone, claystone) were also measured. Within the rock group, porosity is the main factor controlling thermal conductivity, saturated density, P-wave velocity and electric resistivity. From the point of view of rock properties, limestone and marl exhibit a homologous line where they represent low and high porosity fields, respectively, and thus could be treated together. The same applies for dolomite and dolomitic marl. P-wave velocity shows slight anisotropy, being in lateral direction 6-11% higher than in vertical direction, whereas electric resistivity shows no systematic change. The lateral variations of the rock properties for the same stratigraphic unit in Estonia are mainly due to lithological changes. As a rule, increase of the clay content in a rock increases porosity, susceptibility and natural remanent magnetization (NRM). All studied sedimentary rocks are paramagnetic with low NRM.
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