Clay content of a clayey diatomite, the Early Eocene Fur Formation, Denmark

Gunver Krarup Pedersen, Stig A. Schack Pedersen, Jacob Steffensen, Christian Schack Pedersen

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21 Citations (Scopus)


The Early Eocene Fur Formation is a clayey diatomite interbedded with layers of volcanic ash. The diatomite is non-calcareous, laminated or structureless, and thin sections show that the proportion of clay-sized particles to diatom frustules varies between laminae. The clay mineral phase has been isolated and its chemical composition has been determined by X-ray fluorescence (XRF). Clay mineralogical analyses based on X-ray diffraction (XRD) show that the dominant phase is smectite. A general formula for the clay mineral phase is: X 0.1K 0.2(Mg 0.3Fe(III) 0.3-0.7Al 1.1-1.4)Si 4O 10(OH) 2. The investigation indicates that the clayey diatomite of the Fur Formation comprises three components: diatom frustules, clay minerals and volcanic dust. The chemical compositions of bulk samples have been determined. The clay mineral content is calculated to be 30-45% (by weight). Volcanic dust constitutes c. 10% of the diatomite, and the rest is diatoms (opal-A). The diatom frustules contain some Al 2O 3 that is either of primary or diagenetic origin.

Original languageEnglish
Pages (from-to)159-177
Number of pages19
JournalBulletin of the Geological Society of Denmark
Issue number2
Publication statusPublished - 15 Dec 2004


  • Chemical composition
  • Clay minerals
  • Denmark
  • Diatomite
  • Early Eocene
  • Fur Formation

Programme Area

  • Programme Area 4: Mineral Resources


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