Effects of burial on the clay assemblages in the Triassic Skagerrak Formation, Denmark

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Sandstones and mudstones of the Skagerrak Formation from the Danish Sub-basin have been studied to assess the origin of the clay minerals, their diagenesis and their transformation/ conversion temperatures (compared to modelled maximum burial temperatures). Detrital smectite and vermiculite occur only at shallow levels. Conversion of smectite into random S-I took place at >47°C and of random S-I into ordered I-S at >74°C. The omnipresent illite increases in amount with burial. The amount of authigenic kaolinite (kaolin) decreases with increasing temperature (>75°C), possibly due to the growth of chlorite. Random S-C is converted into ordered S-C between 70°C and 105°C and chlorite is most abundant at maximum burial temperatures (150°C). This investigation suggests that diagenesis of clay minerals begins at relatively low temperatures, and emphasizes the importance of the availability of necessary ions (K+, Mg2+, Fe2+) for the reactions, besides time and temperature, as controlling parameters.

Sider (fra-til)619-635
Antal sider17
TidsskriftClay Minerals
Udgave nummer4
StatusUdgivet - dec. 1999
Udgivet eksterntJa


  • Clay minerals
  • X-ray diffraction
  • Petrography
  • Sandstone
  • Burial depth
  • Triassic


  • Programområde 3: Energiressourcer


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