Unit M25

image M25-02


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Cross sections through large ammonite shells on a bedding surface. The outer chambers of the shells are filled with the muddy limestone which also surrounds the shells. The inner chambers were not completely filled with sediment: later, the remaining spaces were filled with crystalline calcite (white), precipitated from solution. Look carefully at the sediment between the ammonites - it shows abundant evidence of burrowing.

  • What was the mode of life of ammonites?
  • What does the presence of ammonites tell us about the environment of deposition?

Scale: coin is 25mm across

Grid reference: 987 315

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