Fig. 8.9. (Upper) Carbonate concretion in Kimmeridge Clay (Upper Jurassic) Burning Cliffs, Dorset. Note
the way in which clay laminae converge away from the concretion, thus demonstrating that it formed as a result of localized cementation during shallow burial, prior to compaction. (Lower) Septarian nodule from the
Lias (Lower Jurassic), Charmouth, Dorset. This concretion developed shrinkage cracks that were then infilled
by calcite. In both cases the concretions contain complete fossils, while flattened shells occur in adjacent
shales. This is further evidence for early precompaction cementation.
the way in which clay laminae converge away from the concretion, thus demonstrating that it formed as a result of localized cementation during shallow burial, prior to compaction. (Lower) Septarian nodule from the
Lias (Lower Jurassic), Charmouth, Dorset. This concretion developed shrinkage cracks that were then infilled
by calcite. In both cases the concretions contain complete fossils, while flattened shells occur in adjacent
shales. This is further evidence for early precompaction cementation.