Petrographic examination and re-interpretation of concretionary carbonate horizons from the Kimmeridge Clay, Dorset

Sections through two concretionary carbonate horizons from the Kimmeridge Clay type locality in Dorset have been examined by back-scattered imaging EM, energy-dispersive X-ray and XRD techniques. One horizon has experienced a complex cementation history involving precipitation of several carbonate phases (low Mg, low Fe calcite and ferroan dolomite). The other horizon is compositionally and texturally homogeneous being cemented throughout by interlocking subhedral ferroan dolomite crystals.