"Mark Godden's Little Bit Of Cyberspace Mk.II"

A "shelly" Portland whitbed, (typically from upper half of face).

A "clean" Portland whitbed, (typically from lower half of face).

Whitbed tends to be a more shelly stone than basebed. The higher shell content makes it very durable and ideally suited for use as a general building stone. The younger whitbed (from the upper part of the whitbed quarry face) tends to contain ubundant oyster shell fragments and the calcareous algae Solenopora. The older (lower) whitbed tends to contain significantly less large shell fragments. The whitbed is overlain by the roach, the two beds are not normally separated by a distinct junction or bedding plain, but the shelly" upper" whitbed tends to grade into the even more shelly roach. It is believed that the trend throughout the period that the Portland freestone was being laid down, was towards a shallowing of the overlying sea water. This could help to explain the observed trend of a decrease in shell content (and hence sea floor life) with age.