They formed in residuum derived from soft, calcareous shale (marl) and from some thinly interbedded limestone.
(They; formed; L:in residuum) (residuum; derived; from soft, calcareous shale (marl) and from some thinly interbedded limestone)
They residuum
formed derived
L:in residuum
from soft, calcareous shale (marl) and from some thinly interbedded limestone