PSEUDOBRECCIATION IN ORDOVICIAN LIMESTONES 409 
brecciated structure due to the cementation of a dolomite breccia 
in a calcareous matrix, is evident from the microscopical examina- 
Fic. 5.—Thin section, showing margin between dolomitized (left) and undolo- 
mitized (right) limestone. 3. 
tion. In several thin sections there are found at the margins of the 
dolomitized areas fossils which have been surrounded by a thin 
