FORMATIONS IN SOUTHEASTERN IOWA. 303 
layers of granular limestone, however, one or more thin beds of 
a purer, fine and compact limestone occur which are especially 
valuable for the manufacture of lime. The granular limestones 
are well exposed at Graner’s quarry (p. 295) and elsewhere. At 
Belfast they are seen resting upon the compact limestones, the 
whole constituting a thickness of twenty-two feet. This formation 
is sometimes found in small lenticular patches in the brecciated 
limestone, and in some cases a limited development of true odlitic 
limestone occurs under similar conditions, but it is not common. 
Brecciated limestone.—This constitutes the most generally 
recognized phase of the Saint Louis group in Iowa. Usually it 
consists of ten to twenty feet of limestone breccia or conglom- 
erate in which the fragments are of the compact variety noted 
above, more or less completely cemented by similar calcareous 
material. In its maximum development it is from 50 to 75 feet 
thick, the brecciated character in these cases evidently involving 
all of the preceding formations to the base of the Saint Louis 
group. In these exposures, as, for example, near the mouth of 
Reed’s Creek in Van Buren county, at Croton, and elsewhere, 
the lower portion is seen to consist of coarse fragments of the 
arenaceo-magnesian limestones, and their related sandstones, 
loosely piled together, and the interstices filled with green clay. 
The whole takes on a rude stratification, while somewhat persist- 
ent but decidedly undulating beds occur at irregular intervals. 
Upwards the breccia becomes more compact and firmly cemented, 
and is composed chiefly of the compact white or gray limestones 
sometimes including the granular type. Away from these areas 
of greatest disturbance, the lower portion is soon replaced by 
undisturbed strata of the brown Lithostrotion formation while 
over this the lighter colored, more compact breccia extends 
itself in varying thickness. It fails entirely in places, as already 
noted, and its place is occupied by the compact gray limestones 
in undisturbed beds. These limestones differ from those which 
elsewhere rest zpon the brecciated formation in being of a some- 
what darker shade. The fragments of limestone composing the 
breccia are frequently waterworn, but the wearing has seldom 
