CHARACTERISTICS OF TYPES OF CONGLOMERATES 553 
In crush-conglomerates the shapes and sizes are variable, depending 
on the character of the rocks crushed, and on the character and 
amount of the deforming force. No doubt the pebbles would often 
be distorted and contain fracture planes and tension cracks. Glacial 
pebbles are characterized by variety in composition, size, and shape. 
Their sizes and shapes may, however, be so successfully imitated by 
bowlders and pebbles of fluviatile origin that it is only when the frag- 
ments are seen to bear the characteristic glacial striae, or to be inti- 
mately associated with stones that are so marked, that their glacial 
nature can be regarded as established. Even here caution is needed; 
for in landslides or mud flows, or by the action of shore- or river-ice, 
striated pebbles may be produced, which closely resemble those 
developed by glacial action. 
While the evidence shows that marine conglomerates are some- 
times ferruginous, the trend of opinion seems to be that such rocks 
are not, as a rule, highly colored. According to Russell, observations 
_show that lacustrine sediments are usually not red.*| The evidence 
found with reference to the color of estuarine deposits is insuffi- 
cient to make any general statement; they are, however, often con- 
sidered to have a tendency toward a red color. Some of the fluviatile 
deposits studied are shown to have highly colored or purplish zones. 
Strahan, speaking of the characteristics of continental formations, 
says they have a common tendency to a red color. Crush-conglom- 
erates, being induced as secondary structures in rocks already formed, 
partake of whatever color the parent rock may have possessed. 
Glacial conglomerates, as a rule, appear not to be highly colored, © 
though the Australian bowlder-beds are described as containing 
reddish-brown members. Red color is therefore not a distinctive 
characteristic of any particular type of conglomerate formation, but 
it may be said to be more common in the fluviatile and perhaps in the 
estuarine types than among the other kinds of conglomerate. 
Marine formations have been found to possess, on the whole, the 
most uniform bedding; while glacial formations exhibit the least 
developed and perhaps the most irregular stratification. Lacustrine 
and estuarine formations tend to resemble those of marine origin, 
U.S. Geological Survey, Bulletin No. 52, 1889, p. 47. 
~ 2 Quarterly Journal of the Geological Society, 1897, pp. 143, 144. 
