CHARACTERISTICS OF TYPES OF CONGLOMERATES © 551 
The data collected from these various sources were arranged in 
accordance with the following scheme: 
Matrix.—Kind of material; size of grains (coarse or fine, uniform or varied); 
shape of grains (angular, subangular, or rounded); arrangement of grains (orderly 
or disorderly, well stratified, rudely stratified, or unstratified); cement (argilla- 
ceous, siliceous, calcareous, or ferruginous). 
Pebbles.—Kind of material; size of pebbles (large or small, uniform or varied, 
gradation in any particular direction); markings (facets, polish, striation); 
deformation (distortion, tension cracks, fracture); arrangement (well stratified, 
rudely stratified, unstratified). 
Color.—General tone of the rock; relations to matrix; relations to pebbles. 
Characteristics of bedding.—Uniform series grading into finer beds, thickness 
and extent; variable series (lenses of coarser and finer materials, false-bedding 
and local unconformities, ripple-markings, sun-cracks, raindrop-impressions, or 
organic markings), thickness and extent. 
Relations to subjacent rocks —Conformable; nature of the underlying series; 
unconformable; eroded surface deeply disintegrated; eroded surface of relatively 
fresh rock unglaciated; eroded surface relatively fresh rock glaciated. 
The matrices of the various types of conglomerates have not been 
very fully described. According to Geikie the small particles of 
detritus are generally less well rounded than those of greater dimen- 
sions.!. Thisis doubtless true of all water-laid deposits. The evidence 
collected appears to show that the matrices of marine conglomerates 
tend to consist of clean sands fairly well sorted and often cross- 
stratified. Willis states of beach deposits that the “sand is clean and 
characterized by marked and irregular cross-bedding.”? Russell, 
referring to the incrustation of the grains in certain ferruginous 
deposits, remarks that if the débris had been deposited in the ocean 
and exposed to the action of waves and currents, the sands would 
have been more thoroughly assorted than we now find them, and also 
that the attrition produced by the waves under such circumstances 
would have scoured off the incrustation of ferric oxide. Dutton, too, 
emphasizes the more thoroughly assorted condition of marine sedi- 
ments as opposed to fluviatile deposits. Of the latter he states that 
material of all sorts is deposited everywhere, yet with a tendency to 
t Text-Book of Geology, 4th ed., Vol. I, p. 162. 
2 Journal of Geology, Vol. I (1893), p. 487- 
3U. S. Geological Survey, Bulletiny No. 52, 1889, p. 45. 
