MANSFIELD: ROXBURY CONGLOMERATE. 143 
colored, dense, and arenaceous. ‘That iron coloration is wide-spread 
in marine accumulations is attested by the remarkable bed of “fossil 
ore” in the Clinton group, which extends from New York to Ala- 
bama, and by the reddish facies displayed by the Potsdam and 
Medina sandstones. These colors, however, are not ordinarily in- 
tense. In the rocks where the coloration is present it seems to 
reside in the matrix and is not described as encrusting or discoloring 
the pebbles. 
:—Fluviatile. The data at hand do not supply much evidence 
with relation to the color of fluviatile deposits. In the Siwalik deposits 
of India and in the New and Old Red Sandstone of England red colors 
are present. 
——:— Lacustrine. No evidence with reference to the color of 
lacustrine sediments has been noted above. Russell states (a, p. 47) 
that observations show that lacustrine sediments are usually not red. 
:—Estuarime. Regarding the color of estuarine conglomerates 
also no definite information is at hand. The Newark formation, which 
is believed by many to be of estuarine origin, is characterized by a deep 
red color in many of its members, but it may be questioned whether 
the formation is not fluviatile. 
——:— Glacial. Among the more recent glacial deposits the latest, 
unweathered, are generally dark bluish or greenish gray in color, 
while the older, more deeply weathered accumulations, are often 
highly ferruginous. Of the ancient glacial deposits above described, 
the majority are said to be dark bluish, greenish, or grayish in color, 
while some of those in Australia are said to contain reddish brown 
clay slates, passing downward into grayish brown mudstones. 
:— Crush. No data bearing on the color of crush conglomer- 
ates are available for this discussion. 
Bedding:— Marine. Marine accumulations in general possess a 
well-marked stratification, the beds grading upward from coarse to 
fine, where the deposits were laid by a transgressing sea, and passing 
horizontally seaward into younger and finer beds, as described by Hill. 
Variations in thickness and composition along the dip of the several 
beds are much greater than along the strike and all the beds are 
lens shaped in cross section, first thickening, then thinning seaward. 
Cross-stratification and irregular bedding are common among the 
conglomerates and sandstones, and sometimes these coarser beds are 
interstratified with finer materials in lenses which thin out or are 
replaced in their own horizon by deposits of different texture. Local 
unconformities may occur, as where interbedded marsh deposits are 
