262 
The American Geologist . 
April, 1896 
oxide as coloring matter in the rocks of the anthracite coal 
region. He said: 
A section of Lykens valley, for example, shows a thick stratum of 
red shale below the Carboniferous series. It is overlain by thin green 
sandstones, the color of which is due to another oxide of the same metal. 
Upon this rests the thick masses of the Pottsville conglomerate, a white 
quartzite which shows no coloration from iron, except perhaps a slight 
external tinge on the enclosed quartz pebbles. Above the conglomerate 
we find intercalated among the sandstones of the Coal Measures sixteen 
coal seams of varying thickness of which the lowest three show a red 
ash, several above them a white ash, while the upper three return to a 
red or pink ash. Above the Coal Measures there are no signs of iron 
coloration until, in other localities, the Trias is reached where we find 
the red coloring as pronounced as in the Subcarboniferous shales. 
These several strata cover a long period in geological history and 
exhibit the following phenomena :—During the red shale period the 
presence of iron oxide was sufficient to give a high color to the entire 
deposits. During the still longer period of the conglomerate the avail¬ 
able iron having been all distributed in the red shale did not appear at 
all, and the conglomerate beds show none. In the deposit of the three 
lowest seams a fresh supply of iron appears, enough to color their min¬ 
eral constituents red. Then ensued a long series of coal seams contain¬ 
ing little or no iron, to be followed by several red ash seams near the 
top of the series. There is then an entire absence of iron in sufficient 
quantity to color the rocks, until, in other localities, the Triassic period, 
when evidences of the universal distribution of iron oxide are more 
abundant than ever. 
These facts appear to show several points during which the accessible 
supply of iron was exhausted by complete distribution in the strata 
under process of deposit with intermediate and subsequent periods dur¬ 
ing which new supplies appear from some source not yet clearly explained. 
Prof. A. P. Brown continued the discussion and said: 
It has been suggested by Russell that the red color of certain forma¬ 
tions may have originated from the subaerial decay of iron-bearing 
rocks and the subsequent deposit of this material as sediment, forming 
the red rock. Such rocks as contain iron, especially limestone and the 
metamorphic schists, would weather in the atmosphere to reddish clays 
and during periods when denudation of the surface was not active, or 
when the land remained at constant level such weathered accumula¬ 
tions could form to considerable depths. A rise of land level would 
cause denudation of this accumulated red soil and result in its deposit 
elsewhere. The periods preceding the formation of the Mauch Chunk 
red shales and the New Red or Trias were such periods of quiescence 
and they were followed in the first case locally, and in the second gen¬ 
erally, by elevation of land, causing denudation to be set up and accu¬ 
mulation of red clays to be formed. 
As far as the ash of coal is concerned, it is probable that the color is 
due to the way in which pyrite is contained, either in the coal itself or 
in the slates adjoining. Coal containing separable pyrite would give 
white ash, while if the pyrite is intimately mixed in the coal the ash 
will be red. 
The subject was further discussed, by Messrs. Heilprin, 
Willcox, Goldsmith and Lyman. 
A communication was read from Dr. Persifor Frazer re¬ 
garding certain supposed new trap dykes in Chester county, 
Pennsylvania, described before the Academy by Mr. Theo. D. 
Rand. 
