2 
Transactions Texas Academy of Science. 
[ 104 ] 
-The formations observed then or later to overlie there were: 
(a) A series of brown sands and grits with conglomerates which were 
referred to the Potsdam. The pebbles of these beds include quartz and 
other siliceous material, red basaltic rocks, red sandstone (resembling 
that under discussion), and fragments of material resembling silicified 
wood such as was found on the west slope of Eagle Flat mountain and 
identified by Dr. Osann as belonging to the quartz porphyries. Their 
character is well shown, on plate number XXIV of the Second Annual 
Eeport. Toward the top, these brown sands and grits gradually change 
their color to gray and become finer grained, the pebbles being chiefly of 
quartz. Still higher, the increasing fineness of the grain gives beds of 
gray and yellow sandstone full of worm borings. This is the horizon 
from which specimens were sent to Mr. Walcott by Prof. Streeruwitz, 
and the borings were identified' by him as those of Scolithes linearis. 
The culminating beds are flaggy. 
(b) Above these beds, and possibly separated from them by another 
sandy bed, are the limestones of the Silurian; and these are followed by 
the deposits of the Carboniferous. The reference of these beds to the 
Silurian and Carboniferous is based upon the fossils found in them by 
the different explorers of the Boundary . Survey, the Pacific Railroad 
Survey, and W. P. J enny, and, later, by ourselves in the various moun- 
tain ranges of the region. The Carboniferous fossils are abundant at 
■Certain horizons of the beds referred to that age, but those of the Silurian 
are not so plentiful. Enough can be found, however, to determine the 
age. 
In the vicinity of the Hazel mine we have all of these horizons repre- 
sented. In the mountains lying to the southeast of the camp a long 
. scarp shows a body of Silurian limestone underlain by the Potsdam, 
which in turn rests unconformably on the Hazel sandstone. Following 
the scarp westward to the : vicinity of the Black Gulch mine, we find a 
strong fault with a northeast-southwest strike, which brings into view 
the Texan marbles resting directly upon the Hazel sandstone. This con- 
dition continues toward the west until the summit of the ridge is reached, 
when the Texan marbles or dolomites are overlain by the Potsdam and 
this by the Silurian. Across the ridge, the exposures show the Texan 
group resting on the Hazel sandstone and capped by a dark brown sand- 
stone, highly ferruginous, and different from the Potsdam beds. This 
is followed by a bed of reddish brown basaltic material. This basaltic 
material is also found in connection with the deposits of copper in vari- 
ous localities, and appears to b6 closely related to them. The marbles 
are here underlain by shales and schistose materials containing a dike of 
the red igneous rock. 
The exposures at Tumbledown mountain, which lies south of the Hazel 
mine, give practically the same section as the lower portion of the hills 
