110 GUIDEBOOK OF THE WESTERN UNITED STATES 
sediments. The old basement of schist and granite of pre-Cambrian 
time appears in the Van Horn and El Paso regions, where in places it 
is overlain by sandstone and limestone probably of Algonkian age. 
The relation of land and sea and the extent to which Algonkian de- 
posits were laid down can be only vaguely pictured. Late in Cambrian 
time there was extensive marine submergence, with shores on which 
accumulated the sand of the Bliss and Van Horn sandstones. In the 
next period (Ordovician) there were widespread marine conditions 
from time to time, separated by intervals of general uplift in which 
doubtless some deposits were removed by erosion. This oscillation 
of submergence and emergence continued through the Paleozoic era, 
but representatives of part of the Silurian, Devonian, Mississippian, 
and Pennsylvanian are all indicative of widespread marine seas, most 
of the shores of which can not be located. In these times the uplifts 
were general and in greater part not attended by flexing until late 
° 2 Miles 
See Eo 8 3 j = 
Vertical scale 
° 1000 Feet 
| ee Se See See Re 
FicuRE 21.—Section across the western part of the Wylie Mountains 
north of Lobo siding, Tex. Cp, Permian limestone; €vh, Van Horn 
sandstone (Cambrian) 
more. In places the deposition was long continued, subsidence keep- 
ee algae, bryo- 
Sponges, crinoids, and other fossils of reef habitat. Behind 
ere wide lagoons in which thinly stratified beds were laid 
