292 Geologic Story of the Colorado River. — Hill. 
ado basin and forms the resistance causing the great bend of the 
river in the south-west corner of Burnet county, the river 
flowing around its western and southern borders. The 
Cretaceous sediments once covered all this paleozoic area. 
At many points, as in the town of Burnet, where the stratified 
rocks have not been removed, the presence of the granite is 
apparent from the undulatory folds accompanied by intense 
metamorphism and crystallization of the limestone. It is 
from these contacts that the rare mineral crystals of the region 
are collected. 
THE EARLY MESOZOIC HIATUS. 
The extent of this post paleozoic disturbance seen in the 
excavation of the Colorado river is obscured in most parts of 
Texas, as will be shown later, by the sediments of the great 
subsidence in early Cretaceous times, but there is no doubt 
that it was connected with the extensive orographic move- 
ment (as illustrated by somewhat different phenomena) of 
the Ouachita system of Arkansas and Indian Territory. It is 
also apparent from evidence which cannot be quoted here, 
that this disturbance outlined the axis which at intervals 
separated during Permian, Triassic and Jurassic times the 
interior basins of the west from the Atlantic shore line. 
The record shows, as far as such evidence is reliable, that 
the eastern slope of this disturbed area remained above water 
during early mesozoic time until the beginning of the 
great lower Cretaceous subsidence. Whether it was a part of 
the post-paleozoic continent whose southern border is so 
sharply defined through south-western Arkansas and southern 
Indian Territory which has not been submerged since, is an- 
other question. There is evidence that this Texas paleozoic 
area,if not an island entirely cut ofi" from the Arkansas-Indian 
Territory system, was a very long and narrow peninsula. 
THE CRETACEOUS HISTORY.' 
The section shows between 3,000 and 4,000 feet of Cretaceous 
sediments, including the oldest and the latest known horizons 
in this country. 
These sediments belong to two entirely distinct formations 
of about equal thickness, separated by complete sedimentary 
and faunal unconformity. In fact the differentation is so 
'See Am. Jour, of Science, April 1889, pp. 282-297. 
