78 
The American Oeologist. 
Feb. 1890 
The Balconcs fracture, extending from system to system at 
right angles to this resultant of general elevation, with its 
ancient volcanoes and faulting, is pregnant with sugges- 
tions of a long continued line of structural weakness, sub- 
tending ancient coastal plains, while the little known disturb- 
ances of the granite region, are sufficiently near it to suggest 
an ancestry and lineage of sedimentary disturbance along this 
line, more complete in its record than any other fracture in 
our land. 
Having now outlined the great plains and mountains of the 
Texas region, Part iii of this paper will be devoted to a study 
of its topographic history as interpreted in its ancient shore 
lines, subsidences and river systems. 
Epitome of the Chief Topographic Areas of the Texas Region. 
Explanatory of the accompanying map. See p. 9. 
I. Plains AND valleys 
IN PLAINS. 
A. Valleys of erosion. 
1. Terraces of the riv- 
ers of east Texas. 
2. Trans -Pecos Lake 
Basins. 
3. Great Valley of the 
Canadian. 
4. River Systems. 
(a) Rivers of the 
RioGrande-Arkan- 
sas System. 
(b) Rivers of the 
Red, Brazos and 
Colorado System. 
(c) Rivers of the 
Nueces, San Anto 
nio and Guadalupe 
System. 
(d) Rivers of the 
Coastal and Mis 
sissippi - lat eral 
System. 
Altitude. 
200 (above pres- 
ent fl o o d ■ 
plains.) 
2000. 
2000—3000. 
Character and Age 
OF Substructure. 
Transport ed up 
stream debris. 
Lacustral loam and 
debris. 
Alluvial calcareous 
debris or "Terra 
Blanca," deposited 
upon the Red Beds. 
Age of Topography. 
Post - Tertiary depos- 
its, the history un- 
solved. 
LatestQuaternary and 
recent: little studied. 
Great Basin epoch. 
Early Quaternary. 
Later than Staked 
Plains. Newer than 
present drainage. 
Grand canon epoch, 
or"MiddleTertiary" 
of Dutton. 
Antecedent to Staked 
Plains formation, or 
Pre-Tertiary. 
Subsequent to Staked 
Plains and Grand 
Plateau epochs. Ear- 
ly Quaternary?? 
Subsequent to Bal- 
cones epoch. 
Post-Tertiary and re- 
cent. 
