270 CENTRAL MINERAL REGION OF TEXAS. 



since its elevation at the close of the Fernandan Period. All the later shore 

 lines, so far as they can be presumably traced, confirm this opinion. 



There is at first view less difficulty in arranging a suitable classification of 

 the included rocks than of those belonging to the underlying system. The 

 chance that a part or all of the Burnetan rocks may have been eruptive is 

 not as strong an obstacle in the case of the Fernandan Beds ; for if we except 

 the intrusive and extrusive igneous masses, and possibly some uncertain basal 

 members, there is hardly a doubt of the aqueous origin of the greater por- 

 tion of these strata. But metamorphism has introduced a new difficulty. 

 Many of the schists, which for good structural reasons may be included 

 in this system near its base, have such a close resemblance to some of the 

 Burnetan rocks that nothing but a close observation of many exposures will 

 enable one to properly separate them. A few illustrations will make this 

 statement more clear. 



SECTION A. 



About three-quarters of a mile below Lone Grove, on the right bank of 

 Little Llano Creek, where the section is badly complicated by other strikes, 

 there is a succession like the following: 



Principal dip, nearly vertical, north 54 degrees east; strike, north 36 degrees 

 west. 



1. White saccharoidal rocks with very little muscovite; chiefly saccharite (andesite, var.) 



2. Quartz and black mica schist, underlaid by 



3. Dense ferruginous hornblende? schist. 



4. Granite masses, with engulfed fragments of black mica schist and other rocks. 



5. Slabby, dense, mottled, biotitic gneiss, apparently overlaid, on dip of south 54 degrees 

 west, by 



6. Granular quartz rock, ferruginous, 50 feet. 



7. Loosely aggregated crystalline dolomitic marble. 



8. Similar to 7, less altered. 



9. Similar blue-gray marble, tough. 



10. Black mica schist parting of ten inches. 



11. A kind of porous chalky ferro-calcite, apparently burned by igneous intrusions. 



12. Very fine grained, ferruginated, black mica schist, with granite inclusions (G=3.133); 

 25 inches thick. 



13. Altered oligoclase? granite. 



14. Contorted hard gray marble. 



15. Bluish and white albite, much broken by joints. 



And so on, with felsitic and calcareous strata, badly broken by cross 

 strikes of Post-Fernandan uplifts. 



SECTION B. 



Between the Little Llano, near its head, and Arrott's Branch, and farther 



