EPARCH.EAX GROUP. 277 



ing the Llano Series, is not clearly exhibited. East of Packsaddle, especially 

 southward, outcrops are abundant. These he probably did not see. In the 

 only two cases reported by him these rocks were involved in the strike of an 

 uplift of much later date than the close of the Eparchsean Era. Mr. Wal- 

 cott himself obtained a hint of this, but his " hurried reconnoissance "did 

 not give him an opportunity to trace the connection between- this ''move- 

 ment," which he says " appears to have been at the close of the Paleozoic," and 

 the present position of the Texan Beds, where he observed them. 



In our field one must have considerable knowledge of the dynamic history 

 before he can determine how much to include in each group or system of 

 strata, and this statement is especially applicable to the older non-fossiliferous 

 rocks. The discovery of undoubted Texan beds unconformably beneath the 

 Potsdam does not necessarily imply that the former are occupying the position 

 they had before the deposition of the latter; and, as a matter of fact, there is 

 much unmistakable evidence that the Potsdam in Packsaddle Mountain was 

 not laid down upon the Texan Beds while they were elevated in an east-west 

 trend. 



The course of an uplift which has involved the strata of the Archaean and 

 Eparchsean groups, and no others, is the one which will give the true Texan 

 trend. This bears almost due north and south*, and it can be clearly made 

 out in parts of Llano and Mason counties. A portion of Packsaddle Moun- 

 tain east of Walcott's section lies in this strike. Southeast of Packsaddle 

 Mountain, especially in the neighborhood of Sandy Mountain, and northward 

 in the north-south course of the Llano River, there are good exposures of 

 this trend showing some of the characteristic Texan strata, including also a 

 portion of the underlying Fernandan System. The present eastern boundary 

 of the outcrops may, for good stratigraphic reasons, be assumed at a line 

 about in the general course of the Colorado River between Burnet and Llano 

 counties. No outcrop has been discovered east of the river. Evidences of 

 a shore line along this confine are visible, but much confused by more recent 

 dynamic events. The relative elevations of different exposures, the excessive 

 contortions, and other phenomena, all indicate much faulting; and there has 

 certainly been no more difficult problem in this field than the working out of 

 the Texan section, which is still but imperfectly accomplished. In Mason 

 County a broad belt of this orographic system is exposed, largely in the 

 drainage area of Comanche Creek north and south of Mason City. Some 

 very troublesome questions concerning the stratigraphy are as yet unsolved, 

 the search for fossils being heretofore unsuccessful and the effects of the up- 

 lift at the close of this period tending in places to mislead. There is a strong 



*North 10 degrees west, magnetic, 1889; average declination 9 degrees 15 minutes east; 

 corrected, north degrees 45 minutes west. 



