PALEOZOIC GROUP. 285 



1. At least two and probably three series of Cambrian strata are repre- 

 sented in Central Texas. 



2. The character of the beds and their great thickness indicate gradual 

 subsidence. 



3. The tendency to folding along meridianal lines, which began at the 

 close of the Texan period, continued during much of the Cambrian period. 



(1.) HICKORY SERIES (LOWER CAMBRIAN?). 



Wherever I have seen good contacts of the Cambrian with the Texan 

 strata, and in many places where the granites directly underlie the Cambrian, 

 there is a set of beds which differ from the typical Potsdam sandstone. In 

 every case in our region in which the upper contact of the terrane can be 

 determined, there is an unconformity, although this is not always detected 

 by casual observation. In most exposures the whole Cambrian System has 

 been involved in Post-Cambrian uplifts, and this fact has caused previous 

 observers to overlook the Inter- Cambrian minor unconformities. Probably the 

 best outcrops of the lowest member of the series are those in the neighbor- 

 hood of House Mountain, in the valleys of Hickory Creek and its tributaries, 

 but there are also instructive exposures of higher beds in many other places, 

 as at the summits of Smoothing Iron, Fox, Town, Sandstone, Sharp, Pack- 

 saddle, Sandy, Lockhart, and other peaks or elevated tables in Llano County. 

 Besides these, there are patches in portions of Mason County, south of Fly 

 Gap, between Mason City and the Llano River, and on Katemcy and Ranch 

 creeks in the northern part. The last named exposures extend more or less 

 into McCulloch County. An outcrop of the lowest conglomerate also occurs 

 in Burnet County, about four miles from Burnet on the road to Bluffton, on a 

 branch of Spring Creek, and what appear to be sandstones of the Hickory 

 Series are well displayed at Cottonwood Spring, south of the same road, two 

 miles farther west. The rocks begin at the base of the series with a coarse 

 conglomerate absent from some of the sections, and they somewhat gradually 

 change above to pebbly sandrock of medium fineness, with much local modi- 

 fication. In most cases false bedding and rapid variegation in color and 

 lamination afford abundant evidence of littoral deposition. The basal con- 

 glomerate especially exhibits marked traces of in-shore beach accumulation 

 from the degradation of the local subjacent rocks, and this feature gradually 

 disappears in the higher strata, which have more the character of off-shore 

 deposits made in shallow water. Some of the highest beds have the texture 

 resulting from deposition in deeper water, regularly agitated. One very 

 characteristic and persistent division is a massive white to buff fine pebbly 

 sandstone near the top of the series, which is almost a quartzite, and which 

 might be supposed to be burnt by igneous contact, if judged from some of 



