THE 



SOUTHERN BORDER 



OF THE 



CENTRAL COAL FIELD 



W. F. CUMMINS. 



The exploration upon which this report is based extended over parts of 

 Lampasas, San Saba, Coleman, McCulloch, Concho, and Tom Green counties. 

 The object of the trip was to secure such general information regarding the 

 section as would indicate the special lines of work that could be most advan- 

 tageously pursued in the detailed survey of this region. 



DESCRIPTIVE GEOLOGY. 



During the present expedition strata belonging to the Silurian, Carbonif- 

 erous, Cretaceous, and Recent systems have been observed, some of which 

 will be more fully mentioned under separate headings, but their boundaries 

 must be left for more detailed work. 



The different formations have been identified either by their fossils or by 

 their relative positions in regard to other known strata. There is great uni- 

 formity of structure in the individual strata of the several formations over the 

 entire field ; so much so that one becoming familiar with the characteristics of 

 a stratum in one place need have little trouble in recognizing it elsewhere 

 when found. 



The strata of the Paleozoic Group as observed along the route have a gen- 

 eral and uniform dip to the north and northwest, with little or no disturbance, 

 except in one or two instances which are noted. The Mesozoic strata, on the 

 contrary, have a general inclination to the southeast. 



Few evidences of faults or folds of the strata in any of the formations were 

 seen, except where they are in contact with the eruptive rocks. The alterna- 

 tions of limestone, sandstone, and shales in the various formations show that 

 the periods of their deposition were attended with alternating conditions of 

 subsidence and elevation. 



CRETACEOUS SYSTEM. 



The rocks of the Cretaceous system are found in contact with strata of both 



the Carboniferous and Silurian, showing that the Silurian and Carboniferous 

 j 



