Ixiv REPORT OF THE STATE GEOLOGIST. 



ately preceding the Carboniferous, either existed only in limited areas 

 or has been almost entirely destroyed by erosion. 



It has been stated that the character of the deposits found along the 

 eastern and southern borders of the Central Paleozoic Region is such as 

 to almost necessitate the existence of a shore line from Red River to the 

 Colorado and west to the Rio Grande — possibly in some such locality 

 as the present western and northern border of the scarp of the Grand 

 Prairie plateau. 



From this shore line of the great land area which existed to the east 

 and south a sea stretched out towards the west and north. 



The present outcrops of this interior sea appear east of the Pecos in 

 a series of beds whose boundaries have a general northeast-southwest 

 course, and as we go northwest or across the strike of the formations we 

 gradually rise both topographically and geologically. The beds are al- 

 ternations of sands, sandstones, clays, limestone, and shales, with coal and 

 gypsum ; and this alternation of strata of hard and soft materials gives 

 us a rolling country of great beauty. The ascent to the north and west 

 is not a gradual slope, but rather a series of steps. This is due to the 

 harder layers of rock material which occur scattered through the softer 

 material. The steep side, or bluff as it often shows in places, is com- 

 monly towards the south and east, while the gentle slope is more nearly 

 in the direction of the dip. Exceptions to this are, however, numerous, 

 caused by the various drainage channels of creeks and by other local 

 conditions. The capping of the Cretaceous rocks which also exist in 

 parts of this region aids in bringing about other changes in the general 

 topography. The whole region is one of great erosion, and until this 

 shall have been studied and properly understood we will be unable to 

 fully appreciate all of the features which its present topography force 

 upon us. To the west of the Pecos the rise is very rapid, and the un- 

 derlying Paleozoic rocks are covered in most places by the Cretaceous 

 until we reach the southern continuation of the Guadalupe Mountains 

 at Van Horn, where the Carboniferous rocks are again brought to view. 



In this great interior sea were laid down not only those sediments 

 which now constitute the Sub-Carboniferous and Carboniferous, but 

 also the Permian, and it may be the Jura-Trias strata — or, in short, all 

 those previous to (and possibly even after) the beginning of the Creta- 

 ceous period. These various sediments show little signs of disturbance 

 other than the deepening or shallowing of the bed of the sea itself, save 

 just along the ancient shore line, and are usually of a very gentle dip. 



