730 TRANS-PECOS TEXAS. 



The calcareous sand at the base of the Quitman bed forms the cap rock of 

 Yucca and Bluff mesas. The fullest exposure is along the crest of Quitman 

 Mountains southward from Quitman Pass. It occurs also passing through 

 the southwest side Camp Mesa and in the hill one mile southwest of Bluff 

 Mesa. 



The oblong oyster that occurs in the sand at the base of this bed appears 

 in the calcareous sand overlying the Orbitolina horizon in the hill one-fourth 

 of a mile northwest of Eagle Spring. At Mica Water Hole, fifteen miles 

 southeast of Torbert Station, the same oyster occurs associated with Area in 

 similar calcareous sand overlying Carboniferous limestone. It is found also 

 in fragments in the small buttes one mile northeast of Eagle Flat Station. 



MOUNTAIN BED. 



The final Caprotina horizon is succeeded by a great development of oyster 

 shell siliceous limestone, calcareous sandstone, and quartzitic and flaggy mar- 

 ble in conformable horizons, in all four thousand feet thick, forming the most 

 extensive series of rocks yet observed. It was not possible at the time these 

 rocks were examined to make an exhaustive study of them, but during the 

 time they were worked no evidence was found that would give a positive de- 

 cision upon the exact division to which they belonged. The Mountain bed 

 succeeds that of Quitman in regular conformity of dips and strikes, and the 

 rocks are not materially different lithologically from much of the sandstones, 

 limestones, and breccias of the underlying beds. The series of horizons of « 

 the Mountain bed are divided, with their section, as follows: 



I. FINAL ALTERNATING HORIZON. 



1. Calcareous sandstone 20 feet. 



2. Concealed , 100 feet. 



3. Pale yellow compact limestone 30 feet. 



II. UPPER QUARTZITIC SAND. 



1. Red, brown, and gray quartzitic sandstone 280 feet. 



III. UPPER ALTERNATING HORIZON. 



1. Very yellow to bright reddish-yellow fine-grained limestone 5 feet. 



2. Quartzitic sandstone 15 feet. 



3. Very yellow limestone, conglomerate 15 feet. 



4. Brown quartzitic sandstone 60 feet. 



5. Pale yellow compact limestone 10 feet. 



6. Brown quartzitic sandstone 50 feet. 



7. Yellow flaggy limestone or marble 10 feet. 



