IN THE UPPER BIO GRANDE EMBAYMENT IN TE5CAS. 89 



7. N]i. survey B S & F survey 65. 



8. S^>, Miles Bonnet 7-i survey. 



9. South end Guadaloupe de los Santos survey. 



10. W. Owen's survey. 



11. Centre, Survey .56, block 6. 



12. SwYi, survey 57, block 6. 



13. Centre, survey 58, block 6. 



14. Nw^, survey 103, block 6. 



15. W%, survey 119, block 6. 



16. N;^, survey 93, block 6. 



17. S;^ survey 47, block 6. 



Dips to the west, northwest, or to the southwest were noted 

 as follows: 



1. Nu-;^, survey 225, block 7. 



2. Se'i, survey 18, block 6. 



3. Near S. line, purvey 22, block 6. 



4. Near X. line. Serena Goodman survey. 



5. W. line, Thomas Weeks survey (on Rio Grande). 



6. E. 51, survey 12, W. of Anton Handauer survey. 



It is clear that from the north end of this area of variable dip 

 there is a general descent of the beds to the south, probabh- equal 

 to some 30 feet to the mile. But there are minor folds which 

 frequently revenue this dip. The frequency of the horizontal atti- 

 tude on the west side of the stated line and no less the occasional 

 tilting to the west, clearh' show that the strata are affected by a 

 flexure, which has the form of an arch whose crest extends in a 

 north and south direction. But owing- to the general inclination 

 of the terranes to the southeast, the west limb of this arch is 

 slightlj' more raised in its position, as compared to the east limb 

 (see plate 3), 



The presence of the arch is clearly shown at its northern 

 extension in the southward detours made by lines indicating the 

 north limits to the three members of the Eagle Pass formation. 

 It also appears from these curves that the arch is more narrow 

 and pinched at its north end and wider and perhaps not as high 

 ' or as well defined at its south end. South of Mula creek, in the 

 Sauz pasture, it is lost in a general dip to the southeast which 

 again becomes the ruling structure. The highest dips referable 

 to this arch were seen on its east side as far north as the Salado 

 tank in the Salado pasture. Near the old Salado tank there is 

 an eastward dip of some five or six degrees and at a point south- 



