226 E. T. DUMBLE — GEOLOGY OF THE RIO GRANDE. 



of Eagle Pass. This is a fault with a downthrow toward the north of 

 about 60 feet. 



Half a mile below the bridge across Elm creek the following section 

 was observed : 



Section on Elm Creek. 



Feet. 



Sand 12 



< iravel 1 to 4 



X( idules of oxide of iron 5 to 1 



Sand 2 



Chocolate clays, with interbedded iron nodules 3 



Cross-bedded sandstone 1 



Blue clay 1 



Sandstone containing clay inclusions, some glauconite, and regularly stratified 



iron nodules 3 



( "lavs with very thin seam of coal 



Above the bridge a deposit of shaly sands occurs, containing ferru- 

 ginous sandstone seams which in -places pass into a lean iron ore and 

 form a stratum of eight to twenty inches in thickness. The sandstone 

 has a very shaly appearance on weathering. Overlying this there are 

 beds of laminated yellow clays, followed by darker beds with a very thin 

 scam of coal. 



Immediately above the laminated clays lies the stratum containing 

 cannon-ball concretions, which, with the overlying sands carrying great 

 quantities of silicified wood, form one of the most persistent and easily 

 recognizable horizons of the series. There are numerous excellent expo- 

 sures of the latter on Seco creek. 



Convent Hill Section. 



Feet, 



Gravel (Reynosa beds) 



Yellow clays and sands 30 



Calcareous nodules, highly ferruginous, imbedded in clay 1 to 2 



Bituminous shales with ',-inch seam of coal, to river 



Above these beds are found a series of brown or buff sandstones, semi- 

 indurated, calcareous, and containing fossil shells of Tnoceramus, Exogynt 

 ponderosa, etc. 



The entire section from these sandstones to the lower San Miguel 

 sandstones is shown in a general way in the following record of a boring 

 made for artesian water on the top of the hills just northeast of Eagle 

 Pass : 



