OLDER CRETACEOUS DEPOSITS. 221 



is capped by gravel. Toward the south and east rises a scarp composed 

 of the same Arietina clays and Nodosaria shales. 



The deposits of ochre which have been reported from this district 

 occur in these Arietina clays in the form of segregations of ferruginous 

 matter in bodies of considerable size but somewhat variable quality. 



The clays and shales of the scarp are capped by a fine grained sub- 

 crystalline limestone of creamy white color, semi-conchoidal fracture, 

 and containing many small reddish spots. This limestone is litho- 

 logically and stratigraphically equivalent to the Vola limestone of the 

 Colorado section, and although no fossils have been found, it is referred 

 to that horizon on these grounds alone. It is the highest bed of the 

 lower Cretaceous in this locality. 



UPPER CRETACEOUS. 



The Vol Verde Flags. — The lower Cretaceous materials continue to a 

 point 2$ miles south of Del Rio, where the Vola limestone is overlain 

 by a softer flaggy limestone. The contact observed in this locality 

 was so small in area and so covered that no conclusion could be reached 

 regarding the conformity of the two beds. Where it has been observed 

 in other localities it shows little, if any, unconformity. The lime flags 

 can be followed to Sacatosa creek, 6 miles southeast of Del Rio, where 

 they are well developed. They are grayish-white in color, laminated to 

 flaggy in structure, and separated into bands by laminated clays. The 

 lower strata contain considerable bituminous matter and the remains of 

 fishes. The higher beds of this locality are also sufficiently bituminous 

 to give off a fetid odor when struck with a hammer. The principal 

 fossil here is TnoceramibS, "the species of which have not yet been de- 

 termined. These flags can be followed from this locality down Saca- 

 tosa (?) creek to the Rio Grande, and down the Rio Grande to Syca- 

 more creek, forming a bluff 25 to 75 feet in height along the river the 

 entire distance, so that we have an exposure some six miles in length 

 alonir the line of section, with a dip apparently not less than 100 feet to 

 the mile. 



These Mull's are in Y;il Verde county, and for that reason I have 

 named the flags the Vol Verde Jim/*. They are tolerably uniform in 

 structure from base to top, the principal variation being in thickness. 

 In places they are shalv. but are COmmOnly flags of various thicknesses, 

 frequently showing on a transverse surface alternate parallel lamina' of 

 white and yellow. Their weathered surfaces are from Light yellow to 

 reddish, and in some places beds of deeper yellow or even orange hue are 

 found. Modci-atc amounts of oxide of iron occur, and at one place a 

 quantity of calcite was observed crystallized similarly to that which L 



