Vol. V] DUMBLE— TERTIARY DEPOSITS IN NORTHEASTERN MEXICO J73 



Papagallos shales which are supposed to underhe the Escon- 

 dido, thus indicating an unconformable overlap. 



Amole Creek flows in a long narrow valley in which the 

 Amole Ranch is located. After crossing the creek west of 

 Perros Bravos the country for several miles to the west is 

 covered with the Reynosa, but after passing this, the road 

 crosses a series of small benches made up of thinly bedded 

 yellowish sandstones weathering brown and carrying frag- 

 ments of oysters. Just west of Amole we found a contact be- 

 tween shaly brown sandstone with abundant Ostrea cortex 

 Con. and a somewhat similar sand with Ostrea pulaskensis 

 Har. This later sand is overlain in the neighborhood of the 

 Cuevas Ranch by grayish yellow sandy clay and this in turn 

 by the Carrizo sand, which to the south becomes the most 

 prominent member of the Tertiary, overlapping in many 

 places both the Lignitic and Midway to a contact with the 

 Cretaceous. The Cretaceous (Escondido) sandstones noted 

 west of Amole also appear along the western side of the 

 Ceja del Macha and as far south as the Pescado Ranch, un- 

 derlying a dark brown clay carrying boulders and containing 

 broken and worn fragments of Ostrea cortex, which we refer 

 to the Midway. South of the Pescado Ranch we find a 

 large area covered by the deposits of the Reynosa and an 

 old lake bottom, beyond which the first recognizable Cre- 

 taceous was encountered in the San Antonio hills. These 

 hills on the eastern side of the Salado River appear to be 

 made up principally of the yellow clays of the Escondido 

 with a plating of gravel. 



The Salado River flows in a narrow valley, lying between 

 the San Antonio and San Juan hills, and the sections made 

 here gave us the relations of the various members of the 

 Cretaceous, which are found in contact with the Tertiary. 

 On the west side of the Salado, the San Juan Hills are 

 made up of a series of thin to heavy bedded limestones 

 interstratified with thin beds of yellowish clay. This is the 

 type locality of the San Juan beds. Towards the base the 

 limestones are shaly, dark gray in color, and weather gray 

 to whitish. Toward the summit the limestones are of a 

 bluish shade, weathering white. The uppermost beds are 

 sandy and weather to a reddish or rusty brown color. They 



