462 A. W. GRABAU PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



Feet 

 (Contact generally abrupt; sometimes a few inches of shale inter- 

 vene. ) 



0>. Medina red sandstones. Massive sandstone in beds from one to 

 several feet in thickness and varying in color from reddish to 

 grayish. Irregular cross-bedding generally well shown, together 

 with local cut and fill phenomena, the wedging out of beds, etcetera. 

 A few fossils are found in the lower, more regular beds, especially 

 Lingula cuneata, while Arthrophycus harlani is restricted in this 

 section to the under side of this division, projecting downward 

 into underlying shales 12 to 15 



5. Medina variegated sandstones and shales. Compact, solid, reddish or 

 gray sandstone, mottled with red, in beds from 4 to 6 inches thick, 

 separated by shaly partings with occasional beds of red shale 2 to 4 

 feet thick. About 20 feet above the base of this series is a concre- 

 tionary layer from one to two feet thick, which appears not unlike 

 a bed of large rounded bowlders. These concretions vary in 

 diameter up to 3 or 4 feet, and they lie in close juxtaposition, not 

 infrequently piled one upon another. Thinning out of layers in all 

 directions is a common phenomenon, and ripple marks are fre- 

 quently met with on the sand beds, one of the layers 10 feet above 

 the base showing ripples with their crests 1 to 1% feet apart. 

 Fossils are more common in these layers, the following having been 

 obtained : Lingula cuneata, Whitfteldella oUata, Modiolopsis ortlw- 

 nota, M. primigenia, and fragments of others 35 to 40 



4. Gray and greenish gray Medina shales, intercalated toward the top 



with reddish bands and finally changing to red altogether 6 



3. Gray Medina sandstone. Porous and calcareous sandstone and sandy 

 shales, some of the former massive and in beds 6 or 7 inches thick 

 separated by shaly layers. Fragments of fossils are common and 

 often appear to have been dissolved out. Many of the thinner beds 

 have ridges on their under side, the filling of grooves or trails in 

 mud below. Small black phosphate pebbles or nodules, often very 

 smooth, are not uncommon in some of the layers, suggesting small 

 worn fragments of fish bones. Larger pebbles of carbonaceous 

 shales are also found occasionally. The fossils are mostly Gastro- 

 pods and pelecypods, but some thin layers are covered with poorly 

 preserved fragments of what seems to be the Bryozoan Helopora 

 fragilis. Other fossils found here are: Camarotoecjiia sp., Uncin- 

 ulus stricklandi, Plectorthis medinaensis, Rhipidomella sp., Pent- 

 amerus sp., Modiolopsis orthonota, M. primigenia, Pterinea of. 

 emacerata, Pleiirotomaria parvetusta, P. Httorea, Orthoceras sp., 

 Ascidaspis sp., Dahnanites sp., etcetera 5 



2. Gray Medina shales. Fissile clay shales, gray in color and generally 

 free from sand, but with occasional sandy intercalations, and even 

 thin-bedded white quartzose sandstones near the center. Fossils 

 are scarce, Lingula cuneata being the most common. From being 

 coated by red mud these shales generally appear red in the cliff. . . 25 



1. Whirlpool quartzite 25 



Total Medina 120 to 130 



