21 



different localities the upper limits of the lower group, and its connection 

 with No. 2 of the Cretaceous. First, near the mouth of Iowa Creek, on the 

 eastern side of the Missouri River, where the river cuts the bluffs, and where 

 the rocks are seen all in their order. 1 



4. Yellow marl, a recent deposit. 



3. Niobrara group, layers of white and yellow chalky lime, passing down 

 into gray marly rock. 



2. Black plastic clay with hard layers, containing Inoccramus, a species 

 of Ostrea, like O. congesta, remains of fishes, crystals of sulphuret of iron, 

 selenite, &c. 



1. Dakota group, sulphuret of iron, fragments of wood, impressions of 

 leaves, willow, laurel, &c. 



The second case of superposition of both formations is marked by Dr. 

 Hayden six miles above the mouth of the Big Sioux River, where the strata 

 are reported in the same order as in the former : 



3. Shaly limestone, gradually passing into the bed below, with an abund- 

 ance of Inoceramus problematic!/ s and of fish-remains. 



2. Dark plastic clay, with ferruginous concretions. 



1. a, Yellow friable sand ; b, earthy lignite, six inches ; c, variegated 

 sandstone and clays, with dicotyledonous leaves. 



In following the bluffs of the Missouri River, about eight miles east of 

 the "Winnebago village of the Indian reservation of the Blackbird Hills, I ob- 

 tained another well-exposed section of the Upper Dakota group and of the 

 Cretaceous formations above it, as follows : 



3. Impure limestone, formed of an agglomeration of large shells, Inocer- 

 amus, Ostrea, &e, with sandy yellowish clay ; worked for lime from the sur- 

 face to the bed below, eight feet. 



2. Dark laminated clay, with shells and fish-remains, 7 feet. 



1. Yellow sandstone, easily disaggregated, with streaks of hard red sand- 

 stone or ferruginous clay, passing down to compact red sandstone, 50 feet. 



At this place, about two miles north of Warner's Quarry, I did not find 

 any leaves in the formation which from its top represents the Dakota group. 

 But in following the bluffs down to that new-opened quarry, I found an 

 abundance of remains of fossil plants to the highest point, or in the yellow 

 friable sandstone immediately topped by the strata of No. 2, the Benton 



1 Geological Survey of the Territories, 1807, p. 48. 



