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B. N. A, BOUNDARY COMMISSION. A 



















saints is about 750 feet; 700 feet being the thickness assisneae ee ; 
No. 4, in Nebraska. This would allow the beds to be almost perfectly — 
a horizontal, as No. 5 is only about eighty feet thick, when seen near Wood } 
~~ Mountain, and the base of No. 4 is not exposed at the first mentioned — 
B locality. 
The possibility of the discovery of lignites in the lower Cretacous, 
has been already adverted to, and the extent of this portion of the — 
formation, may perhaps become a question of some importance in this {" 3 
regard, Wy 
re Lignite Tertiary Formation. bt 
a 365. The highest beds of the Lignite Tertiary series, in the vicinity | ae 
¥ of the forty-ninth parallel, are probably those which occur about Porcu- — 
ie pine and Pyramid Creeks, and the Great Valley, and high lands south . 
of the Missouri Coteau ; and I am inclined to believe that if there is any ie i 
difference of horizon among the beds of these localities, those of the first __ 
mentioned may somewhat overlie the others. At the same time, in a na fy 
a region where local dips due to original irregularity of deposition,so much = 
surpass in amount those due to any general inclination of the beds; _ 
c and where individual strata have so little constancy, and good exposures — : 
3 occur with comparative rarity, it is impossible to arrive at any very 
a precise knowledge of the equivalency of the beds of different localities. 
in The creeks above mentioned cross the Line at the 385, 352, and 345 mile ; 
points respectively, and have been proved by the explorations of Lieu. = 
tenant Greene of the U. 8. Northern Boundary Survey, to be tributaries _ 
of the Quaking Ash, an affluent of the Missouri. In connection with this 
part of the section, numerous and important beds of lignite occur, in 
" association with greyish, yellowish, and purplish arenaceous clays, sands, 
and little consolidated sandstones, and bands of ironstone. The deposit 
i: shows no trace of marine or brackish-water conditions, and wherever 
4 remains of molluscs are found they are those of frésh water. The lignites 
a appear to prove the frequent elevation of parts of the area above the 
ng surface of the water, and the general prevalence of plant remains in the 
intervening sands and clays, show that at no time were land surfaces far 
removed. 

