308 
GRASSY BLACK SHALE 
it to the Genessee shale (still Mid Devonic). De Verneuil,® after 
viewing the contained fossils in the field, sided with Owen as to 
its Carbonic age. In 1866, Meek and Worthen ® were still calling 
this Black shale by the New York name, the Genesee slate. 
On the Mississippi River the Black shale was noted as early as 
1855 by Swallow,^ although only incidentally. A few years later 
it was briefly described by Meek and Worthen,® who had examined 
the formation on the east side of the great stream. In both of 
these allusions the entire section of shale immediately beneath 
the Louisiana limestone was considered. This was also the case 
with the other references to this shale in Indiana and Kentucky. 
Whether or not this section was an exact terranal equivalent of 
the Chattanooga black shale of distant Georgia, as in recent 
years described by Hayes,® remains to be shown by further field 
correlations. Ulrich was inclined to extend the title Chattanooga 
Terrane of the southern Appalachians northwestward to Iowa, 
including by that term both the Green (Saverton) and the Black 
(Grassy) beds, exposed at Louisiana, Missouri, in the one forma¬ 
tion. 
When the Black shale of northeastern Missouri again comes 
into prominent notice the shale section is divided into an upper 
Green member, and a lower Black member. Both of these beds 
develop westward into heavy bodies having a combined thickness 
of more than 100 feet.^^ So important are the sections a few 
miles from Louisiana, on Grassy, Noix, and Buffalo creeks, that 
their terranal significance requires distinct names. The Black 
shale is designated in the fieldbooks of the Survey, the Grassy 
Creek shale. Soon afterwards this distinctive geographic title 
is formally published as a terranal term.^® 
Since the stratigraphic importance of the black Grassy shales 
comes to be fully recognized it is carefully traced northward 
and southward from Louisana. Although at the latter point 
it is only 4 feet thick the formation attains a much greater vertical 
5 Bull. Geol. Soc. de France, T. IV, p. 13, 1847. 
6 Illinois Geol. Surv., Vol. II, p. viii, 1866. 
7 Missouri Geol. Surv., 1st and 2nd Ann. Repts., p. 107, 1855. 
8 Am. Jour. Sci., (2), Vol. XXXII, p. 167, 1861. 
9 Bull. Geol. Soc. America, Vol. II, p. 143, 1890. 
10 Bull. Geol. Soc. America, Vol. XXII, p. 608, 1911. 
11 Bull. Geol. Soc. America, Vol. Ill, p. 286, 1892. 
12 Missouri Geol. Surv., Vol. IV, p. 47, 1894. 
13 Proc. Iowa Acad. Sci., Vol. V, p. 63, 1898. 
14 Am. Jour. Sci., (4), Vol. XXXVI, p. 160, 1913. 
15 Froc. Iowa Acad. Sci., Vol. XXIII, p. 113, 1916. 
