Palmer — Flora of the Grand Falls Chert Barrens. 99 
Creek barrens is a massive silicious bed near the base 
of the Keokuk stage of the Mississippian series or Lower 
Carboniferous rocks. Throughout Southwest Missouri 
and adjacent territory occupied by strata of this age 
chert is everywhere abundant, usually in the form of 
nodules, lenses or layers interbedded with limestone. The 
Grand Falls Chert layer, as this formation is called from 
the falls on Shoal Creek where it is typically exposed, 
is remarkable if not unique for its great extent and thick- 
ness. The surface exposures, with the exception of the 
small area referred to above on Turkey Creek, north of 
Joplin, are confined to the valley of Shoal Creek and 
several of its small tributaries in the northern part of 
Newton County, Missouri. The area has been carefully 
studied and mapped by the United States Geological Sur- 
vey, and the formation is described in the Geological 
Atlas of the Joplin District, published in 1907. The ex- 
posed area perhaps aggregates about two square miles, 
beyond which the chert disappears under higher strata 
and is of wide extent as revealed by hundreds of shafts 
and drill holes that have penetrated it in search of lead 
and zine ores, of which it often carries valuable lodes. 
To the northward in Jasper County it is known to the 
miners as the ‘‘sheet ground,’’ and is the basis of a very 
extensive mining industry. In the vicinity of Webb City 
the chert is found at an average depth of about one hun- 
dred and fifty feet below the surface, and its thickness 
ranges from thirty to forty feet. Elsewhere it is said 
to attain a maximum thickness of over eighty feet. 
Shoal Creek, along which the principal exposures of 
Grand Falls Chert occur, is a swift flowing stream of con- 
siderable volume, that might well be denominated a small 
river. It has its rise in the highlands of Barry County, 
flowing in a winding but generally northwesterly direction 
until it joins Spring River several miles beyond the Kan- 
sas line. For the greater part of its course it traverses 
a rugged hilly country, through which it has carved a val- 
ley of varying width and depth, the adjacent hills some- 
