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 zinc 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 Palls 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- 



