188 



BUREAU OF AMERICAN ETHNOLOGY 



[bull. 60 



superficially by members of the Bureau of American Ethnology/ 

 and later by Dr. W. A. Phillips, by the present writer, and others. 

 Dr. IMiillips made extended examinations of the quarries under 

 the ausi)ices of the Field Museum of Natural History.- 



The limestone strata, through which the chert concretions are 

 distributed in interrupted layers, occupy an approxi- 

 Geoiogy of the Lo- jj^.^j^g^y horizontal position and have been subject to 

 extensive disintegration by the action of acid-charged 

 waters. In the vicinity of M\\\ Creek the disintegration and leaching- 

 out of the calcareous matter of the superficial strata have been com- 

 plete, and as a result the underlying Devonian floor is buried be- 

 neath extensive bodies of the residual clays (fig. 64). In many 

 places these clays reach a thickness of 25 feet or more, and the chert 

 concretions, not being subject to disintegration, are distributed ir- 



', \ ■ > s \ ) 



"i; ) 5 ! i i ! 1 1 I ! I r 



I 1 r 



"! r 



T i 1 '. \ i i r 



-! ) i r 



1 ) i \ \ i S i i I ) ) 5 ) i \ 



1 r — ) ! \ \ T — r 



T~i — r 



1 r 



Fk;. 04. Section indicating the relation of the residual nodule-bearing deposits to the 



limestones. 



regularly throughout the deposits. It is these concretions that the 

 aborigines sought and obtained at enormous cost of time and labor. 

 The manner of the original occurrence of the concretions in the 

 limestone strata is shown in figure 65, and examples 

 The Concretions of typical forms appear in figure 66. These concre- 

 tions differ from the prevailing tyi^es obtained from 

 the ui)per carboniferous formations to the north and east in being 

 usually of flattish form and of exceedingly varied outline. They are 

 often joined by irregular necks over considerable areas, but the trans- 



1 Thomas, Report on Mound Explorations, p. 154. 



-A preliminary report of his operations appears in tlie Anicrirnn Anthropologist, 

 January-March, 1900, and his later investigations, the most thorough yet made of any 

 of the concretion-producing quarries, are in course of preparation for publication by the 

 Field Museum. Dr. Phillips has very generously permitted the writer to embody portions 

 of his data in these pages. 



