SUMMARY OF OPINION AS TO ORIGIN OF THE CRYSTALLINES. 369 



masses appear clearly to be areas in which the superior fine grained 

 facies have been removed through erosion. The physiographic features 

 of the region point to the same conclusion, as will be hereafter noted. 



Origin of the massive Crystallines and their present Configuration. 



summary of opinion. 



Since the time when King* made his first " Remarks on the Geology 

 of the State of Missouri " there has been considerable difference of opin- 

 ion as to the true character of the acid crystallines, but in all this half 

 century until very recently little has been done beyond making general 

 observations regarding the origin. More has been said, however, regard- 

 ing the old configuration of the region. 



Swallow t said nothino; about the crystallines after making a general 

 allusion to their igneous nature and giving a brief lithological descrip- 

 tion. Shumard J likewise only briefly alluded to these rocks in his report 

 on Sainte Genevieve county. 



The view Pumpelly § took was that the porph3ay region and the Ozarks 

 generally had been above the sealevel from a very early period. " Tlie 

 higher portion of the elevation does not seem to have been submerged 

 since before the Upper Silurian period, while broad areas in the flanks 

 of the range have apparently been dry land since the Carboniferous." 



In Broadhead's account || of Madison county the massive crystallines 

 are regarded as metamorphosed sediments which have been broken 

 through by dikes of quartz, greenstone, dolerite and specular iron ore. 

 In subsequent allusion to the subject the view presented lately ^[ is tbe 

 reiterated statement that the crystalline peaks have remained above the 

 sealevel since early Cambrian times. 



Winslow** follows closely the views previously expressed by Pumpelly 

 and by Broadhead that the crystallines have been subjected to weather- 

 ing agencies since Archean times. 



RECENT INVESTIGA TIONS. 



During the past few years the massive crystallines of the region have 

 been the subject of special inquiry by Haworth,tt who has studied with 

 the microscope the rocks from nearly all parts of the area. He has show^n 

 beyond all doubt that they are all igneous in origin and not highly meta- 



* Proc. Amer. Assoc. Adv. Science, vol. v, 1851, pp. 182-'J00. 



fGeol. Survey of Missouri, 1st and 2d Ann. Reports, 1855, pp. 134-135. 



J Geol Survey of Missouri, 1855-'71, 1873, p. 300. 



gGeol. Survey of Missouri, Iron Ores and Coal Fields, 1873, p. 8. 



II Geol. Survey of Missouri, vol. i, i874, p. 348. 



^American Geologist, vol. xiv, 1895, p. 383. 



** Missouri Geol. Survey, Iron Mountain Sheet, 1894, p. 6. 



tt Missouri Geol. Survey, Bull. 5, 1891, pp. 5-42. 



