548 C. X. GOULD CRYSTALLIXE ROCKS OF THE PLAIXS 



limestoue several hundred feet iu thickness correlated with similar limestones 

 of Cambro-Ordovician age in other localities."' 



CAMDEX COUXTY, MISSOURI 



In Camden Comity, sontli central Missouri, there is a single exposure 

 of igneous rock. Arthur AYinslow describes it as follows :^- 



"On the Camden and Laclede County line, at the Wheeler mine, in section 

 32 of township 27 north, range 16 west, is an area of intense local disturbance. 

 "With this is associated an erupted dike or boss of pegmatite. Special interest 

 attaches itself to this outcrop, as it is the only one of post-Archean age found 

 in the Mississippi Valley, with the exception of the Mesozoic eruptives of 

 Arkansas. Further, it is the only indication we have that igneous action or 

 metamorphism accompanied the crustal movements of the Ozark uplift. The 

 actual exposure of pegmatite does not exceed a few square yards, and. had it 

 not been that the locality was prospected for lead, its presence might never 

 have been detected. 



"The rocks of the dike consist of a graphic granite or pegmatite and of 

 white mica. -These do not seem to be disturbed or arranged in any special 

 order, unless it be that the mica prevails near the contact with the surround- 

 ing rocks. The dike seems to have the form of a boss or neck, which has 

 pushed its way up through the rocks. It is not probable that this intrusion 

 or eruption ever reached the surface."' 



Edward M. Shepard says, in a personal communication dated Xovem- 

 ber 2, 1922 : 



"The pegmatite exposure in Camden County is, without any doubt in my 

 mind, a volcanic dike. The immediate contact with adjoining rocks shows 

 metamorphism in the formation of beautiful yellow, contorted muscovite, 

 schist, and quartzite. The galena in the neighborhood is badly decomposed. 

 The rocks for many acres around, representing the lower formations, either 

 stand on edge or are greatly tilted." 



WOOD SOX COUXTY, KAXSAS 



On an area of about 120 acres in southern Woodson Count}', Kansas, 

 granite boulders varying in size up to seven feet in diameter are strewn 

 on the surface. Professor Twenhofel, who has studied these rocks and 

 their mode of occurrence, was first of the opinion that these "boulders 

 reached the position in which they are found through the agency of ice, 

 either glacial or floating, but more probably the latter.'" ^^ Later studies 

 of metamorphism in adjacent areas, however, have caused him to suggest 

 that possibly "the facts may be explained on the hypothesis that the 

 boulders mark the weathered outcrop of a dike." ^^ 



In a letter dated Xovember 1, 1922, Professor Twenhofel says: 



