ABSTRACTS OF PAPERS 147 



GEOLOGY OF THE GUILFORD, CONNECTICUT, QUADRANGLE 

 BY WILBUR G. FOYE 



(Abstract) 



The Guilford Quadrangle is situated immediately east of the New Haven 

 Quadrangle and forms a position of the area whose geology will be described 

 in the projected New Haven folio. 



A large hatholith of tonalite, whose center lies in the town of Killingworth, 

 is the dominant feature of the structure of the area. A border of gneiss, suc- 

 ceeded by a horder of nietainorphic sediments, dips gently away from the 

 central batholith on all sides. 



At the south of the area the tonalite, previously rendered gneissic, has later 

 been altered by impregnation by a granite allied to the Sterling gneiss of 

 Rhode Island. 



Presented extemporaneously. 

 Discussed by B. K. Emerson. 



Discussion 



Professor Emerson : I wish to express appreciation of this paper. The 

 Walker Building, next, east, to our meeting place, is a fine example of the 

 Mouren granite. The trimmings of Willi ston Hall, where we have held our 

 meetings, is of a more gneissoid type of the same age, from Pelham, east of 

 Amherst. The Amherst schist had better have been named the Wilbraham 

 schist, as the good outcrops in Amherst have been quarried away or covered. 



JASPEROID OF THE JOPLIN DISTRICT, MISSOURI, KANSAS, AND OKLAHOMA * 



BY W. S. TANGIER SMITH 



{Abstract) 



In this paper, following an outline of the geology of the Joplin District and 

 a brief account of the characters of the jasperoid, the various hypotheses con- 

 cerning its origin are reviewed and facts are presented in support of the 

 view that the rock is a replaced limestone. This is assumed as a basis for all 

 the conclusions in the remainder of the paper. 



The hypothesis that the chert breccias, of this district are a residual from 

 the solution of limestone is rejected for the reason (among others) that the 

 conditions show most of the limestone originally associated with the chert of 

 the ore bodies to have been replaced by jasperoid or dolomite, instead of being 

 lost by solution, leaving cavities. The occurrence of the jasperoid as a cement 

 to the chert breccias is explained as the result of flowage of the limestone at 

 the time of the brecciation of the cherts, and evidence is presented that in the 

 sheet ground also the limestone which the jasperoid replaces has undergone 

 at least slight deformation by shearing and flowage prior to its silicification. 



The brecciation of the chert and the flowage of the limestone are both con- 

 sidered to be the result of stresses developed within synclinal folds of the 

 unusually competent Grand Falls chert. The breccias are believed (on ample 



1 Read before the Cordillearn Section of the Society March 26, 1921. 



