1916] The Ottawa Naturalist. 31 



St. Lawrence valley to the Cretaceous boundary "of the Paleozoic 

 in Georgia and Alabama. Thus there is gradually being amassed 

 more and more material significant of the diagenesis of the Cam- 

 brian and Ordovician rocks, and relating to the history of the 

 seas from and under which they were deposited. It will not do, 

 in this study, to dub all. coarse, clastic, intraformational rocks, 

 whose constituents may or may not be rounded, as simple con- 

 glomerates all of similar origin. It is believed that a more 

 careful examination of these intraformational structures in the 

 field and laboratory will greatly aid in deciphering the his- 

 tory of the original limestone sediments. Upon the rock-walls 

 of the Bellefonte quarries have been observed many of the struc- 

 tural phenomena which are to be found on shallow water areas, 

 mud-flats and beaches of to-day. Ripple-marks, mud-cracks, 

 edgewise conglomerates and breccias are disclosed in close stra- 

 tigraphic sequence wherever exposure ami subacrial erosion 

 have been able to develop the hidden structures. The con- 

 clusion has been reached that nearly all of the intraforma- 

 tional conglomerates and breccias seen at Chambersburg, Belle- 

 fonte and Tyrone, Pennsylvania, are of extremely shallow water 

 origin; in fact, their formation postulates an emergence from 

 the sea such as is common under tidal action. That mud- 

 cracked beds and intraformational breccias are in certain cases 

 one and the same thing is, perhaps, the only original contribu- 

 tion to the origin and classification of intraformational struc- 

 tures. 



Glomerate axd Phexoclast. 



Before proceeding with the classification of intraforma- 

 tional structures, it seems best to analyz the term conglom- 

 erate.* Indeed the study of intraformational "conglomerates" 

 requires a more careful consideration of all conglomerates than 

 has heretofore been deemed necessary. A review of the liter- 

 ature, as well as certain examples studied in the field, has shown 

 that not all intraformational conglomerates are made up of 

 water-worn materials; in fact, certain of them are composed of 

 distinctly brecciated fragments which show no signs of attrition 

 by water transportation, a common characteristic according to 

 most geologists. Walcott (op. cit. p. 192) recognized this diffi- 



* Most stratigrapheis would certainly agree that true breccias cannot be defined under 

 the general term of conglomerate, yet if we refer to the Century Dictionary we 

 discover that although a conglomerate is defined as "a rock made up of the rounded 

 and water-worn debris of previously existing rocks", a breccia is defined as "a con- 

 glomerate in which the fragments, instead of being rounded or water-worn, are 

 angular". No less an authority than J. D. Whitney is responsible for these definitions 

 but most geologists would probably refuse to accept them as they stand. Quotation 

 is taken from the Century Dictionary only to show that there is some confusion at 

 least at present in regard to just what conglomerate means. 



