ALGONKIAN ROCKS IN VERMONT. 429 



place or another all the eminent characteristics of a basal con- 

 glomerate. 



An apology may be in order for dwelling so long upon the 

 evidence detailed in support of the conclusion that an uncon- 

 formity occurs at the base of the conglomerate, when, to many, 

 the evidence afforded by the conglomerate alone would he con- 

 sidered amply sufficient ; but in an area so greatly disturbed and 

 metamorphosed as this, it seems best to enumerate all possible 

 criteria that can be legitimately advanced tending to sustain the 

 above conclusion. 



SUMMARY. 



To summarize briefly, this paper is hoped to have substan- 

 tiated essentially the following facts : 



1. That immediately beneath the Lower Cambrian quartzite 

 in Vermont there is a series of more or less metamorphosed 

 clastic rocks of no inconsiderable thickness ; the upper member 

 of this series being a dark chloritic mica schist ; the lower mem- 

 ber a highly metamorphosed conglomerate, and between these 

 several pebbly limestones and pebbly micaceous quartzite strata. 

 Evidence for and against an unconformity at the top of the 

 schist is presented, but no satisfactory data are advanced to sus- 

 tain either interpretation. The evidence for a time-break at the 

 base of the conglomerate is thought to have been established, 

 and the data in support of this conclusion are discussed in some 

 detail. These rocks are referred to the Algonkian Period and 

 are provisionally called the Mendon series. 



2. That below the Mendon sedimentary rocks, a still older, 

 more metamorphosed and more variable series of stratified rocks 

 of Algonkian age occurs, together with gneisses and schists, 

 whose origin is unknown, and abundant metamorphic equivalents 

 of old basic igneous rocks. Many of the varieties of rocks 

 occurring in this series are enumerated, and, together with their 

 structure are contrasted with the rocks of the Mendon series, 

 whose basal member, the conglomerate, delimits the series above. 

 From their typical development in the town of Mount Holly, 

 Vt., it is suggested that these rocks be called the Mount Holly 

 Series. Charles Livy Whittle. 



