GRENVILLE SERIES OF EASTERN NORTH AMERICA 633 



outlined embraces 83,000 square miles. In areal extent, therefore, it 

 can be compared only with certain of the greatest developments of 

 the Paleozoic limestones in North America as for instance the Knox 

 Dolomite of the Southern Appalachians. Over this area of 83,000 

 square miles, the Grenville series is not, of course, now continuously 

 exposed. It is penetrated in many places by great intrusions of 

 granite and anorthosite. This is especially true of the Adirondack 

 Mountains in which these intrusives are especially numerous. This 

 area, however, is one which was originally undoubtedly covered 

 by a continuous development of the Grenville series. 



In all probability, however, the areal distribution of the Grenville 

 series is much greater than this. In many parts of the Laurentian 

 Highlands far to the north of the limit here taken as the boundary 

 of the Grenville series, areas of white crystalline limestone and asso- 

 ciated rocks are found which are identical in character with that of 

 this series. Enormous developments of such limestones, identical in 

 all respects with the Grenville series, are, for instance, found about 

 the shores of Hudson Straits. Whether these northern limestones 

 belong to the same series is however not at present known with cer- 

 tainty. Definite information on this point may be obtained as our 

 knowledge of this great northern country becomes more complete. 

 It is furthermore very highly probable, as the Grenville series along 

 the southern margin of the protaxis everywhere disappears to the 

 south beneath the Paleozoic cover, that iii this direction it originally 

 had a very much greater extent than that over which it is at present 

 exposed. In this connection it is important to note that the pre- 

 Cambrian limestone series of the Highlands of New Jersey, which 

 has recently been studied by Bayley, has by him been correlated with 

 the Grenville series.^ The facts, however, in our possession at 

 present show that the Grenville series is one of the greatest limestone 

 series in North America and that it presents, as has been mentioned, 

 the greatest development of limestone known in the pre-Cambrian. 



CORRELATION OF THE GRENVILLE SERIES 



In connection with the Grenville series one other question presents 

 itself, namely, whether this great series represents a continuous suc- 



I "Preliminary Account of the Geology of the Highlands of New Jersey," Science, 

 May 8, 1908, p. 722. 



