EEE 
POWKNAL OF GEOLOGY 
¥ANUARV-FEBRUARY, 1909 
ONE ir ORICIN, OF THE AVMPHIBOLICES (OR THE 
LAURENTIAN AREA OF: CANADA* 
FRANK D. ADAMS 
McGill University, Montreal 
In a paper which appeared in the last number of this Journal 
an account’ was given of the development of the Grenville series in a 
great tract of the Laurentian Protaxis, some 4,200 square miles in 
extent, situated in the eastern part of the Province of Ontario, a 
study of which has recently been completed for the Geological Survey 
of Canada by Dr. A. E. Barlow and the writer. 
In this tract the Grenville series is not only of great areal extent 
but is of enormous thickness. About one-half of this thickness con- 
sists of limestone while the remainder consists of gneisses of sedi- 
mentary origin (paragneiss), with occasional quartzites and great 
bodies of amphibolite. This series is invaded by enormous bathyliths 
of gneissic granite and while in the southeastern portion of the 
area toward the margin of the Protaxis, the sedimentary series is 
comparatively free from igneous intrusions, toward the northwest 
the granite in ever increasing amount arches up the sedimentary series 
and wells up through it, in places disintegrating it into a breccia 
composed of shreds and patches of the invaded rock scattered through 
the invading granite, until eventually connected areas of the sedi- 
mentary series disappear entirely and over hundreds of square miles 
the granite and granite-gneiss alone are seen, holding, however, in 
: Communicated by permission of the Director of the Geological Survey of Canada. 
Vol. XVII, No. 1 I 
