88 PETROLOGICAL ABSTRACTS AND REVIEWS 
MILLER, WILLET G., and Knicut, Cyrir W. The Pre-Cambrian 
Geology of Southeastern Ontario. Report Bureau Mines, XXII, 
Part 11) Woronto, 19142 Pp: va4- 151, figs. 67) pls: 44 maps 7, 
bibliographies. 
The oldest rocks of the region are essentially green schists of igneous 
origin, which were extruded during the Keewatin period. In other parts 
of Ontario this was a period of great volcanic activity, and enormous 
quantities of rock were erupted. Succeeding this active period came one 
of sedimentation during which the Grenville series, variously estimated 
at from 50,000 to 94,406 feet in thickness, and consisting of crystalline 
limestone, greywacke, quartzite, and slate and iron formations, was 
laid down. During Laurentian times both the Keewatin and Gren- 
ville rocks were invaded by great masses of granite and syenite. This 
caused a folding and crumpling of the older rocks, and their alteration 
to schists and gneisses. Injection schists appear in certain places. 
Later, erosion removed much of the Keewatin and Grenville material 
and exposed the deep-lying igneous rocks. The region now became 
partially or entirely submerged and beds of conglomerate and quartzite 
of the Hastings series were deposited. The youngest pre-Cambrian 
rocks are post-Hastings, and include granite, diabase, and basalt. 
During the Paleozoic the surface sank below sea-level, and limestones, 
sandstones, and shale were deposited, and these were later elevated to 
their present position. 
Numerous analyses are given, but little attempt has been made to 
describe the rocks petrographically. 
