BASIS OF PRE-CAMBRIAN CORRELATION Tile 
sedimentaries were swept away over the greater part of the region, 
leaving only the lower portion of the folds—the roots of the mountains 
—in the form of long narrow belts, separated by the granitic 
rocks marking the axes of jhe intervening anticlinal uphifts. This 
period of profound erosion constitutes what Lawson has termed the 
Eparchean Interval. Up to this time the movements which affected 
the continent of Laurentia were due, as has been stated, to thrusts 
coming from the southeast and caused by the negative element 
underlying the Paleozoic plain in this direction, at that time con- 
stituting the ocean bed, by its subsidence crowding against the posi- 
tive element which formed the continent of Laurentia. This is seen, 
as has been stated, in the distribution of the older rocks of the first 
two chapters of the pre-Cambrian in the form of long narrow belts 
running in a general northeasterly and southwesterly direction and 
representing the downward sagging portions of the ancient folds. 
Succeeding this long period of intense and widespread erosion, 
which followed upon the conclusion of Middle Huronian or pre- 
Animikie time, there was again a very widespread transgression of 
the sea upon the surface of the continent of Laurentia. In this was 
laid down a series of sediments which while occurring at localities 
sometimes separated from one another by hundreds of miles, vet 
preserve the same general features. These younger rocks form chains 
of islands fringing the east coast of Hudson Bay over a distance of 
about three hundred miles and have been described under the title 
of the Nastapoka series. This assemblage of beds dips toward 
Hudson Bay, generally at low angles, and lies in long parallel ridges 
with steep eastern faces. The strata comprise a group of arkoses 
and sandstones overlain by sandstones, argillites, cherty limestones 
and dolomites and calcareous shales with great intrusive sheets of 
diabase. The series has been found in places to have a thickness 
of at least three thousand feet and is further characterized by the 
occurrence at certain horizons of beds of banded jaspilite and iron 
ores. In the interior of Labrador, where the series dips at low angles 
toward the Atlantic, there is throughout a zone at least three hundred 
miles long, a development of similar rocks and here again occur the 
jaspilite beds. On the Atlantic side, at the head of Hamilton inlet, 
and further up the river of the same name, occurs a similar series, 
