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Haliburton area. From thence it descends toward the northeast, thus 
dividing the drainage to the south and west into the St. Lawrence system 
and to the north into the Ottawa River. Both the configuration of the 
lakes and the direction of the streams is guided to a large extent by the 
foliation of the rocks. This is especially true of the limestone area while 
the drainage lines on the granite gneisses show much less dependence 
on tectonic lines. 
The limestones and dolomites of this region are a part of a pre- 
Cambrian limestone terrane stretching from Georgian Bay to beyond 
the St. Maurice River in the Province of Quebec. In the contiguous 
area to the southeast of the Haliburton and Bancroft areas, Logan’s 
Hastings district, these limestones and dolomites, while containing 
basic intrusives, are less highly altered than in Logan’s Original Gren- 
ville of Quebec, where they are intruded and intensely altered by the 
same granite gneisses which invade them in the Haliburton and Bancroft 
areas. Since the less altered limestones of the Hastings district grade 
into the highly altered limestones to the northwest without divergence 
of strike and without the interposition of basal conglomerates, or other 
evidences of unconformity, Adams and Barlow believe that the entire 
terrane constitutes one series to which they give the name Grenville, 
and with this they correlate the limestones of the Adirondacks, thus 
grouping as one, an areal exposure of 83,000 square miles of limestone, 
one of the greatest developments of limestones in North America, and 
the greatest in the pre-Cambrian. The existence of certain conglom- 
erates in the Bancroft area, however, has caused Miller and other geolo- 
gists to suspend judgment as to the unity of this region. 
The position of the Grenville Hastings series in the pre-Cambrian is 
still left in doubt since they have not been found to connect with any 
of the correlated units. Nor do they resemble any of them lithologically. 
In the linear character of their topography and in their great dominance 
of sediments, they are more like the Algonkian than the Archean. 
Adams and Barlow class them as Archean, evidently using the term as 
synonymous with pre-Cambrian. 
The basement on which the sediments rest has nowhere been found. 
Adams and Barlow, however, follow Lawson in their belief that in cases 
like this, the sediments were deposited on the granites and that later 
the granite basement became re-fused and intruded into the sediments. 
The thickness of the sediments in the Haliburton and Bancroft 
areas is estimated by the authors to be about 17 miles, though they 
recognize the probability that isoclinal folding and other factors may 
