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Spieker, 1949) include a large proportion of sandstone. The marginal,
alluvial or delta plains were formed when sediment of sand grade was being
supplied from the Cretaceous highlands. A fairly large proportion of
finer sediments, now preserved as shale, was also retained on the plains.

All of the sand was not held, however. Much of it passed beyond and
into the bordering brackish and marine waters, where it formed deposits of
mostly marine, but partly brackish, sandstones. These fringing sandstones
are probably the “‘littoral sandstones” of Spieker’s (1949) classification, but
some may have been deposited far from the shore or delta front and will be
referred to here as fringing sands or sandstones. Some marine sandstones
of the Canadian interior have no visible contact with deposits of the mar-
ginal alluvial plains, and cover largeareas. There is some reason to believe,
however, that if traced west across the Rocky Mountains, which unfortu-
nately is not possible, it might be found that they would pass into marginal
alluvial plain deposits.

The greater part of the fine sediments, now preserved as shale, passed
into the sea, where it was deposited beyond the fringing sands. All thick
sections of shale, where fossiliferous, contain the remains of marine animals.

VARIABLE GEOGRAPHIC OUTLINES OF LOWER CRETACEOUS TIME
General Statement

In spite of the great mass of information gathered by geologists, it is
not yet possible to produce accurate paleogeographic maps of the western
interior of Canada in Lower Cretaceous time. An attempt to draw such
maps was made by McLearn in 1932. Twelve years later a revision was
necessary (McLearn, 1944). Another is now called for, but it will be use-
less to attempt it until some important problems of correlation are settled
and more is known of the subsurface stratigraphy of the Lower Cretaceous
of the interior regions of Canada.

Amid all the revisions, however, several features of the paleogeography
have remained unchanged. One is the greater variety of geographic out-
line in the Lower than in the Upper Cretaceous; that is, more distinctive
kinds of outlines throughout Lower Cretaceous time. Another is the
boreal origin of the Fort St. John seas. Another is the peculiar lineaments
of sea and marginal alluvial plain in middle Fort St. John time; however,
it is admitted that the paleogeographic maps of this time must be dras-
tically revised.

Much of the evidence of Cretaceous history has been destroyed. To
the west, rocks of this age have been removed from the Rocky Mountains;
to the north they have suffered denudation in the Mackenzie Mountains.

Possible Emergence in Middle Lower Cretaceous Time

No beds of middle Lower Cretaceous age have yet been recognized in
the Bullhead group of northeastern British Columbia, and the possibility of
a, break in the succession between the non-marine and upper part and the
marine and lower part of this group has been considered (See page 72).
If, in the course of investigation, substantial proof of this break is obtained,
emergence above the sea in middle Lower Cretaceous time in northeastern
British Columbia must be inferred.