File:The Quarterly journal of the Geological Society of London (12735773383).jpg

76
S. V. WOOD, J TIN., AND F. W. HARMER ON THE
signs of any gradual disappearance of the shells by the abstracting
agency being apparent, and also that the dividing line was very
irregular, the shelly crag often rising in a boss or prominence (as in
sections I. and II.). The unfossiliferous layers underlying in some
cases detached portions of shelly material, as in section III., also pre-
sented a difficulty. In addition to these was the presence not merely
of a separate and independent stratification, but the circumstance of
bands of ferruginous loam at the base of the sands, sometimes, as in
section II., enwrapping in an entirely unconformable way pro-
minences of shelly crag.
Fig. 2. /Section II, in a pit three furlongs east of Great Bealinys
church. (Scale 10 feet to the inch.)
a and b as in fig. 1.
b\ Band of dark, partly indurated, ferruginous loam.
Notwithstanding these difficulties, however, we are inclined to
think that the view expressed by Mr. Whitaker is correct ; and we
have been principally led to that conclusion by the detection of the
band of pebbles shown in section I., which seems clearly to indicate
that the original oblique stratification of the Crag once prevailed
through these sands, and that the agent which abstracted the
calcareous material was inoperative upon the pebble-band, which
remained as part of the original stratification. If this view is
correct, it is clear that in many, indeed in most, cases the material
has been so far restratified in the process, that the present stratifica-
tion of the sands is often as unconnected with the original stratifica-
tion of the deposit as is cleavage or jointing in the cases of the old
rocks.
In saying this, however, we would not be misunderstood as
suggesting that there has been a rearrangment of the whole of the
original material of the Crag, because, since the originally oblique
bedding of the pebble-seam remains unaltered, it is evident that the
arrangement of the sand particles among which this was imbedded
cannot have changed, or the position of the pebble-seam would have
changed with them. It is the argillaceous and ferruginous material
taken up by the percolating water which has been redeposited, so as
to form, in combination, the coloured threads and bands which give
rise to this apparently new stratification.