_Ireland._—At Armagh, Ireland, Professor Hull found boulder beds of
Permian age, containing pebbles and boulders, sometimes 2 feet in
diameter. Some of the boulders must have been transported from a
region lying about 30 miles to the north-west of the locality in which
they now occur. It is difficult to conceive, says Professor Hull,
how rock fragments of such a size could have been carried to their
present position by any other agency than that of floating ice. This
boulder-bed is overlaid by a recent bed of boulder clay. Professor
Ramsay, who also examined the section, agrees with Professor Hull that
the bed is of Permian age, and unquestionably of ice-formation.[174]
Professor Ramsay feels convinced that the same conclusions which he has
drawn in regard to the Permian breccia of England will probably yet be
found to hold good in regard to much of that of North Germany.[175] And
there appears to be some ground for concluding that the cold of that
period even reached to India.[176]
_South Africa._—An ancient boulder clay, supposed to be either
of Permian or Jurassic age, has been extensively found in Natal,
South Africa. This deposit, discovered by Dr. Sutherland, the
Surveyor-General of the colony, is thus described by Dr. Mann:—
“The deposit itself consists of a greyish-blue argillaceous matrix,
containing fragments of granite, gneiss, graphite, quartzite,
greenstone, and clay-slate. These imbedded fragments are of various
size, from the minute dimensions of sand-grains up to vast blocks
measuring 6 feet across, and weighing from 5 to 10 tons. They are
smoothed, as if they had been subject to a certain amount of attrition
in a muddy sediment; but they are not rounded like boulders that
have been subjected to sea-breakers. The fracture of the rock is not
conchoidal, and there is manifest, in its substance, a rude disposition
towards wavy stratification.”
“Dr. Sutherland inclines to think that the transport of vast massive
blocks of several tons’ weight, the scoring of the subjacent surfaces
of sandstone, and the simultaneous deposition of minute sand-grains
and large boulders in the same matrix, all point to one agency as the
only one which can be rationally admitted to account satisfactorily
for the presence of this remarkable formation in the situations in
which it is found. He believes that the boulder-bearing clay of Natal
is of analogous nature to the great Scandinavian drift, to which it
is certainly intimately allied in intrinsic mineralogical character;
that it is virtually a vast moraine of olden time; and that ice, in
some form or other, has had to do with its formation, at least so far
as the deposition of the imbedded fragments in the amorphous matrix are
concerned.”[177]
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account