TRANSACTIONS
OF THE
HULL
GEOLOGICAL
SOCIETY
KELSEY
HILL AND OTHER DRIFT PROBLEMS.
(Presidential Address: March 20th, 1924.)
Before launching
my main
theme,
allow me a retrospective glance, in addressing you on an occasion over a
quarter of a century ago (just twenty-six years in fact, but the
century-fraction strikes the time more impressively), I
used the opportunity to enumerate certain gaps in our knowledge of East
Yorkshire geology [
Some open questions in East Yorkshire Geology
] . My address was printed in your Transactions, and by
reference to it we can measure the substantial progress that has been made
towards filling the gaps, a task in which the
There were questions as to
Some
advance has likewise been made on almost all the other problems I mentioned,
and though some are still unsolved, their solution has been, at least,
approached.
Two
of these I propose to take as the subject of my present Address ; not with a
solution to offer, but in order to analyse the difficulties and to stimulate
a further attack upon them. These are both directly concerned with Drifts of
the Humber Gap. They are (I) The shelly gravels containing Corbicula
fluminalis, and (2) The Kirmington Estuarine Deposit. On both problems I
shall offer opinions, but with the consciousness that they are in neither
case decisive, since the evidence at present available falls short of
affording certainty, thoug'h sufficient to justify an opinion.
The
Shelly Gravels have been a problem ever since 1828, when John Phillips first
called attention to them. Why do they become suddenly so richly shelly at
Kelsey Hill, and what is Corbicula--a fresh-water shell--doing in
that galley where all the other shells are marine? The Kelsey gravels form a
link in the chain of gravelly mounds which is traceable from the summit of
Flamborough Head, across Holderness, to the Humber, and is seen again south
of it in
As to
the identity of the shell with the living form, I have sought the opinion of
my friend Mr. A. S. Kennard, our leading authority for Pleistocene and
Recent Fresh-water Shells, who kindly permits me to quote, as follows, from
his reply :--" Now, the Kelsev shells are
Corbicula
fluminalis
(Mull.) ; at least they are the same as the Pleistocene shells so-called
from many English deposits, and I cannot find any real difference between
them and the Euphrates and Nile shells. And they are derivatives. They were
fossil before they got in the Kelsey gravel. The worn condition of some of
the umbos is clear proof to me. By the way, some are marked with dendrites:
are the other Kelsey shells marked in a similar way ? That is, I think,
a point to be settled."
It was long ago. recognised by Gwyn-Jeffreys and Prestwich (Q.J.G.S.,
vol. 7,
1861,
pp. 448-51) that the shells at Kelsey Hill .ere not in their original
habitat and had been swept together from various depths and surroundings.
Nevertheless it was taken for granted that the gravels were marine, a view
that is still to some extent current. But the continued study of the shelly
drifts of Britain has led gradually to the recognition that where ice-sheets
of the Glacial Period have been forced inland from the old sea-basins they
have almost every-where brought in marine shells or shell-fragments along with
their other detritus, just as modern ice-tongues have been observed to do
today in
Granting this mode of formation for the gravels, we have still to seek an
explanation for the anomalous admixture of the Corbiculae.
That
they should exhibit themselves around the
But if Corbicula were not a
It is true that, against this idea of an easterly source, there
is a particular objection in the absence (so far as is known) of
Corbicula from all the boulder-clays and stratified drifts of the
coast-sections to the eastward in Holderness, although most of the marine
species associated with it at Kelsey may be found, therein.
To
meet this objection, it can be argued that the glacial river may have swept
the shells together from parts of the sheet which lay farther eastward than
the present coastline: or, alternatively, that the upper layers of the ice
may have carried material quite different from that in the lower layers---as
I have myself seen in a flat-lying glacier in Spitsbergen. The latter
possibility is indeed illustrated in the Holderness cliff-sections of
boulder clay, where bands of strikingly different composition, rudely
stratified and sometimes contorted together, often occur within the limits
of a single closely-welded bed. From observations in other localities also,
I think that the bringing together of different constituents into
juxta-position in this way has been common whereever an advancing ice-flow
fins impinged upon a rising slope, and is to be explained by the tendency of
this condition to cause a blockade of the lower part of the ice and an
over-riding or over-thrusting of it by the oncoming parts of the mass. The
occurrence of broad fiat belts of thick boulder-clay, as in Holderness, is
generally observable w'ith these circumstances ; and such belts formed near
the margin of the ice-sheet might be described as "expanded moraines." The
Kelsey gravels lie above a belt of this kind, and therefore are likely to
contain the material brought in by the upper layers of the ice.
However, whether we look east, west, or underground, for the origin of the
Cobiculae,
there
are difficulties. And so the problem stands! What is especially to be
desired is that some fresh-water deposit should be found in the
While
on the subject of the South Holderness drifts, I may be allowed to add a
word or two on new information obtained not long ago from Government borings
near Spurn. I was able to examine samples of the material from one of these
at Kilnsea, which penetrated deeply into the Chalk. Often when at
Dimlington. I have wished that we could get to know something of what lay
between the shelly Basement Clay seen at low water there and the
deeply-buried Chalk, an unknown space with room in it for many
possibilities. Forest Bed or Crags, perhaps? The boring gave the answer and
dispelled the hope for such novelties. From the record and the specimens (of
which I published a short account in the
"Summary of Progress," Geol. Surv.
for 1918, pp. 63-4), it is clear that drifts similar to those seen in the
Holderness cliffs extend right down to the Chalk here. The boring started at
25 ft. above O.D. ; and down to 127 ft. it passed almost entirely through
boulder clays, mainly of the ordinary dark purple type, and not, in any of
the submitted samples, notably shelly. I have long suspected that the very
shelly portions of the so-called " Basement Clay," seen on the shore
at Dimlington, Bridlington, and in rarer exposures in Filey Bay, are really
only local lenticles, occurring in the thick mass of the lower boulder
clays, like the smaller lenticle I found many years ago in the cliff at
South Sea Landing; and this we may now safely assume to be the case. The
shelly character is confined to bands or streaks, and does not pervade the
whole thickness of the lower boulder- clays. Also it goes without further
saying that nothing resembling the Corbicula-gravels of Kelsey
Hill was encountered in the specimens from the boring.
Below
127 ft. the boring passed through a few feet of stratified silty clay and
sand and then into tough "chalk-wash," this part of the section being
apparently quite similar to that seen at the bottom of the drifts in the
cliff section at the mouth of Danes' Dyke, and at Flamborough North Sea
Landing. The thickness of the " chalk-wash " was not precisely determinable,
as the
Now
let us turn to the other perplexing problem of the
This
bed was first noticed by Wood and
Thin
patches of red weathered boulder-clay (now no longer seen) and several feet
of coarse shingly gravel (still visible) overlie the estuarine bed, and
betoken Glacial conditions in the locality alter the deposition of the warp
; while the boulder-clays and stratified drifts proved in the borings afford
clear proof of Glacial conditions here before the estuarine episode. The
shells of the warp, few in number and in species, are clearly in their
original .surroundings, the bivalves generally with valves united; and all
are such as still live together in estuaries throughout the North Temperate
and Boreal regions of
The
particular interest of the section lies in the fact that here we have
convincing evidence for a marine intercalation between deposits of Glacial
origin; and it is the only place known to me in
Moreover, the estuarine material reaches a height of close upon 100ft. above
O.D.; and as it must have been laid down in very shallow water, probably
between tide- marks, it may be taken to denote the exact measure of the
submergence during its accumulation.
But
think what this implies! A submergence of 100 ft. would put all Holderness
under water; and all the country east of the Wolds in Lincolnshire; all the
Fen country farther south; all the Vale of Ancholme; most of the Vale of
York; and great spreads in the valley of the Trent right up to Newark; not
to speak of the wide regions, both northward and southward, more remote from
Kirmington. Yet in all this area there has been nowhere found anything
comparable to this Kirmington deposit; that is to say, no deposit
intercalated with the drifts above present sea level containing an
indubitably indigenous marine fauna. On the contrary, everywhere else on
these low grounds we seem to have clear indication of continuous sub-aerial
erosion during and since the closing stages of the Glacial period. Why
should the Kirmington evidence be so exceptional? That is the puzzle: and
the solution of it is yet to seek.
It is
true that for evidence of the character and contents of a deposit of this
kind we have to depend upon an artificial opening, and if it had not been
for the Kirmington brickyard, we should have remained ignorant of this
instance; so that other occurrences may remain undisclosed. But in these
well-populated lowlands the presence of a useful stoneless brick-earth is
pretty certain to have attracted practical attention in the past, when the
making of bricks and tiles was distributed almost entirely in small local
yards. Also, the whole of the ground has been systematically examined by the
officers of the Geological Survey, which again reduces the chance of
undiscovered occurrences.
I am
satisfied, after repeated examination, that we cannot, at Kirmington, invoke
the agency of transportation by ice to explain the facts. The conditions are
quite different from those displayed by the mixed shreds of sea-bottom among
the boulder-clay at Bridlington, Dimlington and other places on the coast,
where we are driven, by clear evidence, to this explanation. The present
sequence at Kirmington is a natural one. As I interpret it, we have, in the
Glacial sand and gravel which forms the floor of the brickyard, the
thaw-water outwash from the retreating ice which had previously laid down
the deep lying boulder-clays proved in the borings. What I think must be a
continuation of the same sand and gravel was formerly exposed at about the
same level in a small pit in the hollow near Croxton, three-quarters of a
mile N.N.E. of Kirmington, where it has yielded the usual worn and
fragmentary marine shells of the Holderness gravels, including, as
previously mentioned, three specimens of Corbicula
fluminalis.
Reid
considered this sand and gravel to be the off-shore representative of the
Kirmington warp, and spoke of the two together as the deposits of the
"Croxton and Kirmington
fjord." But both the physiographical and the new stratigraphical evidence
tell against this correlation, and I think we must regard the estuarine warp
as indicative of a different set of conditions marking a definitely later
stage. The presence of peat and of loam with fresh- water shells, above the
sand and gravel but below the estuarine deposit, denotes that the tract was
above sea level for a time, anterior to the estuarine phase. It seems most
probable therefore that the sandy out-wash gravels were themselves spread
upon a land surface, or, at least, on an area which could be converted into
land by the very moderate thickness of the gravelly deposit. As we have no
actual indication of the sea-level at this time, we cannot measure the
maximum amount of the later sub- mergence; but it must at least have
exceeded 20 ft., to allow the accumulation of the thickness of warp seen at
Kirmington. If the laminated clays exposed in a brick-yard at Great Limber,
about three miles S.E. of Kirmington, belong to the same episode, as Reid
suggests, the bounds of the submergence would be raised by another 20 ft.,
as the deposits there reach to at least 120 ft. above O.D. But no shells or
other fossils have been detected at Limber; and the laminated clays differ
also in other respects from the Kirmington warps, and appear to be nearer
akin to the laminated drift formerly so conspicuous in the cliff at
Hilderthorpe, south of Bridlington, which we interpret as the product of a
local ice-dammed lake.
It
is, however, not unlikely that, granting the unfossiliferous laminated clays
of this type to be thaw-water sediments deposited in pools bordering the
ice-sheet, yet the general level of these pools may have been governed by
the sea-level of the period; and that there may have been connexions, more
or less open, between there and the sea. Certainly, the levels round about
100 ft. above present O.D. seem to have had some controlling influence upon
a considerable portion of the stratified lowland drifts of Yorkshire and
But
let us leave the question of levels for the moment, in order to consider the
topmost beds of the Kirmington section. These betoken strangely different
conditions from those of the estuarine warp stage. The coarse battered
shingle of flints with a few foreign stones, 8 or 10 ft. thick in places,
directly overlying the warp wherever the section approaches the crest of the
rising ground, was described by Reid as " beach shingle," thereby
implying wave-action. But the Chalk valley is long and barely half a mile
wide, with gentle slopes on both sides; and, as we know now from the
borings, the Kirmington hillock lies about midway in this valley, with no
bare Chalk in the immediate vicinity. It is inconceivable that wave-action
powerful enough to form a shingle-bank so coarse and thick as this could
arise in so narrow an inlet. Moreover, the shingle has none of the
distinctive characters of a beach-shingle, but is like the bouldery "
cannon-shot" type of Glacial gravel. It has its nearest analogue in the
moundy: crescentic mass of bouldery gravel associated with boulder-clay
occurring at Wrawby near Brigg, five miles west of Kirmington. This mass of
drift is the most conspicuous feature on the low ground of this
neighbourhood west of the Wolds, and is just opposite the gap in the Chalk
at Melton Ross, which breaks by a low col into the Kirmington valley. The
moundy mass, largely consisting of chalk and flint, appears from its shape
ant composition to have been the moraine of a tongue of ice which passed
westward up the Kirmington hollow and through the gap at Melton, at a late
stage of the Glacial period. The relationship of the drift to the gap is
well illustrated by the one-inch Geological Survey map (Old Series, Sh. 86).
I
think that we can reasonably interpret the top "' Shingle " at
Kirmington as part of the same story, and
Now
let us consider further the difficulties in which we are involved. The
shell-bearing warp, if deposited at its present level, proves a submergence
of 100 ft. at some stage between the beginning and the end of the
glaciation. But why is the evidence confined to this one spot, and
unobtainable elsewhere in the wide extent of adjacent country, both east and
west, at or below this level? And from which direction--east or west--did
the salt water obtain access to this sheltered valley? I have sometimes
speculated on the possibility that the bed, although on its original site,
may have been bulged up above its original level, along with the drifts
beneath it, by the pressure of the tongue of later ice which re-invaded the
valley and brought in the capping drift. This kind of elevatory movement
does appear to have taken place at Speeton, where there is evidence that the
shelly bed at the base of the drifts has probably been lifted to its present
position of some 90 ft. above sea-level by the bulging up-creep of its
foundation of Speeton Clay under the pressure of the neighbouring chalk
escarpment. But the possibility of any such agency at Kirmington is very
remote; and, even if entertained, it really does not help matters. For,
supposing the bed to haw been deposited at any lower level, we are faced
still more acutely by the difficulties of explaining its absence from the
coast- sections and of finding a place for it in the Glacial sequence seen
there.
Excluding the great gap of the Humber, it is note-worthy that the gap
through the Chalk Wolds at Kirmington, with a present passage at 80--85 ft.
above O.D., and a still lower passage if all the drift were removed, is the
only other, place in the whole of the Chalk range between the Wash and the
Vale of Pickering where the hills are broken to below the 100 ft. contour;
and I think that this fact may have something to do with the unique
occurrence and preservation of the estuarine bed. Some further evidence
bearing on the pre-glacial condition of the Kirmington valley has come to
hand since our borings were made in 1903- 4.
Borings for water at Brocklesby,
1½
miles E.N.E., and at the Immingham Docks, 6 miles E.N.E., of Kirmington,
of which particulars are preserved at the Geological Survey Office, have
revealed the presence of a drift-filled trough in the Chalk, which appears
to be the down-stream prolongation of the Kirmington hollow.
At Immingham the Chalk-floor is at about
240ft. below O.D.,
and at Brocklesby at about
140 ft.
below O.D., while, as previously stated, we found it approximately at O.D.
at Kirmington.
We
do not know that any of the borings actually touched the deepest part of the
valley in their vicinity; but whether they did or not, it is clear that the
down slope of the valley-floor is very sharp, and denotes a stage of
intensive erosion and relatively high elevation before the onset
of
the Glacial conditions. This bears out the evidence north of the
Later, however, during the glaciation, the low escarpment saddle
between Kirmington and Melton Ross was
Nevertheless, thee absence in the surrounding country of any of the more
lasting traces of a coast-line, such as a shore-platform or an old base-level,
is remarkable, and appears to indicate that the submergence was of short
duration. It is evident, also, that there has been much re-modelling of the
surface by subaerial agencies since this period, particularly in the area
west of the
Wolds;
and the retrogression of the Chalk escarpment in this quarter has almost
certainly been deep enough to explain the disappearance of any narrow
shore-ledge which may have existed on its flank.
I have still avoided the question whether the salt-water invaded the col
from the east or from the west, or from both sides simultaneously ; and, in
truth, I can find better objections against, than reasons for, either an
easterly or a westerly sea. I hope that the Hull geologists will sooner or
later bring some nmv evidence to bear on this aspect of the matter which
will rescue it from the realm of speculation. Bur the best guess I can give
at present --a guess that I first entertained over 30 years
ago and have not
yet
been able to better--it is that
the
rise of sea level
followed upon the maximum glaciation, when the East
British ice reached its farthest up the easterly slopes of the Yorkshire
Wolds and covered most of the Lincolnshire Wolds and all the great Fenland,
while the Pennine glaciers overspread the Vale of York and the more
southerly part of the Humber basin to at least as far south as Retford and
Gainsborough. By these ice-sheets the sea would be blocked out from the
low-lying areas which would have otherwise been submerged, and the boundary
between land and sea would be as confused as it is now in
Upon
the waning of the glaciation and the consequent recession of the ice-border,
the sea would creep in along its margin wherever the land was low enough ;
but would still be confined to the uncovered tracts, irregularly localized
and determined by complex factors, as they are at present in
I
still hold that the evidence of the coast-sections between the Humber and
the Tees can only be interpreted on the supposition that the basin of the
North Sea, in these latitudes was occupied by an ice-sheet continuously from
the beginning to the end of the production of the Yorkshire boulder-clay
series, and that the marginal recessions were irregular and partial. The
main recession was that which occurred just before the deposition of the
Hessle Clay; and it appears to have been during the later portion of this
interval that the estuarine waters invaded the Kirmington gap. The
That
is my working hypothesis. I am conscious of the weak places in it, and of
difficulties which arise when we seek to extend it beyond the
[Note -This article has been scanned in from original printed format and then put through an OCR program by Mike Horne. The process may have introduced some new spelling errors to the texts. Some original misspellings have been corrected.]
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