333
Geological Records from the
Valley of the River Stort
BY JOHN F. HAYWARD, Ph.D., M.Sc., F.G.S.
The two parts of this paper are quite unconnected except for the fact
that both refer to the region of the Stort valley. The first gives an
account of a series of trial boreholes at Bishops Stortford and the second
deals with a lithological facies of flint found at Stansted Mountfitchet.
1. THE BISHOPS STORTFORD BOREHOLES
These consisted of a series of thirteen shallow bores of which No. 1 was
sunk in the yard of the Anchor Inn, South Street, Bishops Stortford, and
No. 10 was within the grounds of the Sewage Disposal Works to the south
of the town, Nos. 11 and 12 were on the rising ground to the east of the
main series as indicated in Figure 1. There was also a number 9a near
to number 9. The line of bores covered a distance of about one mile. The
bores were shallow, No. 7 being sunk to a depth of 40 feet, Nos. 10 and 11
to 30 feet, and the rest to shallower depths. Nevertheless, some interesting
facts emerged.
Figure 2 gives the section which cuts obliquely across the River Stort.
It shows a series of gravels and other river deposits lying upon the Reading
Beds which here have overlapped the Thanet Sand and He directly on the
Chalk at about 150 O.D. The soft Chalk with flints was proved at this
depth in borehole No. 7 only.
The Reading Beds were proved in several boreholes, but not in such a
manner as to give a complete sequence. By combining the records from a
number of boreholes and assuming the bed3 to have a constant disposition
over the whole range, the following composite sequence is obtained:—
Fawn silty clay............ 8 ft. or more.
Fine sand ............ 10 ft.
Bed and brown silt ... ... ... 3 ft. passing down into
Grey-green sandy clay......... 8 ft. or more.
Gap of 4 ft.—details not available.
Soft brown sandy clay......... 2 ft. 6 ins. or more.
Soft green sandy clay ... ... __ 2 ft. 6 in3.
Chalk.
In borehole No. 6 only are to be found at least 6 ft. of Chalky Till,
somewhat sandy in the lower part and more clayey above. This offers a
comparison with the Lea Valley, for the author has found a deposit of
Boulder Clay in the bottom of the Hedge Lane channel, Edmonton, and
it may be that borehole 6 lies within the area of a former channel of the
Stort, possibly a deep channel. This is corroborated by the presence on
either side of this of beds containing peaty material which may represent
bog conditions bordering the channel. These are represented by the letter
"P" in Fig. 2.
The valley gravel was variable. In several boreholes it consisted of small
sub-rounded or sub-angular white flints grading down into the matrix which
contained also some quartz sand.