11
ON THE MOLLUSCA OF THE SHELL-MARL
OCCURRING AT FELSTEAD AND IN OTHER
PARTS OF ESSEX.
By J. FRENCH. With remarks by W. H. DALTON, F.G.S., late of the Geological
Survey,
In the Geological Survey Memoir to Sheet 47 ("Geology of the North-
west part of Essex," &c), under the heading "Post-Glacial Drifts,"
there are frequent notices of clay containing broken shells, and of
shell-marl, with short lists of contained fossils. In the valley of the
Blackwater, in the neighbourhood of Witham, shell-marl appears to
attain its greatest development. It is there described as being
associated with peat, as well as with sand and gravel. Also there is
an account of similar marl west of Sudbury, in the valley of the
Stour, and a list of shells is given for both localities. For a Strati-
graphical description of the shell-marl, the reader is referred to the
above-named Memoir. Wherever it there comes under notice, the
position and character of the beds for all localities is similar, and
although there is no notice of the much more modern deposits at
Felstead, the same description will largely apply. For instance, at
Witham (see Fig. 19 of Memoir), shell-marl is described as being asso-
ciated with loam and peat, and passing at times into a buff laminated
clay, which is also the case at Felstead; and there are many other
marks of similarity which leave little doubt that the patches which
occur throughout Mid- and North Essex are closely analogous de-
posits, and a comparison of the shell-lists will support that view.
In the neighbourhood of Felstead there are two or three principal
developments of these deposits. At the west end of the village there
are some three meadows, the soil of which is almost made up of the
marl, and it passes from thence in a westerly direction, dipping under
the clay Alluvium near the bathing-place, where it forms part of the
bed of the river Chelmer, and is being denuded by that stream. It
can again be traced disconnectedly under the Alluvium at two places
below the water-mill, and it is worthy of note that the lie of the bed
in all these three cases is athwart the direction of the stream.
There is considerable development of the bed near Seward's Hall,
about a mile N.E. of the village. At the rabbit-warren there, a
section made in draining gave three feet of peat, underlaid by about
three or four feet of shell-marl, which gradually passed down into a
yellowish clay, and at fourteen feet the water-bearing stratum of