Geoscience Reference
In-Depth Information
5.2 Volume II
In September 1924, due to Harmer's death the previous year, Alfred Bell of the
Ipswich Museum undertook the writing of the Preface to this Volume in which he
included the following remarks:
The late author of this Monograph realized his wish to complete his account of the
Pliocene Gasteropoda before his death, which occurred on April 11th, 1923. Part III of his
second volume had been passed by him for press several months before its publication,
and the fourth and concluding part was also ready. An Index to the second volume had
been compiled by him, but Sir Arthur Smith Woodward has kindly undertaken to have this
work done independently, in order to assure the accuracy which is so important in an
Index.
Mr. Harmer had intended to express his sincere thanks to all those friends at home and
abroad who had helped him in difficulties by the loan or gift of specimens for comparison,
or by the determination of critical forms. This duty he left for his son, Sir Sidney Harmer,
and myself to carry out, in his name and for him.
5.3 General Remarks
In geology, Crag is the collective term given to the sandy, shelly Pliocene deposits
which comprise the principal Tertiaries of East Anglia laid down about 2 million
years ago under marine and later estuarine conditions. Patches of the Red Crag
have survived in northeast Essex at Dovercourt, Beaumont, Wrabness and Little
Oakley. In the 19th and early 20th centuries sand pits at these sites yielded fossils,
one of the most well known sites was a shallow pit at Little Oakley that was
investigated by Harmer who, in his later years, sifted and examined its sand for
fossil shells. As a result, 650 different species of mollusca and about 100 speci-
mens of polyzoa were found in this one pit alone (nearly 400 of the species
illustrated in his monograph were from the Little Oakley pit).
Harmer's meticulous research has shown the extraordinarily rich mollusca
fauna of the Crag Sea which existed over northeast Essex and East Anglia about 2
million years ago. He was aware that the Red Crag formation was deposited in
near-shore conditions during the Pliocene as part of a large delta that was building
out into the southern part of the Crag Sea which, at that time, extended into the
London Basin as far west as Hertfordshire, where a proto-Thames flowed into it.
Although this Crag Sea or proto-North Sea was connected to the Atlantic across
southern Britain it was not through the English Channel as it is known today.
However, this early sea link was slowly reduced and by about 2 million years ago
not only was it lost but the head of the delta between Britain and mainland Europe
