Geoscience Reference
In-Depth Information
linked to long-term variations in the general circulation which could be investi-
gated in a novel and useful way by the reconstruction of past circulation patterns.
As with his innovative ideas in the business world, Harmer's application of
palaeometeorological
methods
to
geology
again
illustrates
his
pioneering
endeavours—this time in science.
He questioned that although in speculations about the causes of anomalous past
climates, especially those of the Pleistocene epoch, geologists had recognised the
crucial role played by ocean currents, as well as the influence of winds upon the
latter, they had seldom questioned how climatic changes may have also been
driven by variations in the wind flow itself, that is, by changes in past circulation
patterns.
Harmer believed that by combining findings of geology and meteorology, past
circulation patterns could be determined which would provide an effective means
for solving certain geological problems. Anomalous past climates, he believed,
could only have occurred when atmospheric situations prevailed which were
different from those normally experienced in the present period.
His attention had been drawn to palaeometeorology by chance when endeav-
ouring to solve an outstanding geological problem, namely, the meteorological
conditions under which the Crag deposits of East Anglia had been laid down.
Some of these beds originated as littoral accumulations during the Pliocene on the
western margin of the proto-North Sea, termed the Crag Sea. Comprising a
mixture of sand and molluscan shells these deposits are found today in a more or
less continuous line of land-locked strata in the cliffs of the East Anglian coast; 2
million years ago the shore-line of the Crag Sea extended further west than that of
the present North Sea.
4.2 The Red Crag
Harmer was particularly interested in the Red Crag formation, a shore-line deposit
comprising a succession of beds varying in thickness up to about 6 m (20 ft) with
laminae of sands and shells inclined at a high degree to the horizontal. He had
discovered that the molluscan shells of these deposits are seldom found today on
the shores of East Anglia and that one may walk for miles along the beaches of the
region without finding more than a chance specimen. However, this is not due to
any absence of such molluscan life in the adjoining sea which Harmer, assisted by
his son, Sidney, had ascertained by dredging.
Accordingly, he inferred that the meteorological conditions under which the
Red Crag was deposited must have differed from those prevailing today and
suggested that easterly rather than westerly winds may have prevailed over East
Anglia and the southern North Sea in the earlier period. Investigating the matter
further, he ascertained, during a visit to Holland, that the beaches there were, in
places, plentifully strewn with molluscan shells, probably comparable in amount
and extent with those that had accumulated in East Anglia during the late Pliocene.
