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around the lake and the E.N.T. reserve. Several
members reported hearing them, but careful
stalking proved the birds to be reed warblers
which sound rather similar. Presumably the
sedge warblers were present but not observed.
Chris Shennan
RECENT DEVELOPMENTS IN THE PLEISTOCENE GEOLOGY
OF THE IPSWICH AREA, 6th June, 1982
A small party of the Essex Field Club visited the
Ipswich area on 6th June, 1982 to consider recent
developments in the local Pleistocene geology.
Crag
The Red Crag was examined at Waldringfield Heath
to establish a picture of what shallow marine sediments
look like. The strata present were dominantly medium-
scale cross-bedded units, typical of tidal water of
depths of 20-30 m., with abundant marine shells.
Opportunity was taken to collect specimens while in
the pit;. Recent developments suggest that the shallow
marine environment of the Crag Sea continued later
than the time when the Red Crag was deposited. At
Great Blakenham, a thick sequence of flat-bedded sands
and the silty-clay (the Creeting Beds) was examined.
The sequence is now recognised to be typical of tidal
flats such as occur off the north German coast today.
The beds lack the shells typical of the Red Crag, but
pollen obtained from the silty-clay suggests an early
Pleistocene age. Borehole evidence suggests that
these deposits are widespread to the north and east
of Ipswich, but absent to the west, probably indicating
that a shoreline lay across south-east Suffolk.
Possibly this shoreline represents a stand still
during the retreat of the Red Crag Sea which, at its
maximum, extended inland at least to the St. Albans