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The Anglian Cold Stage in Essex - a review
PETER ALLEN
13, Churchgate, Cheshunt, Hertfordshire EN8 9NB
Abstract
The Anglian cold stage occurred within, creation of now deeply buried valleys and
and interrupted, a period of nearly two deposition of an extensive sheet of till
million years (the Quaternary) of fluvial (boulder clay) which covers much of the
geological activity in Essex. During the county. More geological change was
Anglian Essex experienced tundra desert achieved in a period of less than 100,000
and possibly humid tundra conditions, years than in the rest of the Quaternary.
major disruption of the river systems, Essex has provided much crucial evidence
establishment of the modern Thames, for our knowledge of the period.
Introduction
The Quaternary covers approximately the last two million years, though its lower boundary is
the subject of controversy. The majority of the period is taken up by the Pleistocene, but the last
10,000 years is known as the Holocene or Flandrian. Putting limiting dates on the Anglian cold
stage is difficult as dating methods lose precision at such long ranges and different, not fully
compatible, methods have been used. Broadly, the preceding temperate period, Oxygen Isotope
Stage 13 (late Cromerian Complex) (Fig. 1). is dated at ca. 500,000 years ago. but dates for the
succeeding warm stage, the Hoxnian, are variously given as 470,000 and 400,000 years ago (cf.
Bowen, 1999). Thus the duration of the Anglian cold stage may have been as short as 30,000
years or have approached 100,000 years. The longer duration is favoured. From oxygen isotope
variation recorded in oceanic sediments, it is known that temperatures slowly declined from
Oxygen Isotope Stage (OIS) 13 to reach their coldest late in the stage, before rapidly improving
for the Hoxnian (OIS 11). Mean annual temperatures for much of the cold stage were low, but
the sedimentary evidence, as detailed below, shows that for much of the time there is no
indication of glacier advance and that periglacial conditions prevailed. The glacial phase
appears to be a relatively short-lived event towards the end of the cold stage.
History of Research
Essex has a significant history of research into the Pleistocene and in particular into the Anglian.
However, due to very significant increases in our knowledge of fluvial and glacial processes,
much early work relevant to the Anglian is no longer accepted, though the conclusions reached
at the time were appropriate.
The sands and gravels underlying the Essex tills were for a long time thought to be glacial
outwash due to their rich erratic content, particularly quartz and quartzite (up to 30%), but also
small amounts of Carboniferous chert, schorl, and various igneous and metamorphic rocks.
However, detailed stone counts (Rose. Allen and Hey, 1976; Rose and Allen. 1977; Rose et al.,
1999) showed significant differences between these gravels, now recognised as the Kesgrave
Formation, and known glacial outwash. In particular the latter had Rhaxella chert and more
(sub-) angular flint. Also an interglacial fossil soil (the Valley Farm Soil) was
recognised
Essex Naturalist (New Series) 16 (1999)