4
WALTHAMSTOW MARSHES: A BRIEF POLLEN ANALYSIS
Although not strictly a feature that can be seen, sub-surface natural history allows us to
peek at the past.
Below is a brief summary of part of a study looking at the past environmental change at
Walthamstow Marshes, east London which was carried out last year as part of my thesis
at the Guildhall University (formally City of London Polytechnic).
Remarkably this is the first time that pollen analysis has been applied at Walthamstow. I
hope therefore that this synopsis will be of interest to readers and give my apologies to
those already familiar to the background Quaternary history and for the brevity of account
regarding vegetational change. The observed changes of lithology and the application of a
pollen analysis at Walthamstow Marshes, combined with regional Quaternary histories to
correlate and date underlying sediments, has provided evidence of environmental change
over the past 9,000 yrs BP.
Channels were cut into the Lea Valley floodplain gravels as a result of complex glacio-
eustatic variations at the end of the last ice age. A combination of the downwarping of
regional crustal margins of the Thames basin combined with a series of marine
transgressive/regressive phases led to the infilling of floodplains north and south of the
river Thames with a series of post-glacial sediments, including the Lea Valley at
Walthamstow (Although there are no direct saline conditions connected with the past
rising of the river Thames, tidal 'ponding' of the river Lea did occur).
At Walthamstow marsh a 3.5 metre core was taken of mixed peats, sands and clays
accumulating on the floodplain gravels of late glacial age. This was analysed for pollen
remains in the laboratory. The analysis has provided a record of climatic and vegetational
change from the early Boreal to Atlantic periods.
Evidence is shown of an ameliorating climate by tree assemblages. A gradual change
from pioneer species, such as Betula (Birch), Pinus (Pine) and Corylus (Hazel) was
slowly superseded by the expansion of thermophilous species such as Quercus (Oak)
andTilia (Lime). Of interest is the rapid rise in Alnus (Alder) seen in the Walthamstow
pollen diagram. The rise is considered an important time/indicator horizon for pollen
diagrams in southern England as the climate changed to wetter conditions around 7,000
BP. The chronology follows closely established vegetational changes recorded by other
pollen analysis.
Molluscan remains found in association with the pollens provide further correlation.
Considered as alien species, Helix pomatia (Roman snail) and Helix aspersa (Garden
snail) have neolithic and post-Roman affinities.
If anyone is interested, copies of the full pollen diagram can be made available, a S AE
would be appeciated.
Alyn Pilkington, 11 Downs Ct, Amhurst Road, Hackney, London E8 1AT