Interglacial deposits at Ilford, Essex

Abstract

At Ilford, Essex, organic sediments have been found beneath the brickearth, long famous for its rich mammalian fauna. Pollen analysis shows that these organic sediments and the lower part of the overlying brickearth were deposited during the Ipswichian (Last) Interglacial. The pollen diagrams show the vegetational succession typical of the first half of the interglacial, with pollen zones b, c, d, e and f, which cover the early treeless part of the interglacial and the change to forested conditions with Pinus and Quercus. The rich flora of macroscopic plant remains indicates that a climate with summers warmer than now obtain in the area prevailed probably in zone c and more certainly in the later zones. Analyses of the macroscopic plant remains and the non-marine Mollusca demonstrate that the organic deposits were formed in a large pond or a small stream, tributary to the Thames at that time. A rising base level, probably resulting from the rise in sea-level known to occur in zone f of the interglacial, caused the Thames floodplain to extend over the organic deposits, and brickearth was deposited up to a height of 42 ft. O.D. at least. The surface of the brickearth was contorted by cryoturbation during the Weichselian (Last) Glaciation. The Ilford temperate deposits are correlated with temperate fossiliferous deposits at Little Thurrock (Grays), and more tentatively, with temperate fossiliferous deposits at Erith, Crayford and Ebbsfleet. The consequences of the dating of the Ilford brickearth to the Ipswichian Interglacial for the terrace succession of the lower Thames valley are considered.