Interglacial deposits from the Histon road, Cambridge

Abstract

Summary The paper describes the results of the examination of deep sewer trenches in the Middle Terrace of the Cam on the northern outskirts of Cambridge. Extensive aggradation of upwards of 20 feet is indicated by the sequence of organic shelly calcareous muds followed by silt, sand and gravel. The muds and silt yielded abundant molluscan remains and a few mammalian bones, as well as a rich flora. Abundant Corbicula fluminalis at one horizon is a noteworthy feature of the extensive faunal lists based on determinations by the late A. S. Kennard. From an analysis of the proportions of land and fresh-water shells (both numbers of individuals and of species) at several horizons an attempt is made to infer the changing flood-water conditions. Vegetable remains are recorded from several levels. Evidence from both macroscopic remains and from pollen-analysis results, notably the abundance of hornbeam pollen, demonstrates a clear correlation with Jessen's zones f and g associated with the Eemian transgression of the Last Interglacial of North-West Europe. There are indications of brackish water conditions in the flora at one level. There is a striking agreement between the climatic and ecological condition suggested by Kennard from the mollusca, the physical nature of the deposits and the inferences from the flora. It is concluded that this aggradation phase probably represents a marginal phase of the transgression of the Eem Sea in Britain. The implication of the new data on the age of the overlying gravel of the terrace is not discussed and no revision of the Cam sequence is attempted.