TWO LACUSTRINE DEPOSITS IN THE SOUTH OF THE ENGLISH LAKE DISTRICT

Authors


  • *

    Now at the Nuffield Quaternary Research Unit, Queen's University, Belfast.

Summary

It is shown that the lowermost deposits at Helton Tarn and at the former lake near Witherslack Hall, Westmorland, date from Late-glacial times and that zones I, II and III correspond roughly to layers of laminated clay, clay mud, and clay, respectively. There is little evidence for solifluction in zone III. Pollen analysis reveals a Late-glacial flora comparable with floras of similar date which have already been described. A minor oscillation, in which herb pollen becomes predominant over tree and shrub pollen, occurs at both sites during zone II. At Helton Tarn some of the pollen types characteristic of the Late-glacial period occur sporadically until Boreal and Atlantic time; at both sites pollen of those weed and ruderal types which are plentiful in the early deposits constantly recurs throughout Post-glacial time.

Stratigraphical and pollen analytical evidence suggests that at the maximum of the early Post-glacial marine transgression, the sea overflowed a rock bar that is now at about + 5 m. O.D. into the Helton Tarn basin and laid down a layer of clay during the earliest part of Atlantic time.

In contrast to the findings of Walker (1955a), at the sites investigated, Finns appears to have been relatively successful in Boreal time and Tilia pollen, although not appearing until early Atlantic time, is present in quantity throughout most of post-Boreal time. The relatively high proportion of Tilia pollen suggests that the lime was growing as far north as southern Westmorland in post-Boreal time.

At the opening of the Sub-boreal period, at the first decline of Ulmus pollen, the presence of small amounts of Plantago lanceolata pollen is taken to indicate the first agricultural activity in the region.

Ancillary