Insect faunas of late Devensian and Flandrian age from Church Stretton, Shropshire

Abstract

Invertebrate faunas consisting mainly of insects, from deposits in the Church Stretton valley, are described and discussed. These deposits fall into two periods: (a) Late Devensian, which follows an episode of glaciation and precedes a period of accumulation of frost-shattered gravel fans; and (b) Flandrian, which post-dates the gravels and has been placed in the post-Glacial pollen zones VI and VII. The faunas of these two episodes are dealt with separately in Parts I and II respectively. Part I. From two sites in which sequences containing clays, peats and silts were examined five radiocarbon dates are available, the oldest being 13 555 ± 620 years B.P. and the most recent 11 000 ± 200 years B.P. The faunas include a substantial number of species not now found in Shropshire, many not in Britain. Inferences on the changing ecology and thermal environment of the area are drawn from these faunas and are compared with the pollen analytical zones. This comparison shows that, according to the insects, the warmest part of the episode was late zone I, and that zone II (the Allerod), often considered to be the climatic optimum of the period, appears to have been a time of gradually deteriorating summer temperatures. Part II. Deposits from three late Flandrian sites are discussed. Although only one radiocarbon date was obtained, of 8101 ± 138 years B.P., pollen analysis was carried out by Rowlands throughout each sequence and this showed that the earliest deposit, at Little Stretton, dated from zone VI a and at all three localities deposition continued into zone VII b. An examination of the insect assemblages shows that completely different biotopes, from open pasture to dense woodland, were existing side by side in the Church Stretton valley in late Flandrian time. Summer temperatures at least as high as those of today are inferred. The possibility exists that during the period represented here the climate was even warmer than that of the present but until more information is available it is not possible to be more definite on this point.