Archaeological and historical evidence for subsidence in southern Britain

Abstract

This paper is presented as a warning of the pitfalls which are involved in a too ready and uncritical acceptance of the evidence for apparent changes in relative land and sea level which has been derived from the archaeological and historical remains around the coasts of southern Britain. The general trends of relative sea level changes in the later Holocene are indicated; but I am concerned more to correct some of the misapprehensions and inexact conclusions which have been drawn from the often imprecise data, and to establish a wider recognition of the types of errors and inaccurate assumptions which have been promulgated in some publications, and which erroneously, albeit unwittingly, have been cited by specialists in other disciplines to reinforce or to substantiate conclusions derived from their different data. The optimum conditions for establishing the former positions of relative mean sea level are found in deposits which can be shown to have formed in a known relationship to sea level as part of a continuous halosere from marine sands and clays to freshwater fen deposits (cf. Churchill 1965, p. 240). I would stress that estimates of sea level changes should be based primarily on the analysis of physiographical data; the archaeological and historical data may provide complementary and corroborative evidence of relative land and sea level changes, but they are generally too imprecise to stand alone as definitive indicators of actual mean sea level or tidal heights.

Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK)

“…Archaeological and historical evidence confirms that saltmarshes were extensively developed in southeast England in pre-Romano-British times (Akeroyd, 1972;Greensmith and Tucker, 1980;Kirby, 1990). Since about 200 AD, there has been net submergence and landward movement of the shoreline, albeit with fluctuations (Greensmith and Tucker, 1973).…”

Holocene development of the east bank of the Gironde Estuary: geoarchaeological investigation of the Saint Ciers-sur-Gironde marsh

“…Due to the general unreliability of archaeological sites as sea-level indicators (Akeroyd 1972), the site distribution is used largely to infer patterns of vertical/ horizontal marsh development. However, the nature of human occupation on the St Ciers marsh does have significant implications for sea-level change in the Gironde Estuary.…”

The temporal and spatial development of landslides in the axmouth‐lyme regis undercliffs national nature reserve, Devon

“…The effects of toe erosion and high water tables continue to have an effect on stability, although the relative stabilization of the rate of sea level rise has led to a decrease in the frequency of occurrence of high magnitude events, especially whole-slope events. Both Jelgersma (1961) and Akeroyd (1972) suggest that the current rate of sea level rise level is in the order of 10.0cm per century, and Akeroyd believes that this rate has been operative for the past 6000 years. Therefore the current slope morphologies may indeed have been established a considerable time ago, following the initial post-glacial period of rapid sea level rise.…”