Flandrian sea‐level changes in the Fenland. II: Tendencies of sea‐level movement, altitudinal changes, and local and regional factors

Abstract

Shennan, I. 1986 Flandrian sea-level changes In the Fenland II: Tendencifs of sea-level movement, altitiidina c hanges, and local and regional factors. loonid/ ol Quaternary Science, Vol. 1, pp. 155-1 79. ISSN 0267-81 79 ABSTRACT: Stratigraphic, micropalaeontologic and radiocarbon data show that since c. 6500 BP the Fenland has been influenced by 7 periods of positive sea-level tendencies and by 6 periods of negative sea-level tendencies. Despite the numerous problems associated with the reconstruction of past altitudes of sea level the periods of positive sea-level tendencies were clearly characterised by a rise in sea level, the development of transgressive overlaps and a landward movement of the coastline. The periods of negative sea-level tendencies were characterised by the development of regressive overlaps, a seaward movement of the coastline and a reduced or negative rate of sea-level rise. The various altitudinal errors do not permit the incontrovertible distinction of periods of falling sea levels. All changes within the Fenland were not synchronous and local factors influenced theexact nature of each sea-level indicator. Dominant regional and local factors have been identified for different areas and different time periods. The chronological and spatial characteristics of the sequences within the Fenland are bestexplained by a palaeocoastline without supratidal barriers controlling sedimentation.The data indicate an average crustal subsidence in the Fenland of 0.9 m/l 000 years since c. 6500 BP and the pattern of positive and negative tendencies of sea-level movement is also seen in the chronologies for north west England and north east Scotland. Journal of Quaternary Science

Application of stable carbon isotopes for reconstructing salt‐marsh floral zones and relative sea level, New Jersey, USA

“…This distinctive pattern provides a means to reconstruct relative sea level by recognition of these floral zones in coastal sedimentary archives where organic material has accumulated, such as salt marshes, infilled lagoons and estuaries (Shennan, 1986). To do so, requires that the elevational range of each floral zone can be robustly estimated from modern salt marshes.…”

“…The precision of this approach may be increased if salt marshes can be further divided using δ 13 C values into floral zones (high and low salt marsh) characterized by varying proportions of C 3 and C 4 inputs (Edwards, 2007). To be used as a sea-level indicator, it is necessary to quantify the relationship between bulk sediment δ 13 C values (or the vegetation types they represent) and elevation in the tidal frame (Shennan, 1986;van de Plassche, 1986). This relationship is formalized by the indicative meaning, which is the elevational range occupied by a sea-level indicator (indicative range) in relation to a contemporaneous tide level (reference water level).…”

Holocene drainage systems of the English Fenland: roddons and their environmental significance

“…This may in part have been diachronous across the Fenland (Hall, 1987;French, 2003). Dates for this earliest marine incursion range from ca 4200-3300 yr BP (Shennan, 1986b;French and Pryor, 1993). The first generation of roddons formed at or near the end of deposition of these Lower Barroway Drove Beds clays.…”

Reconstructing relative sea-level change using UK salt-marsh foraminifera

“…A multi-proxy approach employing radiocarbon-dated lithostratigraphic and biostratigraphic sea-level indicators is routinely used to establish a series of sea-level index points (SLIs) that fix the former positions of RSL in terms of age and altitude. Errors associated with the precise determination of this age and altitude information require these data to be plotted as a band of sea-level change, representing the generalised course of variations in RSL throughout the study period (Shennan, 1986). These limitations become increasingly problematic as the temporal scale of the investigation is reduced from examining changes occurring during the Holocene period as a whole, to studying fluctuations during the last two or three millennia, and ultimately the error band becomes of comparable magnitude to the sea-level variations of interest.…”