Jason R. Kirby

Holocene sea-level change and coastal evolution in the Humber estuary, eastern England: an assessment of rapid coastal change

New stratigraphic data collected from six sites in the Humber estuary establish a record of Holocene relative sea-level (RSL) change, and enable testing of four possible causes of rapid coastal change: sea-level rise, changes in sedimentation, storm-surge history, and human impact. Mean high water of spring tides (MHWST) in the Humber rose from c. 9 m OD at 7500 cal. yrs BP to 0 m OD by 4000 cal. yrs BP, at an average long-term rate of c. 3.9 mm yr-1. After this, the rate of rise gradually decreased to c. 1 mm yr’. Discrete episodes of rapid RSL rise are not identified although their absence may reflect limited data availability. However, we do observe two episodes of rapid coastal change in the Humber estuary. The first occurs between c. 3200 and 1900 cal. yrs BP, as marine conditions expand to their Holocene maximum and then contract. This pattern of coastal development differs from that in the East Anglian Fenlands, suggesting local processes control sedimentation at one or both of these sites. The second period of rapid change relates to a well-documented episode of increased storm surge activity in the Humber estuary and elsewhere in the UK and the North Sea region between c. 700 and 500 cal. yrs BP. Coastal development during this period varies considerably with erosion, accretion and flooding in different parts of the estuary system. Finally, we examine evidence for accelerated sediment delivery to the Humber estuary due to woodland clearance and prehistoric agriculture from 5700 cal. yrs BP onwards. Maximum sediment input is likely at c. 3200 to 1900 cal. yrs BP; a period which tentatively correlates with an episode of estuary infilling and shoreline advance.

Holocene relative sea-level changes in the inner Solway Firth

Abstract Bio- and lithostratigraphic data from four sites from the inner Solway Firth allow an accurate reconstruction of Holocene RSL changes in the estuary. Radiocarbon assays give eleven new sea-level index points providing a total of 24 reliable index points for the inner Solway Firth. These data show a consistent pattern of rapid RSL rise during the early Holocene culminating in a mid-Holocene sea-level maximum, then a gradual fall to the present day level. Detailed analysis of this dataset quantifies for the first time differential crustal movement between the north and south shores of the Solway Firth. These data are used to test the accuracy of quantitative isostatic rebound models of Lambeck and Peltier, and show there is good general agreement between the data and the models, especially during the early Holocene. The models predict the mid-Holocene sea-level peak slightly later than shown by the data (c. 500 and c. 2000 yr), this may be partly due to lack of resolution in the models, and for the south Solway the maximum altitude at this peak is ∼1 and ∼2.5 m too high in the two models. The data are also compared to the isobase models of the Main Postglacial Shoreline, showing slight diachroneity between the north and south shore but otherwise general agreement with the postulated age, and indicating that the altitude of this feature is 1–3 m higher than suggested by the models.

The litho- and biostratigraphy of a late Holocene tidal channel in Romney Marsh, southern England

The evolution of tidal channels and, in particular, the sedimentological and biostratigraphic evidence for channel infilling, are areas of palaeoenvironmental research that have received relatively limited attention in stratigraphic studies aimed at landscape reconstruction. This paper details the results of a multidisciplinary investigation into the late Holocene evolution of the Wainway, a large tidal channel in Walland Marsh, East Sussex. Lithostratigraphic, microfossil and sedimentological data, as well as geomorphological and historical evidence detail the rapid infill of this channel between the tenth and sixteenth centuries. This infilling was associated with localized changes in coastal configuration caused by storm events. Our analyses suggest that the channel sediments provide a detailed insight into the dynamics of this important watercourse during the closure of the New Romney tidal inlet and the opening of a tidal inlet at Rye during this period. The final stages of sedimentation within the Wainway Channel record its progressive infilling and final inning at c . ad 1600. This is reflected in the sedimentological and micropalaeontological data by a progressive upward fining of the sediment sequence and the development of low energy mudflat and saltmarsh conditions. In this study we find significant differences in the usefulness of different microfossil groups for palaeoenvironmental interpretation. In particular, the foraminiferal data provide a more continuous and sensitive record of changing intertidal conditions compared with the diatom record.

The Distribution Of Contemporary Saltmarsh Foraminifera In A Macrotidal Estuary: An Assessment Of Their Viability For Sea-Level Studies

An analysis of dead benthic foraminiferal assemblages and associated environmental variables is presented to establish the controls on species distribution and zonation on two macrotidal saltmarshes in the Mersey estuary with the aim of evaluating the use of foraminifera in reconstructing past sea levels. The combined results from five contemporary transects from two sites illustrate that where there is a sufficient elevational range, foraminifera distribution and zonation shows a good relationship with altitude, with a high-to-middle marsh zone characterised by Haplophragmoides wilberti , Jadammina macrescens, and Miliammina fusca, and a low marsh zone composed of similar agglutinated species with calcareous species including Brizalina spp., Elphidium spp., and Haynesina spp. Cluster analysis and partial Redundancy Analysis (pRDA) reveals that the elevational control decreases with respect to other environmental variable inter-correlations when the sampling elevation range is reduced. It is proposed that this is a key issue for macrotidal environments when the contemporary sampling range represents a small proportion of the spring tidal range (i.e. <10%). Limiting the contemporary dataset to agglutinated species only, a tidal level transfer function can be obtained which offers acceptable predictability and precision (r2jack = 0.79, RMSEPjack = 0.13 m) for the reconstruction of past sea level.

Combining Palaeoecological and Historical Approaches to Investigating Post-Medieval Land Use Change at Sandford Mire, Cumbria, North West England, UK

Abstract Sandford Mire in western England provides a case study of how peat core based evidence and historical records can be combined to investigate the post-medieval history of a landscape. Data on pollen, testate amoebae and various aspects of peat sedimentology are combined with historical maps and written sources to elucidate the environmental history of the site. The peat core data allows additional detail to be added to the history described in the archival sources. In particular, these records identify what appears to be significant soil erosion. We suggest this may be associated with enclosure ploughing which is not described in local historical documents and adds significantly to the eighteenth-century agricultural history of the area. In addition the peat core evidence adds other details to the known historical record – such as the probable use of barley as a crop, the scrub growing on the mire surface during the eighteenth and early nineteenth century and inferred increases in twentieth-century grazing; as well as mire surface fires possibly associated with the opening of the nearby railway line in the mid-nineteenth century. The proxy data from our core also helps confirm some details recorded in the text sources, such as drainage and a drier mire surface in the second half of the twentieth century and helps identify the role of changes in grazing pressure on the bogs vegetation – which has the potential to inform future conservation management.