The Fenland of East Anglia is the largest area of Holocene deposits in Britain (c. 4000 km[superscript 2]) and some successions reach a thickness of 30 m. A complex palaeoenvironmental landscape has been progressively revealed as the overlying peat has wasted away to reveal exceptionally preserved roddons. Roddons are defined as dendritic ridge systems, up to 1 m high, that meander across Fenland areas. They are interpreted as being the surface expression of silted-up tidal creeks. Three generations of East Anglian roddons have been identified, each being related to a major “transgressive” event between about 2000 and 6000 yrs BP. Soon after the tidal creeks and channels had been established, they were choked by sediment (silts and fine sands) derived from a nearby shallow marine environment, perhaps following major (storm-induced?) physiographic changes. The final stage in their formation occurred after 17th century Fenland drainage, with compaction, shrinkage and wind ablation of the surrounding salt marsh clays and peats, leaving the more resistant channel infill as topographic highs. Roddon deposits contain rich assemblages of autochthonous, low marsh foraminifera with rarer ostracods (together with allochthonous taxa and fossils reworked from bedrock); assemblages differ from trunk to tributary roddons. A late-stage channel incised into a roddon at Must Farm, near Peterborough, is filled predominantly with clays containing freshwater ostracods and molluscs, together with riparian archaeological remains. This freshwater channel, therefore, represents a distinctly different palaeoecological regime compared to that of the roddons. Any future marine transgression will take place across an anthropogenically modified Fenland where the topographically positive roddons will act as barriers and islands that will affect marine ingress.

Given that recent anomalous positive values in the North Atlantic Oscillation (NAO) may be related to anthropogenic forcing, the need exists to document more fully NAO evolution in palaeoclimate records. To this end, this thesis investigates whether NAO-type variability can be identified in biochemical varves of mid- to late-Holocene age from a lake sediment sequence in Diss Mere, UK. The varved record was examined using a number of cutting-edge technologies, with an emphasis placed on the time-series analysis approach to determine spectral properties of high-resolution palaeo-environmental time-series constructed from laminae-thickness measurements (a palaeoproductivity indicator) and XRF core-scanning for inter-annual records, principally, of elemental Ca-abundance, a proxy for summer temperature. For comparison, a low-resolution record of organic carbon burial was taken to record change in winter temperature. The in-situ chemical, biological and clastic constituents of individual varves were also examined using SEM-BSEI to investigate the annual cycle of sedimentation and variety of varve-fabric types. The results indicate that varve deposition is characterised by statistically significant interannual and bidecadal cycles that correspond to periodicities found in instrumental and other proxy records of the NAO. A shift from interannual to bidecadal cycles after 4000 Cal. BP is coincident with a rapid transition at Diss towards decreased seasonality during the late-Holocene that is also reflected in a distinct change in varve character and phytoplankton dynamics. This appears comparable, if not analogous, to the evolution of the modern NAO where a dominance of decadal variability since the 1950s is coincident with a tendency towards an NAO positive. It is hypothesised that change at 4000 Cal. BP and seasonality cycles thereafter have implications for the degree of longer-term predictability that may exist in the mean state of the NAO due to forcing by solar activity and orbital precession.

No description available.

Λεπτομερείς τοπογραφικές έρευνες για τη στρωματογραφία του Ολόκαινου σε συνεργασία με τη μελέτη ενός σπουδαίου αριθμού από αρχαιολογικές ανακαλύψεις, οι οποίες παρέχουν πολύτιμες πληροφορίες για μία καλύτερη κατανόηση της σχέσης ανάμεσα στους ανθρώπους και της περιβαλλοντικής εξέλιξης. Κατά τη διάρκεια του πρώιμου Ολόκαινου, οι ανθρώπινες δραστηριότητες ήταν επηρεασμένες σε μεγάλο βαθμό από περιβαλλοντικές κλιματικές αλλαγές, όπως αποδείχτηκε από τα εύρηματα θαμμένων αρχαιολογικών τοποθεσιών στις ποτάμιες αποθέσεις της κοιλάδας του ποταμού Βουραϊκού. / Detailed field investigations of Holocene stratigraphy in combination with the study of an important number of archaeological discoveries provided valuable information for a better understanding of the relationship between man and the environmental evolution. During Early Holocene, human activities were strongly influenced by climate-induced environmental changes, as proven by the occurrence of archaeological sites buried within the alluvial depos-its of the Vouraikos river valley.

Geomorphological evidence has frequently been used to infer past environmental conditions, but in recent years the emergence of landscape evolution models (LEMs) has opened the possibility of us- ing numerical modelling as a tool in palaeo-environmental reconstruction. The application of LEMs for this purpose involves retrodictive modelling, each simulation scenario being congured with model variables (e.g. reflecting climate change) and parameters to reflect a specic hypothesis of environmental change. Plausible scenarios are then identied by matching contemporary observed and modelled landscapes. However, although considerable uncertainty is known to surround the specication of model driving conditions and parameters, previous studies have not considered this issue. This research applies a technique of accounting for the uncertainty surrounding the speci- cation of driving conditions and model parameters by using reduced complexity 'metamodels' to analyse the full model parameter space and thus constrain sources of uncertainty and plausible retrodicted scenarios more eectively. This study applies the developed techniques to a case study focused on a specic set of coastal gullies found on the Isle of Wight, UK. A key factor in the evolution of these gullies are the relative balance between rates of cliff retreat (which reduces gully extent) and headwards incision caused by knickpoint migration (which increases gully extent). To inform the choice and parameterisation of the numerical model used in this research an empirical- conceptual model of gully evolution was initially developed. To provide a long-term context for the evolution of the gullies and to identify the relative importance of the various driving factors, the Holocene erosional history of the Isle of Wight gullies was then simulated using a LEM. In a preliminary set of simulations a 'traditional' (i.e. with no consideration of parameter uncertainty) retrodictive modelling approach was applied, in which driving variables were arbitrarily altered and observed and simulated landscape topographies compared, under various scenarios of imposed environmental change. These initial results revealed that the coastal gullies have been ephemeral in nature for much of the Holocene, only becoming semi-permanent once cli retreat rates fall below a critical threshold at 2500 cal. years BP. Next, in an attempt to constrain more detailed erosional histories and to explore the extent to which retrodicted interpretations of landscape change were confounded by uncertainty, a Central Composite Design (CCD) sampling technique was employed to sample variations in the model driving variables, enabling the trajectories of gully response to dierent combinations of the driving conditions to be modelled explicitly. In some of these simulations, where the ranges of bedrock erodibility (0:03-0:04m0:2a).