New approaches to mapping and managing palaeochannel resources in the light of future environmental change : a case study from the Trent Valley, UK

Abandoned river channels may provide rich primary sources of palaeoenvironmental and cultural information elucidating landscape evolution, climate change, vegetation history and human impact, especially since the beginning of the Holocene epoch. However, although potentially an important resource, palaeochannels are not often recorded systematically and only rarely enjoy robust statutory protection (in the UK as Sites of Special Scientific Interest). In consequence, it is challenging to mitigate and manage this important geoarchaeological resource effectively within the UK planning framework. Whilst palaeochannels have long been recognised on aerial photographs and historic maps, the advent of airborne laser scanning (Lidar) and other remote-sensing technologies has provided a hitherto unforeseen opportunity to record such landforms and related features at a catchment scale. This paper provides a case study from the Nottinghamshire reach of the Trent Valley, where a desk-based methodology that is now being extended across the entire catchment has been developed for recording, geospatially locating and defining the attributes of observed palaeochannels. After outlining the methodology, we consider how this approach to resource management can aid archaeological research and future heritage management, especially in the light of predicted climate and environmental change

Using legacy data to reconstruct the past? Rescue, rigour and reuse in peatland geochronology

There is a growing interest in the rescue and reuse of data from past studies (so-called legacy data). Data loss is alarming, especially where natural archives are under threat, such as peat deposits. Here we develop a workflow for reuse of legacy radiocarbon dates in peatland studies, including a rigorous quality assessment that can be tailored to specific research questions and study regions. A penalty is assigned to each date based on criteria that consider taphonomic quality (i.e., sample provenance) and dating quality (i.e., sample material and method used). The weights of quality criteria may be adjusted based on the research focus, and resulting confidence levels may be used in further analyses to ensure robustness of conclusions. We apply the proposed approach to a case study of a (former) peat landscape in the Netherlands, aiming to reconstruct the timing of peat initiation spatially. Our search yielded 313 radiocarbon dates from the 1950s to 2019. Based on the quality assessment, the dates—of highly diverse quality—were assigned to four confidence levels. Results indicate that peat initiation for the study area first peaked in the Late Glacial (~14,000 cal years BP), dropped during the Boreal (~9,500 cal years BP) and showed a second peak in the Subboreal (~4,500 cal years BP). We tentatively conclude that the earliest peak was mostly driven by climate (Bølling–Allerød interstadial), whereas the second was probably the result of Holocene sea level rise and related groundwater level rise in combination with climatic conditions (hypsithermal). Our study highlights the potential of legacy data for palaeogeographic reconstructions, as it is cost-efficient and provides access to information no longer available in the field. However, data retrieval may be challenging, and reuse of data requires that basic information on location, elevation, stratigraphy, sample and laboratory analysis are documented irrespective of the original research aims

Planform architecture, meander evolution and grain-size variability of a deltaic channel belt in the Rhine-Meuse delta, The Netherlands

In the unconstrained, low gradient setting of major delta plains, individual meander belts tend to function for relatively short periods of time due to repeated channel avulsion. Their short lifetime makes ‘deltaic’ channel belts suitable to study the products of steady meander evolution as the deposits and internal architectural elements preserved are often without complications of repeated bend cutoffs. This study investigated how sedimentary characteristics as preserved from subsequent stages of activity differ within the Stuivenberg channel belt. The Stuivenberg channel belt is a long-studied example in the Holocene Rhine-Meuse delta, The Netherlands, for which the meander evolution, i.e. geometry and dimensions through initiation, main activity and abandonment stages and durations of activity involved, was reconstructed. Mapping of the channel belt started from established coring based and LiDAR-aided methods. Explorative approaches were used to assess active channel width at the onset of abandonment, and to reconstruct meander positions during earlier stages. The migration history of five consecutive meanders is revealed from convex and concave ridge-and-swale scrolls. Analysis identifies them to be the product of translation, expansion and rotation trajectories during a period of 800 years. Grain-size composition throughout the sand body is interpreted given these positional contexts, with special attention to local coarsening of upper point bar facies in deltaic meander belts. The findings emphasize: (i) the need to separate abandonment stage from main activity stage when analysing three-dimensional channel belt architectures; and (ii) the influence of meander evolution on lithological characteristics of initial stage versus mature stage parts of deltaic channel belt sands

Late Holocene ecological shifts and chironomid-inferred summer temperature changes reconstructed from lake Uddelermeer, the Netherlands

This paper presents a Late-Holocene chironomid-inferred July-air temperature record from a core obtained from Lake Uddelermeer in the Netherlands. A core interval, which dates from 2500 to 400 cal. yr. BP, was analysed at multidecadal resolution for organic content, pollen, spores and NPPs (Non Pollen Palynomorphs), and chironomid head capsules. These proxies indicate that, from 2500 to 1140 cal. yr. BP, the lake was mesotrophic and sustained a Littorellion, while the chironomid assemblage was dominated by littoral species associated with macrophytes. At 1140 cal. yr. BP a shift in the lake ecology occurred from low-nutrient to high-nutrient conditions dominated by algae. This shift might be linked to a concurrent increase in human impact and is reflected in the chironomid assemblage by increases in eurytopic taxa, which are resistant to disturbances. Shifts in the chironomid record between 2500 and 1140 cal. yr. BP do not coincide with changes in lake ecology and are presumably driven by climate change. Using a Norwegian-Swiss calibration dataset as a modern analogue, we produced a chironomid-inferred temperature (C-IT) reconstruction. This reconstruction compares well to other regional temperature reconstructions in timing and duration with a Roman Warm period between 2240-1760 cal. yr. BP, a Dark Age Cold Period starting at 1760 cal. yr. BP and the Medieval Climate Anomaly beginning at 1280 cal. yr. BP. The C-IT record indicates a temperature drop of 1.5°C from the Roman Warm Period to the Dark Age Cold Period. Findings improve knowledge of the first millennium AD in NW Europe, which was characterised by changes in landscape, vegetation, society and climate

After the deluge

After World War II huge land consolidation projects measuring thousands of hectares were carried out in West-Frisia. Large scale excavations of Bronze Age settlement sites were carried out resulting in a convincing model for the Bronze Age habitation of West-Frisia. This model envisaged settlement sites situated on creek ridges in an open almost treeless landscape. After a sudden change in climate c. 800 cal BC parts of the landscape were inundated, peat bogs developed and West-Frisia was abandoned by man. It was widely believed that this densely inhabited Bronze Age landscape was almost completely destroyed during the land consolidation projects. At the start of this century, however, it turned out that well preserved Bronze Age settlement sites still exist in West-Frisia. These sites were not only well-preserved but also situated at unexpected locations. The excavation results also gave reason to think of the presence of woodlands and forests during the Bronze Age. This thesis tries to unite the excavation results from the period of land consolidation and those of the later development led projects. In this thesis the palaeogegraphy is described at three scale levels. West-Frisia, the land consolidation project of Westwoud and several settlement sites. Based on an analysis of excavation results and environmental proxy data, a new model for the development of the landscape and habitation of West-Frisia during the Bronze Age emerges. For the construction of the palaeogeographical maps of Westwoud, a new approach is used, based on, amongst others, macro botanical remains. The thesis concludes with an alternative strategy for the prospection of Bronze Age sites in West-Frisia. This thesis is of interest for anyone who is professionally interested in the habitation history of West-Frisia and people who are professionally engaged with palaeogeographical and vegetation reconstructions

Deltaic Sedimentary Environments in the Niger Delta, Nigeria

Chinotu Franklin George would like to thank his sponsor: Petroleum Technology Development Fund (PTDF) and SPDC Port Harcourt for providing the satellite images used. He expresses his gratitude to his mentors: Dr. K. O. Ladipo and late Professor L. C. Amajor, and to Ms. Okwuchi Omekara for the technical support, she offered for data assembly.Peer reviewedPostprin

Palaeogeographical changes in response to glacial–interglacial cycles, as recorded in Middle and Late Pleistocene seismic stratigraphy, southern North Sea

Offshore stratigraphic records from the North Sea contain information to reconstruct palaeo‐ice‐sheet extent and understand sedimentary processes and landscape response to Pleistocene glacial–interglacial cycles. We document three major Middle to Late Pleistocene stratigraphic packages over a 401‐km2 area (Norfolk Vanguard/Boreas Offshore Wind Farm), offshore East Anglia, UK, through the integration of 2D seismic, borehole and cone penetration test data. The lowermost unit is predominantly fluviatile [Yarmouth Roads Formation, Marine Isotope Stage (MIS) 19–13], including three northward‐draining valleys. The middle unit (Swarte Bank Formation) records the southernmost extent of tunnel valley‐fills in this area of the North Sea, providing evidence for subglacial conditions most likely during the Anglian stage (MIS 12) glaciation. The Yarmouth Roads and Swarte Bank deposits are truncated and overlain by low‐energy estuarine silts and clays (Brown Bank Formation; MIS 5d–4). Smaller scale features, including dune‐scale bedforms, and abrupt changes in cone penetration test parameters, provide evidence for episodic changes in relative sea level within MIS 5. The landscape evolution recorded in deposits of ~MIS 19–5 are strongly related to glacial–interglacial cycles, although a distinctive aspect of this low‐relief ice‐marginal setting are opposing sediment transport directions under contrasting sedimentary process regimes

Landscape response to glacial-interglacial cycles: insights from a southern North Sea offshore wind farm dataset

Landscape evolution during periods of Quaternary climate change can be reconstructed using integrated subsurface datasets acquired by the offshore wind industry. Reconstruction of landscapes that evolved during changes in past climates aid understanding the responses to future changes in climate. The bathymetry of the southern North Sea region makes it an attractive location for wind farm developments. The integration of a dense 2D grid of seismic reflection data, with sedimentological and geotechnical data, allow detailed documentation of depositional environments and landscape evolution from the Middle Pleistocene to present day over a 1040 km2 area. The stratigraphic architecture records multiple phases of transgression and regression linked to multiple glacial-interglacial cycles and relative sea-level change. Middle Pleistocene stratigraphy (MIS 19-13) reveals a predominantly fluviatile depositional environment, with northward draining river valleys that are filled with a seismic architecture that support changing depositional environments from terrestrial to marginal marine. North-south orientated tunnel valleys provide evidence for subglacial conditions and southwards drainage, most likely during the Anglian stage (MIS 12). During the late Pleistocene (MIS 5d-2), a regressive stratigraphy is preserved, with geomorphology and stratigraphy recording multiple fluctuations in relative sea level in an overall low energy setting. Late Devensian postglacial stratigraphy reveals a terrestrial landscape with southward draining fluvial networks contemporaneous with peats that formed in freshwater wetlands. Early Holocene geomorphological features record marine transgression across a low relief coastal plain. Carbon stocks of postglacial peats are estimated and upscaled for the southern North Sea (726 Mt). The peats crop out on the seabed, and their susceptibility to reworking is considered. The landscape evolution of the study area has revealed abrupt and opposing drainage directions, subglacial conditions, and postglacial marine transgression. Subtle topographic relief is a primary control on sedimentary process, and stratigraphic preservation. Improved 3D understanding of the subsurface has direct commercial application to the offshore wind industry, and for informing understanding of landscape response to changing climate