Flandrian sea-level changes in the fenland

Micropalaeontological, stratigraphic, radiocarbon, and published data have been assessed to elucidate sea-level changes in the Fenland during the Plandrian Stage. Up to 8 periods characterised by positive tendencies in sea-level movement have been identified, Wash I - VIII, separated by up to 7 periods, Fenland I - VII, dominated by negative tendencies in sea-level movement. 102 (>14) C dates form the chronological framework on which this scheme is based. Negative tendencies cannot yet be confirmed as absolute falls in sea-level due to the errors involved in the assessment of sea-level indicators. These errors relating to age and altitude have been quantified wherever possible. The variation in stratigraphic surfaces has been briefly assessed and the statistical limitations of pollen analyses have been shown by the application of confidence limits to the pollen diagrams. A computer program, NEWPLOT, has been developed to draw the pollen diagrams, including pollen concentration, from 6 sites at Bourne Fen, Cowbit Wash and Adventurers’ Land. Models have been suggested to assess the stratigraphic and micropalaeontological changes at the salt marsh-freshwater fen transition and to identify tendencies of sea-level movement. Problems relating to the existing methodology of sea-level studies have been noted from the difficulty in objectively correlating the data and results of various authors. The errors identified in the collection, interpretation and correlation of sea-level data have repercussions for the planning of sea-defences and land-use in low-lying coastal areas

The Comparison of Sea Level Chronologies from the Estuaries of the North Sea (Progress Report)

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Reconstructing paleoseismic deformation, 2: 1000 years of great earthquakes at Chucalén, south central Chile

In this paper we adopt a quantitative biostratigraphic approach to establish a 1000-year-long coastal record of megathrust earthquake and tsunami occurrence in south central Chile. Our investigations focus on a site in the centre of the rupture segment of the largest instrumentally recorded earthquake, the AD 1960 magnitude 9.5 Chile earthquake. At Chucalén coseismic subsidence in 1960 is recorded in the lithostratigraphy and biostratigraphy of coastal marshes, with peat overlain by minerogenic sediment and changes in the assemblages of diatoms (unicellular algae) indicating an abrupt increase in relative sea level. In addition to the 1960 earthquake, the stratigraphy at Chucalén records three earlier earthquakes, the historically documented earthquake of 1575 and two prehistoric earthquakes, radiocarbon dated to AD 1270–1450 and 1070–1220. Laterally extensive sand sheets containing marine or brackish diatom assemblages suggest tsunami deposition associated with at least two of the three pre-1960 earthquakes. The record presented here suggests a longer earthquake recurrence interval, averaging 270 years, than the historical recurrence interval, which averages 128 years. The lack of geologic evidence at Chucalén of two historically documented earthquakes, in 1737 and 1837, supports the previously suggested hypothesis of variability in historical earthquake characteristics. Our estimates of coseismic land-level change for the four earthquakes range from meter-scale subsidence to no subsidence or slight uplift, suggesting earthquakes completing each ∼270 year cycle may not share a common, characteristic slip distribution. The presence of buried soils at elevations below their modern equivalents implies net relative sea-level rise over the course of the Chucalén paleoseismic record, in contrast to relative sea-level fall over preceding millennia inferred from sites on the mainland. Sea-level rise may contribute to the preservation of evidence for multiple earthquakes during the last millennium, while net relative sea-level fall over the last 2000–5000 years may explain the lack of evidence for older earthquakes

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

The roddons of the English Fenlands are fossilised silt and sand-filled tidal creek systems of mid- to late-Holocene age, incised into contemporaneous clay deposits. However, anthropogenic change (drainage and agriculture) has caused the former channels to become positive topographical features. Three stratigraphically discrete generations of roddon have been discriminated. They all show well-developed dendritic meander patterns, but there is little or no evidence of sand/silt infill during meandering; thus, unlike modern tidal creeks and rivers they typically lack laterally stacked point bar deposits, suggesting rapid infill. Major “trunk” roddons are rich in fine sands and there is little change in grain size from roddon mouth to the upper reaches, suggesting highly effective sand transport mechanisms and uniform conditions of deposition. Tributaries are silt-rich, while minor tributaries also have a significant clay component. During infill, active drainage networks appear to have been choked by sediment, converting mudflat/salt-marsh environments into widespread peat-forming freshwater reed swamps

Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site

Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site's former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services

Sea-level constraints on the amplitude and source distribution of Meltwater Pulse 1A.

During the last deglaciation, sea levels rose as ice sheets retreated. This climate transition was punctuated by periods of more intense melting; the largest and most rapid of these—Meltwater Pulse 1A—occurred about 14,500 years ago, with rates of sea-level rise reaching approximately 4 m per century1, 2, 3. Such rates of rise suggest ice-sheet instability, but the meltwater sources are poorly constrained, thus limiting our understanding of the causes and impacts of the event4, 5, 6, 7. In particular, geophysical modelling studies constrained by tropical sea-level records1, 8, 9 suggest an Antarctic contribution of more than seven metres, whereas most reconstructions10 from Antarctica indicate no substantial change in ice-sheet volume around the time of Meltwater Pulse 1A. Here we use a glacial isostatic adjustment model to reinterpret tropical sea-level reconstructions from Barbados2, the Sunda Shelf3 and Tahiti1. According to our results, global mean sea-level rise during Meltwater Pulse 1A was between 8.6 and 14.6 m (95% probability). As for the melt partitioning, we find an allowable contribution from Antarctica of either 4.1 to 10.0 m or 0 to 6.9 m (95% probability), using two recent estimates11, 12 of the contribution from the North American ice sheets. We conclude that with current geologic constraints, the method applied here is unable to support or refute the possibility of a significant Antarctic contribution to Meltwater Pulse 1A

InterPro in 2017-beyond protein family and domain annotations

InterPro (http://www.ebi.ac.uk/interpro/) is a freely available database used to classify protein sequences into families and to predict the presence of important domains and sites. InterProScan is the underlying software that allows both protein and nucleic acid sequences to be searched against InterPro's predictive models, which are provided by its member databases. Here, we report recent developments with InterPro and its associated software, including the addition of two new databases (SFLD and CDD), and the functionality to include residue-level annotation and prediction of intrinsic disorder. These developments enrich the annotations provided by InterPro, increase the overall number of residues annotated and allow more specific functional inferences