bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vertical accretion versus elevational adjustment in UK saltmarshes: an evaluation of alternative methodologies
Authors: Cahoon Donald R. , French Jonathan R. , Spencer Thomas , Reed Denise , Möller Iris 
Published: April 2008

Abstract

Simultaneous measurements of vertical accretion from marker horizons and marsh-elevation change from sedimentation-erosion tables (SET) were made in selected marshes along the East Anglian coast of the UK in order to address the following objectives:

(1)
to ascertain the validity of treating accretion measurements obtained within tidally dominated, minerogenic saltmarshes as equivalent to surface elevation changes;

(2)
to explore the implications, in terms of physical and biological processes, of discrepancies between separately measured vertical accretion and elevation change within contrasting marsh types.

Data were collected from several marsh environments at Scolt Head Island and Stiffkey on the North Norfolk coast and at an experimental managed realignment project near Tollesbury, Essex. Scolt Head Island was selected for its long-term datasets of marsh accretion, Stiffkey for its contrasting open coast-back barrier settings, and Tollesbury for its experimental management, in order to illustrate the potential application of the SET method and evaluate the relationship between vertical accretion and elevation change in a variety of marsh settings.
The relationship between vertical accretion and elevation change varied widely among marsh settings of different age and height (within the tidal frame) at Scolt Head Island and Stiffkey. Rates of vertical accretion and elevation change were similar in the older and midheight settings on Scolt Head Island, indicating control of elevation change by surface accretionary processes (e.g. sediment deposition). However, subsurface processes controlled elevation at three of the marsh sites. Spartina Marsh, the youngest and lowest of the back barrier settings at Scolt Head Island, exhibited continuous shallow subsidence (vertical accretion greater than elevation change) over a 4-year period, implying that compaction controls elevation change. In the upper part of Hut Marsh and the interior of the Stiffkey marshes, elevation change exceeded vertical accretion suggesting that subsurface processes (e.g. organic accumulation) controlled elevation in these settings. Surface accretionary processes control elevation change in both the highly dynamic, outer marsh at Stiffkey and the low, restored marsh at Tollesbury. Despite the occurrence of shallow subsidence, all sites gained elevation at an annual rate comparable to that of sea-level rise. In summary, the SET provides the means to critically evaluate the influence of vertical accretion measures on elevation and represents an improved method by which to evaluate the vulnerability of a marsh to sea-level rise.
Holocene coastal lowlands in NW Europe: autocompaction and the uncertain ground
Authors: Allen J. R. L. 
Published: April 2008

Abstract
The continuous, progressive, irreversible and asympototic processes of sediment autocompaction play a significant but so far largely neglected role in determining the coevolving character of Holocene landscapes and sedimentary sequences formed in coastal marshlands. Autocompaction ensures that actual total sediment deposition rates are always greater than the rate at which sea-level rise creates accommodation space. High rates of autocompaction help to foster resource-rich, mineralogenic tidal marshes that can be readily exploited by humans from neighbouring higher ground, for example, dryland areas, or locations within the marshland where peat formation had persisted sufficiently late that domal, raised bogs had not yet completely collapsed. Subsequent autocompaction may bring about a significant inversion of relief. The general effects of autocompaction are a high degree of vertical stratigraphic distortion and displacement amounting to as much as a few metres, depending on the depth to ‘basement’, the lithologies present, and their order of deposition. Autocompaction results in inaccurate sea-level curves when based on intercalated peats, inaccurate rates of sea-level change when calculated on a bed-averaged basis, and inconsistent age-altitude relationships among archaeological sites preserved in coastal deposits. The challenge is to predict/retrodict autocompaction in Holocene coastal lowlands, in order to better understand sequence development, the evolution of surface environments, topography and landscape, and the constraints placed upon (and opportunities presented to) human communities living in these contexts.
The Humber estuary: managing the archaeological resource in a dynamic environment
Authors: van de Noort Robert , Ellis Stephen 
Published: April 2008

Abstract
The archaeology of the intertidal wetlands of the Humber estuary is of international importance, and includes prehistoric boats, trackways, fishtraps and platforms, Roman settlements and ports and Post-Medieval fishweirs. This resource is threatened by coastal erosion and flood defence improvement work. This paper outlines a strategic approach to the threatened archaeological resource in the Humber estuary.
Radar evidence of water-saturated sediments beneath the East Antarctic Ice Sheet
Authors: Siegert Martin J. 
Published: April 2008

Abstract

Ice-penetrating airborne radar data from East Antarctica were examined in order to identify regions of the ice-sheet base where water-saturated sediments are thought to occur. Distinctive radar returns are identified from three subglacial environments as follows. (1) A frozen ice-bedrock interface, which shows scattering of a weak radar signal. (2) An ice-water contact above a subglacial lake where the radar reflections are bright, and horizontally flat. (3) The surfaces of two regions of water-saturated basal sediment, one at the centre of the ice sheet and one near the ice margin, where the radar returns are almost as bright as those from the subglacial lake, but not as flat. Characterization of radar signals from these regions is valuable since the results can be compared with data from other areas of the ice-sheet base to establish the nature of the sub-ice contact at a continental scale. The subglacial geomorphology of sediments near the ice margin displays large-scale (
c.
10 km long,
c.
200 m high) features with slopes that are relatively steep up-glacier, and shallow down-glacier, plus small-scale (<1 km long, <50 m high) regularly spaced undulations. Such sub-ice physiography indicates that the radar data may display
in-situ
sedimentary structures.
An instability mechanism for drumlin formation
Authors: Fowler A. C. 
Published: April 2008

Abstract
Drumlins are subglacial bedforms that are formed by the interaction of ice flow with an erodible basal topography. The mechanism of their formation bears resemblance to similar processes that cause the formation of dunes and anti-dunes in rivers, and sand dunes in deserts. In 1998 Hindmarsh showed that the interaction of a shearing ice flow with a deformable basal till layer could cause an instability which promotes the growth of basal topography, though he was unable to give analytic criteria for the instability. Here we analyse Hindmarsh’s model, and by using certain approximations, we are able to give concise analytical parametric criteria for this instability. The resultant instability occurs if the basal shear stress is larger than a critical value which increases with increasing basal effective pressure, and which also depends on the basal till thickness. It is hypothesized that this instability is the basic mechanism involved in the formation of Rogen moraine and drumlins.
Evolutionary significance of fossil larval shell characters: a case study from the Ostreoidea (Bivalvia: Pteriomorphia)
Authors: Malchus Nikolaus 
Published: April 2008

Abstract

Prodissoconchs of Middle Jurassic oysters possess key characters for a new understanding of the hinge evolution within the Ostreoidea. The ancestral larval hinge most likely evolved from a mytilid-like provinculum through accelerated growth in an antero-ventral direction along a flat, helico-spiral trajectory. The posterior denticles moved into the centre of the hinge axis while the central and anterior denticles were reduced in size and eventually disappeared. The remaining, now central, posterior denticles evolved further into a secondary symmetrical hinge. In most oysters, except for example
Tiostrea
, the larval ligament maintained its relative position between posterior and anterior denticles, even though this is not obvious in the Ostreidae because of the loss of the anterior denticles. Larval and adult ligaments are continuous. The examined specimens provide further evidence for the plesiomorphic state of planktotrophy within the superfamily. Although additional direct evidence is lacking, consideration of all new available data favour the hypothesis that the postero-dorsal notch is uniquely derived by oysters. The ideas on character evolution put forward in this study are consistent with phylogeny hypotheses based on palaeontological-biological data and recent genetical studies.
Phenotypic plasticity of burrowing depth in the bivalve
Macoma balthica
: experimental evidence and general implications
Authors: Edelaar Pim 
Published: April 2008

Abstract

Depth of burrowing in bivalves presents the individual with a trade-off: burrowing more deeply increases safety against predators but shallow burrowing increases food intake. Large variation in burrowing depth exists both between and within species. This study investigated whether part of this variation in depth in the tellinid
Macoma balthica
can be attributed to phenotypic plasticity. A predatory crab and food availability were either offered or withheld in separate aquaria and the response in burrowing depth measured. Individuals burrowed more deeply in the presence of a crab but only to shallow depths in the presence of food. This suggests that individuals can assess their environment and subsequently make decisions on their burrowing depth.

Phenotypic plasticity like this flexible anti-predation behaviour in
M. balthica
can have farranging effects. In the presence of predators burrowing depth increases, reducing energy uptake and subsequent growth and reproduction, whereas increased burrowing depths reduces mortality by predation, further affecting prey and predator population dynamics.
Microfacies development in Late Archaean stromatolites and oolites of the Ghaap Group of South Africa
Authors: Wright David T. , Altermann Wladyslaw 
Published: April 2008

Abstract
Organism-environment feedbacks in Precambrian platformal carbonates and reefs were strongly influenced by the activities of diverse microbial ecosystems. Microfacies studies of representative platformal microbial carbonates, comprising cyanobacterial mat, stromatolites and giant ooids, from the Late Archaean Ghaap Group of South Africa have provided compelling evidence for an intimate relationship between taphonomic evolution, fabric development and mineralogy in rocks of the Gamohaan and Boomplaas formations. Cements, both in fold hinges and between the limbs of slump-folded and contorted, partially-degraded, pyritiferous stromatolitic laminae, were precipitated after deformation of organic fabrics, but before or during their compaction, indicating that cementation took place at the same time as anoxic organic degradation involving bacterial sulphate reduction. Bundles and strands of the organic remains of filamentous cyanobacteria, in varying states of degradation in both stromatolites and ooids, have been preserved by mineralization. Structural detail is usually best preserved in calcite, where cyanobacterial sheaths, 10 µm to 25 µm in diameter and hundreds of micrometres in length, can be clearly seen. Petrographic analysis of the microfabrics using cathodoluminescence reveals dolomicrite nucleated along the outer margin of some sheaths. Dolomicrospar and dolospar fabrics developed progressively in association with increasing sheath degradation, as evidenced by the sequential loss of structural detail, culminating in a xenotopic fabric comprising brown, inclusion-rich, anhedral crystals with irregular boundaries. Biogeochemical modelling supports a genetic link between bacterial sulphate reduction and (1) calcite precipitation in the contorted laminae, and (2) replacive dolomitization of the calcitic matrix in the stromatolites and ooids. The evidence indicates that anoxic organic diagenesis was an essential and major process in controlling carbonate precipitation and mineralogy in widespread microbialitic sediments of the Ghaap Group, a depositional environment analogous to many other Archaean, Proterozoic and, during periods of biotic stress, some Phanerozoic carbonate platforms.
Reefs and coral carpets in the northern Red Sea as models for organism-environment feedback in coral communities and its reflection in growth fabrics
Authors: Riegl Bernhard , Piller Werner E. 
Published: April 2008

Abstract

Coral framework construction and resultant growth fabrics in response to environmental factors were studied in the northern Red Sea, and the Gulfs of Suez and Aqaba. The dependence of growth fabric types on sea-floor topography, oceanography and the ecology of constituent coral species was investigated. Five types of coral frameworks and their growth fabrics were differentiated:
Acropora
reef framework (platestone to mixstone facies);
Porites
reef framework (domestone facies);
Porites
carpet (columnar pillarstone facies); faviid carpet (mixstone facies);
Stylophora
carpet (thin pillarstone facies). Two non-framework community types were found:
Stylophora-Acropora
community and soft coral communities. Reef frameworks and resultant growth fabrics show a clear ecological zonation along depth and hydrodynamic exposure gradients. Coral carpets build a framework lacking a distinct internal zonation since they only grow in areas without pronounced gradients. In the northern Red Sea they show a gradual change with depth from
Porites
(pillarstone) to faviid (mixstone) dominance.

The initiation of frameworks was governed by bottom topography (reefs on steep slopes and highs, coral carpets in flat areas). According to environmental conditions, different coral communities produce different framework and growth fabric types. In step with framework growth the environment is modified. The modified environment in turn modifies the coral communities. Thus an environment-organism-environment feedback loop exists.
Rudist lithosome development on the Maiella Carbonate Platform margin
Authors: Stössel Iwan , Bernoulli Daniel 
Published: April 2008

Abstract
Cenomanian to mid-Campanian rudist lithosomes, exposed along a transect across the Maiella carbonate platform margin (central Apennines, Italy), are described in terms of faunal and matrix composition, geometry, and facies association. On the external platform, the lithosomes reveal a complex geometry and a comparatively high faunal diversity, whereas lithosomes of the inner platform are generally thinner and show a simple, sheet-like geometry. Based on the abundance of lithosomes and of the associated rudist-derived calcarenites, we propose that lithosome formation and, hence, sediment production preferentially occurred on the outermost platform, although the preservation potential of bioconstructions was low in these high-energy environments. Reworking of rudists led to sediment export both towards more internal areas as well as towards the adjacent basin. In contrast, on the inner platform, rudist lithosome formation was restricted by the lack of an adequate substrate and by higher sedimentation rates.
A mid-Frasnian marine incursion into the southern part of the Munster Basin: evidence from the Foilcoagh Bay Beds, Sherkin Formation, SW County Cork, Ireland
Authors: Higgs K. T. , MacCarthy I. A. J. , O’Brien M. M. 
Published: April 2008

Abstract
The Munster Basin of southern Ireland contains a thick (7 km +) succession of Old Red Sandstone sediments interpreted as the product of various alluvial processes. The present study presents a preliminary sedimentological and palynological analysis of a grey succession informally known as the Foilcoagh Bay Beds, which is the lowest unit of the Sherkin Formation exposed in the southern part of the basin. Sedimentological analysis of the succession suggests that it is the product of sinuous distributary channels, flanked by permanently flooded overbank areas that endured occasional crevasse splay floods. These conditions evolved into a protected lagoon or lake that received periodic high energy floodings from an adjacent marine environment. Palynological study has refined the age of the Foilcoagh Bay Beds as mid-Frasnian time. Palynofacies analysis has provided direct evidence of marine influence as revealed by the presence of marine microfossils and abundant amorphous organic matter at some dark grey mudrock levels. This suggests deposition in a well-established lacustrine or lagoonal environment in which anoxic conditions prevailed at intervals and which was subjected to a period of marine incursion. The recognition of a marine influence in the Munster Basin at an early stage in its history has several important implications, including the following (1) previous models for the basin that suggested an enclosed centripetally draining entirely non-marine system have to be re-evaluated; (2) the drainage pattern and direction of the marine incursion were probably controlled by localized subsidence along an east-east direction; initiation of subsidence associated with the development of the east-west-trending South Munster Basin may have commenced much earlier than previously considered; (3) the occurrence of marine conditions has been tentatively correlated with the Rhinestreet mid-Frasnian sea-level highstand; (4) the recognition of marine conditions early in the known history of the basin provides a pathway for fish to have entered the basin; (5) the basin may have had a marine connection throughout much of Late Devonian time, opening the possibility for base-level control of the alluvial systems within the basin by external eustatic factors.
New data on the age of the uppermost ORS and the lowermost post-ORS strata in Dickson Land (Spitsbergen) and implications for the age of the Svalbardian deformation
Authors: Piepjohn Karsten , Brinkmann Lars , Grewing Anke , Kerp Hans 
Published: April 2008

Abstract
In NW Spitsbergen, the infill of a large Old Red Sandstone (ORS) basin was affected by the Svalbardian deformation shortly after the sedimentation of the uppermost ORS units. In the Billefjorden area, along the eastern margin of the basin, folded and thrustfaulted Devonian deposits are unconformably overlain by undeformed Carboniferous clastic sediments and platform carbonate deposits. To re-examine the age of the Svalbardian deformation, samples for palynological investigations were taken from the youngest deformed ORS strata and the oldest post-Svalbardian sediments. The results of palynological investigations show that the folded and thrust-faulted uppermost ORS unit, the Plantekløfta member of the Mimerdalen Formation (Andrée Land Group), is Late Famennian in age. The lowermost undeformed and unconformably overlying post-ORS unit, the Triungen member of the Hørbyebreen Formation (Billefjorden Group), is ?Late Tournaisian to Viséan but not Famennian in age. Thus, the compressional west-directed folding and thrusting of the Svalbardian deformation took place after Late Famennian and before Late Tournaisian time.
Climatic modelling in the Cretaceous using the distribution of planktonic Foraminiferida
Authors: Hart Malcolm B. 
Published: April 2008

Abstract
During the Cretaceous, planktonic Foraminiferida underwent a major diversification, colonizing a wider range of water depths and geographical regions. Orville Bandy, over 30 years ago, was the first to recognize the potential of using this regional distribution to reconstruct different palaeoceanographic regimes. Using new data from the South Atlantic Ocean, Antarctic Ocean and the Indian Ocean it is possible to show the poleward migration of warm-water taxa during the Cretaceous and compare it with data already available from the Northern Hemisphere. Instead of the present-day nine latitudinal zones based on planktonic taxa it is only possible to identify five with any degree of reliability. These are from north to south, the Boreal, Transition, Tropical (= Tethyan), Transition and Austral. In some of the developing oceans during the Cretaceous (e.g. the Eastern Indian Ocean, South Atlantic Ocean) there are local biogeoprovinces with quite distinctive local assemblages and morphotypes. While these do not reflect on the climatic zonation they provide an interesting insight into the development of the plankton. The foraminiferal distributions are compared with climatic maps produced by the assessment of other data sources.
Environmental changes in pre-evaporitic Late Miocene time in the Lorca Basin (SE Spain): diatom results
Authors: Jurkschat Th. , Fenner J. , Fischer R. , Michalzik D. 
Published: April 2008

Abstract

During the Late Miocene the Lorca Basin, which was an integrated part of the Betic Strait, underwent desiccation. The present investigation was completed to determine the response of the diatom flora to environmental changes before this event. Near the city of Lorca (Province of Murcia, SE Spain) the outcrop area around the Serrata ridge was studied and a stratigraphic section of 125m has been measured and sampled (115 samples). The Serrata ridge is capped by a 25m thick gypsum bed (Gypsum Member of the Serrata Formation). The profile below these gypsum layers comprises marl, sandstone, gypsum and partially laminated diatomite (Varied Member of the Serrata Formation). The frequency of radiolaria, siliceous sponge spicules, silicoflagellates, ebridians, diatoms and diatom species has been determined quantitatively. For the lower 87.5m of the section, which contains sufficiently well preserved diatoms, an age of latest Miocene (6.6-5.3 Ma; Magnetic Epoch 6 and 5) can be assigned by the presence of the diatom species
Asterolampra acutiloba
and
Nitzschia reinholdii
, applying the stratigraphic ranges of the species used in the North and Equatorial Pacific and in the Atlantic. In total, 116 diatom species and species-groups have been identified. However, the number of species per sample varies only between 13 and 36 species (a minimum of 300 valves counted). This low diversity, together with a dominance of one species-group,
Thalassionema nitzschioides
(up to 80%), which tolerates considerable ecological changes (e.g. in salinity) indicate that environmental stress must have prevailed during the sedimentation of the Varied Member of the Serrata Formation. Abundance fluctuations of this species-group, as well as changes in the composition of the remaining diatom assemblage and decreases in abundances of the siliceous microfossil groups, reflect repeated periods of interruption of the still marine influenced deposits before the deposition of thick gypsum layers. Several repetitive changes are indicated, where each cycle is characterized by an increase in meroplanktonic species (e.g.
Paralia sulcata, Actinoptychus senarius
) and by a contemporary decrease in the holoplanktonic species towards the top, suggesting progressive environmental stress and a shallowing of the basin. Five of these cycles are clearly distinguished characterizing the initial stages of the evaporitic desiccation event in the Lorca Basin. Benthic diatoms are present only in low abundances (2–4%) and show no correlation with these fluctuations.