bluuebunny/crossref_metadata_2025 huggingface dataset:
When Did the Western Anatolian Grabens Begin to Develop?
Authors: Yilmaz Yücel , Genç Ş. Can , Gürer Fevzi , Bozcu Mustafa , Yilmaz Kamil , Karacik Zekiye , Altunkaynak Şafak , Elmas Ali
Published: April 2008

To solve a long-lasting controversy on the timing and mechanism of generation of the western Anatolian graben system, new data have been collected from a mapping project in western Anatolia, which reveal that initially north-south trending graben basins were formed under an east-west extensional regime during Early Miocene times. The extensional openings associated with approximately north-south trending oblique slip faults provided access for calc-alkaline, hybrid magmas to reach the surface. A north-south extensional regime began during Late Miocene time. During this period a major breakaway fault was formed. Part of the lower plate was uplifted and cropped out later in the Bozdağ, Horst, and above the upper plate approximately north-south trending cross-grabens were developed. Along these fault systems, alkaline basalt lavas were extruded. The north-south extension was interrupted at the end of Late Miocene or Early Pliocene times, as evidenced by a regional horizontal erosional surface which developed across Neogene rocks, including Upper Miocene-Lower Pliocene strata. This erosion nearly obliterated the previously formed topographic irregularities, including the Bozdağ elevation. Later, the erosional surface was disrupted and the structures which controlled development of the Lower-Upper Miocene rocks were cut by approximately east-west trending normal faults formed by rejuvenated north-south extension. This has led to development of the present-day east-west trending grabens during Plio-Quaternary time.
Timing of Extension on the Büyük Menderes Graben, Western Turkey, and Its Tectonic Implications
Authors: Bozkurt Erdin
Published: April 2008

The Büyük Menderes Graben is one of the most prominent structures of western Anatolia (Turkey) and borders the Aegean. New structural and stratigraphic evidence demonstrates that the (?)Miocene fluvio-lacustrine, coal-bearing red clastic sediments exposed along the northern margin of the graben are northward back-tilted, locally folded and overlain unconformably by horizontal terraced Pliocene-Pleistocene sediments. Also, there is no evidence that these red clastics at the base of the Neogene sequence were deposited during neotectonic extension. It is suggested here that these sediments cannot be regarded as passive neotectonic graben-fill deposits.

This new evidence further indicates that the age of the modern Büyük Menderes Graben is Pliocene, younger than previously considered (Early-Middle Miocene) and that initiation of north-south neotectonic extensional tectonics in the graben, and thus in western Anatolia, is unlikely to have resulted from orogenic collapse. The Pliocene estimate of the start of extension is in close agreement with the start of slip on the North Anatolian Fault Zone. The north-south extensional tectonics, and associated east-west faulting and basin formation, commenced during the Pliocene due to the effect of westward tectonic escape of the Anatolian block along the North and East Anatolian Faults. New mammal evidence also constrains the start of slip on the younger faults which bound the present-day graben floor to
c
. 1 Ma.

The Büyük Menderes Graben has experienced a two-stage extension. An initial extension (latest Oligocene-Early Miocene) along initially moderately, steeply dipping normal faults was superseded by movement on steeper normal faults during the (?)Pliocene. The two phases of deformation appear to reflect significant changes in the tectonic setting of western Anatolia and are attributed to orogenic collapse followed by tectonic escape.
Petrogenesis of Basalts from Southern Turkey: the Plio-Quaternary Volcanism to the North of İskenderun Gulf
Authors: Yurtmen Sema , Rowbotham George , İşler Fikret , Floyd Peter A.
Published: April 2008

The Quaternary volcanicity north of the İskenderun Gulf in the eastern Mediterranean is represented by small basaltic scoria cones and flows. Approximately 115 km
2
of land area is occupied by young basalts which straddle both the main (the Karataş-Osmaniye Fault Zone) strike-slip fault system which forms the Africa-Turkey Plate boundary and the suture of the southern arm of the former Neotethys Ocean. Detailed petrological and geochemical analyses of these rocks have been carried out, with the aim of trying to understand why they have erupted in this locality. The rocks consist mainly of basanites (43–46ilica; 3.9–6.5% alkalis) and some alkali olivine basalts (45ilica; 3.8–4.2% alkalis). Both the basanites and alkali olivine basalts are porphyritic, vitrophyric and highly vesiculated with euhedral and subhedral olivine (Fo
82
-Fo
78
) phenocrysts set in a fine-grained groundmass of olivine (Fo
70
), plagioclase (An
71
-An
66
), clinopyroxene and titanomagnetite. Olivine phenocrysts contain abundant Cr-spinel and titanomagnetite inclusions. Some geochemical characteristics of these basalts indicate similarity with extension-related alkali basalts; others indicate similarity with ocean island basalt; and yet others indicate subduction-related characteristics. This complexity leads to difficulties with interpretation, especially since there is no demonstrable local extension, subduction or mantle plume activity in the vicinity.
Relationship between current measurements and sonographs of subtidal bedforms in the macrotidal Tay Estuary, Scotland
Authors: Duck Robert W. , Wewetzer Silke F. K.
Published: April 2008

Near bottom current measurements have been compared with sonographs revealing a variety of subtidal dune geometries at eight stations in the middle reaches of the macrotidal Tay Estuary, Scotland. At six stations, dune asymmetries did not support the tidal dominance expressed in terms of maximum or average current speeds. Determination of bottom tidal current dominance according to the length of time during which a speed of 0.5 ms
−1
was exceeded, as a proxy for the inequality of the total ebb and flood tide bedload sediment transports, provides a better, but not perfect, correlation with sonographs. Other controls on dune asymmetry and reversal are height, sediment discharge rate and bottom current velocity fluctuations. The study has shown that bedload transport processes and pathways in this relatively small (
c.
8 km
2
), dynamic part of the estuary are far more complex than previously inferred and near bed flows do not simply correspond with the surface water circulation pattern. Neither sonographs nor current data alone are adequate to gain an understanding of subtidal bedforms in such an environment.
Marine sand supply and Holocene coastal sedimentation in northern France between the Somme estuary and Belgium
Authors: Anthony Edward J.
Published: April 2008

From the Somme estuary to Belgium, much of the French coast is characterized by aeolian dunes, sand-choked estuaries and nearshore sand banks. The lack of sand-bearing rivers in this area and the abundance of sand in the English Channel point to the latter as the source of this important sandy accumulation. A comparison of patterns of nearshore and coastal accumulation with results from studies of the hydrodynamics and marine sand transport pathways suggests long-term drift of sand towards the French coast and the North Sea in response to tidal flows and meteorological forcing. This has occurred through sand bank migration onshore, and sand transport alongshore in a pathway hugging the French coast. From this tide-driven ‘conveyor belt’, fine sand moved onshore to form aeolian dunes, while sand of all sizes has accumulated as thick estuarine fill. This mode of Holocene coastal development emphasizes the joint action of tidal currents, storm waves and wind activity, within an overall framework of tidal dominance in this macrotidal setting.
Storm surges and erosion of coastal dunes between 1957 and 1988 near Dunkerque (France), southwestern North Sea
Authors: Vasseur Bruno , Hequette Arnaud
Published: April 2008

The comparison of aerial photographs of eroding coastal dunes located between Dunkerque (Northern France) and the Belgium border revealed that the retreat rate of the dune front increased between 1957 and 1988. Analyses of hourly water levels from the Dunkerque Harbour tide gauge showed an increase in the frequency of high water levels associated with storm surges during the same period. Significant wave heights that could be generated during these high water level events were computed according to a wave hindcast model and using wind data collected at Dunkerque. These analyses show an increase in storm magnitude and frequency during the last two decades of the study period, and suggest a strong relationship between dune front erosion and frequency of storm surge conditions. Since relative sea-level is rising in the southern North Sea, coastal dunes will probably be more frequently reached by storm waves in the future. Consequently, more severe coastal dune erosion may take place during the next decades, increasing the risk of flooding of coastal lowlands.
Erosion and recycling of aeolian dunes in a rapidly infilling macrotidal estuary: the Authie, Picardy, northern France
Authors: Anthony Edward J. , Dobroniak Christine
Published: April 2008

The Authie is a rapidly infilling macrotidal (mean estuary-mouth spring tidal range = 8.5m) estuary in Picardy, northern France, whose mouth is affected by strong tidal currents and wind waves generated in the English Channel. The estuary cuts across a major sand dune barrier and has been sourced by sand derived from offshore and alongshore, as well as from recycling of the aeolian dunes lining its north bank. Sand released by the severe erosion of these north bank dunes is temporarily stored on the beaches. A small fraction of the sand is back-cycled into the dunes via blowouts. The rest is transported towards the inner estuary where it forms longitudinal aeolian dune ridges and sand sheets that are ultimately recycled into sandy-muddy intertidal flats that develop into salt marshes. The erosion of the dunes lining the north bank of the estuary represents a morphodynamic adjustment to concentration of the tidal flux against this north bank by massive accretion and progradation of a south-bank sand platform. This erosion contributes in giving a funnel-shaped estuary mouth and probably in accommodating the tidal prism following large-scale reclamation of the inner estuary. The estuary-ward recycling of aeolian dune sand enhances overall accretion of the estuary whose ultimate fate is complete silting up in the decades to come.
Textural and geochemical evidence for the provenance of aeolian sand deposits on the Aquitaine coast, SW France
Authors: Saye Samantha E. , Pye Kenneth
Published: April 2008

The coastal dune system of the Aquitaine region, SW France, is the largest in Europe. At the present time the dunes are mostly stabilized by forest vegetation which is largely the product of dune stabilization schemes undertaken since the late 18th century. Much of the shoreline is currently eroding at rates of 1–2ma
−1
, which are likely to increase if predictions of accelerated sea-level rise and increased storminess are correct. The sources of the beach and dune are poorly understood, and need to be identified in order to assess the sand budgets and likely dynamic response of the dune systems to changes in environmental forcing factors. This paper presents the results of an investigation to characterize the beach and aeolian sand in the region, and to identify its origin. The dune sands were found to be texturally and compositionally similar to the Quaternary Sable de Landes which occurs landward of, and partially beneath, the coastal dune belt. The results suggest that marine, aeolian and local fluvial reworking of the Sable de Landes has provided the main source of coastal dune sand, although marine erosion of Pleistocene deposits exposed in the coastal cliffs of the Medoc has made a secondary contribution.
The use of Nuclear Magnetic Resonance Imaging (MRI) to assess impact of oil-related waste on estuarine sediments and sediment dynamics
Authors: Reeves Alison D. , Chudek John A.
Published: April 2008

The Marine Pollution Control Unit of the Department of Transport are at present testing the suitability of burial and landfarming of oily residues in sandy coastal environments as an alternative to landfill sites. The tendency for oil related compounds to sorb to sediments (and hence to affect their cohesiveness) has been extensively investigated, but this has not involved or permitted the ‘observation’ or measurement of advection/diffusion processes or the breakdown of these residues within sediments.

MRI, which is a multidimensional technique allowing the position of nuclei (most commonly protons) to be located within a known volume of substrate, for example sediment, provides a means of monitoring the change in position and the eventual breakdown of oil within sediments, thus offering a method of assessing the harming potential of oils in near-shore environments. Two dimensional (2D) and three dimensional (3D) MRI analysis of the movement of oil in estuarine sediments show that, using appropriate parameters, movement of the oil can be both observed and quantified. To aid quantification a sample holder fabricated from polyvinylsiloxane, an inert material visible in magnetic resonance images has been used as an internal intensity standard. The results show the great potential of MRI in studying protonated contaminants in these materials, notwithstanding the presence of paramagnetic species in estuarine sediments, which might distort the image. Sediments studied thus far have been collected from the Tay Estuary, NE Scotland.
Stratigraphic architecture, relative sea-level, and models of estuary development in southern England: new data from Southampton Water
Authors: Long A. J. , Scaife R. G. , Edwards R. J.
Published: April 2008

This paper presents the results of an investigation into the Holocene depositional history of Southampton Water, southern England. A three phase history of estuary development is proposed. Between
c.
7500 and 5000
bp
(8200 to 5700 cal. a
bp
), mean sea-level rose rapidly from
c.
−9m to −4 m
od
. During this interval thin basal peats which developed in present outer estuary locations were inundated and the area of intertidal and subtidal environments within the estuary expanded. Relative sea-level (RSL) rise began to slow between 5000 and 3000
bp
(5700 and 3200 cal. a
bp
) and a phase of saltmarsh and freshwater peat accumulation occurred. In this interval freshwater peat-forming communities extended outwards and seawards across former saltmarsh and mudflat environments and caused a reduction in the extent of the intertidal area within the estuary. During the late Holocene there was a switch to renewed minerogenic sedimentation as most of the freshwater coastal wetlands of Southampton Water were inundated. This tripartite model is broadly applicable to the Thames and the Severn estuaries, suggesting that regional processes have controlled their macroscale evolution. RSL change and variations in sediment supply emerge as key controls during the first two phases of estuary development. The late Holocene demise of the estuary wetlands probably reflects a propensity for increased sediment reworking and unfavourable conditions for the accumulation and preservation of organogenic deposits due to reduced rates of long-term RSL and watertable rise.
Coastal development and human activities in NW Germany
Authors: Petzelberger Bianka E. M.
Published: April 2008

The flat coastal region of NW Germany is constructed of siliciclastic and organic sediments which were deposited during the Holocene sea level rise. By 7500
bp
the marine transgression had reached the present coastal area which is proved by brackish-marine sediments. Nearly coinciding with this there was an evident deceleration of the sea-level rise. A reconstruction of the coast-line for the last 2000 years on the basis of the sediment and settlement distribution shows that the coast remained more or less in the same position during this period of time. However this does not apply to certain regions. Thus, bays which existed around the time 0
ad
, gradually became mainland. In other areas late Medieval and early Modern storm floods were responsible for great losses of mainland, such as the Jade Bay. These losses of mainland are especially noteworthy, because these area had been protected with dykes. Until the beginning of dyke building the settlers of the flat coastal region raised their dwelling areas artificially and built dwelling mounds (so-called Wurten) in order to be protected against flooding. By doing this men reacted to the influences of their environment, but by building dykes they started to shape their environment actively.
Intertidal peats and the archaeology of coastal change in the Severn Estuary, Bristol Channel and Pembrokeshire
Authors: Bell Martin
Published: April 2008

Dates for the beginning and end of intertidal and coastal peat formation are reviewed in the Severn Estuary, Bristol Channel and Pembrokeshire. Peat formation at many sites started between
c.
6000–4000 Cal
bc
and in the Severn Estuary continued until
c.
200 Cal
bc
. Archaeological evidence is concentrated at two main stages within the coastal sequences. Throughout the area Mesolithic sites underlie the earliest peat and relate to coastal exploitation just prior to the transgression represented by peat formation. During the main period of peat formation from the later Mesolithic to the early Bronze Age there is only small-scale human activity within the coastal peats. A second episode of concentrated human activity is confined to the Severn Estuary and occurs in the middle Bronze Age and Iron Age. Round and rectangular buildings and trackways are associated with the initial stages of marine transgressions which led to the burial of a coastal bog by minerogenic silts. A transgression in the middle Bronze Age
c.
1400 Cal
bc
was followed by a regression phase, the main period of human activity at Goldcliff, this ended with a widespread transgression centred on in the third century
bc
. The factors which attracted human activity at particular stages within the coastal sequence are considered, as is the relative visibility of human activity during each sedimentary stage. The contribution which archaeological evidence, particularly dendrochronological dating of wooden structures, can make to the dating of coastal change is emphasized.
Basal ice formation and deformation in central Greenland: a review of existing and new ice core data
Authors: Souchez R. , Vandenschrick G. , Lorrain R. , Tison J.-L.
Published: April 2008

In this paper we review, and supplement, existing data to investigate the character, origin and deformation of the basal silty ice of the centre of the Greenland ice sheet as revealed in the Dye3, GRIP and GISP2 cores.

A major process of basal silty ice formation in the central part of Greenland is incorporation of relict non-glacial ice at the base of the ice sheet during its development. The evidence for this can be found in a stable isotope composition study, both in δD and δ
18
O, in a total gas content and gas composition study, in a comparison of the dielectric conductivity profile and chemical profiles. Ice crystallographic investigations and the study of the isotopic compositions in Nd, Sr and Pb of the mineral particles embedded in the silty ice help to clarify the situation.

The processes proposed to explain the stacked sequence developed in the basal silty ice of these central areas are folding resulting in the interbedding of silty ice and glacial ice, and flow-induced mixing related to circular motion of ice in bedrock depressions with flow separation accompanied by some entrainment of the underlying ice.
Ice crystallographic evolution at a temperate glacier: Glacier de Tsanfleuron, Switzerland
Authors: Tison Jean-Louis , Hubbard Bryn
Published: April 2008

Ice crystallographic measurements have been made on eight cores retrieved from temperate Glacier de Tsanfleuron, Switzerland. Cores are aligned approximately along a flow-parallel transect, allowing a stratigraphic model of crystallographic evolution at the glacier to be constructed.

Results indicate the presence of four crystallographic units at the glacier. Unit 1 composed of homogeneous, fine-grained ice with a uniform fabric, is located within
c.
20 m of the ice surface in the accumulation area of the glacier. Crystal growth within this unit occurs in the absence of significant stresses, and its rate is closely described by an Arrheniustype relationship. Unit 2 ice, characterized by the local development of coarser crystals, forms after some decades of Arrhenius growth, marking the initial influence of processes of dynamic recrystallisation. Unit 3 ice, characterized by an abrupt increase in minimum crystal size, occurs at a depth of
c.
33 m throughout the glacier. In the accumulation area, this increase coincides with the first evidence of systematic fabric enhancement, interpreted in terms of dynamic recrystallisation. Unit 4 ice, characterized by large, interlocking grains with a multi-modal girdle fabric, develops within
c.
10 m of the glacier bed. Here, the measured minimum crystal size is consistent with a steady-state balance between Arrhenius processes of grain growth and strain-related processes of grain-size reduction. These changes are interpreted in terms of the effects of intense, continuous deformation in this basal zone.
The effect of H
2
SO
4
on the stress exponent in ice single crystals
Authors: Baker I. , Trickett Y. L. , Pradhan P. M. S.
Published: April 2008

Sulphuric acid is a naturally occurring contaminant in ice. Recently, it was demonstrated that, during compression tests at −20°C and a strain rate of 1 × 10
−5
s
−1
, as little as 0.1 ppm H
2
SO
4
reduced both the peak strength and the subsequent flow stress of ice single crystals that deform primarily by basal slip. In the present work, compression tests were performed at −20°C at a variety of strain rates on both undoped ice single crystals and ice single-crystals containing 6.8 ppm sulphuric acid of various orientations again deforming primarily by basal slip. The results show that sulphuric acid dramatically decreases both the peak stress and the subsequent flow stress of ice single crystals at all strain rates. In contrast, the stress exponent was determined to be 1.89–1.97 and was unaffected by the dopant. This value is similar to values found by previous workers for undoped ice crystals.
Structural styles and deformation fields in glaciers: a review
Authors: Hambrey Michael J. , Lawson Wendy
Published: April 2008

Early structural glaciological research focused on analysis of particular structures or on mapping of structural features at particular glaciers. More recently, glacier structures have been interpreted in the context of deformation rates and histories measured or estimated using a range of techniques. These measurements indicate that glacier ice experiences complex, polyphase deformation histories that can include a wide range of types, rates and orientations of strain. Deformation styles in glacier ice resemble those in rocks, but occur at a much faster rate, allowing direct measurements to be undertaken, and providing potentially useful models of rock deformation. Structural analysis in the context of measured deformation shows that a wide range of structures (e.g. folds, foliations, boudins, shear zones, crevasses and faults) develop in response to complex strain environments, but strain does not necessarily result in the generation of structures. In the future, three-dimensional numerical modelling may be able to interpret and predict deformation histories and structural development.
Experimental work on the effect of pre-existing anisotropy on fabric development in glaciers
Authors: Wilson Christopher J. L.
Published: April 2008

Localization of deformation in ice is known to be important at all scales in deforming glaciers. However, relatively little is known of the significance of shear localization and the influence of fabric development in anisotropic ice at microscopic scales (<mm-cm). In this experimental study, the effect of initial
c
-axis preferred orientation and the inclination of the primary layering in anisotropic ice masses, during both plane strain-compression and combined simple shear-compression, have been examined. A series of creep tests in the temperature range of −5 to −1°C over a range of shortening strains varying from 10 to 40% and compressive stresses ranging from 0 to 0.7 MPa have been undertaken. Significant variations in the strain rate and microstructural development have been observed in the plane strain-compression experiments that reflects the varying orientations of the anisotropy and its relationship to easy-glide directions in the ice mass. In the unconfined combined compression and shear experiments minimum shear stress rates vary between the variously oriented anisotropic ice masses and deviate from the normal power flow law for isotropic ice. Where annealing occurs, such ice masses preserve the pre-existing
c
-axis fabric and hence may reflect a contribution from both the recrystallized and inherited ice components.
Use of a viscous model of till rheology to describe gravitational loading instabilities in glacial sediments
Authors: Hindmarsh Richard C. A. , Rijsdijk Kenneth F.
Published: April 2008

This paper models the operation of loading (Rayleigh-Taylor) instabilities in sediments using an effective-pressure-dependent viscosity such has been used to model the deformation of sediment beneath glaciers. A particular feature is a strong increase of viscosity with depth, resulting from the fact that the effective pressure increases with depth.

Observations suggest that more than one wavelength is generally present (e.g. diapirism and loadcasting) which requires at least three layers with uniform properties to be present. Three layers permit wavelength growth maxima at two distinct wavelengths. We investigate whether an effective-pressure dependent rheology is consistent with RT instabilities, and whether the non-uniformity it produces is able to increase the number of growth-rate maxima.

The investigation starts from the point where sediment in an underlying layer is less dense than the overlying sediment, and the Rayleigh-Taylor instability starts to operate. The mechanics of two layers of finite thickness but infinite extent are modelled by the Stokes equations. The equation set is linearized, and the Fourier transform taken in order to describe the periodic horizontal variation of flow fields at a specified wavelength.

The influences of layer thickness and viscosity ratio on the flow fields are considered. It is found that, for a given wavelength, layer thickness has a far stronger influence on flow fields than does viscosity ratio. For all configurations inspected, the dependence of growth rate on wavenumber exhibited one maximum, meaning that a variable viscosity model does not produce multiple wavelengths. Maximum growth rates occur at wavelengths corresponding to the layer thicknesses.

We infer that loading instabilities occurring at wavelengths around the layer thicknesses are consistent with the effective-pressure-dependent viscous model.
Kinematic indicators of subglacial shearing
Authors: Van der Wateren Frederik M. , Kluiving Sjoerd J. , Bartek Louis R.
Published: April 2008

Criteria to distinguish between sediments that have been subglacially deformed and those that are undeformed, or deformed by other mechanisms, are sparse. In this paper we develop structural criteria to reconstruct the deformation history of glacial sediments that can be readily applied in the field as well as to analyses of thin sections of tills and related materials.

Progressive simple shear is the simplest model to describe the deformation history of subglacially deformed sediments. It includes most of their characteristic structural aspects and provides tools for the kinematic analysis of subglacially deformed sediments. Progressive simple shear generates asymmetric structures, in which the principal direction of finite extension is subparallel to the direction of shearing. This is the simple shear fabric’s most distinctive characteristic, and that which most reliably defines the palaeo-ice flow direction. At a moderately strong intensity of deformation a typical shear zone in unlithified sediments may contain folded and strongly attenuated sediment layers, producing a transposed foliation which must not be mistaken for a sedimentary layering. Original sedimentary and deformation structures may completely disintegrate in the most intensely deformed sediments leading to its homogenization, although the typical shear zone fabric may still be identified in thin section.
Micromorphological evidence for polyphase deformation of glaciolacustrine sediments from Strathspey, Scotland
Authors: Phillips E. R. , Auton C. A.
Published: April 2008

A combination of field investigation and micromorphological analysis has been applied to polydeformed Late Devensian rhythmites and glacigenic diamicton, exposed in Strathspey, Scotland. This provided information on the geometry, kinematics and relative ages of ductile and brittle structures, and records a complex subglacial deformation history. The deformation is interpreted as resulting from a single progressive event, associated with over-riding of proglacial lake sediments by wet-based ice. The earliest deformation (‘D
1
’) resulted from compaction/loading (pure shear) and imposed a bedding-parallel (S
1
) fabric throughout the rhythmites. S
1
was subsequently deformed by kink bands and minor ductile shearing during ‘D
2
’. A later ‘D
3
’ event, characterized by soft-sediment deformation and fluidization of matrix-poor sands, was accompanied by an increase in pore water pressure. This lead to hydrofracturing of the rhythmites. The most intense deformation (‘D
4
’), which resulted from simple shear, was partitioned into the upper part of the sequence. It produced folding, thrusting and brittle microfaulting in response to NNW-directed ice-push. These findings indicate that, in general, subglacial deformation is not homogeneous and can extend to depths of >3 m below the presumed ice-sediment interface.
Large-scale glaciotectonic thrust structures in the eastern Danish North Sea
Authors: Huuse Mads , Lykke-Andersen Holger
Published: April 2008

The distribution of shallow, detached thrust fault complexes in the eastern Danish North Sea has been mapped based on 6400 km of high-resolution multichannel seismic data. Individual thrust segments are 200–1000 m long and 100–250 m thick with up to 200 m of horizontal displacement. Thrusting mainly affected upper Middle Miocene to lower Pleistocene strata and predated an extensive system of now buried subglacial valleys. The thrust structures are located along a 200 km long NW-SE trend. The general thrust direction is towards the SW, parallel to inferred directions of ice movement during the Elsterian and Saalian glaciations. This direction is, however, also parallel to the dip of the underlying detachment surface. The detachment surface corresponds to the mid-Miocene unconformity in the SE and the base of the Quaternary to the northwest. Detachment is generally located at depths of 130–270 m below sea level.

The structures are interpreted as glaciotectonic thrust structures of Elsterian and/or Saalian age. The driving mechanism is interpreted to be gravity spreading in front of glaciers advancing from the north, NE and east. Thrusting was facilitated by the presence of SW-dipping detachment surfaces.
Cladistic perspectives on early bivalve evolution
Authors: Carter J. G. , Campbell D. C. , Campbell M. R.
Published: April 2008

Parsimony analysis suggests derivation of the Bivalvia from monoplacophorans rather than from rostroconchs, and additionally indicates that a phylogenetic classification of the Bivalvia can be achieved by erecting the superorder Nuculaniformiinov.and the order Nuculanoidanov.for the superfamily Nuculanoidea; relegating all other palaeotaxodonts to the superorder Nuculiformii; restricting the order Nuculoida to the families Nuculidae and Pristiglomidae; expanding the order Solemyoida to include ctenodontid genera as basal plesions; restricting the superorder Heteroconchia to palaeoheterodonts and heterodonts, exclusive of the Modiomorphidae; relegating the new family Evyanidae, the Colpomyidae, Matheriidae and Modiolodontidae to near-basal plesion status within the superorder Pteriomorphia; restricting the Mytiloida to the superfamily Mytiloidea, inclusive of modiolopsid genera as basal plesions; placingOrtonellaas a basal plesion within the Cyrtodontoida; expanding the order Pectinoida to include the Myodakryotidae and the suborders Limina and Pectinina; and expanding the superfamily Arcoidea to include the frejid genera andCatamarcaiaas basal plesions, and the family Glyptarcidae. Modiomorphid anomalodesmatans appear to be more closely related to the Pteriomorphia than to the Heteroconchia, andEvyanalies close to the common ancestry of modiomorphids and colpomyid pteriomorphians. Arcoids may have evolved from left-right symmetrical but otherwise rhombopteriid-like ancestors, rather than from actinodontoids or directly from cyrtodontids. The new family Eodonidae is proposed to distinguish the nacreous genusEodonfrom the non-nacreous Astartidae within the superfamily Crassatelloidea.
Relationships between the extant Anomalodesmata: a cladistic test
Authors: Harper Elizabeth M. , Hide Elizabeth A. , Morton Brian
Published: April 2008

Although ancient anomalodesmatans were apparently abundant shallow and deep burrowers, in Recent seas the subclass comprises some of the most specialized rarest of all bivalves. The morphological adaptations associated with diverse life habits has persistently frustrated attempts to achieve a widely accepted scheme for the relationships between extant families.

A cladistic analysis, using 43 informative anatomical and shell characters for each of the extant anomalodesmatan families has produced a single, reasonably robust tree which is in broad, albeit imperfect, agreement with the known fossil record of the subclass. This total evidence tree places the Pandoridae, Lyonsiidae, Cleidothaeridae and Myochamidae, and also the Thraciidae, Periplomatidae and Laternulidae in monophyletic groups. Carnivory appears diphyletic, with the Parilimyidae separated from the ‘septibranch’ families (Cuspidariidae, Verticordiidae, Lyonsiellidae and Poromyidae) which form a monophyletic group. The enigmatic tube-dwelling Clavagellidae appear as a sister group to the ‘septibranchs.’.

Re-analysis of the data matrix using only those 18 characters which could be socred from shell characters alone, produced a tree which contradicted the total evidence tree rather than producing a poorly resolved version. The degree of convergence shown by shell characters make it, at least at present, difficult to include the extinct anomalodesmatan families in a cladistic analysis.
Comparative sperm ultrastructure in pteriomorphian bivalves with special reference to phylogenetic and taxonomic implications
Authors: Healy John M. , Keys Jennifer L. , Daddow Lina Y. M.
Published: April 2008

Pteriomorphian spermatozoa, like those of most other bivalves, are of the classic aquasperm type (conical acrosomal vesicle, short to rod-shaped nucleus, short midpiece composed of two centrioles and a ring of spherical mitochondria, a simple flagellum). Whereas most other bivalve subclasses show at least some defining acrosomal feature(s), this does not appear to be the case within the Pteriomorphia. While this could indicate non-monophyletic status, it also correlates with the fact that the Pteriomorphia are a very old and very successful group of bivalves. Acrosomal similarities suggest a close link between the Ostreoidea and Limoidea (acrosomal vesicle with wedge-shaped apical zone; radiating plates present but not well developed); and between the Pterioidea, Pinnoidea and Pectinoidea (dense anterior layer; very well developed radiating plates). For supposedly closely related taxa, the Arcoidea and Limopsoidea (both Arcoida) differ markedly from each other in acrosomal shape and substructure. The affinities of the Anomioidea and even more so the Mytiloida remain uncertain, the latter possibly connected with the Pterioidea or, more likely, removed from the rest of the Pteriomorphia (mytiloid acrosomes show concentric lamellae). A very close relationship between the Pectinidae and Spondylidae of the Pectinoidea is demonstrated (dense anterior layer of acrosome recurved). Within the Mytilidae (Mytiloidea) there is substantial variation in sperm morphology between supraspecific taxa especially at the subfamial level.
Growth patterns of noetiid ligaments: implications of developmental models for the origin of an evolutionary novelty among arcoid bivalves
Authors: Thomas R. D. K. , Madzvamuse A. , Maini P. K. , Wathen A. J.
Published: April 2008

The dorsal ligaments of arcoid bivalves typically consist of oblique, lamellar and fibrous sheets, alternating along the hinge so that their attachments from characteristic chevron patterns. New elements are added at or near the middle of the pattern, as the ligament grows ventrally and gets longer. Most Palaeozoic arcoids exhibit this growth pattern, which still predominates among their living descendants. Early in the Cretaceous, a novel pattern emerged, with vertical strips of lamellar ligament embedded in grooves in the sheet of fibrous ligament which is attached to each valve. In contrast with the chevron, duplivincular ligament, new elements are added to each end of the noetiid ligament, anteriorly and posteriorly. This distinctive growth pattern is the defining character of the family Noetiidae.

Remarkable variation among individuals within populations of a living limopsid arcoid includes forms with vertical strips of lamellar ligament. These variants suggest how the noetiid growth pattern could have been derived from the duplivincular pattern. Computer simulations show that such patterns can be generated by a reaction-diffusion mechanism of the sort first conceived by Turing (1952,
Philosophical Transactions of the Royal Society, London, Series B
,
237
, 37–72). Moreover, the noetiid growth pattern can simply be derived from the duplivincular pattern by a developmental switch based, for example, on a change in boundary conditions. These results indicate that striking differences in form may arise from modest changes in the developmental process. The evolution of the Noetiidae, members of which are quite disparate in overall shell form, should be reassessed. The derived character on which this family is based may not be uniquely shared, so the group could well be polyphyletic.
The Queen Scallop
Aequipecten opercularis
: a new source of information on late Cenozoic marine environments in Europe
Authors: Johnson A. L. A. , Hickson J. A. , Swan J. , Brown M. R. , Heaton T. H. E. , Chenery S. , Balson P. S.
Published: April 2008

Few data exist on seasonal variation in the temperature (or other aspects of the environment) of late Cenozoic shelf seas in Europe. Ontogenetic records in the shell of
Aequipecten opercularis
, a widespread, fast-growing and typically well-preserved bivalve, are a potential source. Study of modern forms has shown that oxygen stable isotopes are incorporated in equilibrium with surrounding seawater (hence providing a faithful record of temperature) and data from late Holocene
A. opercularis
of the southern North Sea Basin (SNSB) indicate that extreme winter (as well as summer) temperatures are registered. Oxygen isotope data from apparently well-preserved, mid-Pliocene shells of the SNSB indicate seasonal temperatures similar to present, whereas microgrowth increment data suggest substantially warmer conditions, in accordance with other evidence. The balance of evidence thus implies cryptic diagenetic corruption of the isotopic temperature signature in mid-Pliocene shells. However, it would be premature to discount the possibility of cooler mid-Pliocene conditions than currently recognized. Ontogenetic variation in carbon isotopic composition within shells is minor and apparently unrelated to environment, but differences between mid-Pliocene, late Holocene and modern shells probably relate to changes in atmospheric CO
2
concentration. Unlike certain taxa, seasonal variation is not evident in the strontium or magnesium contents of the
A. opercularis
shell, but may be displayed by other trace elements, hence affording (together with seasonal increment width variation) a means of independent temporal calibration of isotope profiles. Ontogenetic records of environment from
A. opercularis
can be complete (and, in the case of increment data, easily recovered) but are of short duration. They must be complemented by (less complete) records from longer lived taxa to obtain the fullest possible environmental history. Seasonal cycles in ontogenetic records afford a means of establishing age and growth rate, and can therefore provide information of value for evolutionary studies and management of living populations.
The myth of metabolic cold adaptation: oxygen consumption in stenothermal Antarctic bivalves
Authors: Peck Lloyd S. , Conway Lucy Z.
Published: April 2008

Antarctic marine ectotherms are often described as only being capable of living in a restricted temperature range, i.e. they are stenothermal. However, few data exist demonstrating that for a given group this is the case. The Antarctic bivalve molluscs
Laternula elliptica
and
Limopsis marionensis
are similar to other Antarctic invertebrates and can only exist within a temperature window of 6–12°C. This is two to six times smaller than the range for temperate and tropical bivalves, thus demonstrating their stenothermal nature. The possibility of elevated metabolic rates of cold-water ectotherms has been a topic of debate over many years. Recently, the suggestion that metabolic rates must be elevated at low temperatures to overcome constraints has been supported by findings that mitochondrial contents of muscles in ectotherms are higher at low temperatures. Data, presented here for standard or routine metabolic rates of 41 species of bivalve mollusc from polar, temperate and tropical sites, indicate that oxygen consumption is not elevated at low temperatures. Indeed, analysis of Q
10
coefficients between 0 and 25°C suggests that metabolic rates of polar species may be lower than would be expected by comparison with temperate bivalves.
Marine mussels, their evolutionary success, ecological significance and use as chronometers of environmental change
Authors: Seed R. , Richardson C. A. , Smith K.
Published: April 2008

The evolution of the heteromyarian form and neotenous retention of the byssus into the adult stage were central to the colonization of hard substrata and the subsequent evolutionary success of epibyssate mytilids. In addition, these mussels are supreme filter feeders and exhibit many structural, behavioural and life-history traits which make them particularly successful colonizing species. As competitively dominant species, mussels can potentially monopolize epibenthic communities with a consequent reduction in diversity of the primary space-occupying species. However, mussel patches themselves are extremely diverse, offering numerous resources which are exploited by a range of associated organisms from most animal phyla. Mussel beds can influence large-scale coastal and estuarine processes such as productivity and eutrophication, and can significantly alter sediment biogeochemistry. Annual growth lines and tidal bands in mussel shells have been used to estimate age, and to investigate the effects of environmental factors such as seawater and air temperature, spring-neap lunar tidal cycles and exposure to chlorination regimes in power station culverts. Analysis of the elemental composition of the incremental record in long-lived mytilids has been used to assess the effects of anthropogenic inputs into coastal waters.
A temperate reef builder: an evaluation of the growth, morphology and composition of
Sabellaria alveolata
(L.) colonies on carbonate platforms in South Wales
Authors: Naylor Larissa A. , Viles Heather A.
Published: April 2008

Sabellaria alveolata
(Linné) (Polychaeta: sabellariidae) is a sedentary polychaete that builds wave-resistant reefs from sand-sized particles. Reefs are formed in areas with a large, continuous supply of sand-sized sediment and turbulent water, such as the Bristol Channel, UK. Although several studies have documented the extent, growth, form and geological importance of Sabellariidae, their bioconstructive role has not been adequately assessed.
S. alveolata
occurs rarely in the UK and is classified as a distinct ecological unit by the Marine Nature Conservation Review, yet it has been little studied. Thus, there is a need for greater understanding of the species’ role in UK coastal ecology and geomorphology. An evaluation of reef development in terms of composition, growth and extent of
S. alveolata
constructions on carbonate shore platforms in South Wales is presented here. Results indicate that
S. alveolata
is a fast-growing species capable of juvenile settlement, tube formation and growth of 2.5–5.0 cm in as little as two months after installation of exposure blocks of artificial substrata. Particle size analysis of 24 randomly selected reefs and ten adjacent sand samples shows a significant difference in mean grain size, with worms consolidating particles of a coarser size distribution than the mean particle size of surrounding sand. Preliminary scanning electron microscope observations indicate preferential use of flat, platy and elongate particles in the worm tubes. This research forms part of a larger study concerned with quantifying the bioconstructive capability of
S. alveolata
.
Skeletal growth rates of Upper Cretaceous rudist bivalves: implications for carbonate production and organism-environment feedbacks
Authors: Steuber Thomas
Published: April 2008

The skeletal growth rates of late Cretaceous rudist bivalves have been inferred from cyclic variations of isotopic and chemical compositions which are found in sclerochronological profiles of outer shell layers. Annual shell accretion of 11 studied shells from different environmental settings was in the range of less than 10 to 54 mm. CaCO
3
production of individual rudists was calculated to range from 12 to 214 g a
−1
, and estimates of annual production of rudist communities assuming dense growth fabrics range from 4.6 to 28.5 kg m
−2
. These production rates are not significantly higher when compared to modern mussel or oyster beds but, in contrast to modern analogues, rudist associations were much more important for the sedimentary budget of low-latitude shallow-water depositional environments.

Controlling factors for the formation of growth fabrics and carbonate production are evaluated in a case study of rudist formations from a single depositional sequence. From turbulent outer platform environments to lagoonal inner platform settings, a decrease both in carbonate production and size of shells was found among specimens of a single species. No differences in carbonate production are evident when carbonate production in siliciclastic and calcareous environments is compared. Potential feedbacks between rudists and their environment induced by vertical growth, large production of bioclastic sediment and ejected biodeposits are discussed.