bluuebunny/crossref_metadata_2025 huggingface dataset:
White-mica 'crystallinity', finite strain and cleavage development across a large Variscan structure, NW Spain
Authors: GUTIÉRREZ-ALONSO GABRIEL , NIETO FERNANDO
Published: December 2007

X-ray diffraction analyses were performed on white-micas, formed under strain and low-grade metamorphic conditions, from sandstones and siltstones along a transect through the Narcea Antiform, a large structure that separates the external from the internal zones of the Variscan belt of NW Spain. The results indicate a close spatial relationship between the onset of metamorphism and the cleavage front. At the cleavage front, strain is characterized by oblate ellipsoids that have
x
=
y:z
ratios from 1 to 1.5. The
x
=
y:z
ratio increases westward (up to 3.0), as does the grade of metamorphism, and is accompanied by an increase in the 'crystallinity' index of the white-mica from very low to low metamorphic grade. This increase corresponds qualitatively to an increase in penetrativeness of the axial planar cleavage. In the western part of the Narcea Antiform, the major deformation event was the development of kilometre-scale, reverse shear zones. Because of polyphase deformation, these rocks are not suitable for quantitative strain analysis, but qualitatively, finite strain can be observed to be prolate and invariably larger in this region than in the eastern sector. The metamorphic grade is higher in the western part of the Narcea Antiform, with local maxima occurring next to the base of the shear zones. The
b
0
cell parameter, a semi-quantitative geobarometer measured in the white-mica, is chaotic in the Eastern sector, showing a clear detrital inheritance. In the western sector it is rational due to complete re-equilibration during thermal resetting. The inverse correlation between finite strain and white-mica 'crystallinity' is close, showing that the anchizone-epizone limit can be related to the increase of finite strain above values of R
s
= 1.5. The close relation between white-mica 'crystallinity' and strain is suitable for tracking strain variations in extensive fine-grained siliciclastic rocks where no appropiate strain markers are found.
A model for the structure and development of fault zones
Authors: CHILDS C. , WATTERSON J. , WALSH J. J.
Published: December 2007

Cross-sections of fault zones commonly show two sub-parallel slip surfaces which bound more or less deformed rock. This characteristic geometry can be explained by a combination of 'tip-line' and 'asperity' bifurcation processes. Fault tip-line bifurcation is due to irregular tip-line propagation resulting in leading edge segmentation, fault overlap and eventual duplex formation. Asperity bifurcation removes a fault surface irregularity by the generation of a new slip surface which by-passes the original slip surface. Repetitions of either or both bifurcation processes give rise to a fault zone with a complex and unpredictable internal geometry. These processes are described mainly on the basis of observation of normal faults hut can be applied to other fault types. Fault zone thickening by bifurcation is intermittent rather than progressive and localised fault zone thinning may occur.
High-temperature (>90°C) calcite precipitation at Waikite Hot Springs, North Island, New Zealand
Authors: JONES BRIAN , RENAUT ROBIN W. , ROSEN MICHAEL R.
Published: December 2007

The Waikite Hot Springs emit waters (most >90°C) with a pH of 7.2–8.9, high SiO
2
(150–170mgl
−1
) concentrations, but low Ca (<l0mgl
−1
) and Mg (<1mgl
−1
) concentrations. Although amorphous silica (sinter) is the dominant precipitate, calcite is forming around some springs. At Springs WS-2 and WS-11, ledges and 'lily-pads' in the shallow waters around the pool edges and outflow channels, have rims formed of trigonal calcite prisms and interiors formed of interlaminated calcite and amorphous silica.

At Spring WS-5, water ejected at 92–98°C has cooled to 72°C, 2 m downslope from the orifice. The soft calcite that covers the discharge apron is composed of disorganized micrite or composite fibrous calcite crystals. Although extracellular mucus is common, no microbes were found. Near the orifice, ooids up to 4 mm in diameter, were found in the soft micrite that forms the floor of a shallow pool where the water temperature is 92°C. Mucus, generated by thermophilic bacteria, mediated the formation of some cortical laminae.

Calcite is being precipitated at these springs because the constant supply of Ca
2+
and CO
2–
3
compensates for the low Ca content of the water. Its crystal form is controlled by the supply rate of Ca
+
and CO
2–
3
and mucus generated by the thermophilic bacteria.
A synthesis of the stratigraphic and tectonic setting of the Uralian ophiolites
Authors: SAVELIEVA G. N. , NESBITT R. W.
Published: December 2007

The Ural Mountains mark a 2500 km long, linear mid-Palaeozoic orogenic zone representing the closure of an ocean basin-island arc system between the European Plate to the west and the Siberian Plate to the east. Within the orogenic belt there are over 150 ophiolitic masses displaying sections of oceanic lithosphere with both harzburgitic and lherzolitic restites. These occur as tectonic slices and allochthons within volcano-sedimentary sequences and melanges. The paper concentrates on the main lines of evidence which form the basis for the palaeo-reconstruction of the collision zone. In particular, it reviews the stratigraphic, sedimentological and structural evidence which is used to support a model in which the ophiolites were emplaced from the east onto the continental margin of the European Plate. In general the evidence is that as older oceanic crust was obducted, new arc and oceanic crust was being created to the east. As well as providing a general geological map which locates the major ophiolites, the paper presents cross sections across the major zones of the belt, showing current views on palaeo-reconstructions. A tectonic model is presented which attempts to integrate the volcanic-sedimentary history of the belt with the emplacement history of the ophiolites.
Cretaceous sedimentary rocks on the Masirah Ophiolite (Sultanate of Oman): evidence for an unusual bathymetric history
Authors: IMMENHAUSER A.
Published: December 2007

Autochthonous sedimentary rocks on the Masirah Ophiolite preserve a record of vertical movements of their oceanic basement. The Masirah Ophiolite was formed in the uppermost Jurassic and subsequently underwent thermal subsidence for about 20 Ma as documented by pelagic sediments. Submarine alkali-basaltic volcanism in the lower Barremian marks the onset of rapid basement uplift to or above sea-level. Carbonate platforms grew in Barremian/mid-Aptian time on highs of oceanic basement. The uplift is interpreted as the result of transpressive tectonism along a large oceanic fracture zone. The platforms submerged in the mid-Aptian and reached the CCD in the Albian. Ribbon cherts were deposited during the Albian to Santonian time. The first influx of siliciclastic detritus, shed from the Arabian craton, is recorded in Coniacian sandstones. Ophiolitic conglomerates interfinger in the Campanian to mid-Maastrichtian with continent-derived sandstones, reflecting regional compressive tectonism. Crystalline exotics, deposited in the late Maastrichtian, are derived most likely from the Precambrian basement of Arabia, whilst the origin of the sedimentary exotics, dated Triassic to Cretaceous, remains unclear. The Masirah Ophiolite was overthrust at the Cretaceous–Tertiary boundary by an upper ophiolite nappe and emplaced onto the margin of southeast Oman.
Switches in subduction direction and the lateral termination of mountain belts: Pyrenees-Cantabrian transition, Spain
Authors: TURNER JONATHAN P.
Published: December 2007

The switch in subduction polarity at the transition from the Pyrenees to the Cantabrians implies an abrupt change in the gross direction of plate movement. The Pyrenees formed in response to the northward subduction of continental crust beneath Europe during the Palaeogene whereas the Cantabrians developed during the southward subduction of Biscay oceanic crust beneath Spain. As yet, no attempt has been made to explain the mechanism and geometry of this apparent switch in plate kinematics. The transition from northward to southward subduction occurs across a discrete lineament, the Pamplona Fault, oriented transversely with respect to the long axis of the adjacent mountain belts. Regional mapping reveals a 180° switch in the facing direction of thrusts and associated folds across the Pamplona Fault. Balanced structural cross-sections, constructed either side of the Pamplona Fault, exhibit marked contrasts in bulk shortening, depth to detachment, gross structural geometry, and the thickness and completeness of the pre-orogenic Mesozoic succession. The Pyrenean-Cantabrian transition zone is thus envisioned as a fundamental crustal lineament of pre-orogenic origin.

A new model for the Cenozoic tectonic evolution of north Spain has the Pamplona Fault separating a series of transtensional basins in the Pyrenees from a passive margin in the Cantabrians. Subsequent plate collision between Spain and Europe reactivated the faults that controlled pre-orogenic 'syn-rift' sedimentation in the present Pyrenean area. In the Cantabrians, however, plate collision signalled a shift from a passive margin to an active margin consuming Biscay oceanic crust beneath a northern Spain subduction zone. An implication of this model is that the foreland crust was affected variably by 'backarc' heating during the early stages of Spain-Europe collision. This is expressed by the changing depth of the Ebro Basin, the foreland basin that developed in response to Pyrenean-Cantabrian orogenesis, whose thickness of the Tertiary succession varies laterally according to changes in flexural rigidity.
A tectonomagmatic model for the genesis and emplacement of Caledonian calc-alkaline lamprophyres
Authors: VAUGHAN ALAN P. M.
Published: December 2007

Petrogenetically related, Caledonian, calc-alkaline lamprophyric and shoshonitic dykes in eastern Ireland appear coeval with sinistral transtension. These dykes are exposed in a 10 km wide zone trending SW from Clogher Head, that strikes anticlockwise of the surface trace of the Iapetus Suture. Lamprophyre dykes intruded sinistral Riedel shears with a mean strike-trend at 040°. Riedel shears that host lamprophyre dykes strike anticlockwise of primary sinistral shears by 35°, consistent with sinistral transtension: primary shears strike 070°. parallel to the mean strike trend of shoshonitic dykes. Sinistral. primary shears may have controlled the emplacement of Caledonian, shoshonitic, intrusive rocks. Using lamprophyres from Clogher Head as examples, a new model is proposed for lamprophyre genesis and emplacement related to simple shear. In this model. transient decompression of metasomatized mantle during simple shear triggers release of volatile-rich potassic magma, which ascends to crustal levels along steep strike-slip faults. An association between lamprophyre magmatism and deep faulting suggests that relatively deep (>60km) seismicity may precede magma ascent. This model can account for several paradoxes of Caledonian magmatism.
The Gölbaºi basin, southeastern Turkey: a complex discontinuity in a major strike-slip fault zone
Authors: WESTAWAY R. O. B. , ARGER J. A. N.
Published: December 2007

We show that the 33 km long Gölbaºi basin on the East Anatolian fault zone marks the triple junction between the African, Arabian. and Turkish plates. The main strand of the Turkish–Arabian plate boundary, the Göksu fault, enters this basin from the ENE before splaying to form faults which develop farther southwest into the Turkish–African and African-Arabian boundaries. The Gölbaþi Türkođu fault, the Turkish–African boundary, is shown to have slipped 16 km; the prevously unrecognised Kirkpmar fault. the African–Arabian boundary, has slipped 17 km. We propose that this fault geometry developed at c. 3 Ma following earlier slip, starting at
c.
5 Ma, on other strike-slip faults nearby which marked the start of westward motion of the Turkish plate.
Accretion tectonics of the Neotethyan Ermioni Complex, Peloponessos, Greece
Authors: CLIFT PETER D.
Published: December 2007

Late Cretaceous-Early Tertiary terrigenous and calcareous turbidites exposed in the Argolis Peninsula of southern Greece represent an accretionary complex assembled during the closure of a Late Cretaceous Neotethyan ocean. Massive sulphide bodies, thrust slices of cherts and serpentinized ultramafics are found imbricated within a tectonic stack of approximately 8 km thickness. Basalts with overlying Cenomanian-Maastrichtian pelagic limestones and metalliferous sediments are found distributed throughout the complex. The basalts give trace-element chemical signatures consistent with an origin at a mid-ocean ridge or back-arc basin. Folding and shearing is locally intense in fault zones 10-20 m across, resulting in a block-in-matrix fabric. Metamorphism within the complex is of low-to-high diagenetic grade, with grade generally increasing structurally up-section. Palaeo-slope indicators suggest that the ocean basin lay to the present SE. The SSW to NNE emplacement is at variance with the SW-vergent Early Tertiary thrusting of the Hellenides. and may be explicable in terms of transpressional tectonics along the southeastern termination of the Pelagonian micro-continent. The processes which assembled the Ermioni Complex appear to have operated in a similar fashion to those seen along the margins of major ocean basins, although active over much shorter periods of time.
Chemostratigraphic correlation, structure and sedimentary environments in the Dalradian' of the NW Co. Mayo inlier, NW Ireland
Authors: WINCHESTER J. A. , MAX M. D.
Published: December 2007

A thorough geochemical survey of the Dalradian rocks in the NW Mayo inlier has shown that each formation has a characteristic geochemical signature, within regional geochemical trends that vary systematically with stratigraphic age. This geochemical characterization enables correlation between geographically and tectonically isolated stratigraphic successions in the NW Mayo inlier. An almost complete succession of late Proterozoic Grampian. Appin and Argyll Group Dalradian rocks structurally overlies earlier basement Annagh Division gneisses in structural blocks bounded by Caledonian thrusts, extensional low-angle faults, and steeply dipping faults. Grampian–Appin Group relationships are better seen here than anywhere else in Scotland or Ireland. but no Tayvallich Subgroup or Southern Highland Group Dalradian rocks are present.

Comparison with chemostratigraphic data from Scottish Dalradian rocks reveals broadly similar chemical trends with time. suggesting that the geological evolution of the Dalradian took place in a related depositional environment, probably an unbroken continental margin, along the entire Dalradian outcrop seen in both Scotland and Ireland.
A second major fluvial sourceland for the Silesian Pennine Basin of northern England
Authors: GLOVER B. W. , LENG M. J. , CHISHOLM J. I.
Published: December 2007

New Nd and Sr data indicate that two isotopically distinct terrains supplied sediment to the Silesian Pennine Basin. The sources consisted of a northerly-derived fluvial system, which was responsible for much of the detritus during Namurian times, and a second major system which entered at the west and south sides of the basin. This second source, which provided material derived from the former Avalonian/Armorican and Gondwanan terranes, became more influential through the Silesian, so that by Westphalian B/C times, the central parts of the basin were being fed by systems derived from the west and south of the basin. Although the inferred source rocks are petrographically diverse their Nd–Sr signatures are remarkably similar, perhaps due to multicyclic sediment homogenization. The change in provenance may reflect early Variscan tectonic activity to the west of the Pennine Basin.
Linkage between mantle and crustal structures and its bearing on inherited structures in northwestern Scotland
Authors: SNYDER D. B. , ENGLAND R. W. , McBRIDE J. H.
Published: December 2007

Deep seismic reflection profiles in Scotland reveal mantle structures beneath a crust with a polyphase tectonic history that resulted in several generations of structures. Continuum mechanics suggests that coeval mantle and crustal structures must be kinematically linked. Inherited structures imply relative ages for the reflectors, ages that can be placed into the context of the geological history of the near-surface rocks of northern Scotland. Thus, some mantle reflectors are assigned Triassic ages related to the opening of the West Orkney and related marginal basins of the Atlantic Ocean. Other mantle reflectors are cut by late Caledonian structures associated with the Great Glen Fault Zone and therefore older than
c.
400 Ma. Many of these structures also track the late Precambrian margin of Laurentia and may be related to either the opening (900–600 Ma) or closing (500–600 Ma) of the Iapetus Ocean. Some reflective structures may also be attributed to 1800–1700 Ma Laxfordian deformation that was part of a global-scale orogenic belt.
Patterns of basement structure and reactivation along the NE Atlantic margin
Authors: DORÉ A. G. , LUNDIN E. R. , FICHLER C. , OLESEN O.
Published: December 2007

A lineament pattern on the NE Atlantic margin is discussed, illustrated by gravity and magnetic images in the Norwegian Sea, and reviewed in the context of onshore field evidence. While most possible fault trends exist, three major sets predominate. A NE-SW left-stepping lineament set defines the gross geometry of the margin, while interposing northerly trends impose a rhomboidal geometry at a variety of scales. The margin is segmented by NW-SE transfer zones, sometimes involving significant offsets. The principal trends are primarily a function of Mesozoic-Cenozoic plate-wide extensional stress fields. Certain Proterozoic and Caledonian lineaments were, however, opportunistically reactivated according to the extension direction. Caledonian NE-SW orogen-oblique shears, typified by the Møre-Trøndelag Fault Zone, were reactivated via (?Jurassic) strike-slip or oblique-slip, and were further exploited during Cretaceous-early Cenozoic extensional episodes leading to continental break-up. Jurassic E-W extension may also have reactivated N-S faults existing in the basement or generated in duplex systems between the NE-SW shears. Precambrian and Caledonian basement lineaments striking at a low angle to the extension direction probably predisposed the formation of major transfer zones.
The Thabazimbi-Murchison Lineament of the Kaapvaal Craton, South Africa: 2700 Ma of episodic deformation
Authors: GOOD NADINE , DE WIT MAARTEN J.
Published: December 2007

The Thabazimbi–Murchison Lineament is a prominent tectonic feature extending for approximately 500 km in a NNE–SSW direction across the Kaapvaal Craton. The lineament has a tectonic history of more than 2.5 Ga, because it appears to form and/or influence: the boundary between the Archaean granite/greenstone terrain of the Kaapvaal Craton and the southern margin of the high grade terrain of the Limpopo Mobile Belt; the northern margin of the Archaean-Proterozoic Transvaal Basin; the southern margin of the Mesoproterozoic Waterberg Basin; and has probably also influenced the emplacement of the Mesoproterozoic Bushveld Complex. Mesozoic Karoo basalts and sediments formed the Springbok Flats; these lavas erupted into half graben structures formed by the normal reactivation of the previously strike/slip Zebedelia Fault, part of the Thabazimbi-Murchison Relay System. The lineament is cut by a Mesozoic dyke swarm associated with the break up of Gondwana.
Fault-zone weakening processes along the reactivated Outer Hebrides Fault Zone, Scotland
Authors: IMBER J. , HOLDSWORTH R. E. , BUTLER C. A. , LLOYD G. E.
Published: December 2007

The Outer Hebrides Fault Zone is a major reactivated structure cutting amphibolite-grade Lewisian basement gneisses in NW Scotland. During a regionally important phase of sinistral strike-slip movements, the influx of chemically active hydrous fluids along the fault zone was associated with the formation of a network of greenschist-facies phyllonitic shear zones. Later ESE-directed extensional strain was preferentially focused into these pre-existing zones of weakness. The syn-tectonic alteration of a relatively strong, feldspar/hornblende-dominated load-bearing framework microstructure to an interconnected weak layer microstructure of fine-grained, strongly aligned phyllosilicate aggregates leads to the long-term weakening in the fault zone. Comparison with experimental data suggests that this produces a shallowing of the frictional-viscous creep ('brittle-ductile') transition and a substantial reduction in total crustal strength. Similar processes may account for the apparent weakness of many long-lived fault zones.
Controls on reactivation of a major fault zone: the Fair Head–Clew Bay line in Ireland
Authors: McCAFFREY K. J. W.
Published: December 2007

The Fair Head–Clew bay line, a major Caledonian fault zone in Ireland was reactivated throughout the Palaeozoic. At a regional scale, basement configuration controlled fault zone segmentation and the response to plate vector variations during and after plate collision. In the Ox Mountains inlier, mid-crustal deformation partitioning in both metasedimentary and igneous rocks influenced the formation of a sinistral Early to Mid-Devonian pull-apart basin. Subsequent reactivation by Late Devonian dextral strike-slip and Early Carboniferous normal faulting was focused on the margins of a structural high formed by the then exhumed Ox Mountains metamorphic block.
The emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and pH front
Authors: RUSSELL M. J. , HALL A. J.
Published: December 2007

Here we argue that life emerged on Earth from a redox and pH front at
c.
4.2 Ga. This front occurred where hot
(c.
150°C), extremely reduced, alkaline, bisulphide-bearing, submarine seepage waters interfaced with the acid, warm
(c.
90°C), iron-bearing Hadean ocean. The low pH of the ocean was imparted by the ten bars of CO
2
considered to dominate the Hadean atmosphere/hydrosphere. Disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal FeS membrane. Iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites. Our hypothesis is that the FeS membrane, laced with nickel, acted as a semipermeable catalytic boundary between the two fluids, encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers. The ocean provided carbonate, phosphate, iron, nickel and protons; the hydrothermal solution was the source of ammonia, acetate, HS
−
, H
2
and tungsten, as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde. The mean redox potential (ΔEh) across the membrane, with the energy to drive synthesis, would have approximated to 300 millivolts. The generation of organic anions would have led to an increase in osmotic pressure within the FeS bubbles. Thus osmotic pressure could take over from hydraulic pressure as the driving force for distension, budding and reproduction of the bubbles.

Condensation of the organic molecules to polymers, particularly organic sulphides, was driven by pyrophosphate hydrolysis. Regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the Hadean ocean. This was the first use by a metabolizing system of protonmotive force (driven by natural ApH) which also would have amounted to
c.
300 millivolts. Protonmotive force is the universal energy transduction mechanism of life. Taken together with the redox potential across the membrane, the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt.

The role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers. This organic take-over of the membrane material led to the miniaturization of the metabolizing system. Information systems to govern replication could have developed penecontemporaneously in this same milieu. But iron, sulphur and phosphate, inorganic components of earliest life, continued to be involved in metabolism.
Three-dimensional interplay of advective and diffusive processes in the generation of sequence boundaries
Authors: KARNER GARRY D. , DRISCOLL NEAL W.
Published: December 2007

Quantitative stratigraphic models have been generated using either geometric constructs or diffusion algorithms to simulate the development and timing of sequence boundaries and how they vary in response to tectonics, eustasy, climate, and sediment supply. While diffusion models provide a physical basis for the generation of clinoforms, the resulting model predictions appear to do little more than track the transgressive and regressive movements of the shoreline. On the other hand, geometric models do a relatively good job in simulating the observed stratigraphy but offer little in actually ascertaining the physics controlling the processes of deposition and erosion. All these stratigraphic models fail to predict the most fundamental response of depositional systems, namely, the development of a downward shift in coastal onlap during a fall in relative sea level. This basinward shift and the development of an onlap surface are the critical observations that define chronostratigraphic sequences and are not simply a consequence of shoreline transgressions and regressions. A major assumption in these two-dimensional models is that the observed stacking patterns are solely the consequence of deposition processes and sediment transport within the modelling section, in marked contrast to the observation that the major sediment transport direction along margins is sub-parallel to the margin. We present a variation on the diffusion theme in which across-margin transport and deposition are dominated by advection-type processes and along-margin erosion and deposition processes are dominated by diffusion. With this combination of advection and diffusion it is possible to generate a lowstand system tract and sequence boundaries (i.e., onlap surfaces). In particular, the generation of the lowstand system tract is, in large part, the result of depositional processes operative along the margin (i.e., out of the section).
Geological implications from geochemical and isotopic studies of Upper Cretaceous and Lower Tertiary igneous rocks around the northern Rockall Trough
Authors: HITCHEN K. , MORTON A. C. , MEARNS E. W. , WHITEHOUSE M. , STOKER M. S.
Published: December 2007

Major, trace, rare-earth element geochemistry and isotopic data have been obtained for offshore igneous rocks from around the northern Rockall Trough, NE Atlantic Ocean. Most comprise basalts derived from the sub Rockall-Hebridean asthenospheric mantle, but subcontinental lithospheric mantle generated the phono-tephrites of Rosemary Bank, and melting of upper crust was responsible for the peraluminous dacites of well 163/6-1A. Crustal contamination of the lavas around the Rockall Trough suggests that the Lewisian-Islay (Rockall Bank) basement terrane boundary crosses the trough and passes between George Bligh and Rockall Banks. Basalts representing uncontaminated mantle-derived material are scarce, but the available data indicate that the Cretaceous basalts of Rosemary Bank and Anton Dohrn have higher
206
Pb/
204
Pb ratios than the younger Palaeocene lavas of Rockall Bank, the Hebrides Shelf and well 163/6-1A, implying significant geographic and/or temporal changes in mantle composition.
Structural modelling of regional depth profiles in the Vøring Basin: implications for the structural and stratigraphic development of the Norwegian passive margin
Authors: WALKER I. M. , BERRY K. A. , BRUCE J. R. , BYSTØL L. , SNOW J. H.
Published: December 2007

Interpretation of key regional seismic lines across the Vøring Basin has identified a number of seismic megasequences that have provided a framework for further basin analysis. These megasequences have been classified as pre-, syn- and post-rift with respect to the late Cretaceous-early Tertiary phase of extension. Forward and reverse structural and stratigraphic modelling of two of these regional lines has been performed in an attempt to test and validate the structural and stratigraphic interpretations of the syn and post-rift megasequences.

Reverse thermal subsidence modelling (flexural backstripping) of these lines to the base Tertiary was performed using a laterally varying beta factor across the sections. A number of features on each of the depth profiles are considered to be regional subaerial datums for the backstripped sections. The backstripped templates were then forward modelled using the flexural cantilever model. The forward models calculate a laterally varying beta profile along their length which can be compared to the reverse models, thereby ensuring an internally consistent structural model between both the reverse and forward modelling techniques.

The modelling work has highlighted the existence of a significant discrepancy between the extension measured from the forward models (fault heaves) and the extension needed to produce geologically-acceptable backstripped profiles. This observation is of particular importance as it may place a significant constraint on the mode of lithospheric extension that can be used to explain the evolution of the Norwegian continental margin.
High-Resolution carbon isotope stratigraphy of the basal Silurian Stratotype (Dob's Linn, Scotland) and its global correlation
Authors: UNDERWOOD C. J. , CROWLEY S. F. , MARSHALL J. D. , BRENCHLEY P. J.
Published: December 2007

Since its designation as the Global Stratotype Section and Point (GSSP) for the base of the Silurian System, the choice of Dob's Linn, Southern Scotland, has received criticism due to the difficulties of relating its well-constrained graptolite biostratigraphy to shallow-water sequences elsewhere. Kerogen samples from across the Ordovician-Silurian boundary interval at Dob's Linn have yielded carbon stable-isotope signatures consistent with those recorded elsewhere, in particular showing a clear positive δ
13
C excursion in the terminal Ordovician. The architecture of the δ
13
C curve from Dob's Linn enables very high-resolution stratigraphic subdivision and direct correlation between the deep water Dob's Linn section and time-equivalent carbonate shelf deposits. An integrated stratigraphic scheme using isotope stratigraphy and biostratigraphy of graptolites, conodonts and shelly faunas has been constructed. This direct correlation shows that the shallow water successions, including the former stratotype candidate at Anticosti Island, are generally incomplete, with hiatuses related to the rapid sea-level changes during the Hirnantian stage. This confirms and greatly increases the global utility of Dob's Linn as a boundary stratotype.
Palaeogene-Neogene/present day(?) growth folding in the Bahamian foreland of the Cuban fold and thrust belt
Authors: MASAFERRO JOSE L. , POBLET JOSEP , BULNES MAYTE , EBERLI GREGOR P. , DIXON TIMOTHY H. , McCLAY K.E.N.
Published: December 2007

The Santaren Anticline constitutes the frontal termination of the Cuban fold and thrust belt within the Bahamian foreland. New well and seismic data allow us to constrain in detail the evolution of this anticline. Pre-growth and syntectonic (partly post-tectonic?) units, separated by a major unconformity, are associated with the Santaren Anticline. Their geometrical features are consistent with a detachment fold. The precise age of the beginning of fold growth remains unknown. However, the complete record of well-dated syntectonic sediments documents its kinematic evolution from Mid-Eocene to Pliocene/present day, and reveals an approximately constant and very slow growth rate from Early Miocene to Pliocene/present day. The timing of evolution of the Santaren Anticline is not consistent with previous models that postulate that deformation associated with the Cuban fold and thrust belt ended in the Eocene. Our data suggest that the most external part of the Cuban fold and thrust belt was still being deformed under a compressional regime during the late Palaeogene, Neogene and probably during the Quaternary. We propose that this folding may result from compressive stresses transmitted approximately 400 km northwards from the actual plate boundary, as a result of slow convergence between the N and S American plates.
Strontium isotope correlation of the basal Maastrichtian Stage in Antarctica to the European and US biostratigraphic schemes
Authors: CRAME J. A. , McARTHUR J. M. , PIRRIE D. , RIDING J. B.
Published: December 2007

New
87
Sr/
86
Sr dating allows the correlation of a marker horizon within the prolific Late Cretaceous
Gunnarites antarcticus
faunal assemblage of the Cape Lamb Member, Snow Hill Island Formation, Vega Island, Antarctica with reference sections in Europe and the USA. This horizon is between 81.5 and 96.5 m above the base of the
G antarcticus
assemblage. Replicate analysis of six macrofossils from within it yielded a mean value for
87
Sr/
86
Sr of 0.707 735 9 ± 0.000 004 3 (± 2 s.e.,
n
=17). This ratio in turn yields a numerical age of 71.0 ± 0.2 Ma when compared to the standard
87
Sr/
s6
Sr reference curve for the latest Cretaceous, for which the Campanian-Maastrichtian boundary is placed at 71.3 ± 0.5 Ma. The value of 0.707 735 9 ± 0.000 004 3 correlates to a level in the
Belemnella lanceolata
belemnite Zone of the Chalk of northwestern Germany that is 2.5 ± 5 m beneath the base of the overlying
B. pseudobtusa
Zone (and 7.5 m above the Campanian-Maastrichtian belemnite boundary), and to an interval within the ammonite zonation of the US Western Interior that spans the early Maastrichtian
Baculites baculus
and
B. eliasi
zones, but with a most likely level within the
B. eliasi
Zone. An earliest Maastrichtian age is thereby determined for the Antarctic horizon, and indeed for the entire
G. antarcticus
assemblage.
Gunnarites, sensu lato,
is an important ammonite marker for the base of the Maastrichtian throughout the southern high-latitude regions, and the associated large heteromorph ammonite
Diplomoceras
may comprise a macrofossil link back to the Maastrichtian type sections.
Palaeoenvironments of Early Miocene Kisingiri volcano
Proconsul
sites: evidence from carbon isotopes, palaeosols and hydromagmatic deposits
Authors: BESTLAND ERICK A. , KRULL EVELYN S.
Published: December 2007

Early Miocene (
c.
18 Ma) hominoid sites
(Proconsul)
from Rusinga Island, Lake Victoria occur in palaeosols and volcaniclastic strata deposited in a semi-arid, seasonal climate on the flanks of the active, low-relief edifice of the Kisingiri volcano. Palaeosols interbedded with sequences of primary pyroclastic deposits have stable carbon isotope values indicative of C3 vegetation from semi-arid environments. Isotopic values of palaeosol organic matter and pedogenic carbonate from the Rusinga Group have average δ
13
C of – 23.8 ± 0.8 and – 7.7 ± l.l‰, respectively, considerably heavier than average C3 vegetation. These isotopic values were most likely caused by reduced photosynthetic fractionation under water-stressed conditions. Prolonged dry seasons and semi-arid precipitation levels for Rusinga Group fossil soils are also supported by the profile depth of calcareous horizons and vertic clay structures.

The principal fossil-bearing units of the Rusinga Group (Kiahera and Hiwegi formations) are dominated by sandy strata which are interbedded with palaeosols and have features indicative of hydromagmatic pyroclastic deposition. Pyroclastic surge features include very low-angle cross-bedding, low amplitude and long-wavelength dune bedforms, moderate to poorly sorted layers of tuffaceous and pebbly sandstones, and common, isolated cobbles and boulder clasts of Precambrian basement rocks with associated impact sags. These features are interpreted as the deposits of pyroclastic surge dune bedforms and ballistically implaced volcanic ejecta, both produced by powerful hydromagmatic explosions from the Kisingiri volcano. According to this interpretation, the initial stages of this carbonatite-nephelinite volcano had repeated episodes of hydromagmatic eruptions which built a large (15–20 km radius), low-relief tuff ring or maar volcano. The palaeosol sequences interbedded with the primary pyroclastic deposits represent periods of volcanic quiescence lasting hundreds to thousands of years. Thus,
Proconsul
and associated fauna and flora inhabited a frequently disturbed landscape that experienced repeated catastrophic volcanic deposition in an overall semi-arid seasonal climate.
Linking onshore and offshore structures: Mesozoic extension in the Scottish Highlands
Authors: ROBERTS A. M. , HOLDSWORTH R. E.
Published: December 2007

Geological relationships in the offshore basins flanking northern Scotland suggest that a regional Caledonian control on the structure of these basins is far from proven, but conversely Mesozoic faults of the offshore set may extend onshore. The Strathconnon fault, long held to be late Caledonian, may be Mesozoic in age, forming the principal kinematic link between the east and west coast basins of northern Scotland. The numerous outcrops of Precambrian basement within the Minch/Hebrides basin nearly all lie in the uplifted footwalls of Mesozoic faults. Similar fault controls on the distribution of onshore outcrop within the Precambrian may exist.
Tectonic evolution of the Taimyr Peninsula, northern Russia: implications for Arctic continental assembly
Authors: INGER S. , SCOTT R. A. , GOLIONKO B. G.
Published: December 2007

New field data from the Taimyr Peninsula, northern Russia, indicate that models for the tectonic evolution of Arctic Eurasia need substantial reassessment. The late Palaeozoic structural history of central Taimyr is characterized by thin-skinned thrusting that may be related to the Permo-Carboniferous Uralian orogeny, with southern Taimyr as the distal foreland. These structures were reworked in later folding and strike-slip regimes of probable Late Triassic age. The new model suggests that no oceanic tract survived between the Arctic continental mass and western Siberia after the Permian, and has implications for understanding sediment dispersal and deformation over a vast region.
Some aspects of the geochemistry, provenance and palaeoclimatology of the Torridonian of NW Scotland
Authors: YOUNG GRANT M.
Published: December 2007

Geochemical data, mostly from mudstones, are used in an attempt to investigate some aspects of the palaeoclimatology and provenance of the Torridonian succession in NW Scotland. The basal part of the Stoer Group, which has been interpreted as glaciogenic is thought to have formed in a warm arid setting. The presence of oscillation ripples and desiccation cracks in mudstones containing isolated clasts is thought to preclude their interpretation as ice-rafted debris. Some aspects of the major element geochemistry of the Stoer Group mudstones suggest deposition in an environment with little weathering, but chemical weathering is inhibited in both frigid and arid settings and sedimentological evidence favours the latter. The Stoer Group mudstones are enriched in Mg, Ca and Na relative to the Torridon Group samples, which are much closer in composition to an average shale estimate (PAAS). The Cr and Ni contents of the Stoer mudstones are significantly higher than those of the Torridon Group samples. There is, however, no evidence that enrichment in these elements was due to contamination with volcanic material like that of the Stac Fada Member. The Scourian basement appears to be an adequate source of the Ni and Cr in the Stoer Group sediments. Th/Sc ratios are higher in the Torridon than in the Stoer mudstones. This difference is interpreted as indicating that the Stoer mudstones were largely derived from local Archaean sources but that the Torridon Group mudstones incorporated materials from a much wider provenance, including younger and recycled materials. Evidence from rare earth elements also provides evidence for different source terrains for the Stoer and Torridon Groups. The Torridon Group mudstones are more weathered, have a higher REE content and display a more prominent Eu anomaly (lower value for Eu/Eu*) than do the Stoer samples. These results support evidence from Th/Sc ratios, that the Torridon Group was derived from a more varied, recycled and granite-rich terrain than the Stoer, much of which appears to have relatively local provenance. The geochemistry of mudstones can shed considerable light on problems of provenance and palaeoclimatology, because many useful trace elements tend to be concentrated in such fine grained rocks and some aspects of their major element chemistry may be related to climatic factors.
U–Pb geochronology of regional migmatites in East Sutherland, Scotland: evidence for crustal melting during the Caledonian orogeny
Authors: KINNY P. D. , FRIEND C. R. L. , STRACHAN R. A. , WATT G. R. , BURNS I. M.
Published: December 2007

Moine semi-pelitic metasediments near the base of the Kirtomy and Naver nappes, northern Scotland, were partially melted syn-tectonically under low
T,
high
a

H
2
O

conditions. Migmatites from the Kirtomy and Naver nappes have been dated using SHRIMP U-Pb geochronology. Zircon rims which grew during migmatization have mean
206
Pb/
238
U ages of 461 ± 13 Ma (2σ) (Kirtomy) and 467 ± 10 Ma (2σ) (Naver). These ages demonstrate the reality of a Middle Ordovician (Taconic) tectonothermal event in the Caledonides of northern Scotland. Monazites from the Kirtomy migmatite have a younger mean
206
Pb/
238
U age of 431 ±10 Ma (2σ). This may date either a late, low amphibolite facies overprint associated with steepening of part of the nappe pile, cooling through the closure temperature of monazite for radiogenic Pb, or cessation of fluid flow along the Kirtomy Thrust.

Original detrital zircons from the sedimentary precursors of both migmatites fall mostly into the age range: 1850–1000 Ma, demonstrating that deposition of the Moine sediments in Sutherland occurred after
c.
1000 Ma, following the culmination of Grenvillian orogenic activity in the North Atlantic region. Only two Archaean grains were found, demonstrating that Lewisian gneisses of the foreland to the Caledonian were not the source.
A concrete framework for environment machines
Authors: Biernacka Małgorzata , Danvy Olivier
Published: December 2007

We materialize the common understanding that calculi with explicit substitutions provide an intermediate step between an abstract specification of substitution in the lambda-calculus and its concrete implementations. To this end, we go back to Curien's original calculus of closures (an early calculus with explicit substitutions), we extend it minimally so that it can also express one-step reduction strategies, and we methodically derive a series of environment machines from the specification of two one-step reduction strategies for the lambda-calculus: normal order and applicative order. The derivation extends Danvy and Nielsen's refocusing-based construction of abstract machines with two new steps: one for coalescing two successive transitions into one, and the other for unfolding a closure into a term and an environment in the resulting abstract machine. The resulting environment machines include both the Krivine machine and the original version of Krivine's machine, Felleisen et al.'s CEK machine, and Leroy's Zinc abstract machine.
Outlier detection by logic programming
Authors: Angiulli Fabrizio , Greco Gianluigi , Palopoli Luigi
Published: December 2007

The development of effective knowledge discovery techniques has become a very active research area in recent years due to the important impact it has had in several relevant application domains. One interesting task therein is that of singling out anomalous individuals from a given population, for example, to detect rare events in time-series analysis settings, or to identify objects whose behavior is deviant w.r.t. a codified standard set of rules. Such exceptional individuals are usually referred to as outliers in the literature.

In this article, the concept of outlier is formally stated in the context of knowledge-based systems, by generalizing that originally proposed in Angiulli et al. [2003] in the context of default theories. The chosen formal framework here is that of logic programming, wherein potential applications of techniques for outlier detection are thoroughly discussed. The proposed formalization is a novel one and helps to shed light on the nature of outliers occurring in logic bases. Also the exploitation of minimality criteria in outlier detection is illustrated.

The computational complexity of outlier detection problems arising in this novel setting is also thoroughly investigated and accounted for in the paper. Finally, rewriting algorithms are proposed that transform any outlier detection problem into an equivalent inference problem under stable model semantics, thereby making outlier computation effective and realizable on top of any stable model solver.
Memory scheduling for modern microprocessors
Authors: Hur Ibrahim , Lin Calvin
Published: December 2007

The need to carefully schedule memory operations has increased as memory performance has become increasingly important to overall system performance. This article describes the adaptive history-based (AHB) scheduler, which uses the history of recently scheduled operations to provide three conceptual benefits: (1) it allows the scheduler to better reason about the delays associated with its scheduling decisions, (2) it provides a mechanism for combining multiple constraints, which is important for increasingly complex DRAM structures, and (3) it allows the scheduler to select operations so that they match the program's mixture of Reads and Writes, thereby avoiding certain bottlenecks within the memory controller.

We have previously evaluated this scheduler in the context of the IBM Power5. When compared with the state of the art, this scheduler improves performance by 15.6%, 9.9%, and 7.6% for the Stream, NAS, and commercial benchmarks, respectively. This article expands our understanding of the AHB scheduler in a variety of ways. Looking backwards, we describe the scheduler in the context of prior work that focused exclusively on avoiding bank conflicts, and we show that the AHB scheduler is superior for the IBM Power5, which we argue will be representative of future microprocessor memory controllers. Looking forwards, we evaluate this scheduler in the context of future systems by varying a number of microarchitectural features and hardware parameters. For example, we show that the benefit of this scheduler increases as we move to multithreaded environments.
Incorporating cognitive/learning styles in a general-purpose adaptive hypermedia system
Authors: Stash Natalia
Published: December 2007

Natalia Stash received her PhD from the Eindhoven University of Technology (TU/e), The Netherlands. The title of her thesis is "Incorporating Cognitive/Learning Styles in a General-Purpose Adaptive Hypermedia System". She currently participates in the CHIP project (Cultural Heritage Information Personalization) located at the Rijksmuseum in Amsterdam. Her research interests include adaptive web-based systems, semantic web technologies, learning styles, e-culture applications.