bluuebunny/crossref_metadata_2025 huggingface dataset:
Eocene sedimentation and tectonics in the Hampshire Basin
Authors: Plint A. G.
Published: December 2007

Sedimentary evidence in the Eocene (Cuisian-Lutetian) of the Hampshire Basin indicates important intra-Eocene movement on the Isle of Wight and Purbeck Monoclines, and on the Ridgeway Fault. Evidence for syn-depositional movement includes Jurassic and Cretaceous chert and flint pebbles in the Eocene, the distribution of which suggests derivation from both E and W. At Whitecliff Bay, two units of cross-bedded sand have northward-directed palaeocurrents and may have been deposited as localized fans of debris reworked from earlier Tertiary sediments on the upwarped side of the monocline. Three units of laminated muds are intercalated with marine sediments in the eastern part of the basin and suggest periods of low salinity, tideless conditions. These episodes are attributed to the periodic isolation of the Hampshire Basin from the fully marine Dieppe Basin to the SE. This may have been the result of intermittent movement on a tectonic barrier to the SE of Selsey. The onset of uplift and subsequent exposure of the Chalk along the southern margin of the basin proceeded unevenly from ?early Cuisian to late Lutetian times. Movement on the Portsdown Anticline probably occurred over a similar period. The Isle of Wight and Purbeck Monoclines are the superficial expressions of faults in the Palaeozoic basement, and not the result of lateral ‘Alpine’ pressures. A minor series of syn-depositional folds trend NW-SE across the basin and may reflect a component of sinistral strike-slip on basement faults.
Late Cretaceous and early Miocene Andean-type plutonic activity in northern Makran and Central Iran
Authors: Berberian F. , Muir I. D. , Pankhurst R. J. , Berberian M.
Published: December 2007

Two calc-alkaline plutonic complexes. Bazman and Natanz, intruded through the south-eastern active and south-western ancient continental margins of Central Iran, Have been dated by the Rb-Sr whole-rock isochron method at 74 ± 2 and 24 ± 4.5 Ma, respectively. Detailed trace element studies together with low
87
Sr/
86
Sr initial ratios (<0.706) indicate that these complexes represent parts of an Andean-type magmatic are formed in response to subduction of Tethyan oceanic crust beneath Central Iran. Geochemical data on the igneous rocks at Bazman suggest that subduction of the Oman oceanic crust was well established by the late Cretaceous. On the evidence of the Natanz rocks, the Arabian-Central Iranian collision did not occur during the late Cretaceous, but took place during late Paleogene or early Neogene time. The Natanz low-Rb diorites and gabbros cannot be comagmatic with the more salic rocks, for they have distinctly lower
87
Sr/
86
Sr ratios and the gabbros, at least, were intruded some 10 Ma earlier.
Rb-Sr isotope study of latest Proterozoic volcano-sedimentary belts in the Central Arabian Shield
Authors: Darbyshire D. P. F. , Jackson N. J. , Ramsay C. R. , Roobol M. J.
Published: December 2007

Five new Rb-Sr whole-rock isochrons for volcanic successions assigned to 'sequence' A in the Central Arabian Shield indicate that very late Precambrian
c
.690–570 Ma volcanicity was an important event in the evolution of the shield. The following ages are considered to define or approximate to the age of lava extrusion: Fatimah group— 688 ± 30 Ma; Jahhad unit—616 ± 13 Ma; Juqjuq formation— 612 ± 22 Ma; Arfan formation— 608 ± 9 Ma; Hummah unit— 572 ± 23 Ma. Initial
87
Sr/
86
Sr ratios range from 0.7027 to 0.7036, and Rb/Sr ratios are uniformly low (<0.4), except for a few metarhyolites. All the lavas appear to have been derived from a primitive mantle-type source, although a slight increase of initial
87
Srl
86
Sr ratio for the Jahhad and Hummah samples reflects the involvement of less-depleted mantle or possibly slight crustal contamination.
Geochemistry and petrogenesis of the Derbyshire Carboniferous basalts
Authors: Macdonald R. , Gass K. N. , Thorpe R. S. , Gass I. G.
Published: December 2007

Dinantian volcanism in Derbyshire was associated with minor phases of isostatic uplift of a shallow carbonate platform on the northern margin of the St. George's Land E-W land mass. The mainly tholeiitic magmas were generated by varying degrees of partial melting of heterogeneous mantle sources followed by fractional crystallization and final equilibration mainly within the lower crust. Large, high-level magma chambers were not established. Even single lava sequences, such as the Miller's Dale Lava, represent several, isolated magmatic phases. Volcanism was of within-plate type. Magmas generated in isolated mantle pockets rose to the surface through crust attenuated by lithospheric stretching.
Depositional history of the late Pleistocene limestones of the Kenya coast
Authors: Braithwaite C. J. R.
Published: December 2007

The coastal limestones of Kenya extend approximately 180 km N-S from Malindi to the Tanzanian border. They are at least 20 m thick and may be subdivided into sedimentary units representing major periods of marine deposition punctuated by sub-aerial erosion.

Their foundations are formed by thick fluvial and aeolian quartz sands but there is local evidence of marine deposition following these. In the main limestone unit, deposited about 240,000 years ago, initial high energy shallow-shelf deposition was replaced by quiet water sediments with scattered corals. Sea level stood about 8 m higher than at present. Quartzose sands were confined to western areas.

A return to shallow water heralded a new phase of emergence and erosion, producing karst surfaces and sub-aerial sediments. These are overlain by herring-bone cross-bedded quartz-rich calcarenites which were the products of a tidally dominated shelf and, at Watamu and Wasini, pass upwards into aeolian dune deposits. However, these were also emersed and subject to karst erosion before deposition of a further widespread marine limestone. Within this, coral knolls are well developed. Much of the sediment accumulated in shallow water, but the ecological succession indicates that knolls were at times in deeper waters. These deposits formed about 125,000 years ago when sea level ultimately stood 15–20 m above its present position.

More recently in the area sea level has again fallen. However, the descent was not continuous and pauses were marked by marine terrace formation and subsequent karst erosion with sub-aerial deposition. Brief reversals caused both terraces and sediments to be overlain by thin marine deposits. Sea level paused at its present position about 30,000 years ago when the present reef platform was probably defined. It continued to fall to a maximum of about-120 m before rising to its existing level 7000 years ago and beginning the current cycle of sediment accumulation.
The petrology and mineralogy of Mt. Popa Volcano and the nature of the late-Cenozoic Burma Volcanic Arc
Authors: Stephenson D. , Marshall T. R.
Published: December 2007

Mt. Popa is situated on a line of widely-spaced, calc-alkaline volcanic centres in the central lowlands of Burma. Latites, rhyodacites, and ignimbrites are interbedded with strongly-folded arenaceous sediments of topmost Miocene and Pliocene age. These are overlain unconformably by a composite cone of basalt and basaltic andesite lavas and pyroclastic deposits of Pleistocene or early Recent age.

The two groups of lavas are regarded as a single petrographic suite in which several continuous and discontinuous mineral reaction series are recognized. Phenocryst phases, analysed by microprobe, are: olivine, bronzite-hypersthene, biotite, diopsidic augite-salite, magnesio-hastingsite-magnesio-hornblende, titaniferous magnetite, bytownite-oligoclase, and sanidine. Whole-rock analyses are characterized by relatively high K, Ba, Sr, Rb, and Zr. High Mg/(Mg + Fe") ratios of 0.85 to 0.65 in both phenocrysts and whole-rock, high K/Rb (767) and low Sr
87
/Sr
86
(0.70431) and Rb/Sr (0.0155) ratios suggest that the basalts are relatively primitive mantle-derived compositions, modified slightly by fractionation, with negligible crustal contamination. The more siliceous lavas may have been derived by fractional crystallization of such magmas at crustal levels.

This high-K calc-alkaline suite is typical of a continental margin orogenic environment. Analyses of contemporaneous lavas from elsewhere in Burma define three N-S volcanic lines which become more alkaline from W to E. The magmatism is attributed to the waning stages of orogeny as eastward subduction of the Indian plate beneath China gave way to strike-slip movement, associated with the Andaman Sea spreading-centre. Within this tectonic model, magmas were probably generated by hydrous mantle melting above dehydrating oceanic crust of the subduction zone.
A coal depositional model for the Durham Coal Measures of NE England
Authors: Fielding C. R.
Published: December 2007

The Upper Carboniferous (Westphalian) Coal Measures of the Durham coalfield were deposited on a broad, flat, deltaic plain. In early Westphalian A times, a lower delta plain setting prevailed, evolving through southward deltaic progradation into an upper delta plain by mid-Westphalian A.

Detailed facies analysis of large, opencast exposures, supported by extensive subsurface data, has shown that a hierarchy of depositional controls operated across the Durham area during Westphalian times; (i) on the large scale, depositional geometry was controlled by patterns of major delta progradation and switching; (ii) on the medium scale, by a combination of structurally and compactionally induced subsidence, and (iii) on the small scale, by local sedimentary processes and subsidence patterns.

These observations form the basis of a coal depositional model for the Durham Coal Measures, which predicts that the thickest coals are to be found in upper delta plain domains controlled by compactional subsidence and not underlain by substantial channel sandstones. This model may also be applicable to other coalfields of northern England, and to ancient delta plain sequences elsewhere in the world.
U-Pb zircon geochronology and geological evolution of the Halaban-Al Amar region of the Eastern Arabian Shield, Kingdom of Saudi Arabia
Authors: Stacey J. S. , Stoeser D. B. , Greenwood W. R. , Fischer L. B.
Published: December 2007

U-Pb zircon model ages for eleven major units from the Halaban-Al Amar region of the eastern Arabian Shield indicate three stages of evolution: (1) plate convergence, (2) plate collision, and (3) post-orogenic intracratonic activity.

Convergence occurred between the western Afif and eastern Ar Rayn plates that were separated by oceanic crust. Remnants of oceanic crust now comprise the ophiolitic complexes of the Urd group. The oldest plutonic unit in the study is from one of these complexes and gave an age of 694 ± 8 Ma. Detrital zircons from the sedimentary Abt formation of the Urd group, which is intercalated with the ophiolitic rocks, were derived from source rocks with a mean age of 710 Ma. The Abt formation may be an accretionary wedge on the western margin of the Ar Rayn plate. Plate convergence was terminated by collision of the Afif and Ar Rayn plates during the Al Amar orogeny which began about 670 Ma. During collision, the Urd group rocks were deformed and in part obducted on to one or both plates. Synorogenic leucogranitoid rocks were intruded from 670 to 640 Ma. From about 640 to 630 Ma, widespread unfoliated dioritic plutons were emplaced in the Ar Rayn block, and represent the end of orogenesis related to collision. There is no definitive evidence for a significantly older basement beneath the study region.
Pressures and temperatures of metamorphism in the eastern Dalradian
Authors: Baker A. J.
Published: December 2007

Pressures and temperatures have been determined from locations in the eastern Dalradian using a number of different geothermometers and geobarometers. Temperatures range from 550°C in the low kyanite zone to about 800°C in the sillimanite–K feldspar zone. Pressures range from about 5.5 kbar in Glen Esk to 9–10 kbar in the Central Highlands. The barometric calibrations employed are consistent with the kyanite–sillimanite equilibrium.

Evidence from mineral zoning suggests that rocks outside the Buchan area (in the Duchray Hill Gneiss, Glens Clova and Avon and in the Schichallion area) underwent a pressure decrease synchronous with the metamorphic peak.

Regional temperature variations define a thermal high centred on the Cromar–Glen Muick–Duchray Hill Gneiss area. To the W of this high temperatures decrease rapidly. A sharp thermal break occurs between high grade sillimanite–K feldspar gneisses in Glen Muick and kyanite–staurolite schists to the W. This thermal contrast is attributed to a structural break which may be analogous to a number of other thermal features in the Dalradian.
A model for the MOIST seismic reflection profile, N Scotland
Authors: Blundell D. J. , Hurich C. A. , Smithson S. B.
Published: December 2007

An interpretation of the Moine and Outer Isles Seismic Traverse reflection profile along the north coast of Scotland is developed here by the construction of a model crustal cross section from which, by ray tracing, a synthetic seismic section has been prepared for comparison with the observed record section. Faults are modelled by narrow low velocity zones and the Moho by narrow high and low velocity zones. The geometry of the faults shown in the model is believed to imply that during the Caledonian Orogeny, crustal thickening was achieved by imbrication of thrust flakes from the SE, in which the thrust front propagated northwestward into the foreland and at the same time cut down so that the basal decollement deepened relative to the Moho, eventually into the mantle. Concomitant erosion and uplift initiated extension and the development of sedimentary basins in half-grabens.
The use of cluster analysis in the study of some non-marine bivalvia from the Westphalian D of the Sydney Coalfield, Nova Scotia, Canada
Authors: Vasey G. M. , Bowes G. E.
Published: December 2007

Cluster analysis is combined with Principal Components Analysis in an attempt to study the variation in shell-shape displayed by non-marine bivalves of the genusAnthraconautapruvost from the Sydney coalfield, Nova Scotia. Two assemblages of shells, 89 from above the Phalen seam and 91 from between the Harbour and Hub seams of the Westphalian D, are analysed.

The method requires the measurement of only six linear shell dimensions in order to produce a phenetic classification. The results are presented in the form of phenograms, stereo Principal Component plots and pictographs. Use of Principal Components Analysis allows the construction of reproducible pictographs with identified variational trends.

A new morphospecies,Anthraconauta calveri, is figured and described as a result of the analyses which are found to be broadly in agreement with the Trueman & Weir system of nomenclature presently in use for the classification of Upper Carboniferous non-marine bivalvia. Suggestions are made as to how this system of nomenclature might ultimately be modernized and revised
Stanniferous placer development on an evolving landsurface with special reference to placers near St Austell, Cornwall
Authors: Camm G. S. , Hosking K. F. G.
Published: December 2007

The geomorphic setting of the stanniferous placers of SW England is presented and the history of their development is broadly drawn. In particular, the relationships between the placers and the major types of primary tin deposit in the region are emphasized. The nature and genesis of three placer deposits in the N St Austell district are treated in some detail in order to demonstrate the complexity of placer development in the region as a whole. Stress is placed on an examination of the placer cassiterite morphology to determine the complex genesis of the Cornish deposits. Finally, it is emphasized that the initial stages of placer development in the region are due essentially to processes of disintegration, with processes of decomposition never playing more than a very minor role.
Carboniferous magnetostratigraphy
Authors: Palmer J. A. , Perry S. P. G. , Tarling D. H.
Published: December 2007

A review of the available data on the polarity of the geomagnetic field during the Carboniferous confirms that it is predominantly reversed, although the data base is only of poor reliability, particularly in terms of the age of the magnetization. New British and Irish data, partially supported by positive fold tests, suggest that the Courceyan and Arundian stages are almost certainly entirely reversed. The Asbian and Brigantian are similarly all reversed, with the exception of two short normal polarity intervals—one at the base and one at the top of the Asbian. An examination of the suggested age for the base of the predominantly Kiaman interval of reversed polarity shows a very wide variation in postulated ages, and it is proposed that the base is defined as being that of the youngest normal interval that can be identified near to the Permo-Carboniferous boundary.
Remanence acquisition in red beds from the Coal Measures of Central England
Authors: Turner P. , Vaughan D. J. , Besly B.
Published: December 2007

The magnetic mineralogy, palaeomagnetism, and magnetic fabric of a Carboniferous mudstone-dominated red bed sequence and associated sandstones are described. Natural remanent magnetization (NRM) is carried by hematite both as relatively coarse particles and as pigmentary material; magnetite and goethite also contribute to the remanence of some mudstones. The magnetization of red sandstones is carried exclusively by hematite. Magnetic carriers have been identified using a combination of rock magnetic measurements, X-ray diffraction and
57
Fe Mössbauer spectroscopy.

Both sandstones and mudstones carry a primary style magnetic fabric apparently related to the deposition of hematite particles. The reddening is associated with areas which developed better drainage and is genetically related to complex palaeosols in the mudstones, a feature indicating that it (and the magnetization) must have been approximately contemporaneous with sediment deposition.
Upper Palaeozoic ophiolite generation and obduction in south Cornwall
Authors: BARNES R. P. , ANDREWS J. R.
Published: December 2007

The Gramscatho flysch sequence of south Cornwall, including the mélanges of the Meneage Formation, and the Lizard ophiolite are described in relation to the development of the Gramscatho basin. The timing and geotectonic evolution of this feature are considered in its regional context within the Rhenohercynian zone of Northwest Europe. This zone is interpreted as an intracontinental dextral transform system that developed during the Devonian closure of the so-called Massif Central Ocean. A basin and rise topography is attributed to extension and compression at offsets on major faults. E–W extension of the Gramscatho pull-apart basin in Middle and Upper Devonian times is believed to have caused rifting and the development of ocean crust from which the Lizard ophiolite was assembled in an oceanic setting at a ridge-transform junction. The Meneage Formation was generated as a result of intrabasinal uplift on transcurrent faults. A major change of plate motions took place when the Massif Central Ocean finally closed at the end of the Devonian and the weak Rhenohercynian zone became a site of crustal convergence from which thrust nappes were transported northwards. Foreland basins were sequentially developed and deformed by thin-skinned tectonics as the system advanced northwards during the Carboniferous.
Seismic refraction investigation of the structural setting of the Lizard and Start complexes, SW England
Authors: DOODY J. J. , BROOKS M.
Published: December 2007

A long refraction line was established between the Lizard and Start peninsulas during a large-scale seismic experiment carried out in SW England during 1979. Interpretation of first arrival data indicates a shallow crustal structure consisting of two layers of regional extent. The upper layer of average velocity 5.15 km/s is interpreted as Devonian metasediments. The underlying layer with a velocity of about 6.10 km/s lies at a depth of several kilometres beneath the Lizard complex but rises eastwards to occur at or near surface in the Eddystone and Start areas. The lower layer is believed to represent a pre-Devonian crystalline basement of which the metamorphic rocks of Start and Eddystone are constituent parts. By contrast, the Lizard complex is interpreted as a thin surface sheet overlying Devonian metasediments.
Geochemical investigations of selected Eastern United States watersheds affected by acid deposition
Authors: BRICKER O. P.
Published: December 2007

The effects of acid deposition on surface waters in eastern United States watersheds having similar size, physiography, climate and land use are related to the composition of the underlying bedrock. Watersheds developed on greenstone, calcareous shale, sandstone, granite, and schist differ in their ability to neutralize acid deposition. Surface waters in watersheds developed on greenstone and calcareous shale are not discernably affected by acidification. Wastersheds developed on sand-stone have little capacity to neutralize acid rain; consequently, stream acidity is similar to that of precipitation. Watersheds developed on granite and schist are intermediate in their capacity to neutralize acid deposition. Bedrock composition appears to be the major property controlling surface-water chemistry in these systems; hydrologic flow paths and the nature of surficial materials and vegetation also influence chemical responses to acid deposition in watersheds.
Production, storage and output of coarse upland sediments: natural and artificial influences as revealed by research catchment studies
Authors: MOORE R. J. , NEWSON M. D.
Published: December 2007

Rates of sediment production in UK river basins are generally low; however, upland source areas control both runoff and sediment volumes to he routed through larger basins and there are indications that development pressures on land in upland areas have far-reaching implications. Output rates for bedload from semi-natural grassland and commercially-afforested catchments are now available for a ten-year period at the Plynlimon catchments, mid-Wales. The influence of forestry drainage practice is to increase bedload yields sixfold; suspended load yields are doubled. In an attempt to predict yields and to investigate the operation of storage and transport processes on bedload a regression analysis was conducted, using the weight of bedload trapped as a dependent variable, and selected climatic supply and transport factors as independent variables. The climatic supply factors chosen are shown to have little influence on yield, relative to transport factors, despite evidence of supply-limited yields. Tracer studies indicate that channel storage of material exercises a critical control on yield, a factor which is not accommodated by the climate-based supply indices. Implications for field measurement techniques are discussed.
Syn-orogenic alkaline magmatism and its relationship to the Moine Thrust Zone and the thermal state of the Lithosphere in NW Scotland
Authors: HALLIDAY A. N. , AFTALION M. , PARSONS I. , DICKIN A. P. , JOHNSON M. R. W.
Published: December 2007

The alkaline complexes of NW Scotland lie in a zone sub-parallel to the Moine thrust and represent the NW edge of the otherwise overwhelmingly calc-alkaline late-orogenic magmatism of the Caledonian fold-belt. The emplacement of intrusives in Assynt overlapped the thrust movements and new U-Pb zircon ages for the Loch Ailsh intrusion (439 ± 4 Ma) provide are liable bracket, when combined with existing age data for the Loch Borralan intrusion (430 ± 4 Ma), for the main movements on the Ben More thrust plane. A detailed history of the main tectonic and igneous events in the Moine Thrust Zone is tabulated. Zircons from the undeformed Cnoc-nan-Cuilean syenite, emplaced in Moine rocks near Loch Loyal, give an age of 426 ± 9 Ma, in contrast to the deformed Glen Dessary syenite for which earlier work gave 456 ± 5 Ma. The linear distribution of the alkaline complexes to the west of the calc-alkaline plutons, and the ultra-potassic character of the Loch Borralan complex (the most westerly), are consistent with, but do not prove, generation related to a W-dipping subduction zone. The persistence of the magmatism, over 30 Ma, in a belt being shortened by thrusting, suggests a source in the mantle lithosphere. The absence of magmatism further to the NW and the production of calc-alkaline magmas to the SE of this zone, is compatible with a model in which the thermal state of the lithosphere exercises the most important control on the nature of Late Caledonian magmatism.
The Southern Uplands Controversy
Authors: McKERROW W. S.
Published: December 2007

Report of a discussion meeting held at Burlington House on 12 February 1986

The idea for a discussion meeting followed from remarks made by Professor C. H.
Holland (1986)
in his Presidential Address to this Society in 1985, when he expressed concern about the uncritical application of the accretionary prism model to the Southern Uplands of Scotland. It has since become apparent that divergent views are held both among those against the model and those in favour of it. This meeting served to air some of these different opinions, even if it has not immediately resolved many of the arguments. Most of the contributors to the meeting (see the Society Newsletter for January 1985) have produced written papers for this volume, and so far only one or two have modified their views between writing their abstract and submitting their paper.

The concept of an accretionary prism model developed gradually. A comparison of Scotland with Burma suggested that the Southern Uplands were like western Burma where trench and oceanic sediments are being underthrust by subduction processes (
Mitchell & McKerrow 1975
). With the development of modern analogues from the Pacific (Seeley
et al.
1974; Karig & Sharman 1975), the model was applied to the Southern Uplands with more emphasis (

McKerrow
et al.
1977

;

Leggett
et al.
1979
a

,

b

, 1982
).
Moseley (1977
, 1978
) was one of the first to express doubts about this model; he believed that the Iapetus Ocean had closed by the end of the Ordovician, and thus, like many others
The Structure of the West Orkney Basin, northern Scotland
Authors: ENFIELD M. A. , COWARD M. P.
Published: December 2007

The West Orkney Basin developed in Devonian times, as the western part of the Orcadian intermontane basin. It has been studied using commercial speculative seismic reflection data and the MOIST deep seismic data. The NW edge of the West Orkney Basin is formed by listric faults which are also strongly arcuate in plan, while the SE part is composed of straight domino-type faults which formed parallel to earlier (Caledonian) layering in the basement. Fault restoration and balancing suggest that initial extension in the basin occurred on low-angle reactivated Caledonian thrust faults. Steeper breaching faults cut the low-angle set, forming planar (domino-type) faults in the centre of the basin but listric faults at the NW margin. The maximum extension is about 45% in the basin centre, most of this being taken up on the later breaching fault system. This extension decreases to the SW, where fault tips occur on-shore, but some may transfer to fault systems in the Minches. The faults apparently decouple at a depth of 18-20 km and the extension suggests an initial post-Caledonian crustal thickness of up to 40 km. However, the sedimentary thickness is an average of only 3 km in the basin centre, much less than would be expected had the lithosphere thinned homogeneously, and there is no evidence of a thermal subsidence phase to the basin. This suggests that the extension shown by the West Orkney Basin was transferred to lower lithospheric levels to the east along the deep decoupling zone.

The Devonian sediments on-land show facies changes and periods of uplift and erosion which may be related to extension during basin development. They also show a phase of pre-Late-Permian tectonic inversion where the beds are locally folded and thrusted, probably related to the Hercynian events further south. The West Orkney Basin is capped by Mesozoic sediments and was probably reactivated during Mesozoic basin development in the Minches and Moray Firth.

The shape of the faults, their orientation and decoupling levels are strongly controlled by the earlier Caledonian structure, in particular by the layering and crustal anisotropy developed along and above the Moine thrust. The West Orkney Basin with its 20 km deep decoupling level formed by extension of Caledonian thickened crust. It is notable that the major basin-bounding faults to the NW, the Outer Isles and Flannan faults, which developed where the crust was thinner and hence less ductile at depth, decoupled at much deeper structural levels, at the Moho or below.
Mesozoic reactivation of Variscan thrusting in the Bristol Channel area, UK
Authors: BROOKS M. , TRAYNER P. M. , TRIMBLE T. J.
Published: December 2007

New seismic reflection data from the Bristol Channel area provide direct evidence of a major Variscan thrust in the Palaeozoic basement beneath the Mesozoic Bristol Channel syncline. The thrust has an average southerly dip of about 25° and it rises into the major fault (the Central Bristol Channel fault zone, CBCFZ) at the northern margin of the Bristol Channel syncline. The CBCFZ is attributed to reactivation in extension of the Variscan thrust, probably during the early Cretaceous. There is no evidence for major synsedimentary movement on the CBCFZ, and the Bristol Channel syncline does not represent a rollover structure. Section restoration suggests that the CBCFZ has cut up through a previously tilted sequence of Triassic and Jurassic strata. Pervasive NNW–SSE cross faults are interpreted as original Variscan transfer faults that have been reactivated in the Mesozoic and Tertiary.
Short Paper: Evidence of negative structural inversion beneath central England from new seismic reflection data
Authors: CHADWICK R. A. , SMITH N. J. P.
Published: December 2007

A major seismic reflection transect, acquired by the British Geological Survey between 1984 and 1986, has elucidated the deep geology and structure of some well-known surface features of central England. The Worcester Basin, a Mesozoic extensional graben system, is bounded to west and east by major, sub-planar normal faults which formed by the extensional reactivation of much older structures; respectively the Malvern Axis and a similar though concealed structure forming its mirror image to the east. Within the Worcester Basin a thick Permo-Triassic sequence rests directly upon Precambrian basement rocks. To the west and east, Permo-Triassic rocks are thin or absent, but relatively thick Palaeozoic sequences are preserved above the Precambrian. These strikingly different successions, together with the fault geometry, suggest that the Worcester Basin lies within a major, inverted oblique-slip fault system or flower structure. In Palaeozoic times transpressivt stresses led to reverse faulting along the Malvern Axis and its complementary structure to the east with consequent regional uplift of the intervening tract and the formation of a positive flower structure. In Permian and early Mesozoic times, transtensional stresses caused collapse and negative inversion of the flower structure and consequent subsidence of the Worcester Basin.
The Caledonian and related geology of Scandinavia
Authors: GAYER R. A. , TOWNSEND C.
Published: December 2007

This conference was held at University College, Cardiff, 22–23 September 1987, in memory of Dr Sven Føyn, former Director of Norges Geologiske Undersøkelse, who with Professor J. G. C. Anderson in 1962 established the Norwegian Caledonides research group in the Department of Geology at University College, Cardiff. The group is now celebrating its 25th anniversary. The conference consisted of 35 talks and 10 poster presentations with c. 75 delegates attending, mainly from British and Scandinavian institutions.

The conference was introduced by
M. Brooks,
welcoming delegates to Cardiff, and was followed by a short session on basement geology.
T. Emmett
(CCAT Cambridge) described a series of dolerite dykes in the Jotun Nappe of S. Norway the geochemistry of which suggested that there had been a late Precambrian, pre-Caledonian extension of the Balto-Scandian continental margin.
I. Bryhni
(Oslo) followed with a description of the supracrustal rocks of the gneiss region of south Norway and the equivocal relationship of these rocks to the high pressure eclogitized rocks of the basement.

The second session concentrated on the geology of Finnmark in northernmost Norway.
B. Robins
(Bergen) discussed the relationship between deformation and emplacement of the Seiland Igneous Province and concluded that deformation had occurred prior to the youngest intrusion dated at 531 ± 3 Ma.
S. Daly
et al.
(UC Dublin, Leeds and Cardiff) presented Rb-Sr and U-Pb (zircon) ages of
c.
800Ma for granite bodies which cross-cut folds in the Kalak Nappe Complex, suggesting that the Klubben Group metasediments and the deformation
A new Ordovician–Silurian boundary section in San Juan Province, Argentina, and its definitive graptolite fauna
Authors: CUERDA A. J. , RICKARDS R. B. , CINGOLANI C.
Published: December 2007

Bed-by-bed collecting of the La Chilca Formation at Talacasto, San Juan, Argentina has revealed a sequence spanning the Ordovician–Silurian boundary, and the recognition of the following graptolite zones:
Glyptograptus persculptus
, probable
Parakidograptus acuminatus
and possible
Atavograptus.
The Talacasto section thus allows the closest definition of the Ordovician–Silurian boundary in South America. The shales of the La Chilca Formation are 3.65 m thick, rich in graptolites, and have allowed us to recognize for the first time in South America several stratigraphically important forms:
Glyptograptus persculptus, Climacograptus angustus, C. normalis, C. acceptus, C. rectangularis
and
Paraclimacograptus innotatus
. Also identified for the first time are
Rhaphidograptus
and
Lagarograptus.
The following are described:
Talacastograptus leanzai
gen. et sp. nov.,
Pseudoclimacograptus
(
?Metaclimacograptus
)
robustus
sp. nov. and
Lagarograptus praeacinaces
sp. nov. The closest affinity of the new biserial genus is considered to be with
Pseudoclimacograptus
. The evolutionary relationships of the three new graptolites are briefly discussed
Short Paper: Stratigraphical correlations adjacent to the Highland Boundary fault in the west of Ireland
Authors: HARPER D. A. T. , WILLIAMS D. M. , ARMSTRONG H. A.
Published: December 2007

An Ordovician age for at least part of the Clew Bay Supercomplex, a dismembered ophiolite together with contiguous deep-water sediments and volcanics occurring adjacent to the Highland Boundary fault in western Ireland, supplement comparisons with the Highland Border Complex of Scotland based on lithological similarities. An early phase of terrane development associated with ophiolite emplacement is represented in western Ireland whilst the recognition of similar intra-terrane magnafacies patterns permit a more complete analysis of the evolution of the Highland Border terrane.
Structural controls on basin evolution: Neogene to Quaternary of the Ionian zone, Western Greece
Authors: CLEWS JEAN E.
Published: December 2007

Turbidite deposition of Oligocene to Early Miocene age occurred in the foreland basin to the Pindus mountains which formed the NNW-trending Hellenide thrust front. Deposition was interrupted by the migration of the deformation front westwards through the foreland basin itself. The Kalamitsi Thrust, exposed in West Levkas, became active in late Early Miocene times. A Miocene to Pliocene piggy-back basin developed, fed both from the thrust front to the west and the mountain belt to the east. During the mid–Late Miocene, deformation remained confined to the Ionian and Gavrovo zones, possibly related to the presence of lubricating evaporites which terminate in the Pre-Apulian zone to the west. During the Late Plio-Quaternary, inner arc extension (trenchward of the Hellenic arc) caused a system of ENE and WNW basins to open under the N-S tensional regime. These were linked by NNW and NE transtensional faults and the system is still active in the Lake Trikhonis and Gulf of Corinth areas today. In the west of the study area, however, post-Pliocene NW-SE compressional faults dissected the piggy-back basin. This compressional phase must have been either contemporaneous with or interrupted the extension active in the east from Late Pliocene times.
Structural evolution of Mesozoic Peninsular Malaysia
Authors: HARBURY N. A. , JONES M. E. , AUDLEY–CHARLES M. G. , METCALFE I. , MOHAMED K. R.
Published: December 2007

Field evidence from Upper Palaeozoic and Mesozoic strata exposed in Peninsular Malaysia demonstrates that the structural style, degree and orientation of folding, axial-plane cleavage, and faulting in the Triassic, Jurassic and Cretaceous rocks of the central basin are remarkably similar. In contrast, the Upper Palaeozoic strata, especially the Carboniferous rocks exposed in the eastern part of the peninsula, show multiple phase folding and regional metamorphism unlike anything seen in the Mesozoic rocks. These observations demonstrate that two important compressional events affected Peninsular Malaysia, one in Late Permian times and the other in the mid- to late Cretaceous. The Late Palaeozoic compressional event was a major orogenic mountain building phase with associated emplacement of major Permo–Triassic granite plutons that form the eastern and main ranges. No indications were found of the widely reported Triassic orogenic compression. The palaeotectonic and palaeogeographical implications of these discoveries are important for interpreting the evolution of eastern Gondwana and Tethys.

The Raub–Bentong line was an important fault zone active during the Mesozoic but does not appear to have been a major tectonic suture since the Late Palaeozoic. We postulate that the Permo–Triassic granites of the eastern belt and those presently exposed in the main range were originally about 30–50 km apart, and that Triassic and Jurassic crustal attenuation and subsidence led to the separation of these two granitic belts by more than 100 km.
Palaeoclimates
Authors: SUMMERHAYES C. P.
Published: December 2007

Research into palaeoclimate was reviewed at the third Lyell Meeting of the Geological Society on 23 February 1989. These meetings in honour of one of the founding fathers of Geology were recently inaugurated by the Palaeontological Association and the Geological Society and the title of this meeting, Palaeoclimates, was an apt celebration of Charles Lyell's considerable interests in the subject.

Of the 13 papers and one poster presented at the meeting, eight papers have been collected for publication in this thematic set in the Journal of the Geological Society.

Charles Lyell and palaeoclimate

Ever since the days of Charles Lyell it has been appreciated that climate is one of the first order controls on stratigraphy. Lyell himself devoted no less than four chapters of the 12th edition of his
Principles of Geology
(Lyell 1875) to the subject. Given the tectonic processes that put continent where they are and create topography, climate then governs the kinds of weathering, development of soil, rates of erosion, means of transport, conditions in the environment of deposition, and much of the development of the stratigraphic record. The tectonic framework creates the space for sediments to accumulate in basins, and itself modifies the climatic regime.

Without the benefit of global knowledge and of plate tectonic theory Lyell fully realized that the continents had probably moved through time and that these motions in themselves modified climate, as the following quotations make plain.

The deviations of (isothermal) lines from the same parallel of latitude are determined by a
Sea level changes at active plate margins: processes and products
Authors: PIRRIE D.
Published: December 2007

A joint IAS/Geological Society of London meeting, organized by the British Sedimentological Research Group, was held in London at the Geological Society on 9-11 May 1989, to address the problem of recognizing the controls on, and effects of sea level change at active plate margins. The conference consisted of 48 talks and 11 poster presentations, with about 170 delegates attending.

The conference was introduced by the convenor
D. I. M. Macdonald
(BAS, Cambridge), followed by a short opening session on tectonics, eustasy and stratigraphy.
B. U. Haq
(NSF) introduced the concept of sequence stratigraphy, and the now familiar global cycle charts, arguing that systems tracts and sequences could be used for regional and inter-regional correlation.
J. F. Dewey & W. C. Pitman III
(Oxford and Lamont Doherty) considered the problem of the mechanics behind eustatic sea level changes, suggesting that changing ocean basin volume, due to fluctuations in spreading rate, may provide a way of generating the long-term cycles seen. However, such processes were gradual and could not produce the rapid short-term cycles. These short-term cycles could be attributed to changing ice-volume during periods of known glaciation; but how are they generated during non-glacial periods?

Sea level changes at Neogene and Recent margins were discussed in the second session.
M. Dobson
(Aberystwyth) suggested that the control on sedimentation at the Aleutian arc was more a function of separate block activity, rather than arc-wide tectonics or eustatic controls.
R. D. Larter & P. Barker
(BAS, Cambridge) provided evidence for post-collision uplift
Silurian graptolite biostratigraphy in the Welsh Basin
Authors: ZALASIEWICZ J. A.
Published: December 2007

Silurian graptolite zones are of markedly shorter duration than those of the Ordovician, averaging 0.8 Ma. Several can be sub-divided, and further refinement will undoubtedly follow a revision of many of the graptolite species and their stratigraphic range. Locally, integration of palaeontological and sedimentological studies facilitates correlation. A premilinary subdivision of the
crispus
and
griestoniensis
zones in central Wales is made.
The Silurian of the Pyrenees
Authors: DÉGARDIN J. M.
Published: December 2007

A detailed stratigraphical study of the Silurian rocks of the Pyrenees and analysis of their graptolite and conodont faunas has allowed the construction of composite lithostratigraphical successions and accurate correlations between them. The lithostratigraphy reflects generally continuous deposition of pelitic and shale sediments across the whole of the Pyrenean range from Rhuddanian to Homerian times. There is, however, some variation eastwards where sandier intercalations appear in the Rhuddanian. Also, carbonate facies were deposited in the Mouthoumet Massif during the latest Telychian and then from Sheinwoodian times spread across the major part of the central and eastern Pyrenees. Pelitic sedimentation persisted during the Gorstian and Ludfordian but with some differentiation into more clastic facies westwards and more carbonate-rich facies to the east. These features of sedimentation became more pronounced during Pridoli times and continued until the Early Devonian. The Silurian lithofacies of the Pyrenees are interpreted as epicontinental deposits formed in low energy, reducing environments on the northern margin of the Gondwanan continent.
The formation of coastal peat marshes under an upward tendency of relative sea-level
Authors: ALLEN J. R. L.
Published: December 2007

The upward growth of a tidal mudflat-marsh within the tidal frame is determined theoretically by the rates of minerogenic sediment supply, organogenic sediment supply, long-range sediment compaction and movement of relative sea-level. Where the movement of relative sea-level is upward, a marsh can achieve a state of dynamic equilibrium in which the composition of the sediment accumulating on its surface is governed by the balance between the rates of organogenic supply and sea-level change. A peat (organogenic) marsh should arise where the former rate roughly equals or exceeds the latter. A minerogenic marsh should form where the rate of sea-level rise is dominant, even though the absolute availability of mineral fine sediment may be so high as to appear to suggest that build-up to extreme tidal levels, where vegetation would dominate, should have occurred.
Experimental investigation of controls on cementation in carbonates
Authors: NEILSON JOYCE E.
Published: December 2007

Experiments simulating carbonate diagenesis have been performed using natural oolitic and skeletal sediments in seawater at temperatures of 183-186 °C and hydrostatic pressures of 6-10 MPa. During the experiments both equant and granular/columnar calcite cements were precipitated. Equant cements developed when both nucleation and growth rates were low due to Mg
2+
inhibition or to lower rates of CaCO
3
supply via aragonite dissolution. The data show that the Mg/Ca ratio of the pore fluid does not control calcite morphology directly during the experiments but rather the morphology is a function of nucleation and growth rate. It is also suggested that the presence of organic matter may aid nucleation of CaCO
3.
Terrane assemblage of the Leinster Massif, SE Ireland, during the Lower Palaeozoic
Authors: MAX M. D. , BARBER A. J. , MARTINEZ J.
Published: December 2007

Compilation of Irish Geological Survey mapping is used to construct a synthesis of the tectonic evolution of the Leinster Massif during the Lower Palaeozoic. The massif is interpreted as a series of NE-SW trending tectonostratigraphic terranes of diverse origin and provenance brought together along major sinistral transcurrent faults. With minor discrepancies the age of these terranes decreases from SE to NW. The Precambrian basement Rosslare terrane is succeeded by the Early Cambrian continental margin Cullenstown-Cahore terrane. In the Waterford-Wicklow terrane Late Cambrian-Early Ordovician accreted ocean floor materials are overlain by a Late Ordovician volcanic arc. The Early to Mid-Ordovician accreted ocean floor Dublin terrane to the NW is overthrust by the Early Cambrian continental margin Bray terrane and is followed to the NW by the mainly Silurian Midlands terrane. These terranes were juxtaposed after substantial sinistral movement along transcurrent faults during the Silurian. Consolidation of the massif also took place from SE to NW. Stages in the consolidation are marked by the intrusion of the Saltees (437 Ma), Carrigmore (415 Ma) and Leinster (404 Ma) stitching plutons. Fault movement ceased before the deposition of Late Devonian and Carboniferous sediments on a linking unconformity across the massif.
Palaeozoic continental margin tectonics in southern Armorica
Authors: JONES K. A.
Published: December 2007

A well-constrained clockwise
P-T
path has been established for the Southern Brittany Migmatite Belt. The prograde
P-T path
is characterized by a large
dT/dP
and is abruptly interrupted by a retrograde stage consisting of near isothermal decompression followed by near isobaric cooling. The migmatites are attributed to anatexis, which was the result of thermal relaxation in slightly overthickened crust, followed by decompression during the ascent of an anatectic granite diapir which dragged its thermal envelope, the migmatites, to shallower crustal levels. An evaluation of data from the migmatite belt and several other possibly allochthonous key elements of southern Armorican geology has been incorporated into a coherent tectonic model which accounts for the origin and subsequent involvement of micaschists, blueschists, eclogites, orthogneisses and migmatites juxtaposed by later Variscan strike-slip tectonics in the Palaeozoic evolution of southern Armorica. The tectonic model involved subduction, the creation of a volcanic arc and its associated back-are basin and their eventual destruction during continent-continent collision.