bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphatization of soft-tissue in experiments and fossils
Authors: BRIGGS D. E. G. , KEAR A. J. , MARTILL D. M. , WILBY P. R.
Published: December 2007

Soft-tissues phosphatized in laboratory experiments closely resemble fossil phosphatized soft-tissues, indicating that similar processes were involved. The smaller the aggregations of calcium phosphate particles precipitated the greater the fidelity of morphological preservation. The highest fidelity occurs where the bacteria themselves are not replicated even though precipitation is bacterially induced. While extensive phosphatization of larger carcasses, however, may necessitate the build-up of concentrations in the sediment beforehand, this is not the case for phosphatization of small quantities of soft-tissue. Mineralization of soft-tissue in the laboratory is not ‘instant’ but may take several weeks, or even months if decay is inhibited. The precipitation of associated calcium carbonate is controlled by shifts in pH in response to the decay process.
A reassessment of the early Ordovician 'Celtic' brachiopod province
Authors: COCKS L. R. M. , McKERROW W. S.
Published: December 2007

In the early Ordovician, Laurentia, Baltica and Gondwana each had endemic shallow-water cratonic faunas dominated by trilobites and brachiopods as well as some more widespread faunas around the continental margins. The latter include the Toquima-Table Head faunas around Laurentia and the 'Celtic' brachiopod faunas which form the main topic of this paper. The Celtic faunas were thought to have been distributed along and offshore of only the Gondwana side of the Iapetus Ocean. However, fresh analysis of the Celtic occurrences reveals a wider distribution of these brachiopods, ranging from a substantial volcanic island arc (the Bronson Hill-Tetagouche-Lushs Bight Island Arc) close to Laurentia to sites firmly attributable to Avalonia and possibly also Baltica. Thus, unlike most contemporary trilobite faunas, these brachiopods (which are not a homogeneous fauna) had wider latitudinal tolerance than previously supposed, and the term 'Celtic Province’ can be abandoned.
Tertiary erosion magnitudes in the East Midlands Shelf, onshore UK
Authors: HILLIS R. R.
Published: December 2007

Sonic velocities from the Upper and Middle Chalk, the Kimmeridge Clay, the Lias and the Bunter Sandstone were used to quantify apparent erosion (i.e. amount of missing section) in the Welton-1 and Cleethorpes-1 wells of the East Midlands Shelf, onshore UK. Apparent erosion was determined with reference to sonic velocities in 150 wells the UK Southern North Sea area. Apparent erosion at Cleethorpes-1 is estimated as 1.4 km (from the Kimmeridge Clay, Lias and Bunter Sandstone) and 1.6 km (from the Upper and Middle Chalk), and at Welton-1 as 1.6 km (from the Bunter Sandstone) and 1.7 km (from the Lias). The consistency of results from the different units analysed increases confidence in the results with respect to compaction studies based on a single stratigraphic unit. Estimates of missing section in this study are generally greater than those previously published for the East Midlands Shelf, but they are consistent with recent estimates from apatite fission track analysis.
The earliest possible choristodere (Diapsida) and gaps in the fossil record of semi-aquatic Reptiles
Authors: STORRS G. W. , GOWER D. J.
Published: December 2007

New fossil material of the problematic reptile species
Pachystropheus rhaeticus
from the uppermost Triassic (Rhaetian) of England, and re-examination of other specimens, demonstrate that it may be the earliest known example of the Choristodera, a poorly understood group of semi-aquatic diapsid reptiles. As a result, the fossil record of choristoderes is extended back in time by approximately 45 million years and a significant gap in the fossil record of these reptiles is highlighted. Failure of the record to reveal the evolutionary histories of those reptilian taxa that are most prone to fossilization (i.e. semi-aquatic and aquatic forms) emphasizes the need for rigorous, character-based studies in phylogenetic analysis of tetrapod lineages, rather than reliance upon stratigraphical position as an indicator of phylogenetic branching sequence. Furthermore, cladistically-based predictions of pre-Jurassic choristoderes are themselves seemingly reinforced by this discovery.
Mineral Resource Evaluation 93
Authors: WHATELEY M. K. G. , HARVEY P. K.
Published: December 2007

Report of a joint Mineral Deposit Studies Group and Geosciences Information Group meeting in association with the Institution of Mining and Metallurgy (Midlands Section), held on 6 and 7 April 1993 in the Geology Department at Leicester University. The meeting was organized by Michael K.G. Whateley and Peter K. Harvey.

After the first Mineral Resource Evaluation meeting held in Cardiff in March 1991, it became clear that there was a large, interested group of geologists, engineers and financial experts who have a common interest in mineral resource evaluation. It appeared timely to repeat the conference; this second meeting therefore was convened to discuss methods in mineral resource evaluation and describe case histories. This successful international meeting brought together all those who are involved in the day to day exploration and evaluation of mineral deposits in addition to those who are responsible for their economic evaluation and for mine feasibility and design studies. The two-day meeting included 31 papers, six posters and commercial displays by nine companies. A Special Publication of the Geological Society will be published within about a year from the date of the meeting. The meeting attracted over 100 speakers and delegates from Ireland, the Netherlands, USA, Portugal, Germany, Malawi, Canada, Ghana, Sweden, Bulgaria, Belgium, England, Scotland and even Wales.

The theme of the conference was to discuss methods of mineral deposit evaluation, and to follow this with case histories from around the world. The conference started with a keynote address by
G. Riddler
(British Geological Survey) on
Deep seismic reflection structure of the Caledonian orogenic front west of Shetland
Authors: McBRIDE J. H. , ENGLAND R. W.
Published: December 2007

Although the Moine Thrust has been well studied on land in northwestern Scotland, the subject of its deep crustal structure and regional continuation offshore remains controversial. Here, we use post-stack migration and filtering of deep seismic reflection profiles crossing the projection of the Moine Thrust and coincident Caledonian orogenic front around the western margin of the Shetland Platform in order to characterize the crustal structure of the thrust in an area not substantially affected by basin formation and extension, and where onshore geological constraints can be more readily applied. This study provides for the first time seismic reflection constraints on middle and lower crustal structure down to the level of the Moho discontinuity underlying the thrust. The seismic data reveal a thick wedge of east-dipping reflections in the lower crust capped by a highly coherent reflection which can be correlated to the postulated Moine Thrust as previously mapped on Shetland. The continuation of this wedge from the middle crust down to the Moho, against which individual reflections are abruptly truncated, suggests a ‘thick-skinned’ interpretation for the Caledonian orogen beneath the, western flank of the Shetland Platform. The available seismic data from around Shetland imply that the Moine Thrust/Caledonian front forms a boundary between an upper plate which is relatively featureless structurally and a lower plate composed of interpreted northwest-verging thrusts, possibly a crustal duplex, structurally below the level of the Moine nappe. Our observations are thus in contrast with previous interpretations made from seismic data in the West Orkney Basin north of the Northwest Highlands that describe a highly reflective Moinian upper plate.
Fault zone thickness versus displacement in the Permo-Triassic sandstones of NW England
Authors: KNOTT S. D.
Published: December 2007

Fault zone displacement and thickness data (230 measurements) plus orientation and slip vectors from 55 faults were obtained from outcrops of Permo-Triassic sandstones. The data indicate that, generally, as fault displacement increases, the width of a fault zone also increases. In detail, the relationship between displacement and thickness is stepped with thickness increasing sharply above certain values (thresholds) of displacement. This indicates a discontinuous growth of the fault zone. There are at least two thresholds in the data presented. Previous well- and seismic-based studies in the North Sea have shown a clear positive correlation between the displacement, normalized as a fraction of the reservoir thickness, and the probability of a fault sealing. Displacement, therefore, can be used to give a rough estimate of the probability of a fault acting as a pressure barrier to fluids in sandstone-dominated successions. Porosity and permeability of the reservoir rock are reduced within a fault zone, therefore the wider the zone the more likely the fault will seal hydrocarbons. Rapid jumps in fault zone thickness at displacements of roughly 300 mm and 5000 mm indicate that the relationship between fault displacement and fault seal probability may not be linear, but to a fair approximation (±15%) may be taken as such.
A continuity-based sedimentological model for temperate-zone tidal salt marshes
Authors: ALLEN J. R. L.
Published: December 2007

An exploratory model for the hydraulic and sedimentary regimes of tidal salt marshes predicts a velocity pulse as the tide enters the dry channel network, generally low channel velocities otherwise for undermarsh tides, pulses of high velocity as overmarsh tides at first flood onto and finally ebb off the marsh platform, generally sluggish flows otherwise over the marsh platform, and the retardation of the flow over the platform with increasing distance from channels and the marsh front. The model points qualitatively to a long-term depositional regime on marsh platforms, characterized by a decline away from channels and the marsh front in the accretion rate and grain size of sediment advected by overmarsh tides. The sedimentary regime in the channel network is more complex but, over periods of years, a state of quasi-equilibrium is plausible. Under these circumstances, the model hints that the external factors of tidal range and the texture and mineralogy of available sediment may determine the character of the branching channel network.
The Peterborough Member (Callovian, Middle Jurassic) of the Oxford Clay Formation at Peterborough, UK
Authors: HUDSON J. D. , MARTILL D. M.
Published: December 2007

King’s Dyke brick pit, Whittlesey, near Peterborough, Cambridgeshire, provides a continuous section through the Peterborough Member (formerly known as the Lower Oxford Clay) of the Oxford Clay Formation, and is here described as its type section. It also shows parts of the underlying Kellaways Formation and of the overlying Stewartby Member of the Oxford Clay Formation. Other sections in the Peterborough district are discussed and related to the type section. The Peterborough Member is developed throughout southern England and aspects of its stratigraphy, palaeogeography and burial history are briefly reviewed.
Mineralogy and geochemistry of the Peterborough Member, Oxford Clay Formation, Jurassic, UK: element fractionation during mudrock sedimentation
Authors: NORRY M. J. , DUNHAM A. C. , HUDSON J. D.
Published: December 2007

X-ray diffraction, electron microprobe and SEM analyses show that the Peterborough Member of the Oxford Clay Formation is composed mainly of quartz and illite, with lesser amounts of chlorite, kaolinite, K-feldspar, plagioclase, very small amounts of anatase and apatite, and variable amounts of calcite and subordinate siderite. The geochemistry, including major and a range of trace elements are used, with the mineralogy, to demonstrate the existence of several distinct components which have contributed to variations within the Peterborough Member. These components are (1) quartz, zircon and possibly other heavy minerals and K-feldspars, (2) carbonates, (3) phosphatic material, (4) organic material and (5) clays. Geochemical comparisons are made with various average shales demonstrating abnormally low Ba, Cu, CO, Mn, Na and Mg in the Peterborough Member. It is suggested that the current mineral assemblage is mostly detrital material, with little diagenetic alteration. The demonstration of fractionation between hydrodynamically heavy and light grains, even in an apparently fine grained sediment such as the Oxford Clay, has disturbing consequences for geochemical studies of sediment source areas where small numbers of small samples are employed.
Reappraisal of Middle Pleistocene fluvial deposits near Brandon, Warwickshire and their significance for the Wolston glacial sequence
Authors: MADDY D. , COOPE G. R. , GIBBARD P. L. , GREEN C. P. , Group S.G. LEWIS
Published: December 2007

Recent exposures at Pools Farm Pit, Brandon have allowed a reinvestigation of strat-igraphic relationships critical to the debate concerning the status of the Wolstonian Stage of the British Pleistocene. Central to the original case for maintaining the type site of the Wolstonian Stage at Wolston, Warwickshire is the acceptance that the fluviatile Baginton Formation (Shotton’s Baginton-Lillington Gravel and Baginton Sand) forms, together with the glacigenic Wolston Formation, a series of sediments (Shotton’s Wolston Series) deposited during a single post-Hoxnian (i.e. post-oxygen isotope stage 9) glacial stage. Evidence presented in this paper suggests this interpretation is no longer tenable.

The sediments of the Baginton Formation exposed at Pools Farm Pit record the facies changes identified by Shotton in 1968. A predominantly gravel unit, the Brandon Gravels (Baginton Gravel Member), is overlain by a sandy unit, the Brandon Sands (Baginton Sand Member), the bounding surface being erosional. Two newly exposed fine-grained organic channel fills are described. The Brandon Lower Organic Sands and Silts lie within the Brandon Gravels and contain a temperate coleopteran fauna and a boreal forest flora. Correlation of these organic deposits on fauna1 grounds with the nearby site of Waverley Wood suggests a correlation with oxygen isotope stage 15. The Upper Organic Silts and Clays lie within the Brandon Sands and contain a cold climate fauna and flora. The Brandon Sands are overlain locally by the Brandon Upper Sands and Gravels which are correlated with the Ailstone Member of the Avon Valley Formation (stage 6). The younger Avon Valley Formation is known to extend back to at least stage 9 and therefore given that the Wolston Formation is younger than the Baginton Formation as indicated by a borehole nearby, it could represent any of the cold stages 10, 12 or 14. However, stage 12, the Anglian, remains the most likely attribution.
A record of late Cenozoic stratigraphy, sedimentation and climate change from the Hebrides Slope, NE Atlantic Ocean
Authors: STOKER M. S. , LESLIE A. B. , SCOTT W. D. , BRIDEN J. C. , HINE N. M. , HARLAND R. , WILKINSON I. P. , EVANS D. , ARDUS D. A.
Published: December 2007

A punctuated 103.3 m thick succession of upper Palaeogene to Quaternary sediments has been recovered in a borehole from the upper Hebrides Slope, west of Britain. The borehole proved 11.2m of upper Oligocene, carbonate-rich muds at the base, unconformably overlain by 2.85 m of middle to upper Miocene, glauconitic sands. This is in turn unconformably overlain by 89.25 m of predominantly Plio-Pleistocene sands and muds, with a Holocene sea-bed veneer. The post-Miocene succession is subdivided into two units: the sand-dominated, Pliocene to lower middle Pleistocene, Lower MacLeod sequence between 89.25 and 67.82 m, and the mud-dominated, middle Pleistocene to Holocene, Upper MacLeod sequence above 67.82 m. Regional mapping indicates that these sequences are commonly associated with large-scale shelf-margin progradation and slope-front fan construction.

The borehole core provides an excellent record of the transition from pre-glacial to glacial conditions in the mid-latitude NE Atlantic Ocean. Climatic conditions warmer than present prevailed in the late Oligocene, mid- to late Miocene and Pliocene, although the influx of ice-rafted detritus in the late Pliocene marks the onset of climatic deterioration. This deterioration continued, in a fluctuating manner, until the early mid-Pleistocene (0.44 Ma) when fully glacial conditions were established on the Hebridean Margin.
Stratigraphic and structural evolution of the Tertiary Cosmelli Basin and its relationship to the Chile triple junction
Authors: FLINT S. S. , PRIOR D. J. , AGAR S. M. , TURNER P.
Published: December 2007

At the Taitao Peninsula, in southern Chile (46.5
°
S), an active mid-ocean ridge is being subducted under the South American continent. Continental crust south of the current triple junction has experienced subduction of three ridge segments since the mid-Miocene. A series of Mid-Late Tertiary sedimentary basins lies inboard of the triple junction: the Cosmelli basin lies in the region which has experienced the earlier ridge subduction events. Within the Cosmelli basin fill, abrupt facies dislocations give clear evidence of marked base level changes. Four sequence boundaries are delineated, with an upward increase in degree of facies dislocation, which is believed to reflect increasing magnitudes of base level fall. The lower part of the basin fill is folded and then thrust eastward as a series of imbricate slices, while the overlying, greater thickness of fluvial sediments is only gently tilted westwards. This geometry indicates that the early basin fill was deforming due to contractional tectonics while the later basin fill was being deposited; these processes controlled accommodation space and thus stratigraphic architecture during much of the basin life. This complex basin history, plus the presence of basaltic sheet intrusions may reflect the underlying slab history as successive ridge segments were subducted.
Oroclinal bending in the Caledonides of western Ireland
Authors: SMETHURST M. A. , MACNIOCAILL C. , RYAN P. D.
Published: December 2007

New palaeomagnetic data from the Caledonides of western Ireland indicate that the Silurian rocks of South Mayo underwent oroclinal bending, following folding, in Siluro-Devonian time. Bending was accommodated on faults cutting the Silurian sequence, and was driven by strike slip motion across the Antrim-Galway Line, a recently recognized major curvilinear lineament. We propose that the Silurian rocks in the east of the region suffered up to 30° clockwise rotation, increasing towards the west to approximately 70°. This newly inferred differential rotation of the Silurian rocks, about a sub-vertical axis, implies that the underlying Dalradian rocks of the Connemara Massif to the south must also have undergone clockwise rotation in late Silurian/early Devonian time. This is consistent with published palaeomagnetic data from the Connemara Gabbro and accounts for the swing in strike of the Caledonian orogen in this part of western Ireland. From this we deduce that the swing in strike of the Caledonian rocks elsewhere on the west coast of Ireland might have a similar explanation.
Trace metal solid state speciation changes associated with the down-column fluxes of oceanic particulates
Authors: CHESTER R. , LIN F. J. , BASAHAM A. S.
Published: December 2007

The ‘global carbon flux’, which is dominated by large-sized organic aggregates, removes dissolved trace metals from sea water and delivers suspended particulate material to the sediment surface. Dissolved trace metals sequestered by the sinking particulates can have different speciation signatures; for example, Cu is removed principally via an organic association, whereas Mn is mainly scavenged via an inorganic surface association involving small particles which are ‘dragged down’ by the aggregates. The trace metal speciation signatures in suspended particulate material appear to be similar on a global ocean basis, but once the particulates reach the sediment surface they are subjected to a variety of processes which are constrained by the depositional environment, especially the redox conditions. In some marginal hemi-pelagic deposits the original suspended particulate trace metal speciation signatures can be retained in the buried sediment, but in open-ocean pelagic sediments deposited under oxidizing conditions the particulates suffer severe modification as the organic carbon in the sinking aggregates is destroyed during oxic diagenesis. The solid state speciation signatures of trace metals reflect these modifications, and so can be used as ‘tracers’ to monitor the chemical changes affecting particulate material incorporated into deep-sea sediments via the ‘global carbon flux’. This is illustrated with respect to the speciation signatures of Fe, Cu and Mn in surface sea water particulates and deep-sea sediments from the Atlantic Ocean.
Element supply to surface manganese nodules along the Aitutaki-Jarvis Transect, South Pacific
Authors: CRONAN D. S. , HODKINSON R. A.
Published: December 2007

Supply of metals to manganese nodules in the south equatorial Pacific is heavily dependent on variations in biological productivity. In the northern part of the Aitutaki-Jarvis transect, under high biological productivity in the surface waters, there is a high flux of Mn, Ni, Cu and Zn to the nodules diagenetically cycled through the interstitial waters of the uppermost sediments, together, in the nodules, with the formation of 10Å manganite. To the south of the high productivity zone, these elements decrease in the nodules at the expense of Fe, CO and Pb of hydrogenetic provenance and δMnO
2
is more abundant. However, nodule compositions also reflect the position of the deposits relative to the carbonate compensation depth (CCD), which deepens northwards throughout the region, with Mn, Ni, Cu and Zn being enriched in 10Å manganite bearing nodules from near the CCD under high productivity waters and Fe, Co and Pb being more abundant in X-ray amorphous or δMnO
2
-bearing nodules away from the CCD and/or in the south of the transect under low productivity waters.
Element supply to surface sediments and interrelationships with nodules along the Aitutaki-Jarvis Transect, South Pacific
Authors: MILLER S. , CRONAN D. S.
Published: December 2007

A suite of surface sediment samples has been studied from sites on the Aitutaki-Jarvis Transect, between the equator and 17°S at approximately 160°W in the Central Pacific Ocean. The sediments were analysed by bulk and partition analysis in order to characterize changes in sediment geochemistry with water depth and with latitude, with particular reference to the effects of variation in supply and dissolution of biogenic material. The surface sediments are heterogeneous, ranging from carbonate or siliceous oozes to pelagic red clays. The elements in the sediments are variably partitioned into different sediment fractions. Examination of the sediments along the Transect has also provided a profile of the carbonate compensation depth, which shows it to deepen from approximately 4800 m at 16°S to approximately 5300 m at the equator.

The relationships between the bulk sediments and the sediment reducible fraction and associated Mn-Fe nodules has been examined. Variations in the interrelationships between the nodules and the sediment reducible fraction are ascribed to variations in element supply and early diagenetic reactions. A major decoupling of the relationship between nodules and associated sediment reducible fraction is observed in the north of the Transect at water depths close to the position of the CCD. Diagenetic reactions involving the destruction of organic matter which result in the reductive remobilization of Mn and the release of trace metals from labile material are thought to be important causes of this decoupling.
Two Archaean granulite-facies metamorphic events in the Nuuk-Maniitsoq region, southern West Greenland: correlation with the Saglek block, Labrador
Authors: FRIEND C. R. L. , NUTMAN A. P.
Published: December 2007

Two dilferent granulite-facies events have been identified using SHRIMP U-Pb zircon geochronology in the Nuuk-Maniitsoq tract of West Greenland, previously considered to comprise a continuous, contemporaneous granulite facies terrain. About 35 km north of Nuuk, a granulite-facies metasedment contains metamorphic zircon overgrowths recording a
207
Pb/
206
Pb age of 2999 ± 4 Ma (2σ). Some l30 km further north, near Maniitsoq, an orthopyroxene-bearing granite contains metamorphic zircons recording an age of 2738 ±6 Ma. Previous correlations have liked the early Archaean rocks of the Saglek block of northern Labrador with those in the Nuuk region. However, this causes problems with correlation of crustal blocks on either side of the Labrador Sea. The proposal here, of correlating late Archaean metamorphic events at 2740 Ma, provides a better solution to the problem.
Palaeostress analysis and geodynamical implications of Cretaceous-Tertiary faulting in Kent and the Boulonnais
Authors: BERGERAT F. , VANDYCKE S.
Published: December 2007

Detailed studies of fracture patterns and palaeostress reconstruction based on fault slip data analysis allow identification of five main palaeostress fields in the Cretaceous formations of the Boulonnais and Kent areas. These stress patterns correspond to six successive tectonic events: (1) a N–S compression/E–W extension of early Cenomanian age, (2) an E-W extension of late Cenoma-nian age, and (3) four post-Santonian events with N–S, E–W, NW–SE and NE–SW extensions, respectively. The first event, interpreted from conjugate strike-slip faults is related to the beginning of the Sub-Hercynian phase and linked to a right-lateral motion of the Nord-Artois Shear Zone. The first E-W extensional event and the N-S extensional event could be related to the last rifting episodes of the North Sea graben and English Channel (Wessex basin). The others post-Santonian extensional events are related to Late Cretaceous, Tertiary and Recent tectonic episodes.
Fission-track analysis and provenance studies in Calabrian Are sedimentary rocks, southern Italy
Authors: THOMSON S. N.
Published: December 2007

Fission track analysis has been applied to the Stilo–Capo d'Orlando Formation of southern Italy. This is a terrigenous syn-orogenic sedimentary deposit of Oligo-Miocene age that accumulated during a phase of accelerated denudation that affected the nearby crystalline basement rocks of the Calabrian Arc between
c.
30 and 15 Ma.

Seven conglomerate clasts and two sandstone samples from the base of the formation have produced eight apatite fission-track ages, nine zircon fission-track ages and six apatite confined-track length analyses. The zircon fission-track data confirm that detritus was derived from local Hercynian igneous and metamorphic rocks. In addition, apatite fission-track results from the two sandstone samples reveal that the basal part of the Stilo–Capo d'Orlando Formation was exposed to maximum palaeotemperatures in excess of 70°C after deposition. Despite this, apatite fission track ages much older than those obtained from the in situ crystalline basement source rocks of the Calabrian Are have been acquired. These ages are interpreted as being derived from ‘lost cover’, that is, rocks originating from the structurally highest levels of the basement complex that have now been completely removed by erosion. Fission track analysis demonstrates that erosion, in addition to previously identified extensional tectonism, was a major factor during accelerated denudation of the Calabrian Are basement rocks during the late Oligocene and early Miocene.
Fission-track dating of granitic rocks from the Eastern Cordillera of Peru: evidence for Late Jurassic and Cenozoic cooling
Authors: LAUBACHER G. , NAESER C. W.
Published: December 2007

Apatite and zircon fission-track ages of three samples of the Huachon granite and one sample of the Quiparacra granite, from the Eastern Cordillera of the Andes of central Peru, have been determined. Zircons from the Huachon granite yielded two groups of ages. An older group, made up of zircons with the lowest uranium content, gave an age of
c
. 270 Ma. The zircons with high uranium content from this granite gave ages of
c
. 160 Ma. The zircon ages from the Huachon granite show no correlation with elevation. The age of 270 Ma is interpreted as the age of probable emplacement; the 160 Ma age is evidence of a mild cooling (≥200°C) event that ended in late Mid-Jurassic time. This cooling correlates, in central Peru, with thick conglomerates in the Sub-Andes and strong exhumation in the Eastern Cordillera during Bathonian to Malm times.

Zircons from the Quiparaca granite, which is a component of a composite batholith of possible Precambrian to Tertiary age, show ages of
c.
30 Ma which are interpreted as the emplacement age. These zircons were totally annealed prior to the cooling in the Oligocene. This required temperatures, >200°C.

Apatite fission-track dating of the Huachon granite yielded only Neogene ages which reflect the total annealing of the tracks present in the apatite before exhumation began
c.
22 Ma. Apatite ages show a correlation with elevation and indicate two periods of cooling during the Neogene at c. 21 Ma and between 12 Ma and the Present. These young ages suggest approximately 4 to 6 km of erosion in the Eastern Cordillera of central Peru in the past 30 Ma. These amounts are consistent with known geological data and fission-track ages obtained from other parts of the eastern Andes.
Late Proterozoic magmatism in the Nakasib suture, Red Sea Hills, Sudan
Authors: SCHANDELMEIER H. , ABDEL RAHMAN E.M. , WIPFLER E. , KÜSTER D. , UTKE A. , MATHEIS G.
Published: December 2007

The south-western part of the NE-SW-trending Nakasib suture in the Red Sea Hills of Sudan is characterized by a distinct lithostratigraphic and geochemical zonation from north to south. The southern part of the suture zone is underlain by the Ariab volcanic arc which is separated from the adjacent Oshib ophiolitic melange to the north by a major NW-verging thrust. Basalts of the Oshib ophiolite complex vary from north to south from typical mid-ocean-ridge (MORB) through oceanic island (OIB) to boninitic lavas. The volcanic sequences of the Ariab island are consist of minor tholeiitic and major calc-alkaline intermediate to felsic volcanic and plutonic rocks. Approximately 810 Ma old, subduction-related calc-alkaline granitoid rocks have been intruded into the northern margin of the 890–840 Ma old Haya terrane along the southern boundary of the Nakasib suture zone. This lithostratigraphic arrangement and the geochemical zonation of the ophiolites indicate that the Nakasib ocean basin was consumed in the Late Proterozoic by a southerly dipping subduction zone.
Sedimentation and volcanism in an Oligocene-Miocene intra-oceanic are and fore-are, southwestern Viti Levu, Fiji
Authors: HATHWAY B.
Published: December 2007

Rocks belonging to the Lower Oligocene to Middle Miocene Wainimala Group in southwestern Viti Levu can be divided into an are assemblage, representing the axial part of a volcanic are, and a basinal assemblage, representing the trenchward flank of the are and the inner part of the fore-are basin. The are assemblage consists mainly of volcaniclastic rudites and lava flows, with minor shallow-water limestones, and is intruded by Mid- to Late Miocene gabbro and tonalite stocks. The basinal assemblage to the north is floored by part of an earlier, Eocene to Lower Oligocene are. The lower part of this assemblage includes volcaniclastic rudites representing the dispersal aprons of major volcanic edifices to the trenchward of the are axis, and basaltic lavas and fissure-fed rhyolite lava domes and breceia ridges erupted in deeper water away from these centres. The rhyolites are directly related to the acidic members of a dense, compositionally bimodal dyke swarm that intrudes the underlying earlier are rocks, recording substantial crustal extension. The basinal volcanic rocks are interbedded with and overlain by a sequence of pelagic carbonates, thin-bedded epiclastic turbidites, and acidic tuffs. The basinal succession evolved from an intra-are to an inner fore-are setting as volcanism within the assemblage died away in the Early Miocene. In the late Early Miocene increased uplift and emergence of the are massif increased the sediment yield to the fore-are basin, resulting in the deposition of thicker-bedded, coarser-grained turbidites.
Channelled fluid infiltration and variation in permeability in Reynolds Range marbles, Australia
Authors: CARTWRIGHT I. , BUICK I. S.
Published: December 2007

Strike-parallel flow of H
2
O-rich fluids through Reynolds Range marbles formed wollastonite-bearing assemblages. Wollastonite abundance varies on a millimetre de from 10 to 66 modal%. The mineralogy of unmetasomatized marbles suggests that the formation of more than
c
. 19% wollastonite requires silica metasomatism. Comparison with advective transport models suggests that the variable wollastonite contents may be explained by time-integrated fluid fluxes and intrinsic permeability varying by up to two orders of magnitude on a millimetre scale. Fluids were probably focused through the marble within microfractures and the variations in intrinsic permeability may reflect variable fracture density.
Timing and significance of crosscourse mineralization in SW England
Authors: SCRIVENER R. C. , DARBYSHIRE D. P. F. , SHEPHERD T. J.
Published: December 2007

Rb-Sr isotope analyses of inclusion fluids from quartz have demonstrated a Triassic age (236 ± 3 Ma) for N–S-trendmg Pb–Zn–F vein mineralization in the Tamar Valley district of the Cornubian orefield. Consideration of the stratigaphy and structure of the Permo-Triassic basins both onshore and in the English Channel suggest that this mineralization results from the formation of fractures during regional extension-driven subsidence, and the subsequent ingress of basinal brines to the Variscan basement.
Excavations at the Lower Palaeolithic site at East Farm, Barnham, Suffolk 1989–92
Authors: ASHTON N.M. , BOWEN D.Q. , HOLMAN J.A. , HUNT C.O. , IRVING B.G. , KEMP R.A. , LEWIS S.G. , McNABB J. , PARFITT S. , SEDDON M.B.
Published: December 2007

Preliminary results are presented from three seasons' work at the Lower Palaeolithic site at Barnham. The complex stratigraphy is described and a provisional interpretation given, which suggests that the archaeological deposits date to a warm phase after the Anglian (Middle Pleistocene) cold stage. A fauna1 assemblage from the deposits is described, providing an environmental and biostratigraphic context for the site. Further geochronological control is provided by amino acid ratios on shells from the sequence. Two flint assemblages have been excavated, the first consisting of flakes and cores, and the second including bifaces. These assemblages and their position in the British sequence are considered in terms of their stratigraphic context and their relationship to other Lower Palaeolithic assemblages in the British Isles.
Compressional deformation at the ocean–continent transition in the NE Atlantic
Authors: MASSON D. G. , CARTWRIGHT J. A. , PINHEIRO L. M. , WHITMARSH R. B. , BESLIER M.-O. , ROESER H.
Published: December 2007

Local zones of compressional deformation, spatially coincident with the ocean-continent transition. occur in the NE Atlantic off western Iberia, on the northern margin of the Bay of Biscay and in the southern Rockall Trough. The deformation zones are typically broad oceanward-facing monoclines several tens of kilometres in width. The amount of shortening is small, although the structures may also accommodate some strike-slip motion. Deformation peaked during the Mid-Late Eocene in Biscay. off Galicia Bank and in Rockall Trough, and in the mid-Miocene off western Iberia. These deformation pulses were contemporary with the Pyrenean and Betic Orogenies in western Europe and may have resulted from structural reorganizations within the evolving orogens driven by changes in plate motion. Possible mechanisms which might concentrate deformation at the ocean-continent transition include slip within serpentinized peridotite underlying the transitional region and reactivation of a pre-existing detachment fault within the thinned continental crust. Our observations may imply that rifted continental margins, when reactivated, can develop into new sites of plate subduction.
40
Ar/
39
Ar mineral age record in NE Greenland: implications for tectonic evolution of the North Atlantic Caledonides
Authors: DALLMEYER R. D. , STRACHAN R. A. , HENRIKSEN N.
Published: December 2007

40
Ar/
39
Ar mineral ages have been determined from basement gneisses and cover sequences exposed in the Caledonides of NE Greenland. These range between
c
. 438 Ma and
c
. 370 Ma (early Silurian-mid-Devonian).They are interpreted as dating cooling following polyphase Caledonian metamorphism which completely reset argon systems within the (early Proterozoic) basement gneisses. The
40
Ar/
39
Ar results indicate that thrust-related regional deformation and metamorphism in NE Greenland continued into the early Devonian. This contrasts with Scandinavia, where nappe stacking was largely completed by the early–mid-Silurian and was followed by regional extension and tectonic unroofing in the late Silurian–mid-Devonian. Tectonic models developed for the late-orogenic evolution of the northern Atlantic Caledonides therefore need to incorporate considerable along- and across-strike variation in both the style and timing of major tectonothermal events.
Wave-dominated nearshore sedimentation and ‘forced’ regression: post-abandonment facies, Great Limestone Cyclothem, Stainmore, UK
Authors: AINSWORTH R. B. , CROWLEY S. F.
Published: December 2007

Investigation of sedimentary successions and depositional structures from the post-abandonment phase of the Great Limestone Cyclothem (Upper Carboniferous), Stainmore, UK suggests that deposition occurred in a sand-dominated coastal setting. Recognition of sedimentary structures produced by storms and interpretation of palaeocurrent and palaeowave data indicate that a W—E oriented, southwardly prograding, high-energy shoreline system existed in the Stainmore region. Two equally plausible interpretations suggest that the trough cross-stratified facies lying towards the top of the shoreface succession may either represent: (1) upper shoreface deposits formed by high energy fairweather waves, or (2) the deposits of a tidally influenced deltaic distributary or incised valley fill estuarine system. These interpretations contrast significantly with the N-S oriented, transgressive barrier island model proposed in an earlier study.

The sharp contact between lower shoreface and underlying offshore facies suggests that progradation of the shoreline occurred during a relative sea-level fall (‘forced’ regression). Palaeocurrent evidence indicates that deposition occurred within a system in which sediment was periodically flushed from a contemporary delta lobe and subsequently transported to the Stainmore shoreline by longshore currents.
Early calc-alkaline magmatism in the Mogollon-Data Volcanic Field, New Mexico, USA
Authors: DAVIS J. , HAWKESWORTH C. J.
Published: December 2007

The Mogollon-Datil Volcanic Field in southwest New Mexico was active between 40 and 20 Ma. It is situated
c.
500 km from the western North American plate margin, and yet the early pre-30 Ma volcanic rocks comprise a high-K calc-alkaline suite ranging from basaltic andesites to dacites. All the samples are characterized by high and variable LILE and LREE contents, and LILE/HFSE ratios, and variable Nd and Sr isotope ratios of 0.51231–0.51250 and 0.7055–0.7065 respectively. In detail, three groups are recognized: Group 1 rocks have the lower SiO
2
, incompatible element abundances and
87
Sr/
86
Sr ratios; Group 2 preserves the clearest evidence for open system differentiation, and Group 3 exhibits little variation in
87
Sr/
86
Sr and the most coherent major and trace element arrays. The Group 2 rocks have been modelled in terms of simple binary mixing between selected Group 1 basaltic andesites and a higher silica crustal endmember, which appears to have been derived from the mid-lower crust in the presence of residual garnet. The Group 3 rocks, by contrast, are consistent with near closed system differentiation, modelled in three stages and involving Plag-Aug-O1-Mag and subsequently hornblende and K-feldspar. Published experimental data indicate that the differentiation of the parental basaltic magmas took place at elevated pressures of
c
. 4-5 kbar, and water contents,
c
. 2wt% H
2
O. It is argued that the parental magmas to these calc-alkaline suites were generated in a period of lithospheric extension, and that they were derived from within the continental mantle lithosphere, as inferred for mid- to Late Tertiary rocks elsewhere in the western US, with no significant contribution from contemporaneous subduction processes.
Late Cenozoic rates of magmatic activity in the Central Andes and their relationships to continental crust formation and thickening
Authors: FRANCIS P. W. , HAWKESWORTH C. J.
Published: December 2007

Data from four sources are used to assess the rate of magmatic addition to the central Andean crust : (i) a closely studied segment of the are between latitudes 21° and 22°S; (ii) all the potentially active volcanoes within the Central Volcanic Zone; (iii) all the volcanic additions in the last 1 Ma; and (iv) those within the last 10 Ma. These indicate a consistent rate of effusive volcanism of 3 X 10
−6
km
3
a
−1
km
−1
. Rates of silicic pyroclastic volcanism, the ratios of extrusive to intrusive rocks, and the fraction of material newly derived from the mantle are more difficult to constrain, but conservative estimates indicate that the overall rate of magmatic addition to the crust is of the order of 1.3 × 10
−5
km
3
a
−1
km
−1
. This rate is inadequate to account for the crustal thickening since 15 Ma ago, but is consistent with estimates from, for example, the Aleutian are (3.4 × 10
−5
km
3
a
−1
km
−1
). These data support Isacks' contention that the thick crustal root beneath the Central Andes results from tectonic shortening and thickening, rather than magmatism.

There is little evidence of sediment subduction at the Chile-Peru trench at the present day, but tectonic erosion at a rate of about 1 × 10
−6
km
3
a
−1
km
−1
may have continued since the Jurassic. Their net effects are difficult to determine, primarily because of uncertainties about petrological processes in the lower crust. The extensive ignimbrite province of the Sierra Madre Occidental of Mexico has some similarities with the Central Andes, but eruption rates are 20 times larger (3.7 × 10
−5
km
3
a
−1
km
−1
). ɛ
Nd
values for the Sierra Madre dacites are high (+0.2–+0.48) suggesting that they evolved by crystal fractionation from mantle-derived basaltic parent magmas, and are consistent with rapid formation of continental crust. In the Central Volcanic Zone, however, higher Rb/Sr ratios in similar dacites suggest large scale melting of middle to lower continental crust, perhaps in association with lithospheric thinning. If lithospheric thinning is an important cause of melting, it will reduce estimates of net magmatic additions to the crust.
A hydrogeological model for the early diagenesis of Late Triassic alluvial sediments
Authors: WRIGHT V. P. , SANDLER A.
Published: December 2007

The late Triassic Mercia Mudstone Group of southwest Britain, a problematic, complex arid playa-floodplain-aeolian deposit, contains a variety of Mg clays and carbonates. Recent interpretations have invoked marine waters as a source of Mg in clays. However, both the Mg-rich clays and other early diagenetic features seen in the late Triassic in Europe are directly analogous to those found in the inland drainage basins of Australia. A simple hydrogeological model is offered based on these basins where shallow
groundwater
evolution takes place within the basin producing a range of early diagenetic products including groundwater dolocretes and Mg clays. Such a model, as developed in Australia, is probably widely applicable to ancient arid alluvial systems.

The Mercia Mudstone Group is a problematic sequence of predominantly red siltstones and mudstones with minor sand, dolomite and limestone intercalations (
Ruffell 1991
). It has been extensively studied in outcrops in southwest and southern Britain, particularly in the Bristol Channel area. The siltstones and mudstones, of late Triassic age, are the distal equivalents to alluvial fan deposits and are associated, at least locally, with lake margin and spring travertine deposits (

Leslie
et al.
1992

).

Some workers have favoured a marine-influenced setting for the deposition of the mudrocks or playa lakes (see review in
Taylor 1983
). Most recently they have been interpreted as the deposits of complex floodplain-playa systems with a signficant aeolian input (

Talbot
et al.
1994

).

Extensive evaporites occur locally in the unit, including thick halite deposits and have been interpreted as evidence of marine
Neoproterozoic sinistral displacement along the Darling Mobile Belt, Western Australia, during Gondwanaland assembly
Authors: HARRIS L. B.
Published: December 2007

Evidence is provided for Neoproterozoic sinistral displacement along the Darling Mobile Belt between Greater India and Precambrian terranes of Western Australia. A dilatational bend in the shear zone is thought to have controlled emplacement of alkali granites, anorthosite and mafic intrusives of the Leeuwin Complex which was deformed during progressive deformation. Faults formed in this event extend across the Albany Mobile Belt, and control the formation of the Stirling Basin on the southern margin of the Yilgarn Craton. The regional extent of this event and the rotation of Mesoproterozoic trends in the Albany Mobile Belt through 90° suggests that the Darling Mobile Belt may be part of a shear system of regional importance during assembly of proto-East Gondwanaland.

Much attention is being focused on the assembly of Gondwanaland and the relative displacements between Archaean cratons along Proterozoic mobile belts (e.g.
Powell 1993
;
Unrug 1994
;
Yoshida 1994
). Southwestern Australia is a key area within proto-East Gondwanaland as, in reconstructions such as de Witt
et al.
1988 and Powell
et al.
1988, it constitutes the junction between the Archaean Yilgarn Craton of Western Australia, India/Greater India, and the East Antarctic Shield (Fig. 1). This paper examines the timing and nature of displacements along the Darling Mobile Belt (Glikson & Lambert 1973; Mathur & Shaw 1982) on the western margin of the Yilgarn Craton and contemporaneous structures within the Albany Mobile Belt and southern Yilgarn Craton (Fig. 2).

The Darling Mobile Belt.
The Darling Mobile Belt, referred to by
Myers (1990)
as the