fluorescing macerals in south african coals abstract maceral microlithotype and fluorescing maceral content were analysed along with the vitrinite relative fluorescence measurements thirty samples from the south africa soutpansberg waterberg and main karoo basins were investigated these results were also compared with previously measured vitrinite reflectance values the application of fluorescence techniques has allowed the identification of much higher liptinite content about 5 as compared with the results of routine maceral analysis in white light results presented provide an explanation of this difference which is caused by difficulties in identifying fine liptodetrinite particles under illumination by the halogen lamp therefore detritic particles of uncertain affinity should be verified under fluorescing light during routine maceral analysis the presence and intensity of the fluorescing vitrinite in south african coals were also studied the occurrence of this component is connected with the rank of coal but could be also affected by the facies sample no b 35 and in situ coal oxidation sample no b 3 the relative fluorescence intensity of vitrinite depends on the rank of the coal but also on its degree of oxidation it seems also to be connected with the expulsion of oil which enhances its intensity the influence of the fluorescing macerals content on some coal properties was proved by the positive correlation between fluorescing vitrinite as well as sum of fluorescing macerals and calorific value 0 66 and 0 74 corr coeff respectively this proves the necessity of fluorescence application in routine maceral analysis carried out for coal quality evaluation

a crustal seismic velocity model for the uk ireland and surrounding seas summary a regional model of the 3 d variation in seismic p wave velocity structure in the crust of nw europe has been compiled from wide angle reflection refraction profiles along each 2 d profile a velocity depth function has been digitised at 5 km intervals these 1 d velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values an analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate horizontal dimensions of the model cells are optimised at 40 40 km and the vertical dimension at 1 km the resulting model provides a higher resolution image of the 3 d variation in seismic velocity structure of the uk ireland and surrounding areas than existing models the construction of the model through kriging allows the uncertainty in the velocity structure to be assessed this uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure and shows that for this region the velocity is poorly constrained for large areas away from the input data

macro and micro factors affecting coal seam quality and distribution in southern africa with particular reference to the no 2 seam witbank coalfield south africa abstract petrographical and palynological coal quality investigations relating to variations in one of the best known and well researched coalfields in africa the witbank coalfield and one of the most commercially important seams within this coalfield the no 2 seam are highlighted in this paper the investigations were based on 14 channel samples covering a 40 20 km 2 area in the witbank coalfield the results indicate that the coals in the no 2 seam were formed at the stage of major change over from dwyka to ecca floras as illustrated by the progressive dying out of dwyka pollens and spores and the introduction of ecca floral elements this also suggests a rapid amelioration of climate over the period of peat accumulation following a period of continental glaciation furthermore it is proposed that the in seam horizons reflect fluctuating of cyclic environments probably due to changing water level and plant communities due to changing growth environments saccate pollens appear to occur in association with vitrinite rich microlithotypes trilete spores with inertodetrite and carbominerite rich microlithotypes and plicates with inertite semifusite inertodetrite microlithotypes acritarchs nonspinose are present in parts of the seam where inertodetrite is common and in association with unusual suites of trace and major elements possibly indicating changing geochemical environments in high groundwater conditions petrographic results indicate that the coals are medium rank hypobituminous and show wide variations in maceral mineral and microlithotype compositions both vertically and laterally on the basis of microlithotype and mineral group analyses investigations were undertaken to establish vertical subdivisions by the study of historical patterns and possible lateral correlations of these subdivisions in the area under investigation these methods were then compared with distribution of selected chemical and geochemical parameters the evidence suggests that a common sequence of major events and some minor events occurred during the accumulation of the no 2 seam as manifested by petrographic and palynological facies three major periods or zones are recognized these tepresent periods of relatively stability quiescence separated by major in seam disruptive events namely flood deposits bearing high proportions of detrital organic material or minor clastic sedimentation these zones are subdivided into several subzones representing periods of reworking local flooding or rise in ground water levels and or changing geochemical environments these events can be recognized throughout the area under investigation but the manifestation of these events varies from area to area depending upon topographic situation proximity to river channels valley flanks or palaeoshorelines degree of subsidence and compaction geochemical environment and length of time under a specific set of conditions thus channels in close proximity to one another or in similar positions relative to valley flanks or axes appear to be remarkably similar to one another direct correlation of stratigraphic zones and sub zones from sample site of sample site was therefore possible although the methods to achieve this are complex and require the support of several supplementary complementary interpretative techniques coal quality variations and distribution within the original seam are therefore explicable in terms of the detailed factors listed above

the genesis of coal from the viewpoint of coal petrology abstract the genesis of the microscopic constituents of coal macerals and of maceral associations microlithotypes representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats peat microscopy especially promoted the understanding of humification and biological gelification both of which are decisive for the genesis of huminites vitrinites in brown coals and hard coals respectively microbial activity during peatification has been documented by chemists microbiologists and petrologists and recently by electron microscopical observations in coals this activity leads to the incorporation of lipid substances into the humic matter and later influences the chemical physical and technological properties of vitrinites geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal in this process the hydrogel brown coal is transformed to the bitumogel bituminous coal coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration the formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the coalification jumps of the macerals especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite bitumen and micrinite dead carbon bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals bituminite fluorinite and exsudatinite and suggests a higher proportion of algal material in coals than was thought earlier the genesis of various types of inertinite macerals will probably become an increasingly important subject of research especially with regard to rank inertinites that seem to attain their high inertinitic reflectance initially during coalification besides the origin of macerals the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu the peat forming vegetation palaeoclimate water and nutrient supply acidity marine and calcareous influence and fire with examples from euramerican carboniferous coals gondwana coals and tertiary brown coals vegetation water and oxygen supply eh conditions are most important for the generation of coal facies vegetation has been reconstructed with the help of palaeobotany including palynology cuticular analysis and wood anatomy in brown coals and with the study of petrified permineralized peats preserved in coal balls the microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative however the results of palynological and cuticular analyses should be evaluated with caution considering the varying resistance of palynomorphs and cuticles and in the case of palynomorphs their possible extrapaludal origin microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies especially in brown coals the much disputed origin of brown coal lithotypes is considered in detail for hard coals there seems to be agreement that coal layers rich in vitrites and liptinite poor clarite were deposited in wet forest swamps that microlayered liptinite rich clarites are sub aquatic humic muds and that inertinite rich durites represent oxidized peats the origin of liptinite rich durites is controversial either subaquatic muds or oxidized peats the latter perhaps from raised bogs a recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous oligotrophic conditions although raised bogs with a dense arborescent vegetation are known from borneo it seems not probable that most seams which were deposited in foredeeps or steadily sinking graben zones are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams but as in modern peats striking changes of coal facies are commonly caused by hydrological events e g inundations as a consequences of crevasses or of fires that burned the peat the origin of the inertinite rich gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub arctic peats is recommended coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite as well as by hydrogen rich vitrinites with a relatively low reflectance and high fluorescence all due to a strong bacterial activity in peats of low acidity proposals for further research are made in the conclusions

petrographic and reflectance analysis of solvent swelled and solvent extracted south african vitrinite rich and inertinite rich coals maceral transitions during solvent swelling and extraction of two south african coals similar in rank and age but different in maceral composition were evaluated inertinite rich highveld coal dominated by semifusinite and vitrinite rich waterberg coal were used maceral group analysis of solvent extracted and solvent swelled residues showed no changes in the maceral composition for both coals solvent extracted residues exhibited significant observable changes of some particles particle fracturing decrease in reflectance and rounding of particle edges inertinite rich coal exhibited extensive fracturing during solvent treatment random reflectance analyses of both coals showed that solvent treatment reduces reflectance values of both vitrinite and inertinite vitrinite reflectograms showed a shift from the dominant reflecting v types to lower reflecting v types the inertinite reflectograms exhibited an increase in the number of reflecting inertinite types i types with solvent treatment resulting in a broadening of the reflectograms the changes in reflectance between the original and solvent treated coal may be attributed to a combination of structural elemental or surface changes current data for these south african coals suggests a relationship between solvent extraction and mean random reflectance the higher the extraction yields the lower the mean random reflectance

the role of coal petrography in understanding the properties of south african coal abstract the variations in physical and chemical properties of coal can only be explained in terms of its petrographical composition and its rank by means of a trend computer programme quantitative relationships correlation coefficients 0 97 were established between the contents of total carbon and hydrogen daf of south african humic coals and their volatile matter and oxygen contents their calorific value all daf and their mean maximum reflectance of vitrinite rmax the inherent moisture content ash free the vitrinite content mineral matter free and the hardgrove and free swelling indices yielded only semiquantitative relationships correlation coefficients between 0 80 and 0 93 and high standard deviations when expressed in terms of total carbon and hydrogen contents daf these interrelationships are shown graphically by means of a seyler diagram modified for south african coal the relatively poor correlation in the case of vitrinite content is due to the presence of fairly large amounts of reactive semifusinite in most south african coals and for this reason it is necessary to distinguish between normal perhydrous and subhydrous coals depending on the relative difference between determined and inferred vitrinite contents due to the high content of low reflecting inertinite the modal reflectance of vitrinite is also regarded to a better rank parameter than the mean reflectance as the former is not affected by sporadic low or high values from the modified seyler diagram it is also possible to devise a grade type rank classification for south african coals where grade is given by the ash content moisture free basis this classification complements alpern s universal classification of solid fossil fuels the seyler diagram can also be used to delineate fields of the most useful application of south african coals based on the relevant coal properties

is the brazil current eddy dominated to the north of 20 s 1 the brazil current bc originates with the arrival and bifurcation of the southernmost branch of the south equatorial current ssec between 10 20 s previous climatological studies showed a stratified ssec bifurcation and that the resulting southern branch formed a shallow bc a weak western boundary current the analysis of three recent synoptic surveys and global model outputs challenge the description of a continuous bc the ssec bifurcation signal near the continental margin was unclear in the analyses and the velocity fields were dominated by mesoscale eddies recurrent anticyclones that seemed to be related to the meandering bc led us to construct a picture of a flow strongly influenced by topography and probably very unstable given this new emerging scenario we hypothesize that the brazil current is eddy dominated to the north of 20 s

transdimensional love wave tomography of the british isles and shear velocity structure of the east irish sea basin from ambient noise interferometry we present the first love wave group velocity and shear velocity maps of the british isles obtained from ambient noise interferometry and fully non linear inversion we computed interferometric inter station green s functions by cross correlating the transverse component of ambient noise records retrieved by 61 seismic stations across the uk and ireland group velocity measurements along each possible inter station path were obtained using frequency time analysis and converted into a series of inter station traveltime datasets between 4 and 15 seconds period traveltime uncertainties estimated from the standard deviation of dispersion curves constructed by stacking randomly selected subsets of daily cross correlations were observed to be too low to allow reasonable data fits to be obtained during tomography data uncertainties were therefore estimated again during the inversion as distance dependent functionals we produced love wave group velocity maps within 8 different period bands using a fully non linear tomography method which combines the transdimensional reversible jump markov chain monte carlo rj mcmc algorithm with an eikonal raytracer by modelling exact raypaths at each step of the markov chain we ensured that the non linear character of the inverse problem was fully and correctly accounted for between 4 and 10 seconds period the group velocity maps show remarkable agreement with the known geology of the british isles and correctly identify a number of low velocity sedimentary basins and high velocity features longer period maps in which most sedimentary basins are not visible are instead mainly representative of basement rocks in a second stage of our study we used the results of tomography to produce a series of love wave group velocity dispersion curves across a grid of geographical points focussed around the east irish sea sedimentary basin we then independently inverted each curve using a similar rj mcmc algorithm to obtain a series of one dimensional shear velocity profiles by merging all 1d profiles we created a fully three dimensional model of the crust beneath the east irish sea the depth to basement in this model compares well with that averaged from seismic reflection profiles this result is the first 3 dimensional model in the uk with fully quantified uncertainties it shows basin depths and basement structures and their concomitant uncertainties

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

seismological evidence for shallow crystalline basement in southern uplands scotland new evidence is presented and old data re appraised to indicate that the southern uplands of scotland contain crystalline rocks of continental affinity at shallow depth 1 5 km in at least two zones roughly parallel to the caledonoid strike this is in contrast with earlier interpretations especially of the lispb seismic profile1 2 which suggested that the lack of such rocks implied a major discontinuity across the caledonides near the southern uplands fault the new interpretations suggest that basement indistinguishable seismologically from that below the midland valley continues 15 20 km southwards below the southern uplands and that another such crustal block underlies the eskdalemuir eka seismological array further to the south the existence of such blocks radically affects plate tectonic reconstructions of the caledonides especially the margins of the lapetus ocean3 6 only drilling is likely to show whether the contact between basement and the overlying lower palaeozoic greywackes and shales is structural igneous or least likely simple overstep

observed features of the halmahera and mindanao eddies 1 the structure and variability of the halmahera and mindanao eddies he and me which are thought to be quasi stationary eddies are described based on onboard and time series observations in the gateway region of the indonesian throughflow itf the he was found to have a clear anticyclonic eddy structure during all cruises it tilted northward and or westward with increasing depth the he mixes waters from the northern and southern hemispheres and transfers this mixed water to the eastern route of the itf the he shifted northwestward in the boreal summer and the cold phase of enso el nino and southern oscillation and southeastward in the boreal winter and the warm phase of enso in contrast the me with its cyclonic eddy structure was observed only once and seems not to be a quasi stationary eddy it appears in the mean field and is confined above the thermocline the stationary northward undercurrent the mindanao undercurrent was also not found at 7 n east of mindanao but the northern tip of the he was found at this latitude

local earthquake tomography of scotland scotland is a relatively aseismic region for the use of local earthquake tomography but 40 yr of earthquakes recorded by a good and growing network make it possible a careful selection is made from the earthquakes located by the british geological survey bgs over the last four decades to provide a data set maximising arrival time accuracy and ray path coverage of scotland a large number of 1 d velocity models with different layer geometries are considered and differentiated by employing quarry blasts as ground truth events then simulps14 is used to produce a robust 3 d tomographic p wave velocity model for scotland in areas of high resolution the model shows good agreement with previously published interpretations of seismic refraction and reflection experiments however the model shows relatively little lateral variation in seismic velocity except at shallow depths where sedimentary basins such as the midland valley are apparent at greater depths higher velocities in the northwest parts of the model suggest that the thickness of crust increases towards the south and east this observation is also in agreement with previous studies quarry blasts used as ground truth events and relocated with the preferred 3 d model are shown to be markedly more accurate than when located with the existing bgs 1 d velocity model

preliminary interpretation of upper crustal structure across the midland valley of scotland from two east west seismic refraction profiles a seismic refraction survey was carried out over the central coalfield syncline in the midland valley of scotland during may 1984 to determine depth to sub carboniferous basement and to locate intra basement contrasts and structure three refractors were identified and mapped the shallowest is thought to be the top of the lower old red sandstone so that the top layer of the crustal model defines the carboniferous and upper old red sandstone which varies in thickness from 1 5 to 3 5 km deeper refractors are interpreted as the top of the crystalline basement and an intra basement horizon the depth of the top basement refractor limits the combined thickness of lower old red sandstone and lower palaeozoic sedimentary rocks to between 0 and 5 km no obvious correlations with the bathgate gravity and magnetic anomaly are found in the seismic data gravity modelling based on the seismic interpretation suggests that the likeliest cause of the anomaly is thick extrusive basic igneous rocks of carboniferous and or lower old red sandstone age

causes of high crustal conductivity beneath the iapetus suture zone in great britain summary two magnetic variation anomalies in southern scotland and northern england have been linked to the position of the iapetus suture previous magnetotelluric measurements along a 140 km profile that crosses both anomalies have been supplemented by new high quality broad band observations groom bailey decomposition of the impedance and hypothetical event analysis of the magnetic variation data agree in defining different strike directions for the two halves of the mt profile n50 e for the northern part over the southern uplands and n90 e for the southern part over the northumberland trough te and tm mode apparent resistivity and phase data at representative frequencies have been inverted for the two sub profiles separately using the smooth inverse of smith booker 1990 the uppermost layer has a low resistivity is variable in thickness and correlates well with the known position and thickness of carboniferous sedimentary rocks the second layer has a very high resistivity thousands of m and reaches the surface where the lower palaeozoic metamorphic rocks of the southern uplands crop out a relatively rapid transition to low resistivities occurs at depths of between 8 and 16 km the conducting layer appears to be quasi continuous but where the profile crosses the anomalies identified by magnetic variation measurements the conductance increases and the upper surface is shallower the spatial coverage of the magnetic variation data has enabled us to extrapolate conductive features away from the line of section and project the electrical image onto the nec vertical incidence seismic reflection profile in the north sea there is excellent agreement between a number of features in the acoustical and electrical images the shallowing of the low resistivity layer to form a narrow wedge like feature corresponds to the offshore position of the stublick fault while to the north of the fault the top of the layer coincides with a south dipping reflector thought to be a thrust however the zones of high conductance and high lower crustal reflectivity do not in general correlate the good conductor beneath he northumberland trough spans two zones which were differentiated on ihe nec profile in terms of their reflectivity the shape of the conductor s upper surface in the vicinity of the stublick fault agrees well with the model of chadwick holliday 1991 who proposed that the iapetus suture was a whole crustal shear with a gently dipping central ramp the coincidence between the present day low resistivity layer and a surface of weakness that was active 300 400 myr ago is much more readily explained in terms of mineralogy the presence of graphite than the presence of fluids there is also strong support for interpreting the northern conductor in the same way its upper surface is relatively flat and occupies the position predicted as the horizontal detachment surface over which wedges of the southern uplands rocks were thrust its northeastward extension is sampled by a group of carboniferous vents from which xenolith suites of crust and upper mantle origin have been obtained the middle to upper crust is believed to be represented by quartzo feldspathic gneisses that contain abundant graphite

generation of tropical instability waves in the atlantic ocean the spatial and temporal distributions of tropical instability waves tiws in the atlantic ocean are investigated using a combination of current observations with moored instruments deployed at the equator at 23 w and a realistic eddy resolving 1 12 general circulation model of the atlantic ocean the meridional and vertical shears of the zonal current system contribute to the eddy production rates and thus to the generation of tiws in the central tropical atlantic ocean in the southern hemisphere tiws are forced only by baroclinic instability associated with the vertical shear of the central part of the south equatorial current sec in the northern hemisphere baroclinic instability due to the vertical shear of the northern sec nsec as well as barotropic instabilities due to horizontal shears of the equatorial undercurrent euc nsec and nsec north equatorial countercurrent necc contribute to the generation of the tiws since seasonal changes of the instability production rates related to the euc nsec are comparable low while the rates related to the nsec necc are high we suggest that the seasonality of the necc dominates the seasonal modulation of the tiws

structural characterization of vitrinite rich and inertinite rich permian aged south african bituminous coals abstract two south african coals of the same rank and age but different in maceral composition were subjected to extensive structural analyses inertinite rich highveld coal dominated by semifusinite and vitrinite rich waterberg coal were studied to determine structural differences and similarities the two coals had similar carbon content 84 dmmf and vitrinite reflectance mean maximum 0 71 for vitrinite rich vs 0 75 for inertinite rich but differed in hydrogen content 6 23 for vitrinite rich and 4 53 for inertinite rich the inertinite rich coal was more aromatic 86 for inertinite rich and 76 for vitrinite rich and more polycondensed indicated by a higher bridgehead carbon content the inertinite rich coal was structurally more ordered with a higher degree of crystalline stacking both coals had similar average aromatic cluster sizes 16 carbons for vitrinite rich and 18 carbons for inertinite rich and number of cluster attachments 6 attachments for vitrinite rich and 5 attachments for inertinite rich mass spectrometry showed that both coals consist of similar molecular weight distributions ranging to approximately 1700 m z with a maximum abundance of 450 m z for the vitrinite rich coal and 550 m z for the inertinite rich coal compared to the argonne premium coals the south african vitrinite rich waterberg coal was comparable to the coals in the high volatile bituminous range and inertinite rich highveld was closer to the medium to low volatile bituminous range both coals were surprisingly similar in bulk characterization although inertinite rich highveld coal was structurally more ordered hydrogen deficient and more aromatic

mavis an upper crustal seismic refraction experiment in the midland valley of scotland summary the results of the midland valley investigation by seismology mavis are described the experiment consists of three refraction profiles of between 80 and 100 km length across the upper palaeozoic basins of the scottish midland valley three refractors are recognized thus defining four upper crustal layers the top two layers are interpreted as carboniferous plus upper old red sandstone and lower old red sandstone plus lower palaeozoic the structure of the refractor an unconformity separating the two layers mirrors surface structure deeper refractors associated with midland valley crystalline basement show no correlation with surface structure the mavis survey allows the refinement of earlier gross interpretation of upper crustal structure in the midland valley but confirms the existence of anomalously shallow 6 4 km s basement and shows in conjunction with results of previous work that a large area of the central and southern midland valley is characterized by one velocity signature probably indicative of a single terrane

rayleigh wave tomography of the british isles from ambient seismic noise we present the first rayleigh wave group speed maps of the british isles constructed from ambient seismic noise the maps also constitute the first surface wave tomography study of the crust under the british isles at a relatively high resolution we computed interferometric interstation rayleigh waves from vertical component records of ambient seismic noise recorded on 63 broad band and short period stations across the uk and ireland group velocity measurements were made from the resulting surface wave dispersion curves between 5 and 25 s using a multiple phase matched filter method uncertainties in the group velocities were computed by calculating the standard deviation of four dispersion curves constructed by stacking a random selection of daily cross correlations where an uncertainty could not be obtained for a ray path using this method we estimated it as a function of the interreceiver distance group velocity maps were computed for 5 25 s period using the fast marching forward solution of the eikonal equation and iterative linearized inversion at short and intermediate periods the maps show remarkable agreement with the major geological features of the british isles including terrane boundaries in scotland regions of late palaeozoic basement uplift areas of exposed late proterozoic early palaeozoic rocks in southwest scotland northern england and northwest wales and sedimentary basins formed during the mesozoic such as the irish sea basin the chester basin the worcester graben and the wessex basin the maps also show a consistent low velocity anomaly in the region of the midlands platform a proterozoic crustal block in the english midlands at longer periods which are sensitive velocities in the lower crustal upper mantle the maps suggest that the depth of moho beneath the british isles decreases towards the north and west areas of fast velocity in the lower crust also coincide with areas thought to be associated with underplating of the lower crust such as northern ireland the eastern irish sea and northwest wales

maceral types in some permian southern african coals abstract a suite of permian gondwana coals from southern africa exclusive of the republic of south africa were examined petrographically with the exception of a single low volatile bituminous semi anthracite coal from mozambique the coal rank is high volatile bituminous c most coals were dominated by inertinite group macerals primarily semifusinite and detrital inertinite inertodetrinite but with significant secretinite in some cases vitrinite group macerals were absent in several zambian coals when considering these coals it becomes apparent that not all gondwana maceral types determined necessarily fit the iccp definitions

a comparison of long coastal trapped wave theory with observations off peru abstract the agreement between coastal trapped wave theory and observation is studied for the case of observations made off peru during the 1977 cuea joint ii experiment wave properties are calculated using a numerical model with realistic horizontally uniform stratification and realistic bottom topography these properties are then explored as a function of the ratio of the first internal rossby radius of deformation to the shelf slope width the agreement of observed and calculated first mode free wave phase speeds 230 cm s 1 is excellent while modal structures agree more poorly a forced wave calculation using observed winds and currents as input is used to hindcast alongshore currents and sea level in the frequency band where smith 1978 observed free coastal trapped waves during 1977 the model suggests that most of the observed sea level and alongshore velocity fluctuations in the 5 10 day period band are due to free waves originating equatorward of 5 deg s while winds between 5 deg s and

strike slip terranes and a model for the evolution of the british and irish caledonides evidence is presented that many of the major strike faults in the british and irish caledonides were active as sinistral strike slip zones in the end silurian to pre mid devonian period some such as the highland boundary fault moved in this way at an earlier stage in the ordovician these data allow the caledonian rocks lying between the laurentian miogeocline whose basement is represented by the lewisian moine and possibly the dalradian and the gondwanaland miogeocline midland platform and welsh basin to be re analysed as a group of disorganized terranes which originated to the southwest in north america and southwest europe africa prior to the silurian the highland border terrane and northern belt terrane are interpreted as duplicated pieces of a mid ordovician sequence which was a back are to northwest subduction the midland valley terrane is interpreted as a slice of laurentian foreland onto which ophiolites were obducted in the lower ordovician but which became the basement of a continental margin arc to northwest subduction in the mid ordovician the cockburnland terrane is inferred to be part of the same arc repeated and then broken up and dispersed by continuing strike slip the connemara terrane is regarded as an allochthonous piece of the dalradian miogeocline and the south mayo terrane as a remnant of an early ordovician arc and fore arc which in mid ordovician times became a back arc marginal basin to northwest subduction the lake district wexford terrane is part of an arc to southeast subduction under gondwanaland whose activity climaxed in the mid ordovician the central terrane is interpreted as a silurian overstep assemblage which blankets the junction between laurentian and gondwanaland derived oceanic terranes and therefore iapetus is regarded as an ordovician ocean which closed prior to the silurian the model suggests that at the end of the silurian a clockwise rotating gondwanaland having carried laurentia into collision with baltica broke free and created a major sinistral strike slip zone which disrupted the ordovician palaeogeography in the british isles north american sector of iapetus

lispb revisited a new look under the caledonides of northern britain summary the lithospheric seismic profile in britain lispb shot in 1974 included a 700 km long north south profile of the crust and upper mantle of northern britain the wide angle seismic data from lispb was of exceptional quality and coverage making a reinterpretation using current modelling programs worthwhile this reinterpretation shows that the original crustal model published by bamford et al 1978 satisfies the observed first arrival traveltimes but that further detail of crustal velocity structure may be obtained by model shows strong variations in crustal velocity structure that appear to be correlated with geological and tectonic structures mapped at the surface the new lithospheric model is compatible with the observed gravity field when converted to appropriate densities and the variations in loading along the base of the density model show that the lithosphere is close to local isostatic equilibrium profiles of the variation of velocity and density with depth from the new model are compared with measurements of lewisian rocks made at confining pressures up to 8 kbar allowing the seismic model to be interpreted geologically a synthetic normal incidence profile of the new model is superimposed on the nearby nec deep seismic reflection profile and the features imaged by the two techniques are compared