towards an understanding of the neogene tectonostratigraphic framework of the ne atlantic margin between ireland and the faroe islands abstract the neogene succession preserved on the continental margin between ireland and the faroe islands can be divided into two megasequences of miocene and pliocene holocene age the base of each megasequence is marked by a regional unconformity these are of latest oligocene early miocene and early pliocene age respectively and reflect major phases of neogene margin evolution the megasequences and their bounding unconformities reflect a gross two stage depositional history predominantly a response to intra plate tectonism that modified sedimentation patterns and palaeoceanographic circulation the latest oligocene early miocene event marks a major change in the oceanographic regime and can be linked to the establishment of deep water exchange between the arctic and north atlantic oceans the submergence of the greenland scotland ridge which includes the iceland faroe rise and the wyville thomson ridge in the area of study resulted in locally vigorous deep water erosion as northern source deep water flowed through the faroe conduit which is part of the southern gateway for deep water exchange coeval deposition of sediment drifts occurred in the faroe shetland channel and rockall trough as the deep water currents stabilised the early pliocene event marked the widespread instigation of shelf margin progradation to the north west of britain and ireland and to the east of the faroe islands this event is linked to the uplift and erosion of britain ireland and the faroe islands and is part of a larger north atlantic scale uplift significant deep water erosion in the rockall trough suggests that the water circulation pattern was also modified by this event the formation of the key megasequence boundaries occurred during times of significant plate rearrangement and suggests that these events may be correlatable across the whole nw european margin

development of the hatton rockall basin north east atlantic ocean abstract magnetic anomaly and bouguer gravity anomaly maps have been prepared over the hatton rockall basin in the north east atlantic a qualitative interpretation of these maps is presented two cross sectional models have been constructed along lines perpendicular to the axis of the basin the north eastern part of the hatton rockall basin is characterised by circular intrusions and has evolved differently from the south western part which is characterised by linear intrusions that reach the base of the sedimentary sequence it is proposed that the two parts of the basin evolved initially along similar lines and that the south western part of the basin evolved further with a period of extension at the same time as extension between endymion spur and hatton bank

evidence for an early proterozoic crustal province in the north atlantic region published sm nd data for the ketilidian belt of greenland the rockall bank in the north atlantic and the islay inishtrahull block of the british isles are used to suggest the existence of a single early proterozoic crustal province in the north atlantic region with a crustal formation age of c 1 96 ga the three sub provinces also have similar metamorphic histories as documented by sr and pb isotope data they probably represent one or more island arcs which were accreted to the laurentian craton 100 ma later in the 1 85 to 1 75 ga ketilidian laxfordian orogeny a line of suture between the archaean craton and early proterozoic accreted terranes is tentatively proposed

sequence stratigraphy of the middle cambrian daegi formation korea and its bearing on the regional stratigraphic correlation abstract the sediments that comprise the middle cambrian daegi formation in eastern central korea are interpreted to have been deposited in a carbonate ramp setting the daegi formation consists of nine lithofacies argillaceous rock ribbon rock oolitic limestone skeletal limestone microbial limestone intraclastic limestone micritic limestone bioturbated limestone and crystalline limestone which are grouped into three facies associations presenting from base up outer ramp grain shoal and inner ramp facies associations two depositional sequences can be distinguished in the daegi formation sequence 1 in the lower part of the daegi formation comprises a lower transgressive systems tract tst and an upper highstand systems tract hst the tst consists of terrigenous deposits with subordinate limestones while the hst contains various types of limestone sequence 2 comprises the upper half of the daegi formation and was deposited during a tst the sequence stratigraphic analysis of the daegi formation suggests that the sediments were deposited during one 3rd order sea level change during the middle to late middle cambrian the sequence stratigraphic framework of the daegi formation can be excellently correlated with coeval deposits in north china the zhangxia and the lower part of the overlying gushan formations which belong to the same tectonic block as the korean peninsula the sino korean block skb the almost identical sequence stratigraphic frameworks in two separate basins suggest that the sequence stratigraphic development on the skb was mainly influenced by eustatic changes during the middle cambrian

geochemical and isotopic constraints on the nature and age of basement rocks from rockall bank ne atlantic an isotopic and geochemical reappraisal of samples from rockall bank ne atlantic indicates that the granulites and granites present on the bank have little anity with the lewisian of nw scotland with which they have been previously associated new pb rb sr and sm nd data together with existing k ar data indicate that the rocks formed at about 1625 ma although this is contemporaneous with late laxfordian events in nw scotland the high model p value of 8 03 indicates that the rocks were not derived by metamorphic reworking of ancient lewisian crust but largely represent pristine mantle contributions at this time in this sense the rockall terrane is comparable with the islay terrane which has a model p value of 7 9 but is apparently somewhat older c 1800ma the rockall basement rocks therefore represent a pre viously unrecognized crust formation event in the north atlantic region and reconstructions of proterozoic geology will need to take into account the presence of this crustal block of predominantly juvenile mantle derived material the rockall area may also be considered a likely source for the torridonian sediments of nw scotland our knowledge of the geology of the rockall plateau ne atlantic fig 1 has not advanced significantly since the review published by roberts 1975 subsequent work on the eastern ne atlantic area has largely concentrated on the development of the rockall trough which marks the eastern limit of the plateau as summarized by smythe 1989 and on the development of the volcanic passive margin that marks the

a nonlinear modeling and forecasting system of earth fractures based on coupling of artificial neural network and geographical information system exemplified by earth fractures in yuci city shanxi china earth fracturing or fissuring is a natural phenomenon and a major geohazard in many countries the factors that cause the earth to fracture were analyzed in yuci city in shanxi province of china using the geographical information system gis a nonlinear simulation and assessment model of earth fracturing was established using the artificial neural network ann technology to simulate the structure and function of the neural network nn of the human brain with engineering technology the developed nonlinear modeling and forecasting system was used to assess and forecast the earth fracture hazard in yuci city the results of this study provided useful and essential information for scientific policy making in the areas of city planning environmental protection and land development

the jurassic petroleum system north and west of britain a geochemical oil source correlation study abstract recent significant oil discoveries have focused exploration attention on the atlantic margin areas north and west of britain in particular the west of shetlands area these discoveries the foinaven and schiehallion fields each have reserves of 250 to 500 million barrels 39 8 to 79 5 106 m3 of 24 27 api oil while an earlier heavy oil discovery the clair field is the largest undeveloped oil discovery on the u k continental shelf with resources estimated in the range 3 5 billion barrels 477 to 795 106 m3 other discoveries include suilven the very heavy oil in well 204 28 1 and the quadrant 205 strathmore and solan fields potential source rocks in areas adjacent to the west of shetlands include the upper jurassic kimmeridge clay formation equivalent the middle and lower jurassic and the middle devonian the results of geochemical studies of the oils reservoir core extracts and source rocks from released wells from these west of shetlands discoveries show them to be genetically related to north sea oils sourced from the kimmeridge clay formation equivalent detailed geochemical analysis biomarkers source rock reaction kinetics compound specific isotope analysis and fluid inclusion crush leach analysis of the clair field and foinaven complex oils showed that at least two episodes of charging from different source facies within the kimmeridge clay formation took place with an intervening biodegradation event oil charging from middle jurassic lacustrine source rocks is also indicated in the foinaven complex oils the source rocks are shown to exhibit variations in organic facies from very oil prone to mixed oil and gas with a corresponding range of kinetic parameters this complex generation migration and trapping scenario is directly linked with the tectonic evolution of the west of shetlands with major oil generation from very oil prone kimmeridge clay and middle jurassic lacustrine facies into shallow buried reservoirs biodegradation of the oils appears to have occurred shortly after migration into the traps followed later by a second charge of unaltered oil this appears to have been from a different source facies with more terrestrial slower reacting type ii iii kerogens similar to those seen in the kimmeridge clay formation or heather formation in wells on the basin margins kinetics studies show the middle and upper jurassic kerogens to be fast reacting and very oil prone with little potential for later gas generation this finding appears crucial in the understanding of the west of shetlands petroleum system as it explains the lack of large gas accumulations in a basin of such high thermal maturity

mid cenozoic post breakup deformation in the passive margins bordering the norwegian greenland sea abstract since the initial breakup of the norwegian greenland sea in early eocene time chron 24b 53 7 ma the conjugate passive margins have been subject to compression extension magmatism and broad uplifts and subsidence mid to late cenozoic compressional doming basin inversion and reverse faulting occurred predominantly offshore within the rheologically weak deep cretaceous depocenters on the norwegian margin the domes seem to have formed primarily in middle eocene to early oligocene and in early miocene while doming in the faroes rockall region developed in late paleocene to early eocene oligocene and mid to late miocene we suggest that the main driving force was plume enhanced ridge push a testable working hypothesis is that discrete phases of compression were associated with periods of high plume flux in addition the oligocene chron 13 35 ma change in plate motion appears to have generated local shear adjustments along pre existing basement weaknesses forming compressional structures in the overlying sedimentary section this change in plate motion was first manifest by significant extension between the sw barents sea and the conjugate nne greenland margin and led to spreading along the knipovitch ridge mid cenozoic extension and magmatism also preceded the development of the kolbeinsey ridge the associated separation of the jan mayen microcontinent from east greenland must have been strongly influenced by the position of the iceland plume center in addition to the change in extension direction with respect to initial breakup of the norwegian greenland sea in early eocene time the mid cenozoic extension and magmatism is a post breakup phenomena widely spaced areas of neogene uplift occurred along all bordering margins these enigmatic uplifted areas acted as nucleation sites for growth of ice caps and initiated large glacial deposits that built out on the adjacent shelves

the influences of coal mining on the large karst springs in north china environmental damage to a greater or lesser degree is caused by coal mining on the basis of analyzing the hydrogeological conditions of the mining areas this paper provides a sum up of the characteristics of water disasters in north china type coalfield researching into the baimai spring group this paper explores the relation between karst water and groundwater of coal measure strata using the methods of pumping test dynamic observation and tracer test after working over the impact of mine water inrush on spring dynamics this paper estimates the contributory level of karst water to mining drainage this paper holds that the mine water inrush mainly results from karst water with the fault structures acting as channels the keys of mine water inrush are faulty density intersection and endpoint fault finally this paper suggests that mining below mine 9 be forbidden and that below mine 7 be properly mined which provides the scientific basis for preserving springs and preventing water disasters in the mining areas

mesozoic rocks from the hebrides shelf and implications for hydrocarbon prospectivity in the northern rockall trough abstract shallow boreholes drilled in the west lewis and west flannan basins outer hebrides shelf have proved rocks of probable latest bajocian bathonian to barremian age where previously a mainly permo triassic infill has been assumed the full geological succession of the basins remains unproved although the permo triassic history of the basins may be similar the rocks encountered suggest that the basins may have dissimilar geological histories during the jurassic and early cretaceous lithologies are mainly fine grained poorly sorted sandstones or organic rich mudstones some correlation can be made with the isle of skye and the west shetland area the sandstones are poor hydrocarbon reservoirs but the middle jurassic and ryazanian mudstones although immature where drilled have excellent oil source rock potential and may have generated large amounts of hydrocarbons if they are present at depth in the adjacent northern rockall trough

development characteristics and mechanisms of the taigu qixian earth fissure group in the taiyuan basin china since the 1980s increasing human activity and continuing over exploitation of groundwater resources have caused the earth fissures in the rift basin in shanxi china to enter an active phase buildings along these earth fissures have been seriously damaged four massive earth fissures that developed in the taigu and qixian areas of the eastern taiyuan basin endanger the operational safety of the high speed railway that passes through this region using field observations measurements and exploration we determined that the four earth fissures are parallel to each other have a northeast trend and are separated by approximately equal distances the rupture zones of these earth fissures are generally 10 50 m wide and are formed by the main fissures and secondary fissures the width of the zone affected by the earth fissures is 20 50 m based on deformation and the damage done to buildings these fissures formed on the earth s surface their hanging walls are lower than their foot walls forming normal faults and the ground surface around the fissures exhibits ridges and depressions the fissures are connected to deep hidden faults the fault displacement increases with increasing depth which is characteristic of syn sedimentary faults these earth fissures are characterized by vertical displacement and their average annual activity rate is 1 3 cm we believe that the formation of this large scale fissure group may be related to the tectonic structure of the hidden faults in the basin and may also be affected by the continuous regional extensional stress of the basin the current increased level of activity could be caused by the over exploitation of groundwater in the area

geochemistry of organic rich cretaceous and jurassic mudstones in the west lewis and west flannan basins offshore north west scotland implications for source rock presence in the north east rockall trough the west lewis and west flannan basins serve as important calibration sites for understanding the source rock distribution and quality in the north eastern part of the rockall trough in the west lewis basin two shallow boreholes penetrated organic rich oil prone bathonian mudstones which were deposited in a fresh to brackish water environment these mudstones will generate oils rich in paraffins upon maturation organic rich oil prone ryazanian mudstones were discovered in both the west lewis and west flannan basins they are offshore marine mudstones with a predominance of algal organic matter akin to the kimmeridge clay in the north sea and basins west of shetland the bathonian mudstones will generate their hydrocarbon products at higher temperatures than the ryazanian mudstones the presence of lower cretaceous and middle jurassic oil prone mudstones in basins on the hebrides shelf is intriguing and suggests that similar source rocks may be present along the north eastern margin of the rockall trough

geological implications from geochemical and isotopic studies of upper cretaceous and lower tertiary igneous rocks around the northern rockall trough major trace rare earth element geochemistry and isotopic data have been obtained for offshore igneous rocks from around the northern rockall trough ne atlantic ocean most comprise basalts derived from the sub rockall hebridean asthenospheric mantle but subcontinental lithospheric mantle generated the phono tephrites of rosemary bank and melting of upper crust was responsible for the peraluminous dacites of well 163 6 1a crustal contamination of the lavas around the rockall trough suggests that the lewisian islay rockall bank basement terrane boundary crosses the trough and passes between george bligh and rockall banks basalts representing uncontaminated mantle derived material are scarce but the available data indicate that the cretaceous basalts of rosemary bank and anton dohrn have higher 206 pb 204 pb ratios than the younger palaeocene lavas of rockall bank the hebrides shelf and well 163 6 1a implying significant geographic and or temporal changes in mantle composition

petroleum geochemistry of the lower and middle jurassic in atlantic margin basins of ireland and the uk potential hydrocarbon source rocks of lower and middle jurassic age have been reported from outcrop shallow boreholes and exploration wells in atlantic margin basins of the uk hebrides west of shetlands and flanking the ne rockall trough and recently in the continuation of this trend offshore ireland slyne erris and porcupine basins previously these organic rich mudrocks were considered to be of little economic importance due largely to their perceived limited areal distribution and low maturity however recent geochemical studies of oils and shales from exploration drilling of these basins shows the lower and middle jurassic to have considerable potential as effective hydrocarbon source rocks supplanting the late jurassic early cretaceous kimmeridge clay formation equivalents as the only viable oil source rock in the region flanking the atlantic margin in the irish and uk sectors rich oil source potential occurs in two transgressive mudrock cycles of lower jurassic age these are the sinemurian pliensbachian interval and the overlying toarcian section present in basins such as the solan minch hebrides slyne north celtic sea st george s channel and central english channel the middle jurassic source rocks have a more limited areal distribution and occur in the faroe shetland solan west lewis west flannan hebrides slyne and north porcupine basins with oil source potential in regressive marginal marine to lacustrine facies mudrocks geochemical studies were undertaken on mudrocks from the lower and middle jurassic sections in atlantic margin basins outcrop shallow borehole core and exploration well cores and cuttings samples and on oils from drill stem test and shows core and cuttings extracts detailed analyses using gc gc ms and carbon isotopes allowed both characterization of the source rocks and oil to source correlation biomarker and carbon isotope studies of oils from the faroe shetland basin foinaven and schiehallion fields the porcupine basin connemara accumulation the wessex basin wytch farm and kimmeridge oil fields and wells in the slyne basin show strong correlations to the various source rock developments in the lower and middle jurassic the mixed biodegraded foinaven and schiehallion oils have a major waxy component and correlate with lacustrine middle jurassic source rocks in the solan and west lewis west flannan basins middle jurassic sourcing of the connemara oils is also suggested while oils in the slyne basin appear to have been largely sourced by the lower jurassic pabba shale formation oils in the wessex basin wytch farm and kimmeridge appear to have been sourced by hettangian sinemurian mudrocks and those in the north celtic sea basin by toarcian source rocks the results from this study in combination with previously published data show that rich effective oil prone source rocks occur in both the lower and middle jurassic of the atlantic margin basins offshore ireland and the uk these source rocks can be correlated with indigenous oils indicating the existence of a previously under evaluated petroleum system

a reappraisal of the lewisian gneiss complex geochronological evidence for its tectonic assembly from disparate terranes in the proterozoic new u pb single zircon geochronology undertaken on tonalitic gneisses granite sheets migmatites and metasediments from the lewisian gneiss complex on the mainland and the northern part of the outer hebrides nw scotland have been used to test the correlation of so called laxfordian events across the complex from the outer hebrides to the mainland and the current model for the evolution of the complex as a whole the study has revealed that the granite sheets originated in two quite different melting events those on the mainland at loch laxford are ca 1 855 ma old whereas those on harris and lewis with which they are presently correlated are ca 1 675 ma old grey gneisses associated with granites on the south side of loch laxford are confirmed to belong to the northern region a migmatitic grey gneiss on harris has given a protolith age of ca 3 125 ma the currently oldest recognised in the complex detrital zircons in the leverburgh and langavat belts range in age from 2 780 to 1 880 ma and unequivocally demonstrate deposition in the palaeoproterozoic the granulite facies metamorphism in this block is dated from zircon overgrowths at ca 1 880 ma the laxford shear zone which separates the northern and central regions is interpreted to have evolved post 1 860 ma during amphibolite facies metamorphism accompanying deformation which took place at ca 1 740 ma in both regions on harris the langavat finsbay shear zone developed after 1 675 ma when a ca 1 880 ma granulite facies proterozoic arc was juxtaposed against amphibolite facies archaean rocks to the north therefore the shear zones which bound tectonic blocks in the lewisian complex evolved at different times and can be interpreted as terrane boundaries the new data confirm that the lewisian complex was not constructed from one contiguous piece of archaean crust reworked in the proterozoic but was progressively assembled from several discrete terranes during the proterozoic accordingly the former regional divisions of the lewisian complex are here renamed as follows on the mainland the northern region is called the rhiconich terrane and the central region the assynt terrane on the outer hebrides the archaean gneisses of lewis and the northern part of harris comprise the tarbert terrane whereas the newly accreted proterozoic blocks are called the roineabhal terrane in harris and the niss terrane in the north on lewis wider correlations show that the geology of the outer hebrides has more in common with east greenland than mainland scotland on the eastern side of the minch fault

origin of seaward dipping reflectors in oceanic crust off the norwegian margin by subaerial sea floor spreading a remarkable layered acoustic stratification is observed in the upper oceanic crust adjacent to the norwegian continental margin it comprises a seaward dipping complex of reflectors in the form of a wedge we suggest that it is a layered igneous sequence that results when crustal accretion occurs at a subaerial spreading axis and that this phenomenon may commonly occur during the earliest phase of ocean basin genesis

the geology of the uk hatton rockall margin abstract seismic potential field sea bed sample and shallow drilling data have been used to investigate the geology of the uk part of the rockall plateau most of the rockall plateau is underlain by early proterozoic rockall bank islay terrane metamorphic basement although george bligh bank and the north eastern end of hatton bank may be underlain at depth by lewisian rocks the basement crops out on rockall bank but occurs at a much deeper level beneath hatton bank and hatton basin the widespread palaeogene lavas of rockall plateau have been sourced from large central igneous complexes rockall swithin sandastre mammal lyonesse and sandarro local volcanoes and fissures some of the lavas may also have been derived from the incipient rift axis west of hatton bank at the time of continental break up differences in seismic facies allow the extent of the lavas from the large centres to be mapped where the lavas are absent beneath parts of hatton bank either due to non emplacement or subsequent erosion during the cenozoic seismic data image the underlying mesozoic and older rocks here bgs boreholes 99 1 and 99 2a have proved mid cretaceous albian shales and sandstones respectively beneath a thin cenozoic cover the mesozoic and older rocks appear to be quite extensive and are folded and faulted mesozoic strata are not observed on rockall bank in uk waters the post lava cenozoic succession of rockall plateau can be sub divided into three megasequences separated by two unconformities which by analogy with rockall basin have been designated c30 intra late eocene and c10 intra early pliocene the ages can be corroborated by dsdp odp boreholes in the hatton basin the cenozoic succession contains eocene prograding fan sequences contourite deposits on the flanks of the banks and shallow faulting some of which affects the present day sea bed structurally rockall high appears mainly as a large basement block whereas hatton high is more complex exhibiting half grabens inversion structures and reverse fault geometries due to cenozoic tectonism the northern end of hatton high is a large anticline with its axis aligned ene wsw the structural differences between the highs may be due to their locations with rockall high exhibiting fewer tectonic effects due to its more landward intraplate setting further away from plate margin deformation

a study of the symbiotic relationship between tectonic fissures and faults in the fenwei graben system china the fenwei graben system is an important extensional fault depression zone which is the tectonic boundary between the ordos block and the south china block and the north china block the graben system presents an s shape with a total length of 1200 km and a width of 30 60 km and an overall strike of nne due to complex tectonic background and active faults nearly 612 ground fissures develop in these basins and more than 90 of these ground fissures are tectonic fissures which are closely associated with fault activities to reveal the plane symbiotic phenomena profile symbiotic modes and symbiotic mechanism between tectonic fissures and faults in the fenwei graben system the developmental characteristics were investigated in detail by surveying mapping trenching and drilling in the study area the main conclusions are as follows 1 the tectonic fissures of the fenwei graben system are mainly distributed along the margin faults of basins the boundary faults between blocks and the hidden faults within blocks causing serious damages to farmlands houses and roads the symbiosis between these fissures and faults is obvious on the surface 2 the profile symbiotic morphology includes vertical extension type syncline and anticline y type and stepped type 3 the symbiotic mechanisms include vertical growth lateral rupture and clustery derivation 4 the activities of underlying faults give impetus to the formation and expansion of tectonic fissures the exposure of the fissures makes underlying faults continue to develop in the form of surface fractures

the southern margin of the rockall plateau stratigraphy tertiary volcanism and plate tectonic evolution the geological evolution of the southwest rockall plateau in the area of edoras bank has been clarified using seismic reflection gravity and magnetic data four principal reflectors are observed within the tertiary sedimentary sequence i late miocene ii latest early miocene iii late eocene iv earliest eocene a period of pronounced sediment drift accumulation marks the interval i ii reflector iii the top of a sediment wedge prograding southward from edoras bank marks a change from terrigenous to pelagic sedimentation that is probably related to subsidence of the rockall plateau following the separation of greenland from eurasia in the earliest eocene reflector iv marks the top of a wedge shaped seismically transparent layer that also thins southward away from edoras bank on the basis of its seismic attributes and magnetic signature this layer is interpreted as a volcanic sheet formed as part of the north atlantic tertiary volcanic province during rifting of greenland from eurasia the recognition of voluminous volcanic rocks south of edoras bank extends the known area of the tertiary volcanic province several hundred kilometres to the south gravity anomaly modelling and continental reconstructions suggest that the region south of edoras bank is underlain by thinned continental crust a four stage geological evolution for this region is indicated i initial rifting associated with the separation of labrador from greenland in the late cretaceous is characterized by enhanced crustal thinning and subsidence in the region of a rift triple junction ii passive subsidence and accumulation of late cretaceous and earliest tertiary sediments followed the initiation of seafloor spreading in the labrador sea iii blanketing of the area by palaeocene volcanic rocks masked pre existing magnetic lineations providing an explanation for some of the problems in earlier interpretations based mainly on magnetic data iv post volcanic sedimentation continuing to the present day

tertiary compressional structures on the faroe rockall plateau in relation to northeast atlantic ridge push and alpine foreland stresses abstract a number of compressional anticlinal structures are identified in the western and northern part of the faroe rockall plateau these structures occur on that part of the faroe rockall plateau which was above sea level during the latest phase of paleocene plateau basalt extrusion three post basalt compressional phases have affected the plateau most of the compressional structures in the northern part of the plateau are related to ne sw to ene wsw oriented stress which we date to late paleocene early eocene the oligocene phase is interpreted as resulting from n s directed compressional stress which also mainly affected the compressional structures on the northern part of the plateau compressional stress from the northwest seemed to affect the whole of the faroe rockall plateau and we suggest it to be of miocene age it is proposed that during the late paleocene early eocene phase of compression local structure and anomalously oriented gravitational ridge push from the now extinct aegir axis contributed to a local ne sw compressional stress system the two later deformation phases were apparently connected to the regional northwest european stress system with small local modifications