pre folding magnetization reconfirmed for the late ordovician early silurian dunn point volcanics nova scotia johnson r j e and van der voo r 1990 pre folding magnetization reconfirmed for the late ordovician early silurian dunn point volcanics nova scotia tectonophysics 178 193 205 paleomagnetic results have been obtained for three new sites in steeply inclined subarea1 volcanic flows of the dunn point formation from the avalon terrane of nova scotia demagnetization analysis reveals a characteristic magnetization carried by hematite which is similar to that reported in previous studies of this unit a new and improved fold test for the characteristic component combining paleomagnetic and structural data from the present study with paleomagnetic data for vertically dipping flows and laterites studied previously by the authors is significantly positive the new fold test reconfirms the prefolding age of the characteristic component a primary age of magnetization is inferred based on field evidence for early oxidation of the flows the overall mean direction for the characteristic component of d 344o i 60 k 68 6 ass 4 1 paleopole at 2on 130 e corresponds to a late ordovician earliest silurian paleolatitude for avalon of 41 s the latter is much higher than that predicted for the area on the basis of the cratonic north america apparent polar wander path implying a substantial post ordovician displacement 1700 km of avalon with respect to the craton the dunn point result supports previous paleogeographic reconstructions that show avalon together with the continental blocks of hercynian europe and northwestern gondwana

the response of suction caissons to long term lateral cyclic loading in single layer and layered seabeds suction caissons are being increasingly considered as an alternative foundation type to monopiles for offshore wind turbines single caisson foundations or monopods for offshore wind turbines are

silurian deformation in eastern notre dame bay newfoundland eastern notre dame bay newfoundland is divided into five fault bounded terranes they are from north to south the twillingate terrane the chanceport terrane the new world island terrane the dildo run terrane and the port albert terrane the new world island terrane is characterized by fault repeated sequences of middle ordovician to early silurian turbiditic sandstones sansom formation and conglomerates goldson formation the chanceport terrane has a lower volcanic unit and an upper sedimentary unit consisting of red and green siltstones shales overlain by turdiditic sandstones this sequence is structurally overlain by a mafic and felsic volcanic unit the clastic sedimentary rocks of the chanceport new world island and port albert terranes best record the silurian deformation in the area silurian deformation is divided into two deformation events an early silurian d1 thrusting event and a late silurian d2 dextral ductile faulting event the early silurian joey s cove melange constrains th

further paleomagnetic results from the builth wells ordovician inlier wales a characteristic magnetization has been isolated from 18 sites in middle ordovician igneous and sedimentary rocks from the builth inlier wales two conglomerate tests demonstrate that the characteristic magnetization in two of the volcanic units was acquired early perhaps during initial emplacement six sites from the northern and central parts of the inlier give a mean direction of d 153 8 i 69 8 k 45 8 95 10 that passes a regional fold test however 12 sites from the southern end of the inlier in and near the llanelwedd quarry yield a significantly different direction after correction for local tilt d 176 4 i 44 5 k 42 4 95 6 7 the llanelwedd quarry data are anomalous with respect to both results from the northern parts of the inlier and those obtained from approximately coeval rocks from the shelve inlier we have searched for an explanation for the discrepancy between the magnetization directions of the two areas and have now ruled out some possibilities including superimposed magnetization components at one of the two areas the llanelwedd quarry lies within a wedge of dominantly andesitic volcanic rocks that appear only locally and which are overlain by two unconformities that are also not present elsewhere in the inlier one possible explanation for the anomalous nature of the llanelwedd quarry magnetization is that the strata were not horizontal at the time of magnetization either due to early volcano tectonic tilting or primary dips on the flanks of a volcano another possibility is that the llanelwedd quarry rocks were extruded rapidly enough that the geocentric coaxial dipole field hypothesis cannot be applied results from cenozoic volcanic rocks from the western united states suggest that even highly anomalous fields can be preserved virtually unchanged over a number of separate flow events we currently regard this to be the most viable explanation for the anomalous nature of the llanelwedd quarry magnetization we conclude that the data from the 6 northern sites represent the best estimate of the middle ordovician axial dipole field for the inlier

melange development in the boones point complex north central newfoundland the boones point complex in north central newfoundland is a narrow melange belt separating roberts arm terrain volcanic and volcaniclastic rocks to the north from upper ordovician westerly derived

soil strength estimation and pore pressure dissipation for free fall piezocone in soft clay this paper considers centrifuge modelling of free fall piezocones in soft clay and interprets the test data to estimate the undrained shear strength and coefficient of consolidation data from the free fall piezocones which involved dynamic embedment in a normally consolidated kaolin clay sample from various drop heights were compared with equivalent data from piezocone tests the undrained shear strength as interpreted from the acceleration trace of the free fall piezocone was found to be in good agreement with that derived from the piezocone penetration tests the free fall piezocone is also found to produce identical pore pressure dissipation behaviour as for a statically penetrated piezocone despite a significant rise in the pore pressure at the start of the dissipation phase

paleomagnetism and the orocline hypothesis eldredge s bachtadse v and van der voo r 1985 paleomagnetism and the orocline hypothesis in n l carter and s uyeda editors collision tectonics deformation of continental lithosphere tectonophysics 119 153 179 oroclines were originally defined by carey as curved mountain belts which initially were straight or at feast straighter than they are today in the last few years the definition has been broadened to include any curved mountain belt regardless of its original shape since the occurrence of oroclinal bending is best recorded in the change of declination as a function of tectonic setting paleomagnetic and structural data from six potential oroclines have been compiled and analyzed to determine the amount of rotation displayed by the change of paleomagnetic declination relative to the change in strike of the fold belt the arcuate belts investigated are the sicilian calabr n arc and the umbrian arc of italy the swiss portion of the jura mountains the central portion of the appalachian mountains from pennsylvania to virginia u s a the wyoming idaho overthrust belt of western north america and the hercynides of western and central europe the jura mountains and the pennsylvania virginia portion of the appalachians fail to show significant oroclinal bending the wyoming idaho belt shows a combination of rotated possibly oroclinai and unrotated thrust sheets in the sicilian calabrian arc significant oroclinat bending caused by the impingement of the calabria peloritani nappes in the late tertiary can be demonstrated while the umbrian arc of similar age in the northern apennines also shows oroclinal bending on a smaller scale hercynian europe the only belt included in which deformation of basement rocks can be demonstrated shows oroclinal bending at least so as well as a marked original curvature 70 in its western part common to all the orociines studied in this paper is the probable impingement of a rigid block or continental margin during the orogeny causing subsequent deformation and bending of the fold belt

petrogenesis and paleotectonic history of the wild bight group an ordovician rifted island arc in central newfoundland the wild bight group wbg is a sequence of early and middle ordovician volcanic subvolcanic and epiclastic rocks part of the dunnage tectonostratigraphic zone of the newfoundland appalachians a detailed geochemical and nd isotopic study of the volcanic and subvolcanic rocks has been carried out to determine the geochemical characteristics of the rocks interpret their palcotectonic environments and constrain their petrogenetic history the lower and central stratigraphic levels of the wbg contain mafic volcanic rocks with island arc geochemical signatures including lree enriched are tholeiites with e nd t 0 1 to 2 2 type a i lree depleted arc tholeiites with e nd t 5 6 to 7 1 type a ii and an unusual suite of strongly incompatible element depleted tholeiites in which e nd t ranges from 0 9 to 4 6 and is negatively correlated with147sm 144nd type a iii high silica low k rhyolites occur locally in the central part of the stratigraphy associated with mafic rocks of arc affinity and have e nd t 4 7 to 5 4 the upper stratigraphic levels of the wbg dominantly contain rocks with non arc geochemical signatures including alkalic basalts with e nd t 4 6 to 5 5 type n i strongly lree and incompatible element enriched tholeiites that are transitional between alkalic and non alkalic rocks with e nd t 4 4 to 7 0 type n ii and rocks with flat to slightly lree enriched patterns and e nd t 5 1 to 7 4 type n iii rocks with non arc and arc signatures are locally interbedded near the stratigraphic type of the wbg nd isotopic data in the type a i and a ii rocks are generally compatible with mixing partial melting models involving depleted mantle variably contaminated by a subducted crustally derived sediment the petrogenesis of type a iii rocks must involve source mixing and multi stage partial melting but the details are not clear the geochemistry and nd isotope data for types n i n ii and n iii rocks are compatible with petrogenetic models involving variable partial melting of a source similar to that postulated for modern oceanic island basalts comparison of the wbg with modern analogues suggests a 3 stage developmental model stage 1 island arc volcanism eruption of type mafic volcancs stage 2 arc rifting continued eruption of type a i a i eruption of types a ii and a iii mafic volcanics and high silica low k rhyolites and stage 3 back arc basin volcanism continued minor eruption of type a i basalts eruption of types n i n ii n iii basalts stages 1 and 2 volcanism involved partial melting of subduction contaminated mantle while stage 3 volcanism utilized depleted mantle sources not affected by the subducting slab this model provides a basis for interpreting coeval sequences in central newfoundland and a comparative framework for some early paleozoic oceanic volcanic sequences elsewhere in the appalachian orogen

wet sediment deformation in the upper ordovician point leamington formation an active thrust imbricate system during sedimentation notre dame bay north central newfoundland

early paleozoic paleogeography and accretionary history of the newfoundland appalachians new paleomagnetic results were obtained from several units in the central mobile belt of the north central newfoundland appalachians combined with recently published data the results place important limits on interpretations of early paleozoic paleogeography and evolution of the appalachian caledonian orogen the ordovician appalachian margin of north america located at low paleolatitudes and facing roughly south was separated from the southern margin of iapetus avalon armorica by 3500 km primary directions in pillowed volcanic rocks of the moreton9s harbour group that are part of an early ordovician island arc show that these rocks were formed near the north american margin at a paleolatitude of 12 s early to middle ordovician volcanic rocks of the roberts arm chanceport and summerford groups on the other hand were extruded at paleolatitudes of 30 40 s unconformably overlying volcanics of the silurian botwood group were extruded subaerially at a paleolatitude of 24 s combined with tectonostratigraphic data these results suggest the following tectonic history in early ordovician time northerly subduction of the main iapetus basin was accompanied by the formation of a volcanic arc and a back arc basin near the north american margin middle ordovician emplacement of ophiolites on the north american margin reflects the closure of this back arc basin iapetus i and continued northerly subduction in silurian time closed the main basin iapetus ii

early devonian pre acadian magnetization directions in lower old red sandstone of south wales uk summary two components of magnetization have been resolved from the lower old red sandstone of south wales all 39 sampled sites lie north of the variscan front and all but three are largely unaffected by variscan folding thirteen sites yield a high unblocking temperature magnetization component which pre dates acadian mid devonian folding the site mean direction for this component dec 232 2 inc 31 9 95 8 5 yields a pole position lat 7 3 s long 306 7 e which can be assigned an early devonian age a lower unblocking temperature component is present at 38 of the sampled sites this component post dates both the acadian and variscan folding has reversed polarity and a mean direction dec 193 8 inc 7 2 95 2 6 which corresponds to a pole position lat 40 4 s long 338 0 e consistent with a latest carboniferous or early permian age the early devonian pole position confirms the existence of a siluro devonian inflexion in the apparent polar wander path apwp for southern britain which coincides with an inflexion in the apwp for scotland britain north of the iapetus suture indicating the closure of the iapetus ocean by siluro devonian time the early devonian palaeolatitude 17 s 5 is consistent with an early devonian configuration in which gondwana laurentia baltica and avalonia were part of a single supercontinent

near laurentian paleogeography of the lawrence head volcanics of central newfoundland northern appalachians abstract paleomagnetic analyses were completed on two volcanic units of the exploits group in newfoundland s central mobile belt which are part of an ordovician arc back arc system the tea arm volcanics display scattered and unstable characteristic directions that cannot be interpreted however stable end points in six sites supported by great circle analysis of seven sites in the mid arenigian to llanvirnian lawrence head volcanics yield a tilt and strike corrected characteristic direction of d 56 i 23 95 19 k 14 n 6 the magnetization is carried by magnetite and passes a tilt test the corresponding paleolatitude of 12 10 is interpreted as southerly and is similar to the paleolatitude of 11 4 for arc volcanics of the nearby moreton s harbour group however this near laurentian paleolatitude is distinctly different from the paleolatitude of 31 8 reported for the robert s arm cottrell s cove chanceport summerford volcanic terrane the low paleolatitude of the lawrence head volcanics supports the location of a major ordovician subduction system near the laurentian margin of iapetus whereas the present day juxtaposition of latitudinally distinct elements in the area represents a complex accretionary history involving early silurian or older thrusting and younger strike slip faulting of several iapetan island arc terranes to laurentia

lithoprobe onshore seismic reflection transects across the newfoundland appalachians vibroseis seismic reflection data have been recorded to 18 s two way traveltime along three transects across the island of newfoundland the upper crust has both steep and subhorizontal reflectors consistent with a ramp flat style of deformation whereas the middle and lower crust are largely free of regional flats reflectors descend through ca 20 km of vertical section in the middle and lower crust to flatten into the moho or perhaps cut through it in places the moho is interpreted to be no younger than the dipping reflectors reflection fabrics interpreted to be indicators of dominantly mid ordovician to mid silurian strain show consistent orientations among the transects and divide the crust into two blocks a northwestern block is characterized by upper and middle crustal reflectors dipping mostly southeast at variable angles this block is underlain to the southeast by supposedly younger and dominantly northwesterly dipping reflectors that define a northwest tapering wedge shaped block floored

palaeomagnetic data from the borrowdale volcanic group volcano tectonics and late ordovician palaeolatitudes nineteen palaeomagnetic sampling sites from the borrowdale volcanic group between borrowdale and langdale english lake district yield high unblocking temperature magnetization components which postdate the structural tilt and therefore postdate the formation of the broad block faulted syncline which characterizes this part of the central lake district the mean magnetization direction before tilt correction dec 347 2 inc 61 9 95 6 9 corresponds to a palaeolatitude of 43 s 5 7 the magnetization is associated with pervasive late ordovician hydrothermal alteration and is certainly pre devonian based on comparison with available palaeomagnetic data from southern britain this implies that the block faulted synclinal structure of the borrowdale langdale region is pre acadian in age consistent with recent interpretations of late ordovician volcano tectonics based on mapping and volcanological studies

the tectonics and depositional history of the ordovician and silurian rocks of notre dame bay newfoundland reply in the notre dame bay region ophiolitic rocks underlie a thick sequence of lower ordovician volcanic arc rocks to the north of the lobster cove chanceport fault neither this fault nor the lukes arm sops head fault shows evidence of very large strike slip movements as parts of the same arc together with much arc derived detritus straddle both faults towards the east this arc derived detritus becomes more distal in aspect and passes laterally into the dunnage melange during the middle ordovician epoch late llandeilo and early caradoc most areas show a marked decrease in volcanic activity and in the amount of coarse detritus deposited coarse turbidites reappear at different times in different areas during the late ordovician these are related to several fault bounded basins and to movements on the lukes arm sops head fault many of these faults particularly in the east are marked by olistostromes several of which can be dated by fossils as late ordovician and early silurian the whole

tracer derived freshwater composition of the siberian continental shelf and slope following the extreme arctic summer of 2007 we investigate the freshwater composition of the shelf and slope of the arctic ocean north of the new siberian islands using geochemical tracer data 18o ba and po 4 collected following the extreme summer of 2007 we find that the anomalous wind patterns that partly explained the sea ice minimum at this time also led to significant quantities of pacific derived surface water in the westernmost part of the makarov basin we also find larger quantities of meteoric water near lomonosov ridge than were found in 1995 dissolved barium is depleted in the upper layers in one region of our study area probably as a result of biological activity in open waters increasingly ice free conditions compromise the quantitative use of barium as a tracer of river water in the arctic ocean

remagnetizations and postfolding oroclinal rotations in the cantabrian asturian arc northern spain devonian carbonates in the cantabrian arc reveal characteristic magnetizations with coherent shallow upward inclinations the magnetizations appear to be carried by magnetite within site directions are very well grouped but site mean declinations range from easterly to south southwesterly in in situ as well as tilt corrected coordinates as has also been observed in previous studies of other formations in the arc the widely varying declinations of all studies roughly correlate with the overall structural trends of the arc and suggest that the sites underwent rotations in a process that involved folding about vertical axes and tightening of arc upon tilt correction the inclinations of our study on the other hand become scattered and it is concluded that the magnetizations were acquired after late carboniferous folding about horizontal axes the oroclinal rotations therefore also must have occurred after the late carboniferous folding phase the previous paleomagnetic results had been interpreted mostly as primary magnetizations residing in hematite however inclination only fold tilt tests applied to these results suggest that many if not all of the directions were acquired during the earlier stages of the late carboniferous folding thus all paleomagnetic results from the cantabrian arc appear to be remagnetizations but the ages of the remagnetizations vary from pre to synfolding for the mostly hematitic formations to postfolding for the devonian carbonates the reversed polarity inclinations of the hematite bearing formations have mean values ranging from 25 to 5 whereas the carbonates have a mean inclination of 8 on the basis of inclinations predicted for the area from results from stable europe the pyrenees and the iberian meseta the ages of these remagnetizations can be inferred to range from about 320 ma to 260 ma because all the remagnetizations reveal rotated declination patterns the oroclinal rotations occurred well after the main phase of hercynian deformation 320 280 ma while the timing of the rotations is unconstrained at the younger end they must have occurred during or after the permian best estimate is less than 260 ma which is much later than anticipated from other geological considerations

field trials of suction caissons in clay for offshore wind turbine foundations a programme of testing on suction caisson foundations in an artificially prepared sand test bed near luce bay in scotland is described the tests are relevant to the design of either monopod or quadruped foundations for offshore wind turbines records are presented for suction installation of the caissons cyclic moment loading under both quasi static and dynamic conditions to simulate the behaviour of a monopod foundation and cyclic vertical loading and pullout of caissons to simulate one footing in a quadruped foundation variations of stiffness with loading level of the foundation are observed with high initial stiffness followed by hysteretic behaviour at moderate loads and degradation of response at high loads some implications for the design of wind turbine foundations are briefly discussed

deep seismic reflection profile across the northern appalachians a marine seismic reflection line across the northeast extremity of the canadian appalachians in newfoundland indicates a collisional suture in the lower crust beneath the central ophiolitic dunnage terrane the thrust and fold belt miogeocline above the grenville basement and the dunnage and gander tectonostratigraphic terranes all appear to be allochthonous with respect to lower crustal basement the gander avalon terrane boundary to the east is a near vertical feature that penetrates the crust the data also suggest that the ancient passive margin of north america extends eastward under the dunnage terrane for about 70 km the newfoundland deep seismic experiment indicates major tectonic differences compared to results for the southern appalachians

geology of eastern new world island newfoundland an accretionary terrane in the northeastern appalachians eastern new world island is located in the northeastern part of the dunnage zone of the newfoundland appalachians contrary to previous interpretations deposition of the sedimentary sequences in this area took place in a single basin although styles of deposition varied laterally within this basin four generations of deformation have affected these rocks d 1 deformation was progressive and highly heterogeneous and it is associated with thrusting movement zones are present at the bases of thrusts locally with zone parallel cleavage s 1 these zones show a complex deformation history folds overprinted by cleavage folds with axial plane cleavage and folded cleavages all occur movement zones are locally associated with technically deformed olistostromes repetition of the general stratigraphic sequence occurs as a consequence of d 1 thrusting the thrusting direction on eastern new world island however cannot be unequivocally determined superimposed on d 1 deformation there is regional folding f 2 with a well developed regional s 2 axial plane cleavage two types of f 3 folds are present and these are associated with strike slip faulting f 4 deformation caused the formation of minor kinks d 1 deformation is lower silurian and younger in age and is included in the acadian orogeny of the appalachians evidence for earlier taconic deformation is absent the over all geometry of eastern new world island is that of a steeply dipping thrust pile with a complex internal geometry it strongly resembles parts of the imbricate fan complex of the southern uplands of scotland

paleogeography of some vestiges of iapetus paleomagnetism of the ordovician robert s arm summerford and chanceport groups central newfoundland in the central mobile belt of newfoundland three volcanic groups of early middle ordovician age robert9s arm summerford and chanceport are thought to have formed within the iapetus ocean demagnetization analyses of 328 samples from these three groups has yielded similar magnetic directions calculated by combining stable end point directions and great circle poles the three groups yield similar poles located at 6 n 140 e 8 n 140 e and 10 n 131 e corresponding to paleolatitudes of about 30 s the magnetization of the robert9s arm group passes the tilt test and one site shows normal polarity antipodal to the directions of the other sites the paleolatitude of 31 s places the volcanic rocks at the time of their formation in the middle of iapetus between the laurentian margin at about 15 s and the location of the avalon terrane at 50 s subsequent accretion to laurentia and the presently adjacent island arc rocks represented by the moreton9s harbour group occurred after northward drift in the later ordovician earliest silurian and before the middle silurian

palaeomagnetism of palaeozoic rocks from the cabo de penas asturia spain summary ordovician volcanic samples of the cabo de penas area yielded a primary remanent magnetization d 202 i 78 95 6 which is partially or entirely overprinted by a late palaeozoic remagnetization late devonian early carboniferous sedimentary samples reveal a pre or syntectonic carboniferous remanent magnetization similar to the secondary one of the volcanic samples a soft post tectonic component appears also in few samples for which a late carboniferous age is inferred comparison of the carboniferous remanent magnetizations and structural parameters suggests that in a late stage of the deformation the sites have undergone minor rotations around a vertical axis a strike correction is therefore proposed to take such an effect into account the average of the corrected mean site directions d 178 i 19 95 9 is considered to be a good approximation of the early or middle carboniferous palaeomagnetic direction in asturia

structural evolution of a transpression zone in north central newfoundland abstract a dextral transpression zone in notre dame bay north central newfoundland was active in middle to late silurian times following the closure of a marginal basin the deformation in the transpression zone was complex and involved several generations of structures deformation was initially distributed over wide low strain zones through the formation of a penetrative regional cleavage with steepening and overturning of the strata the orientation of the sequence was favorable for strike slip bedding parallel movement and the deformation became more efficiently accommodated by shear within the incompetent lithologic horizons forming localized shear zones in high strain zones the sheared incompetent horizons define a belt of melange the boones point complex centered on the contact between a volcanic island arc terrane to the north and a marginal basin terrane to the south two cleavages with similar orientation and morphology were generated at different times during the structural evolution of the transpression zone one of the cleavages is regional in distribution and is transposed by the shear zones folds with no axial planar cleavage but a cleavage cutting obliquely across their hinges are reported they have the geometry of transected folds but are clearly the result of overprinting by a younger generation of cleavage

paleomagnetism of the moreton s harbour group northeastern newfoundland appalachians evidence for an early ordovician island arc near the laurentian margin of iapetus paleomagnetic results have been obtained from mafic volcanic units in the upper part of the moreton s harbour group which is part of an accreted island arc terrane that is preserved in the notre dame bay subzone of the central mobile belt of the newfoundland appalachians detailed thermal and alternating field demagnetization reveals a stable characteristic component of magnetization carried by magnetite at a large number of sites in pillow basalts and coeval basaltic dikes the intrusives contain both polarities and a primary age for the characteristic magnetization is indicated by a positive contact test for one of the dikes and by a positive structural test involving a correction for block rotations strike correction the overall mean direction for the characteristic component after tectonic tilt and strike correction flows and intrusives d 171 i 22 k 22 6 95 6 5 pole 29 n 135 e flows d 166 i 22 k 33 2 95 6 5 corresponds to an early ordovician paleolatitude for the arc of 11 s which is indistinguishable from the expected paleolatitude of the north american margin this implies that the arc formed at or near the margin of the craton in contrast the avalon block which formed the other margin of iapetus was widely separated from the arc and the craton at this time the early ordovician paleolatitude of the arc terrane supports a tectonic model in which coeval ophiolitic sequences inboard of the arc were formed in a narrow ocean basin between the arc and the craton subsequent convergence between the arc and laurentia in middle ordovician time resulted in closure of this narrow ocean basin and obduction of the back arc basin oceanic crust onto the ancient margin of the craton thus giving rise to the taconic orogenic pulse in the newfoundland appalachians

the response of flexible piles to lateral loading the majority of piles encountered in practice may be regarded as flexible under lateral loading that is the induced deformations and bending moments are confined to the upper part of the pile and the overall length of the pile does not significantly affect the response of the pile the results of a parametric study conducted using the finite element method and treating the soil as an elastic continuum with a linearly varying soil modulus are presented as simple algebraic expressions these expressions are similar in form to those which arise from a winkler idealization of the soil enabling immediate estimates to be made of the active length of the pile the ground level deformations and the maximum bending moment down the pile in addition expressions are presented quantifying the effect of interaction between neighbouring piles from which the behaviour of groups of piles subjected to lateral loading may be deduced application of the solutions is demonstrated by the analysis of lateral loading