granite ascent and emplacement during contractional deformation in convergent orogens based on a case study in the central maine belt of west central maine u s a it is proposed that crustal scale shear zone systems provide an eaective focussing mechanism for transfer of granite melt through the crust in convergent orogens during contractional deformation flow of melt in crustal materials at depths below the brittle plastic transition is coupled with plastic deformation of these materials the flow is driven by pressure gradients generated by buoyancy forces and tectonic stresses within the oblique reverse central maine belt shear zone system stromatic migmatite and concordant to weakly discordant irregular granite sheets occur in zones of higher strain which suggests percolative flow of melt to form the migmatite leuco somes and viscous flow of melt channelized in sheet like bodies possibly along fractures cyclic fluctuations of melt pressure may cause instantaneous changes in the eaective permeability of the flow network if self propa gating melt filled tensile and or dilatant shear fractures are produced due to melt enhanced embrittlement in homogeneous migmatite and schlieric granite occur in zones of lower strain which suggests migration of partially molten material through these zones en masse by granular flow and channelized flow of melt carrying entrained residue founded on the central maine belt case study we develop a model of melt extraction and ascent using the driving forces stress conditions and crustal rheologies in convergent especially transpressive orogens ascent of melt becomes inhibited with decreasing depth as the solidus is approached for intermedi ate a h2o muscovite dehydration melting the water saturated solidus occurs between 400 and 200 mpa near the brittle plastic transition during high t low p metamorphism where the balance of forces favors sub horizontal fracture propagation emplacement of melt may be accommodated by ductile flow and or stoping of wall rock and inflation may be accommodated by lifting of the roof at shallower crustal levels and or sink ing of the pluton floor the resultant plutons have sub horizontal tabular geometries with floors that slope down to the ascent conduits although these plutons may have locally discordant relations with country rock structures when viewed at the crustal scale granite ascent and emplacement in convergent orogens are syn tec tonic processes 1998 elsevier science ltd all rights reserved

in situ pore pressures what is their significance and how can they be reliably measured the intergranular fluid pressure in a soil matrix pore pressure has fundamental influence on the engineering behaviour of soils often assumptions are made regarding pore pressures however in critical analyses direct measurement of pore pressures should be made this paper discusses the pore pressure measurements made at the ormen lange field pore pressure measurements using piezometers indicate pore pressures in excess of hydrostatic at the back wall of the slide and the stornese feature hydrostatic pressures have been identified on the north flank and in the basin of the slide dissipation tests performed during the field investigation did not yield reliable in situ pressure estimates the pore pressure measurements from the piezometers are consistent with the assumptions required in the theoretical slope stability analyses explaining the storegga slide mechanism as no standard commercially available technology for autonomous pore pressure monitoring exists the paper describes also the technical solutions designed and implemented for pore pressure monitoring at the ormen lange field

late cenozoic glacial history and evolution of the storegga slide area and adjacent slide flank regions norwegian continental margin abstract acoustic data and sediment cores collected from the storegga slide and its adjacent slide flanks i e the voring plateau to the north and the north sea fan to the south have been used to study the late cenozoic glacial history and geological development of this region age constrains obtained from the investigated cores show that the fennoscandian ice sheet reached the shelf edge during marine isotope stages mis 12 10 8 6 and 2 ice sheet fluctuations within each glaciation might have occurred as is evidenced for the last glacial maximum mis 2 the first extensive ice advance is identified in the early pleistocene at c 1 1 ma however between 2 6 and 0 5 ma the ice sheets were largely restricted to the fjords and inner shelf during each glacial maximum glacigenic debris flows gdfs transported basal till deposited at the shelf edge into the deep sea along the entire studied margin the most voluminous gdf sequences are found on the southern storegga slide flank north sea fan where the individual flows are found as far as 500 km from the shelf edge on the voring plateau glacimarine hemipelagic sedimentation has dominated the last c 250 000 yr during mis 2 such sediments were rapidly deposited covering the upper slope limited gdf units in this region between c 15 700 and 15 000 14c yr bp i e during the last deglaciation of the norwegian margin a presumed meltwater plume released from the disintegrating norwegian channel ice stream transported and rapidly deposited up to 20 m of fine grained sediments in the region north of the north sea fan the rapid deposition of large volumes of gdfs glacimarine and meltwater related sediments might have influenced the stability of the slope sediments in the studied region promoting conditions favorable for failure furthermore these high sedimentation rates also partly account for the high subsidence rates observed on the norwegian continental margin in the late cenozoic

morphology and mechanics of submarine spreading a case study from the storegga slide spreading is a common type of ground failure in subaerial environments however this type of mass movement has hardly been documented in submarine settings in this paper we show that spreading covers at least 25 of the storegga slide scar area a giant submarine slide located offshore mid norway the morphological signature of spreading is a repetitive pattern of ridges and troughs oriented perpendicular to the direction of movement two modes of failure can be identified retrogressive failure of the headwall and slab failure and extension both involving the breakup of a sediment unit into coherent blocks these blocks are displaced downslope along planar slip surfaces limit equilibrium modeling indicates that loss of support and seismic loading are the main potential triggering mechanisms the extent of displacement of the spreading sediment is controlled by gravitationally induced stress angle of internal friction of the sediment pore pressure escape and friction the resulting block movement pattern entails an exponential increase of displacement and thinning of the failing sediment with distance downslope sediment properties explain the remaining spatial variation of ridge and trough morphologies associated with spreading

significance of the early fabric in the contact metamorphic aureole of the 590 ma ben vuirich granite perthshire scotland an early fabric is preserved in pseudomorphs of contact metamorphic cordierite and andalusite found in hornfelsed dalradian rocks at the nw margin of the ben vuirich granite as previous work had suggested that this fabric may be of regional tectonic d1 origin and taken as evidence that a pre 590 ma neoproterozoic orogenic event had affected the dalradian supergroup the textures found in the hornfelses and their porphryoblasts are illustrated and described in detail three types of hornfels are recorded unspotted cordierite and andalusite bearing cordierite was altered to mica garnet and kyanite and andalusite pseudomorphed by kyanite during the subsequent d2 regional metamorphism the early fabric is finely spaced and associated with a weak shape fabric except in the higher grade hornfelses where it is more intensely developed and formed during the deformation of irregularly shaped cross cutting granitic veinlets it is concluded that the hornfels fabric is probably bedding modified by intrusion related deformation rather than a d1 fabric parallel to bedding the implication of this finding is that intrusion of the ben vuirich granite occurred during the vendian c 650 ma rifting phase at about the time that the tayvallich lavas were being deposited and before any significant deformation of the dalradian rocks had taken place there is no unambiguous evidence to show that the early fabric in the hornfels at ben vuirich formed during a precambrian regional scale deformation of the dalradian block

mineralogical and microstructural development of the sediments on the mid norwegian margin abstract as a contribution to the understanding of the mechanisms and causes for storegga slide the mineralogy and microstructure of samples from a series of boreholes from the slide neighbourhood have been analysed the results show a change from kaolinite rich oozes through smectite rich fossilferous clays clayey oozes to illite dominated hemipelagic and glacial sediments from the brygge eocene to earliest miocene to kai earliest miocene to late pliocene to naust formations late pliocene to present respectively the deposits are interpreted as the effect of denudation of weathered regolith and an increase in physical erosion in conjunction with the deterioration of the climate and the initiation of glacial cycles during the late cenozoic during the quaternary climate has controlled the mixing of current transported fine grained sediments that are probably derived from the region around the faeroe islands and coarser grained glacial sediments containing a broad spectrum of minerals eroded from the north sea and scandinavian mainland since currents have been most important during warm periods sediments from these periods are finer grained and contain more smectite than the glacial sediments however it is concluded that the mineralogical differences between finer grained sediments from warm periods and the coarser grained glacial sediments are not great enough to explain the ubiquitous utilisation of glacial marine hemipelagic sediments as slip planes for the slides in the area but that this is probably a consequence of the differences in the grain size distribution of the sediments voids that may be casts left behind by gas hydrates have been observed

intrusive rocks in the ophiolitic melange of crete witnesses to a late cretaceous thermal event of enigmatic geological position the ophiolitic melange in the uppermost tectonic unit of the cretan nappe pile contains crystalline slices which consist of a low pressure high temperature metamorphic sequence and synmetamorphic intrusions ranging in composition from diorite to granite the plutonic rocks conform to two different igneous suites dominated by diorites in eastern and granites in central crete displaying i type and a type characters respectively some of the granites from central crete are classified as transitional i s type they are closely associated with migmatitic paragneisses based on major and trace element ree sr and nd isotope geochemistry the mafic members of both suites are derived from a depleted mantle source the higher concentrations of p and ti in the mafic members of the igneous suite in central crete and the deviant trend of the whole suite may be explained by a different mantle source or a lower degree of partial melting in both suites magmatic evolution was governed by fractional crystallization of amphibole clinopyroxene plagioclase and minor phases in addition mixing or mingling of compositionally different magmas is indicated for the intrusive suite of eastern crete whereas in central crete the magma composition was at least partially modified through assimilation of meta pelites the geochemical results suggest that the plutonic rocks formed in a supra subduction zone setting however a formation during continental lithospheric extension cannot be ruled out published and new rb sr and k ar dates on amphiboles and biotites from intrusive rocks and their metamorphic country rocks show that the peak of the low p high t metamorphism and the intrusion of the two igneous suites testify to the same thermal event of late cretaceous age a similar late cretaceous association of metamorphic and plutonic rocks has been described from the uppermost tectonic unit in the attic cycladic crystalline complex together with the cretan occurrences they form a small sector radiating ssw along a distance of 300 km across the general trend of the tectonic zones in the hellenic orogen this n s alignment is regarded as a primary feature which may delineate the frontier zone between the hellenides and the taurides the real paleogeographic position and geodynamic significance of the late cretaceous low pressure high temperature belt however remains enigmatic

the last phase of the storegga slide simulation of retrogressive slide dynamics and comparison with slide scar morphology the prehistoric storegga slide one of the world largest known submarine slides took place about 8200 years ago most likely the slide was triggered by an earthquake in a steeper slope area in the distal part of the slide the present day s morphology of the slide area indicates that major parts of the slide took place as a sequential failure process spreading successively from the far end to the present shelf edge numerical simulations illustrating this retrogressive back stepping behaviour are presented for the last phase of the storegga slide as it reached today s upper headwall the applied rheological model is based on a bingham fluid with a history dependent yield strength and consistency

soil conditions and slope stability in the ormen lange area abstract the ormen lange gas field is located in 850 1100 m water depth in the slide scar of the enormous storegga slide this slide occurred about 8200 years ago and left steep and high scarps above and below the planned field development area today s stability of these scarps has been a major concern for the field development work this paper gives an overview of soil investigations evaluation of potential trigger mechanisms and stability analyses performed to demonstrate adequate conditions the area under consideration is large with a limited number of geotechnical borings and integration of geological geophysical and geotechnical information was required to develop a geotechnical model of the area the stress history and the soil conditions are strongly influenced by rapid deposition during glacial periods by the loss of overburden from the storegga slide and glacial loading along the shelf edge natural and project induced triggering sources with potential for generation of renewed slide activity were evaluated with respect to magnitude and location and possible influence area relative to the major scarps stability analyses were carried out for critical sections of the scarps under gravity loading and under combination of gravity and potential triggering sources applying drained analyses for long term gravity loading and undrained analyses considering gravity combined with short term load effects project induced load effects like weight of equipment and rockfills anchor loads and effects of drilling and production activities were found to have insignificant effect on the large scale stability of the headwalls and local surficial slope failure can be handled by adequate engineering and lay out with respect to natural triggering sources it was concluded that an extremely strong earthquake with a very low probability of occurrence is the only realistic mechanism for triggering of new slides in the ormen lange area

seafloor instabilities and sediment deformation processes the need for integrated multi disciplinary investigations abstract in this paper we present the current practice of investigations of seafloor instabilities and deformation processes based on extensive research conducted over the last years which sets the scene for future research activities in this field the mapping of the continental margins and coastal areas with ever increasing resolution systematically reveals evidence of instabilities and deformation processes both active and palaeo features in order to properly assess the hazards and risks related to these features an integrated and multi disciplinary approach is essential but challenging such an approach consists of combining field data geophysics geology sedimentology geochemistry and geotechnical data with numerical simulations constrained by results from laboratory data as such it is of paramount importance to build a common knowledge base and understanding that unify these disciplines into more complete and conceptual models constrained by all the data we review the status of this integrated approach adapted to palaeo landslides e g storegga ana vesteralen and recent deformations finneidfjord nice gulf of guinea allowing to identify gaps in our knowledge at these sites by reviewing these case studies one can conclude that each case remains highly site specific in which both the regional and local geological tectonic settings have a distinct effect of the type of instability or deformation taking place or that can take place our knowledge on the actual triggers remains poorly constrained and there is even ambiguity for historic landslides e g finneidfjord also our knowledge of the preconditioning factors is incomplete there is a general lack of geotechnical data both in situ and from laboratory and therefore modelling the dynamics e g rheology of the instabilities relies on a number of assumptions rather than facts in addition excess pore pressure and its evolution is one of the key parameters driving instabilities despite this fact in situ excess pore pressure is rarely measured or monitored much work remains to be done to relate and integrate geotechnical data with geophysics e g through inversion and rock physical models in order to obtain additional quantitative information from the sub surface but also with respect to partial saturation free gas hydrate and pore pressure behaviour or lithologies it is of critical importance to be able to identify the different processes which can lead to hazardous situations which include establishing recurrence intervals timing and frequencies through event recognition and age control and magnitudes so that proper mitigation measures can be developed in this perspective the smaller scale instabilities deserve much attention as there are many instances where such features had far reaching consequences for society e g nice finneidfjord in that perspective human interferences e g exploitation drilling blasting loading must be one of the factors that should be taken into consideration

critical role of wave seabed interactions in the extensive erosion of yellow river estuarine sediments abstract integrating field observations in the high erosion rate region of the chinese coastal zone northern estuary of the yellow river were used to investigate the role of wave seabed interactions in seabed erosion combined with laboratory erosion experiments on the variations in sediment erodibility due to cyclic wave loading the field results highlight a strong erosive event that occurred in the presence of high waves during which the seawater turbidity increased sharply from 50 ftu to 600 800 ftu and the bed elevation decreased by 7 7 mm h over 27 h the laboratory results attribute this type of erosion to the contribution of wave actions on seabed sediments where the waves probably acted as a plough and reduced the threshold velocity and critical shear stress values thus enhancing sediment transport that also occurs due to the shear effect of near bed currents during fair weather conditions wave induced liquefaction characterised by the uneven build up of excess pore pressures at different buried depths may also enhance sediment erosion by generating vertical pore water seepage within the sediment and inducing internal sediment re suspension the field observations allowed us to construct a regional mathematical model of seabed erosion that parameterises the wave seabed interactions as well as to explore the implications of this model for extensive erosion of yellow river estuarine sediments this research represents a major step towards validating the critical role of wave induced interactions in extensive sediment erosion events within a shallow estuarine system

laboratory investigation of pore pressure dissipation in clay around permeable piles excess pore water pressures induced by pile driving could have a detrimental effect on a project especially on the construction sequence and ground settlement measures that can effectively accele

silica cycling and isotopic composition in northern marguerite bay on the rapidly warming western antarctic peninsula the southern ocean is a key region for silica si cycling and the isotopic signatures established here influence the rest of the world s oceans the climate and ecosystem of the southern ocean are changing rapidly with the potential to impact si cycling and isotope dynamics this study examines high resolution time series dataset of dissolved si concentrations and isotopic signatures particulate si concentrations and diatom speciation at a coastal site on the western antarctic peninsula wap in order to characterise changes in si cycling with respect to changes occurring in productivity and diatom assemblages dissolved and particulate si phases reflect the dominant control of biological uptake and combined with isotopic fractionation were consistent with a season of low intermediate productivity biogenic si is tightly coupled to both chlorophyll and particulate organic carbon at the sampling site consistent with diatom dominated phytoplankton assemblages along the wap variability in diatom speciation has a negligible impact on the isotopic signature of dissolved si in surface waters although this is unlikely to hold for sediments due to differential dissolution of diatom species a continued decline in diatom productivity along the wap would likely result in an increasing unused si inventory which can potentially feed back into si limited areas promoting diatom growth and carbon drawdown further afield

terrestrial style slow moving earthflow kinematics in a submarine landslide complex abstract morphometric analysis of simrad em300 multibeam bathymetric dems reveals details of deformation patterns in a 145 km2 submarine landslide complex that are commonly associated with slow moving earthflows in terrestrial settings this mode of failure where existing landslide debris is remobilised repeatedly along discrete shear boundaries and is progressively conveyed through the complex has not previously been recognised in the submarine environment the kinematics contrast with the more traditional models of submarine landslide complex development in which repeated catastrophic failures each mobilise new source material to form a composite stacked landslide deposit in our study of the tuaheni landslide complex on the hikurangi margin of new zealand remobilisation has formed boundary shear zones imaged at the seafloor surface in multibeam data and at depth in multichannel seismic reflection data a significant amount of internal deformation has occurred within the debris streams phases of deformation appear to be partitioned longitudinally as extensional and contractional zones rooted into a basal decollement and laterally with strike slip shears partitioning discrete debris streams while slow moving terrestrial earthflows are activated by fluctuating piezometric levels typically controlled by precipitation different processes cause the equivalent mobility in a submarine earthflow elevated pore pressures in submarine earthflows are produced by processes such as earthquake generated strong ground motion and or gas fluid release earthflow movement in submarine settings is prolonged by slow dissipation in pore pressure

detection of seismic anisotropy using ocean bottom seismometers a case study from the northern headwall of the storegga slide summary azimuthal seismic anisotropy has been identified from the analysis of s waves generated by p to s mode conversion in the pleistocene sediments that form the northern headwall of the storegga slide which were investigated with a seismic experiment employing a seabed array of ocean bottom seismometers and a grid of airgun shots the principal technique used to detect the anisotropy was azimuthal stacking of the radial and transverse horizontal geophone components after the application of moveout to show the variations in amplitude phase and cumulative traveltime effects of s waves ultimately providing information that identified the fast and slow s wave polarization orientations particle motion analysis was used to corroborate the results and provide further information on the magnitudes of cumulative s wave splitting a 2 d ray traced inversion of the traveltimes of pre critical p and ps arrivals provided a velocity model from which the variation with depth of vp vs and anisotropy could be compared with lithological and stratigraphic data from a borehole at the centre of the obs array increased anisotropic response was observed to be coincident with high velocity units which have high mica but low water content and are interpreted to be of glacial origin the analysis of azimuthal seismic anisotropy shows clear evidence for horizontal transverse isotropy or an orthorhombic symmetry the distribution in orientations of the fast plane of symmetry is broadly bimodal e w and ne sw across the obs array the e w group showed correlation with the headwalls of old buried slides and other faults visible within coherency attributes calculated from an accompanying 3 d seismic data set and with the strike of some of the headwalls of slides shown in multibeam bathymetry however the pattern of headwall fractures shown in the bathymetry is complicated and reticulate and the ne sw orientation is also well represented we infer that the cause of the anisotropy is the presence of vertical to sub vertical fluid filled fractures and micro cracks partially held open by high pore fluid pressure the fracture orientations are controlled primarily by the present day gravitationally induced down slope stress which is mediated by the heterogeneous nature of sub surface causing local changes in the orientation of the principal stresses at the margins of incipient or failed slides the fractures if connected are likely to increase vertical permeability within the sediment column significantly and influence the distribution of gas hydrate within the strata

long term in situ observations at the athina mud volcano eastern mediterranean taking the pulse of mud volcanism abstract long term monitoring on mud volcanoes is fundamental to unravel episodic processes and transient changes that might otherwise be missed by using snapshot observations during time limited research expeditions we deployed a pore and seafloor pressure observatory close to the main conduit of the athina mud volcano south of turkey eastern mediterranean sea for a period of 26 months between february 2014 and april 2016 the observatory recorded 32 pore pressure transients related to as many seismic events out of 625 earthquakes with mw 2 5 occurred over the monitoring period in a radius of 1000 km and few pore pressure excursions related to mud volcanism the data helped to define a threshold for earthquake triggered changes in mud volcano pore pressure thus delineating possible pore pressure distance relationships for different magnitudes ranges peak ground accelerations as representative for earthquakes ground motion at the observatory have been calculated with different ground motion prediction equations using a conservative approach an empirical equation has been identified which specify the lowermost pga necessary to induce a change in pore pressure record at the athina mud volcano moreover internal variations of the mud volcano system recordable through the pore pressure signal have been described for the first time in such a submarine feature

horizontal stress anisotropy and effective stress as regulator of coal seam gas zonation in the sydney basin australia abstract coal seam gas zonation in the sydney basin nsw australia is related to basin hydrodynamics and hydrochemical facies evolution along the flow path from the subcrop to the basin center biogenic methane corresponds with meteoric water under hydrostatic pressure and persists down to the top of the geopressured zone 800 to 1000 m thermogenic gases including wet hydrocarbons can reach up to relatively shallow horizons of less than 500 600 m depth in the transition zone between the top of the geopressured and base of the hydrostatic zone a mixed water and gas regime prevails comprising brackish waters and gases of mixed biogenic thermogenic and inorganic origins including co 2 mechanisms for and the role of stress in the development of this layered hydrogeological and gas environment are investigated in this paper the inverse relationship between effective horizontal stress and permeability in coals through regulation of cleat volumes is well documented and there is evidence of regionally compartmentalized stress regimes with depth within the sydney and other eastern australian coal basins this regional stress regime can be overprinted by the effect of localized geological features it is hypothesized that the in situ stress regime plays an important role in the regulation of groundwater flow regimes and extents resulting in the development of the reported gas content and compositional zonation analysis of regional gas and stress data obtained from public and private databases as well as literature supports this hypothesis changes in gas concentration and composition with depth correspond with discernable variations in horizontal stress anisotropy gas contents generally increase with depth down to a peak gas horizon below which concentrations decrease this peak gas zone is coincident with a horizontal stress anisotropy change from moderately high to low levels associated with reverse to strike slip faulting conditions respectively the stress release zone also marks the top of the thermogenic gas zone identified by the first appearance of ethane in the vertical profile this zone also hosts gases of mixed origins biogenic thermogenic and inorganic co 2 and represents a mixed transitional groundwater flow environment the base of the mixed gas zone is the top of the geopressured only flow associated with thermogenic gases and is signaled by the return to high stress reverse faulting conditions below 850 900 m depth in the sydney basin

the pleistocene to recent geological development of the ormen lange area a large volume of geological geophysical and geotechnical data have been acquired over the last decade in order to perform a safe development of the ormen lange gas field which is located in the scar of the holocene storegga slide the last in a series of large slides in this region over the last 500 ky based on high resolution seismic data and a series of geotechnical borings a unified pleistocene stratigraphy has been established for the area two main modes of deposition prevailed in the pleistocene during periods of peak glaciation when glaciers extended to the shelf break basal tills were deposited on the shelf and glacial debris flows on the continental slope during the much longer periods of reduced ice cover including interglacial periods normal marine and distal glacial marine deposition prevailed partly developed as contourites on the slope the resulting two sediment types are unsorted glacial diamictons and fine grained partly laminated sediments respectively these display distinctly different sedimentological and geotechnical properties and the failure planes for all the major slides are found in the fine grained marine deposits

controls on low pressure anatexis low pressure anatexis whereby rocks melt in place after passing through the andalusite stability field develops under more restricted conditions than does low pressure metamorphism our thermal modelling and review of published work indicate that the following mechanisms operating alone may induce anatexis in typical pelitic rocks without inducing wholesale melting in the lower crust i magmatic advection by pervasive flow ii crustal scale detachment faulting and iii the presence of a high heat producing layer of these only magmatic advection by pervasive flow and crustal scale detachment faulting have been shown quantitatively to provide sufficient heat to cause widespread melting combinations of the above mechanisms with pluton scale magmatic advection shear heating removal of the lithospheric mantle or with each other provide additional means of developing suitable high temperatures at shallow crustal levels to generate low pressure anatexis

the phillips pluton maine usa evidence of heterogeneous crustal sources and implications for granite ascent and emplacement mechanisms in convergent orogens the phillips pluton age of 403 8 1 3 ma was assembled at a crustal level below the contemporary brittle plastic transition during regional dextral reverse transpressive deformation the pluton is composed dominantly of medium to coarse grained leucogranite sensu lato s l but within its bounds includes decametric massive outcrop of fine to medium grained granodiorite s l in places the leucogranite contains centimetric enclaves apparently of the granodiorite granodiorite is host to more biotite than muscovite and more calcic oscillatory zoned plagioclase compared to the leucogranite pegmatitic granite and composite pegmatite aplite occur as metric sheets within the pluton and as larger bodies outside the pluton to the sw magmatic fabrics defined by biotite schlieren occur locally in the leucogranite the attitude of these fabrics and layering within the leucogranite are concordant with the ne striking steeply dipping country rock foliation k2o contents rb sr ratios rb sr and ba covariations and chondrite normalized rare earth element ree patterns of leucogranite are consistent with high to moderate a h2o muscovite dehydration equilibrium eutectic melting of a predominantly pelite source similar to metasedimentary rocks of the surrounding central maine belt cmb the ree patterns and rb sr ratios of granodiorite also suggest derivation from a metasedimentary source but more likely by moderate to low a h2o muscovite biotite dehydration equilibrium eutectic to non eutectic minimum melting of a protolith dominated by greywacke in which garnet and plagioclase were residual phases both granite s l types have heterogeneous initial nd isotope compositions samples of granodiorite define a range in end 404 ma of 1 8 to 0 1 0 3 2 uncertainty and samples of leucogranite define a range in end 404 ma of 8 0 to 5 3 0 3 2 uncertainty this bimodal distribution suggests that melts were derived from a minimum of two sources the data are consistent with these sources being cmb metasedimentary rocks end 404 ma 4 for the granodiorite the range of nd isotope compositions within each granite type most likely reflects isotopic heterogeneity inherited from the source these data imply that the integrity of individual melt batches was maintained during ascent and that extensive mixing of melt batches during emplacement at this level in the pluton did not occur although centimetric enclaves have intermediate nd isotope compositions consistent with small scale interactions between magmas we infer that the phillips pluton represents the root of a larger pluton and that what remains of this larger pluton is the feeder constructed from multiple melt batches arrested during waning flow of granite magma through a crustal scale shear zone system

contourites and their relevance for mass wasting along the mid norwegian margin between about 12 and 4 3 ma slope parallel bottom currents dominated the neogene sedimentation on the slope of the mid norwegian margin and large scale sediment bodies accumulated to thicknesses up to 1000 m these bedforms are morphologically classified as sheeted and elongated mounded contourite drifts an increase in sediment supply from about 4 to 3 ma due to onshore uplift and glaciation resulted in a massive influx of downslope derived material onto the continental margin only on the voring plateau was contourite sedimentation little affected by this change in sedimentary style during the last 0 5 my contouritic deposits occurred also in the storegga area as 100 150 m thick infill drifts inside the scars of two palaeo slides r and s holocene post slide deposits in the scar of the storegga slide 8 2 ka have the typical morphological features and distribution of contourite drifts with the upslope limit at the lower base of the warm northward flowing north atlantic current at 500 700 m depth and the downslope limit at depths of approximately 1200 m detailed chronostratigraphy of the post slide sediments show relatively constant high sedimentation rates in the order of 1 2 m ky during the last 8000 years this is equivalent to the estimated rates for the older infill drifts the infill drifts consist mainly of clays with silty and sandy lamina and represents marine and glaciomarine conditions the main influence of contourite drifts on slope stability relates to their physical properties forming a more sensitive and brittle deposit than the glacial deposits and their exposure to downslope sedimentation in addition the potential for build up of excess pore pressure due to rapid loading from subsequent glacial depositions their seabed smoothing effect and great lateral extent make the contourite drift deposits particularly important for slope instability in this region