toward a global model for correction of bottomhole temperature data progress and limitations static formation temperature sft can be estimated from temperatures measured during wire line logging tm a large number of correction models for obtaining sft from tm have been suggested several studies have shown that sfts yielded by such models are off by an average of 6 c 10 c 43 f 50 f at burial depths of 1 5 3 5 km 0 9 2 2 mi and thus have the potential to cause serious issues in thermal and hydrocarbon generation models this paper explores the causes for erroneous sft predictions generated from tm measurements and identifies factors that should be addressed to generate a globally applicable correction model we also present an improved empirical correction model for tm data from eight oil and gas fields located on the norwegian continental shelf the new empirical model was designed to give correct average sft predictions and is applicable to single tm measurements it has been validated against temperatures recorded during drill stem testing which closely represent local sfts the expression yields improved results compared with other correction models applied to the data set however the average error in computed sft values varies by up to 10 c 18 f between the investigated hydrocarbon fields we conclude that these variations result from differences in operational practices such as fluid circulation and drilling velocities therefore current empirical and physical models for sft prediction from tm require local calibration it is also suggested that more accurate compilations and analyses of operational data could lead to improved and more globally applicable models

glaciological studies on nelson island south shetland islands antarctica the ice cap on nelson island in the south shetland islands west antarctica was studied between 1985 and 1989 the ice cap has an average thickness of 120 m it is temperate exists under the sub antarctic maritime climate and almost completely covers the island owing to intense percolation of meltwater and to some extent liquid precipitation the snow firn layer is in the soaked facies with a firn ice transition at a depth of 25 26 m at the summit a force balance model suggests that the ice is almost linearly viscous but has a high viscosity the model further suggests that basal sliding makes a larger contribution to the ice movement than does ice deformation from 1970 to 1988 the average accumulation rate was 120 kg m 2 a 1 at the centre and between 1985 and 1989 the equilibrium line elevation averaged 110 m a s l analysis of chemical impurities in the surface snow suggests that the precipitation source is mainly local marine air masses and that human activity has already exerted a detectable influence on the local environment

the southern caspian a compressional depression floored by a trapped modified oceanic crust the south caspian intracontinental depression floored by oceanic basement is a relatively stable block with minor deformation surrounded by active fold thrust belts of arcuate form talesh alborz and kopeh dagh mountains which have undergone intense late cainozoic crustal shortening the basin is interpreted as a neogene quaternary compressional depression bounded by multi role mountain bordering reverse faults and apparently floored by a late paleozoic triassic or late mesozoic early tertiary modified oceanic crust trapped along an old geosuture it may be a relic of an old paleozoic triassic ocean or else a marginal sea developed behind a mesozoic paleogene ocean and analysis of geological and geophysical data enables a scheme to be suggested the general arcuate shape of the alborz and the talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south caspian depression a tectono sedimentary study of the south caspian region coupled w

late cenozoic geological development of the south voring margin mid norway abstract late cenozoic seismic stratigraphy of the voring continental margin has been studied in detail with emphasis on the geological development of the naust formation deposited during the last 3 million years the kai formation 15 3 ma comprises mainly biogenic ooze deposited in the more and voring basins in naust time there was a marked increase in supply of sediments from the inner shelf areas and the western part of the scandinavian mountain range and glaciers expanded to the shelf and reached the shelf edge several times during the last 1 5 2 million years during early to mid naust time the shelf was widened by westerly prograding sediment units but for a long period the shallowest part of the helland hansen arch hha formed a barrier preventing glacially derived debris from being distributed farther west west of the hha mainly stratified marine and glacimarine sediments were deposited a substantial part of these sediments were transported by the north flowing norwegian atlantic current which redistributed suspended particles from ice streams rivers coastal erosion and seabed winnowing after burial of the crest of the hha at c 0 5 ma glacial debris and slide deposits were also deposited west of this high in the north massive units of glacial debris were distributed beyond the crest of the hha also in mid naust time thinning westwards and interfingering with fine grained sediments on the lower slope the sklinnadjupet slide inferred to be c 250 000 years old corresponds in age with an earlier huge slide in the storegga area an elongated area of uneven seabed topography previously interpreted as diapirs vigrid diapirs on the slope west of the hha is shown to be formed by ooze eruption from the crest of the arch and submarine sliding

spatial variability of antarctic peninsula net surface mass balance 1 measurements from ice cores and snow pits collected over the last 50 years are used to examine how net surface mass balance varies across the antarctic peninsula to give the first detailed map of mass balance for the region a total of 211 reliable mass balance measurements were available for the preparation of the map but some areas were found to be very data sparse the analysis suggests that the largest values of mass balance are found along the spine of the northern part of the peninsula where over 2 5 m yr 1 water equivalent we has been measured a secondary peak of more than 2 0 m yr 1 we is determined along the mountains of eastern alexander island precipitation minus evaporation p e fields from the european centre for medium range weather forecasts reanalysis project are compared with our analysis of in situ data the model fields are found to have peak values of p e of only half the amounts found from the measurements the greatest model values are located on the western side of the peninsula areas where a high density of in situ data is available including king george vi sound and the high south central plateau part of the peninsula show a high spatial variability of net surface mass balance suggesting that local orographic features play a major part in dictating the mass balance

investigations of the oxygen 18 content of samples from snow pits and ice cores from the filchner ronne ice shelves and ekstrom ice shelf

the free gas zone beneath gas hydrate bearing sediments and its link to fluid flow 3 d seismic imaging offshore mid norway abstract hydrate recycling and vertical migration of fluids from deep sources are processes evoked as controllers of the formation and stability of the free gas zone fgz beneath the base of the gas hydrate stability zone bghsz these processes have been often investigated through analytical and numerical modeling at some locations in continental margins however the seismic response of sediments deformed by such mechanisms has been poorly investigated due to the lack of reliable seismic resolution to clearly image anomalies confined to the fgz the present study is dedicated to the seismic characterization of the fgz beneath the bghsz at a hydrate site offshore mid norway using high resolution p cable 3d seismic data dim amplitude anomalies showing mainly lineations in a polygonal pattern of distribution 50 80 m vertical extension 150 300 m lateral extension and up to a few kilometers long are interpreted as evidence of sediment remobilization possibly aided by hydrate dissociation at focused fluid flow zones below former bases of the ghsz the exclusive occurrence of the anomalies within a depth range comprising estimated paleo bghszs during the last 200 kyr suggests that the anomalies are associated to paleo hydrate bearing sediment seals emplaced at depths controlled by overburden it also supports recently reported indications of main periods of fluid expulsion towards the seafloor occurring between 200 and 130 ka bp

oxygen isotope and total beta radioactivity measurements on 10 m ice cores from the antarctic peninsula as part of the glaciology of the antarctic peninsula gap programme the snow cover at 25 stations was sampled to 10 m depth for oxygen isotope and total radioactivity analysis the mean annual oxygen isotope ratio correlates satisfactorily with 10 m temperature despite the complex topography of the area and suggests on average that climatic trends in the region are fairly systematic the relationship with temperature is similar to that derived from a simple model in which an air mass initially of maritime subtropical characteristics is progressively cooled as it moves towards the region the detailed isotope profiles show that for future deep drilling the most easily interpretable climatic information will be found in the more continental areas on the cast coast and on the plateau in the south of the region the degree of continentality of particular sites is reflected in the amplitude of the annual wave in the upper portion of the isotope ratio profile as well as in the accumulation rate

mud volcanism by repeated roof collapse 3d architecture and evolution of a mud volcano cluster offshore nigeria abstract using 3d seismic data we document the subsurface architecture of a cluster of 3 mud volcanoes located on the upper continental slope offshore nigeria in a background of gently dipping stratified sediments the subsurface of the cluster contains 8 seismic sequences made of one subcircular syncline 1 3 km in diameter and adjoining unstratified units synclines flatten out upward through intercalation of unstratified concave up lenses between stratified units and are eventually filled by a convex up unstratified lens onlapped by background sediments the lower boundary of each sequence is a 0 5 1 5 km deep bowl shaped unconformity across which high dip strata rest above truncated low dip series we interpret each seismic sequence as a mud volcano system mvs sourced from a connected region and evolving through episodes of roof collapse three are associated with the surface mud volcanoes and another 4 to fossil ones mud volcano systems are dynamic features that record the evolution of 1 the material extruded from one single connected source region depletion zone as it grows downwards and stepwise becomes depleted 2 the basal unconformity which joins strata originally separated by material evacuated in the remobilization process by analogy with salt tectonics we propose to call it a mud weld 3 the conduits and 4 the successive collapsed roofs of the depletion zone the evolution of each mud volcano system in this interpretation records progressive growth of the depletion zone by downbuilding punctuated by episodes of roof collapse and extrusion the geometry and evolution of this type of mvs can be interpreted in the light of analogue models of magmatic caldera development in early stages the thin roof experiences downsagging while remobilized material is extruded through an axial pipe like conduit in later stages the thickened roof undergoes piston like subsidence and mud extrusion occurs along the peripheral fault

sefidrud delta and quaternary evolution of the southern caspian lowland iran abstract the southern caspian sea lowland in iran forms a thick sedimentary prism produced by interactions of marine deltaic and fluvial processes during the late neogene and quaternary deltaic and fluvial deposits have been developed mainly by the sefidrud which is the largest river of the country its drainage area ca 61 600 km 2 includes nearly the entire alborz mountain range and forms deep valleys gorges and a large delta at the southern coast of the caspian sea the sefidrud delta is so large that it covers one third of the large guilan mazanderan plain both from an aerial and volumetric point of view consequently the drainage network of the sefidrud represents the quaternary evolution of northern iran and can be used to test the hypothesized evolution of the region the sefidrud delta has been investigated using many short and long cores satellite images and lithofacies maps and the results show that this delta complex 1680 km 3 consists of a covered lower part and exposed upper deltaic sequences the lower and upper parts of the complex were formed during the early pleistocene and late pleistocene respectively the upper exposed alluvial and deltaic sediments represent a total progradation of approximately 50 km forming three separate delta subsequences d1 3 of which the last one d3 is the modern sefidrud delta the modern delta is a wave dominated blanket like sediment cover ca 30 m thick and 1550 km 2 produced during the last three millennia it was formed by 30 km progradation of six juxtaposed lobes each lobe corresponds to a long term sea level fluctuation of the caspian sea the active lobe ca 50 km 2 has been forming since 1550 ad late pleistocene deltaic sequences d1 3 particularly the modern one d3 were produced by relatively fast deposition due to high volume sediment load of the sefidrud it is suggested that they were produced after the opening of the rudbar gorge by river capture that in turn six times enlarged the drainage area previous deltaic progradation and marine transgressions were relatively slow and the development of the whole lowland at the southern caspian sea lasted ca 1 1 2 ma bp

fossilisation of a silica diagenesis reaction front on the mid norwegian margin the diagenetic transformation of biogenic silica from opal a to opal ct was recognised on seismic reflection data over an area of 78 103 km2 on the mid norwegian margin the opal a ct diagenetic boundary appears as a positive high amplitude reflection that generally cross cuts the hosting stratigraphy we demonstrate that it is not a sea bottom simulating reflection bsr and also that is not in thermal equilibrium with the present day isotherms we present arguments that three styles of deformation associated with the opal a ct reflection polygonal faulting regional anticlines and synclines and differential compaction folding indicate that the silica diagenesis reaction front is fossilised at a regional scale isochore maps demonstrate the degree of conformity between the opal a ct reflection and three seismic horizons of late miocene to early pliocene age that potentially represent the paleo seabed when fossilisation of the reaction front took place the seismic interpretational criteria for recognition of a fossilised diagenetic front are evaluated and the results of our study are integrated with previous studies from other basins of the ne atlantic in order to determine if the arrest of silica diagenesis was diachronous along this continental margin

climatically induced retreat and collapse of northern larsen ice shelf antarctic peninsula the areal changes of the northern larsen ite shelf lis antarctic peninsula between march 1986 and march 1997 have been analyzed based on synthetic aperture radar images of the european remote sensing satellites ers 1 and ers 2 and on landsat images this analysis is complemented by data on ice motion and surface mass balance which have been obtained during several field campaigns since the early 1980s after a period of retreat coinciding with atmospheric warming and with decreasing net accumulation at the surface due to melt losses the two northernmost sections of lis disintegrated almost completely within a few days in january 1995 recent observations of the ice shelf section north of jason peninsula which is presently the northernmost section of lis show increased summer melt and intensification of the rifting processes probably causing accelerated retreat of this section in the near future the retreat and the disintegration event of lis indicate high sensitivity of ice shelves to prolonged perturbations of the mass balance

hummock fields in the norway basin and eastern iceland plateau rayleigh taylor instabilities side scan imagery and 3 5 khz profiles in the norway basin reveal 3 4 10 4 km 2 of sea floor covered by regularly spaced 500 2000 m low relief hummocks previously attributed to bottom currents extrapolating from nearby borehole data i attribute these mound fields to gravitational rayleigh taylor instabilities resulting from superposition of 50 100 m of thick pliocene pleistocene glacigenic glacier derived sandy clays density 1800 kg m 3 on a several hundred metre thickness of miocene biosiliceous oozes having a density of 1300 kg m 3 this hypothesis predicts or explains similar hummock fields in many oceanic regions where such density inversions exist

understanding antarctic peninsula precipitation distribution and variability using a numerical weather prediction model daily precipitation fields and annual means from the european centre for medium range weather forecasts re analysis exercise are used to examine the distribution and variability of precipitation across the antarctic peninsula the annual mean precipitation field from the model agrees well with the available ice core data and suggests that the maximum accumulation for the area is on the western side of the barrier at about the 200 m level where the annual total is close to 1 3 m w e the peninsula is shown to be a very effective barrier to the zonal movement of precipitati ng weather systems which results in quite different atmospheric flow regimes being responsible or significant precipitation events on either side of the divide frontal depressions are the primary source of large daily snowfall totals on both sides of the peninsula on the southern coast of the bellingshausen sea major snowfall events are often linked to strong northerly flow when the atmospheric circulation is blocked predominantly northerly flow is also responsible for significant snowfall on the ronne ice shelf which often occurs in association with lee cyclogenesis events to the east of the peninsula

the sklinnadjupet slide and its relation to the elsterian glaciation on the mid norwegian margin abstract the sklinnadjupet slide scar is a large buried feature on the continental slope southeast of the voring plateau the mass flow occurred ca 250 000 years ago on a slope angle of ca 0 5 and removed glacial debris from the up to 350 m thick naust s sequence on the upper slope this part of the mid norwegian margin appears to have been fairly stable throughout the last 2 8 million years naust s represents the third last glacial unit in the skjoldryggen region and was deposited during the elsterian ca 400 200 ka bp during this glaciation a wide depression was formed on the continental shelf between haltenbanken and traenabanken with the strongest glacial erosion in the west trending sklinnadjupet palaeo trough this trough leads directly towards the deep 90 km wide slide scar indicating that a local depocentre was formed here before the mass flow occurred the shallowest crest of the helland hansen arch is located below the southern part of the slide scar and two large craters were formed on the surface of this anticlinal structure our model suggests that the deposition of glacial sediments above the helland hansen arch caused high excess pore pressures along the shallowest crest of this structure and formed a high pore pressure gradient towards the sea floor on its western flank an earthquake possibly triggered the initial slide where the slope was steepest west of the crest most of the slide scar was already formed when the slide finally eroded into the anticline high excess fluid pressure subsequently mobilised the diatomaceous oozes in the helland hansen arch and formed the craters much of this material flowed down slope without being totally disintegrated and was deposited as levee ridges and mounds above slide deposits from the first phase of the mass flow they have previously been wrongly interpreted as diapirs

formation of large crater like evacuation structures in ooze sediments in the norwegian sea possible implications for the development of the storegga slide abstract several crater like structures up to 20 km wide and 300 m deep have been identified by mapping of the top of the oligocene miocene ooze formations in the norwegian sea fig 1 the upper part of the ooze has been evacuated from the structures and emplaced in mounded local accumulations of ooze sediments located stratigraphically above and geographically downslope relative to the evacuated structures the structures are filled in by mass flow deposits belonging to the plio pleistocene naust formation our conceptual model implies that the evacuation structures were triggered by mass flows which loaded ooze sediments at the sea floor or at shallow burial the ooze was evacuated due to its low density which caused it to ascend to the surface of the mass flow

mass wasting processes in the western wilkes land margin possible implications for east antarctic glacial history abstract multichannel seismic data collected off western wilkes land east antarctica reveal widespread sediment mass movement events mainly in the form of mega debris flows deposited on the continental rise in places they have a seaward extent of more than 200 km and a thickness of up to 400 m debris flow units are commonly separated by thin deposits of well stratified facies interpreted as glaciomarine mixed contouritic and distal turbidite deposits possibly with some hemipelagic sediments these units due to a dominant contouritic component represent weakened layers and could then play a major role in the slope instability based on stratigraphic correlation with dsdp site 268 it is suggested that slope failures in the western wilkes land occurred mostly during the miocene inferred high sedimentation rates due to large amounts of sediment delivered from a temperate wet based ice sheet would have constituted a key factor in the sediment failures the distribution of mass wasting related features appears also strongly related to the amount of meltwater discharge the main trigger mechanism would probably have been earthquakes enhanced by isostatic rebounds following major ice sheet retreats

stratigraphic development of the south voring margin mid norway since early cenozoic time and its influence on subsurface fluid flow abstract the cenozoic seismic stratigraphy and geological development of the south voring margin are analyzed to understand their relation to fluid flow and margin stability the regional stratigraphy and palaeomorphology of the more and voring basins indicate gradual changes in depositional environment and tectonic compression between 55 ma to 2 8 ma during brygge and kai periods and abrupt changes associated with glacial interglacial cycles from last 2 8 ma during naust period these changes resulted in deposition of various types of sediments and led to processes such as polygonal faulting and dewatering inter fingering of contouritic stratified and glacigenic sediments and margin progradation a gas hydrate related bottom simulating reflector bsr occurs at nyegga and within the central voring basin while pockmarks are observed at nyegga only diagentic reflectors due to opal a opal ct conversion dbsrs occur along a wider area beyond the shelf edge the dbsrs are located in oozes within the kai and late brygge formations the gas hydrate bsr occurrence is concentrated above eocene depocenters in hemipelagic and contouritic sediments deposited during late plio pleistocene the bsr overlies polygonal faults and dbsrs but are confined to the slope of anticlines indicating its formation being related to fluid pathways from methanogenic rocks through focused fluid flow microbial gas production in kai brygge and deeper formations may have supplied the gas for gas hydrate formation fluid expulsion due to dbsr formation and polygonal faulting in oozes may have created overpressure development in permeable layers belonging to the overlying naust formation slide headwalls are also located close to the anticlines in the study area implying that over pressured oozes and focussed fluid flow may have been important in creating weak surfaces in the overlying naust sediments promoting conditions for failures to occur

a climatology of southern hemisphere extratropical cyclones a climatology of extratropical cyclones determined by an objective automatic scheme applied to 15 years 1975 89 of once daily australian bureau of meteorology hemispheric analyses is presented contour maps of the positions of formation cyclogenesis dissipation cyclolysis together with other cyclone statistics are presented the distribution of cyclones through the hemisphere was found to be dominated by a permanent high latitude core coincident with the circumpolar trough during the winter and intermediate seasons two mid latitude branches are evident in the cyclone density originating in the tasman sea and south american sectors both spiraling poleward and merging with the circumpolar core in the southern oceans systems were observed to move in an castsouth east direction away from their location of formation exhibiting peak speeds of migration in the mid latitudes little seasonality was evident in the densitiy distribution of cyclones through the southern oceans but a considerable amount was found in their central pressure

seismic vulnerability caspian sea southern coast seismic vulnerability degree evaluation is the main target in this research through correlation between earthquake focal points and the alignment of all faults using a geographical information system the main active faults were distinguished recognition of the potential for earthquakes with richter magnitude more than 5 seismic vulnerability was recognized combining all data layers the geotechnical hazard potential was computed using a universal ranking system model ursm the main results show that recognition of active faults can improve seismic vulnerability degree and geotechnical instability assessment in this region

glaciological and oceanographic calculations of the mass balance and oxygen isotope ratio of a melting ice shelf on a etudie l alimentation du george vi ice shelf en relation avec l accumulation le velage et la fonte on releve la relation temperature taux d isotope de l oxygene ces donnees sont couplees a des donnees oceanologiques sur les eaux chaudes et son interaction avec le shelf

diatom ooze crucial for the generation of submarine mega slides numerous studies invoke weak layers to explain the occurrence of submarine mega slides 100 km3 in particular those on very gentle slopes 3 failure conditions are thought to be met only within this layer which is embedded between stable sediments although key to understanding failure mechanisms little is known about the nature and composition of such weak layers mainly because they are destroyed with the landslides this study is the first to place detailed constraints on the weak layer for one of the submarine mega slides that occurred on the nearly flat subtropical northwest african continental slopes integrating results from the ocean drilling program with high resolution seismic reflection data we show that the failure surfaces traced into the undisturbed sedimentary sequence coincide with thin 10 m diatom ooze layers capped by clay as diatom oozes are common on many continental margins we suggest a new margin independent failure mechanism to explain submarine mega slides at low gradient continental slopes globally diatom oozes are susceptible to building up excess pore fluid during burial due to their high compressibility and water content if a low permeable clay cap prevents upward drainage excess pore pressures accumulate at the ooze clay interface causing the shearing resistance to increase at a lower rate than the shear stress until failure can occur changes in global climate affect the abundance of diatoms and thus formation of diatom oozes thereby preconditioning the sediments for failure however the actual timing of failure is independent of environmental changes

surface lowering of the ice ramp at rothera point antarctic peninsula in response to regional climate change level line surveys at a number of sites on the antarctic peninsula since the early 1970s have shown a lowering of the ice surface elevation in areas where the climate is warm enough for melting to occur during summer results are presented here from annual surveys on the ice ramp at rothera point over an 8 year period a large proportion of the ramp shows a generally steady reduction in surface elevation the uppermost part of the ramp shows no clear trend the ice ramp has suffered a mean rate of surface lowering of 0 32 m a i w e over the period of the surveys which is similar to that seen at other sites on the antarctic peninsula measured ice velocities on the ramp are low so the surface lowering can be attributed directly to changes in surface mass balance the surveys coincide with a period of long term increase in temperature and ablation seen in meteorological records comparison of the observed surface lowering with temperature data shows a good agreement and we conclude that increasing air temperatures in the region will raise ablation and increase the recession rate of the ice ramp

reconstruction of glaciation over the past 6 myr from ice borne deposits in the norwegian sea it is well known that a significant intensification of northern hemisphere glaciation occurred 2 5 myr ago in contrast to the much earlier onset 35 myr of glaciation in antarctica1 3 much less is known about the behaviour of the climate before 2 5 myr and it has remained unclear when sizeable glaciers first started to develop in the northern hemisphere here we deduce the history of high northern latitude glaciation over the past 6 myr from records of ice borne deposits in deep sea sediments of the norwegian sea we find that glaciers large enough to reach sea level were present in the norwegian sea area as early as 5 5 myr three million years before the intensification of glaciation at 2 5 myr fluctuations in ice volume can be deduced from the oxygen isotope record but this provides only a global average which may not reflect the history of ice sheet growth in specific regions from a comparison of the oxygen isotope records with the record of ice rafted material we derive an estimate of the relative contributions of southern and northern hemisphere glaciation to global variations in ice volume

resolution limits of fluid overpressures from mineralogy porosity and sonic velocity variations in north sea mudrocks pore pressure identification in mudrocks largely relies on indirect methods including analyses of sonic velocity data the magnitude of pore pressure changes that can be resolved from such data depends on the impact of fluid pressures on well log responses and on the velocity responses to lithological variations that could be mistaken for indications of pore pressure changes analysis of relationships between sonic velocity mineralogy and porosity from 11 north sea wells demonstrated porosity variations of up to 5 from the mean value in mudrocks at any given depth between 1 and 3 5 km 3300 11 500 ft comparisons of these wells with seven wells from the norwegian sea demonstrated that the sonic velocity and density variations are influenced by the content of silica with a biogenic origin but that they can otherwise not in general be related to mineralogy and pore pressure variations the sonic velocity deviations from the mean value are of the same magnitude as those that would be caused by porosity changes of 8 in mudrocks of uniform lithology furthermore the deviations are not significantly reduced when the velocity data are compensated for changes in density porosity detection limits for mechanically compacting mudrocks that are at their maximum effective stress are equivalent to static mud density changes of 0 1 0 15 g cm3 these numbers apply to mudrocks with similar lithological variability to those analyzed in our data set but should be much higher when significant amounts of silica with a biogenic origin are present the impact of effective stress changes on the sonic velocities of chemically compacting as well as of mechanically unloading rocks is much less because small or no porosity changes follow from the effective stress changes in such cases the velocity responses for mechanically unloading and stress insensitive chemical compaction can only be identified from four dimensional time lapse seismic data unless the rocks are close to the fracturing limit these observations imply that reasonably accurate velocity based pore pressure identification in north sea mudrocks requires a knowledge of local mudrock heterogeneity and compaction that cannot easily be obtained as a result sonic velocity data should be treated with considerable caution in pore pressure evaluation

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

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

heat flow measurements in late palaeoproterozoic to permian geological provinces in south and central norway and a new heat flow map of fennoscandia and the norwegian greenland sea abstract new heat flow determinations from 9 sites in south and central norway situated in late palaeoproterozoic to permian geological provinces show that topographically and palaeoclimatically corrected surface heat flow generally varies between 50 and 60 mw m 2 the palaeoclimatic corrections are significant typically constituting 10 20 of the final heat flow values higher heat flow was encountered at 3 sites however only at the fredrikstad site situated in the high heat producing iddefjord granite could this elevated heat flow be related to high heat production a compilation of new and previously published heat flow data from norway show that on the scale of major geological provinces heat flow varies significantly and is generally overlapping the lowest heat flow values ca 30 mw m 2 come from the early palaeoproterozoic karasjok kautokeino greenstone belt and the early neoproterozoic egersund anorthosite complex both of which are dominated by low heat producing rocks the highest heat flow values ca 60 80 mw m 2 come from early neoproterozoic high heat producing post orogenic granites in south norway these geological provinces display relatively little variation in lithology and heat production which allows such relationships to be made in general however significant lithological variation within geological provinces makes relationships between heat flow and geological factors such as tectonometamorphic age lithology and heat production on a country scale obscure at best in contrast a compilation of almost 1000 heat flow measurements from fennoscandia and the norwegian greenland sea shows a distinct correlation between heat flow and tectonic age the archaean provinces in ne fennoscandia karelia display low heat flow of ca 35 40 mw m 2 increasing gradually to ca 50 55 mw m 2 southwestwards in palaeoproterozoic and mesoproterozoic provinces the transscandinavian igneous belt which consists largely of relatively high heat producing granites breaks this trend with a heat flow of ca 60 65 mw m 2 on the norwegian continental margin the heat flow is rather constant at ca 60 mw m 2 and the oceanic crust shows an exponential increase in heat flow from ca 60 mw m 2 near the continent ocean boundary oceanic crust ca 55 million years old to 200 mw m 2 near the mid atlantic spreading ridge similar to heat flow determined from oceanic crust elsewhere as well as to theoretical models of oceanic heat flow although a number of factors may render individual heat flow measurements uncertain the abundance of available data obtained by different methods and the clear correlation between heat flow and geology provide confidence as to the significance of these heat flow values