structural development of the fennoscandian border zone offshore denmark abstract the hans 1 saeby 1 and terne 1 wells are located within the danish part of the fennoscandian border zone and provide significant new data pertaining to the evolution of this important tectonic belt all three wells encountered palaeozoic and mesozoic rocks the cambrian to lower silurian deposits can be closely correlated to sections known from bornholm and scania and tectonic activity within the fennoscandian border zone cannot be verified during this time interval the thick upper silurian shales were probably deposited in a rapidly subsiding foreland basin marginal to the speculative caledonian deformation front which lies south of the ringkobing fyn high a major hiatus comprises the devonian and early carboniferous upper carboniferous sediments were deposited before a phase of rifting upper carboniferous intrusive and extrusive volcanic rocks suggest tectonic activities heralding the rifting phase extensive block faulting occurred in the border zone during the rotliegende and more than 650 m of reworked volcanic rocks were deposited in an alluvial fan environment syndepositional erosion created a major unconformity before the deposition of post rift zechstein sediments during the mesozoic the fennoscandian border zone was divided into two zones the sorgenfrei tornquist zone to the west and the skagerrak kattegat platform to the east the sorgenfrei tornquist zone continued to experience tectonic activity in triassic and middle jurassic times the zone has experienced an uplift of 1700 2000 m during late cretaceous to early tertiary inversion tectonics and the late tertiary uplift of fennoscandia

sveconorwegian igneous complexes beneath the norwegian danish basin abstract gravity and magnetic anomalies have previously been interpreted to indicate strongly magnetic permian or even tertiary intrusive bodies beneath the skagerrak waterway such as the skagerrak volcano and beneath silkeborg in denmark our combined modelling of the magnetic and gravity anomalies over these rock bodies indicates that a steep upward magnetisation is required to explain the magnetic anomalies at the surface reminiscent of the magnetic direction in the sveconorwegian rocks of the rogaland igneous province in southern norway the younger rocks of the permian oslo rift region have intermediate and flat magnetisation that is inadequate to explain the observed magnetic field the positive part of the skagerrak aeromagnetic anomaly is continuous with the induced anomalies associated with the eastward extension of the rogaland igneous province this relation also suggests that rocks of the rogaland igneous province and its offshore extension are responsible for the skagerrak anomalies both the negative remanence dominated aeromagnetic anomaly and the positive gravity anomaly can be modelled using constraints from seismic reflection lines and available density data and rock magnetic properties a 7 km thick complex of ultramafic mafic intrusions is located below a southward dipping 1 4 km thick section of mesozoic sediments and 1 2 km of palaeozoic sediments the enormous body of dense ultramafic mafic rocks implied by the modelling could be the residue of the parental magma that produced the voluminous rogaland anorthosites the application of similar petrophysical properties in the forward modelling of the silkeborg source body provides an improved explanation of the observed gravity and magnetic anomalies compared with earlier studies the new model is constrained by magnetic depth estimates from the located euler method ranging between 6 and 8 km forward modelling shows that a model with a reverse magnetic body anorthosite situated above a dense mafic ultramafic body may account for the silkeborg anomalies the anorthosites may have formed by differentiation of the underlying mafic intrusion similar to the intrusive relations in the rogaland igneous province we conclude that there is strong evidence for a sveconorwegian age for both the skagerrak and the silkeborg anomalous rock bodies

a storm surge prediction model for the northern bay of bengal with application to the cyclone disaster in april 1991 abstract a numerical model for simulating and predicting tides and storm surges in regions that include areas of open sea combined with estuarine channels and intertidal banks is described the model makes use of modified depth averaged equations with a numerical scheme in which the solution of 1d equations for narrow channels 2d equations for the open sea and an approach to modeling inundation are combined within a unified framework this simplifies the construction of realistic models for complex coastal areas and deltas the model is applied to the northern shelf of the bay of bengal and the ganges delta including the coast of bangladesh devastated by a cyclone surge in april 1991 in which about 140 000 people died hindcast and forecast simulations of this event using forcing derived from a semianalytical cyclone model with data supplied by the joint typhoon warning center jtwc are described it is shown that the timing of cyclone landfall and its coincidence with high tide determine the area

detailed stratigraphic subdivision and regional correlation of the southern danish triassic succession this paper provides a regional log based lithostratigraphic correlation of the danish triassic deposits with deposits known from the southern north sea basin including the northwest german and dutch onshore areas a new lithostratigraphic nomenclature mainly adapted from the dutch nomenclature is suggested for the danish area south of the ringkobing fyn high replacing the previously used nomenclature the new nomenclature comprises the lower triassic bunter shale and bunter sandstone formations the lower to middle triassic rot and muschelkalk formations and the uppermost middle triassic and upper triassic keuper and sleen formations in total 22 members are also defined from the southern north sea into the southern danish area this main marine southern facies province is separated from a continental northern facies province by the northern flank of the ringkobing fyn high trend units of the southern province only crossed the central and western part of the ringkobing fyn high during the rot and the muschelkalk transgressions whereas the basin north of the eastern part of the high was influenced by the southern facies province during the early to early late triassic

quantitative provenance analysis of sediments review and outlook provenance analysis of sediments is aimed at reconstructing the parent rock assemblages of sediments and the climaticphysiographic conditions under which sediments formed inferring sediment provenance from the final product a basin fill is anything but straightforward because the detrital spectrum evolves as the sediment is transported along the pathway from source to basin successful provenance analysis requires that the nature and extent of compositional and textural modifications to the detrital spectrum be recognised if not quantified the history of quantification in sediment provenance studies is summarised and illustrated by tracking two fundamental ideas the concept of the sediment petrological province or petrofacies and the relation between sandstone composition and plate tectonic environment progress in sedimentary provenance analysis has been closely linked with advancements in measurement technology a brief survey of modern data acquisition tools illustrates the possibilities and limitations of modern provenance research an operational definition of quantitative provenance analysis qpa is presented in which the central role of mass balance is acknowledged extension of this definition to include quantitative predictions obtained by forward modelling computer simulation of sediment production as well as methodological improvements in data acquisition and processing is needed to cover likely future developments in qpa the contributions to the special issue quantitative provenance analysis of sediments illustrate the intrinsic multidisciplinarity and rapid expansion of qpa d 2004 elsevier b v all rights reserved

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

ancient ephemeral stream deposits a local terminal fan model from the bunter sandstone formation l triassic in the tonder 3 4 and 5 wells denmark

relief and saprolites through time on the baltic shield abstract the relief of basement rocks in high latitudes has most often been interpreted as the result of glacial erosion although over large areas its character of exhumed paleoplains has been known for a long time the relief in the precambrian basement of sweden has therefore been analysed in relation to remnants of late proterozoic and phanerozoic cover rocks most of the shield was exposed in the late proterozoic the end result was an extremely flat surface the primary peneplain it was covered by palaeozoic rocks which preserved this surface until re exposure as a sub cambrian surface it makes up the present scenery in large parts of eastern and central sweden the south swedish dome is a key area for the geomorphic analysis of the shield as it has palaeozoic cover rocks on its northern and eastern slopes and mesozoic rocks on its southern and western ones based on the experience from this area classification of the relief in the whole country and experiences from the tropics on relief evolution two theoretical schemes were constructed for a discussion of the relief differentiation the analysis of the relationship between relief saprolite and cover rocks through time led to the conclusion that the most important factor for the present relief differentiation is the time of exposure of the basement surface during the phanerozoic this has important applications for the evaluation of phanerozoic crustal movements as well as implications for the assessment of glacial erosion the approach is thought to be most valuable for comparative studies of shield geomorphology in general and with the laurentian shield in particular

paleozoic paleo cover of the southern part of the fennoscandian shield fission track constraints abstract granitic intrusions older than 1200 ma from an area west of lake vanern south sweden show fission track ages of 680 50 ma 2 late precambrian for sphene and 220 10 ma late triassic for apatite the samples were taken at the present post glacial erosion surface which is close to the sub cambrian peneplain the c 680 ma sphene fission track ages are thought to be related to the uplift of the area which led to the establishment of this erosion surface at c 600 ma ago the much younger apatite fission track ages and the confined spontaneous track length distributions along with regional stratigraphic constraints suggest that the basement was subsequently buried under 3 4 km of paleozoic supracrustals this induced in the basement a rise in temperature which obliterated the older apatite fission tracks but not those in sphene which has a higher closure temperature at the beginning of the mesozoic the area was uplifted again the cover rocks were removed and the basement rocks cooled slowly below the temperature range of fission track annealing in apatite

late triassic structural evolution of the southern margin of the ringkobing fyn high denmark a late triassic carnian unconformity is observed on seismic sections and in wells along the southern margin of the ringkobing fyn high the unconformity is characterised by low angle erosion on the central parts of the eastern ringkobing fyn high mon high and by a significant onlap onto the unconformity surface structural reconstruction shows that the unconformity is related to differential subsidence between the ringkobing fyn high and the north german basin the differential subsidence initiated movements in the mobile zechstein salt causing deformation of the cover sediments the variability in differential subsidence observed during the triassic along the southern margin of the ringkobing fyn high is interpreted to reflect the subdivision of the ringkobing fyn high into a number of structure blocks

partial recovery of the arctic ocean halocline 1 the evolution during the 1990 s of the cold halocline layer chl of the arctic ocean is investigated using data from icebreaker and scicex submarine cruises the chl disappearance and subsequent partial recovery is described along repeated transects through the central arctic ocean from the alpha ridge to the nansen basin salinity at the top of the halocline is used as a measure of halocline development with high salinity corresponding to a poorly developed halocline in the nansen amundsen and makarov basins upper ocean salinity increased from 1991 to 1998 as the chl disappeared then decreased from 1998 to 2000 as it recovered salinity was higher over the study region through the 1990 s than at any time during the prior 40 year period hence the 1990 s chl recovery was only partial disappearance of the chl from the eurasian basin in the early 1990 s was due to a shift from the laptev to east siberian seas of the region for seaward flow of low salinity siberian shelf waters ice velocities and sea level pressure fields suggest that the reappearance of the chl in 1999 corresponded to a shift of this flow back to the laptev sea region

desert sand plain and sabkha deposits from the bunter sandstone formation l triassic at the northern margin of the german basin facies studies of well cores from the bunter sandstone formation in the tonder area denmark indicate that the formation is composed of two desert sand plain sequences associated with sabkha and inland basin lake mudstones the lower desert sand plain sequence consists of subaerial sand flat deposits overlain by aeolian sand sheet and dune facies topped by interbedded aeolian and ephemeral river deposits the upper desert sand plain sequence consists of ephemeral river deposits partly interbedded with and overlain by sabkha and inland basin mudstones two shoreline sandstones occur in the uppermost part both sequences are interpreted mainly in terms of tectonic subsidence of the basin and related upheavals of the source regions the lower sequence represents a rather continuous progradation of the desert sand plain followed by a rapid transgression of the waters from the inland basin the upper sequence represents brief periods of fluvial progradation followed by a gradual retreat of the river plain the most distal part of the sand plain was finally reworked by weak wave action

rapid freshening of antarctic bottom water formed in the indian and pacific oceans 1 repeat hydrographic sections occupied in 1995 and 2005 reveal a rapid decline in the salinity and density of antarctic bottom water throughout the australian antarctic basin the basin wide shift of the deep potential temperature salinity s relationship reflects freshening of both the indian and pacific sources of antarctic bottom water the s curves diverge for waters cooler than 0 1 c corresponding to a layer up to 1000 m thick over the antarctic continental slope and rise changes over the last decade are in the same direction but more rapid than those observed between the late 1960s and the 1990s when combined with recent observations of similar freshening of north atlantic deep water these results demonstrate that dense water formed in both hemispheres is freshening in response to changes in the high latitude freshwater balance and rapidly transmitting the signature of changes in surface climate into the deep ocean

sveconorwegian and caledonian foreland basins in the baltic shield revealed by fission track thermochronology fission track thermochronology has been applied to apatite zircon and titanite from various depths of the baltic shield burial due to sveconorwegian grenville and caledonian foreland sedimentation is revealed titanite and zircon fission track ages from surface samples from eastern sweden do not vary significantly and average 850 myr it is suggested that sveconorwegian sediments reached a thickness of at least 8 km in eastern sweden exhumation of these sediments was succeeded by deposition of lower palaeozoic cover rocks apatite fission track ages along a transect from sw to ne across the shield increase from 300 myr to 900 myr and yield the phanerozoic history of subsidence and exhumation apatite fission tracks in the basement of the thickest parts of the foreland basin were totally annealed these results suggest a 600 km wide caledonian foreland basin filled by devonian sediments that were 2 5 km thick in southern and western sweden thinning to the east in finland

meso cenozoic morphotectonic evolution of southern norway neogene domal uplift inferred from apatite fission track thermochronology apatite fission track aft thermochronology of precambrian and paleozoic basement samples from southern norway reveals a post paleozoic exhumation history related to offshore mesozoic and cenozoic extensional basin development the data indicate two major phases of rapid exhumation a first mesozoic phase started in the triassic 220 ma in the east and south of the study area and migrated to the west where jurassic 160 ma ages of exhumation predominate a second event is indicated by thermal history modeling of aft ages and track length distributions it is inferred to be neogene in age initiated at about 30 ma and it produced a domal pattern of aft isochrons which follow present day topographic elevation youngest aft ages 100 ma are encountered at sealevel in the inner fjords near the areas of highest topography ages increase radially outward to the mountain peaks and the coastlines forward modeling of age elevation patterns suggests that mesozoic geothermal gradients were 10 15 c km higher than the present value of 20 c km during the triassic and jurassic a total of 1 3 3 5 km of overburden was removed from the study area assuming a 30 c km geothermal gradient for that period we attribute this to rift margin erosion as a result of erosional base level lowering and flank uplift as evidenced by thick continental clastic sequences deposited in triassic jurassic half grabens in the north sea basins we propose that 1 5 2 5 km of neogene exhumation were a result of late stage domal uplift this is supported by basinward dipping pre neogene strata in the basins surrounding southern norway and the infill of a 1 to 2 km thick neogene sediment wedge containing various internal unconformities domal uplift probably started in the late oligocene may have been amplified in the pliocene and was overprinted by plio pleistocene glacial erosion maximum neogene tectonic uplift is estimated at approximately 1 1 5 km radially decreasing outward to a value 500 m near the shoreline neogene domal uplift is coincident with oligocene and pliocene plate reorganizations in the north atlantic similar neogene domes are found around the norwegian greenland sea i e svalbard and the barents sea northern norway east greenland suggesting a regional tectonic cause the onset of neogene uplift postdates major volcanism and continental breakup by 25 m y and predates plio pleistocene glaciations its origin is possibly a combination of induced mantle convection resulting in thermal erosion of the lithosphere and the operation of intraplate stresses

seismic stratigraphic subdivision of the triassic succession in the central north sea integrating seismic reflection and well data the triassic sedimentary succession in the central north sea has been investigated to establish a broader understanding of the triassic period from the combined interpretation of seismic reflection data and well data the triassic succession has been subdivided into four seismic units where unit boundaries are characterized by regional seismic amplitude anomalies reflecting changes in gross sedimentary facies or rock properties a successful correlation between sedimentary facies interpreted within the well sections and distinct seismic reflection patterns allowed a thorough mapping of the gross palaeoenvironment throughout the triassic the method presented of subdividing a continental sedimentary succession into seismic units should be applicable elsewhere in other basins the main source area during the triassic was scandinavia to the north and sediment transportation was mainly along north south and ne sw trending lineaments which are at present located onshore southern norway and in the asta graben and the varnes graben offshore an uplifted skagerrak graben area acted as source area in the early and early middle triassic with sediment dispersal to the south and sw high relief existed for a longer period in western scandinavia than in eastern scandinavia which supports an asymmetric shape of the scandinavian mountains during the triassic accommodation space in the early triassic was mainly controlled by the relief inherited from a late carboniferous permian rift phase although thermally induced regional subsidence continued in the middle and late triassic creation of local accommodation space was mainly limited to halokinesis including redistribution and withdrawal of salt from the subsurface the upper triassic succession is eroded across the western and central parts of the study area although the upper triassic unit is preserved in synforms adjacent to salt structures in the western part of the study area dry playa conditions prevailed during the early triassic although fluvial systems supplied long transported sandy detritus southeastwards in the late early triassic more sandy detritus was transported into the sedimentary basin in the middle and late triassic concurrently with a gradually wetter climate supplementary material uninterpreted seismic sections are available at www geolsoc org uk sup18726

linking changes in tectonic style with magmatism in northern europe during the late carboniferous to latest permian abstract early carboniferous to permian magmatism associated with rifting within the northern foreland of the variscan orogen was widespread across europe during the long period of magmatic activity the regional tectonic setting changed across the region from early carboniferous extension and basin formation to a rifting wrenching style of deformation in the late carboniferous stephanian to early permian wrenching and faulting were accompanied by widespread voluminous and episodic magmatic extrusion intrusion and underplating this was followed by thermal relaxation and the development of the northern and southern permian basins in later permian times thermal relaxation was punctuated by a permo triassic phase of extension and graben formation 40ar 39ar ar step heating dating for mineral separates and whole rock samples of magmatic rocks from southern scandinavia oslo graben and south sweden and rugen north germany provides further radiometric evidence for three of the proposed periods of magmatic activity in the region latest carboniferous to earliest permian ages c 300 310 ma were obtained for volcanic rocks in the oslo graben and dolerite sills and dykes in south sweden and north germany this phase can be time correlated with magmatic activity that occurred throughout europe during large scale dextral wrenching that followed the variscan orogeny a second phase of alkaline intrusions is confined to the oslo graben and related to caldera collapse around c 275 ma the third permo triassic phase c 250 ma is considered to be related to a new tectonic cycle involving extension that triggered minor melting of enriched fertile mantle

when will the summer arctic be nearly sea ice free 1 the observed rapid loss of thick multiyear sea ice over the last 7 years and the september 2012 arctic sea ice extent reduction of 49 relative to the 1979 2000 climatology are inconsistent with projections of a nearly sea ice free summer arctic from model estimates of 2070 and beyond made just a few years ago three recent approaches to predictions in the scientific literature are as follows 1 extrapolation of sea ice volume data 2 assuming several more rapid loss events such as 2007 and 2012 and 3 climate model projections time horizons for a nearly sea ice free summer for these three approaches are roughly 2020 or earlier 2030 10 years and 2040 or later loss estimates from models are based on a subset of the most rapid ensemble members it is not possible to clearly choose one approach over another as this depends on the relative weights given to data versus models observations and citations support the conclusion that most global climate model results in the cmip5 archive are too conservative in their sea ice projections recent data and expert opinion should be considered in addition to model results to advance the very likely timing for future sea ice loss to the first half of the 21st century with a possibility of major loss within a decade or two

northward sediment transport from the late carboniferous variscan mountains zircon evidence from the oslo rift norway proto rift late carboniferous fluvial and deltaic sandstones from the asker group are locally preserved in the upper palaeozoic oslo rift high precision u pb ages of single detrital zircon grains from a moscovian late westphalian to early stephanian sandstone and overlying tuffaceous sediments that predated initial basaltic volcanism have been used to study the provenance of the detritus and to evaluate the tectonic significance of the deposits we find late neoproterozoic of avalonian affinity cambro ordovician and early carboniferous detrital zircons requiring that one of the source regions was located along or south of the axis between southern england and northeastern germany and implying sediment transport from the south probably as a consequence of uplift during the asturic compressional phase of the variscan orogeny other age groups reflect typical baltic sources possibly from the ringkobing fyn high detrital zircons and monazite from underlying silurian sandstone wenlock ludlow yield svecofennian to sveconorwegian as well as late ordovician ages but lack late neopoterozoic avalonian ages it is thus unlikely that the bulk of the carboniferous detritus could have been derived by recycling of preexisting silurian sandstones these data imply that the rivers feeding the asker group originated in the variscan mountains and entered the oslo proto rift from the south possibly via the horn graben or along the sorgenfrei tornquist zone

diagenesis in oxidising and locally reducing conditions an example from the triassic skagerrak formation denmark abstract diagenetic changes in red and white parts of the skagerrak formation triassic from onshore wells in denmark were analysed by scanning electron microscope electron microprobe and petrographic microscope in reflected and transmitted light the diagenetic sequences of the red and white parts of the skagerrak formation are in many ways the same early infiltration clays followed by precipitation of caliche calcite dolomite mixed layer illite smectite quartz feldspar kaolin minerals illite chlorite and anhydrite with increasing burial differences between the red and white parts of the skagerrak formation comprise oxidation stage in detrital minerals oxidation of glauconite in the red part and reduction of biotite in the white part the presence of eogenetic authigenic minerals pyrite and poikilotopic calcite in the white part hematite and red coatings in the red part the amount of mesogenetic authigenic kaolin minerals larger in the white part the chemistry of mesogenetic authigenic chlorite mg rich in the red part and fe rich in the white part and the preservation stage of detrital opaque minerals magnetite hematite chromite ilmenite show none or minor alteration in the red part whereas they have been almost completely altered in the white part as the differences between red and white areas are found both in early eogenetic and in mesogenetic authigenic minerals different oxidising conditions must have prevailed immediately after the deposition and continued into burial oxidising conditions were dominant in the arid triassic climate and the widespread red colour of the skagerrak formation was probably formed during early diagenesis due to precipitation of iron oxides or hydroxides locally reducing areas were formed probably by oxidation of organic material precipitation of oxidised iron minerals was thus prevented and the original white colour was preserved reducing conditions prevailed until the reducing agent was exhausted then an outer rim of the reduction spot might locally have been secondarily oxidised these changing redox conditions explain the occurrence of hematized authigenic pyrite and crandallite group minerals in red areas

mesozoic and cenozoic tectonic evolution of scania southern sweden abstract triassic to early cretaceous transtensional sinistral tectonics induced the subsidence of fault bounded basins in scania late cretaceous dextral transpressional deformations induced the inversion of these basins and the uplift of major basement blocks the resulting structural relief is of the order of 2000 m

retreat of the cold halocline layer in the arctic ocean we present a comparison of arctic ocean hydrographic data sets from the 1990s with a focus on changes in the upper few hundred meters of the eurasian basin the most recent observations discussed here were collected during the spring 1995 scientific ice expedition scicex 95 the second in a series of scientific cruises to the arctic ocean aboard u s navy nuclear submarines although the 1990s have seen an abundance of synoptic cruises to the arctic this was the only one to take place in winter spring conditions other data considered here were collected during the first scicex cruise in summer 1993 scicex 93 and during an icebreaker cruise to the eurasian basin in summer 1991 oden 91 a new russian american winter climatology is also used as a reference these comparisons reveal that the eurasian basin cold halocline layer has retreated during the 1990s to cover significantly less area than in previous years specifically we find a retreat from the amundsen basin back into the makarov basin the latter is the only region with a true cold halocline layer during scicex 95 changes are also seen in other halocline types and in the atlantic water layer heat content and depth since the cold halocline layer insulates the surface layer and thus the overlying sea ice from the heat contained in the atlantic water layer this should have profound effects on the surface energy and mass balance of sea ice in this region using a simple mixing model we calculate maximum ice ocean heat fluxes of 1 3 w m 2 in the eurasian basin where during scicex 95 the surface layer lay in direct contact with the underlying atlantic water layer the overall cause of water mass changes in the 1990s might have been a shift in the atmospheric wind forcing and resulting sea ice motion during the late 1980s which we speculate influenced the location where fresh shelf waters flow into the deeper basins of the arctic ocean finally we discuss two different mechanisms that have been proposed for cold halocline water formation and we propose a compromise that best fits these data

triassic paleogeography of the greater eastern norwegian danish basin constraints from provenance analysis of the skagerrak formation abstract zircon u pb geochronometry and heavy mineral ccsem analysis are used to determine the provenance of the skagerrak formation which was deposited during most of the triassic period as an up to 3 km thick succession the sampled sandstones are collected in well cores from the norwegian danish basin the sorgenfrei tornquist zone and the skagerrak kattegat platform with the goal of obtaining a geographically and stratigraphically representative dataset usable for investigating provenance and the implications for triassic paleogeography the basement in the source terranes has pronounced differences in zircon ages so it is possible to distinguish which terranes the zircon grains were derived from the zircon ages found in the skagerrak formation are comparable to source terranes in southern norway and southwestern sweden including the telemarkia terrane the idefjorden terrane and the eastern segment of the sveconorwegian orogen the basement and paleozoic sediments of the skagerrak graben and the skagerrak kattegat platform were presumably exposed to erosion during the early to middle triassic as indicated by the abundant rock fragments present in the skagerrak formation south of this elevated area this local input was mixed with vast amounts of material transported from other basement areas in the northeast and their cover the material was transported by rivers that downstream developed into braid plains with braided rivers and aeolian activity the decreasing grain size up through the skagerrak formation is reflecting the gradual overstepping of the basin margins thus sediment supplied by local erosion is absent in the upper part of the formation the heavy mineral assemblages are mineralogically immature due to the arid depositional conditions and the limited temporary storage during transport the assemblages are very uniform in the norwegian danish basin whereas they are characterized by local inputs on the skagerrak kattegat platform a locally deposited basement conglomerate indicates that the basement beneath northern denmark has ages corresponding to the telemarkia terrane in southern norway similarly to the ages of the basement beneath southern denmark

the late rhaetian transgression in southern sweden regional and global recognition and relation to the triassic jurassic boundary palynological investigations of rhaetian outcrops and drillcores in combination with subsurface data from wells in scania southern sweden have revealed the presence of marine dinoflagellate cysts in sedimentary strata that were previously considered to have been deposited in a mainly terrestrial environment two distinct dinocyst events are identified one older event where persistent rare to common occurrences of rhaetogonyaulax rhaetica and lunnomidinium scaniense indicates deposition in shallow marine and marginal marine environments this lunnomidinium interval is preceded and succeeded by assemblages with rare to common r rhaetica and can be correlated with the mid to late rhaetian r rhaetica zone it is associated with spore pollen assemblages of the mid rhaetian rhaetipollis limbosporites zone the younger event the r rhaetica maximum interval is characterised by mass occurrence of r rhaetica with less common or absent dapcodinium priscum in association with a dark grey to black mudstone shale the introduction of d priscum in association with the over whelming abundance of r rhaetica allows correlation with the transition between the r rhaetica zone and the succeeding d priscum zone and signals fully marine conditions the r rhaetica maximum interval is associated with spore pollen assemblages of the late rhaetian ricciisporites polypodiisporites zone and is in sweden succeeded both lithostratigraphically and palynostratigraphically by the t j transition the r rhaetica maximum interval corresponds to a late rhaetian maximum flooding event that took place in a shallow gently sloping embayment that covered the danish basin area during the late triassic early jurassic this maximum flooding event can be recognised in late rhaetian strata from different parts of the northern hemisphere it is an important temporal constraint on the t j boundary as it is associated with the disappearance of triassic marine faunas appears to coincide with the onset of the main pulse of camp volcanism immediately precedes the initial carbon isotope excursion and the global sea level drop that characterises the t j transition

latest caledonian to present tectonomorphological development of southern norway abstract the regional resultant stress field of the northeastern north atlantic has shifted significantly throughout the phanerozoic in fennoscandian parts of the caledonian orogen mountain building which was characterized by nw se contraction reference to present north was followed by a collapse with transport both parallel and transverse to the mountain chain the late palaeozoic mesozoic saw several stages of e w to nw se extension varying in time and position local episodes of inversion are traceable in some cases particularly in connection with deep seated and long lived zones of weakness the cenozoic has to a larger degree been affected by compression including folding and basin inversion again some of the more pronounced effects of local inversion are related to pre existing fault systems neogene uplift of the western mountainous area in scandinavia can be unravelled by potential field study aft data and reflection seismic sections assuming that the region is close to isostatic equilibrium the uplifted areas must be supported at depth by substantial volumes of low density material within the crust or the mantle close to the crust mantle interface or close to the lithosphere asthenosphere interfaces a series of nw se oriented cross sections representing successive stages of development from the late caledonian to present were prepared and used to analyse the tectonomorphological development as related to the shifting stress configurations three stages are inferred stage 1 devonian late permian denudation of the caledonian mountain chain during the latest stage of closing of the iapetus ocean in early to mid devonian times the caledonian mountain chain reached its maximum elevation of perhaps as much as 8 9 km including the foreland basins to the east the average topographic gradient of the eastern flank may have been in the order of 1 3 the denudation of the caledonian mountains continued into the permian and by the end of the permian the mountain system was more or less obliterated with a gradient of the eastern flank probably continued to fall to less than 0 1 stage 2 triassic late cretaceous tectono thermal uplift of central south norway uplift of central south norway was rejuvenated in triassic times and continued throughout the jurassic and early cretaceous the gradient of the eastern flank increased to a maximum of approximately 0 15 and master structural elements like the laerdal gjende olestol fault complex again played important roles in the development stage 3 tertiary present renewed tectono thermal activity and post glacial rebound a second phase of post caledonian tectono thermal uplift of south central norway started in oligocene time again increasing the gradient of the eastern flank of south norway around 0 2

effects of asthenospheric heat flow in basin modelling exemplified with the danish basin a mathematical model is developed to simulate the process of basin formation by rifting subsidence is driven by crustal thinning and influenced by the transient temperature variation within the lithosphere the model offers possibilities for multiple phases of rifting superimposing non steady state conditions important features in the model are two layered heat production and a definition of the lower boundary in terms of heat flow instead of one of constant temperature as opposed to other models furthermore phase transformations caused by rift induced pressure and temperature changes are suggested as an additional syn rift subsidence mechanism the relevant phase transformations are assumed to be those occurring during an amphibolite to granulite facies transition perturbation of the steady state temperature profile is performed by one or several phases of rifting with finite stretching rates by sill intrusion or by changes in asthenospheric heat flow the greatest deviation from the steady state geotherm occurs at the lower boundary because of the flow definition of the lower boundary the consequence of this is a much longer duration of anomalous heat flow the model is applied to the danish basin north jylland denmark this basin was formed in permian times and since then it has been thermally subsiding apart from a minor event of stretching in the late cretaceous the higher present day heat flow in the basin compared to the adjacent fennoscandian shield area is successfully explained by the model presented in this paper it is concluded that transient temperature conditions still today contribute significantly to present surface heat flow although main rifting took place for more than 240 m y ago this cannot be explained by models using a fixed temperature definition of the lower boundary the modelled contribution by phase transformations to subsidence explains why the syn rift early and middle triassic subsidence was accompanied by insignificant faulting activity as evidenced by the seismic data available

denudation surfaces and tectonics in the southernmost part of the baltic shield abstract the sub cambrian peneplain is a fundamental landform in the scenery of the southernmost baltic shield it had been shaped during an undefined time interval in the late precambrian and became conserved below a cover of cambrian sedimentary rocks after exhumation the peneplain was subjected to further remodelling in the study of the phanerozoic denudational and tectonic history the sub cambrian peneplain forms an important reference surface mesozoic and tertiary denudation surfaces and sediments dominate in the south and reveal the sequence of events later in the phanerozoic

the horn graben and its relationship to the oslo graben and the danish basin abstract the tectonic development of the horn graben the danish basin and the oslo graben are compared with special emphasis on the timing of their initiation the comparison is based on seismic interpretation and is supported by analysis of tectonic subsidence devonian and carboniferous sedimentary strata and rotliegende volcanics constitutes the pre rift succession in the horn graben in the central part of the graben it rests unconformably on precambrian possibly dalslandian basement to the south on caledonian metamorphic basement whereas lower palaeozoics occur to the north the distribution of these pre devonian assemblages suggests initial early devonian uplift of the ringkobing fyn high as the lower palaeozoic sediments are believed to have covered the high originally further uplift appears to have taken place in the early permian a subdivision of the horn graben into a northern and a southern segment are recognized the rifting was apparently heralded only in the southern segment in the rotliegende and the main rifting phase did not start before the triassic subsidence modelling shows that the thermal anomaly created by rifting of the horn graben was less significant than in the danish basin and resulted in much less post rift thermal subsidence the reduced thermal anomaly may account for an earlier consolidation of the crust thereby rendering the area resistant to late cretaceous early tertiary inversion tectonism the oslo graben was tectonically active during late carboniferous to early permian times and essentially became inactive during triassic times when the main tectonism of the horn graben occurred subsidence modelling shows that the danish basin south of the fjerritslev trough was tectonically active mainly during the zechstein whereas the rapid triassic subsidence is modelled to be caused by phase transformations as indicated by the minor amount of basement attached faulting based on the differing subsidence patterns it is concluded that the three basins did not develop simultaneously and that they are not genetically related

structure and tectonic evolution of the tornquist zone and adjacent sedimentary basins in scania and the southern baltic sea area abstract southernmost sweden bornholm and the surrounding baltic sea region are located on a large scale releasing bend in the dextral strike slip system of the tornquist zone with its resulting pull apart basins the well constrained geology of scania and bornholm has been combined with detailed on and offshore borehole data and three proprietary marine seismic surveys this in conjunction with supplementary babel deep seismic reflection findings allows a combined 3d interpretation of sediment structure interactions as a result a regional interpretation has emerged which gives a new understanding of the interplay between structural movement on a complex strike slip fault system tornquist zone and its intrazonal depressions vomb trough and colonus shale trough as well as the sedimentation history of associated areas of sediment accumulation ronne and arnager grabens hollviken halfgraben hano bay basin and skurup platform detailed sequential litho and seismo stratigraphic descriptions have been possible by combination of the various data sets this resulted in the clarification or recognition of previously unknown structural limits to sub basins and highs in the study area a 3d chronological 4d model for the development of the region is proposed this model takes into account the long lived structural history combining elements of strike slip extension and inversion tectonics the deep seated faulting controlling these structures is integrated with the deep structure as revealed by the babel line in this area

scattering of continental shelf waves at a discontinuity in shelf width abstract an analytical solution is presented for the scattering of a free shelf wave incident upon a discontinuity in shelf width in a barotropic ocean the discussion of solutions relying on backscattered free waves with large wavenumbers which may not exist in a realistically stratified ocean is avoided by considering only the range of parameters over which energy transmission is nearly 100 there is a substantial transfer of energy to modes other than that of the incident wave the mode most readily excited is that which has the cross shelf structure most closely coinciding with that of the incident wave the resultant presence of multiple modes produces a strong alongshelf modulation in flow intensity and phase progression downstream of the scattering region which may affect the interpretation of shelf wave observations a nondispersive long shelf wave pulse is shown to scatter into a train of pulses of differing mode number each propagating at its own flee wave speed