palaeomagnetism of the late precambrian vadso and barents sea groups varanger peninsula norway abstract a palaeomagnetic study has been made on neoproterozoic rocks from the varanger peninsula northernmost norway several of the formations studied contain a stable magnetization of diagenetic origin two main groups of directions were obtained one a with a steep southeasterly positive direction the other b with a shallow northern direction the group a direction is not in accordance with the stratigraphic age of the rocks and the fennoscandian apparent polar wander path hence it may reflect a remagnetization the group b direction yields a late riphean early vendian palaeopole at 24 n 207 e dp 5 dm 11 n 11 in good agreement with data from contemporary rocks of the kola peninsula the varanger peninsula is transected by the trollfjord komagelv fault which divides the peninsula into the allochthonous barents sea region and the autochthonous varangerfjord region previous palaeomagnetic studies have suggested that the barents sea region has moved 500 to 1000 km to its present position this study indicates that the movement has been less than 250 km which is in better agreement with geological information

palaeomagnetism mafic dykes and the protogine zone southern sweden the protogine zone pz forms the border between the svecofennian and sveconorwegian domains of southern sweden intruded in the zone are three generations of mafic dykes dated 1510 ma 1180 ma and 930 ma a palaeomagnetic study of these dykes in the central and southern parts of the pz yields two main directions of magnetization a d 291 i 78 n 31 and b d 129 i 40 n 13 these directions give palaeopoles on the sveconorwegian loop of the fennoscandian apparent polar wander path apwp a third poorly defined group c yields a mean declinationof 185 and inclination of 9 with the corresponding palaeopole situated on the c 1500 1600 ma part of the apwp two other sites yield palaeopoles located in the 1200 ma part of the path the data imply that the sveconorwegian orogeny caused a remagnetization of the two older dyke generations and that this remagnetization was complete in the southern part of the pz while a few dykes retained their original magnetization in the central part of the zone either the difference between the a and b directions record appreciable apw movement during differential cooling of the pz or the a and b directions may represent an asymmetric reversal of the earth s magnetic field in the latter case they may be contemporary and have implications for the size and form of the sveconorwegian loop of the fennoscandian apwp

evidence of an extratropical atmospheric influence during the onset of the 1997 98 el nino the major 1997 98 el nino episode was initiated by a series of very energetic westerly wind bursts in late 1996 and early 1997 downwelling oceanic kelvin waves were subsequently generated and propagated rapidly eastward across the equatorial pacific ocean and induced significant warming in the eastern basin by analyzing newly available wind products derived from ssm i satellite observations we found indications that these westerly wind bursts were embedded within the active phase of the tropical intraseasonal oscillation the madden julian oscillation but their amplitudes were greatly enhanced in the western pacific sector the local enhancement involved the development of equatorial twin cyclones which themselves were induced by northerly cold surges from east asia western north pacific into the tropical pacific demonstrating an extratropical atmospheric influence on tropical processes

cross equatorial influence of winter hemisphere subtropical cold surges abstract two case studies are presented of winter hemisphere cold surges affecting the summer hemisphere tropics one case has been chosen from each of the northern and southern hemispheres in both instances the subtropical rise in pressure is tracked equatorward this leads to a pressure rise at the equator and the establishment of a west east pressure gradient at low latitudes in the opposite hemisphere these effects lead in turn to an enhanced cross equatorial component of flow and enhanced monsoon westerly flow in the summer hemisphere both enhanced wind flow effects are observed through a deep layer from the surface up to at least 500 mb in both cases the sequence of events also includes the development of a tropical cyclone in the summer hemisphere monsoon trough the generality of the above sequence of events is investigated with time series data for several seasons it is shown that day to day changes in equatorial pressure are significantly correlated to pressure changes in the winter hemis

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

pre grenvillian and grenvillian lithotectonic regions in eastern labrador correlations with the sveconorwegian orogenic belt in sweden the trans labrador batholith groswater bay terrane and lake melville terrane are three major crustal segments located adjacent to or within the grenville province in eastern labrador each crustal segment is a distinct lithotectonic entity displaying contrasts with each other in proportions of rock types structural style and metamorphic imprint together they indicate a unilateral polarity to the region partly reflecting grenvillian tectonism which sliced the region into thrust bound blocks in all three crustal segments an archean or aphebian gneissic basement is inferred onto or adjacent to which ca 1900 1700 ma supracrustal rocks were deposited deformation metamorphism and granitoid pluton emplacement were partly coeval with and partly postdated the supracrustal assemblages in the north tectonothermal effects can be assigned to hudsonian ketilidian orogenesis but their peak was 50 100 ma later farther south post tectonic granitoid plutons and layered mafic intrusions were emplaced at about

observations of rossby waves linked to convection over the eastern tropical pacific rossby wave activity propagating into the eastern tropical pacific from the midlatitudes during northern winter is examined in some detail these waves are associated with the intrusion of high potential vorticity air into low latitudes and they modulate cloudiness stability and vertical motion in the vicinity of the itcz in the upper troposphere and lower stratosphere the horizontal phase and group propagation of the wave activity are qualitatively like those of a nondivergent barotropic rossby wave as the waves move equatorward they become more shallow and propagate upward into the stratosphere the horizontal and vertical propagation is consistent with the tilts of the waves the large scale three dimensional background flow and with the signatures of momentum and heat fluxes associated with the wave activity in the lower troposphere paired cyclonic anomalies on either side of the equator accompany the upper level wave activity to the west of the itcz cloudiness signal these waves amplify following the peak in the itcz cloudiness and propagate westward along the equator this suggests that the upper level wave activity and possibly the associated convective heating can trigger the excitation of the equatorially trapped rossby modes the transient wave activity appears to be a crucial component of the momentum balance of the eastern tropical pacific circulation there is substantial interannual variability in the wave activity consistent with observed changes in the large scale basic state associated with the southern oscillation

how well do precambrian paleomagnetic data agree with the phanerozoic apparent polar wander path a baltica case study abstract precambrian paleomagnetic data are crucial for various tectonic and geophysical applications the reconstructions of fusion and fission of supercontinents in particular due to many objective reasons the variety of stability tests for these data are abridged in comparison to phanerozoic results and is further hindered by the rather common refusal to consider the resemblance between precambrian and younger poles in this paper we selected precambrian paleomagnetic data with ages of

an index for tropical temperate troughs over southern africa strong cases of the tropical temperate troughs ttt that are responsible for the most of the summer rainfall over subtropical southern africa are analyzed an index for identifying the ttt is introduced for the first time using anomalies of outgoing longwave radiation olr and the wind the ttt is associated with a ridge trough ridge wave like structure in the lower troposphere over southern africa and the adjoining indian ocean therefore the index considers physical processes that occur over southern africa adjoining the atlantic and indian oceans to depict the variability of the ttt events unusually strong ttt events are identified when the standard deviations of the ttt indices defined by the olr and wind anomalies in the selected regions are above 1 5 and 0 5 respectively after applying this criterion and filtering out consecutive events 55 ttt events are identified during the study period of december january february seasons from 1980 1981 to 2009 2010 from the composite analyses of those 55 events it is found that the ttts evolve with suppressed enhanced convection over the southwest indian ocean adjacent to madagascar southern africa the suppressed convection is in turn found to be associated with the enhanced convection around sumatra in the southeast tropical indian ocean this may explain why more ttt events occur in la nina years as compared to el nino years time evolution of the canonical ttt event shows that it starts 3 days prior to the mature phase of the event suggesting possible predictability after reaching a matured state the system moves east toward the indian ocean and decays within the subsequent couple of days in addition the intertropical convergence zone itcz structure changes over southern africa madagascar during the ttt event and remains similar to climatology over other regions the results indicate that the continental part of the itcz intensifies prior to the ttt event and then spreads southward following the mid latitude influence during and after the event

the late holocene gargano subaqueous delta adriatic shelf sediment pathways and supply fluctuations the gargano subaqueous delta formed on the eastern and southeastern sides of the gargano promontory in the western adriatic this subaqueous deposit represents the southernmost portion of the late holocene highstand systems tract hst growing along the western side of the adriatic as an extensive wedge of deltaic and shallow marine mud the late holocene hst rests above a regional downlap surface that marks the time of maximum landward shift of the shoreline attained around 5 5 cal kyr bp at the end of the late pleistocene holocene sea level rise high resolution seismic stratigraphic and tephra correlation indicate the presence of a thin basal unit recording condensed deposition between 5 5 and 3 7 cal kyr bp over much of the basin above this unit sediment accumulation rates increased to high values as much as 1 5 cm yr 1 reflecting the stabilisation of relative sea level and the forcing from high frequency climatic or anthropogenic changes affecting river dynamics the late holocene mud wedge of which the gargano subaqueous delta is a significant component reaches up to 35 m in thickness and has a volume of ca 180 km3 the shore parallel thickness distribution of the mud wedge reflects the dominant oceanographic regime of the basin and the asymmetric location of the mostly western sediment sources with a combined modern delivery of 51 7 106 t yr 1 of mean suspended load in sections perpendicular to the coast the late holocene mud wedge appears composed of forestepping clinoforms with gently dipping foresets typically 0 5 the gargano subaqueous delta is characterised by a submarine topset in water depths shallower than 25 28 m and accounts for about 1 7th of the total volume of the late holocene mud wedge despite the absence of direct river supply to the gargano area in the area of maximum interaction between shore parallel currents and basin morphology progradation occurs onto a flat and barren bedrock outcrop in about 50 80 m water depth the rapid transition from a thickness of 30 m of late holocene mud to nil is a good indication of the role of southward flowing bottom hugging shelf currents in causing the redistribution of sediment along the adriatic inner shelf additional evidence of this regime comes from 1 the most recent sigmoid defined at seismic stratigraphic scale deposited since the onset of the little ice age showing a shore parallel thickness distribution and a main depocentre to the southeast of the gargano promontory 2 the maximum values of sediment accumulation rates over the last century documented by 210pb measurements defining a narrow shore parallel belt immediately seaward of the depocentre of the most recent sigmoid the gargano subaqueous delta grows from the outbuilding of progressively younger progradational sigmoids that tend to parallel the previous ones the gargano subaqueous delta differs from other documented late holocene subaqueous deltas because its growth reflects 1 sediment transport dominated by bottom currents sub parallel to the strike of the composing clinoforms 2 a complex supply regime including the po delta 350 km to the north and several coalescing apennine rivers acting as line source 3 several alternating intervals of enhanced outbuilding and condensed deposition and 4 an in phase growth of the most recent sigmoid with the major progradation of the po delta during the little ice age

southern hemisphere summertime rossby waves and weather in the australian region motivated by recent studies on the significant summertime weather patterns in the australian region the life cycle of summertime transient rossby wave packets in the southern hemisphere is investigated the strength of the interaction between the wave packets and the jet i is defined by the advection of potential vorticity by the divergent part of the wind on the 350 k isentropic surface the magnitude of i is used as the basis for time lagged composites in distinct regions sw chile sw africa over the indian ocean sw australia and over the w pacific the interaction is strongest on the stratospheric side of the jet core although in each case cyclogenesis from a pre existing disturbance in the upper troposphere precedes the generation of the rossby wave packets there are two types of interaction with the jet in the sw chile sw africa and indian ocean cases extratropical cyclogenesis and the associated convection lies on the poleward side of the jet and hence i is positive in the sw australia and w pacific cases extratropical cyclogenesis occurs 3 days earlier than the others and i is negative as it describes the interaction of a downstream propagating rossby wave packet with the subtropical jet in all cases as the cyclones develop the wave activity propagates from low levels to the upper levels of the troposphere and then downstream and equatorwards towards higher values of refractive index the equatorward refraction of the sw australia and w pacific wave packets is accompanied by enhanced tropical convection in the warm conveyor belt of the advancing front

preservation of laminated shale in ancient clinoforms comparison to modern subaqueous deltas in phanerozoic fine grained marine sedimentary deposits preservation of physical lamination is commonly presumed to record anoxic benthic conditions lamination may also be preserved however in oxygen rich settings where sediment influx is rapid and as a consequence high levels of turbidity and fluid substrates inhibit colonization by benthic organisms differentiation between these two situations is critical for accurate paleoenvironmental interpretations the recognition of clinoforms which are common in ancient fine grained successions is a key step in making this distinction in the tropic shale and correlative tununk member of the mancos shale of southern utah clinoforms are preserved in two superposed depositional sequences the fourth and fifth sequences in the succession the geometry of the clinoforms indicates that foreset deposits accumulated relatively rapidly and bottomset deposits more slowly in sequence 4 patterns of preservation of lamination in clinoforms resemble those in modern subaqueous deltas these ancient clinoforms evidently prograded into oxygenated waters and preservation of lamination was primarily controlled by the rate of sediment accumulation in sequence 5 however the oxygen level apparently controlled the preservation of lamination

characteristics of wave packets in the upper troposphere part i northern hemisphere winter abstract gridded data produced by the ecmwf reanalysis project have been analyzed to document the properties of wave packets in the northern hemisphere winter midlatitude upper troposphere based on results from earlier investigations 300 hpa meridional wind variations were chosen for analysis wave packet envelopes were also defined by performing complex demodulation on the wind data the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed both on and wave packet envelopes the results show that over most regions in the northern hemisphere winter with the exception of the deep tropics and near the aleutian low medium scale waves dominant wavenumber 5 8 exhibit the characteristics of downstream development and occur within wave trains that propagate with eastward group velocities much faster than the phase speeds of individual phases of the waves their group velocity is highly correlated with the local time mean 200 400 hpa wind while the

adjustment of the atmospheric circulation to tropical pacific sst anomalies variability of transient eddy propagation in the pacific north america sector nas a pattern that is shifted southward northward compared with climatology paths of coherent phase propagation of transient eddies and of the propagation of wave packets are analyzed a coherent path of propagation across the pacific towards north america is identified that is more zonal during el niwinters and during la nihas a dominant path heading northeastward to the pacific northwest a second path heading southeastward from the central pacific to the tropical east pacific is more accentuated during la ni nas than el ni nos these changes in wave propagation are reproduced in an ensemble of seasonal integrations of a general circulation model forced by a tropical pacific sea surface temperature pattern confirming that the changes are forced by changes in the mean atmospheric state arising from changes in tropical sea surface temperature a simplified model with a specified basic state is used to model the storm tracks for el ni no and la ni na winters the results suggest that the changes in transient eddy propagation and the eddy statistics can be understood in terms of the refraction of transient eddies within different basic states copyright c 2010 royal meteorological society

description of the polar profile transect display abstract the polar profile transect display attempts to integrate all the existing aeromagnetic gravimetric geological and geochemical investigations with the results of the deep seismic and electromagnetic studies carried out along the polar profile our description is based on the stage of joint interpretation reached at the second earth science study centre the nearly 440 km long ne sw trending polar profile traverses archaean and early proterozoic parts of the baltic shield the thickness of the crust varies between 40 and 50 km and consists of three distinct crustal layers a geological interpretation based on the various geophysical results is given for the uppermost 10 14 km thick layer in the central part of the profile the overthrust early proterozoic lapland granulite belt forms a wedge shaped body reaching the middle crust the upper crust is underlain by a transparent layer 16 18 km thick with a smooth increase in velocity and density a reflective lowermost 10 21 km thick layer has a high velocity gradient the crust mantle has a pronounced topography

late cretaceous climate changes recorded in eastern asian lacustrine deposits and north american epieric sea strata abstract cretaceous climate data of the long lived cretaceous songliao basin sb in eastern asia is correlated and compared with the western interior seaway wis on the northern american plate in order to understand better the dynamics of the earth s past greenhouse climates nearly continuous late cretaceous terrestrial deposition in the songliao basin is represented by two cores totaling 2431 m in length the turonian maastrichtian age of the section is based on integrated stratigraphy and is comparable in age with upper cretaceous strata in the wis being consistent with global trends the dynamic late cretaceous climates of both the sb and wis gradually cooled from the warmest albian cenomanian time to the end of the maastrichtian with several intervening warm periods as did the global climate however regional differences existed the songliao basin climate was humid to semi humid warm temperate subtropical and the western interior seaway was in the humid warm temperate zone and experienced only moderate climatic changes the shifts of oxygen isotope data in the songliao basin were frequent and abrupt whereas wis records more gradual change affected mainly by fresh water runoff mixing with southern tethyan and northern arctic waters sedimentary cycles of eccentricity obliquity and precession bands are recorded in both the sb and wis basins the sedimentary cycles in the wis and sb are interpreted to be related to variations of the wet dry runoff cycles which indicate that orbital forcing played an important role in global climate change in late cretaceous the most favorable condition for organic carbon burial in both the sb and wis basin was bottom water anoxia regardless of the cause of the anoxia but the organic carbon burial rate was usually much higher in the songliao lake than in the wi epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric co 2 in both basins organic rich deposits formed during a rise in water level and incursion of saline waters the integration of paleoclimate data from cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the cretaceous greenhouse climate change and may provide insights for a future greenhouse world

recurrent depletion of benthic oxygen with 4th order transgressive maxima in the cretaceous western interior seaway abstract a study was designed to investigate the relationship between depletion of benthic oxygen and 4th order sea level change within the cretaceous western interior seaway of north america three 4th order sea level change cycles were studied in strata belonging to the tropic shale and the tununk shale member of the mancos shale in utah these sedimentary deposits accumulated within prodeltaic environments in utah strata belonging to all three 4th order cycles exhibit evidence for depletion of benthic oxygen at times of peak 4th order transgression and development of condensed sections the evidence includes decreased intensities of bioturbation increased cr al ni al and zn al ratios and decreased mn fe ratios the data also suggest that depletion of benthic oxygen in the distal section preceeded that in the more proximal one and thus may reflect episodic expansion of an oxygen depleted water mass es from the pelagic to the prodeltaic environment of the seaway evidence for subsequent increases in benthic oxygen level with the onset of 4th order regressions is interpreted to reflect either aggradation of the seafloor above the oxygen poor water due to sediment accumulation or contraction of the oxygen depleted water mass from the prodeltaic part of the seaway or a combination of the two s organic c ratios of strata interpreted to have been deposited under conditions of depleted benthic oxygen are distinctly below 0 4 and thus were not useful for recognition of paleo oxygen levels in the prodeltaic environment this study highlights the importance of depletion of benthic oxygen as a mechanism for enhancing preservation of organic carbon in condensed sections on a hundred thousand year time scale our results underline the potential for source rock formation in similar prodeltaic deposits of other epicontinental seaways during periods of relatively high sea level and global depletion of benthic oxygen

a case study of the mechanics of extratropical influence on the initiation of the madden julian oscillation abstract mechanisms for extratropical influences on the initiation of the madden julian oscillation mjo are investigated using numerical simulations and a global reanalysis product previous simulations by a tropical channel model captured the timing and gross features of the initiations of two mjo events and suggested that the initiations were due to influences from the extratropics in this study latitudinal transport of momentum from the extratropics is found to be crucial in generating the lower tropospheric westerlies in the tropics associated with the mjo initiation the diagnoses of the zonal momentum budget for the mjo initiation region revealed that the advection by meridional winds could be important prior to the initiation of the mjo the time evolution of the wave activity identifies its source over the southern indian ocean where it grows by extracting kinetic energy from the mean flow the time scale of the lateral boundary conditions that is responsible for the mjo initiation is also inv

palaeomagnetism of middle proterozoic basic intrusives in central sweden and the fennoscandian apparent polar wander path abstract palaeomagnetic results are presented from three sets of post svecokarelian intrusions in central sweden the first is a system of e w trending doleritic dykes including the large breven and hallefors dykes and with a probable emplacement age of c 1530 ma their original nrm is disturbed by later events but two magnetic directions group ew1 with decl 359 5 incl 6 2 95 8 2 n 35 and group ew 2 with decl 11 1 incl 51 3 95 10 1 n 14 have been isolated and give palaeopoles at 27 7 n 196 8 e and 61 7 n 176 1 e respectively the group ew1 direction is considered to represent the original emplacement nrm this is based on comparison with contemporary palaeomagnetic data from elsewhere in fennoscandia the second set comprises dolerites and quartzporphyries the tuna dykes age 1371 ma they present a stable magnetization with decl 14 8 incl 18 1 95 9 6 and a palaeopole at 21 1 n 180 4 e the third set studied are dolerites belonging to the dala and jamtland complexes of the central scandinavian dolerite group csdg age c 1250 1200 ma post jotnian they present well defined magnetic directions that give palaeopoles close to the equator around 155 e in agreement with other published palaeomagnetic csdg data however there are deviating results obtain from dolerites belonging to the dala complex of the csdg those deviating have a mean decl of 12 9 incl 1 4 95 18 1 n 5 which gives a palaeopole at 27 0 n 179 5 e situated within the area of the 1600 1500 ma poles results from three probably sweconorwegian c 1000 850 ma doleritic dykes are also presented the results obtained are compared with other contemporary palaeomagnetic poles from fennoscandia and a revised apparent polar wander path is presented and discussed

modulation of equatorial subseasonal convective episodes by tropical extratropical interaction in the indian and pacific ocean regions composite relationships among outgoing longwave radiation sea level pressure surface winds and upper tropospheric circulation are examined for northern winter during subseasonal episodes of eastward progression of convection from the indian ocean to the western pacific this evolution often culminates with westerly wind burst events and strong air sea interaction associated with regional scale convective blowups in the western equatorial pacific we first document some of these interactions in the composites for two timescales the submonthly 6 30 days and that of the madden julian oscillation mjo timescale 30 70 days we then analyze the december 1992 period during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare to illustrate how these composite relationships are manifested in a case study convection in the indian ocean for the composites is shown to be associated with a northern hemisphere wave train at 200 mbar arcing through the midlatitudes that can contribute to convective blowups farther east on the submonthly 6 30 days timescale in the intertropical convergence zone itcz in the eastern pacific the eastern asian trough that is part of this wave train is associated with pressure surges from the northern hemisphere and subsequent convection over southeast asia as the mjo convective envelope moves east to australasia midlatitude wave trains in either hemisphere include upper level troughs east of asia and australia and pressure surges from either hemisphere that contribute to pressure rises over the indonesian region and a subsequent shift of the convective envelope to the western pacific the vertical wind structure for the december 1992 case study is consistent with the composite surface and upper level winds and also shows strong vertical wind shear in the boundary layer a sharply defined westerly maximum near 700 mbar and an intensification of the upper level easterlies near 100 mbar very deep westerlies to 200 mbar are confined to shorter timescales the case study illustrates the various time and space scale interactions noted in the composites reciprocal interactions between the tropics and the midlatitudes on the submonthly and mjo timescales in both the composites and the case study involve pressure surges and wave interaction that influence subsequent convection as the convective envelope migrates eastward from the tropical indian to pacific ocean region

structure and characteristics of submonthly scale waves along the indian ocean itcz this study examines wave disturbances on submonthly 6 30 day timescales over the tropical indian ocean during southern hemisphere summer using japanese reanalysis jra25 jcdas products and national oceanic and atmospheric administration outgoing longwave radiation data the analysis period is december february for the 29 years from 1979 1980 through 2007 2008 an extended empirical orthogonal function eeof analysis of daily 850 hpa meridional wind anomalies reveals a well organized wave train pattern as a dominant mode of variability over the tropical indian ocean daily lagged composite analyses for various atmospheric variables based on the eeof result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the indian ocean intertropical convergence zone itcz the wave train is oriented in a northeast southwest direction from sumatra toward madagascar the waves have zonal wavelengths of about 3 000 5 000 km and exhibit westward and southwestward phase propagation individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of sumatra into madagascar meanwhile eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern indian ocean this could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern indian ocean along the mean monsoon westerly flow in addition the waves modulate the itcz convection correlation statistics show the average behavior of the wave disturbances over the tropical indian ocean these statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis the waves appear to be connected to the monsoon westerly flow the waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow this suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical indian ocean the horizontal structure of the wave train may be interpreted as that of a mixture of equatorial rossby waves and mixed rossby gravity wavelike gyres

nature of the differences in the intraseasonal variability of the pacific and atlantic storm tracks a diagnostic study abstract on the basis of an intraseasonal variability index of storm track evaluated for 40 winters 1963 64 through 2003 04 of ncep ncar reanalysis data it is found that well defined midwinter minimum mwmin midwinter maximum mwmax occurs in 21 8 winters over the north pacific in contrast mwmin mwmax occurs in 4 25 of the 40 winters over the north atlantic the power spectrum of such an index for the pacific has a broad peak between 5 and 10 yr whereas the spectrum of the index for the atlantic has comparable power in two spectral bands 2 2 8 and 3 5 8 yr over the north pacific the increase in the zonal asymmetry of the background baroclinicity as well as in the corresponding horizontal deformation of the time mean jet from early late winter to midwinter is distinctly larger in an mwmin winter associated with these changes there is a distinctly stronger barotropic damping rate in the january of an mwmin winter the increase in the net conversion rate of eddy kinetic energy from early

a case study of downstream baroclinic development over the north pacific ocean part ii diagnoses of eddy energy and wave activity the sequential development of a western and then an eastern north pacific cyclone is examined in terms of eddy energy and a phase independent wave activity based on the propagation of both a contiguous wave activity center and eddy energy the development of the western cyclone appears to influence its downstream neighbor a quantitative comparison of these two diagnoses is made in terms of group velocity and only minor differences are found during much of the initial evolution it is only once the tropopause undulations lose their wavelike appearance at which point application of the group velocity concept itself becomes quite tenuous that the downstream propagation of eddy energy seems faster than that of wave activity conventional methods of tracking this wave packet are also briefly discussed

global teleconnections in the 250 mb streamfunction field during the northern hemisphere winter abstract teleconnections of the streamfunction in the global domain based on ecmwf 250 mb winds for the 11 northern winters from 1978 79 through 1988 89 are documented in this study a zonal structure with a node near the equator indicating an out of phase relationship between the streamfunctions in the northern and southern hemisphere appears to mask the fluctuations of the asymmetric components of streamfunction after removing zonal means a global pattern emerges as the dominant structure in the low frequency band this pattern consists of several dipoles straddling either the exit region of midlatitude jets or the equator indicating the existence of teleconnections not only between the midlatitudes and the tropics but also between the northern and southern hemispheres teleconnection patterns in the intermediate frequency band are predominantly wavelike seven waveguides are identified based on the one point lag correlation maps for base points near the maximum teleconnectivity among them are thr

sedimentary architecture of a plio pleistocene proto back arc basin wanganui basin new zealand the sedimentary architecture of active margin basins including back arc basins is known only from a few end members that barely illustrate the natural diversity of such basins documenting more of these basins types is the key to refining our understanding of the tectonic evolution of continental margins this paper documents the sedimentary architecture of an incipient back arc basin 200 km behind the active hikurangi subduction margin north island new zealand the wanganui basin wb is a rapidly subsiding plio pleistocene sedimentary basin located at the southern termination of the extensional back arc basin of the active central volcanic region tvz the wb is asymmetric with a steep thrust faulted outer arc ward margin and a gentle inner craton ward margin it contains a 4 km thick succession of plio pleistocene sediments mostly lying offshore composed of shelf platform sediments it lacks the late molasse like deposits derived from erosion of a subaerial volcanic arc and basement observed in classical back arc basins detailed seismic stratigraphic interpretations from an extensive offshore seismic reflection data grid show that the sediment fill comprises two basin scale mega sequences 1 a pliocene 3 8 to 1 35 ma sub parallel regressive bpre growthq sequence that overtops the uplifted cratonward margin above the reverse taranaki fault and 2 a pleistocene 1 35 ma to present divergent transgressive bsyn growthq sequence that onlaps i the craton ward high to the west and ii uplifted basement blocks associated with the high angle reverse faults of the arc ward margin to the east along strike the sediments offlap first progressively southward mega sequence 1 and then southeastward mega sequence 2 with sediment transport funnelled between the craton and arc ward highs towards the hikurangi trough through the cook strait the change in offlap direction corresponds to the onset of arc ward thrust faulting and the rise of the axial ranges at ca 1 75 ma resulting in 5100 5700 m of differential subsidence across the fault system sedimentation has propagated south to southeast ward over the last 4 myrs at the tip of successive back arc graben volcanic arcs and the associated thermally uplifted parts of the north island following the southward migration of the hikurangi subduction margin subsidence occurred by mantle flow driven flexure the result of active down drag of the lithosphere by locking of the hikurangi subduction interface and sediment loading the wb is considered to be a proto back arc basin that represents the intermediate stage of evolution of an epicratonic shelf platform impacted by active margin processes

large scale circulation associated with westerly wind bursts and deep convection over the western equatorial pacific the relationship between deep equatorial convection over the western pacific and atmospheric circulation during november to february 1986 1992 is studied using cross correlations between outgoing longwave radiation olr and national meteorological center global analyses we focus on intraseasonal convective events on the 6 to 30 day timescale over two regions just east of borneo and over the tropical ocean and global atmosphere toga coupled ocean atmosphere response experiment coare domain to the northeast of new guinea although comparatively little work has been done on this timescale we show that the bulk of the intraseasonal variability in both convection and low level circulation over the tropical western pacific occurs in this period range as a comparison with these higher frequency events the evolution of coare convection on the 30 to 70 day timescale is also considered the results of the historical data analysis are compared to a case study of deep convection associated with strong surface westerly winds during november 1989 this analysis is meant to serve as a benchmark for future case studies from the tropical ocean global atmosphere coare experiment and other periods in general 6 to 30 day equatorial convection in the regions studied occurs in conjunction with low level equatorial westerly wind anomalies paired anomalous cyclonic circulations straddling the equator and a strengthening of the sea level pressure gradient along the equator the increase in the pressure gradient appears most often tied to the simultaneous equatorward movement of high pressure systems originating over southeastern asia and australia a surge of trades over the central pacific also accompanies the development of convection over both study regions following the convective peak the low level westerlies slowly decay as the northern cyclone moves northwestward away from the equator in a track characteristic of a tropical depression it is also observed that low level westerly anomalies occur frequently without deep convection the vertical structure during convective events along the equator on the 30 to 70 day timescale and over indonesia in the 6 to 30 day band is baroclinic with easterly anomalies at upper levels overlying low level westerlies at 200 mbar a strengthened meridional outflow from the olr signal into a wave train on the equatorward side of the asian jet is observed to develop following the convective peak suggesting forcing of this circulation by the convection over the coare domain there is evidence that 6 to 30 day convection often occurs in conjunction with deep westerly flow it is suggested that these types of events are frequently characterized by vertical propagation of westerlies from the surface to the upper troposphere as is shown for a case study from november 1989 this westerly burst episode is shown to have many features in common with the typical case as defined from historical data

cold season synoptic scale waves over subtropical south america the most active winter synoptic scale wave patterns over south america are identified using an extended empirical orthogonal function eeof technique and are physically diagnosed using composite methods results show that the leading modes of short timescale variability propagate along two main paths over the subtropical jet latitudes 308s and over the subpolar jet latitudes 608s this research focuses on the subtropical mode and its evolution over south america the observed structure of the systems associated with the subtropical mode resembles that of midlatitude baroclinic waves both cyclonic and anticyclonic perturbations display significant modifications in their threedimensional structure as they evolve over extratropical and subtropical south america while the upper level perturbations are mostly unaffected when moving eastward the lower level perturbations advance following the shape of the andes mountains and exhibit an abrupt equatorward migration at the lee side of the mountains as a result of such detachment smaller eddy heat fluxes are observed in the vicinity of the orography and consequently a weaker eddy baroclinic growth is observed once the upper level system is on the lee side the perturbations acquire a more typical baroclinic wave structure and low level intensification of the system occurs the latter is largest around 1000 km east of the orography where enhanced moisture transports from tropical latitudes along the eastern portion of the low level cyclone favor precipitation occurrence over southeastern south america those precipitation processes seem to provide a diabatic source of energy that further contributes to the strengthening of the low level cyclone in addition an intensification of the cyclone once over the ocean was found in 60 of the situations considered which is consistent with previous research suggesting an additional source of moisture and heat flux due to the warm waters of the brazil current

sedimentologic character of ancient muddy subaqueous deltaic clinoforms down cliff clay member bridport sand formation wessex basin u k abstract muddy subaqueous clinoforms are a common feature of many modern deltas particularly those developed in basins with strong waves tides or oceanographic currents ancient examples have only rarely been reported implying that they are under recognized herein the sedimentological characteristics of muddy subaqueous deltaic clinoforms from the lower jurassic down cliff clay member of the bridport sand formation wessex basin uk are described and interpreted as a reference to re evaluate other ancient shallow marine mudstone successions deposits below the down cliff clay clinoforms consist of erosionally based bioclastic sandy limestone beds intercalated with upward thickening fossiliferous claystones and siltstones facies association a which record upward increasing water depth under conditions of minor input of clastic sediment and reworking by storm waves these deposits are downlapped by foreset to toeset deposits of the subaqueous deltaic clinoforms which comprise claystones and siltstones that contain calcareous nodules and are variably bioturbated by a low diversity trace fossil assemblages dominated by chondrites facies association b these foreset to toeset deposits record slow deposition undecompacted sediment accumulation rate of c 4 4 m myr from suspension fall out and distal sediment gravity flows under conditions of intermittent and or poor oxygenation of bottom waters clinoform foreset deposits dip paleoseaward at 2 and consist of siltstones and sandy siltstones that are moderately to completely bioturbated by a high diversity trace fossil assemblage facies association c thin

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

geophysical and geochemical evidence of proterozoic collision in the western marginal zone of the baltic shield new continental crust was formed in the svecofennian domain of the baltic shield c 1 9 ga ago approximately 0 1 0 15 ga later new crust accreted to the sw part of the shield in this paper an attempt is made on the basis of gravity measurements and lithogeochemistry to describe the tectonic processes responsible for the continental growth c 1 75 1 8 ga ago the transscandinavian granite porphyry belt tgpb separates the svecofennian domain from the polymetamorphic terrain of the sw swedish gneiss region red orthogneisses occurring immediately west of the tgpb are the deformed equivalents of the tgpb type granitoids while grey orthogneisses displaying a tonalitic granodioritic trend and situated further west were generated in a volcanic arc environment the tgpb granitoids and the red sw swedish gneisses represent a transition from this volcanic arc type rock to contemporaneous within plate type granites intruded in the svecofennian crust the volcanic arc was forced against the svecofennian crust in which large tensional fracture zones ensued with strike directions normal to the collision front in such tensional environments the withinplate type granites were generated in the collision zone the crust was down warped and huge amounts of granitic melts were generated at the base of the crust this tgpb magma rose upwards utilizing the fracture zone between the arc rocks generated slightly earlier and the svecofennian crust a relatively thin upper part of the tgpb that spread laterally westwards became strongly deformed during the collision i e the red sw swedish gneisses while the major deep reaching tgpb root zone that was not completely solidified yet acted as a buffer against the foliation front

extratropical tropical interaction during onset of the australian monsoon reanalysis diagnostics and idealized dry simulations abstract the onset of the australian monsoon is examined using i reanalysis data for seasons when enhanced observational networks were available and ii a 15 yr onset composite similar to previous findings onset is characterized by a sudden strengthening and deepening in tropical westerly winds which are overlain with upper tropospheric easterlies all onsets are preceded by up to a 7 day preconditioning period of enhanced vertical motion and moistening during the transition season the 6 weeks prior to onset a number of moist westerly events occur generally they are only sustained for short periods and overlain by upper level westerly winds suggesting an association with midlatitude troughs which protrude into the deep tropics for individual years and for a 15 yr composite monsoon onset is associated with major cyclogenesis events over the southwest indian ocean in the presence of a subtropical jet over the eastern indian ocean the proposed mechanism for extratropical tropical interaction i

palaeomagnetic study of mesozoic basalts from scania southernmost sweden summary the mesozoic basalt necks of central scania southernmost sweden yield dual polarity palaeomagnetic directions decl 33 incl 66 n 15 and decl 225 incl 73 n 6 the combined mean with the negative directions reversed is decl 35 incl 68 n 21 the corresponding palaeopole is situated at lat 69 n 103 e this pole corresponds with an early jurassic pole for europe and with early jurassic poles for north america after closing of the atlantic the early jurassic age is in contrast with k ar datings ranging between 171 and 81 ma but is in agreement with datings based on microfossils found in tuffaceous layers connected with the basalts

extratropical forcing of tropical wave disturbances along the indian ocean itcz the role of extratropical waves in the excitation of tropical waves on submonthly timescales is explored along the indian ocean intertropical convergence zone itcz during the austral summer using japanese reanalysis products and noaa outgoing longwave radiation data the analysis period is december february of 1979 1980 to 2008 2009 the submonthly tropical waves are regarded as a type of rossby wave propagating along the mean monsoon westerly flow they play an important role in modulating the indian ocean itcz convection the linkage between the tropical and extratropical waves which is responsible for the formation and strengthening of tropical waves is examined composite analysis results linked to the tropical wave train development show that the midlatitude rossby wave train progresses eastward and northeastward from the south atlantic into the subtropical indian ocean as a trough and ridge that form part of the midlatitude wave train approach the southern africa southwest indian ocean swio region a southwest northeast oriented wave train is subsequently established originating from this feature and is strengthened across the tropical indian ocean the midlatitude wave propagation toward the subtropics induces the growth of the trough and ridge over the swio wave activity flux diagnostics indicate that the amplified trough and ridge over the swio act as an energy source for northeastward amplification of the tropical waves through the wave energy dispersion process the results suggest that the propagation of the midlatitude wave toward the swio is the fundamental mechanism behind the development of the tropical waves along the indian ocean itcz

interactions between enso transient circulation and tropical convection over the pacific abstract the interannual variability of transient waves and convection over the central and eastern pacific is examined using 30 northern winters of ncep ncar reanalyses 1968 69 1997 98 and satellite outgoing longwave radiation data starting in 1974 there is a clear signal associated with the el nino southern oscillation such that differences in the seasonal mean basic state lead to statistically significant changes in the behavior of the transients and convection with periods less than 30 days which then feed back onto the basic state during a warm event el nino phase the northern hemisphere subtropical jet is strengthened over the central pacific the region of upper tropospheric mean easterlies over the tropical western pacific expands eastward past the date line and the upper tropospheric mean westerly duct over the tropical eastern pacific is weakened the transients tend to propagate along the almost continuous waveguide of the subtropical jet equatorward propagation into the westerly

westward growth of the baltic shield abstract at the closure of the orogenic processes in the svecofennian orogen roughly 1750 ma ago continental crust began to form to the present west of the newly stabilized craton this western part of the baltic shield is here considered as a growth zone the oldest documented development is the intrusion of alkali calcic granitoids 1780 ma ago within or close to the western margin of the svecofennian archaean craton this plutonism continued when calc alkalic granitoids intruded 1 6 to 1 7 ga ago still farther to the west where small amounts of older continental rocks are also preserved however final cratonization was effected by repeated intrusion of anatectic granites into the growth zone contemporaneously with rupture and mafic intrusions in the cratonized svecofennian archaean continent to the east with time the strontium isotope initials of the granitoids in the growth zone increase this suggests repeated remelting of the continental crust multistage periods of folding and metamorphism render the interpretation of some radiometric age determinations uncertain lithologically and tectonically differently developed crustal segments within the growth zone are delimited by belts of highly strained rocks the protogine and mylonite zones

extratropical forcing of convectively coupled kelvin waves during austral winter abstract observations are presented that link extratropical rossby wave disturbances excited in the southern hemisphere subtropical jet to the initiation of convectively coupled kelvin waves in the pacific intertropical convergence zone itcz during austral winter a baroclinic zonal wavenumber 6 eastward propagating rossby wave train in the subtropical jet turns northeastward in the vicinity of australia inducing upper tropospheric divergence and vertical motion fields that spread equatorward and induce cloudiness anomalies in the tropics lower tropospheric pressure surges excited from the extratropics also induce kelvin wave like geopotential height and temperature anomalies at the surface providing additional lower tropospheric convergence and vertical motion forcing the tropical outgoing longwave radiation olr and circulation fields propagate eastward in tandem with the extratropical rossby wave train at approximately 17 m s 1 kelvin wave activity in the central pacific itcz thus appears to

statistical properties of episodes of enhanced 2 3 day convection in the indian and pacific oceans abstract using 9 yr of ir brightness temperature values as a proxy for tropical convection the climatology and statistics of the 2 3 day convective oscillation signal are examined these higher frequency oscillations are shown to have a very different spatial distribution than the signal associated with the 25 70 day intraseasonal oscillation making it quite unlikely that these oscillations simply represent a form of noise in the time series the characteristics of the oscillations are shown to be strong functions of latitude season and strength of the oscillation itself only the strongest of the 2 3 day oscillations prove to be in good agreement with the properties shown in previous studies which were based on smaller spatial and temporal domains these strong oscillations manifest a strong association with the intraseasonal oscillation and westerly wind bursts particularly in the deep tropics weaker oscillations on the other hand are found to be more stochastic and less dependent on larger sca

cross equatorial influences of submonthly scale southerly surges over the eastern indian ocean during southern hemisphere winter 1 lower tropospheric southerly surges occurring at submonthly timescales over the eastern indian ocean eio during southern hemisphere sh winter are extratropical tropical interaction phenomena involving various processes this study examined the physical mechanism driving equatorial wave disturbances associated with surge induced cross equatorial flow over the eio japanese 25 year reanalysis jra25 and tropical rainfall measuring mission satellite trmm 3b42 data products from june to august for the 7 years from 1998 to 2004 were analyzed composite analyses of low level wind and vorticity fields reveal that an equatorial clockwise gyre develops just after cross equatorial penetration of southerly surge winds this gyre is interpreted as an equatorially trapped rossby wave that develops asymmetrically around the equator in response to surge induced cross equatorial flow eddy vorticity budget analysis demonstrates the dynamic role of the southerly surge in the genesis of the equatorial clockwise gyre the result indicates that an injection of negative absolute vorticity into the equatorial tropics due to both advective and convergent processes associated with the surge winds is primarily responsible for the gyre genesis cross equatorial advection of basic state absolute vorticity by the surge eddy winds and vortex stretching by surge wind convergence are most effective in spinning up the equatorial clockwise gyre wave activity flux analysis further emphasizes that rossby wave energy propagation from the sh extratropics into the equatorial eio region is caused by the southerly surge these dynamic diagnostics suggest that the southerly surge plays a lateral forcing role in exciting the equatorial wave disturbance over the eio composite analyses of moisture flux and precipitation anomalies characterize the equatorial clockwise gyre as a convectively coupled equatorial rossby wave enhanced cross equatorial moisture transport due to the southerly surge appears to be linked to precipitation along the west coast of the southern indo china peninsula a case study of the southerly surge event during august 2000 illustrates the formation of the equatorial clockwise gyre and its convectively coupled equatorial rossby wave signature

the south indian convergence zone and interannual rainfall variability over southern africa abstract the south indian convergence zone sicz is identified in this paper as a region of enhanced precipitation extending off the southeast coast of southern africa during austral summer unlike the south pacific convergence zone the sicz is a land based convergence zone lbcz with position and intensity at least partially determined by surface conditions over southern africa an idealized gcm simulation is used to explore the basic dynamics of lbczs in the tropics and subtropics output from a realistic gcm simulation and the national centers for environmental prediction national center for atmospheric research 40 year reanalysis are analyzed to apply this basic dynamical framework to the case of the sicz in contrast to the intertropical convergence zone where column moisture convergence is primarily due to meridional wind convergence in the moist environment precipitation within the sicz and the lbczs in general is also supported by zonal wind convergence moisture convergence by transient eddy

overview of the meteorological conditions and atmospheric transport processes during indoex 1999 we give an overview of the regional meteorological situation during the indian ocean experiment indoex intensive field phase ifp in february and march 1999 the indoex domain reaching from 30 n to 30 s and from 50 e to 100 e was chosen because the low level outflow of pollution from india is carried by the northeasterly trades into the tropical convergence zone where cloud processing modifies the properties of the aerosols in contrast there is also an inflow of pristine southern hemispheric air by the southeasterly trades into the convergence zone however during the 1999 ifp some deviations from the climatological mean were observed in 1999 the intertropical convergence zone itcz was broken into a northern convergence zone and a southern convergence zone during february the northern zone was more active and the cross equatorial flow n s was weak both suggesting that less pollution was transported to the southern hemisphere in february it was occasionally possible to sample a southern hemispheric air mass on the southern side of the indoex domain during march 1999 the southern convergence zone became dominant and moved to a more southern position near 5 10 s it is shown that four channels carry pollution into the indoex domain 1 ne trades over the western arabian sea 2 nw ne flow along the west coast of india 3 ne trades over the west bay of bengal and 4 ne flow from se asia the strength of each channel is modulated by transients moving across pakistan and northern india western disturbances the heating of the indian subcontinent in march resulted in a eastern shift of the subtropical high from central india to the bay of bengal which also affected channels 2 3 and 4 episodes of high and low carbon monoxide concentrations as measured in kaashidhoo maldives during the 1999 ifp can qualitatively be explained by the operationality of the flow channels determined through trajectory analyses in combination with the intensity of the northern convergence zone

uplift and cooling magnetisation record in the bamble and telemark terranes sveconorwegian orogenic belt se norway and the grenville sveconorwegian loop article i nfo the 1100 ma sveconorwegian orogenic belt comprises allochthonous terranes juxtaposed by major fault zones and emplaced against and onto the south western margin of the fennoscandian shield to resolve the magnetic signature acquired during post orogenic uplift and cooling and evaluate wider correlations with the contemporaneous grenville belt of north america this study reports a regional palaeomagnetic study on a range of rock types from sectors of the medium high metamorphic grade bamble terrane 48 sites and 390 cores and the adjoining medium low grade telemark terrane 33 and 240 cores juxtaposed by an orogen parallel porsgrunn kristiansand fault zone with major vertical displacement magnetite and ilmeno hematites are magnetic carriers with the latter more significant in the higher metamorphic grades magnetic intensities are stronger in the higher grade terrane presumably due to the growth of metamorphic ferromagnets but are an order lower than values predicted for the lower continental crust and indicate that an additional mechanism is responsible for high magnetisations in deep crust anisotropy of magnetic susceptibility ams largely reflects the ne sw tectonic grain of the last stage of sveconorwegian ductile deformation the magnetisation record is filtered by excluding magnetisations possibly acquired during regional mesozoic dyke emplacement development of the permo carboniferous oslo rift and late proterozoic magmatism the remaining record is a dual polarity signature summarised by mean poles at 31 9 n 50 9 e n 191 components in the bamble terrane and at 34 2 n 58 9 e n 151 components in the telemark terrane however these means are non fisherian and embrace arcuate distributions of magnetic components acquired during protracted exhumation cooling of the orogen with the best defined parts

stratigraphical architecture at the muddy margin of the cretaceous western interior seaway southern utah the tropic shale and correlative tununk shale member of the mancos shale accumulated during cenomanian turonian time within prodeltaic environments near the western margin of the western interior seaway of north america stratigraphical and sedimentological analysis has revealed a detailed history of relative sea level change in the thick fine grained succession the tropic and tununk shales were deposited during the greenhorn second order sea level cycle over a time span of about 2 5 million years in southern utah six depositional sequences are superposed upon the record of this long term sea level change the sequences developed during third order relative sea level cycles of hundreds of thousands of years duration and are composed of at least 37 parasequences arranged in retrogradational aggradational and progradational parasequence sets the tropic shale and tununk shale member accumulated just basinward of the axis of maximum subsidence of a foreland basin stratal geometries and facies distribution patterns in the succession indicate that in southern utah the greenhorn cycle was tectonically controlled during the greenhorn transgression and highstand rapid rates of tectonic subsidence trapped terrigenous sediment to the west of the study area in the more proximal foreland at this time hemipelagic facies accumulated at relatively slow rates in southern utah and type 2 sequences developed during third order sea level cycles in contrast during the greenhorn regression rates of thrust induced subsidence in the proximal foreland basin evidently slowed and deltaic clinoforms prograded across the study area at least one forced regression occurred in southern utah at this time and type 1 sequences developed the formation of type 1 sequence boundaries in the upper part of the tropic shale and tununk shale member points to episodes of base level fall and indicates that the six third order sea level cycles recorded in the succession were not the result of changes in sediment supply alone the third order cycles may have been a consequence of episodic tectonism the timing of these cycles however suggests that development of sequences and parasequences in the tropic shale and tununk shale member may have been related to orbital forcing in the milankovitch band glacioeustasy or climatically related fluctuations in the amount of groundwater stored on continents may explain these high frequency sea level changes

palaeomagnetism of proterozoic dykes from bornholm denmark summary the island of bornholm denmark is a structural horst situated at a kink on the margin of and linking two major fault zones the sorgenfrei tornquist zone stz and the tornquist teisseyre zone ttz the fault zones of which separate the downfaulted danish polish basin from the baltic shield thirteen dolerite dykes out of a swarm of more than 200 all belonging to the supposed precambrian n s to ne sw striking dyke swarm on bornholm have been sampled and palaeomagnetically investigated the dykes vary in thickness between 0 2 and 60m and are intruded in precambrian gneisses and granites of gothian and or subjotnian 1 650 1280 ma age principal component analysis of detailed af and some thermal demagnetization experiments reveal three groups of stable direction clusterings from the dykes investigated the stable remanent magnetization of the major dyke keldse2 dyke and the baked gneiss contact corresponds to a palaeomagnetic mean pole group a comparing it with the apw curve for fennoscandia an initial cooling age for this dyke of around 1360 ma subjotnian age is suggested the result is confirmed by dual polarities and a positive baked contact test nine other dykes show a magnetization corresponding to a younger group of poles group b which cluster on the apw path around 1200ma jotnian age this result is also confirmed by a positive contact test two poles group c fall on the apw path around 950ma sveconorwegian age remaining directions display a distribution of poles on the sphere which suggest the presence of either late proterozoic cambrian overprints or injections of some younger dykes based upon a total of 16 bornholm dykes hitherto studied the polarity frequency ratio nir is 719 the remanent magnetizations and equivalent palaeomagnetic poles found in the bornholm dyke swarm thus appear to indicate at least three different periods of igneous activity with dyke injections in early proterozoic time for this otherwise homogeneously looking group of dykes from the margin of the baltic shield

crustal evolution of fennoscandia palaeomagnetic constraints abstract palaeomagnetic poles from fennoscandia ranging in age from archaean to tertiary are compiled and graded using a modified briden duff classification scale an new filtering technique is applied to select only the most reliable poles for analysis the filtering takes into account the following information 1 1 source block of rock unit 2 2 age of rock 3 3 age of magnetization component 4 4 scatter of palaeomagnetic directions 5 5 information from multicomponent analysis of natural remanent magnetization nrm 6 6 whether the pole considered belongs to a cluster or subcluster of poles 7 7 magnetic polarity and 8 8 the author s original assignment of results data are still insufficient for the drawing of separate apparent polar wander paths apwp for different blocks or cratons of fennoscandia treating fennoscandia as a single plate a new apwp from archaean to permian is constructed from the five previously drawn apwp loops or hairpins only one the jatulian loop 2200 2000 ma disappears in filtering the loops during 1925 1700 ma and during 1100 800 ma ago are linked to svecofennian and sveconorwegian orogenies respectively palaeomagnetic data support the concept that these orogenies took place episodically three distinct orogenic pulses early middle and late can be distinguished in the cluster plots of palaeopoles the drift history of fennoscandia from archaean to permian is presented during most of geological history fennoscandia has occupied low to moderate latitudes and undergone considerable latitudinal shifts and rotations the svecofennian and sveconorwegian orogenies have different kinematic characteristics during the svecofennian orogeny fennoscandia drifted slowly while rotating a large amount in an anticlockwise sense during the sveconorwegian orogeny it drifted rapidly and rotated first clockwise and then anticlockwise the most striking feature in the drift velocity curves is however the pronounced maxima in the latitudinal drift and rotation rates 9 cm yr and 0 8 ma respectively during the late subjotnian jotnian anorogenic magmatism and rifting phase 1450 1250 ma ago possibly reflecting the passage of fennoscandia across a thermal upwelling hotspot at equatorial latitudes the use of palaeomagnetism in delineating and dating movements between blocks is demonstrated with three examples from the polar profile area the northernmost section of the european geotraverse

determination of magnetic properties of rocks by analysis of demagnetization curves hematite ilmenite bearing rocks from sw sweden granulites from the high grade sveconorwegian corresponding to grenvillian gneiss terrane of sw sweden were investigated in order to relate magnetic properties to the granulite facies mineralogy and the amphibolite facies retrograde mineralogy we used standard paleomagnetic techniques susceptibility measurements electron and optical microscopy and a new way to analyze demagnetization curves based on vector difference sums the new technique allowed quantitation of the relative contributions of partial natural remanent magnetization nrm components as well as numerical extraction of thermal and coercive force alternating field af unblocking data two major components were identified one stable which is carried by hematite ilmenite and one less stable carried by multidomain md magnetite the age of the hematite ilmenite component is circa 930 ma and it has steep negative inclination coercivities in excess of 150 mt and unblocking temperatures between 540 degrees c and 640 degrees c two corresponding poles are reported 1 paleolatitude paleolongitude plat plong 218 degrees 24 3 with dp dm 9 4 degrees 9 9 degrees paleopole and 2 plat plong 203 degrees 51 degrees with d p d m 4 4 degrees 5 6 degrees vgp the md magnetite component is a recent or cretaceous paleogene steeply positive inclined nrm component associated with strong induced magnetization plat plong 2 degrees 74 degrees and d p d m 11 degrees 14 degrees vgp the md magnetite was unblocked at conditions of 6 40 mt and 60 400 degrees c our new analysis method was successful in showing that retrograde amphibole formation strongly decreases the importance of the hematite ilmenite component on behalf of the md magnetite it has a diminishing effect on a negative aeromagnetic anomaly in the area the 930 ma components constitute 80 0 of the vector difference sums depending on rock composition however as this fraction goes down to 60 the induced magnetization seems to outweigh the hematite ilmenite influence on aeromagnetic anomalies due to its opposite direction these rocks still have a strong and stable hematite ilmenite dominated nrm less

interactions between synoptic intraseasonal and interannual convective variability over southern africa after removing the annual cycle a principal component analysis is applied to the daily outgoing longwave radiation anomaly field used here as a proxy for atmospheric convection the analysis is carried out over the southern african region 7 5 e 70 e 10 s 40 s for austral summer november through february for the period 1979 1980 to 2006 2007 the first five principal components pc are retained the first two pcs describe spatial patterns oriented north west to south east from tropical southern africa sa to the mid latitudes they are interpreted to be different possible locations for synoptic scale tropical temperate troughs ttt one dominant rainfall producing synoptic system in the region the phase relationship between these two pcs describes a tendency for these ttt to propagate eastwards from sa to the mozambique channel and southern madagascar the next three pcs describe convective fluctuations respectively located over the north west the south and the centre of sa their time series are significantly associated with madden julian oscillation mjo activity in the tropics however we find that ttt systems are statistically independent of the mjo i e they are equally liable to occur during any phase of the mjo three pcs out of five also show a significant association with el nino southern oscillation confirming that el nino years mostly coincide with suppressed convection at the intraseasonal time scales a result consistent with its impact on seasonal averages diagnosed in previous studies

tropical extratropical interactions over southern africa three cases of heavy summer season rainfall abstract the synoptic evolution of three tropical extratropical te interactions each responsible for extreme rainfall events over southern africa is discussed in detail along with the consideration of previously studied events common features of these heavy rainfall producing tropical temperate troughs ttts over southern africa are discussed it is found that 2 days prior to an event northeasterly moisture transports across botswana set up by the angola low are diverted farther south into the semiarid region of subtropical southern africa the ttts reach full maturity as a te cloud band rooted in the central subcontinent which is triggered by upper level divergence along the leading edge of an upper tropospheric westerly wave trough convection and rainfall within the cloud band is supported by poleward moisture transports with subtropical air rising as it leaves the continent and joins the midlatitude westerly flow it is shown that these systems fit within a theoretical framework describing

recurrent daily olr patterns in the southern africa southwest indian ocean region implications for south african rainfall and teleconnections a cluster analysis of daily outgoing longwave radiation olr anomalies from 1979 to 2002 over the southern africa southwest indian ocean swio region for the november to february season reveals seven robust and statistically well separated recurrent patterns of large scale organized convection among them are three regimes indicative of well defined tropical temperate interactions linking the hinterland parts of southern africa to the mid latitudes of the swio preferred transitions show a tendency for an eastward propagation of these systems analysis of daily rainfall records for south africa shows that six of the olr regimes are associated with spatially coherent and significant patterns of enhanced or reduced daily rainfall over the country atmospheric anomalies from the ncep doe ii reanalysis dataset show that the olr regimes are associated with either regional or near global adjustments of the atmospheric circulation the three regimes representative of tropical temperate interactions being in particular related to a well defined wave structure encompassing the subtropical and temperate latitudes featuring strong vertical anomalies and strong poleward export of momentum in the lee of the location of the cloud band the time series of olr regimes seasonal frequency are correlated to distinctive anomaly patterns in the global sea surface temperature field among which are shown to be those corresponding to el nino and la nina conditions the spatial signature of el nino southern oscillation s enso influence is related to the combination of an increased decreased frequency of these regimes it is shown in particular that the well known dipole in convection anomalies contrasting southern africa and the swio during enso events arises as an effect of seasonal averaging and is therefore not valid at the synoptic scale this study also provides a framework to better understand the observed non linearities between enso and the seasonal convection and rainfall anomalies over the region