reappraisal of the palaeomagnetism of the miocene intramontane pag and drnis sinj basins external dinarides croatia abstract this paper presents palaeomagnetic results from the miocene offshore pag and the twin onshore drnis sinj basins earlier magnetostratigraphic results were published from both basins which documented that the lake sediments were good targets for palaeomagnetism from the pag basin we sampled the oldest and youngest segments of the 1200 m long crnika section and obtained statistically different palaeomagnetic directions from the two parts during a repeated visit to the section it was revealed that modern gravity driven creeping can account for this i e the results from the pag basin should be rejected from regional tectonic interpretation the overall mean palaeomagnetic direction for the drnis sinj basin has excellent statistical parameters its high quality is further supported by positive regional fold tilt and reversal tests based on seven geographically distributed localities the results suggests 13 20 ccw rotation with respect to africa and 21 27 with respect to stable europe during the last 15 million years as the external dinarides are the loci of a complicated network of miocene and even younger tectonic zones we cannot export the observed rotation for the whole unit but consider our results as one step in obtaining robust kinematic constraints for the post oligocene tectonic history of the external dinarides

a seismic study of deep geological structure in the bristol channel area sw britain summary results from eight seismic refraction lines 35 90 km long in the bristol channel area are presented the data mostly land recordings of marine shots have been interpreted mainly by ray tracing and time term modelling upper layer velocities through palaeozoic rocks usually fall within the range 4 8 5 2 km s 1 below the carboniferous limestone with a normal velocity of 5 1 5 2 kms 1 the old red sandstone with a velocity of 4 7 4 8 kms 1 acts as a low velocity layer as do parts of the underlying lower palaeozoic succession in the central south wales bristol channel area and the mendips a 5 4 5 5 km s 1 refractor is correlated with a horizon at or near the top of the lower palaeozoic succession under the whole area except for north devon a 6 0 6 2 km s 1 basal refractor has been located and is correlated with precambrian crystalline basement rocks in general this refractor deepens southwards from a series of basement highs which existed before the major movements of the variscan orogeny in south wales resulting in a southerly thickening of the pre upper carboniferous supra basement sequence in north devon a 6 2 km s 1 refractor at shallow depth interpreted as a horizon in the devonian or lower palaeozoic succession overlies a deep reflector that may represent the precambrian crystalline basement

structural geological factors in open pit coal mine design with special reference to thrusting case study from the ffyndaff sites in the south wales coalfield

paleomagnetism of the istria peninsula yugoslavia 280 core samples were collected from upper jurassic cretaceous and eocene sediments outcropping in the istria peninsula yugoslavia due to the very low intensities of the initial natural remanent magnetizations more than 50 of the collection consisting mainly of rock samples of jurassic and eocene sediments was not suitable for paleomagnetic studies the cretaceous samples yield a mean paleomagnetic pole lat 53 long 275 and 95 4 8 which is significantly different from the african and european paleomagnetic poles of the same age the position of the istria peninsula on the autochthonous adriatic platform allows the result to be interpreted as applicable to all the autochthonous periadriatic region this new paleomagnetic result indicates that the autochthonous adriatic platform rotated counterclockwise over an angle of about 30 with respect to africa in post mesozoic times

three dimensional computation of flow around groyne the three dimensional 3d numerical simulation of a steady shallow turbulent flow around a groyne in a rectangular channel is presented a method used to track a moving surface boundary and to follow its evolution using a one phase 3d reynolds solver with rigid grids by means of a transient fraction of fluid or porosity field is applied some results are compared with experimental data such as the isolines of water depths and the mean velocity field a comparison of the reattachment length prediction using the free surface model and the rigid lid assumption is given other results concerning the pressure field turbulence or shear stress distribution are presented and analyzed

upper cenomanian lower turonian sea level rise and its consequences on the adriatic dinaric carbonate platform the adriatic carbonate platform existed throughout most of the mesozoic as an isolated intraoceanic carbonate platform it is characterized by what has been traditionally labelled a continuous shallow marine carbonate sedimentation without terrigenous influences however global sea level changes left unequivocal imprints in the continuous carbonate record thus proving that the carbonate platform sensitively responded to sea level fluctuations this paper focuses on the relatively short cenomanian turonian drowning event which temporarily submerged the platform below the euphotic zone and which is related here to the well known global cenomanian turonian sea level highstand this drowning episode is characterized by the abrupt disappearance of numerous shallow water benthic invertebrate taxa and by an abundant occurrence of planktonic organisms including calcispheres and primitive planktonic foraminifera near the middle of the turonian the platform regime was re established correlating with the global fall in sea level the situation is different only at the south west margin of the platform where pelagic sedimentation initiated near the end of the cenomanian continues into the santonian and probably marks the adriatic trough the drowning began earlier in the middle cenomanian in those areas nearer to the north east margin of the platform the area of what is today central croatia and then progressed gradually towards the more interior areas of the platform the middle dalmatian islands which were drowned near the end of the cenomanian

mesozoic reactivation of variscan thrusting in the bristol channel area uk new seismic reflection data from the bristol channel area provide direct evidence of a major variscan thrust in the palaeozoic basement beneath the mesozoic bristol channel syncline the thrust has an average southerly dip of about 25 and it rises into the major fault the central bristol channel fault zone cbcfz at the northern margin of the bristol channel syncline the cbcfz is attributed to reactivation in extension of the variscan thrust probably during the early cretaceous there is no evidence for major synsedimentary movement on the cbcfz and the bristol channel syncline does not represent a rollover structure section restoration suggests that the cbcfz has cut up through a previously tilted sequence of triassic and jurassic strata pervasive nnw sse cross faults are interpreted as original variscan transfer faults that have been reactivated in the mesozoic and tertiary

discussion of separation zone in flow past a spur dyke on rigid bed meandering channel by kedar sharma and pranab k mohapatra

new cretaceous paleomagnetic results from the foreland of the southern alps and the refined apparent polar wander path for stable adria abstract the central western and the eastern southern alps are separated by the triangular shaped adige embayment which belongs to stable adria and was the site of pelagic sedimentation from the tithonian through maastrichtian the first part of this study presents paleomagnetic results from the tithonian cenomanian biancone and turonian maastrichtian scaglia rossa formations sampled at 33 geographically distributed and biostratigraphically dated localities the new and high quality paleomagnetic results from the adige embayment are then combined with coeval paleomagnetic directions from autochthonous istria marton et al 2008 which also belongs to stable adria the combined data set which for the late albian maastrichtian time period is constructed similarly to the synthetic african curve by besse and courtillot 2002 2003 reveals an important tectonic event late aptian early albian characterized by 20 ccw rotation and sedimentary hiatus comparison between paleomagnetic declinations inclinations expected in an african framework i e with the assumption that adria is still an african promontory leads to the following conclusions the time distributed tithonian and berriasian 150 135 ma paleomagnetic directions exhibit the african hairpin with an inclination minimum and a sudden change from cw to ccw rotation at 145 ma concerning the younger ages the declinations for adria continue to follow the african trend of ccw rotation till the end of cretaceous however the tithonian maastrichtian declination curve for stable adria is displaced by 10 from the african curve as a result of two rotations the first an about 20 cw rotation of adria with respect to africa took place between the maastrichtian and the mid eocene during this time the orientation of adria remained the same while africa continued its ccw rotation the younger rotation 30 ccw changed the orientation of adria relative to africa as well as to the present north

reappraisal of paleomagnetic data from gargano south italy vandenberg j 1983 reappraisal of paleomagnetic data from gargano south italy in e mcclelland brown and j vandenberg editors palaeomagnetism of orogenic belts tectonophysics 98 29 41 the platform limestones of apulia italy outcropping in the gargano peninsula have been restudied paleomagnetic research has been carried out on upper cretaceous lower cretaceous and jurassic rocks despite the low intensities of the nrm 10 100 pa m all samples 268 could be cleaned by stepwise a f and or thermal demagnetization treatments nrm directions could be determined accurately and reproducibly for 85 of the samples using a sct cryogenic magnetometer and double precision measuring procedures nrm of the jurassic limestone is carried by secondary haematite and the results are therefore rejected from further consideration the upper and lower cretaceous limestones have an nrm carried by magnetite minor bedding tilt corrections improve the grouping of the site mean results the upper cretaceous scaglia limestone turonian senonian reveals a characteristic mean direction of decl 327 7 incl 38 2o a ss 4 3 21 sites while the lower cretaceous maiolica limestone neocomian aptian albian reveals a characteristic mean direction of decl 303 1 o incl 35 1 as s 8 7o 8 sites the cretaceous results show a post aptian albian counterclockwise rotation of about 25 which is expressed by the smeared distribution of the late cretaceous site mean results and a post senonian i e tertiary counterclockwise rotation of the same amount with respect to the pole these results are in excellent agreement with contemporaneous paleomagnetic results from other peri adriatic regions a tertiary counterclockwise rotation of all the stable adriatic block is strongly supported by the new results

geodynamic evolution of the central dinarides abstract the central part of the dinarides unlike the northwestern and southeastern dinarides shows a consistent pattern in the distribution of the large tectonostratigraphic units from southwest apulia to northeast the following five main units originating in different parts of the mesozoic tethys can be distinguished 1 adriatic dinaridic carbonate platform formations 2 carbonate clastic units flysch bosniaque of the passive continental margin 3 ophiolite bearing formations of the dinaridic ophiolite zone also containing radiolarites greywackes and shales including melange formations and overstepped late jurassic to cretaceous cover sequences 4 active continental margin units represented by upper cretaceous palaeogene trench sediments with blueschists tectonized ophiolite melange alpine medium pressure metamorphic rocks originated from upper cretaceous palaeogene sediments and alpine synkinematic granitoids 5 a nappe consisting of allochthonous palaeozoic triassic formations which is thrust onto the ophiolites and genetically related sedimentary formations the frontal parts of this nappe directly overlie the northeastern margin of the adriatic dinaridic carbonate platform i e the external dinarides the evolution of the central dinarides was controlled by a sequence of tectonic events which took place within the alpine cycle 1 rifting processes lasting some 40 50 ma which started in the late permian and ended in the norian 2 opening of the oceanic dinaridic tethys commenced in the late triassic and persisted for some 70 80 ma until the end of the jurassic 3 subduction processes and emplacement of ophiolites started in late jurassic early cretaceous times during the closing phase of the dinaridic ocean or dinaridic tethys the palaeozoic triassic nappe was emplaced on the ophiolites the thrusting was accompanied by alpine metamorphism 120 100 ma 4 the main alpine deformational event and medium pressure metamorphism with synkinematic granite plutonism took place in late eocene early oligocene times when the ophiolite and palaeozoic triassic nappes were emplaced on the adriatic dinaridic carbonate platform which at the same time was deformed resulting in the development of the external dinarides fold and thrust belt

paleomagnetic and geochronologic constraints on the geodynamic evolution of the central dinarides the geodynamic evolution of the dinaride mountains of southeastern europe is relatively poorly understood especially in comparison with the neighboring alps and carpathians here we construct a new chronostratigraphy for the post orogenic intra montane basins of the central dinarides based on paleomagnetic and 40ar 39ar age data a first phase of basin formation occurred in the late oligocene a second phase of basin formation took place between 18 and 13 ma concurrent with profound extension in the neighboring pannonian basin our paleomagnetic results further indicate that the dinarides have not experienced any significant tectonic rotation since the late oligocene this implies that the dinarides were decoupled from the adjacent adria and the tisza dacia mega units that both underwent major rotation during the miocene the dinaride orogen must consequently have accommodated significant shortening this is corroborated by our ams data that indicate post middle miocene shortening in the frontal zone wrenching in the central part of the orogen and compression in the hinterland a review of paleomagnetic data from the adria plate which plays a major role in the evolution of the dinarides as well as the alps constrains rotation since the early cretaceous to 48 10 counterclockwise and indicates 20 of this rotation took place since the miocene it also shows that adria behaved as an independent plate from the late jurassic to the eocene from the eocene onwards coupling between adria and africa was stronger than between adria and europe adria continued to behave as an independent plate the amount of rotation within the adria dinarides collision zone increases with age and proximity of the sampled sediments to undeformed adria these results significantly improve our insight in the post orogenic evolution of the dinarides and resolve an apparent controversy between structural geological and paleomagnetic rotation estimates for the dinarides as well as adria

correction to apparent and true polar wander and the geometry of the geomagnetic field over the last 200 myr 1 in the paper apparent and true polar wander and the geometry of the geomagnetic field over the last 200 myr by jean besse and vincent courtillot journal of geophysical research 107 b11 2300 doi 10 1029 2000jb000050 2002 the data in the top part of table 4 were incorrect the correct table 4 is given here journal of geophysical research vol 108 no b10 2469 doi 10 1029 2003jb002684 2003

stratigraphy and paleoenvironments of rudist biostromes in the upper cretaceous turonian upper santonian limestones of southern istria croatia abstract rudists are well preserved in the upper cretaceous limestones of southern istria where they flourished within different shallow water environments during the turonian to upper santonian in order to determine paleoenvironments a vertical succession of the rich rudist assemblages has been investigated and described within sequence stratigraphy framework the turonian to upper santonian sediments of southern istria in the sense of sequence stratigraphy comprise one complete third order sequence and the beginning of the transgressive systems track tst of the next sequence lower turonian pelagic limestones were deposited on a foundered carbonate platform and represent the beginning of the tst limestones of the late tst lowstand systems track lst were deposited on the inner shelf and the early tst of the next sequence was deposited on the outer shelf all the rudists which appeared after the early turonian disappearance and partial extinction were elevators the genera durania and praeradiolites thrived in bouquets which may coalesce to form thickets in inner shelf environments of the late tst lst their growth depended completely durania or partly praeradiolites on net sediment accumulation the environment in which durania and praeradiolites thrived was subtidal and deep enough to be out of reach of emersion within the same depositional environment these genera were later replaced vertically by radiolites individuals with slim cylindrical shells and wide growth lamellae have full contact within the thickets in which their growth depended little if at all on net sedimentation rate also radiolites occupied the shallower parts of the subtidal zone with a commissure rim rising above the sediment surface renewed deepening in the late santonian resulted in the outer shelf environment of the next tst gorjanovicia together with rare vaccinites flourished after the radiolites gorjanovicia differed from radiolites only in possessing more pronounced vertical ribs in their slightly deeper subtidal environment with pelagic influxes gorjanovicia thrived in bouquets loosely packed gorjanovicia gave vaccinites an opportunity to grow among them the environmental setting of the southern istria rudist biostromes and their correlation with other shallow water deposits in the mediterranean region suggests that a sequence stratigraphy approach can be applied to correlate rudist biostratigraphy on a regional or even inter regional scale

new seismic evidence for a major geological boundary at shallow depth n devon recently acquired marine reflection data provide evidence for a major geological boundary at shallow depth under the southern bristol channel in the hangingwall block of the bristol channel thrust the boundary is recognized to equate with the top surface of a high velocity layer previously identified along refraction wide angle reflection seismic lines in the north devon area depth estimates from the reflection data and from a new interpretation of the earlier refraction data are combined to produce a contour map of the shallow boundary in the south central bristol channel and north devon areas the boundary has a wsw ene regional trend and lies at a depth of less than 2 km immediately north of the devon coast it is truncated to the north by the bristol channel thrust and deepens southwards across north devon and west somerset the boundary is interpreted as the top surface of a major litho stratigraphic unit older than the outcropping devonian sequence and in normal stratigraphic contact with it however in the absence of regional geological control the nature and age of the underlying high velocity layer remain uncertain

orogenic evolution of the external dinarides in the ne adriatic region a model constrained by tectonostratigraphy of upper cretaceous to paleogene carbonates abstract mesozoic to cenozoic evolution of the central part of the adriatic plate external dinarides and adriatic foreland is still a matter of debate this is expressed by opposing paleogeographic models single carbonate platform adriatic or adriatic dinaridic versus two carbonate platforms adriatic and dinaridic separated by the inter platform budva cukali basin estimates of shortening during adria ne subduction that resulted in the development of the dinaric alps differ substantially the single platform model involves minor shortening achieved by folding and faulting along steep reverse faults the two platform model involves significant shortening achieved mainly by thrust stacking which resulted in almost complete underthrusting of the intervening basinal deposits analysis of upper cretaceous to paleogene stratigraphical data from both outcrops and boreholes allows regional correlation and the interpretation of major lithostratigraphic units as a result a few tectonostratigraphic units are recognized the tectonostratigraphy is used as a basis for a new model on the late mesozoic to cenozoic evolution of the region generally adriatic and dinaridic segments acted as major regional crustal entities of adria the upper portions of the sedimentary cover were differentially affected by progressive southwestward verging thin skinned deformations during the paleocene to eocene miocene the adriatic foreland stayed out of the deformations and is characterized predominantly by wrench and salt tectonics the regional tectonic map shows arcuate thrust fronts of the external dinarides they could be a consequence of both differential propagation of early orogenic thin skinned deformations over crustal fragments separated by transversal faults and or differential isostatic movements of the fragments the collision zone of the adriatic and dinaridic segments is characterized by late orogenic oligocene to miocene thick skinned compressional uplift exhumation related gravity gliding and still active escape tectonics wrenching these processes masked primary thin skinned deformations a significant amount of shortening within and between the thin skinned sedimentary covers is proposed therefore the question of the general paleogeography of the region and the original nw extent of the budva cukali basin ne adriatic trough remains open

cretaceous palaeomagnetic results from murge apulia southern italy tectonic implications summary the adriatic area is of key importance in the reconstruction of the kinematic history of the mediterranean region concerning its relative position with respect to the african plate palaeomagnetic studies marton veljovic 1983 vandenberg 1983 have found evidence that autochthonous istria and gargano rotated counter clockwise with respect to africa after the cretaceous however the geodynamic role of the southern part of apulia has remained unclear in order to decide whether the boundary between the adriatic microplate and africa may be drawn between gargano and murge and whether the different parts of apulia could have undergone differential rotations after the cretaceous we carried out palaeomagnetic investigations in murge and the salentina peninsula in the field several carefully selected facies were collected and oriented with a magnetic compass at eight geographically distributed localities 46 sites 224 cores and 13 hand samples because of extremely weak nrm several sites failed to yield a meaningful palaeomagnetic signal this category comprises all sites younger than the turonian bauxite horizon and also six sites of cenomanian early turonian age samples from the remaining sites were subjected to detailed thermal and af demagnetization kirschvink 1980 and subtracted vector analysis and irm experiments including the thermal demagnetization of three component irm as a result we were able to demonstrate that some of the sites are devoid of overprint on the other hand there were sites with unremovable overprint the latter were rejected from tectonic evaluation despite the sometimes high degree of clustering of the individual nrms within a site so were those with unstable remanence eventually a cenomanian turonian palaeomagnetic mean direction was calculated for murge on a locality before tectonic correction d 327 i 44 k 55 95 17 n 3 after tectonic correction dc 327 ic 38 k 76 95 15 and a site before tectonic correction d 324 i 41 k 44 95 6 5 after tectonic correction dc 327 ic 40 k 42 95 6 7 basis and a palaeomagnetic pole latitude 56 longitude 261 was computed from the tectonically corrected locality mean direction since coeval palaeomagnetic poles for murge gargano and istria cluster we conclude that the stable part of the adriatic region moved in a highly integrated manner their displacement with respect to africa has manifested itself in a moderate ccw rotation since the turonian

palaeomagnetic evidence for tertiary counterclockwise rotation of adria abstract with the aim of obtaining tertiary palaeomagnetic directions for the adriatic foreland of the dinaric nappe system we carried out a palaeomagnetic study on platform carbonates from stable istria from the northwestern and the central dalmatia segment of imbricated adria despite the weak to very weak natural remanences of these rocks we obtained tectonically useful palaeomagnetic directions for 25 sites from 20 localities all exhibit westerly declinations both before and after tilt correction concerning the age of the magnetizations we conclude that five subhorizontal and magnetite bearing eocene localities from stable istria are likely to carry primary remanence whereas three tilted and hematite bearing ones were remagnetized in the northwestern segment of imbricated adria the cluster of the mean directions improved after tectonic correction indicating pre tilting magnetization in contrast maastrichtian eocene platform carbonates from central dalmatian were remagnetized in connection with the late eocene oligocene deformation or miocene hydrocarbon migration based on the appropriate site locality means we calculate mean palaeomagnetic directions for the above three areas and suggest an alternative interpretation of the data of kissel et al j geophys res 100 1995 14999 for the flysch of central dalmatia the four area mean direction define a regional palaeomagnetic direction of dec 336 inc 52 k 107 95 9 from these data we conclude that stable istria in close coordination with imbricated adria must have rotated by 30 counterclockwise in the tertiary relative to africa and stable europe we suggest that the latest miocene early pliocene counterclockwise rotations observed in northwestern croatia and northeastern slovenia were driven by that of the adriatic foreland i e the rotation of the latter took place between 6 and 4 ma

seismic refraction investigation of the structural setting of the lizard and start complexes sw england a long refraction line was established between the lizard and start peninsulas during a large scale seismic experiment carried out in sw england during 1979 interpretation of first arrival data indicates a shallow crustal structure consisting of two layers of regional extent the upper layer of average velocity 5 15 km s is interpreted as devonian metasediments the underlying layer with a velocity of about 6 10 km s lies at a depth of several kilometres beneath the lizard complex but rises eastwards to occur at or near surface in the eddystone and start areas the lower layer is believed to represent a pre devonian crystalline basement of which the metamorphic rocks of start and eddystone are constituent parts by contrast the lizard complex is interpreted as a thin surface sheet overlying devonian metasediments

the tectonic development of the northern adriatic region constrained by jurassic and cretaceous paleomagnetic results abstract in the northern adriatic region there is a clear boundary between the weakly deformed stable core of the adriatic microplate and its tectonically complicated ne margin the external dinarides which are further subdivided on stratigraphic and structural grounds although most authors distinguish an adriatic and a dinaridic realm within the external dinarides the relationship and the present boundary between the realms are matters of discussion the aim of this study was to obtain paleomagnetic directions from different parts of the northern adriatic segment of the external dinarides and discuss their bearing on the different types of the tectonic models for this purpose we carried out standard paleomagnetic measurements on biostratigraphically well controlled samples from 28 localities from the adriatic mainland and the northern adriatic islands and from one middle jurassic locality representing the stable core of the adriatic microplate in addition six localities from the northern adriatic islands earlier studied paleomagnetically were biostratigraphically updated and thus included in the data set for the northern adriatic islands an albian d i 333 48 k 44 95 9 and a cenomanian santonian d i 334 46 k 188 95 5 paleomagnetic direction was defined they are in perfect agreement with coeval paleomagnetic directions from stable adria thus the paleomagnetic data clearly support the models which conceive the area as the imbricated margin of the adriatic microplate the early d i 338 49 k 118 95 11 the middle d i 342 54 k 112 95 7 and the late d i 336 42 k 62 95 16 jurassic paleomagnetic directions all representing the tectonic units of the adriatic mainland suggest an about 30 cw rotation of this belt of the external dinarides with respect to stable adria the difference can be interpreted as inherited from the differencial rotations of two independent carbonate platforms an adriatic and a dinaric alternatively thrusting of the more internal belt of the external dinarides above the adriaticum may be responsible for the difference

new paleocene eocene paleomagnetic results from the foreland of the southern alps confirm decoupling of stable adria from the african plate abstract from the undeformed foreland of the southern alps paleocene through early miocene rocks mostly biostratigraphically well dated sediments with sub horizontal bed attitude were collected for a paleomagnetic study from 23 geographically distributed localities the samples were subjected to standard paleomagnetic measurements and evaluation while the miocene samples are unstable most of the older localities yielded statistically well defined paleomagnetic directions these are interpreted as primary for the compact marls supported by positive between locality tilt and reversal tests this large group of localities is characterized by ccw rotated declinations with respect to the present north combined with paleomagnetic directions of corresponding age from stable istria these allow definition of the apw for stable adria for the 61 6 33 9 ma interval which is significantly displaced from the coeval segment of the african apw due to the decoupling of the former to the latter by a moderate ccw rotation this post eocene final separation exact age is not constrained directly but estimated as end of miocene was preceded by a small cw rotation of adria with respect to africa suggested by unchanged orientation of the former across the cretaceous paleocene boundary while the latter continued its ccw rotation

apparent polar wander path for adria extended by new jurassic paleomagnetic results from its stable core tectonic implications abstract as a continuation of a systematic paleomagnetic research in the northern part of stable adria which provided a well defined apparent polar wander apw path for the cretaceous eocene we present new paleomagnetic results for the jurassic these new data were obtained from 15 geographically distributed localities from the trento platform eastern southern alps using standard paleomagnetic approach the lower jurassic shallow water carbonates are not considered for tectonic interpretation due to inconsistent inclinations the middle and upper jurassic rosso ammonitico provided excellent kinematic constraints with the new jurassic results an apw is now defined for adria for the 167 40 ma interval it is well constrained for timing of important changes like the speed and the sense of rotations this apw suggests that the cw rotation and southward shift changed to the opposite at 155 1 5 3 ma signifying a dramatic change in the life of the neo tethys from opening to closing the latter is manifested in fast ccw rotation and northward movement of adria up to 102 9 2 4 ma and moderate displacements in the same manner in post 103 ma times combined data sets from stable istria and the foreland of the southern alps point to an approximately 15 cw rotation with respect to africa at the end of the cretaceous and an about 25 in the ccw sense after the eocene

latitudinally different responses of tethyan shoal water carbonate systems to the early aptian oceanic anoxic event oae 1a ocean wide anoxic events represent intensively investigated anomalies in the global carbon cycle most previous research has focussed on hemipelagic and pelagic settings and on the relationship between black shale deposition and carbon isotope excursions the study of ocean wide anoxic events and coeval shallow water settings is now increasingly seen as an interesting complementary approach but one that is not without problems whereas platform drowning characterizes the early aptian of the northern tethyan margin lithocodium bacinella rich facies and ongoing shoal water sedimentation at the southern tethyan margin oman bears important information on potential causes of carbon cycle perturbations the present paper seeks to test the supra regional relevance of the oman data by investigating coeval central tethyan limestones three lower aptian shoal water sections in istria croatia deposited on the isolated adriatic carbonate platform are investigated applying chemostratigraphy carbon and strontium and detailed sedimentological analysis the focus is on peritidal to lagoonal facies characterized by mass occurrences of lithocodium bacinella an enigmatic microencruster community lithocodium bacinella facies occurs predominantly in layers ranging from one to several centimetres in stratigraphic thickness with several layers merging to metre thick packages growth fabrics within the layers include oncoidal morphotypes lumps interconnected patches and columns layers and rare nodular to massive bindstone facies these growth patterns show a remarkable regional extent and consistency over study sites distributed several kilometres apart this widespread distribution suggests that specific lithocodium bacinella morphotypes might serve as regional stratigraphic markers the high resolution carbon isotope chemostratigraphy presented here is based on pristine rudist shells and matrix micrite samples and calibrated against strontium isotope data obtained from screened rudist low mg calcite the chemostratigraphic data are consistent with existing biostratigraphic data and place the studied strata at the onset of early aptian oceanic anoxic event 1a moreover results indicate the near coeval nature of lithocodium bacinella bloom facies in istria and oman the outcomes of this study point to latitudinally different responses of tethyan shoal water carbonate systems platform drowning versus lithocodium bacinella blooms to the ocean wide anoxic event 1a

palaeomagnetism and rock magnetism of the permian redbeds from the velebit mt karst dinarides croatia dating of the early alpine tectonics in the western dinarides by a secondary magnetization abstract the studied area of the velebit mt a part of the adria microplate belonged to a ne margin of gondwana during the carboniferous and permian while the carboniferous to the early permian was characterised by deposition of clastic rocks younger sedimentation was dominated by a thick sequence of carbonate rocks the lower permian deposits of the core part of the velebit mt at kosna and crne grede localities were investigated using palaeomagnetic and rock magnetic measurements the main remanence carriers were recognized as haematite with an increasing contribution of sp sd magnetite in younger subsections the ams fabric with low anisotropy ratio 1 3 is strongly oblate at kosna and weakly prolate at crne grede reflecting differences in the contribution of magnetic phases a significant remagnetization of the permian rocks as proved by results of a conglomerate test probably caused by a combination of elevated temperatures and fluid migration may be assigned to burial related processes that affected the rocks before the final uplift of the dinarides characteristic remanent magnetizations recorded in haematite are apparently similar to the permian direction for africa shallow inclination with nnw declination as expected for velebit mt coordinates paradoxically this orientation is observed in situ within the almost vertically dipping beds we explain this relationship assuming a syn folding cretaceous remagnetization of the rocks at their subhorizontal position ca 30 s in which a mean vector of the secondary remanence overlaps with the cretaceous direction expected for africa at the velebit mt geographical coordinates consequently our results indirectly point to the cretaceous time of incipient stages of the dinaric tectonism and suggest african geotectonic affinity of the velebit rocks no important vertical axis rotation is implied by our results in contrast to previously published data the puzzling complete remagnetization carried by haematite at relatively low to moderate temperatures is also discussed

possible variscan thrusting beneath the somerton anticline somerset vibroseis seismic data were acquired by goal petroleum plc during 1982 in the vicinity of the somerton anticline somerset these data show the simple form of the anticline but in addition show a southward dipping discontinuous seismic event beneath gravity modelling demonstrates that this event may be correlated with an e w trending gravity gradient which can be followed for approximately 150 km the dipping seismic event may represent a variscan thrust plane which dips to the ssw in contrast to similar planes seen to the east which dip to the sse the variation in dip seen between these postulated thrust planes may explain the curvature of structural trends seen within and to the east of the mendip hills the polden hills fault runs sub parallel to the proposed thrust plane beneath the somerton anticline and may be linked to a mesozoic reactivation of the postulated thrust

evolution of the adriatic carbonate platform palaeogeography main events and depositional dynamics abstract the adriatic carbonate platform adcp is one of the largest mesozoic carbonate platforms of the perimediterranean region its deposits comprise a major part of the entire carbonate succession of the croatian karst external or outer dinarides which is very thick in places more than 8000 m and ranges in age from the middle permian or even upper carboniferous to the eocene however only deposits ranging from the top of the lower jurassic toarcian to the top of the cretaceous can be attributed to the adcp defined as an isolated palaeogeographical entity although the entire carbonate succession of the karst dinarides was deposited within carbonate platform environments there were different types of carbonate platforms located in different palaeogeographical settings carboniferous to middle triassic mixed siliciclastic carbonate deposits were accumulated along the gondwanian margin on a spacious epeiric carbonate platform after tectonic activity culminating by regional middle triassic volcanism recorded throughout adria the african promontory a huge isolated carbonate southern tethyan megaplatform abbreviated as stm was formed with the area of the future adcp located in its inner part tectonic disintegration of the megaplatform during the middle to late early jurassic resulted in the establishment of several carbonate platforms including the adriatic apenninic and apulian separated by newly drowned deeper marine areas including the adriatic basin as a connection between the ionian and belluno basins lagonero basin and the area of the slovenian and bosnian troughs the adcp was characterised by predominantly shallow marine deposition although short or long periods of emergence were numerous as a consequence of the interaction of synsedimentary tectonics and eustatic changes also several events of temporary platform drowning were recorded especially in the late cretaceous when synsedimentary tectonics became stronger leading up to the final disintegration of the adcp the thickness of deposits formed during the 125 my of the adcp s existence is variable between 3500 and 5000 m the end of adcp deposition was marked by regional emergence between the cretaceous and the palaeogene deposition during the palaeogene was mainly controlled by intense synsedimentary tectonic deformation of the former platform area some carbonates mostly eocene in age were deposited on irregular ramp type carbonate platforms surrounding newly formed flysch basins and the final uplift of the dinarides reached its maximum in the oligocene miocene the adriatic carbonate platform represents a part although a relatively large and well preserved one of the broader shallow water carbonate platform that extended from ne italy to turkey although its continuity is somewhat debatable in the area near albanian greece boundary this large carbonate body which was deformed mostly in the cenozoic including a significant reduction of its width needs a specific name and the central mediterranean carbonate platform is proposed abbreviated to cmcp although the local names such as adcp for its nw part should be kept to enable easier communication and to facilitate description of local differences in platform evolution

variscan structure of the inner bristol channel uk major variscan structures under the bristol channel are concealed beneath a mesozoic and quaternary cover mapping of reflectors on offshore seismic sections reveals two major wnw ese striking thrusts within the underlying palaeozoic sequence the more southerly with a moderate ssw dip has previously been identified as the bristol channel thrust another thrust the previously undescribed gravel margin thrust has been identified in the eastern part of the inner bristol channel and lies in the footwall of the bristol channel thrust it has a similar strike but steeper dip and extends to anticipated precambrian basement depths the bristol channel and gravel margin thrusts together juxtaposed the contrasting palaeozoic successions of south wales and sw england before mesozoic reactivation reflection packages identified on the offshore seismic sections are tentatively correlated with specific onshore palaeozoic sequences interpretation of the offshore seismic sections in conjunction with geological mapping along the north devon coast shows that the bristol channel and gravel margin thrusts have orientations and geometries typical of several mesoscale thrusts observed and measured at foreland point north devon along strike structural changes beneath the inner bristol channel seen on seismic sections provide evidence additional to earlier refraction and structural studies for the offshore continuation of the nw se trending watchet cothelstone hatch fault and its linkage with the previously described central bristol channel fault zone the bristol channel and gravel margin thrusts are interpreted to be offset from the cannington park thrust in north somerset by a 14 16 km variscan dextral strike slip displacement across the watchet cothelstone hatch fault the bristol channel gravel margin thrust and the cannington park thrust are interpreted as syngenetic structures linked by their lateral ramp the watchet cothelstone hatch fault using all the above information the overall structure of the variscides of the inner bristol channel is re evaluated and a new tectonic model is presented the structures discussed in this paper at a scale portrayed by commercial seismic data and published geological maps may represent merely the tips of linked thrusts that have previously been mapped down to mid crustal depths on birps seismic sections from the south west approaches traverse we show that enough data now exist to resolve outstanding problems of the concealed variscan structure in the inner bristol channel providing local structural detail that can be incorporated into the wider tectonic framework of nw europe

magnetostratigraphic dating of shallow water carbonates from san salvador bahamas magnetostratigraphic results are reported here from a sequence of late neogene quaternary shallow water carbonate sediments from a continuous core drilled on the island of san salvador bahamas on the basis of the remanent magnetism of 136 samples from a 91 m measured section of core the polarity sequence can be correlated with the magnetic polarity time scale from the gilbert chron early pliocene through the late brunhes chron late pleistocene holocene magnetic polarities were determined on the basis of relative up down direction in the unoriented core extraction studies of the magnetic particles reveal the presence of single domain crystals of magnetite resembling those produced by the magnetotactic bacteria and algae the sequence of reversals provides a minimum of six new major chronostratigraphic markers for the pliocene pleistocene of the bahamas it confirms and refines the local timing of both the lithologic change from skeletal to nonskeletal sediments and the disappearance of coral and molluscan species from the bahamas as upper late pliocene between 2 6 and 2 7 ma that the primary magnetic remanence is preserved in shallow water carbonates including replacement dolomites suggests that this technique could be used to date similar tertiary and possibly even older carbonate sequences the establishment of a reliable magnetostratigraphy provides refined dating of shallow water carbonates and regional faunal appearances or disappearances sediment accumulation rates subsidence and depositional events

paleomagnetism of aptian albian sections from the northern apennines italy implications for the 150 100 ma apparent polar wander of adria and africa abstract we computed a new 120 to 100 ma high resolution apparent polar wander path apwp for adria from magnetostratigraphic studies in the northern apennines italy we analyzed 274 cores from three early aptian late albian sections of the marne a fucoidi fm belonging to the sedimentary succession deposited above the adria passive margin during meso cenozoic time to solve the problem of tectonic rotations induced during the apennine orogenesis we computed relative rotations between sections and realigned them into a common declination reference frame bosso italy these new data were added to the previous 150 125 ma segment computed from the same region satolli s besse j speranza f calamita f 2007 new 125 150 ma high resolution apparent polar wander path for adria from magnetostratigraphic sections in umbria marche northern apennines italy timing and duration of the global jurassic cretaceous hairpin turn earth planet sci lett 257 329 342 doi 10 1016 j epsl 2007 03 009 to get a very high resolution 100 to 150 ma apwp for adria the comparison of our apwp with the african apwp segment of besse and courtillot computed with 10 myr sliding window besse j courtillot v 2002 apparent and true polar wander and the geometry of the geomagnetic field over the last 200 myr j geophys res 107 doi 10 1029 2000jb000050 leads to the following conclusions 1 our segment after a 25 clockwise rotation of the bosso reference frame is in very good agreement with the african apwp as shown by a very similar time evolution of inclinations and declinations most often statistically indistinct 2 this agreement vindicates our previous model of structural unit rotation for older periods satolli s besse j speranza f calamita f 2007 new 125 150 ma high resolution apparent polar wander path for adria from magnetostratigraphic sections in umbria marche northern apennines italy timing and duration of the global jurassic cretaceous hairpin turn earth planet sci lett 257 329 342 doi 10 1016 j epsl 2007 03 009 3 the concept of synthetic apwp construction is strongly validated 4 the good agreement found strengthens the fact that adria has been a promontory of africa at the lithospheric level during late jurassic early cretaceous 150 100 ma affected by tectonic rotations linked to the apennines orogenic phases during neogene 5 our data evidence a possible ca 105 ma southward motion of adria undetected from classical african apwps finally we have not found evidence for reversals interrupting the long normal cretaceous superchron in our sections

scale effects in flume experiments on flow around a spur dike in flatbed channel this paper presents the findings from a series of flume experiments conducted to determine scale effects in small scale models of flow around a single spur dike wing dam groyne or abutment placed in a channel whose bed is fixed and flat the flow features of primary interest are flow thalweg alignment line of maximum streamwise velocity around a dike and area extent of the flow separation region wake immediately downstream of the dike those features are of practical concern in the deployment of dikes for various channel control purposes the scale effects of concern herein are those attributable to use small length scales together with a bed shear stress parameter e g shields parameter as the primary criterion for dynamic similitude small scale models especially micromodels often are used for investigating channel control issues also the shear stress criterion is commonly used for models of flow in loose bed channels whereas froude number commonly is the primary similitude criterion for models of fixed bed open channel flows the experiments show that use of a shear stress parameter as the primary criterion for dynamic similitude influences the flow thalweg and flow separation region at a dike it does so by distorting pressure gradients around the model dike and by affecting turbulence generated by the dike it also is shown that for a range of small models thalweg alignment and extent of separation region do not scale with model length scales these findings are important for interpreting results from small hydraulic models especially micromodels of flow in loose bed channels

coupled crust mantle response to slab tearing bending and rollback along the dinaride hellenide orogen we integrate structural geophysical and geodetic studies showing that the dinarides hellenides orogen along the adria europe plate boundary in the western balkan peninsula has experienced clockwise oroclinal bending since eocene oligocene time rotation of the hellenic segment of this orogen has accelerated since the middle miocene and is associated with a north to south increase in shortening along the orogenic front within the paleogene nappe pile bending was accommodated by orogen parallel extension clockwise block rotation and thrusting in the hanging wall of the skhoder peja normal fault spnf the spnf and related faults cut the older skhoder peja transfer zone with its pre neogene dextral offset of the west vardar ophiolite nappe rotation of the spnf hanging wall involved miocene to recent out of sequence thrusting that was transferred to the hellenic orogenic front via lateral ramps on dextral transfer zones along strike of the dinarides hellenides and coincident with the southward increase in neogene shortening the depth of the adriatic slab increases from 160 km north of the spnf to 200 km just to the south thereof to several hundreds of kilometers to the south of the kefalonia transfer zone the geodynamic driver of tectonics since the early miocene has been enhanced rollback of the hellenic segment of the adriatic slab in the aftermath of eocene oligocene slab tearing and breakoff beneath the dinarides which focused slab pull in the south the sw retreating hellenic slab segment induced clockwise bending of the southern dinarides and northern hellenides including their adriatic foreland about a rotation pole in the vicinity of the mid adriatic ridge

late carboniferous tectonic subsidence in south wales implications for variscan basin evolution and tectonic history in sw britain detailed stratigraphic data have been used to backstrip seven sections from the carboniferous south wales coal basin resulting tectonic subsidence curves for the interval 319 305 ma namurian westphalian d are convex up indicating increasing subsidence rate with time with rates between 130 and 250 m ma 1 suggesting a foreland basin setting forward modelling of subsidence due to flexural loading in front of a propagating orogenic wedge shows that an orogenic load migrating in a north northeasterly direction across sw england between 319 and 305 ma could have generated the backstripped subsidence patterns sensitivity tests show that while many of the forward model parameters are poorly constrained and the model results non unique backstripped subsidence patterns allow reasonable constraint on the different model cases so that model predictions can be treated as one possibility in a limited range the predicted load evolution is consistent with current knowledge of tectonic and stratigraphic features of sw england these results suggest that subsidence in other late carboniferous uk basins may also have been influenced by flexure due to a propagating orogenic load

paleoecology and proliferation of the bivalve chondrodonta joannae choffat in the upper cenomanian upper cretaceous adriatic carbonate platform of istria croatia abstract chondrodonta joannae choffat is a morphologically variable oyster like bivalve with a predominately calcitic shell an exceptional exposure of c joannae bearing strata of late cenomanian age crops out along the seaside in northern istria croatia and permits a taphonomical and functional analysis in order to define the life habit and growth strategies of this bivalve the c joannae population from the studied succession is characterized by highly elongated large and curved shells reaching about 50 cm in height and 5 cm in length this shell shape is typical of the club like bivalve morphotype which was adapted to soft bottom substrates with high sediment accumulation the shell is slightly inequivalve and characterized by a reduced body cavity a few centimetres high and a dorsal region up to 10 times longer the shell opening mechanism was mostly based on the resilium located between the chondrophores which protrude in the body cavity the abandoned dorsal cavity is filled by a calcite hinge plate the ventral edge of which acted as fulcrum for the valve flexibility in the hinge plate the function of chondrophores changed they acted as a hinge to keep tightly interlocked the valves which considerably emerged above the sediment water interface the individuals were arranged in low shrub type congregations which produced low relief mounds the functional morphology and taphonomic signature suggest that c joannae individuals collected food at a greater distance from the bottom with respect to the co occurring rudists we speculate that the c joannae proliferation could be related to a late cenomanian phase of environmental instability predating the oae2 with fluctuating climatic conditions and ocean fertility

new stepping stones dugi otok and vis islands in the systematic paleomagnetic study of the adriatic region and their significance in evaluations of existing tectonic models abstract the external dinarides from which several conflicting tectonic models were published are the more tectonized ne margin of autochthonous adria dugi otok and vis islands belong to this margin from the two islands a new paleomagnetic study is presented based on 48 geographically distributed and biostratigraphically controlled cretaceous carbonate sediment localities the results suggest that the two islands certainly moved in co ordination after the mid albian which was the time of resumed sedimentation after a period of emersion although some relative movement could have occurred earlier the new post aptian paleomagnetic results are in perfect agreement with recently published paleomagnetic results from stable adria and from the more northerly adriatic islands this consistency suggests that all these areas moved together from the albian on while the coastal range of the external dinarides seems to have moved independently thus autochthonous adria together with the adriatic islands is established as a crustal block within the central mediterranean region which rotated significantly in ccw sense in post cretaceous times

the motion of adria during the late jurassic and cretaceous new paleomagnetic results from stable istria abstract the motion of adria the largest lithospheric fragment in the central mediterranean region has played an important role in the tectonic development of the surrounding mountain chains and even of distant areas like the eastern alps or the pannonian basin the available paleomagnetic data were insufficient to constrain this motion except in a general way in this paper new paleomagnetic results are presented from one of the stable parts of adria which emerge from the adriatic sea the results were obtained on weakly magnetic platform carbonates of the mud supported type collected from 21 geographically distributed localities the results combined with mean paleomagnetic directions from selected localities from a pioneer study in istria that were chosen using statistical criteria were divided into three age groups tithonian aptian albian cenomanian turonian coniacian the paleomagnetic poles calculated for each of them tithonian aptian n 47 e 275 k 67 95 9 4 n 5 albian cenomanian n 58 e 253 k 145 95 4 3 n 9 turonian coniacian n 63 e 261 k 50 95 7 3 n 9 reveal a moderate shift during the cretataceous which is comparable with that calculated from the african reference poles however the istrian apparent polar wander path is slightly displaced from the african curve as a consequence of about 10 counterclockwise rotation of istria with respect to africa this rotation angle is more that 10 smaller than the difference measured for the mid late eocene between the paleomagnetic direction of platform carbonates from istria and the african reference direction this difference may be the consequence of a small clockwise rotation of istria with respect to africa most probably at the end of cretaceous

the direction correction tilt test an all purpose tilt fold test for paleomagnetic studies abstract the tilt or fold test in paleomagnetism is used to infer whether paleomagnetic remanence was acquired before or after tectonic tilting while several tilt test formulations have been proposed none fully satisfies the requirements of statistical validity applicability to all bedding geometries and ease of use this paper introduces the direction correction dc test which examines the relationship between the paleomagnetic site mean directions and their corresponding bedding tilt corrections the dc test is similar to mcfadden s correlation test because both test whether or not the site directions contain information about the bedding tilts however the dc test gives greater weight to sites with greater counter bedding the dc test is similar to watson s numerical tilt tests because they determine the degree of untilting which gives optimal concentration of site directions however the dc test uses analytical rather than numerical methods graphical output aids the researcher in recognizing problem sites using both real and simulated data the dc test is demonstrated to be more discriminating than other tilt test formulations for all bedding geometries the simulations show that the power of the tilt test is inversely proportional to the 95 confidence interval 95 of the overall mean as a rule of thumb paleomagnetists should attempt to sample sufficient sites to obtain an 95 less than 1 6 of the bedding attitude difference