paleogene igneous underplating and subsidence anomalies in the rockall faeroe shetland area abstract crustal thickening caused by igneous underplating related to continental break up in the northeast atlantic has been invoked as the cause of the apparent lack of thermal subsidence seen in many mesozoic basins in the northwest european area in this study we examine a set of commercial wells in the rockall faeroe shetland region and calculate tectonic subsidence histories the rate of post rift basement subsidence during the cretaceous cenozoic determined from backstripping calculations always implies a higher degree of extension than the total basement subsidence assuming uniform extension furthermore the size of this discrepancy increases northward along the rockall trough and westwards in the northern north sea towards scotland we interpret this depth anomaly to reflect the effect of igneous underplating rethickening the crust following mesozoic and cenozoic extension late paleocene extension is identified in subsidence reconstructions throughout the west of britain area and is greatest in the rockall trough assuming that the underplating is gabbroic in composition the subsidence depth anomalies indicate a regional pattern of 2 3 km underplated between the erris trough and porcupine basin increasing to 4 5 km in the west lewis basin and hebrides shelf area in the faeroe shetland basin underplating is 1 0 1 5 km in the east and increases to 4 5 km in the west the data support the hypothesis of a major asthenospheric thermal anomaly centered under the faeroes in the paleocene dynamic uplift of the region is often difficult to identify but is locally seen to develop rapidly around 63 ma implying rapid emplacement of the mantle anomaly the intrusion of gabbroic bodies to the base of the crust in the late paleocene may have had an impact on the thermal maturation of petroleum source rocks in the region however thermal maturity indicators show smaller peak heatflows than predicted from simple thermal models suggesting that underplating was a gradual process achieved through the accretion of several small rapidly cooled bodies

palaeoenvironment of braided fluvial systems in different tectonic realms of the triassic sherwood sandstone group uk abstract fluvial successions comprising the fills of sedimentary basins occur in a variety of tectonic realms related to extensional compressional and strike slip settings as well as on slowly subsiding passive basin margins a major rifting phase affected nw europe during the triassic and resulted in the generation of numerous sedimentary basins in the uk much of the fill of these basins is represented by fluvial and aeolian successions of the sherwood sandstone group additionally regions that experienced slow rates of mesozoic subsidence unrelated to triassic rifting also acted as sites of accumulation of the sherwood sandstone group one well exposed example being the eastern england shelf the fluvial depositional architecture of deposits of the sherwood sandstone group of the eastern england shelf a shelf edge basin is compared with similar fluvial deposits of the st bees sandstone formation eastern irish sea basin a half graben the two studied successions represent the preserved deposits of braided fluvial systems that were influenced by common allogenic factors climate sediment source delivery style differences in preserved sedimentary style principally reflect their different tectonics settings analysis of lithofacies and architectural elements demonstrates that both studied successions are characterized by amalgamated channel fill elements that are recorded predominantly by downstream accreting sandy barforms the different tectonic settings in which the two braided fluvial systems accumulated exerted a dominant control on preserved sedimentary style and long term preservation potential on the eastern england shelf the vertical stacking of pebbly units and the general absence of fine grained units reflect a slow rate of sediment accommodation generation 18 19 4 m myr in this shelf edge basin successive fluvial cycles repeatedly reworked the uppermost parts of earlier fluvial deposits such that only the lowermost channel lags tend to be preserved by contrast in the eastern irish sea basin of west cumbria the rate of sediment accommodation generation was substantially greater 119 m myr such that space was available to preserve complete fluvial cycles including silty drape units that cap the channelized deposits

relating cenozoic north sea sediments to topography in southern norway the interplay between tectonics and climate abstract about 482 000 km 3 of sediment ca 24 m ma accumulated in the north sea during the cenozoic early cenozoic sedimentation was likely due to uplift of the circum north atlantic landmasses related to continental break up kilometre scale transient uplift and in some areas permanent uplift generated sources for progradational influx of clastic sediments from scotland the shetland platform and to a lesser degree southwestern norway the eocene sedimentation pattern was similar to the palaeocene with lower rates of accumulation associated with flooding and tectonic quiescence sediment influx from the shetland platform continued throughout the cenozoic while supply from southern norway increased markedly around the eocene oligocene coeval with the greenhouse icehouse transition mass balance calculations of sediment and eroded rock volumes suggest that while some topography along the western margin of norway may be pre cenozoic significant uplift of the main paleic surface in southern norway occurred around the early oligocene sedimentation rates were almost ten fold higher than the cenozoic average in the plio pleistocene slightly higher than the global average mass balance calculations indicate that plio pleistocene erosion over deepened a pre existing topography

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

synergistic approach for mapping debris covered glaciers using optical thermal remote sensing data with inputs from geomorphometric parameters abstract debris cover on glacier boundaries critically impedes the global inventorying of glaciers and confounds most of the techniques developed for semi automated mapping of glaciers debris on the glacier referred as supraglacial debris and that occurring outside the glacier boundaries referred as periglacial debris being derived from a common source i e the valley rock tend to have a similar spectral response in the reflection region which renders them mutually indistinguishable however there exist temperature differences between them this aspect has been considered in this remote sensing based study to distinguish between the supraglacial and periglacial debris in a test area in the chenab basin himalayas by inclusion of thermal infrared tir bands in remote sensing data processing a synergistic multisensor approach for the delineation of debris covered glacier boundaries is used here which integrates the inputs from thermal terra aster sensor and optical irs p6 awifs sensor remote sensing data multispectral classification techniques and the dem derived geomorphometric parameters the results of this study corroborate earlier findings on utilization of temperature differences as one of the parameters in glacial studies the proposed synergistic approach therefore appears useful in accurate mapping of debris covered glaciers in the himalayan region

the morphology of permian palaeodunes a reinterpretation of the bridgnorth sandstone around bridgnorth england in the light of modern dune studies abstract an examination of the permian bridgnorth sandstone formation around bridgnorth shropshire has indicated that it probably accumulated in a combination of transverse and barchanoid draas with superimposed oblique crescentic and linear dunes under the influence of a fluctuating wind regime three major recurrent facies associations were identifiable isolated transverse draa with superimposed oblique crescentic and linear dunes barchanoid draa with superimposed oblique crescentic and linear dunes and bimodal sand sheets with isolated dome dunes the overall long term wind direction was probably from the east and appears to have controlled draa orientation the orientations of the superimposed dunes however were probably related to medium term wind fluctuations from a more northerly quarter possibly modified by the draa bedforms short term wind reversals may have reworked slipfaces as shown by the presence of internal scour surfaces within dune and draa foresets

the composition and structure of volcanic rifted continental margins in the north atlantic further insight from shear waves abstract imaging challenges caused by highly attenuative flood basalt sequences have resulted in the understanding of volcanic rifted continental margins lagging behind that of non volcanic rifted and convergent margins massive volcanism occurred during break up at 70 of the passive margins bordering the atlantic ocean the causes and dynamics of which are still debated this paper shows results from traveltime tomography of compressional and converted shear wave arrivals recorded on 170 four component ocean bottom seismometers along two north atlantic continental margin profiles this traveltime tomography was performed using two different approaches the first a flexible layer based parameterisation enables the quality control of traveltime picks and investigation of the crustal structure the second with a regularised grid based parameterisation requires correction of converted shear wave traveltimes to effective symmetric raypaths and allows exploration of the model space via monte carlo analyses the velocity models indicate high lower crustal velocities and sharp transitions in both velocity and vp vs ratios across the continent ocean transition the velocities are consistent with established mixing trends between felsic continental crust and high magnesium mafic rock on both margins interpretation of the high quality seismic reflection profile on the faroes margin confirms that this mixing is through crustal intrusion converted shear wave data also provide constraints on the sub basalt lithology on the faroes margin which is interpreted as a pre break up mesozoic to paleocene sedimentary system intruded by sills

late miocene high and rapid surface uplift and its erosional response in the andes of central chile 33 35 s 1 we address the question of the late cenozoic geomorphological evolution of the central chile andes 33 35 s using uplift markers river incision previous and new ages of volcanic bodies and new fission track ages the uplift markers consist of relicts of high elevated peneplains that evidence 2 km of regional surface uplift lasting 2 ma with variable amount along an e w transect the eastern coastal cordillera was uplifted 1 5 2 1 km at 33 34 s and 2 5 at 33 45 s and 1 5 km at 34 30 s erosional response to uplift was characterized by the retreat of a sharp knickpoint with celerities between 10 and 40 mm a 1 extrapolation using a stream power law shows that uplift began shortly before 4 ma or at 10 5 4 6 ma 7 6 ma central age depending on the morphostructural units involved the first alternative implies simultaneous uplift of the continental margin the second model the most reliable one implies that the uplift affected together the eastern coastal cordillera and the principal cordillera while the rest of the western fore arc subsided this regional uplift can be mostly balanced by crustal thickening resulting from coeval shortening related to the out of sequence thrusting event in the principal cordillera and the uplift of the frontal cordillera simultaneously emplacement of the southern edge of the flat slab subduction zone might have partially contributed to this uplift event

lithofacies and cyclicity of mohilla evaporite basins on the rifted margin of the levant in the late triassic makhtesh ramon southern israel marine connected basins with evaporites occur beneath most extensional continental margins that originated at low latitudes and often are of major economic significance cyclicity in the evaporite lithofacies reflects the degree of restriction of the basin overprinted by sea level changes and caused by structural movements in the barrier region whether by fault block rotation footwall uplift or hanging wall subsidence in both extensional and compressional basins the upper triassic evaporites of the ramon section in southern israel model cyclic sedimentation in such environments the mohilla formation is a carbonate evaporate siliciclastic succession of carnian age that fills a chain of basins extending along the levant margin from southern israel to jordan and syria the basins developed in half grabens adjacent to normal faults that formed during a period of regional extension evaporites of this formation are well exposed in outcrops at makhtesh ramon the southernmost of these basins the m2 member of the mohilla formation is composed of 42 sub metre cycles of alternating dolostone gypsum and calcareous shales field and microfacies analysis showed these cycles to conform mostly to restricted shallow and marginal marine environments spatially limited by the uplifted shoulders of the half graben systems a total of 10 facies types belonging to six depositional environments have been identified from stacking patterns and analysis of bed to bed change cycles can be categorized into three groupings i low frequency exposure to exposure cycles that developed under eustatic or climate control ii high frequency deepening shallowing upward cycles characterized by gradual transitions due to short term sea level or runoff event oscillations possibly referable to orbital forcing and iii high frequency shallowing upward cycles characterized by abrupt transitions attributable to sporadic tectonic events affecting accommodation space or barrier effectiveness the way facies and cycling of the sedimentary environments was deciphered in the mohilla evaporite basin can be used to unravel the genesis of many other evaporite basins with barriers of tectonic origin

normal fault growth and fault related folding in a salt influenced rift basin south viking graben offshore norway abstract three dimensional seismic data were analysed to reconstruct the structural and stratigraphical development of a salt influenced rift basin and thus gain an understanding of the relationships between normal fault growth salt tectonics and the evolution of syn rift depocentres the sleipner basin south viking graben northern north sea is ca 30 km long by 8 km wide and is bound to the east by a major extensional fault zone sleipner fault zone two types of fault related fold are identified within the basin 1 a fault parallel monocline interpreted as an extensional forced fold which formed through the upward propagation of the sleipner fault zone through ductile evaporites of the zechstein supergroup and 2 three fault perpendicular salt cored anticlines that compartmentalise the basin into four sub basins and are related to displacement gradients along strike of the sleipner fault zone detailed seismic stratigraphic analysis of pre and syn rift stratal units reveals a complex interplay between fault growth and salt movement which strongly controlled the evolution of syn rift depocentres during the early syn rift a series of depocentres separated along strike by the fault perpendicular folds were offset into the axis of the basin ca 3 4 5 km to the west of the sleipner fault zone by the fault propagation fold later in the rift event the influence of the fault perpendicular folds depleted resulting in a larger interconnected depocentre that shifted into the immediate hangingwall of the fault as the surface of the fault propagation fold was breached the results of this study have implications for normal fault growth and sedimentary depocentre development in salt influenced rift basins and contribute to the general understanding of the controls on salt migration

variscan to alpine heterogeneous palaeo stress field above a major palaeozoic suture in the carpathian foreland southeastern poland abstract the tectonic evolution of the region adjacent to the sw border of the east european craton is crucial for understanding the palaeozoic amalgamation of europe and its later evolution we present a structural analysis of the brittle deformation fault slip data inversion and folding carried out in the cambrian to cenozoic rocks of the european platform in se poland to characterize the late palaeozoic maastrichtian palaeocene and miocene tectonics of this region the variscan late carboniferous palaeo stress pattern was characterized by n s to nne ssw oriented compression as inferred from the folding of the palaeozoic mainly devonian rocks the compression was associated with the northwesterly present day coordinates motion of gondwana towards the northerly situated laurussia subsequently the mid polish trough mpt developed in an extensional regime the stress regime changed to compressional at the maastrichtian palaeocene transition in response to the africa europe plate kinematics the compressional regime induced the tectonic inversion of the mid polish trough the stress pattern was characterized by ne sw oriented compression in the holy cross mts hcm area and in the radomsko high folds and faults in the mesozoic cover revealed a sinistral reactivation of the holy cross fault hcf and of nw se trending faults the alpine stress patterns were related to the subduction of the european platform beneath the carpathian orogen the flexural bending of the subducted lithosphere induced a homogeneous middle miocene n s extension in the carpathian foreland subsequently the northward propagation of the carpathian front resulted in late middle miocene n s compression restricted to the proximal area of the frontal thrusts implied by a strain partitioning at a low friction contact between the carpathian nappes and the european platform since the palaeozoic the teisseyre tornquist zone ttz behaved as lithospheric weak zone which has been reactivated during the maastrichtian palaeocene change in stress regime it resulted in the tectonic inversion of the polish trough inherited faults conditioned superficial stress perturbations and focused the deformation

status and evolution of the cryosphere in the andes of santiago chile 33 5 s in the context of a general retreat of glaciers in the dry andes this study focuses on the state and recent evolution of debris covered glaciers and permafrost related landforms especially rock glaciers in the semiarid to semihumid laguna negra catchment a part of the andes of central chile at 33 5 s that is a key contributor of drinking water for the city of santiago we conducted catchment scale geomorphological mapping diachronic analysis of 1955 and 1996 orthophotographs and digital elevation models dems and the analysis of ground temperatures and their sensitivity to climate variation rock glaciers dominate spatially and in terms of water storage over glaciers area ratio 1 7 1 ratio of water equivalents 1 5 1 an intense downwasting has affected both debris covered and exposed glacier components in the punta negra subcatchment a process that is associated with the growth of numerous thermokarst depressions the altitudinal transect of ground temperature suggest that permafrost is widespread above 4000 m asl although it can also occur at lower elevations on sheltered footslopes and within rock glaciers the sensitivity analysis indicates that the near surface ground thermal regime at high altitudes is strongly influenced by the snow cover disappearance date which may therefore constitute an important control on the effect of climatic warming

permian and triassic rifting in northwest europe the permo triassic roughly coincided with the life span of pangaea so far as europe is concerned pangaea s creation began in the early carboniferous visean when the northward drifting megacontinent gondwana began to collide with the iberian portion of the slower moving laurussia while proto tethys was subducted beneath the southern margin of central europe creation was complete by the end of the carboniferous or early in the permian with the final development of the variscan orogenic belt which trends from brittany eastward through central europe and with the addition of western siberia along the line of the ural orogen ziegler 1989 despite or perhaps because of its bulk pangaea was not a stable megacontinent no sooner had it formed than it tried to break apart again the disintegration of pangaea had already started before the end of the triassic with the westerly extension of tethys between iberia and africa though not yet underlain by oceanic crust and by early in the jurassic rifting was taking place between africa and the americas in the newly forming central atlantic ocean ziegler 1988 indeed e w extensional movements within a proto atlantic ocean possibly began as early as the late carboniferous haszeldine russell 1987 whilst mid permian extension is well documented in east greenland surlyk et al 1984 these extensional movements may have propagated southward to initiate fracturing in the viking and central grabens of the north sea along which the late permian zechstein sea was to break into the subsiding rotliegend basins and towards the central atlantic where a shallow seaway eventually developed early in the jurassic thus in the northern half of pangaea the continued existence of the former laurussia was already at risk in the permian although crustal separation in the north atlantic which possibly started in the rockall trough in the early cretaceous was finally achieved along the line of the reykjanes ridge only in the paleocene these major events on the periphery of what is now europe separately and jointly were factors that probably controlled a whole sequence of tectonic events within the continent which in turn controlled its patterns of mostly terrestrial sedimentation climatically the northward drift of laurussia had carried nw europe from a region of equatorial rain forest during the later carboniferous to the latitudes of a trade wind desert like the modern sahara in the permian the late permian basins of upper rotliegend and zechstein deposition were arid rotliegend sediments are characterized by dune sand and the saline mudstones of a semipermanent desert lake and the zechstein by shallow water carbonates and anhydrite and deeper water halite during the triassic however brackish water fluvial and lacustrine sediments occupied the basinal areas although even here halite horizons e g rrt muschelkalk and keuper in the north sea area associated with local transgressions from tethys testify that arid conditions were never far away

rapid subsidence of small oceanic basins a study of the marsili basin central mediterranean many small backarc basins show subsidence rates significantly greater than those in major ocean basins of similar ages in this study we test by numerical modeling the hypothesis that small backarc basins are formed by the same fundamental processes as major oceanic basins i e by accretion spreading and cooling and that the rate of subsidence is modified and accelerated by lateral heat loss from the hot subbasinal asthenosphere to the surrounding cooler continental lithosphere bathymetric seismic and drilling data in the marsili basin a small and young backarc basin in the central mediterranean are used to constrain the models the results of this analysis confirm the above hypothesis they further suggest that for actively spreading backarc basins the most rapid subsidence occurs in a zone near the margin of the basin during the earliest stage of basin spreading whereas after spreading terminates the location for rapid subsidence migrates towards the basin center

polyphase rift evolution of the voring margin mid norway constraints from forward tectonostratigraphic modeling the mid norwegian voring margin bounding the northern atlantic underwent several rift episodes after the caledonian orogeny permo triassic extension concentrated at the eastern inner margin followed by jurassic cretaceous extension at the center of the margin finally more westward the last rift episode led to continental breakup in the earliest eocene although the general architecture of the margin may be clear the timing and distribution of particularly the oldest rift structures are poorly constrained we use two dimensional forward tectonostratigraphic modeling for better quantitative understanding of the tectonic evolution of the margin two regional profiles crossing the margin have been analyzed modeling of the two profiles integrates the basin shape and fill as well as the underlying crustal structure of the margin the modeling allows us 1 to quantify the distribution and timing of extension of subsequent rift episodes 2 to predict the basin and crustal architecture at deep levels and 3 to test different interpretations of the seismic data the level of lithospheric necking during basin formation is constrained by basement topography and moho depth and lies within the middle crust 20 km furthermore we investigate the migration of the rift axes and the elastic lithospheric strength during the different rift episodes locations of previous extension are not reactivated during renewed rifting instead renewed rifting occurs preferentially in regions where the lithosphere has experienced less extension

the effect of topography latitude and lithology on rock glacier distribution in the lemhi range central idaho usa abstract statistical analysis of rock glaciers in the lemhi range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology we inspected 171 alpine valleys in the lemhi range using optical remote sensing techniques digital topographic analysis and field examination in those valleys we identified 48 rock glaciers and examined them for lichen cover evidence of ice presence specific evidence of movement and distinctive morphological features in addition to recording the presence or absence of a rock glacier in each alpine valley existing rock glaciers were classified according to their morphology factors such as topographic shading lithology relief aspect and elevation determine the development and preservation of rock glaciers analysis of these factors in the lemhi range shows that elevation 2600 m a north facing aspect 300 60 and multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly whereas duration of insolation is a logical controlling factor latitude is more enigmatic additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range lithology may affect rock glacier distribution through its effects on hydrology or air ventilation moreover statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence suggesting that protalus lobes play a role in the genesis of rock glaciers in the lemhi range separate analysis of the classification systems shows that each morphologic class inferred to correlate with rock glacier activity is statistically significant and distinguishable from other classes in addition to the effect of insolation statistical analysis of the classification system also shows that latitude influences distribution of existing rock glacier classes independent of lithology

upper permian carbonates at the northern edge of the zechstein basin utsira high norwegian north sea abstract the first detailed description of zechstein carbonates and their diagenesis along the northern margin of the northern zechstein basin is based on core material from four wells on utsira high in the norwegian sector of the north sea it provides a generic link to the better known southern zechstein basin and northwards to the late permian east greenland basin the zechstein succession consists of shale carbonate cycles and anhydrite only occurs in the uppermost preserved cycle believed to correlate to zechstein 4 the eleven carbonate facies reflect deposition in shallow shelf and arid shoreline environments and resemble zechstein 2 and 3 carbonate facies from the southern zechstein basin the carbonates are pervasively dolomitized by an early texture preserving dolomite characterized by 18o values between 6 and 2 4 similar to dolomites in the southern zechstein basin and 13c values between 0 7 and 5 which is significantly lower than time equivalent dolomites from the southern zechstein basin later subaerial exposure and fresh water infiltration during the late permian or early triassic caused replacement of the upper part of the dolomite by crystalline fabric destructive calcite dedolomite the dedolomitized zone is up to 23 m thick and calcite crystals are characterized by moderately negative 18o values in the range 8 to 5 5 characteristic for meteoric water the utsira high carbonates thus share a depositional history with the classical zechstein carbonates whereas their diagenesis seems to have more in common with the time equivalent succession in east greenland early leaching and dolomitization enhanced porosity whereas subsequent late permian early triassic subaerial exposure and widespread dedolomitization had profound negative impact on reservoir properties of the zechstein carbonates

pre drift extension of the atlantic margins of north america and europe based on paths of permo triassic apparent polar wander summary we reconstruct the relative configuration of north america and europe prior to separation using paths of apparent polar wander apw for the interval 300 to 200 ma the bullard et al 1965 reconstruction closely superimposes the 300 ma points on the two apw paths but leaves the 200 ma points far apart conversely anomaly based reconstructions for later times approximately superimpose the 200 ma ends of the paths but leave the older ends far apart this indicates that separation of the interiors of the two continents began during the interval 300 to 200 ma long before surficial rifting commenced in the late mesozoic this in turn requires pre rift extension in the two continental margins extension appears to have occurred in two phases of approximately equal magnitude but significantly different direction the change in direction occurred at about 200 ma the earlier 300 to 200 ma episode of extension appears to have involved a strong element of sinistral shear based on our preferred reconstruction the total amount of pre rift extension of the two continental margins may have been as much as 1400 km

marine ingressions into the middle late permian saline lake of the southern permian basin rotliegend northern germany possibly linked to sea level highstands in the arctic rift system abstract a huge saline lake existed in the southern permian basin spb of northwest europe during late wordian to early wuchiapingian more than 2500 m thick continental siliciclastics and evaporites of the upper rotliegend ii were deposited before the marine zechstein transgression flooded the basin marine deposition took place in the arctic rift system between east greenland and the fennoscandian shield at that time interval sediments of the foldvik creek group reflect relative sea level fluctuations short termed pre zechstein ingressions from the boreal realm into the spb are known by the marine lamellibranch liebea reichei however sedimentological analysis of different saline lake horizons show that the marine influenced saline lake horizon does not differ lithologically from other saline lake claystone layers in the rotliegend succession the 87 sr 86 sr ratios of anhydrite 0 7089 0 7100 reflect deposition in a continental setting in contrast to this s isotopic values more than 11 7 cdt reflect marine pre zechstein ingressions into the spb in the middle niendorf and munster members s isotopic values of anhydrite can be used as an indicator for marine influence in the spb the pre zechstein ingressions superimpose the climatic triggered lake level fluctuations of the rotliegend saline lake two marine ingressions can be integrated into a set of regularly recurring abnormities in the depositional evolution these important evolutionary steps the saline lake formation the garlstorf ingression the p ameland and bahnsen lake level highstands the niendorf ingression and the zechstein transgression show a periodicity of more or less 1 ma one million year cyclicity is also known from deposits of the arctic rift system in east greenland wegener halvo and ravnefjeld formations a correlation of the upper rotliegend ii deposits with the succession of east greenland is proposed based on the assumption that the marine ingressions as well as the exceptionally intensive saline lake expansions could be linked to sea level highstands in the arctic rift system the result is the first correlation of upper rotliegend ii deposits with marine strata

self subduction of the pangaean global plate one of the most striking and rare occurrences in the earth s history is the amalgamation of most of the continental lithosphere into one supercontinent the most recent supercontinent pangaea lasted from 320 to 200 million years ago here we show that after the continental collisions that led to the formation of pangaea plate convergence continued in a large wedge shaped oceanic tract we suggest that plate strain at the periphery of the supercontinent eventually resulted in self subduction of the pangaean global plate when the ocean margin of the continent subducted beneath the continental edge at the other end of the same plate our scenario results in a stress regime within pangaea that explains the development of a large fold structure near the apex of the palaeotethys ocean extensive lower crustal heating and continental magmatism at the core of the continent as well as the development of radially arranged continental rifts in more peripheral regions of the plate

late carboniferous to triassic reactivation of variscan basement in the western english channel evidence from onshore exposures in south cornwall south cornwall represents the westernmost part of the variscan basement massif in sw england field based investigations into the distribution geometry kinematics and relative chronology of post variscan deformation have been accompanied by preliminary palaeostress analyses these indicate three episodes of basement reactivation 1 stephanian to early permian nnw sse extension 2 early to late permian strike slip deformation and 3 late permian to triassic ene wsw extension these data have been used to test and refine previously published models based upon seismic and well data of late carboniferous to triassic basement reactivation and sedimentary basin development within the western approaches trough we confirm that nnw sse regional extension and reactivation of ene striking variscan thrusts had initiated by the latest carboniferous and that ene wsw regional extension and dip slip reactivation of nnw striking high angle faults occurred during the triassic permian strike slip deformation recognized onshore may have contributed to the development of widespread unconformities within the ovshore basins

palaeocene recent plate boundaries in the ne atlantic and the formation of the jan mayen microcontinent abstract breakup and sea floor spreading between greenland and eurasia established a series of new plate boundaries in the north atlantic region since the late palaeocene a conventional kinematic model from pre breakup to the present day assumes that eurasia and greenland moved apart as a two plate system however new regional geophysical datasets and quantitative kinematic parameters indicate that this system underwent several adjustments since its inception and suggest that additional short lived plate boundaries existed in the ne atlantic among the consequences of numerous plate boundary relocations is the formation of a highly extended or even fragmented jan mayen microcontinent and subsequent deformation of its margins and surrounding regions the major oligocene plate boundary reorganization and microcontinent formation might have been precluded by various ridge propagations and or short lived triple junctions ne and possibly sw of the jan mayen microcontinent from the inception of sea floor spreading 54 ma to c18 40 ma our model implies a series of failed ridges offshore the faeroe islands a northern propagation of the aegir ridge ne of the jan mayen microcontinent and a series of triple junctions and or propagators in the southern greenland basin

engineering geomorphology of rock glaciers a partnership between geomorphology and engineering is facilitating human development in this harsh environment rock glaciers provide locations for urban water sources construction borrow sources drill sites shaft and tunnel portals ski tower supports and dam abutments rock glaciers as dynamic landforms necessitate proper identification in the field placing structures on in or adjacent to rock glaciers requires an appreciation and understanding of their temporal stability internal and surface characteristics provide important clues to the development and deformation of rock glaciers rock glaciers play a significant role in the alpine debris transport system active movement and mass wasting are perhaps the most obvious geologic hazards affecting engineered works the structure of the rock glacier is conducive to the production of a steady continuous supply of meltwater during summer months thus rock glaciers serve as alpine aquifers consideration of rock glaciers as potential aquifer sources requires caution because of the long term impact of climate change on the temporal nature of the landform from the rock glaciers that we have monitored for water quality characteristics it appears that they provide quality potable water this paper provides a foundation for appreciation and understanding of rock glaciers from an engineering geomorphologic point of view the approach taken in this paper provides practical important information to aid the engineer and engineering geologist in prudent evaluations of rock glaciers as potential sites for human development and uses the bottom line of our paper is rock glaciers must be avoided for essentially all structures

evidence for kilometre scale neogene exhumation driven by compressional deformation in the irish sea basin system simon p holford paul f green jonathan p turner gareth a williams richard r hillis david r tappin ian r duddy

stratigraphy petrography and dispersion of the lower permian syn eruptive deposits in the viar basin spain abstract this paper presents a stratigraphic petrographic and sedimentologic analysis of felsic syn eruptive deposits of the southernmost permian basin in europe viar basin an inner orogenic transtensional half graben located between two major geotectonic zones of the iberian variscan belt sw spain the syn eruptive deposits of the viar basin represent a mappable lithostratigraphic unit that is herein named the los canchales formation this unit forms a wedge shaped body bounded by alluvial fluvial deposits red layers that are in gradational contact the stratigraphic architecture of the los canchales formation is complex with frequent facies changes and interfingering among pyroclastic rocks resedimented volcaniclastic rocks and sedimentary rocks abundant fossil flora is also recorded a wax wane cycle of volcanic activity is recognized during the syn eruptive period two short lived volcanic episodes were recorded including ignimbrites and a possible phreatomagmatic event explosive volcanism generated pyroclastic flow surge and ash fall deposits in cases collapsing the drainage network they also modified the vegetation and created a new depositional setting with four successive sedimentary environments vegetated floodplain ephemeral sandy braidplain palustrine environment and again vegetated floodplain input of pyroclasts followed a nw to se longitudinal axial dispersal pattern

detecting rock glacier flow structures using gabor filters and ikonos imagery abstract while ridges and furrows on the surface of rock glaciers are probably the most characteristic morphological features of this expression of creeping mountain permafrost this is the first study that examines the utility of texture filters in detecting rock glacier flow structures texture features were derived from a gabor filterbank applied to two panchromatic ikonos orthoimages from the chilean andes and terrain attributes were obtained in order to narrow down the area of interest and as additional predictor variables four classification methods of different complexity generalized linear model glm generalized additive model gam support vector machine svm bundling were applied to three sets of predictor variables texture attributes terrain attributes and the combination of both and predictive performances were estimated using two spatial cross validation strategies in terms of the median area under the roc receiver operating characteristics curve auroc overall classifiers utilizing texture attributes alone or usually even better in combination with terrain attributes outperformed terrain attributes alone and bundling in most cases followed by svm showed the overall best performance as a classification method cross validated median auroc values were mostly between 0 70 and 0 80 or fair in this focused pilot study but much better results are to be expected at the landscape scale permutation based spatial variable importance measures indicate that gabor features corresponding to texture wavelengths between 10 and 30 m are the most important predictors which is consistent with typical ridge spacing on rock glaciers confounding occurred mostly in areas with linear erosion features and ridges or scarps in morainic and thermokarst terrain we suggest that texture filters and the chosen methodological approach are relevant not only for rock glacier mapping but also for delineating debris covered glaciers and characterizing glacier surfaces as well as for other geomorphological and cryospheric applications

thermal and mechanical evolution of u s atlantic continental margin abstract the postrifting tectonic subsidence of the u s atlantic continental margin appears to be due to thermal contraction following continental breakup this subsidence is greatly increased by the effect of sediment loading models for the response of the lithosphere to loads show that the rigidity of the lithosphere is a strong function of temperature hence the flexural rigidity at the u s margin should vary in both space and time the thermal structure and subsidence of the margin has been modelled using a two dimensional extension model where the amount of extension has been allowed to vary across the margin and lateral conduction of heat has been included the equivalent elastic thickness of the lithosphere has been approximated as the depth to an isotherm thermoelastic effects of the cooling lithosphere as well as the flexural loading of the sediments have been included the lateral flow of heat and flexure have contrasting effects the lateral heat flow tends to cause uplift of the coastal plain region landward of the hinge zone and to increase the subsidence rate in the regions of the transitional crust in addition the effects of lateral heat flow modify the thermal history of the sediments and heat flow flexure on the other hand causes subsidence of the coastal plain and decreases the sediment accumulation beneath the transition zone the stratigraphy of the u s margin is seen to be the result of the complex interaction of these effects as their contributions vary through the history of the margin end of article last page 1671

end of the kiaman superchron in the permian of sw england magnetostratigraphy of the aylesbeare mudstone and exeter groups the chronology of permian strata in sw england is fragmentary and largely based on radiometric dating of associated volcanic units magnetostratigraphy from the c 2 km of sediments in the exeter and aylesbeare mudstone groups was undertaken to define a detailed chronology using the end of the kiaman superchron and the overlying reverse and normal polarity in the middle and upper permian as age constraints the palaeomagnetic directions are consistent with other european permian palaeopoles with data passing fold and reversal tests the end of the kiaman superchron in the wordian occurs in the uppermost part of the exeter group the overlying aylesbeare mudstone group is early capitanian to latest wuchiapingian in age the changhsingian and most of the lower triassic sequence is absent magnetostratigraphic comparison with the southern permian basin shows that the exeter and aylesbeare mudstone groups are closely comparable in age with the havel and elbe subgroups of the rotliegend ii succession the altmark unconformities in these successions appear similar in age to the sequence boundaries in sw england indicating that both may be climate controlled clasts in the exeter group from unroofing of the dartmoor granite first occurred at a minimum of c 8 myr after formation of the granite supplementary material additional sampling magnetic fabric and palaeomagnetic data are available at http doi org 10 6084 m9 figshare c 3283400

geostatistical analysis of glacier roughness data in most glaciological and hydrological models surface roughness of snow and ice is an important parameter however roughness is generally used only as an estimated parameter for lack of available observations in this paper we present a method to collect and analyze ice surface roughness data using a specially designed instrument for survey and geostatistical methods for analysis the glacier roughness sensor grs built at the university of trier records variations in microtopography at 0 2 m 0 1 m resolution when pulled across an ice surface global positioning system data are used for location after several processing steps the data are analyzed using geostatistical methods the mathematical tool used to achieve a morphological characterization of ice surface types is the variogram grs data variograms and surface roughness analysis are ideal matches for morphological characterization because none of them requires or provides absolute elevation values morphology is described not by absolute elevation values but by the change of elevation in space which is the derivative of elevation surface roughness values the variogram is calculated from incremental values parameters extracted from variograms of grs data serve to distinguish lake surfaces wind structures ridge and vauey systems melting structures and blue ice areas examples are from jakobshavn isbrae drainage basin west greenland

the control of sedimentary facies by climate during phases of crustal extension examples from the triassic of onshore and offshore england and northern ireland crustal extension controls the tectonic accommodation space available for sediments in rift settings and may be defined by the structural and depositional geometry of sedimentary successions observed on seismic data and the rate of subsidence through time as represented by the accommodation of sediment the characteristic features of each are dependant on three variables the time taken for deposition the interplay between tectonics and eustasy and the lithology thus facies of the succession observed the sherwood sandstone group has been considered to represent a syn rift phase of fluvial deposition throughout europe with the overlying mercia mudstone group interpreted as the succeeding phase of deposition in an evaporitic seaway during post rift thermal subsidence more recently however there has been the recognition that it is the mercia mst gp which is seen to thicken markedly into faults imaged on seismic data rather than the sherwood sandstone group this work demonstrates the mercia mst gp to be a syn rift phase of deposition with the fine grained nature of the sedimentary record at this time controlled by the prevailing arid climate such conditions were not conducive to the large scale and rapid movement of sediments from the hinterlands raised by relative footwall uplift thus the sediments are fine grained the minor thickening of the sherwood sst gp into faults is interpreted to be a combination of minor extension in the early triassic superimposed on thermal subsidence inherited from the important regional phase of extension in the early permian analysis of the timing of fault growth indicates a larger proportion of fault controlled synsedimentary movement occurred during the mid to late triassic mercia mst gp rather than the early triassic sherwood sst gp

statistical estimation and generalized additive modeling of rock glacier distribution in the san juan mountains colorado united states 1 our goal is to quantify rock glacier abundance and analyze the topographic controls of rock glacier distribution patterns for this purpose we use statistical estimation techniques and generalized additive models relating rock glacier occurrences to terrain attributes significant applied results include the ability to determine water equivalence and denudation rates the statistical estimation of regional rock glacier abundance based on local interpretation of air photos is an efficient alternative to costly rock glacier inventories these presence absence data n 2933 also allow us to analyze the partly nonlinear topographic controls on rock glacier distribution with generalized additive models we apply these techniques in the san juan mountains 2874 km2 above 3400 m colorado where we obtained a total rock glacier surface area of 70 km2 corresponding to a water equivalence in the order of 0 50 0 76 km3 estimated rock glacier debris volumes imply postglacial denudation rates on the order of 0 5 1 1 mm yr 1 within the talus sheds of rock glaciers the distribution model shows the nonlinear factors of local slope slope of the contributing area local curvature and size of the contributing area controlling the probability of rock glacier occurrence the model yields an area under the receiver operating characteristics curve of 0 91 which indicates an excellent fit on the basis of the present results the integration of terrain attributes with remote sensing data will be the next step toward automatic mapping of rock glaciers in vast mountain areas

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

structural analysis of the smeaheia fault block a potential co2 storage site northern horda platform north sea abstract smeaheia a prominent fault block located on the horda platform northern north sea is identified as a potential subsurface co2 storage site we utilise the gn1101 3d seismic survey to generate a high resolution subsurface geomodel to inform the structural style and evolution of the fault block to investigate geological controls on proposed co2 storage and provide a geometric framework as a basis for future analyses two basement involved first order north south trending fault systems the vette fault zone vfz and the oygarden fault complex ofc bound the 15 km wide fault block the vfz bifurcates down section where it is hard linked with two separate basement structures a phenomenon we term as dual rooted apart from activity during the permo triassic rift phase 1 and the late jurassic early cretaceous rift phase 2 we present evidence that rifting in this part of the north sea continued into the late cretaceous with minor reactivation in the palaeocene eocene two segments of the vfz interacted and linked at a relay ramp during rift phase 2 second order thin skinned faults show basement affinity and developed during rift phase 2 in two distinct pulses a population of polygonal faults intersects the overburden and developed during the eocene to middle miocene we have revised the areal extent of two structural closures that define the smeaheia fault block alpha vfz footwall and beta ofc hanging wall which consist of upper jurassic viking group target formations simplified cross fault juxtaposition analysis of the vfz and second order intra block faults are presented and inform pressure communication pathways between the smeaheia and tusse fault block as well as reservoir integrity and compartmentalisation the geomodel further identifies important geological controls on co2 storage in the fault block including a thinning caprock above the alpha structure and identification of hard linkage between deep tectonic faults and shallow polygonal faults