material balance in alpine orogeny recent geophysical data are combined with older information for an updated picture of alpine kinematics using semiquantitative considerations of material balance in the alps a conventional pile of thin peel nappes is disrupted by a central longitudinal system of steep faults and steeply limbed folds both affecting disharmoniously the entire edifice of otherwise flat lying nappes it is particularly from late tertiary phases of deformation that structures of the second type the insubric system with the insubric line and the belt of late alpine windows acquired prominence for the present aspect of the alps these late structures formed as a dextrally transpressive intracontinental branch of the africa europa plate boundary mostly between areas of extension early motions in the late cretaceous to the late eocene were probably responsible for at least half of the 300 km dextral displacement required for the palinspastic restoration of the inner west carpathians and the dinarides during oligocene extension the late alpine batholiths intruded in a belt roughly along the insubric line while deep crustal and lithospheric roots were destroyed in the latest oligocene to middle miocene the adriatic plate moved dextrally to the west along the insubric transfer fault from its frontal insubric indenter a lower crust upper mantle flake probably first obducted in the cretaceous was detached and wedged into the penninic nappes of the western alps bird s head of the ivrea body both the northern and the southern transfer faults of the insubric indenter were disrupted and inactivated by late miocene to later events the giudicarie and neo north apennine events instead of the inactivated insubric fault the windows belt of en echelon folds assumed the role of dextral transpression all of these successive zones of motion are entangled in the ligurian knot largely hidden under the sea or young sediments a large part of the pre alpine crust and practically the whole mantle were subducted only in some cases were high pressure rocks of shallow continental origin re obducted the lithospheric root of the neo alps is largely contained in a vertical slab under the alps but some parts seem to have been removed and others disharmonically displaced with respect to the surface structures

the modified generalized moveout approximation a new parameter selection non hyperbolic generalised moveout approximation is a powerful tool to approximate the travel time function by using information obtained from two rays the standard approach for parameter selection is using three parameters defined from zero offset ray and two parameters obtained from a reference ray these parameters include the travel time and travel time derivatives of different order the original parameter selection implies more fit at zero offset compared with offset from a reference ray we propose an alternative approach for parameter selection within the frame of generalised moveout approximation by transferring more fit from the zero offset to a reference ray by changing in parameter selection the modified approximation is tested against the original one in few analytical model examples including the multi layered model

the arcs of the western alps and the northern apennines an updated view abstract the arcs of the western alps and the northern apennines and the link between them are in the process of being investigated using the european geotraverse and they have historically been interpreted in many different ways new information particularly geophysical further constrains possible models both arcs have evolved in several stages sometimes complexly interrelated and sometimes independent of each other compressional belts produced in these stages have either been of the push arc type indentation into a deformable mass or the pull arc type backward migration of hinge of a subduction zone leading to small extensional basins known as back arc basins and pores with an arcuate mountain range on the subduction side extensional periods with the possible formation of pull arcs in the alps comprise the gosau period between the eo and meso alpine push arc phases and the oligocene lull period between the meso and the neo alpine push arc phases in the northern apennines remainders of the meso alpine nappes were involved in oligocene early miocene pull arc formation associated with spreading in the balearic sea followed by push arc formation particularly in the middle miocene and by renewed pull arc formation from the latest late miocene to the present during all of these developments the moho was modified by such processes as lithospheric stretching asthenospheric intrusions subhorizontal shearing and isostatic uplift the present moho configuration is consequently a collage of moho patches formed at different intervals both push and pull arcs are laterally bounded by complementary strike slip or transform zones these too were modified in the course of history and their final geometry is consequently of a very complex nature in the alps for instance the insubric fault zone appears to have been the main dextral transform fault of the neogene push arc until it was sinistrally kinked by the giudicarie fault zone and probably deactivated dextral transpression being briefly transferred to the en echelon brachyanticlines of the late alpine windows in the case of the oligocene apennines the sinistral rotations of corsica and sardinia otherwise hard to understand may be attributed in part to sinistral transform motions along the eastern border zone of the oligocene early miocene balearic extension

a paleogene flora from the upper bonnet plume formation of northeast yukon territory canada palaeontological exploration of the bonnet plume basin in northwestern yukon territory canada has revealed a late paleocene to early eocene macrofloral assemblage from a channel fill deposit the flora is typified by cosmopolitan taxa and dominated by deciduous angiosperms with the notable presence of zizyphoides ettingshausenia and corylites floras with a similar composition are known from late cretaceous through early eocene deposits in alaska and the canadian arctic archipelago where they have been interpreted as evidence for warm equable temperatures this collection represents the most diverse known paleogene plant macrofossil assemblage from the yukon territory and helps to expand our knowledge of ancient high latitude floras

crayfish burrows from the latest cretaceous lower cantwell formation denali national park alaska their morphology and paleoclimatic significance abstract latest cretaceous strata of the lower cantwell formation denali national park central alaska range contain an abundance of megafloral remains and invertebrate and vertebrate trace fossils though dominated by herbivorous dinosaur footprints the abundance and diversity of fossil bird tracks are unique we present newly discovered crayfish burrows from several areas along a 50 km transect with denali national park most crayfish burrows from the lower cantwell formation are preserved only in cross section and range from approximately 5 10 cm in diameter where preserved in full relief and terminations present burrow depth is generally the cantwell formation fills the cantwell basin a 135 km long and up to 35 km wide east west trending basin bracketed by the hines creek fault to the north and the mckinley fault to the south basin fill comprises up to 4000 m of continental deposits interpreted as braided rivers alluvial fans floodplains swamps and ponds crayfish burrows provide evidence of water table level soil moisture fluctuations as well as insight into mean annual temperatures at the time of deposition of the lower cantwell formation a late cretaceous high latitude paleoecosystem despite a relatively high latitudinal setting 71 n paleolatitude the late cretaceous i e campanian maastrichtian mean annual temperature based on the distribution of similar present day crayfish burrows was more like that of southernmost ontario canada where the northernmost burrowing crayfish are found today the burrow depth suggests 1 no permafrost was present and 2 the phreatic zone was 30 50 cm below the paleo ground surface based on the presence of these crayfish burrows the paleoclimate is interpreted as humid continental koppen scheme with average summer high temperatures between 25 c and 28 c and average winter low temperatures between 6 c and 0 c these estimates compare somewhat favorably with previous clamp estimates of a warm monthly mean temperature of 17 08 1 6 c and a cold monthly mean temperature of 2 31 1 9 c

model for the origin of the yakutat block an accreting terrane in the northern gulf of alaska a composite oceanic and continental terrane the yakutat block is currently colliding with and accreting to north america in the northern gulf of alaska marine geophysical data indicate that the block has moved with the pacific plate during pliocene and quaternary time but are indeterminant about its previous movement history a model that explains some observed geologic and structural features of the block is that it originated as a result of subduction of the kula farallon spreading center beneath north america in this model the spreading center that formed the basaltic basement of the yakutat block was offset from a spreading center to the south by a left lateral transform fault 400 500 km long subduction of the northern spreading center about 45 m y ago sliced off part of the north america continental margin attached it to the kula plate and initiated northward movement of the composite terrane as the yakutat block during eocene and oligocene time migration of the southern spreading center toward north america truncated the yakutat block on the south and left a fossil fracture zone that is now seen as the transition fault the southern spreading center subducted about 25 m y ago and the yakutat block has since traveled with the pacific plate to southern alaska

vertebrate fossils dinosauria from the bonnet plume formation yukon territory canada dinosaurs and other terrestrial vertebrates are poorly documented in the mesozoic of the canadian polar region here we provide a complete review of the upper cretaceous maastrichtian vertebrate fauna of the bonnet plume formation in the northeastern yukon territory canada which includes the description of the first newly collected dinosaur bones from this unit in almost half a century previously reported fragmentary dinosaur remains collected in the early 1960 s pertain to an indeterminate hadrosaurid new material includes a poorly preserved forelimb bone and a pedal phalanx these new remains pertain to at least one species of non hadrosaurid ornithischian dinosaur and the humerus is tentatively referred to a small bodied basal ornithopod the new vertebrate fossils from the bonnet plume formation provide further evidence of vertebrates from this unit however directed field surveys in 2008 and 2009 suggest that vertebrate fossils are not abundant a review of the known localities of terrestrial mesozoic vertebrates from the canadian arctic indicate that it had a relatively diverse community of terrestrial vertebrates including dinosaurs during the late cretaceous but emphasizes our limited knowledge of the mesozoic arctic and considerable potential for future exploration and discovery

accretionary tectonics of the north american cordillera continental geology stands on the threshold of a change that is likely to be as fundamental as plate tectonic theory was for marine geology ongoing seismic reflection investigations into the deep crustal structure of north america are verifying that orogenic zones are underlain by low angle faults of regional extent brown et al 1981 the growing body of regional field relations is likewise delineating numerous orogenic sutures that bound discrete crustal fragments paleomagnetic and paleobiogeographic studies are revealing major latitudinal shifts and rotations within and between suture bounded fragments particularly within the north american cordillera such interdisciplinary studies are leading to a consensus that the cordillera has been built by progressive tectonic addition of crustal fragments along the continent edge in mesozoic and early cenozoic time such crustal growth is referred to as accretionary tectonics in this paper we review some of the important concepts in accretionary tectonics discuss the nature of the materials accreted between central alaska and southern california in jurassic and cretaceous time and consider the general relations between cordilleran accretion and the movement of lithospheric plates the concept of continents growing by peripheral accretion through geologic time has long been a topic of great interest with the advent of plate tectonics a number of different mechanisms for crustal accretion have arisen along with mechanisms for crustal attrition accretion mechanisms include the growth of imbricated sedimentary prisms along inner trench walls slicing off of submarine topographic irregularities within subducting plates and collision of continents and volcanic arcs by ocean basin closure tectonic attrition mechanisms include rifting transform faulting and strike slip or underthrust removal of inner trench wall materials coincident with or in place of accretionary prism growth growth of intraorogenic ocean basins by seafloor spreading is an additional important mechanism for creating accretionary materials as well as displacing crustal fragments an important implication of plate kinematic theory is the likelihood for accretionary and attritionary mechanics to operate in series both in time and space along continental margins since attrition by nature leaves little material evidence of having operated one of the major problems confronting cordilleran geologists lies in the recognition of such attrition within the ancient record particularly when interspersed with accretionary events the spectrum of accretion and attrition mechanisms viewed at cm yr 1 plate transport rates over time scales of 100 m y leads one to suspect a highly mobile history for continental margin orogens the serial arrangement of subducting transform and rifting links along the modern cordillera plate juncture system and both serial and parallel arrangements in the western pacific systems show the complex interplay of such mechanisms through space similar arrangements overprinted through time are suggested by the rock assemblages and structural patterns within the cordillera which presently resemble a collage of crustal fragments davis et al 1978 recognition of the structural state of this collage geologic field mapping and geophysical investigations will bring about a new level of understanding in the growth of continental crust and the reading of stratigraphic records within the fragments and future palinspastic restorations will lead to a new level of understanding in paleogeography and earth history the first problem to be considered is the recognition of native north american crust from exotic fragments that have been accreted to its edge

a crested theropod dinosaur from antarctica jurassic fossil vertebrates collected from the falla formation in the central transantarctic mountains included a partial skull and postcranial elements of a crested theropod cryolophosaurus ellioti gen nov sp nov the theropod bears some resemblance to the large tetanurans of the middle to late jurassic but also has primitive ceratosaurian features elements from a prosauropod teeth from scavenging theropods a pterosaur humerus and a tritylodont molar were also recovered the presence of this fauna suggests that a mild climate existed at high paleolatitude in this area of gondwana during the early jurassic

the late cretaceous environment of the arctic a quantitative reassessment based on plant fossils abstract late cretaceous megafossil floras from the palaeo arctic of northeastern russia and northern alaska are reviewed in respect of their age composition structure and floral dynamics palaeofloral correlations and comparisons are made between the two regions nine angiosperm rich predominantly cenomanian to coniacian floras from the palaeo arctic are re evaluated using climate leaf analysis multivariate program clamp calibrated using a global gridded 0 5 0 5 climate data set derived from that used in climate modelling additional floras from lower palaeolatitudes were used to derive latitudinal temperature gradients seven from n america five from around 30 n palaeolatitude in europe and one from kazakhstan the arctic climatic determinations similar to previous estimates support the existence of a northern pacific ocean cold gyre and a warm arctic ocean at palaeolatitudes greater than 80 n floras are insufficiently diverse in woody dicot taxa to use clamp but using clamp derived latitudinal temperature gradients arctic ocean coastal environments at 70 ma and 82 n and which supported a diverse dinosaur magafauna are predicted to have experienced a mean annual temperature of 6 3 2 2 c a warm month mean of 14 5 3 1 c and a cold month mean no colder than 2 0 3 9 c all uncertainties are 2 the new estimates are in good agreement with a wide range of non palaeobotanical climate proxies and render as an outlier warmer temperature estimates for the arctic ocean derived from the tex 86 proxy modelling however shows that land to ocean temperature gradients could have been steep the clamp estimates also suggest high values for humidity and precipitation consistent with sedimentological indicators and coupled with warm temperatures support the existence of a persistent polar cloud cap that helped maintain high terrestrial air temperatures throughout prolonged periods up to 5 months of winter darkness

a new jurassic pliosaur from melville island canadian arctic archipelago a partial skeleton of a plesiosaur reptilia sauropterygia from the hiccles cove formation middle jurassic callovian of melville island canadian arctic archipelago is the first marine reptile fossil with well preserved skull from the canadian arctic and represents a new genus and species of rhomaleosauridae borealonectes russelli the rhomaleosauridae are a problematic group and a review of the current status of included taxa is given prior to the description of the canadian material the holotype and only known specimen of the new species consists of the skull anterior cervicals and right forelimb the new taxon is characterized by the large prefrontal and the configuration of the postorbital bar in which the postfrontal is excluded from the supratemporal fenestra these are potentially unique features among rhomaleosaurids it exhibits a combination of primitive and derived characteristics that are variable among rhomaleosaurids such as the absence of the dorsomedian foramen and anterior pt

unravelling polyphase brittle tectonics through multi software fault slip analysis the case of the voltri unit western alps italy abstract we have analyzed the brittle structures in a key area of the alps apennines transition zone nw italy here two orogens have interfered with each other since oligocene times producing a complex structural evolution and a heterogeneous fault population only relative chronologies can be reconstructed as stratigraphic constraints are lacking we have performed the inversion of fault slip data with two softwares for paleostress calculations combined with field observations at selected structural stations and photo interpretation the resulting incompatible stress tensors can be grouped in this sequence i a strike slip tensor with nnw sse trending 1 event a ii a strike slip tensor with ne sw trending 1 event b and iii an extensional transtensional tensor with nw se or ne sw trending 3 event c we correlated our results with structures of known age from adjacent areas event a is possibly rupelian early chattian linked to far field incipient rifting in the future ligurian provencal basin event b fits oligo miocene shortening the faults may belong to a sinistral strike slip zone that accommodated the oblique component of deformation during the rotation of the corsica sardinia block event c is attributed to a pliocene quaternary neotectonic event therefore combining different inversion procedures with a detailed structural analysis has successfully unravelled the polyphase brittle tectonics

provenance of oligocene synorogenic sediments of the ligurian alps nw italy inferences on belt age and cooling history mineral chemistry 40ar 39ar geochronology on white micas and apatite fission track thermochronology aftt are applied here to study the provenance of the synorogenic molare formation lowermost unit of the tertiary piedmont basin clastic sequence the molare formation was deposited during transgression onto the ligurian alps nappe stack in the early oligocene depositional facies show that clastic distribution remained transversal with local sources located just landward from the coastline phengite mineral chemistry together with 40ar 39ar data clearly shows two distinctive source areas each one mirroring the composition of the basement directly beneath the clastic sequence amphibole mineral chemistry allows second order provenance distinctions within each sector reflecting heterogeneous metamorphic evolution of the bedrock complexes integrated 40ar 39ar dating and aftt suggest that following a fast cooling exhumation episode of the ligurian alps during the oligocene very little net uplift has since occurred this is due to a period of general subsidence from the oligocene late miocene followed by comparable uplift from late miocene pliocene to the present in general our data provide an image of the ligurian alps during the oligocene which is very similar to the present day one

magnetic overprinting in southeastern australia and the thermal history of its rifted margin the magnetizations of many rock units in southeastern australia have been severely overprinted interpretation of early work was hindered by this and one of the aims of the current research is to ascertain the nature of the overprint mechanism its geological significance and its regional extent results from three igneous bodies from the sydney basin which have been studied previously in a reconnaissance fashion have provided a new insight into the reason for such widespread magnetic overprinting the hornsby breccia hb and milton monzonite mm yield similar magnetic signatures both containing discrete high and low temperature magnetizations with directions of dec 72 inc 83 95 4 and dec 13 inc 76 95 2 respectively for hb and dec 60 inc 78 95 4 and dec 348 inc 79 95 6 respectively for mm the corresponding pole positions are 29 s 166 e a95 7 and 59 s 139 e a95 4 for hb and 22 s 171 e a95 7 and 55 s 158 e a95 11 for mm the paleomagnetic direction and pole from the third body studied the mogo hill basalt mh are dec 241 inc 81 95 5 and 41 s 130 e a95 9 this pole position and the two low temperature overprint pole positions from hb and mm are consistent with ages ranging from 100 m y to approximately 70 m y when compared to the late mesozoic apparent polar wander path we relate the overprinting to uplift erosion and rapid supracrustal cooling of the southeastern margin of australia associated with initial phases of marginal rift development prior to seafloor spreading in the tasman sea the temperatures of rocks now exposed may have reached 200 c or higher before the rapid cooling blocked and stabilized the overprint magnetizations

basal ornithopod dinosauria ornithischia teeth from the prince creek formation early maastrichtian of alaska a diverse and prolific record of polar dinosaurs comes from the upper cretaceous campanian maastrichtian sediments of the prince creek formation exposed on alaska s north slope previous assignment of basal ornithopod material from this formation has been based solely on teeth which have either been referred to hypsilophodontid indet or thescelosaurus sp here we re examine this material and describe several new specimens including five isolated premaxillary teeth and three cheek teeth the premaxillary teeth are most similar to those of thescelosaurus whereas the cheek teeth are more similar to its sister taxon parksosaurus for which premaxillary teeth are unknown referral of this new material to thescelosaurus would represent the oldest occurrence of this taxon and considerably extend its stratigraphic range a more likely possibility is that the premaxillary teeth are referable to parksosaurus an interpretation that is more parsimonious from a stratigraphic perspective intriguingly one ch

a multi disciplinary perspective on habitat preferences among dinosaurs in a cretaceous arctic greenhouse world north slope alaska prince creek formation lower maastrichtian abstract the prince creek formation of northern alaska is the most abundant source of polar dinosaur remains in the world and now corroborating data from this well studied rock unit allow for making inferences about the paleoecological preferences for these extinct polar animals the rock unit records high latitude alluvial sedimentation and soil formation on a low gradient muddy coastal plain compound and cumulative andic entisols and inceptisols formed on levees point bars crevasse splays and along the margins of floodplain lakes ponds and swamps abundant organic matter carbonaceous root traces fe oxide depletion coatings and zoned peds indicate periodic waterlogging anoxia and gleying consistent with a high water table in contrast fe oxide mottles ferruginous and manganiferous segregations bioturbation and less common illuvial clay coatings indicate recurring oxidation and periodic drying out of some soils an integrated reconstruction of pedogenic processes and biota suggests that this ancient arctic coastal plain was influenced by seasonally fluctuating water table levels and floods and in distal areas marine waters four of the five bonebeds in this study are from more distal areas represented by lower delta plain facies while the fifth bonebed is from a more proximal part of the basin represented by a somewhat better drained coastal plain facies bonebeds in the distal areas are dominated by edmontosaurus sp while the more proximal bonebed is dominated by the remains of the ceratopsian pachyrhinosaurus perotorum the distribution of these bonebeds sedimentological facies paleosols and biota suggests that pachyrhinosaurus may have preferred more upland environments while edmontosaurus preferred lowland deltaic environments this distribution may be the result of physiological adaptation to the pronounced seasonality provided by polar terrestrial ecosystems in contrast to a preferred habitat distribution of these large herbivores the large predatory dinosaur nanuqsaurus hoglundi seems to have had a more ubiquitous distribution across the landscape

dinosaurs on the north slope alaska high latitude latest cretaceous environments abundant skeletal remains demonstrate that lambeosaurine hadrosaurid tyrannosaurid and troodontid dinosaurs lived on the alaskan north slope during late campanian early maestrichtian time about 66 to 76 million years ago in a deltaic environment dominated by herbaceous vegetation the high ground terrestrial plant community was a mild to cold temperate forest composed of coniferous and broad leaf trees the high paleolatitude about 70 to 85 north implies extreme seasonal variation in solar insolation temperature and herbivore food supply great distances of migration to contemporaneous evergreen floras and the presence of both juvenile and adult hadrosaurs suggest that they remained at high latitudes year round this challenges the hypothesis that short term periods of darkness and temperature decrease resulting from a bolide impact caused dinosaurian extinction

spore pollen evidence for early oligocene high latitude cool climatic episode in northern canada climatic cooling in the eocene leading to markedly lower temperatures in the oligocene has been documented in oxygen isotope studies in the north pacific1 2 new zealand3 south pacific4 and north sea5 these lower temperatures in the oligocene correspond to palaeoclimatic interpretations of north american leaf floras6 7 which suggest a profound cooling occurring towards the end of the eocene indicated also in the southeastern united states from studies on mid tertiary spores and pollen8 recently collinson et al 9 have shown palaeobotanically that in southern england cooling occurred gradually starting in the latest early eocene leading to two major periods of floristic change before the end of the eocene thick tertiary sections in the subsurface mackenzie delta region northwest territories10 11 provide well preserved palaeogene palynofloras12 discussed here which indicate a cooler climate in the oligocene following warm temperate conditions in the eocene this widespread early middle oligocene cool episode is thus represented in both high latitude and lower latitude floras and seems to have been of global extent persisting until towards the end of the oligocene but its precise dating remains a problem in northern canada it is followed by an amelioration of the climate in the late oligocene which persisted probably until the middle miocene the rate of cooling during the eocene and oligocene may have varied depending on locality but once established the cooler oligocene climate exerted a profound influence on biotic development

paleobotanical evidence for cool north polar climates in middle cretaceous albian cenomanian time mid cretaceous albian cenomanian floras are abundant and diverse on the north slope of alaska the older floras consist of conifers cycadophytes ferns ginkgophytes and sphenophytes horsetails angiosperms appeared in latest albian time and rapidly diversified the preserved floras consist entirely of deciduous plants with the exception of a microphyllous conifer ferns and sphenophytes deciduousness is evidence for strong seasonality which for these floras might be variations in either light or temperature or both cool temperatures are suggested by the prevalence of toothed leaves among the angiosperms and the presence of large leaved conifers the paleobotanical evidence points to a mid cretaceous climate that was no warmer than cool temperate on the north slope of alaska

structures in natural serpentinite gouges abstract serpentinite gouges from cataclastic fault zones in the voltri massif nw italy are dominated by few discrete boundary parallel y shears and oblique synthetic riedel r 1 shears separating domains of massive gouge unlike natural clay rich fault gouges the cohesive microbreccia domains only rarely show foliations these structures dominated by discrete shears indicate a significant degree of localization of the deformation at the scale of the gouge the dominant gouge forming mechanisms were fracturing of olivine and pyroxene grains along serpentinized grain boundaries and initiation of transgranular fractures in pyroxene grains in domains of lattice bending and grain indentation syn tectonic serpentinization added to the weakening of fragments textural similarities with experimentally formed gouges suggest that the voltri fault zones were dominated by stick slip sliding hence that they may represent fossil seismogenic faults a notable aspect of the gouge texture in the voltri fault zones is a sigmoidal shape of the riedel shears which bend into parallelism with the y shears it is argued that this geometry was largely controlled by local perturbations of the stress field near heterogeneities on y or p shears the average spacing between the r 1 shears increases linearly with 0 47 times the distance between bounding y shears this proportionality may reflect a balance between the cohesive strength of the gouge material and the shear stresses acting on the bounding slip planes

paleoclimate reconstruction of the prince creek formation arctic alaska during maastrichtian global warming abstract the upper cretaceous maastrichtian prince creek formation of arctic alaska 82 85 n paleolatitude preserves successions of alluvial paleosols that are used to estimate mean annual precipitation map mean annual temperature mat and meteoric water oxygen isotope composition for the prince creek formation the highest map estimates range between 1000 and 3900 mm yr and the lowest range between 350 and 1200 mm yr the precipitation variability derived from stable carbon isotope analysis occurs on a time scale of 104 years map values agree with previous interpretations from fossil pollen pedological features soil types vegetation composition sedimentological indicators and clamp estimates that suggest high precipitation amounts and high humidity despite the considerable uncertainty with mat proxies our values are consistent with warm month mean temperatures obtained previously from paleobotanical data the 18o of smectite from bentonite beds clusters around 5 0 vsmow the 18o of meteoric water calculated from bentonitic smectite is 23 vsmow assuming a mean annual temperature of 6 3 c which is slightly more 18o depleted than meteoric water calculated from pedogenic siderite in stratigraphically younger beds closer to the brooks range chronostratigraphic correlation with the lower cantwell formation denali national park alaska 64 n paleolatitude suggests higher precipitation rates and highly 18o depleted precipitation in the late cretaceous paleo arctic compared to central alaska these data are consistent with previous studies that suggest a warmer and moister greenhouse earth and an intensified hydrological cycle that enhanced latent heat transport resulting in increased rainout effects

an interpretation of cretaceous and tertiary biota in polar regions abstract rich fossil floras and vertebrate faunas lived within the arctic and atarctic circles during the cretaceous and paleogene these occurrences seem explicable by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there there seems no need to invoke a lower tilt to the earth s axis to provide greater warmth and light in polar regions to account for these fossil records

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

latest cretaceous maastrichtian climate of the koryak upland of north east russia based on a quantitative analysis of a palaeo polar flora we describe fossil plant assemblages from the late maastrichtian kakanaut formation of the koryak upland north east of russia which represent a high 75on palaeolatitude flora the flora contains about 40 species including liverworts horsetails ferns cycadophytes ginkgos conifers and angiosperms angiosperms and conifers predominate and unusually the flora contains typical cretaceous taxa admixed with elements that are more characteristic of the paleocene reconstruction of the palaeoclimate in the kakanaut area was made using the climate leaf analysis multivariate program clamp employing a recently developed calibration that yields 23 different climate variables analysis was made based on 21 morphotypes of woody dicotyledonous plants from the kakanaut flora the analysis indicated a mean annual temperature of 12 2 2 0 c a warmest month mean temperature of 20 6 2 5 c a coldest month mean temperature of 4 8 3 2 c the growing season lasted approximately 7 months during which there was almost 1 m of precipitation this and other indicators relative humidity vapour pressure deficit and potential evapotranspiration all suggest a year round humid regime the winter temperatures suggest occasional mild frosts in this near sea level setting so that at higher elevations freezing conditions would have been more persistent these results throw new light on the living and breeding conditions of diverse latest cretaceous arctic dinosaur populations as represented by numerous skeletal and egg remains associated with the plants

mapping of moveout attributes using local slopes decomposing seismic data in local slopes is the basic idea behind velocity independent imaging using accurate moveout approximations enables computing moveout attributes such as normal moveout velocity and nonhyperbolic parameters as functions of zero offset travel time mapping of moveout attributes is performed from the pre stack seismic data domain into the time migrated image domain the different moveout attributes have different accuracy for a given moveout approximation that depends on the corresponding order of travel time derivative the most accurate attribute is the zero offset travel time and the nonhyperbolic parameter has the worst accuracy regardless of the moveout approximation typically the mapping of moveout attributes is performed using a point to point procedure whereas the generalized moveout approximation requires two point to point mappings testing the attribute mapping on the different models shows that the accuracy of mapped attributes is model dependent whereas the generalized moveout approximation gives practically exact results

the early stages of the alpine collision an image derived from the upper eocene lower oligocene record in the alps apennines junction area the upper eocene lower oligocene sediments deposited in the eastern part of the tertiary piedmont basin in northern italy provide a complete record of the unroofing of the alpine orogenic prism during the early stages of exhumation in the ligurian sector from late priabonian till late rupelian time the sediments in the study area were derived from two different sources one characterised by white micas with sib6 5 pfu and permian 40 ar 39 ar ages 270 ma and the other characterised by white micas with sin7 pfu and eocene oligocene 40 ar 39 ar ages 32 50 ma the first source is considered to be indicative of low pressure metamorphic rocks that covered the hp rocks of the ligurian alps and were completely eroded by chattian time from this time on the study area started to record the first input from western alpine sources characterised by a larger span of ages with a more frequent eoalpine signal thus sediments deposited in the eastern part of the tertiary piedmont basin contain the only available evidence of rocks belonging to high crustal levels in the alpine orogenic prism that were not affected by the alpine overprint these data also provide time constraints to the poorly dated first conglomerates deposited in this area 40 ar 39 ar geochronology reveals a minimum age of 33f1 4 ma for the pianfolco conglomerates in the type locality and of 31 4f3 5 ma for the borbera conglomerates d 2004 elsevier b v all rights reserved

some constraints on the kinematics of the tertiary piemonte basin northwest italy abstract an analysis of fault slip data in oligocene and miocene sediments of the piemonte basin northwest italy shows that a nearly continous sweep of shortening directions exists between the northern apennines and the maritime alps transport directions change from n s to nw se near the western termination of the northern apennines through w e in the ligurian alps to sw ne in the maritime alps n nw directed thrusting along the front of the monferrato culmination fits within this general kinematic framework in addition basement thrusts and transform faults were not sealed by an oligocene transgression but remained active throughout the oligocene and miocene these data provide a distinct constraint on the tertiary kinematics and dynamics of the alps apennine system

palaeomagnetism of volcanic rocks of the kodiak islands indicates northward latitudinal displacement in the past decade it has become widely accepted that southern alaska is composed of allochthonous terranes1 4 but the times of amalgamation and their accretion to north america remain controversial palaeomagnetists and geologists generally agree that the talkeetna superterrane consisting of the wrangellia and peninsular terranes fig 1 was far to the south of its present position with respect to north america in triassic and jurassic time1 4 this consensus is lost when it comes to the question of the relative position of these terranes in the tertiary previously limited palaeomagnetic evidence suggested that the peninsular terrane may have lain substantially south of its present position4 but the timing of deformational and thermal events and the apparent absence of a tertiary suture zone argue for a cretaceous docking of wrangellia and the peninsular terrane5 6 here we present new palaeomagnetic results demonstrating that the kodiak islands were indeed at a more southerly latitude 62 myr ago around 43 n and discuss the implications of this conclusion

palaeomagnetism of lower cretaceous tuffs from yukon kuskokwim delta region western alaska during the past decade the prescient arguments1 3 for the allochthoneity of large portions of southern alaska have been corroborated by detailed geological and palaeomagnetic studies in south central alaska4 9 the alaska peninsula10 kodiak island11 12 and the prince william sound area13 fig 1 these investigations have demonstrated sizeable northward displacements for rocks of late palaeozoic mesozoic and early tertiary age in those regions with northward motion at times culminating in collision of the allochthonous terranes against the backstop of nuclear alaska14 15 a fundamental question is which parts of alaska underwent significantly less latitudinal translation relative to the stable north american continent thereby serving as the accretionary nucleus into which the displaced microplates 16 were eventually incorporated17 18 here we present new palaeomagnetic results from tuffs and associated volcaniclastic rocks of early cretaceous age from the yukon kuskokwin delta region in western alaska these rocks were probably overprinted during the cretaceous long normal polarity interval although a remagnetization event as recent as palaeocene cannot be ruled out this overprint direction is not appreciably discordant from the expected late cretaceous direction for cratonal north america the implied absence of appreciable northward displacement for this region is consistent with the general late mesozoic early tertiary tectonic pattern for alaska based on more definitive studies little to no poleward displacement for central alaska though substantially more northward drift for the southern alaska terranes comprising alaska peninsula kodiak island prince william sound area and matunuska valley since late cretaceous to palaeocene time

the paleoenvironment of tyrannosaurus rex from southwestern saskatchewan canada the recovery of identifiable plant remains intimately associated with a skeleton of tyrannosaurus rex in southwestern saskatchewan canada provides the basis for interpreting the latest maastrichtian 65 5 65 ma paleoenvironment of the region fossil plants from the site are described and fruits formerly known as aesculus antiquus dawson or ficus ceratops knowlton are transferred to a new taxon spinifructus antiquus dawson comb nov study of the sediments of the frenchman formation that host the bones and plants in combination with analysis of the plants indicates that the regional climate was mesothermal and without winter frost but with seasonal drought the t rex is believed to have roamed a broad river valley abundantly vegetated by a largely deciduous flora the deciduous nature of the saskatchewan paleovegetation interpreted as a response to low winter light levels at high latitude contrasts strongly with the contemporaneous vegetation of a few degrees latitude further south and leads t

subsidence stress regime and rotation s of a tectonically active sedimentary basin within the western alpine orogen the tertiary piedmont basin alpine domain nw italy the oligocene to miocene tertiary piedmont basin tpb is located in the nw part of italy at the junction between the apennine and the alpine thrust belts the position of the tpb on top of the alpine apennine orogen poses fundamental questions as to the tectonics of the basin subsidence having undergone little deformation the tpb sediments provide an insight into the stress regime and rotations in the kinematically very complex area surrounding the basin itself in this study we integrate subsidence and structural analysis with measurements of magnetic susceptibility anisotropy ams and natural remanent magnetization nrm in order to better constrain the tectonic kinematics of the basin evolution a major important period of subsidence occurred in the middle miocene involving the whole basin during this period the tpb experienced ne sw directed compression and limited shortening some nw se directed compressional features have been identified and they were probably active during post tortonian times structures associated with north south tension are quite common but the amount of strain that they accommodate is minor in addition this research provides new preliminary data suggesting counterclockwise rotation in the tpb by c 20o which has taken place during middle miocene time

a gravity model of the crust beneath the tertiary piemonte basin northwestern italy abstract a gravity model of a crustal section crossing the tertiary piemonte basin from north to south is presented it was constructed by combining geological data and the results of the application of several geophysical methods with particular reference to the seismic findings a model is proposed for the morphology of the deep crust crust mantle transition identified by the wide angle reflection seismic data from the european geotraverse egt project and its geological consequences are discussed the existence of substantial displacements at the crust mantle boundary is stressed they do not appear to be directly related to superficial structures but underscore the wedging of the ligurian mantle on the insubrian crust compared with the observed bouguer gravity field gravity modelling of the section has supplied a calculated anomaly with a persistent short wavelength negative residual anomaly curve in the area of the asti basin it is suggested that this anomaly is due to a wedge of sedimentary rocks within the crust the wedge consists of both apennine and padane units and is located along a major structural boundary where metamorphic crust and tertiary sediments belonging to the alpine domain overthrust apennine and padane units during the tertiary

vertebrate extinctions and survival across the cretaceous tertiary boundary abstract a critical analysis of the fossil vertebrate record across the cretaceous tertiary boundary shows that the available evidence is far less accurate than that concerning invertebrates and microfossils far reaching conclusions have been drawn from generalisations about vertebrate extinctions in the continental realm based on the local record from western north america but little is known about patterns of terminal cretaceous vertebrate extinctions in other parts of the world and even the western north american record is ambiguous despite this unsatisfactory record it clearly appears that terminal cretaceous vertebrate extinctions were highly selective with some groups e g dinosaurs becoming completely extinct whereas others seem to be virtually unaffected this argues against devastating catastrophes of the kind postulated by some recent impact scenarios however the survival of groups known to be sensitive to climatic deterioration such as crocodilians and other non dinosaurian reptiles indicates that alternative hypotheses involving gradual but fairly important climatic changes on a world wide scale are not convincing either the pattern of extinction and survival among vertebrates across the cretaceous tertiary boundary may be explained as a consequence of the disruption of some food chains following a crisis in the plant kingdom which itself may have been the result of the atmospheric consequences of unusual extraterrestrial or internal events

extended period of extinctions across the cretaceous tertiary boundary in planktonic foraminifera of continental shelf sections implications for impact and volcanism theories discussion and reply

short paper kinematics of the alpine arc is there a continuous sweep in direction of alpine orogenic displacements around the alpine arc or does the overlap of a few distinct directions give this impression the thrust evolution of the sw alps which supports the latter view does not accord with the hypothesis of indenter induced body forces two displacement realms one with directions determined by intraplate configuration and another with directions related simply to the body forces maycoexist within the orogen but this is not yet established one of the longest standing disagreements in alpine geology concerns the nature of the radial pattern of orogenic displacements outwards from the alpine arc in one view there is a continuum of displacement directions sweeping from approximately southward in the maritime alps through west and northwest to approximately northward in austria in the other view there is no continuum but a small number of distinct directions of orogenic displacements each dominating a particular sector which relay one to another around the alpine arc recent papers mark a significant development in both sides of this argument which is given additional importance by the attempt of platt et al 1989 a to use displacement data to constrain plate motions this paper is intended as a contribution to the discussion and suggests one possible resolution of the argument sophisticated syntheses of alpine structure have for a long time accepted the possibility that both of the above views have some validity and goguel 1963 is a good starting point for discussion his displacements of crystalline basement of

extensional faulting in an intraoceanic subduction complex working hypothesis for the palaeogene of the alps apennine system abstract within the ophiolite complexes exposed in the ligurian alps and apennines nw italy several extensional detachment faults are identified which overprint late cretaceous high pressure metamorphic fabrics developed in an intraoceanic subduction system one of these detachment faults is the sestri voltaggio line which marks an 8 kbar pressure gap between blueschist facies ophiolites and calcareous sediments of the sestri voltaggio zone and underlying eclogite fades ophiolites and metasediments of the voltri massif radiometrie and stratigraphie constraints suggest that extension has occurred during the late paleocene to possibly early eocene from the middle eocene onward compressional tectonics prevailed again resulting in westerly directed imbrications in the ligurian alps and easterly directed folding and thrusting in the ligurian apennines a strong correlation is identified between the africa europe convergence rate and the stability of the accretionary wedge i e the paleocene extension coincides with a period of strongly reduced convergence velocities whilst the middle eocene transition to compressional tectonics concurs with an acceleration of the convergence rate this inferred relation between convergence rate and style of internal deformation matches very closely the results from mechanical models addressing the stability of orogenic wedges with a strain rate dependent rheology and provides the basis for a working hypothesis on the palaeogene evolution of the alps apennine orogenic system

dinosaur demise in light of their alleged perennial polar residency the end cretaceous biological crisis is represented by the demise of the non avian dinosaurs however most crucial biologically was the elimination of the photosynthesizing marine phyto and zooplankton forming the base of the marine food chain their abrupt demise attests to sunlight screening darkening the atmosphere for a few years alvarez et al science 208 1095 1108 1980 doi 10 1126 science 208 44 noticed in deep marine end cretaceous sediments an anomalous rise in the chemical element iridium ir which is rare on planet earth and thus suggests an extraterrestrial origin through an impact of a large asteroid this impact would have ejected enormous quantities of particles and aerosols shading the solar illumination as attested to by the elimination of the marine photosynthesizing plankton such a dark period must have affected life on land the apparent cold blooded non avian dinosaurs which were used to living in open terrains to absorb the solar illumination became inactive during the dark period and were incapable of withstanding predators this was in contrast to cold blooded crocodilians turtles and lizards that could hide in refuge sites on land and in the water dinosaur relics discovered in cretaceous polar regions were attributed to perennial residents surviving the nearly half year long dark winter despite their ability to leave the polar concentrations of disarticulated dinosaur bones were suggested as having resulted from a catastrophic burial of a population by floods however this should have fossilized complete skeletons alternatively herds of dinosaurs living in high latitudes might have been sexually driven to spend the half year of continuously illuminated polar summer for mating rather than for nourishment in which the lower latitudes provided as well the aggressive mating competitions would have left victims among the rivals and of young ones incidentally trampled over all being consumed and their skeletons disarticulated accordingly the alleged polar dinosaurs do not challenge the logical conclusion that the non avian dinosaurs were cold blooded as a result of which they became inactive and subjected to predation during the end cretaceous dark period

a guide to phanerozoic cold polar climates from high latitude ice rafting in the cretaceous the high latitude extent of warm climate indicators at certain times in earth history has been considered as evidence that the globe was ice free for long intervals despite theoretical considerations and results from numerical modelling experiments1 2 indicating that this was unlikely one of the warmest periods the cretaceous displays faunal and floral evidence for cool temperate to sub tropical conditions very near to the poles however our studies of lower cretaceous mudstones of central australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice rafting implying that high latitude ice was present at sea level strata of a similar origin of mid jurassic to mid cretaceous age occur on other continents that were positioned between 65 and 78 palaeolatitude indeed there is a record of high latitude ice rafting throughout the phanerozoic suggesting that ice was present on earth for much of its history and that ice free conditions could have been at most only episodic over the past 600 myr

paleolatitudes versus time for southern alaska paleomagnetic determinations of the inclination of the ancient geomagnetic field for localities in the alaska peninsula wrangellia chugach and kuskokwim tectonostratigraphic terranes of alaska show systematic northward motion from late cretaceous time until the present prior to this the ambiguity of polarity of the ancient geomagnetic field allow several interpretations however the preferred interpretation involves southerly motion of the terranes from triassic to early jurrassic time and steady northward motion from then up to the present the latitudinal rate is about 6 cm yr

moveout approximation for vertical seismic profile geometry in a 2d model with anisotropic layers i introduce a new explicit form of vertical seismic profile vsp traveltime approximation for a 2d model with non horizontal boundaries and anisotropic layers the goal of the new approximation is to dramatically decrease the cost of time calculations by reducing the number of calculated rays in a complex multi layered anisotropic model for vsp walkaway data with many sources this traveltime approximation extends the generalized moveout approximation proposed by fomel and stovas the new equation is designed for borehole seismic geometry where the receivers are placed in a well while the sources are on the surface for this the time offset function is presented as a sum of odd and even functions coefficients in this approximation are determined by calculating the traveltime and its first and second order derivatives at five specific rays once these coefficients are determined the traveltimes at other rays are calculated by this approximation testing this new approximation on a 2d anisotropic model with dipping boundaries shows its very high accuracy for offsets three times the reflector depths the new approximation can be used for 2d anisotropic models with tilted symmetry axes for practical vsp geometry calculations the new explicit approximation eliminates the need of massive ray tracing in a complicated velocity model for multi source vsp surveys this method is designed not for nmo correction but for replacing conventional ray tracing for time calculations

geological evidence for post 40 m y b p large scale northwestward displacement of part of southeastern alaska the leech river complex on southern vancouver island and schistose rocks on southern baranof island have very similar geologic histories both were derived from probable upper jurassic cretaceous terrigenous clastic rocks and minor associated volcanogenic rocks and chert each underwent 1 at least two penetrative deformations locally involving folding disruption and transposition of thinly layered sequences and 2 synkinematic low pressure buchan type metamorphism progressive metamorphic zones ranging from greenschist to amphibolite facies are related to granitic intrusive bodies deformation metamorphism and intrusion culminated about 40 to 42 m y ago apparently these units now separated by more than 1 100 km were once contiguous and lay at least as far south as the latitude of southern vancouver island shortly after 40 m y b p the allochthonous leech river complex was emplaced at the southern edge of vancouver island and the schists of baranof island and perhaps the entire chugach terrane began their long northwestward journey along a system of dextral transcurrent faults

herd structure in late cretaceous polar dinosaurs a remarkable new dinosaur tracksite denali national park alaska usa the discovery of a new tracksite of mostly hadrosaurid dinosaur footprints made by a herd living in an ancient high latitude continental ecosystem provides insight into the herd structure and behavior of northern polar dinosaurs and perspective on populations of large bodied herbivores in an arctic greenhouse world this tracksite occurs in the upper cretaceous cantwell formation in the alaska range denali national park alaska united states and it is the largest tracksite known from this far north preservation of the tracksite is exceptional most tracks regardless of size contain skin impressions and they co occur with well preserved plant fossils and invertebrate trace fossils of terrestrial and aquatic insects statistical analyses of the tracks show that individuals of four different age classes of hadrosaurids lived together in a large social group our research results independently corroborate the growth curve for hadrosaurids proposed by paleohistologists that suggests that these dinosaurs experienced a period of rapid growth early in their life history

southern polar forests the early cretaceous floras of victoria and their palaeoclimatic significance abstract a diverse fossil flora including cryptogams pteridosperms cycadales bennettitales ginkgoales coniferales and angiosperms occurs in early cretaceous fluvial and lacustrine strata in the otway and gippsland basins in southern victoria both evergreens e g araucarians cycads ferns and deciduous or semi deciduous forms e g certain pteridosperms and ginkgoales seem to have been represented certain ferns ginkgos and conifers grew to a large size overall the assemblages are typical of early cretaceous floras the associated fauna includes dinosaurs hypsilophodontids allosaurs lepidosaurs chelonians birds fish including the lungfish ceratodus and insects the evidence of the biota as a whole suggests a warm to cool temperate relatively equable climate of moderate seasonality with no widespread winter freezing the complex mesozoic apparent polar wander path apw indicated for australia places victoria in high to polar palaeolatitudes ca 70 85 s during the early cretaceous this apw path is supported by paths for other gondwana continents the existence of the victorian early cretaceous forest and biotic communities through polar nights of about two to five months duration is difficult to accept evergreen species would have required relative equability of light whatever the temperature the dinosaurs foliage throughout the year and the lungfish warm to temperate conditions without freezing in view of the consistency of mesozoic palaeomagnetic results for gondwanaland and the enigmatic presence of mesozoic and early cenozoic fossil floras and faunas in very high northern palaeolatitudes the possibility of a reduced obliquity of the ecliptic in mesozoic early cenozoic time should be considered

character distribution and tectonic significance of accretionary terranes in the central alaska range the central part of the alaska range near mount mckinley is composed of nine separate tectonostratigraphic terranes that were accreted in southern alaska during late mesozoic time these terranes now form long linear fault bounded belts that are subparallel to the denali fault on the north but oblique to the fault on the south the postaccretion right lateral offset along the denali fault system is about 200 km from north to south the major terranes are 1 yukon tanana terrane metasedimentary and metavolcanic rocks mostly undated but including rocks of known late paleozoic age polymetamorphosed with terminal events in late mesozoic 2 pingston terrane isoclinally folded upper triassic deep water silty limestone quartzite and carbonaceous slate folded with upper paleozoic phyllite chert tuff and minor limestone 3 mckinley terrane upper paleozoic flysch chert and minor limestone intruded by large gabbro sills and dikes and overlain by thick piles of triassic porphyritic pillow lava the top of the section is thick sequence of upper mesozoic conglomerate flysch chert and phyllite 4 dillinger terrane very thick sequence of strongly folded lower paleozoic micaceous sandstone turbidites graptolitic shale and deep water limestone locally overlain unconformably by jurassic fossiliferous sandstone or triassic pillow basalt 5 windy terrane heterogeneous assemblage of serpentinite basalt tuff and chert ophiolite with paleozoic and mesozoic flysch and blocks of mid paleozoic fossiliferous limestone 6 mystic terrane predominantly upper paleozoic flysch and conglomerate but also includes lower paleozoic graptolitic shale pillow basalt and shallow water limestone and upper paleozoic fossiliferous limestone sandstone chert and undated pillow basalt 7 chulitna terrane upper devonian ophiolite overlain by upper paleozoic chert volcanic conglomerate limestone and flysch capped by lower triassic limestone and upper triassic red beds basalt and interbedded basalt and limestone later mesozoic rocks are sandstone chert and argillite 8 westfork terrane jurassic chert sandstone conglomerate and triassic and jurassic crystal tuff 9 broad pass terrane upper paleozoic chert tuff and argillite with blocks of devonian and older limestone locally associated with serpentinite these diverse terranes of mixed oceanic and continental affinities are now juxtaposed to form a complex sequence of folded and faulted rootless nappes major suture zones between them are occupied by intensely deformed upper mesozoic flysch all of the terranes differ markedly from wrangellia the southermost coherent accreted terrane in alaska paleomagnetic measurements from triassic rocks prove that wrangellia originated near the equator probably in the southern heimsphere paleolatitudes for terranes in the central alaska range are not yet determined but other lines of evidence biogeographic and lithologic suggest large scale northern transport for some terranes

retrogressive fabric development during exhumation of the voltri massif ligurian alps italy arguments for an extensional origin and implications for the alps apennines linkage geological mapping coupled with structural investigations carried out in the voltri massif eastern ligurian alps italy provide new data for the interpretation of the tectonic context controlling main fabric development during exhumation of its high pressure core the voltri massif is here interpreted as a c 30 km long eclogite bearing asymmetric dome formed by the progressive verticalisation of the regional second phase mylonitic foliation developed during retrogressive greenschist metamorphic conditions in this light the exhumation history is driven by a ductile to brittle extensional process operating through low angle top to the w multiple detachment systems a late eocene early oligocene age for this extensional episode is proposed on the basis of structural correlations stratigraphic and radiometric constraints in this scenario the voltri massif is interpreted as an extensional domain developed to accommodate the late eocene early oligocene arching of the western alps northern apennines orogenic system

some limitations in using leaf physiognomic data as a precise method for determining paleoclimates with an example from the late cretaceous pautut flora of west greenland abstract plant parts of the late cretaceous west greenland pautut flora are derived from vegetation growing in lower delta plain delta upland and levee habitats a large river system drained the uplands and deposited leaves from species there and levee areas into a shallow bay setting the large drainage area of the rivers caused a great diversity of species to be preserved in the bay when these upland and levee species are combined with those that grew and were deposited in the lower delta plain areas 12 fern six cycad cycadeoid 1 ginkgoalean 35 conifer and over 85 angiosperm species represent the pautut flora when the paleotemperature derived from the angiosperm leaf margin ratio of the complete pautut flora 8 c is compared to other paleobotanical data and oxygen isotope values warm temperate to subtropical there is a serious discrepancy that puts the leaf physiognomic approach for precisely determining paleoclimate in the cretaceous in serious doubt also paleoclimatic interpretations based on the angiosperm leaf margin data of leaves from the lower delta plain species would indicate slightly cooler conditions than that suggested by the upper delta plain species leaf size would indicate wetter conditions in the lower delta plain even though other leaf features e g drip tips suggest moist conditions did occur in the upper delta plain these preservation enough that regional paleoclimate scenarios drawn from only one depositional setting or loclity can be erroneous a sampling size of less than 30 angiosperm species for a fossil flora also is suspect for reliably indicating climatic conditions unless the flora was originally impoverished of angiosperm species taphonomic factors play a significant role in fossil leaf preservation so collected fossil assemblages must closely represent the original vegetation before paleoclimatic interpretations based on leaf physiognomy can have a degree of credibility a limit to plausibility is especially significant in cretaceous floras because they have a limited diversity due to evolutionary constraints and appear to have consisted of more successional species than younger floras thus displaying intermediate climatic conditions moisture and arctic light levels further restrict determination of paleoclimatic conditions derived from leaf margin ratios and leaf size

a comparison of eocene climate model results to quantified paleoclimatic interpretations abstract the integration of climate model results and geologic information offers considerable potential for deriving greater insight into the geologic record in this study climate model results and quantified climatic interpretations derived from proxy data are compared to assess model capabilities and to examine proxy data interpretations atmospheric general circulation model experiments were used to produce a range of possible representative eocene climate states based on current knowledge of the eocene record the climate model experiments incorporate two idealized endmembers of eocene ocean surface temperature distributions characterized by very different latitudinal gradients model results are compared to quantified interpretations of the climate of early eocene north america in an attempt to identify one of the sea surface temperature distributions as more likely to have existed during the eocene the comparisons do not produce a conclusive match between inferred paleoclimatic information and any single case of model results but some interesting insights become apparent model predictions of mean annual temperature and mean annual precipitation compare favorably to interpretations from geologic evidence but there are large differences between model results and interpreted paleoclimatic parameters of minimum surface temperature and mean annual temperature range several possible causes for these differences are discussed

application of the fujita ziegler paleoclimate model early permian and late cretaceous examples abstract the fujita ziegler model is a new semi quantitative technique for reconstructing atmospheric circulation and resulting rainfall patterns of the geological past using uniformitarian assumptions in this paper we evaluate the performance of the model when applied to geographic and climatic conditions that were significantly different from the recent a late cretaceous maastrichtian reconstruction permits a test of the performance of the technique during a time that apparently lacked polar ice caps and steep latitudinal temperature gradients an early permian sakmarian reconstruction is used to evaluate the performance of the technique when the equator to pole temperature gradient was steep more like today but all major land masses had merged to form one large supercontinent pangea for both the maastrichtian and sakmarian the model produced more detailed retrodictions of surface air pressure and precipitation continuity than previously published paleoclimate reconstructions the results compare favorably with the known distribution of climatically sensitive sediments such as coals evaporites and phosphorites although the model considers complex relationships among land and sea distribution air pressure surface winds ocean currents and specific precipitation mechanisms it is still relatively simple and easy to apply therefore it is an excellent learning tool for the student of paleoclimate and should be an important technique to complement other methods of paleoclimate reconstruction

kinematics of the alpine arc and the motion history of adria the alps have been interpreted traditionally in terms of north or northwest directed convergence between africa and europe1 with adria the continental underpinnings of the adriatic sea and northern italy acting as a promontory of the african continent2 this has been supported by recent analyses of africa europe relative plate motions3 5 which indicate dominantly north south directed convergence during the tertiary phase of intracontinental shortening we show here however that kinematic indicators from alpine tectonites are difficult to reconcile with this motion history figs 1 and 2 and are explained best by roughly west northwest directed adria europe motion since about 70 million years ago combined with an arc normal pattern of motion driven by local body forces this implies that adria has moved independently of both africa and europe since at least the late cretaceous

three growth in the mesozoic and early tertiary and the reconstruction of palaeoclimates abstract evidence from the distribution and characteristics of fossil wood in the mesozoic and early tertiary indicates that a much warmer global climate prevailed in those times there appears to have been a broad zone of largely non seasonal climate stretching from about 32 n to 32 s palaeolatitudes in addition to this low latitude zone forest growth extended into very high palaeolatitudes where trees cannot grow at the present day a number of theories have been proposed to account for the palaeoclimate responsible for this distribution of forests most notable have been those involving changes in the amount of carbon dioxide in the atmosphere in the positions of the continents or in the obliquity of the earth s axis of rotation evidence from fossil forests indicates that a combination of the effects of an increased quantity of carbon dioxide in the atmosphere and the palaeopositions of the continents in the mesozoic and early tertiary appears at the moment to be the simplest explanation for the climate of those geological times without the need to invoke axial movement

western alpine back thrusting as subsidence mechanism in the tertiary piedmont basin western po plain nw italy abstract basin formation dynamics of the tertiary piedmont basin tpb are here investigated by means of cross section numerical modelling previous works hypothesised that basin subsidence occurred due first to extension oligocene and then to subsequent loading due to back thrusting miocene however structural evidence shows that the tpb was mainly under contraction from oligocene until post pliocene time while extension played a minor role furthermore thermal indicators strongly call for a cold flexure induced mechanism but are strictly inconsistent with a hot thermally induced mechanism our new modelling shows that the tpb stratigraphic features can be reproduced by flexure of a visco elastic plate loaded by back thrusts active in the western alps in oligo miocene times far field compression contributed to the tpb subsidence and controlled the basin infill geometry by enhancing basin tilting forebulge uplift and erosion of the southern margin of the basin these results suggest that the tpb subsidence is the result of a combination of mechanisms including thrust loading and far field compressional stresses

structural evolution of a brianconnais cover nappe the caprauna armetta unit ligurian alps italy abstract the caprauna armetta unit cau is a brianconnais cover nappe emplaced on the external margin of the ligurian brianconnais zone a structural analysis of the nappe indicates that there are four superposed deformations d 1 d 4 d 1 produced large recumbent isoclinal folds associated with a strong axial plane cleavage and a sw trending lineation these folds can be related to a sw directed overthrust shear d 2 produced open to moderately tight folds with subvertical axial planes overturned towards the northeast d 3 and d 4 are represented by large wavelength open folds affecting only the large scale setting of the nappe a finite strain map of the nappe has been compiled using data from an oolitic limestone layer the measured strains appears to be essentially the product of the d 1 phase the measured ellipsoids are generally triaxial the trend of the finite strain x axes is towards the southwest prolate ellipsoids with very high r xz ratios occur on the inverted limbs and sometimes near the hinge zones of the anticlinal f 1 folds oblate ellipsoids are prevalent on the normal limbs this pattern of finite strain resulted from deformation in a ductile shear zone generated within the tectonic units trailed at the base of the huge helminthoid flysch nappe during its motion towards the foreland

cretaceous climatic oscillations in the bering area alaska and koryak upland isotopic and palaeontological evidence abstract new isotopic palaeotemperatures estimated from 18 o values of early albian latest campanian and early maastrichtian ammonoid shells of southern alaska as well as our previously published data on the cretaceous of the koryak upland have been used to reconstruct palaeonvironmental changes in the bering area significant seasonal contrast marked in alaska and the adjacent area during the early albian as well as the coniacian was partly connected apparently with the possible penetration of cooler waters from the polar area via the strait of alaska data suggest that the bering land bridge existed during the post aptian cretaceous with the exception of the early albian and coniacian both the stable isotope and the floral data on the post aptian cretaceous of the bering area suggest the existence of warm climatic conditions in the late albian latest cenomanian coniacian santonian to early campanian latest campanian and also late early maastrichtian recurrent terrestrial cooling in northern alaska reflected in the composition of corresponding floras took place possibly because of a barrier to poleward oceanic heat transport via the western interior seaway wis of north america during the turonian and santonian through early campanian then during the late maastrichtian through danian