earthquakes in northern europe in 1375 1989 abstract an updated version of the catalogue of earthquakes in northern europe is presented it comprises events inside a region window of about 55 80 n and 10 w 45 e covering a 615 year period from 1375 to 1989 the data have been compiled using all the available historical publications catalogues studies and reports of the region and for events from 1984 to 1989 a regional seismic parameter database maintained by the institute of seismology of the university of helsinki the number of events exceeds 5200 of which more than 40 have been registered since 1980 the huge increase of event reports is the result of the installation of new high frequency networks for microearthquake studies and the upgrade of the seismic instrumentation because of the different degree of accuracy and homogeneity of the parameter data the events were divided into historical 1375 1964 and instrumental 1965 1989 datasets the source parameters are mainly macroseismic for historical events and obtained by iterative location procedure for instrumental data by assuming internal homogeneity between the different regional magnitude scales we estimated the catalogue to be complete for events with magnitude 4 5 since the 1880 s magnitude 4 0 4 4 since the 1940 s and magnitude 3 5 3 9 since the 1970 s although the distribution of seismicity exhibits similar patterns in both datasets the clustering of epicenters and offshore seismicity is more distinct in the instrumental period the occurrence of the greatest events can be seen more clearly in the historical data the earthquake epicenters are concentrated in the geologically younger tectonic provinces in the western part of the region and follow with some exceptions the tectonic fracture and fault zones in the fennoscandian area 80 of the earthquakes occurred in the upper 20 km of the earth s crust the deepest epicenters are in the southwestern corner of the region where the crust is thinnest

origin of co2 rich fluid inclusions in leucosomes from the skagit migmatites north cascades washington usa co2 ch4 fluid inclusions are present in anatectic layer parallel leucosomes from graphite bearing metasedimentary rocks in the skagit migmatite complex north cascades washington petrological evidence and additional fluid inclusion observations indicate however that the skagit gneiss was infiltrated by a water rich fluid during high temperature metamorphism and migmatization co2 rich fluid inclusions have not been observed in skagit metasedimentary mesosomes or melanosomes meta igneous migmatites or unmigmatized rocks and are absent from subsolidus leucosomes in metasedimentary migmatites the observation that co2 rich inclusions are present only in leucosomes interpreted to be anatectic based on independent mineralogical and chemical criteria suggests that their formation is related to migmatization by partial melting although some post entrapment modification of fluid inclusion composition may have occurred during decompression and deformation the generation of the co2 rich fluid is attributed to water saturated partial melting of graphitic metasedimentary rocks by a reaction such as biotite plagioclase quartz graphite al2sio5 water rich fluid garnet melt co2 ch4 the presence of co2 rich fluid inclusions in leucosomes may therefore be an indication that these leucosomes formed by anatexis based on the inferences that 1 an influx of fluid triggered partial melting and 2 some episodes of fluid inclusion trapping are related to migmatization by anatexis it is concluded that a free fluid was present at some time during high temperature metamorphism the infiltrating fluid was a water rich fluid that may have been derived from nearby crystallizing plutons because partial melting took place at pressures of at least 5 kbar abundant free fluid may have been present in the crust during orogenesis at depths of at least 15 km

postglacial uplift neotectonics and seismicity in fennoscandia abstract fennoscandia has experienced major uplift in postglacial time which is assumed to reflect a glacial isostatic process connected to the melting of the last ice sheets extensive modelling of the isostatic movements show that the applied deglaciation and uplift model fit the observations well there are however areas with significant deviations between uplift measurements and regional model predictions the misfit between observations and the isostatic uplift modelling is interpreted here to reflect a tectonic component of the uplift the objective of the present investigation is to isolate this tectonic uplift component interestingly enough the areas found partly correspond to areas with pronounced seismic activity and the assumption that the postglacial rebound is responsible for much of the observed onshore seismicity is substantiated we conclude that there seems to be present day deformation along the shoreline of mid norway southern norway shoreline and mountain areas and along the swedish east coast with the centre northeast of the gulf of bothnia that cannot be explained by glacial isostasy not all of the deformations in these areas are necessarily co seismic the study suggests that such vertical deformations are small in magnitude and overprint the glacial rebound the deformations may be a consequence of the plio pleistocene erosional pattern which is of glacial origin

a comparison of gcm simulated cretaceous greenhouse and icehouse climates implications for the sedimentary record abstract two general circulation model simulations of mid cretaceous climate are presented one representing a greenhouse and the other representing an icehouse world through a comparison of greenhouse and icehouse palaeoclimates differences in processes which are intrinsically linked with climate such as continental weathering and snow and ice accumulation may be observed a number of conspicuous and discrete climatic differences can be seen between the two simulations which may be translated into a number of identifiable signatures in the sedimentary record the climate at mid high latitudes in the icehouse simulation was more arid than the greenhouse simulation and could result in deposition of smectite dominated clay suites in contrast the climate of low latitudes of the icehouse simulation resulted in a moister climate than the greenhouse simulation which could affect the weathering regimes and result in deposition of kaolin dominated clay suites thus cool climate episodes do not necessarily result in a global increase in aridity the icehouse simulation predicts a small permanent icecap at high latitudes which could account for the origin of dropstones in marine sediments furthermore a sea level fall as a consequence of an accumulation of ice at high latitudes may also increase continentality and surface albedo which may also contribute to the causes of the drier climate at high latitudes hurricanes are likely to be more frequent in greenhouse than icehouse climates mid latitude depressions also important for generating storms are likely to be both intense and frequent during icehouse and greenhouse periods of the middle cretaceous

middle cretaceous calcareous nannofossil biogeography and preservation in the atlantic and indian oceans implications for paleoceanography abstract the quantitative study of calcareous nannofossil preservation and biogeographic distribution puts constraints on paleoceanographic models for the atlantic and indian oceans during the middle cretaceous we establish a dissolution ranking of middle cretaceous calcareous nannofossils based on susceptibility to dissolution a positive correlation of organic carbon content of the sediments and the relative abundance of watznaueria indicates that much of the carbonate dissolution was caused by the release of carbon dioxide during oxidation of organic matter the depth distribution of the most dissolution resistant species watznaueria barnesae shows relative abundance maxima at the deepest sites and a maximum where intermediate waters impinge on slopes this reflects stagnant oxygen poor bottom waters and possibly a mid water oxygen minimum zone with increased deposition and catabolic breakdown of organic matter factor analyses are performed on various data sets for three different time slices ranging in age from late aptian to early albian middle albian and late albian to cenomanian the resulting factors can be related to paleoceanographic conditions such as colder water at high latitudes high fertility upwelling conditions and neritic conditions for all three time intervals a wide tropical to subtropical zone was flanked by boreal and austral zones upwelling conditions probably existed along the north african margin and over the falkland plateau zonal upwelling is tentatively postulated for the northwestern and northeastern margin of the north atlantic in the middle albian and for the eastern margin of the north atlantic off western europe for the late albian to cenomanian we speculate on surface water current patterns location of upwelling regions and haline driven deep circulation for the middle cretaceous

fluid inclusions in high grade anatectic metamorphites fluid inclusions have been studied by microthermometry in metapelites and metabasites which have undergone partial melting in the transition zone from amphibolite to granulite facies mobilizates contain far more abundant and larger fluid inclusions than non mobilized or restite layers and these inclusions occur as several generations of well defined and chemically contrasted fluids carbonic co 2 ch 4 and hydrocarbon aqueous h 2 o nacl and n 2 a garnet bearing mobilizate in amphibolite contains 4 generations of relatively pure fluids most of them trapped after peak metamorphic conditions in the following p t domains co 2 and n 2 p 2 8 kbar t 550 850 c ch 4 p 1 2 kbar t 400 550 c h 2 o p t 120 400 c

complex response of dinoflagellate cyst distribution patterns to cooler early oligocene oceans previous studies have made extensive use of dinoflagellate cysts to reconstruct past sea surface temperature sst analysis of associations of dinoflagellate cysts using two new ocean datasets for the mid eocene bartonian and early oligocene rupelian reveals clear latitudinally constrained distributions for the bartonian but unexpected changes in their rupelian distribution a significant number of species with low and mid latitude northern hemisphere occurrences in the bartonian extend their northward ranges in the rupelian including some forms characterised as warm water by previous studies this suggests either that dinoflagellates are faithfully tracking a complex oceanographic response to rupelian cooling or that dinoflagellate sensitivity adaptability to a range of ecological variables means that at a global scale their distributions are not primarily controlled by sea surface temperature variability previous use of dinoflagellate cysts for palaeoclimate work has relied on rather subjective and inconsistent identification of warm and cold water forms rather than comprehensive analysis of community associations at the global scale it is clear from this study that a better understanding of the palaeo ecology of dinoflagellates and their cysts is required rupelian dinoflagellate cyst distribution may reflect changes in a range of environmental variables linked to early oligocene climate cooling for example changes in nutrient fluxes triggered by glacially induced base level fall complex reorganisation of ocean current systems between the bartonian and rupelian or muted changes to rupelian summer ssts in the northern hemisphere that have previously been reported many extant dinoflagellate species also exhibit relatively broad temperature tolerance moreover they have potentially extensive cryptic diversity and are able to produce dormant cysts during short lived environmental deterioration all of which may act to limit the value of undifferentiated dinoflagellate cyst assemblages for identifying climate signals

origin of the skagit migmatites north cascades range washington state stromatic and schlieren type migmatites are a major lithology in the type section of the skagit gneiss complex in the north cascades range of washington state usa migmatite mesosomes are chiefly biotite schist amphibolite and orthogneiss in decreasing order of abundance leucosomes are predominantly leucotrondhjemites with a very limited range of composition that is nearly independent of associated mesosome type melanosomes consisting mainly of biotite and or hornblende garnet are inconsistently developed and absent in places the age of migmatization is not well established but appears to be late cretaceous or early tertiary this is also the age of syntectonic tonalite to trondhjemite intrusives that are predominant in most parts of the skagit complex although temperatures in excess of 700 c and pressures as high as 10 kb occurred there is no evidence for widespread partial melting of the mesosomes with which the migmatites are closely associated mass balance calculations preclude an origin by injection of a silicate melt or hydrothermal fluid unless accompanied by metasomatic replacement reactions mass balance relationships also show that the skagit migmatites could not have formed solely by closed system processes such as partial melting or metamorphic segregation unless the mesosomes present were not the protolith from which the migmatites formed field petrographic and geochemical data indicate that an origin by migmatization of a missing mesosome is quite unlikely the most feasible process of migmatization appears to be infiltration of an aqueous fluid into a metamorphic protolith along fracture or foliation planes this triggers a variable degree of metamorphic segregation or possibly minor partial melting unmixing of leucosomes and melanosomes from the mesosome protolith must be accompanied by metasomatic replacement but the total mass transfer required is only a few wt

origin of k poor leucosomes in a metasedimentary migmatite complex by ultrametamorphism syn metamorphic magmatism and subsolidus processes two types of stromatic leucosomes are identified in metasedimentary rocks from the skagit migmatite complex north cascades washington state u s a both types are trondhjemitic and appear similar in outcrop but although both contain low abundances of ree one type consists of leucosomes that are relatively ree enriched compared to the other and contains 1 small 700 c water rich fluid present inferences about the origin of the above listed mineralogical and fluid inclusion features and modeling of leucosome trace element abundances the second type of leucosome is interpreted to have formed entirely by subsolidus processes e g metamorphic differentiation because these leucosomes lack features consistent with an origin by partial melting k poor tonalitic trondhjemitic leucosomes associated with metasedimentary biotite bearing source rocks may form by water saturated partial melting or by subsolidus processes both general leucosome forming mechanisms may operate at different times during upper amphibolite facies regional metamorphism partial melting may be initiated by syn metamorphic magmatic activity if crystallizing plutons serve as external sources of the water rich fluid necessary for ultrametamorphism in the middle crust during orogenesis large scale migmatite complexes such as the skagit migmatites may form at least in part in response to contact effects of plutonism associated with high grade metamorphism so although migmatite complexes are a volumetrically substantial part of many orogenic belts they may not themselves represent a significant original source of magma for larger scale igneous bodies

digital isochrons of the world s ocean floor we have created a digital age grid of the ocean floor with a grid node interval of 6 arc min using a self consistent set of global isochrons and associated plate reconstruction poles the age at each grid node was determined by linear interpolation between adjacent isochrons in the direction of spreading ages for ocean floor between the oldest identified magnetic anomalies and continental crust were interpolated by estimating the ages of passive continental margin segments from geological data and published plate models we have constructed an age grid with error estimates for each grid cell as a function of 1 the error of ocean floor ages identified from magnetic anomalies along ship tracks and the age of the corresponding grid cells in our age grid 2 the distance of a given grid cell to the nearest magnetic anomaly identification and 3 the gradient of the age grid i e larger errors are associated with high age gradients at fracture zones or other age discontinuities future applications of this digital grid include studies of the thermal and elastic structure of the lithosphere the heat loss of the earth ridge push forces through time asymmetry of spreading and providing constraints for seismic tomography and mantle convection models

equable climates during earth history eocene and cretaceous climate model experiments demonstrate that regardless of conditions of warm polar oceans differences in pole to equator surface temperature gradient or topography above freezing surface temperatures in winter for continental interiors at middle to high latitudes cannot be maintained continental interiors will have cold winter temperatures even during globally warm periods unless currently unrecognized forcing factors influenced past climates if model simulations of eocene and cretaceous climates are accurate the term equable as it applies to paleoclimate should be reconsidered

geochemical modeling of low melt fraction anatexis in a peraluminous system the pena negra complex central spain abstract a study was made of the chemical fractionation associated with four cases of anatectic segregation of low melt fraction cordieritic granites from migmatized meta greywackes the aims of the study were to 1 reveal the fractionation patterns of major and trace elements 2 compare the major element chemistry of leucogranites and the quantitative behavior of source minerals during anatexis inferred by mass balance adjustment with available experimental data for peraluminous systems and 3 discuss the behavior of trace elements in crustal melting by comparing the chemically determined composition of leucogranites with the results of three fractionation models two of these assume a perfect diffusive behavior of trace elements within residual solids but they use a different set of distribution coefficients the third assumes a perfect nondiffusive behavior in relation to their source rocks the leucogranites are strongly depleted in li transition elements and light rare earth elements but enriched in k2o sio2 and ba the k rb ratio in leucogranites is higher than in sources and reaches values typical of high grade metamorphism mass balance analysis using the anatexis mixing model shows that the chemistry of cordierite leucogranites is compatible with its having originated by closed system water undersaturated anatexis on previously migmatized meta greywackes leaving a residue enriched in cordierite plus biotite and exhausted in k feldspar biotite melts congruently unless important amounts of sillimanite were also present in the source compared with experimental melts obtained from sources with the same chemical composition but with a different femic mineralogy biotite sillimanite instead of cordierite biotite the pena negra leucogranites are richer in k2o and mgo with a lower fe fe mg ratio the differences in magnesium are believed to result from the changes in the mineral assemblage of the source rocks however the differences in potassium contents are still not well understood the behavior of trace elements during anatexis cannot be modeled by trace element fractionation equations because of the sluggish diffusion kinetics of trace elements at the temperature of anatexis making the melting rate of minerals greater than the diffusion rate of trace elements within minerals the behavior of trace elements essentially consists in following that of the minerals containing them

what controls partial melting in migmatites the layers of six stromatic migmatites from northern western and central europe display small but systematic chemical and mineralogical differences at least five of these migmatites do not show any signs of largescale metamorphic differentiation metasomatism or segregation of melts it is concluded therefore that the compositional layering observed in most of the investigated migmatites is due to compositional differences inherited from the parent rocks almost isochemical partial melting seems to be the most probable process transforming layered paragneisses metavolcanics or schists into migmatites the formation of neosomes is believed to be caused by higher amounts of partial melts formed due to higher amounts of water moving into these layers the neosomes have less biotite and more k feldspar if k feldspar is present at all than the adjacent mesosomes these differences are small but systematic and seem to control the access of different amounts of water to the various rock portions petrographical observations chemical data and theoretical considerations indicate a close relationship between rock composition rock deformation transport of water partial melting and formation of layered migmatites

palaeobiogeography of early cretaceous berriasian barremian calcareous nannoplankton in order to assess early cretaceous nannoplankton biogeography we studied a series of sites which provide a north south transect across the atlantic ocean supplemented by sections from the north sea basin barents sea falkland plateau weddell sea antarctica argo abyssal plain nw of australia and neuquen basin argentina quantitative assemblage data were gathered from each site for seven time slices within the berriasian to barremian interval each horizon being determined by a nannofossil datum trends in species relative abundance and measures of diversity evenness and richness provide revealing biogeographic information a broad low to mid palaeolatitude zone 50 degrees n 50 degrees s is flanked in both northern and southern hemispheres by distinct high palaeolatitude zones major changes in assemblage abundance and composition occur across a sharp biogeographic front at around 50 degrees n and s palaeolatitude high palaeolatitude assemblages are lower in species richness and diversity and characterised by the presence of abundant typically bipolar taxa e g crucibiscutum salebrosum a less distinct biogeographic boundary at similar to 40 degrees n is distinguished by the presence absence of rarer but biogeographically significant taxa many of which have previously been assigned to boreal or tethyan provinces continental shelf sites are characterised by lower diversity assemblages with common to dominant diagnostic taxa which vary with palaeolatitude nannoconus and micrantholithus at low palaeolatitudes and biscutum constans and zeugrhabdotus spp at higher palaeolatitudes the latter two taxa are considered to be indicative of elevated surface water fertility and the former two may have been similarly adapted the genus watznoueria is ubiquitously dominant giving the populations an unevenness which appears to be a common feature throughout coccolithophore history c 2000 published by elsevier science b v all rights reserved

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

a re examination of the seismicity of michigan abstract according to reports on felt shocks and those recorded by instruments 105 seismic events have been reported as occurring within michigan from the 1700 s to the present of these 41 instrumental events are due to chemical explosions detonated in experiments during 1964 1966 of the remaining events most of those reported from the upper peninsula are related to mining in the lower peninsula most events can be shown or strongly inferred to be cryoseisms atmospheric shock waves from explosions or aircraft or errors in location or reporting at least four and perhaps up to eight events are thought to be tectonic earthquakes and occur in the southernmost part of the state primarily in western lake erie and the southwestern corner of the state or in lake superior this study indicates that the seismicity level within michigan is very low and that there is no evidence to substantiate either a tectonically active michigan basin seismic zone or the extension of the midcontinent seismic zone into keweenaw peninsula in addition these results suggest that earthquake catalogs for weakly seismic regions may be contaminated with non tectonic and even non seismic events thirty earthquakes occurring outside the state have also been reported in michigan these lie primarily along a line connecting the st lawrence seaway and the new madrid zone of missouri

temporal and compositional differences between subsolidus and anatectic migmatite leucosomes from the quetico metasedimentary belt canada migmatites in the quetico metasedi mentary belt contain two types of leucosome 1 layer parallel leucosomes that grew during deformation and prograde metamorphism these are enriched in si02 sr and eu but depleted in ti02 fe203 mgo cs rb ree sc th zr and hf relative to the quetico metasediments 2 discordant leucosomes that formed after the regional folding events when metamorphic temperatures were at their peak these are enriched in rb ba sr and eu but display a wide range of lree th zr and hf contents relative to the quetico metasediments layer parallel leucosomes formed by a sub solidus process termed tectonic segregation this stress induced mass transfer pfocess began when the quetico sediments were deformed during burial and continued whilst the rocks were both stressed and heterogeneous sub solidus leucosome compositions are consistent with the mobilization of quartz and feldspar from the host rocks by pressure solution the discordant leucosomes formed by partial melt ing of the quetico metasediments possibly dur ing uplift of the belt the range of composition displayed by the anatectic leucosomes arises from crystal fractionation during leucosome emplacement some anatectic leucosomes pre serve primary melt compositions and have smooth ree patterns but those with negative eu anomalies represent fractionated melts and others with positive eu anomalies represent accumulations of feldspar plus trapped melt

relocating the historical 1951 hualien earthquake in eastern taiwan based on tide gauge record summary a sequence of large earthquakes happened along the longitudinal valley in eastern taiwan in 1951 thefirstthree andlargest earthquakestookplaceneartheharbourcityofhualienatthe northerntipofthevalleyduringthefirstday thesecondofwhich eventii severelydamaged the city the epicentre of event ii had previously been allocated at some 15 km offshore which would result in a vertical subsidence of the hualien city according to model calculations for the supposed seismic source mechanism however the hualien tide gauge record speaks the opposite the site experienced a co seismic uplift by 255 mm due to event ii we conduct a series of numerical grid search simulations and determine a most likely scenario for the earthquake sequence we assert that event ii s hypocentre was actually on land rather than offshore right along the recognized active milun fault below the city of hualien at a very shallow depth this result advances our understanding of the spatio temporal seismotectonic behaviour associated with these historical events and is important towards the assessment of the potential seismic and tsunami hazards of the region

fish tooth δ18o revising late cretaceous meridional upper ocean water temperature gradients the oxygen isotope composition of fossil fi sh teeth a paleo upper ocean temperature proxy exceptionally resistant to diagenetic alteration provides new insight on the evolution of the low to middlelatitude thermal gradient between the middle cretaceous climatic optimum and the cooler latest cretaceous period the new middle cretaceous low to middle latitude thermal gradient agrees with that previously inferred from planktonic foraminifera 18o recovered from deep sea drilling project and ocean drilling program drilling sites although the isotopic temperatures derived from 18o of fish teeth are uniformly higher by 3 4 c in contrast our new latest cretaceous thermal gradient is markedly steeper than those previously published for this period fish tooth 18o data demonstrate that low to middle latitude thermal gradients of the middle cretaceous climatic optimum and of the cooler latest cretaceous are similar to the modern one despite a cooling of 7 c between the two periods our new results imply that no drastic changes in meridional heat transport are required to explain the late cretaceous climate based on climate models such a cooling without any change in the low to middle latitude thermal gradient supports an atmospheric co2 decrease as the primary driver of the climatic evolution recorded during the late cretaceous

cretaceous climate a comparison of atmospheric simulations with the geologic record abstract atmospheric simulations using realistic cretaceous geography 100 million years ago suggest that paleography is an important factor governing the nature of the circulation the simulated cretaceous atmospheric circulations are markedly different both from the present day atmospheric circulation and from the classical hypotheses of a weaker circulation and poleward displacement of circulation features e g the subtropical high therefore they pose specific questions which can be tested against the geologic record aspects of the cretaceous simulations are verified in comparisons with the geologic record the simulations serve to guide areas of future paleoclimatic research and to formulate better the nature of the problem of warm equable climates

modelling the primary control of paleogeography on cretaceous climate the low thermal gradients and clement winters characterizing climates of the cretaceous period reveal that the climate system has modes of behaviour quite different from the present recent proxy data analyses suggest that some aspects of climate change within the cretaceous appear to be decoupled from co2 evolution at the geological time scale here we investigate the impact of paleogeography on the global climate with the climate model foam using a early mid and late cretaceous continental configuration we find that changes in geography from the early to mid to late cretaceous cause a large decrease of the seasonal cycle first order identified processes are the decreased continentality of the mid to high latitudes from the mid cretaceous and the increase of the latent heat transport into the winter hemisphere which induce a wetter and a cloudier atmosphere capable of diminishing the winter cooling of the continents owing to the modifications of the seasonal cycle in response to the tectonic forcing the equator to pole thermal gradient is reduced from the early to mid to late cretaceous we nevertheless still do not succeed in simulating warm enough polar temperatures and a definitive theory still waits for an integrated approach explicitly accounting for each factor influencing the thermal gradient ocean dynamics stratospheric clouds and vegetation our study also suggests a mechanism that can weaken the correlation between co2 and climate changes during the cretaceous as evolving geography from the early to late cretaceous through the response of the water cycle and the changes in the thermal gradient results in a 3 8 c global warming at a constant atmospheric co2 level this demonstrates that the paleogeography may affect the relation between pco2 and the climate history and consequently has to be accounted for when linking the atmospheric co2 evolution and the climate record at geological time scales

estimating locations and magnitudes of earthquakes in eastern north america from modified mercalli intensities we use 28 calibration events 3 7 m 7 3 from texas to the grand banks newfoundland to develop a modified mercalli intensity mmi model and associated site corrections for estimating source parameters of historical earthquakes in eastern north america the model batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mathrm mmi 1 41 1 68 times mathbf m 0 00345 times delta 2 08 mathrm log delta end document where is the distance in kilometers from the epicenter and m is moment magnitude provides unbiased estimates of m and its uncertainty and if site corrections are used of source location the model can be used for the analysis of historical earthquakes with only a few mmi assignments we use this model mmi site corrections and bakun and wentworth s 1997 technique to estimate m and the epicenter for three important historical earthquakes the intensity magnitude m i is 6 1 for the 18 november 1755 earthquake near cape ann massachusetts 6 0 for the 5 january 1843 earthquake near marked tree arkansas and 6 0 for the 31 october 1895 earthquake the 1895 event probably occurred in southern illinois about 100 km north of the site of significant ground failure effects near charleston missouri manuscript received 14 march 2002

late cretaceous oceans and the cool tropic paradox oxygen isotopic proxies of paleo sea surface temperatures ssts suggest that maastrichtian about 66 million years ago tropical ssts were lower than those of today they also demonstrate that maastrichtian latitudinal sst gradients were much lower than those of the present the low maastrichtian sst gradients indicate that meridional heat transport was much greater or latitudinal differences in the balance of radiation to and from the sea surface were much less extreme during the latest cretaceous than they are today or that both conditions were true these findings challenge traditional interpretations of greenhouse late cretaceous climates

water saturated and undersaturated melting of metaluminous and peraluminous crustal compositions at 10 kb evidence for the origin of silicic magmas in the taupo volcanic zone new zealand and other occurrences

late albian dinoflagellate cyst paleobiogeography as indicator of asymmetric sea surface temperature gradient on both hemispheres with southern high latitudes warmer than northern ones abstract late albian temperature sensitive dinoflagellate cysts are characterized in order to better understand mid cretaceous sea surface temperature gradients distribution maps of thirty seven species recovered from one hundred fifty outcrops and deep sea drilling holes odp dsdp sites located from low and high paleolatitudes over the two hemispheres 75 n 70 s are encountered fifty years of published data available in eighty seven articles have been considered and synthesized using a database coupled with a geographical information system gis the continuous and disjoint biogeographic patterns of dinocyst species along latitudes define seven climatic belts four in the northern hemisphere high mid high mid low low latitude belts and three in the southern hemisphere low mid low mid high latitude belts dinocysts restricted along latitudes are temperature sensitive species limit ranges of temperature sensitive dinocysts of mid low and mid high latitude belts reveal mixing belts located at 40 45 n and 50 70 s they represent major palaeofrontal systems as paleosubtropical fronts with strongly mixed water column the northern frontal system 40 45 n was located as in the modern ocean the large southern frontal system 50 s 70 s was 10 20 poleward to antarctica semi quantitative temperature range limits for mid cretaceous dinoflagellates and sst gradients in the two hemispheres are suggested by setting dinocyst climatic belts against estimated 18o temperature curve from fish teeth a paleoecological classification is suggested latitudinal distribution of extant temperature sensitive dinoflagellate cysts follows the asymmetric modern temperature gradient asymmetric latitudinal ranges of late albian dinocyst species of mid low latitude belts restricted between 45 n and 70 s demonstrate asymmetric temperature gradients with southern high latitudes being warmer than northern high latitudes

on the origin of co2 rich fluid inclusions in migmatites nearly pure co2 fluid inclusions are abundant in migmatites although h2o rich fluids are predicted from the phase equilibria processes which may play a role in this observation include 1 the effects of decompression on melt 2 generation of a co2 bearing volatile phase by the reaction graphite quartz biotite plagioclase melt orthopyroxene co2 rich vapour 3 selective leakage of h2o from co2 h2o inclusions when the pressure in the inclusion exceeds the confining pressure during decompression and 4 enrichment of grain boundary vapour in co2 by subsolidus retrograde hydration reactions

melting and diffusion processes in closed system migmatization estimated variations in mineral concentrations across leucosomes suggest that leucosomes are generated during anatexis by a diffusive exchange between the leucosome and the mesosome and not by the migration of melt from the mesosome however the presence of melt is a precondition for the diffusive exchange to take place initially a crack is formed due to shear stress the formation of a crack allows a diffusive exchange to take place through the melt which causes melting of minerals situated near the crack the diffusive exchange of material is less efficient in the mesosome where the melt is isolated at grain corners and edges the microcline enrichment of some granitic leucosomes is thought to be due to the diffusive depletion of the mesosome caused by growth of alkali feldspar during the consolidation of the migmatite in general it seems unnecessary to invoke concentrations of water in the leucosome or the intrusion of external fluids or magmas for migmatite formation

chemical exchange in migmatites during cooling abstract the chemistry of the leucosome components in limited size migmatitic associations is generally believed to reflect the composition of the partial melt that could have been extracted to yield an anatectic magma several well documented studies of migmatites indicate that the distributions of some trace elements in leucosome melanosome pairs are inconsistent with equilibrium partial melting but are rather in agreement with chemical reequilibration during cooling in migmatites the liquid fraction does not leave the system this may induce an alteration of the chemical composition of the whole migmatite system by extensive chemical exchange between the liquid and the solid residue during cooling if this is the case the leucosome and melanosome components are not representative of the chemical composition of the liquid and solid residue respectively at the time of partial melting a rough evaluation of the residences time of the melt fractions in cooling in situ migmatitic bodies yields minimum estimates of 1 to 10 ma for such time spans the characteristics distances of diffusion distances of diffusion induced chemical transfer exceed the sizes of individual mineral grains which is consistent with a re equilibration process the release of latent heat of crystallization in cooling migmatitic systems and the presence of an interstitial liquid phase are critical in determining the extent and scale of chemical exchange the mechanism involves 1 reducing the cooling rate and 2 promoting the efficiency of chemical diffusion through the liquid phase thus some doubt is cast on the ability of small scale migmatitic systems to provide relevant information about chemical mass balance during partial crustal melting

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

earthquake of 4 november 1898 in northern europe new insights 1 the earthquake of 4 november 1898 utc is a rare event in terms of the size of the area of perceptibility that extended to finland and sweden located in the intraplate northern europe previously unknown macroseismic reports were discovered in a thorough search of the contemporary press in this study the comprehensive collection of written documentary records is used to prepare an intensity data point map the slightly damaging intensities 5 5 6 and 6 on the european macroseismic scale are distributed over a larger area than outlined earlier this is attributed to the amplification of ground shaking by the soil characteristics in the river valleys where habitation concentrated at that time the new epicenter is located within a north south oriented seismicity trend that shows frequent microearthquakes and runs parallel to a mapped shear zone the magnitude of the main shock is inferred to be within the range from 4 4 to 4 7 and the magnitude of the immediate aftershock is inferred to be between 3 7 and 4 1 a theoretical relationship of intensity attenuation is employed in the inference of the magnitude the macroseismic reports show that earthquakes of this size posed an indirect hazard of fire to the dwellings in a region where earthquake related problems have previously been considered absent

the relationship between neogene dinoflagellate cysts and global climate dynamics abstract the neogene period 23 03 2 58 ma underwent a long term relatively gradual cooling trend culminating in the glacial interglacial climate of the quaternary palaeoclimate studies on the neogene have provided important information for understanding how modern patterns of atmospheric and oceanic circulation developed and how they may relate to wider environmental change here we use a newly created global database of neogene dinoflagellate cysts the tertiary oceanic parameters information system topis to investigate how dinoflagellate cysts recorded the cooling of neogene surface marine waters on a global scale species with warm and cold water preferences were determined from previously published literature and extracted from the database percentages of cold water species were calculated relative to the total number of species with known temperature preferences from each site and compared throughout the neogene at differing latitudes overall the percentage of cold water species increases gradually through the neogene this trend indicates a gradual global cooling that is comparable to that reported from other marine and terrestrial proxies this also demonstrates the use of dinoflagellate cysts in determining temperature change on both extended temporal and wide geographical scales the increase in the percentage of cold water species of dinoflagellate cysts recorded worldwide from the early and middle miocene to the late pliocene indicates a global scale forcing agent on neogene climate such as co2

neogene dinoflagellate cysts and acritarchs from the high northern latitudes and their relation to sea surface temperature organic walled dinoflagellate cysts and acritarchs are a vital tool for reconstructing past environmental change in particular in the neogene of the high northern latitudes where marine deposits are virtually barren of traditionally used calcareous microfossils yet only little is known about the paleoenvironmental value of fossil assemblages that do not have modern analogues so that reconstructions remain qualitative thus extracting their paleoecological signals still poses a major challenge in particular on pre quaternary timescales here we unravel the relationship between species relative abundance and sea surface temperature for extinct dinoflagellate cyst and acritarch taxa from the neogene of the iceland sea using palynological assemblages and organic geochemical alkenone data generated from the same set of samples the reconstructed temperatures for the miocene to pliocene sequence of ocean drilling program site 907 range from 3 to 26 c and our database consists of 68 dinoflagellate cyst and acritarch samples calibrated to alkenone data the temperature range of five extant species co occurring in the fossil assemblage agrees well with their present day distribution providing confidence to inferred temperature ranges for extinct taxa the 14 extinct dinoflagellate cyst and acritarch species clearly exhibit a temperature dependency in their occurrence throughout the analysed section the dinoflagellate cyst species batiacasphaera hirsuta labyrinthodinium truncatum cerebrocysta irregulare cordosphaeridium minimum impagidinium elongatum and operculodinium centrocarpum s s and the acritarch lavradosphaera elongatum which are confined to the miocene have highest relative abundances and restricted temperature ranges at the warm end of the reconstructed temperature spectrum the latter five species disappear when iceland sea surface temperatures permanently drop below 20 c thus indicating a distinct threshold on their occurrence in contrast species occurring in both the miocene and pliocene interval batiacasphaera micropapillata habibacysta tectata reticulatosphaera actinocoronata cymatiosphaera invaginata show a broader temperature range and a tolerance towards cooler conditions operculodinium eirikianum may have a lower limit on its occurrence at around 10 c the calibration of species relative abundance versus reconstructed sea surface temperature provides a quantitative assessment of temperature ranges for extinct miocene to pliocene species indicating that temperature is a decisive ecological factor for regional extinctions that may explain the frequently observed asynchronous highest occurrences across different ocean basins it demonstrates that qualitative assessments of ecological preferences solely based on paleo biogeographic distribution should be treated with caution in addition to enhancing knowledge on marine palynomorph paleoecology this study ultimately improves the application of palynomorphs for paleoenvironmental reconstructions in the neogene of the arctic and subarctic seas a region essential for understanding past global climate

seismo and neotectonics in finnmark kola and the southern barents sea part 2 seismological analysis and seismotectonics abstract a detailed review and analysis of seismological data acquired since 1979 from finnmark kola and the southern barents sea has provided a much improved delineation of the earthquake activity in that region in the barents sea the seismicity is confined only to the western areas while the finnmark kola coastal areas show some seismicity only north and east of murmansk in the rybachi cape tereberski region further inland there are several clear seismicity lineations that to some extent can be correlated with postglacial faults including the ne sw striking stuoragurra fault in finnmark the spatial correlation between seismicity and mapped faults is interpreted in general as a reflection of broad zones of weakness that respond to the present day stress field a detailed analysis of the earthquakes in this area has also shown a dynamic consistency in that they reveal a reverse faulting pattern that is consistent with a detailed geological study that includes a core drilling the dominant horizontal stress direction in this region is nnw sse consistent with the ridge push effect

low latitude sea surface temperatures for the mid cretaceous and the evolution of planktic foraminifera isotopic data from exceptionally well preserved foraminifera show that the subtropical north atlantic had sea surface temperatures ssts between 30 and 31 c during the late albian and early cenomanian these temperatures were warmer than average modern temperatures in the tropical western atlantic and support previous inferences based on diagenetically suspect material of albian tropical ssts of 30 c this finding is consistent with basic theories of oceanic thermal response in the tropics to the high atmospheric carbon dioxide levels during the middle cretaceous greenhouse however our data do not support the concept of a super tethyan region of hypersaline waters in the western north atlantic during late albian and early cenomanian time because seawater salinities substantially higher than modern ones would require significantly higher ssts than those reported here isotopic analysis of mid cretaceous planktic foraminifera shows that planomalina ticinella and biticinella grew in surface waters and provide isotopic proxies for sst whereas deeper growing species include hedbergella rotalipora and praeglobotruncana none of these taxa display isotopic indications of photosymbiosis suggesting that this ecology did not evolve in planktic foraminifera before the late cretaceous contrary to previous hypotheses none of these species increased their depth habitat during their life cycles unlike many extant planktic foraminifera the rotaliporids may have been preferentially susceptible to extinction during oceanic anoxic events because they lived within or below the thermocline for most of their life cycles

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

warm deep water ocean conveyor during cretaceous time because the deep water is associated with its high latitude sources a warm deep ocean durin gmesozoic cenozoi ctim ei sa challenge ther ei sn ofeasibl ephysica lmechanism that could maintain warm subpolar surface oceans in both hemispheres the goal of this study is to explore a hypothesis that a warm deep ocean can coexist with relatively cool subpolar high latitude sea surface in one hemisphere and a warmer subpolar sea surface in the other a series of numerical ocean circulation experiments confirms that the ocean meridional circulation can keep the abyssal ocean warm despite the northern subpolar surface water staying relatively cool

jiggling the tropical thermostat in the cretaceous hothouse modern open ocean sea surface temperatures rarely exceed 28 29 8c and the same has been thought to represent a rough maximum for past tropical climates however new isotopic estimates from the uppermost cenomanian in the tropical western north atlantic suggest that mixed layer temperatures reached 33 34 8 c 62 8c during the middle cretaceous hothouse uppermost cenomanian tropical sea surface temperatures may have been as much as 4 7 8c warmer than the highest modern mean annual temperatures such extreme conditions suggest that warm tropical oceans could have driven substantially intensified atmospheric heat transport near the cenomanian turonian boundary the tropical thermostat was set higher than today challenging the hypothesis of tropical climate stability

an anoxic event at the albian cenomanian boundary the fish scale marker bed northern alberta canada abstract the fish scale marker bed fsmb of the shaftesbury formation which marks the albian cenomanian boundary is a regional stratigraphic marker in the western interior of canada at the outcrop studied on the smoky river in northwestern alberta three major shale units can be distinguished in the fsmb and contiguous strata the lowermost shale unit 1 is bioturbated and contains high diversity dinoflagellate and moderate diversity foraminiferal assemblages it has dominantly type iii terrestrial organic matter om and low total organic carbon content toc the unit was deposited in an open marine neritic environment of normal salinity the fsmb unit 2 represents a zone of condensed bioclastic accumulation composed of abundant fish remains the dinoflagellate species diversity is drastically reduced in this unit and it lacks benthonic foraminifera and bioturbation unit 2 is characterized by mainly type ii marine om and high toc values unit 2a contains rippled sandstone related to either a shallowing or to deeper water currents a fish hash conglomerate making up unit 2b can alternatively be interpreted as a bioclastic condensed and winnowed deposit or as a transgressive lag unit 2c consists of black platy shale with abundant fish remains and represents a minor marine trangression during the deposition of fsmb when the bottom waters were dominantly anoxic collectively the features of unit 2 suggest deposition under a stratified water column with moderate productivity of planktonic and nektonic organisms in the upper oxygenated layers but with anoxic bottom waters unit 3 overlying the fsmb consists of blocky shale with reduced concentration of fish remains due to increased rate sedimentation during its deposition the organic rich sediment of unit 3 was progressively diluted by clastic material and there was an increase in the dissolved oxygen content of the bottom waters the anoxic event at the fsmb is related to a relative rise in sea level and possibly to the mixing of waters different salinities and temperatures from the arctic ocean and the gulf of mexico in the western interior seaway

petrology of the chilliwack batholith north cascades washington generation of calc alkaline granitoids by melting of mafic lower crust with variable water fugacity calc alkaline granitoid rocks of the oligocene pliocene chilliwack batholith north cascades range from quartz diorites to granites 57 78 sio2 and are coeval with small gabbroic stocks modeling of major element trace element and isotopic data for granitoid and mafic rocks suggests that 1 the granitoids were derived from amphibolitic lower crust having ree rare earth element and sr nd isotopic characteristics of the exposed gabbros 2 lithologic diversity among the granitoids is primarily the result of variable water fugacity during melting the main effect of fh 2 o variation is to change the relative proportions of plagioclase and amphibole in the residuum the ree data for intermediate granitoids quartz diorite granodiorite eu eu 0 84 0 50 are modeled by melting with fh 2 o 1 kbar leaving a plagioclase pyroxene residuum in contrast data for leucocratic granitoids leuco granodiorites and granites eu eu 1 0 0 54 require residual amphibole in the source and are modeled by melting with fh 2 o 2 3 kbar consistent with this model isotopic data for the granitoids show no systematic variation with rock type 87sr 86sri 0 7033 0 7043 end 0 3 3 to 5 5 and overlap significantly with data for the gabbroic rocks 87sr 86sri 0 7034 0 7040 end 0 3 3 to 6 9 the fh 2 o variations during melting may reflect additions of h2o to the lower crust from crystallizing basaltic magmas having a range of h2o contents chillwack gabbros document the existence of such basalts one dimensional conductive heat transfer calculations indicate that underplating of basaltic magmas can provide the heat required for large scale melting of amphibolitic lower crust provided that ambient wallrock temperatures exceed 800 c based on lithologic and geochemical similarities this model may be applicable to other cordilleran batholiths