recent warming in eastern canada inferred from geothermal measurements borehole temperature measurements from several sites in eastern canada were analyzed to determine recent step changes in ground surface temperature inversion of the data suggests a warming by 1 to 2 c in the last 100 years for most of the sites analyzed

continental break up along strike slip fault zones observations from the equatorial atlantic the study focuses on equatorial atlantic margins and draws from seismic well gravimetric and magnetic data combined with thermo mechanical numerical modelling our data and numerical modelling indicates that early drift along strike slip originated margins is frequently characterized by up to 10 20 spreading vector adjustments in combination with the warm thinned crust of the continental margin these adjustments control localized transpression our observations indicate that early drift margin slopes are too steep to hold sedimentary cover which results in their inability to develop a moderately steep slope undergoing cycles of gravitational instability resulting in cyclic gravity gliding these slopes either never develop such conditions or gain them at later development stages our modelling suggests that the continental margin undergoing strike slip controlled break up experiences warming due to thinning along pull apart basin systems pull apart basins eventually develop sea floor spreading ridges margins bounded by strike slip faults located among pull apart basins with these ridges first undergo cooling however spreading ridges leaving the break up trace along its strike eventually pass by these cooling margins warming them again before the final cooling proceeds as a result the structural highs surrounded by several source rock kitchens witness a sequential expulsion onset in different kitchens along the trajectory of spreading ridges

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

climate change in india inferred from geothermal observations 1 temporal variations in surface ground temperature impart a signal to the subsurface thermal regime that is captured in borehole temperature depth profiles seventy temperature depth profiles in india located between 12 and 28 n are analyzed to infer past changes in ground temperature these profiles exhibit predominantly positive anomalous temperatures relative to the background thermal regime beginning at depths of 75 150 m and increasing toward the surface this pattern is consistent with warming over the past century an interpretation in terms of linear surface temperature change indicates warming of about 0 9 0 1 c over the past 150 years relatively complete surface air temperature sat records from meteorological stations near the boreholes indicate similar rates of warming over the last century a combined analysis of borehole temperatures and sat records yields a long term preobservational mean temperature 0 8 0 1 c lower than the 1961 1990 mean sat when the most recent decade is included directly in the analysis the average total warming in india from the early 1800s to the late 1990s is 1 2 c

practicalities of extrapolating one dimensional fault and fracture size frequency distributions to higher dimensional samples previously published theory which extrapolates fault and fracture population statistics observed in a one dimensional sample to two and three dimensional populations is found to be of limited value in practical applications we demonstrate how significant the discrepancies may be and how they arise there are two main sources for the discrepancies 1 deviations from ideal spatial uniformity spatial poisson process of a fault or fracture pattern and 2 non power law scaling of the size frequency distributions of the population we show that even small fluctuations in spatial density combined with variance in the estimator of population statistics can lead to considerable deviations from the theoretical predictions ambiguity about power law scaling or otherwise of the underlying population is a typical characteristic of natural data sets and we demonstrate how this can affect the extrapolation of one dimensional data to higher dimensions in addition we present new theoretical approaches to the problem of extrapolation when clustering of faults and fractures is explicitly considered clustering is commonly observed in the field as en echelon arrays of fault or fracture segments and we show how this property of natural patterns can be quantified and included in the theory these results are relevant to building more realistic three dimensional models of the physical properties of fractured rocks such as fracture permeability and seismic anisotropy

quantifying lake athabasca canada water level during the little ice age highstand from palaeolimnological and geophysical analyses of a transgressive barrier beach complex we combine multiproxy palaeolimnological and geophysical analyses of a barrier beach complex to estimate the water level of a sustained lake athabasca canada highstand during the little ice age lia 1600 1900 ce palaeolimnological analyses on sediment cores from the lagoon behind the barrier indicate high water levels during the lia controlled by subsurface hydrological connection with lake athabasca key features in the lia stratigraphic interval are sand laminations deposited by overwash events and low c n ratios reflecting deposition of predominantly aquatic organic matter ground penetrating radar profiles of the barrier reveal a depositional transgression sequence composed of waterlain landward dipping foreset beds and horizontal topset beds overlain by aeolian deposits stratigraphic relations suggest that the lia washover deposits in the lagoon formed as the barrier was actively translating landward and were generated by high water events on lake athabasca that overtopped the barrier thi

micropaleontological bathymetry of the cretaceous of western morocco abstract micropaleontologic and sedimentologic studies have been carried out on the onshore cretaceous sediments of the agadir and essaouira coastal basins and offshore deep sea cretaceous sediments recovered from dsdp sites 135 137 140 367 and 370 off the coast of northwest africa facies analysis reveals several episodes of transgression and regression in the coastal basins suggesting a local subsidence and interplay between the rates of sedimentation and sea level change the late cretaceous transgression commenced during the late aptian albian and reached a maximum during the early turonian the late cretaceous transgression had two major events of coastal upwelling of cold water masses during the turonian and maastrichtian with the production of cherts radiolarians non keeled planktonic foraminifers and phosphates antarctic current the coniacian to early santonian was regressive whereas the campanian facies keeled planktonic foraminifers recorded a warm cycle of the cretaceous transgression the study has also revealed several specialized assemblages of foraminifers associated with sediment facies of particular ecologic and environmental significance onshore and offshore correlations reveal the evolution of the passive margin which includes a subsidence deep sea circulation variation of the calcite compensation depth ccd a mid cretaceous oceanic hiatus and late cretaceous transgression in the coastal basins these events seem more or less synchronous in nature and depict north atlantic paleogeographic developments through the cretaceous the mid cretaceous events such as deep sea hiatus and oceanic circulation in the north atlantic and their extension in the south atlantic apparently suggest a structural communication in both realms of the atlantic ocean although faunal evidence indicates an earlier surface connection during aptian to albian finally in the light of published data some paleogeographic aspects are reviewed

holocene paleotemperatures deduced from geothermal measurements abstract detailed measurements of temperature and rock thermal properties were carried out in a 1000 m deep borehole drilled in massive granite using a suitable reduction these measurements reveal a coherent variation of apparent heat flow with depth which is attributed to past variations of the ground temperature during the last 10 000 years two inversion techniques of the data are described in order to reconstruct these paleotemperatures a classical inversion method allows a discussion of the information content of the data but leads to unreasonable temperature variations another method using bounds on paleotemperature variations provides more acceptable temperature models the main features of these models are the presence of a cold event identified as the little ice age and of warm episodes around 1500 bc and at the beginning of the present century the amplitude of the inferred variations would be at least 1 09 c

late cretaceous upwelling system along the southern tethys margin israel interrelationship between productivity bottom water environments and organic matter preservation organic rich upper cretaceous sequences in israel were deposited in an extensive highly productive upwelling linked system which prevailed along the southern tethys margin and lasted for 19 m y santonian to late maastrichtian an understanding of the spatial and temporal characteristics of this system was gained through detailed paleontological and geochemical analyses of subsurface sequences in two basins in israel representing an outer shefela and an inner zin facies belt the nature of the upwelling system and its effect on the sedimentary record is related to two basic environmental parameters namely paleoproductivity intensity and oxygen levels at the bottom the assessment of these parameters and their interrelationship has been performed through the development of paleontological foraminiferal criteria which are independent of the organic matter content following the establishment of these criteria it is concluded that the productivity reached its maximum intensity during the late campanian which was also the time of most notable differentiation between the center of the upwelling system in the inner belt and the less intense conditions in the outer basin this distribution is expressed in varied lithology organic rich carbonates phosphorites and siliceous rocks at the core of upwelling and a uniform lithology organic rich carbonates at the margin of this system the uniform lithology of the maastrichtian in both basins composed of organic rich carbonates is ascribed to a gradual weakening of productivity the bottom conditions in the inner belt during the late campanian the time of maximum surface productivity were near anoxic changing to more aerated dysaerobic conditions during the early maastrichtian in the outer belt a more aerated bottom dysaerobic prevailed throughout the late campanian to late maastrichtian the elevated organic matter content in both basins reflects the overall environment of high productivity its actual variations however seem to be unrelated to changes in surface productivity and bottom oxygen levels

ground temperature histories for central and eastern canada from geothermal measurements little ice age signature deep borehole temperature profiles have been analyzed to determine ground temperature histories in central and eastern canada clear signs of a cold period between 1500 and 1800 a d corresponding to the little ice age have been found a warming trend after 1800 a d was detected throughout eastern and central canada temperature profiles from western ontario are consistent and were inverted simultaneously to yield a regional ground temperature history the recent warming appears to be correlated with the increase of atmospheric co2 reported for a greenland ice core

facies and sequence stratigraphy of a late barremian wave dominated deltaic deposit agadir basin morocco abstract the late barremian succession in the agadir basin of the moroccan western high atlas represents wave dominated deltaic deposits the succession is represented by stacked thickening and coarsening upwards parasequences 5 15 m thick formed during fifth or fourth order regression and building a third order highstand systems tract vertical facies transitions in parasequences reflect flooding followed by shoaling of diverse shelf environments ranging from offshore transition interbedded mudstones siltstones and thin sandstones lower shoreface lower delta front hummocky bedforms to upper shoreface upper delta front cross bedded sandstones the regional configuration reflects the progradation of wave dominated deltas over an offshore setting the maximum sea level fall led to the development of a sequence boundary that is an unconformity the subsequent early aptian relative sea level rise contributes to the development of an extensive conglomerate lagged transgressive surface of erosion the latter and the sequence boundary are amalgamated forming a composite surface

ground surface temperatures in canada spatial and temporal variability 1 past changes in the earth s surface energy balance are recorded in the ground as perturbations of the subsurface thermal regime here we reconstruct ground surface temperature histories gsth from temperature versus depth profiles measured at 246 sites distributed across canada we show that the ground has warmed about 0 7 k in the last 100 years spatial variability is significant and indicates that the largest warming is in the southern areas of canada the apparent signal for the little ice age lia does not appear to be homogeneous across canada

comparative study of the lower and mid cretaceous sequences on different maghrebian shelves and basins their place in the evolution of the north african atlantic and neotethysian margins abstract the lower and mid cretaceous sequences known from morocco coastal essaouira agadir safi basin and eastern rif foreland in western algeria da a mountains and finally in southern tunisia chott range and saharian shelf are presented from a biostratigraphic and sedimentologic viewpoint this work shows for the period considered common features in the geodynamic evolution of the different regions such as 1 generalization of the carbonate facies in the early cretaceous berrisian and at the end of the mid cretaceous cenomanian turonian times 2 delineation of important discontinuities in the valanginian and bedoulian times this evolution gives evidence of an undeniable influence of eustatism in this northern part of africa nevertheless detailed differences allow us to distinguish 3 an atlantic type evolution characterized by discontinuities with gaps safi or sudden variations of thickness essaouira agadir at the berriasian valanginian boundary related to the neocimmerian rifting and block faulting phase later on this evolution is underlined by a progressive acceleration of subsidence at the aptian albian boundary due to the removal of the mid oceanic doming 4 a neotethysian type evolution eastern rif foreland western algeria and southern tunisia where local tectonic movements have probably generated the rapid growth of the external marly bedoulian basins and the spreading of the wealdian type valanginian to barremian and utrillas albian terrigenous depositional systems the latest event is linked to the austrian tectonic phase responsible of variable gaps towards the aptian to albian transition

strand plain evidence for late holocene lake level variations in lake michigan lake level is a primary control on shoreline behavior in lake michigan the historical record from lake level gauges is the most accurate source of information on past lake levels but the short duration of the record does not permit the recognition of long term patterns of lake level change longer than a decade or two to extend the record of lake level change the internal architecture and timing of development of five strand plains of late holocene beach ridges along the lake michigan coastline were studied relative lake level curves for each site were constructed by determining the elevation of foreshore swash zone sediments in the beach ridges and by dating basal wetland sediments in the swales between ridges these curves detect long term 30 yr lake level variations and differential isostatic adjustments over the past 4700 yr at a greater resolution than achieved by other studies the average timing of beach ridge development for all sites is between 29 and 38 yr ridge this correspondence occurs in spite of the embayments containing the strand plains being different in size orientation hydrographic regime and available sediment type and caliber if not coincidental all sites responded to a lake level fluctuation of a little more than three decades in duration and a range of 0 5 to 0 6 m most pronounced in the relative lake level curves is a fluctuation of 120 180 yr in duration this 150 yr variation is defined by groups of four to six ridges that show a rise and fall in foreshore elevations of 0 5 to 1 5 m within the group the 150 yr variation can be correlated between sites in the lake michigan basin the 30 and 150 yr fluctuations are superimposed on a long term loss of water to the lake michigan basin and differential rates of isostatic adjustment

late cretaceous biostratigraphy and sea level change in the southwest tarim basin abstract the upper cretaceous sediments of the southwest tarim basin include the remnants of a large epicontinental sea in this study based on the analyses of sedimentation foraminifera ostracods bivalves and other fossils from the simuhana section as well as published biostratigraphy data we present a field based biostratigraphy and review of sea level change for the upper cretaceous strata in the southwest tarim basin the upper cretaceous marine strata include the kukebai and dongba formations relatively abundant foraminifera ostracods and bivalves were discovered and identified based on the biostratigraphy and correlation the proposed age of the lower and middle kukebai formation is cenomanian to earliest turonian the upper kukebai is of turonian to early coniacian age the lower dongba formation is late coniacian to early campanian the middle dongba formation is late campanian to early maastrichtian and the upper dongba formation is late maastrichtian in age possibly extending into the danian the relative sea level began to rise during sedimentation of the lower kukebai formation cenomanian and reached a maximum by the time of the middle to upper part of the upper kukebai formation turonian to early coniacian after a subsequent sea level fall another transgression began during sedimentation of the middle dongba formation above the upper dongba formation the sea level fell dramatically the sea level of the southwest tarim basin shows a close relationship with the global sea level curve and with the sea level of south tibet

sequence stratigraphy and stable isotopes δ13c δ180 of the late cretaceous carbonate ramp of the western margin of the iberian chain soria spain abstract within the upper cretaceous sediments of the western margin of the northern iberian chain several formations of turonian to campanian age form a carbonate platform succession 165 270 m thick developed during a second order cycle of relative sea level rise and fall this succession consists of two depositional sequences deposited during third order cycles formed by sediments deposited in a broad epeiric ramp type platform open to the north the lower depositional sequence moral de homuez formation began during the cenomanian turonian transgression and represents the transgressive systems tract and highstand systems tract it was terminated by a late turonian regression resulting in a type 2 sequence boundary two types of parasequences deepening upward and shallowing upward respectively 1 to 3 m thick deposited within fourth and higher order cycles have been identified with features corresponding to lagoonal deposits the upper depositional sequence comprising the hortezuelos caballar hontoria del pinar burgo de osma and santo domingo de silos formations began during the early coniacian transgression and was terminated by a campanian regression this upper depositional sequence also represents the transgressive systems tract and highstand systems tract eight types of shallowing upward parasequence 1 to 4 m thick locally up to 10 m deposited in subtidal high energy shoals and channels and low energy settings lagoon locally with rudist patch reefs and in tidal flat environments have been identified carbon isotope data showing sharp and correlatable positive anomalies in different sections strongly suggest that oceanic anoxic events are recorded in these shallow platform deposits the cenomanian turonian oceanic anoxic event results in a positive 13c excursion of up to 4 that coincides with the presence of small size low diversity benthic foraminifers agglutinated and planktonic foraminifers and calcispheres despite the paucity or complete absence of black shales the santonian campanian oceanic anoxic event is recorded but is not so evident the relative 13c minimum between these two maxima apparently coincides with the turonian coniacian boundary it is concluded that short term variations in 13c can be useful for correlation in shallow platform areas where the fossil record has little biostratigraphical precision accordingly the ages previously assigned to the sediments studied have been partially modified the oxygen isotope results are more negative than expected for carbonates precipitated in equilibrium with normal marine waters thus indicating diagenetic alteration by meteoric waters

inference of ground surface temperature history from subsurface temperature data interpreting ensembles of borehole logs ground surface temperature histories gsths inferred from borehole temperaturedepth t z data are often degraded to a various extent by random or systematic noise in thet z data and in the measurements of thermophysical properties of the earth to minimize the effects of noise and hence improve the fidelity of the inferred gsth a plausible approach is to perform a simultaneous inversion of thet z logs in a region or alternatively to invert the individualt z logs and then average the resulting gsths averaging and simultaneous inversion are conceptually different whereas an averaging can always be peformed a simultaneous inversion is predicated on the assumption of a common transient component of the gsth in all thet z logs in this work we examine and compare the two approaches using a time domain inverse formulation based on the method of least squares we consider a set of scenarios a multiplet z logs from a single borehole b multiple boreholes from a single site c multiple boreholes in similar climatological settings and d multiple boreholes in different climatological settings we show that for a b and c averaging and simultaneous inversion yield nearly identical results for boreholes in different settings the assumption of a common transient gsth may be invalid and averaging and simultaneous inversion give divergent results

flood hydrology of the peace athabasca delta northern canada this study conducted a systematic examination of the flood hydrology of the peace athabasca delta pad a complex and internationally important freshwater ecosystem located in northwestern canada three distinct zones of floodwater origin within the pad were discerned on the basis of the dominant hydrology and the topography represented by a digital elevation model dem 1 perimeter peace delta 2 perimeter athabasca delta and 3 central delta lakes analysis of the satellite image and dem derived flood maps of historically significant events combined with field data of open water and ice influenced flood stages revealed that ice jamming was the most effective and likely the only mechanism capable of recharging the highly elevated perimeter areas in the athabasca and peace deltas this supports the conclusion of previous studies that used hydrometric data external to the delta to infer inter delta flood conditions by contrast even the record open water flow to the peace delta could not generate overbank flow hydraulic simulation of the naturalized system no dam no weirs suggests that overbanking of the lower peace river would have been a rare occurrence without the effects of regulation both ice jam induced and open water high waters were found to recharge perched basins in the athabasca delta enlargement of the central delta lakes beyond the shoreline was determined to be an effective flood mechanism for filling low to mid elevation wetlands comparison of the observed and naturalized lake levels indicates that flow regulation of the peace river and addition of the weirs on delta outflow channels has depending on the year led to an increase or a reduction in the annual maximum potential of inland flooding via lake expansion copyright 2006 crown in the right of canada published by john wiley sons ltd

vadose zone fluid flow estimates calculated from temperature measurements taken in the southern albuquerque basin at tome new mexico 1 closely spaced temperature measurements taken across the vadose zone at tome new mexico suggest upward and or horizontal fluid flow between 58 and 30 m depth the temperature depth profile is an independent data set that in the present example is best fitted by the exponential expression characterizing vertically upward water flow in addition expressions representing horizontal flow and combined horizontal and vertical flow also provide relatively good fits to the temperature data a unique hydrogeologic environment is present at the tome site where a thick clay layer straddles the water table at 59 m depth neutron and bulk density porosity logs indicate the clay porosity is largely liquid phase water filled it is suggested that matrix potential and perhaps osmosis are able to drive an uncommonly large vertical fluid flow for southwestern u s desert vadose zone sites because the presence of the saturated clay layer straddling the relatively shallow water table provides ideal conditions the vertical specific discharge estimate is 0 09 m yr 1 liquid water horizontal flow may also be possible in the clay layer and is estimated as 23 m yr 1 both the vertical and horizontal flow estimates are not untypical for the saturated zone in the albuquerque basin

ground temperature history in central europe from borehole temperature data summary ground temperature histories gth are inferred from temperature measurements in several boreholes of south eastern germany and western bohemia czech republic the gths that can be extracted from these boreholes ranging in depth between 150 and 700m cover the past 250yr both data sets were inverted separately and yield consistent gths they were also inverted jointly to yield a regional gth of the past 250yr for this part of europe the results indicate two main episodes in the mean ground temperature with 1 a cooling period from 1750 1800 to 1930 1950 followed by 2 short colder and warmer periods until now the same trends are found in the meteorological records at four nearby weather stations bayreuth jena munchen and praha but the meteorological record in berlin is clearly distinct the gth for this part of europe is also markedly different from one obtained in central france these differences are consistent with the spatial variability of climatic trends

a terrestrial scenario for the cretaceous tertiary boundary collapse of the marine pelagic ecosystem in this paper we present an expansion of the model for marine ecosystem collapse at the cretaceous tertiary boundary presented by brinkhuis and zachariasse 1988 a long term sea level drop at the end of the cretaceous culminated in a short term regressive pulse at k t time deep water production was curtailed minimizing the vertical advection of nutrients and oxygen in the oceans consequently a productivity crisis developed which could only be survived by cosmopolitan shallow dwellers and the oxygen minimum zone omz expanded no sustained oceanic anoxic event followed the k t boundary event since productivity had dropped to extremely low values at k t time however the short term expansion of the omz invoked by the combination of minimized oxygen advection and abrupt mass mortality caused dysoxic conditions even to reach up to the shelves as can be deduced from sedimentological chemical and faunistic observations

palaeoecology of foraminiferid assemblages across late cretaceous phosphogenic cycles south west atlas morocco abstract major phosphogenic episodes throughout geological history appear to lie in close proximity to periods of extensive faunal turnover late cretaceous phosphogenic deposits of the southwest atlas morocco comprise part of the great tethyan phosphogenic belt stretching across north africa to the middle east the palaeoenvironmental conditions under which these moroccan deposits formed have been investigated largely through the interpretation of their associated foraminiferid plankton and benthos changes in the composition of foraminiferid assemblages across phosphogenic features suggest a close relationship between phosphogenesis oceanic upwelling and the impingement of cold oxygen depleted waters onto a broad continental shelf environment such a scenario is believed to be followed by high mortality in specialised faunal assemblages and the accumulation of organic material on hard lithified surfaces the erosion and redistribution of hardground and biogenic remanie deposit has been associated with late campanian tectonic disturbances in the atlas mobile belt these events appear to be cyclic occuring throughout the lower maastrichtian of southern morocco

reconstructing absolute water level variability of lake prespa sw balkans during the medieval climate anomaly and little ice age from a prograding beach ridge complex lake prespa beach ridges register climate driven water level fluctuations that contain a strong north atlantic signal this study examines the beach ridge complex that underlies the koula isthmus

ground surface warming history in northern canada inferred from inversions of temperature logs and comparison with other proxy climate reconstructions well temperature logs from 61 sites located in discontinuous and continuous permafrost regions of northern canada are analyzed the method of functional space inversion fsi is applied to the set of precise temperature logs from wells located between 60 and 82 n there is strong evidence of extensive ground surface temperature gst warming beginning in the late 18th century and lasting until the 20th century this was preceded by a lengthy period of cooling the approximate average increase of the surface temperature of canadian arctic based on all individual gst histories is 1 3 c for the last 200 years simultaneous inversion of all well temperature data suggests an even higher warming approximately 2 c there has been no strong south to north gradient in the ground warming magnitude when northern canadian data are compared with eastern and central canadian data south of 60 n which also shows warming close to 2 c in alaska warming of some 2 c has been restricted mainly to the 20th century in general however a high warming magnitude is common for most of canada and alaska for the previous century the averaged gst history gsth for the canadian arctic is calibrated with and compares visually with a variety of recently published regional and hemispheric proxy climate reconstructions these show that gst warming derived from well temperature logs is generally higher than one shown by other proxy mainly tree ring reconstructions

ground surface temperature history in southern canada temperatures at the base of the laurentide ice sheet and during the holocene abstract we use temperature profiles from 7 deep 2000 m boreholes located in southern canada to infer ground surface temperature histories gsth during the last glacial maximum lgm and the holocene visual inspection of the heat flow and of the reduced temperature depth profiles reveals significant regional differences with some sites showing conspicuous signs of post glacial warming and other indicating only very small changes in ground surface temperature these differences are confirmed by the inversions of the temperature profiles the most prominent variations in gst are found at the sudbury ontario sites where the present ground surface temperature is high with the exception of sept iles quebec the other sites only show moderate or no variation in gst for all the sites except possibly sept iles temperatures at the base of the ice sheet during the lgm were at or slightly below the melting point of ice temperatures might have been lower a few degrees below 0 c at sept iles these results are consistent with field observations and model predictions suggesting high velocity basal flows in the ice sheet above the studied regions these new data on basal temperatures will provide better quantitative constraints on glacier flow dynamics the inversions give a chronology for the retreat of the ice sheet comparable to other proxies inversion and direct modeling show that following the ice retreat there was a warm period between 2 and 5 ka with temperatures 1 2 k higher than present the inversion yields a time for this episode 1 2 kyr more recent than that inferred by other proxies for the holocene climate optimum hco

micropalaeontological and geochemical evidence of mid cretaceous dysoxic anoxic palaeoenvironments in the sergipe basin northeastern brazil

east to west retardation in the onset of the recent warming across canada inferred from inversions of temperature logs 1 canadian well temperature logs for 141 sites are analyzed and show evidence of extensive ground surface temperature gst warming beginning in the eighteenth and nineteenth centuries following a lengthy period of cooling the little ice age over most of the past millennium the method of functional space inversion fsi is applied to the complete set of 141 well precise temperature logs from wells located in low conductivity clastic sediments of the western canadian sedimentary basin and higher thermal conductivity crystalline rocks of the canadian shield in central and eastern canada marked regional differences in the onset of recent warming are evident nineteenth century compared to the seventeenth to eighteenth centuries respectively following a prolonged cold period through earlier centuries analysis of spatial patterns of gst history changes across canada based on the individual inversions of temperature logs shows a systematic east to west retardation in the onset of the recent warming yet a higher overall warming magnitude in western canada in the twentieth century

late aptian to maastrichtian foraminiferal biogeography and palaeoceanography of the sergipe basin brazil abstract the oldest marine deposits of the sergipe basin are late aptian in age the foraminifera recovered from these strata reveal a characteristic tethyan affinity such as the assemblages of favusellids other rugose and or non rugose hedbergellids ticinellids globigerinelloidids vaginulinids nodosariids polymorphinids gavelinellids eggerellids textulariids lituolids ammosphaeroidinids haplophragmiieds trochamminids and cyclamminids the microfaunal evidence suggests that this area had at least surface water exchange with low latitude central north atlantic western tethyan biogeographic provinces even possibly at intermediate epi to mesopelagic water depths contribution of microfaunal elements from high latitude northern boreal realm and or southern austral regions is also apparent although of lesser significance s similarity index of simpson about 10 20 the occurrence of deep water planktonic morphotypes biticinella ticinella rotalipora dicarinella marginotruncana throughout the mid cretaceous succession confirms a well developed open connection with low latitude western tethyan regions at intermediate water depths since the mid to late albian low diversity gabonita assemblages occur in the uppermost cenomanian middle turonian onshore deposits of the basin they have a more conspicuous occurrence in the lowermost turonian strata similar assemblages have been reported from the cenomanian turonian of gabon and upper cenomanian lower turonian outcrops of morocco and israel west african endemic species of gabonita have not been found in the coniacian maastrichtian of sergipe however on the whole the high diversity foraminiferal microfauna bears striking affinities s about 80 95 with those reported from the gulf coast caribbean and guinean provinces attesting to similar palaeoceanographic conditions at low latitudes on both sides of the atlantic during that time interval the biogeographic distribution of late cretaceous slope assemblages of calcareous and agglutinated benthonic foraminifera was pandemic

simultaneous inversion of borehole temperature data for determination of ground surface temperature history summary recent variations of the ground surface temperature recorded in the earth s subsurface can be inverted from borehole temperature data the resolution of the inversion of borehole temperature logs is poor even when the noise level is low this report concerns the potential improvement in the resolution of ground surface temperature history when temperature logs from several boreholes are inverted simultaneously for an inversion algorithm based on singular value decomposition the singular values obtained for simultaneous inversion of several boreholes do not decrease as rapidly as the singular values for a single borehole with the same value of the cut off or of the damping parameter more eigenvectors remain in the solution and give higher resolution for several boreholes than for one tests conducted with synthetic data for 15 boreholes show that the improvement in resolution is real but not spectacular these tests indicate that borehole temperature logs should have approximately the same sampling interval temperature profiles over different depth ranges can be inverted if the reference heat flows and ground temperatures are included in the parameters determined by the inversion tests also show that no consistent ground temperature history gth is obtained when inverting data from boreholes that have experienced different surfacetemperature variations simultaneous inversion can be applied to 1 obtain a local gth for a single site with several boreholes having identical surface conditions or 2 obtain regional averages with data from different sites that have experienced the same variations in ground temperature temperature profiles measured in four boreholes near belleterre in eastern canada appear to have recorded the same perturbation inversion of the temperature data from individual boreholes yields similar but not identical gths the gth obtained by simultaneous inversion of these four boreholes indicates a cool period with minimum temperatures at ca 1800 ad followed by warming above the reference level it is consistent with other analyses indicating recent warming in eastern canada

heat flow in the trans hudson orogen of the canadian shield implications for proterozoic continental growth fourteen new heat flow and radiogenic heat production measurements have been obtained in the paleo proterozoic trans hudson orogen of the canadian shield this orogen which consists of several distinctive belts corresponds to a pulse of crustal growth through island arc magmatism between 1 9 and 1 8 ga the data now available include 17 previously published measurements heat flow variations that are related to the history of magmatism and internal differentiation of the belts provide constraints on the crustal assemblages in the different belts of the orogen the average and standard deviation of heat flow values for the entire orogen 425 11 mw m 2 are identical to those of the older superior province and of the younger grenville province for the orogen as a whole heat flow is weakly correlated to the heat production of surface rocks high heat flow values are found in the thompson belt consisting of metasedimentary rocks deposited on the ancient continental margin of the superior craton there the accumulation of sediments derived from older and differentiated continental upper crust has resulted in significant concentrations of rdioelements in large volumes of rocks the heat flow is low in the belts that expose juvenile proterozoic crust consisting mostly of arc related volcanic rocks in the flin flon snow lake belt the average heat flow is the same as the average of the orogen the low heat production and the lack of correlation between heat flow and heat production suggest that the supracrustal volcanics exposed a t the surface are thin and rest on a basement richer in radioelements in the lynn lake belt the heat flow is significantly lower than the average for the orogen although the surface heat production is not low the heat flow data require a thin 10 kin surface layer overlying the mid and lower crust depleted in ra dioelements around the town of lynn lake heat flow is consistently low over a distance of m40 kin the coincidence between this cold spot and anomalously thick crust suggests that deep crustal roots may be preserved because of the stronger rheology implied by the low temperatures the evolution of the trans hudson orogen exemplifies the interplay between the processes generating rocks of evolved composition which require crustal thickening and those forming normal continental crust with average thickness which require crustal flow and soft crustal rheology

bedform and stratification characteristics of some modern small scale washover sand bodies washover sand bodies commonly develop along microtidal coastlines in beach barrier island or spit settings wave runup usually in conjunction with an abnormally high water level may overtop the most landward berm of the beach and the foredune crest if one exists to produce overwash and subsequent runoff across the more landward subaerial surface two main elements of the resulting deposit are the washover fan and runoff channel newly formed small scale washover deposits were examined along the outer banks north carolina near pt mugu california and at presque isle lake erie pennsylvania the fans were formed in response to unidirectional landward transport and the runoff channels in response to unidirectional flow usually in a landward direction but sometimes in shore parallel then seaward direction where overwash carried across the fan surface and entered a pond or lagoon a small scale delta microdelta developed in this case the washover fan consisted of two subfacies the wetted but subaerial part of the fan and the subaqueous washover delta flow associated with the development of the fan and runoff channel produced distinctive sets of bedforms and internal stratification high velocity discontinuous surges moving across the fan surface resulted in the development of a plane bed and subhorizontal to low angle landward dipping planar stratification which comprised the major part of the fan similarly rhomboid forms were produced by high velocity sheet flow across the fan surface where flow carried into a standing body of water delta type foreset strata developed for this case the lateral structural sequence was subhorizontal planar stratification merging landward into landward dipping delta tabular foreset strata in the runoff setting where flow became channelized and continuous both upper flow and lower flow regime currents were typical upper flow regime bedforms included antidunes standing waves and plane beds the most commonly observed lower flow regime bedforms included microdelta like bars low amplitude bars linguoid ripples and sinuous crested current ripple trains the sets of sedimentary structures comprising modern washover sand bodies provide criteria for the identification of similar deposits in ancient sediments and for more specific interpretation of the environment

a cretaceous and jurassic geochronology an integrated geomagnetic polarity and geologic time scale for the jurassic and cretaceous periods is presented based on various methods according to the availability of definitive isotopic ages an age calibrated sea floor spreading model is used to interpolate the ages of the kimmeridgian to barremian and the campanian to maestrichtian stages numerical age estimates for the aptian to santonian stage boundaries follow published isotopic age determinations the hypothesis of equal duration of ammonite zones is employed as a vernier to apportion time for the hettangian to oxfordian stages the new scale results in ages of 208 ma for the base of the jurassic 144 ma for the jurassic cretaceous boundary and 66 5 ma for the top of the cretaceous the integrated biostratigraphic magnetostratigraphic and geochronometric record serves as a working hypothesis for geologic correlation of jurassic and cretaceous strata

orbital scale record of the late cenomanian turonian oceanic anoxic event oae 2 in the tarfaya basin morocco high sedimentation rates up to 12 cm kyear of laminated organic carbon rich biogenic limestones in the tarfaya basin provide an unusually high millennial resolution record of the late cenomanian oceanic anoxic event oae 2 the global positive carbon isotope excursion across the cenomanian turonian corresponds to 11 light dark sedimentary cycles we interpret these cycles as a response to orbital obliquity variation and estimate the duration of the complete excursion as 440 kyear or one long eccentricity cycle on this time scale the main increase in delta 13 c values occurred over a short time interval of less than 20 kyear in the late cenomanian and reached a first maximum approximately 15 kyear prior to the bulk mainly coccoliths delta 18 o derived sea surface maximum temperature that occurs coeval to the extinction of rotalipora cushmani organic carbon accumulation rates follow obliquity cycles reaching a maximum approximately 10 kyear after the last occurrence of r cushmani then slowly decreasing during the early turonian thus the maximum temperature and the maximum organic carbon accumulation in the tarfaya basin lagged by at least 15 kyear behind the global carbon isotope shift and a proposed reduction of atmospheric co 2 content the climate change across the cenomanian turonian boundary probably occurred independent of co 2 levels and may have been controlled by different greenhouse gases water vapour and methane and changes in ocean circulation i e opening of the equatorial atlantic gateway

possible ambiguities in subsurface temperature logs consideration of ground water flow and ground surface temperature change subsurface temperature regimes can commonly be influenced by both ground water flow in the saturated zone and ground surface temperature change both phenomena are widespread and one or the other may be unnoticed and or unanticipated in various temperature logs as a consequence it is often difficult to determine the relative impact of the two phenomena on the temperature depth data at a site a number of models for ground water flow ground surface temperature change and a combination of the two processes are fitted to two example temperature logs showing characteristic nonlinearity examples of the possible impact of one phenomenon on the parameters calculated for the other phenomenon demonstrate the potential interactive influence the analysis can be used to estimate potential uncertainties in calculations of ground water flow and ground surface temperature change from subsurface temperature data and therefore how interpretations of ground water flow and ground surface warming might be affected from the analysis presented the relative importance of the two phenomena may be further considered at different locations

latest cenomanian earliest turonian low oxygen tolerant benthonic foraminifera a case study from the sergipe basin n e brazil and the western anglo paris basin southern england abstract distinctive sedimentological geochemical isotopic and micropalaeontological response characterise the nature of sediments deposited under hypoxic anoxic bottom conditions during the latest cenomanian to earliest turonian of most of the world s basins the composition of the biota is a direct response to overall environmental conditions the recognition of distribution patterns of low oxygen tolerant microfauna is therefore of primary importance in evaluating and reconstructing the regional palaeoceanographic settings where such events took place a case study is presented from two coeval stratigraphic sequences the sergipe basin northeastern brazil and the western anglo paris basin southern england the associated benthonic foraminiferal assemblages from oxygen depleted environments consist mostly of opportunistic r selected species basic patterns in community trophic structures appear to have primarily dictated the composition of the biota the assemblages from outer shelf to upper slope oxygen depleted environments are commonly characterised by 1 low diversity 2 limited intraspecific variation 3 predominance c 40 60 of the total foraminiferal assemblage of epifaunal deposit feeding plano concavo convex trochospiral calcareous hyaline morphotypes gavelinellids conorboidids rosalinids and bagginids 4 variable numbers c 10 30 of infaunal bacterial detrital scavengers tapered and elongate morphotypes turrilinids bolivinids buliminellids fursenkoinids polymorphinids and caucasinids 5 epifaunal shallow infaunal deposit feeding lenticular morphotypes coiled vaginulinids c 5 19 6 variable numbers c 10 30 of agglutinated specimens lituolids discamminids eggerellids textulariids trochamminids ammodiscids tritaxiids and valvulinids and 7 dominance about 60 80 of minute c 100 200 m in maximum diameter width or length calcareous hyaline taxa during widespread dysaerobic quasi anaerobic episodes highly oxygen depleted bottom conditions are marked by the absence of benthonic microfauna minor taxonomic differences between the two studied areas are mostly due to palaeobiogeographic provincialism

mid cretaceous of the gibraltar arch area mid cretaceous depositional environments of the gibraltar arch and adjacent areas exhibit at the cenomanian turonian boundary a special type of organic carbon rich siliceous sedimentation which is intercalated in all the different environments from the shelf down to the deep of this area this will be called the cenomanian turonian boundary event ctbe summarizing the most important features of the ctbe it can be pointed out 1 the initiation of the ctbe is nearly coeval 2 very high tocs especially at the base of turonian 3 kerogen is exclusively of type i ii in the undiluted strata 4 independent of given palaeogeographic setting e g e and w margin of the atlantic ocean 5 bituminous sedimentation is also very pronounced in environments with high detrital input and strong dilution e g deep sea fans here too most strata comprise kerogen of type ii 6 as far as we know there is a striking co occurrence of these sediments with strong enrichment in biogenic silica from diagenetically altered radiolaria but there is no link between good preservation of radiolaria and bituminous sediments e g scaglia facies 7 rich radiolarian faunas are common in the carbon rich and carbon free sediments of shallow marine and deep sea environments 8 the important change in the evolution of planktonic organisms foraminifera radiolaria which marks the cenomanian turonian boundary coincides with the peak of anoxic conditions and biogenic silica rich sedimentation all these features of the ctbe observed in the gibraltar arch area are comparable with coeval dsdp facies in the north atlantic and allow on shore off shore tracing of the ctbe 1986 the geological society

recent warming in northwestern ontario inferred from borehole temperature profiles 1 we have used the temperature depth profiles available in the region north and northwest of lake superior in ontario canada to reconstruct the changes in ground surface temperature over the past 500 years the 49 temperature depth profiles used were obtained for heat flow measurements and are part of two different data sets one collected around 1980 the other one after 2000 we have discarded 16 of these profiles because of known nonclimatic perturbations lakes topography clear signs of groundwater circulation we have inverted the remaining 33 profiles to infer the variations in ground surface temperature individual and joint inversions consistently show a recent 150 200 years warming 1 2 k of the ground surface this warming trend is similar to that inferred for northern manitoba and saskatchewan to the northwest and in eastern ontario and quebec to the southeast however there is no clear indication that a cold episode preceded the warming of the past 200 years in northwestern ontario the mean increase in ground surface temperature for all boreholes measured between 2000 and 2003 is 1 3 0 8 k compared to 0 8 0 6 k for the 1980 data this difference suggests that the warming trend is persisting and might even have accelerated recently although the long term trend is climatic part of the recent warming may be due to deforestation by the logging industry

palaeogeography of africa during the cretaceous period abstract a first attempt is made to synchronize the major palaeogeographical events of the african cretaceous where recognizable palaeoclimatological interpretations are given an overview of the nature of the continental margins and the plate tectonic setting for africa during the cretaceous provides a convenient backdrop for presenting the palaeogeographical development of the continent lacustrine deposits occur along the line of south atlantic rifting late jurassic oceanic crust in the south atlantic dates from the valanginian with continental volcanism adjacent to the walvis ridge continuing until the albian locally there was a barremian incursion in southeast africa the falkland plateau and walvis ridge areas created shallow water barriers in the aptian which facilitated the massive accumulation of salt tectono eustatic transgressions took place in the middle to late albian cenomano turonian late turonian to coniacian and campano maastrichtian anoxic conditions prevailed during the late jurassic agulhas bank falkland plateau aptian albian the cenomanian turonian and the coniacian these are relatable to the epicontinental transgressional maxima and the heavy influx of organic debris however there was no campano maastrichtian anoxic event

comment on ground surface temperature history in central canada inferred from 10 selected borehole temperature profiles by laurent guillou frottier jean claude mareschal and julien musset

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

effects of subsurface heterogeneity on the inference of climate change from borehole temperature data model studies and field examples from canada all existing approaches to the analysis and interpretation of borehole temperatures in terms of a ground surface temperature history are based on the one dimensional theory of heat conduction deviations from this idealization are manifest as noise in the interpretation we present numerical experiments that explore the effects of three dimensional subsurface heterogeneity on ground surface temperature histories inferred from borehole temperature profiles inversions of steady state temperature profiles containing such three dimensional noise reveal that in an inversion formulation incorporating a priori information spurious temperature histories can emerge when the a priori constraints on subsurface temperatures and thermophysical properties are too tight i e when arbitrarily small variations in subsurface temperatures and thermophysical properties are interpreted to have significance for the derived climate history relaxation of the a priori constraints enables an effective muting of the spurious histories similar experiments conducted on synthetic transient signals confirm the steady state results but also reveal that relaxation of the a priori constraints will also lead to a loss of signal if the level of relaxation is excessive our experiments suggest that relaxation of constraints on thermal conductivity is more efficient than relaxation of borehole temperatures in suppressing artifacts arising from the three dimensional effects we identify a range of constraints in which reasonable noise suppression and signal recovery are both achieved and then reprocess data from 22 canadian boreholes for which surface temperature histories had earlier been derived by ourselves and others our reprocessed results reveal a remarkably simple surface temperature history common to much of eastern canada this history comprises a recent warming interval commencing in the nineteenth century in which the surface temperature increased by some 1 4 c approximately 0 5 1 0 c of this increase was a recovery from a preceding cooler interval in which the temperature was below the long term mean the remainder of the increase represents warming that exceeds the long term mean

estimation of ground surface temperatures from borehole temperature data to infer past climatic changes from temperatures measured in boreholes one must obtain reliable estimates of ground surface temperature gst histories from these data this paper presents a method that uses a bayesian inverse technique to estimate the gst in the fourier frequency domain by assuming the a priori gst to be stationary with a prescribed standard deviation and a cutoff period the time series is constrained to be bounded and smooth because accounting for conductivity variations with depth is crucial to the estimation of gst a layered earth medium has been used for which the forward analytical solution of one dimensional heat conduction is available borehole data from flin flon and lac dufault in canada are inverted with this method the flin flon hole logged to a depth of 2900 m provides an opportunity to study long term gst variations and the estimated gst from this hole shows some effects of deglaciation at the end of pleistocene at lac dufault similar gsts were obtained independently from three holes ranging from 550 to 900 m and hence the results are considered more reliable in the lac dufault gsts there is a warm period centered about 1000 years bp and a cold period about 400 years b p confirming the presence of the little climatic optimum and the little ice age respectively the flin flon result does not show the little climatic optimum and the little ice age occurs about 100 200 years earlier however in both locations the gsts show another brief cold period around the turn of the century followed by rapid warming until 1940 1950 in good agreement with the trend of northern hemisphere surface air temperatures

late cretaceous anoxic events in the brazilian continental margin abstract a combined geochemical and micropalaeontological study of cenomanian to maastrichtian pelitic sediments from the brazilian continental margin has been undertaken the organic carbon contents rock eval pyrolysis results and biological marker distributions together with the taxonomic selection and distribution patterns of microfossil assemblages indicate that intermittent anoxic events occurred in the brazilian marginal basins during the cenomanian santonian with deposition taking place in progressively deeper waters from neritic to bathyal such events are characterised by the following 1 i a predominance among the benthonic foraminifera of low diversity small sized specimens mainly composed of gavelinellids buliminids and nodosariids indicating dysaerobic bottom conditions 2 ii levels with virtually no benthonic foraminifera and a well developed planktonic biota foraminifera radiolarians and diatoms indicating anaerobic bottom conditions with oxygenated surface waters 3 iii the occurrence of organic rich calcareous mudstone sediments 4 iv features in the biological marker distributions such as high concentrations of 28 30 bisnorhopane and 25 28 30 trisnorhopane up to 130 ppm a predominance of phytane over pristane and medium to high concentrations of nickel and vanadyl porphyrins up to ca 5700 ppm the widely recognized cenomanian turonian and santonian oceanic anoxic events schlanger and jenkyns 1976 ryan and cita 1977 and jenkyns 1980 are therefore manifest in the cassipore ceara sergipe alagoas and campos basins within the brazilian continental margin as is the presence of such events in the coniacian in contrast the campanian maastrichtian appears to be a time interval when deposition under oxygenated conditions produced sediments with low organic carbon contents and poor hydrocarbon source potential containing highly diversified and abundant calcareous and agglutinated benthonic foraminifera

ground surface temperature history in central canada inferred from 10 selected borehole temperature profiles among the 57 temperature depth profiles recently measured in manitoba and saskatchewan canada only 10 are suitable for inferring recent changes in ground surface temperature many of the rejected temperature profiles show an apparent climatic signal but are affected by topography changes in vegetation or the proximity of lakes at the northernmost site near lynn lake manitoba shallow horizontal variations in temperature have been identified that are related to intermittent permafrost such variations can induce an apparent climatic perturbation in areas where lateral thermal conductivity contrasts have been measured heat refraction effects can also incorrectly be interpreted as ground surface temperature histories the analysis suggests that forest fires that occurred at some of the sites have had little influence on the temperature profiles the 10 selected temperature profiles cover a wide area in northern manitoba and saskatchewan they have been independently and jointly inverted by a singular value decomposition method the ground surface temperature history shows two main episodes a cold period tentatively identified as little ice age with a minimum around 1820 a d was followed by marked warming after 1920 these trends are similar to those recognized in eastern canada

a paleoslope model of campanian to lower maestrichtian foraminifera in the north american basin and adjacent continental margin campanian to early maestrichtian benthic foraminiferal assemblages of the new jersey and delaware coastal plain and the baltimore canyon trough contain distinct bathymetric biofacies each occurring in adjacent settings to one another in a profile downdip toward the north american basin the assemblages are interpreted as representing inner shelf to uppermost middle bathyal environments of deposition 10 to 500 m water depth a unique biofacies which consists of predominantly arenaceous foraminifera in a lithology of dark lignitic shales is present in restricted intervals within the baltimore canyon region this biofacies probably developed under oxygen deficient conditions in middle shelf to upper bathyal paleodepths within the north american basin benthic foraminifers from campanian to lower maestrichtian sections at various dsdp sites indicate that deposition took place in middle bathyal to abyssal environments 500 m to more than 3000 m paleodepth a complete paleoslope profile shelf to abyssal is identified within the north american basin and adjacent continental margin the foraminiferal composition of this paleoslope is as follows gavelinella nelsoni g pinguis lenticulina pseudosecans cibicides harperi andpullenia americana characterize shore face to inner shelf regions of 10 to 50 m water depth species that show maximum development in middle shelf environments 50 to 100 m water depth includeclavulina trilatera hoeglundina supracretacea and nodosariids in the outer shelf 100 200 m water depth praebulimina carseyae gavelinella compressa g spissocostata coryphostoma plaitum andpullenia jarvisi predominate the upper bathyal environment of 200 500 m water depth is characterized by species such asarenobulimina subspherica dorothia oxycona verneuilina dickinsonensis n sp stensioina exculpta gracilis andgyroidinoides globosus pullenia cretacea gavelinella ammonoides g whitei g intermedia praebulimina reussi p cushmani pleurostomella subnodosa andstilostomella pseudoscripta are species common to the middle bathyal environment of 500 to 1500 m water depth species that characterize lower bathyal environments 1500 to 2500 m water depth includearagonia velascoensis reussella szajnochae osangularia utaturensis clavulina gabonica tritaxia aspera andspiroplectammina dentata many of the middle and lower bathyal indicator species extend into the abyssal realm 2500 m water depth where they are associated with more abundant species such asaragonia ouezzanensis reussella pseudospinulosa hyperammina elongata rhizammina indivisa andsaccammina complanata the resulting paleoslope model allows a more critical evaluation of the role played by benthic foraminiferal species in shelf slope and abyssal environments it also enhances the accuracy of estimating paleobathymetry especially in shelf regions of the campanian to early maestrichtian

heat flow density values and paleoclimate determined from stochastic inversion of four temperature depth profiles from the superior province of the canadian shield abstract it has long been recognized that terrestrial heat flow density observations from boreholes may be biased due to non steady surface temperature conditions this calls for paleoclimatic corrections which have conventionally been obtained by solving a forward problem based on the equation of heat conduction and models of the surface temperature history and the thermal properties structure while computationally convenient the forward method fails 1 1 to provide a stringent quantitative representation of all available data with confidence limits 2 2 to extract all available information in an optimum manner 3 3 to provide confidence limits on the parameters of interest a stochastic inverse method which overcomes these shortcomings is described the method treats the surface temperature history the thermal conductivity structure and the background heat flow as unknowns which have been constrained a priori with soft bounds the bounds ensure numerical stability and prevent unrealistic solutions when the a priori hypothesis is safe the technique is applied to geothermal data from four 600 m deep boreholes in the superior province of the canadian shield the examples show how it is possible to constrain simultaneously the recent surface temperature history and the steady state background heat flow from shallow geothermal data and furthermore show how uncertainty about the average ground temperature during the wisconsin glaciation may be taken into account

ground temperature histories in eastern and central canada from geothermal measurements evidence of climatic change abstract inverse and direct methods have been used to analyze a large number of borehole temperature logs in order to infer past climatic changes results indicate a warming of 1 2 c in eastern and central canada during the past 150 years a period of cooling between 500 and 200 years before present corresponding to the time of the little ice age has also been identified in the same areas a regional ground temperature history is estimated for eastern and central canada from the simultaneous inversion of several temperature logs the inferred temperature changes appear correlated with the concentration of atmospheric carbon dioxide as reported from a greenland ice core and agree with existing meteorological and dendrochronological records for the area