improving climatic signal representation in tropical ice cores a case study from the quelccaya ice cap peru 1 the published ice core records for quelccaya peru are shown to contain numerous errors in annual layer determination introduced by the subjective methodology of the original analysis a new methodology is presented that aligns and then merges d18o sample measurement profiles from the two quelccaya cores absolute dating of the stratigraphy is established by comparison of prominent dust anomalies with documented earthquake reference marker events the results demonstrate that the original sample measurements can register a comprehensive millennial climate history at sub annual resolution thus also offering great potential for clearer interpretations of enso signals in tropical andean ice cores

what can we learn about crustal structure from thermal data thermal data represent a valuable remote sensing aid in studying crustal evolution heat flow q results from the heat loss by the cooling earth and from the heat production a of the radiogenic elements brought to the upper crust by magmatic intrusives heat flow is often observed to be linearly related to heat production the slope of this relation or thermal depth d has been used to infer a global upward enrichment in heat producing elements this thermal depth has been equated with the thickness of granites but such an interpretation has not been confirmed everywhere the depth to which granitic plutons are rooted can be computed from the inversion of gravity data it averages 7 2 km and is much smaller than the thermal depth granulite facies rocks are assumed to be present in the lower crust on the basis of seismic and geochemical data these rocks are generally depleted or initially poor in radiogenic elements u th k it is suggested that the thermal depth reflects the depth to the depleted layer in continental regions and that it corresponds to the granulitic layer in most places worldwide thermal and seismic data support this relationship although surface heterogeneities introduce complications thermal data can therefore be used to constrain the structure of the crust and its evolution through time

solar radiation maintained glacier recession on kilimanjaro drawn from combined ice radiation geometry modeling 1 in the context of investigating modern glacier recession on kilimanjaro which began around 1880 this study addresses the glacier regime of the vertical ice walls that typically form the margins of kilimanjaro s summit glaciers these walls have suffered a continuous lateral retreat during the twentieth century to evaluate the role of solar radiation in maintaining glacier recession on kilimanjaro a radiation model is applied to an idealized representation of the 1880 ice cap the combined process based model calculates the spatial extent and geometry of the ice cap for various points in time after 1880 support for input data and fundamental assumptions are provided by an automatic weather station that has operated on the summit s northern icefield since february 2000 even in a simple climatic scenario only forced with an annual cycle of clouds the basic evolution in spatial distribution of ice bodies on the summit is modeled well the northern and southern icefields form in characteristic east west orientation which verifies the basic idea behind the model forcing the model with further climate related phenomena improves the results it then additionally reproduces the eastern icefield the third big ice entity on the summit this study qualitatively demonstrates that solar radiation is the main climatic parameter maintaining modern glacier recession on kilimanjaro summit but also suggests that retreat on the inner ice cap margin might have been supported by a secondary energy source the need for additional field measurements is emphasized in order to better understand the complex processes of glacier climate interaction on kilimanjaro index terms 1620 global change climate dynamics 3309 1827 hydrology glaciology 1863 3309 meteorology and atmospheric dynamics climatology 1620 3359 meteorology and atmospheric dynamics radiative processes 9305 information related to geographic region africa keywords tropical glaciers kilimanjaro climate change glacier retreat solar radiation modeling

a time constant for hemispheric glacier mass balance the notion is developed of a mass balance time constant applicable to the northern hemispheric glacier inventory taken as a whole ice dynamics are incorporated only implicitly in its estimation which follows directly from a consideration of observed mass balance and hemispheric temperature time series while such a parameter must certainly be related to the rate at which glacier hypsometry adjusts to variations in climate as are time constants derived via dynamic considerations the parameter discussed herein differs with respect to its statistical character for an ensemble of northern hemisphere glaciers a time constant value on the order of a century is estimated it is shown that such a value is consistent with the hemispheric near equilibration of glaciers that prevailed around 1970 a reference climate is defined such that the mass balance in a given year is a function only of the difference between that year s climate and the reference this difference was small during the hemispheric near equilibrium that prevailed around 1970 implying that the glacier wastage of the late 20th century is essentially a response to post 1970 warming it is shown that precipitation fluctuations play a compensating role in the hemispheric net mass budget in that they are strongly anticorrelated with fluctuations in temperature induced melting however the contribution of precipitation does not override that of temperature which remains the dominant influence on hemisphere wide glacier fluctuations

shear wave processing of sonic log waveforms in a limestone reservoir sonic full waveforms were recorded in a shale limestone interval with an experimental 12 channel acoustic logging device well defined shear pseudo rayleigh waves were observed throughout most of the 142 m interval and were used to distinguish lithologic boundaries and zones of fracturing as interpreted by logs the high signal to noise ratio of the waveforms permitted meaningful shear velocities to be obtained by intervals in this well a correlation of changes in the vp vs ratio with depth aided in identifying some compositional changes in the well but such a correlation could not be used to distinguish fracturing in the limestone shear wave amplitudes however were effective for identifying lithologic changes as well as fractures from the sonic log shear amplitudes were lower in the shale than in the limestone and shear wave attenuation increased in fractured zones there was no strong correlation between the degree of fracturing and the attenuation of stoneley waves in general shear wave pr

heat flow provinces reconsidered abstract the concept of a heat flow province an area in which there is apparently a linear relationship between near surface heat flow and radiogenic heat generation is considered the relationship has been suggested for a wide variety of tectonic terrains ranging in age from archaean to cenozoic it is expressed as q q 0 a 0 d in which q and a o are the measured heat flow and heat generation and q o and d are interpreted to be the uniform reduced heat flow from the mantle and lower crust and d is a scale depth for the distribution of radiogenic elements reported values for d are in a remarkably narrow range and are typically 10 km however there can be substantial uncertainties associated with the data in particular heat generation measurements from a limited number of sites may not adequately represent even a relatively uniform pluton when the data are re analysed with reasonable estimates of uncertainty associated with them the calculated values of q o and d are in most cases significantly different from those calculated without regard to uncertainties in the data only the data from the sierra nevada batholith a deep seated plutonic complex appear to satisfy the relationship even when their uncertainties are taken into account with the re analysis d generally falls in the approximate range 10 20 km this is also the range of depths to a commonly observed discontinuity in the mid to lower crust sometimes called the conrad discontinuity which suggests a possible correlation between the two a model in which blocks of crust 10 20 km thick depths being randomly arranged are each assigned a uniform heat generation randomly generated from a reasonable range produces an apparent relationship between heat flow and heat generation that is at least as good as most of those deduced from real data the model produces crustal temperatures that are generally considerably lower in the lower crust than those commonly calculated this is consistent with the observations from seismic refraction that the depth to the moho can vary widely even in stable shield environments it is concluded that the concept of a heat flow province as originally expounded is invalid

the variation of heat generation density and seismic velocity with rock type in the continental lithosphere abstract the petrophysical properties radioactive heat generation compressional wave velocity and density are related to rock type in crystalline rocks the cation fraction in the rock forming minerals is applied to determine the relationships quantitatively heat generation exhibits considerable variation with rock type as well as with the geologic age of the rocks therefore the relation between heat generation and rock type has been split into a relation for phanerozoic rocks and another for precambrian rocks which exhibit significantly lower heat generation only 1 3 of that of phanerozoic rocks the interrelations between the petrophysical properties are applied to fennoscandia precambrian terrane and southern bavaria northern alpine foreland phanerozoic rocks to estimate the heat generation by radioactivity in the crust and the heat flow density from the upper mantle

experiment on estimating thermal conductivity of sedimentary rocks from oil well logging geologic note oil well are an important source of geothermal data for studying regional tectonics reconstructing the evolution of sedimentary basins and theorizing petroleum generation migration and accumulation a more satisfactory less laborious method of estimating the thermal conductivity of sedimentary rocks is badly needed the thermal conductivity of cores from two gas wells in france was measured and correlated with neutron porosity index sonic interval travel time bulk density and gamma ray logs to obtain reasonable predictions of conductivity data were segregated into lithologic groups such as sand shale carbonate shale and carbonate sand a set of regression coefficients in the equation that predicts the conductivity from the logs was calculated for each group t e correlation coefficients between the measured and predicted conductivities of the core samples were 0 81 0 75 and 0 61 respectively for the three lithologic groups the average percent difference between the measured and the calculated conductivities for the lithologies likely to be encountered in practice is 13 4 we expect this figure can be reduced to 10 by enlarging the data base for calculating the regression coefficients in the same basin or oil field the relative errors from well to well probably will be 6 or smaller because the lithology will be nearly homogeneous

out of tune the dangers of aligning proxy archives abstract tuning is a widespread technique to combine date and interpret multiple fossil proxy archives through aligning supposedly synchronous events between the archives the approach will be reviewed by discussing a number of literature examples ranging from peat and tephra layers to orbital tuning and 18o series from marine and ice deposits potential problems will be highlighted such as the dangers of circular reasoning and unrecognised chronological uncertainties and some solutions suggested fossil proxy research could become enhanced if tuning were approached in a more quantitative reliable and objective way and especially if individual proxy archives were non tuned and kept on independent time scales

glacier recession on kilimanjaro east africa 1912 89 the varying ice extent on the kibo cone of kilimanjaro east africa this century was reconstructed from terrestrial photogrammetric mappings in 1912 and 1953 and satellite images in 1976 and 1989 these were all conformed to the official 1 50 000 topographic sheet the ice distribution on kibo is characterized by lower ice margins on the southern than on the northern flanks and deepest reaching glaciers to the west contrasting with least ice cover on the eastern crater rim the meridional contrast appears to be related to the more abundant precipitation on the southern side the even more striking zonal asymmetry in ice cover is favored by the vigorous diurnal circulations with enhanced afternoon cloudiness blocking insolation on the western slopes the total ice cover diminished from 12 058 to 6675 to 4171 to 3305 x 10 3 m 2 between the years 1912 1953 1976 and 1989 and the three large coherent ice bodies disintegrated into numerous smaller ice fragments

the measurement of thermal conductivity of solids with a transient linear heat source on the plane surface of a poorly conducting body abstract during the last ten years the transient hot wire method for measuring thermal conductivity of ocean bottom muds and other soft materials has been adapted for measuring the conductivity of solid rocks because it is cheaper and quicker than the steady state methods such as the divided bar this is done by embedding the hot wire in the form of a hypodermic needle or a ribbon flush into the surface of a block of a poorly conducting material when a flat surface of a specimen is placed on the surface of such a sensor the line source can be said to diffuse heat into an infinite half space if one neglects the heat absorbed by the poorly conducting block into which the needle is embedded the rate of the temperature rise of the line source with respect to the logarithm of time elapsed since turning on the heater is inversely proportional to the conductivity in practice the rates of temperature rise are compared for the unknown and for a standard specimen a fused silica plate in our case the percentage of the total heat flowing into the sensor block is in general different for the standard and for the unknown thus possibly creating an error when the conductivity of the sensor block is neglected it was determined experimentally that the temperature rise for a silica plate is decreased only by 1 3 by the heat absorbed by the material of the sensor block an empirical equation is proposed to correct errors arising from this source this correction needs to be used only for materials of conductivity less than 2 mcal cm c s the equation gives somewhat larger but still acceptable conductivity values for substances in the range of 0 208 3 25 mcal cm c s as shown in table 1 and fig 2 for measurements on common rocks corrections for the heat diffused into the material of the sensor block can be neglected

estimating thermal conductivity in sedimentary basins using lithologic data and geophysical well logs a method for estimating in situ thermal conductivity profiles in oil and gas wells is advanced to rectify a major shortcoming in thermal analyses of sedimentary basins thermal conductivity estimates are made in a two stage procedure and are based on a model for the conductivity of mixtures and input data from lithological and geophysical logs first rock matrix conductivity for an arbitrary depth interval i e drill cuttings sample interval which is about 3 m is determined from the laboratory calibrated conductivities and volumetric representation of its individual lithologic components using a geometric mean model in situ conductivity is then estimated by a second application of the model correcting for temperature and porosity determined from geophysical logs the method is illustrated for three uinta basin utah wells that penetrate a series of tertiary sandstones shales and muddy carbonates detailed lithologic descriptions together with sonic and neutron logs were digitized and used for estimating in situ conductivity the validity of the method was tested by comparing the prediction against laboratory measurements on 565 samples from the same wells rock matrix thermal conductivity ranges from 1 6 to 6 8 w m k and is predicted within 20 of the actual measurement for 90 of the samples both in situ conductivity values and variations for a given lithologic unit are reduced at increased porosity and increased temperature thermal conductivity nomograms are presented as useful tools to predict directly the in situ thermal conductivit of a formation from a well log signal

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

thermophysical properties of the earth s crust in situ measurements from continental and ocean drilling knowledge of the variation of thermal conductivity and heat production with depth is critical to understanding the thermal state of the crust continental and oceanic drill holes provide unique opportunities for the calibration of empirical and theoretical models relating crustal thermal properties to physical and chemical properties these calibrations are based on more than 30 000 well log measurements of acoustic velocity both compressional and shear density porosity radioelement concentrations k u th and major element chemistry al si ca fe s mg na in formations ranging in age from 5 to 620 ma and in composition from granitic to gabbroic the mineralogical data available from induced gamma ray spectroscopy logs when combined with known mineral thermal conductivities in a model for the thermal conductivity of a crystalline aggregate enable the in situ application of a laboratory estimation technique and yield continuous conductivity profiles however mineralogy based conductivity models cannot account for the anisotropic conductivity observed in foliated metamorphic rocks a phonon conduction model which utilizes acoustic velocity and bulk density measurements is accurate within 15 in both isotropic and anisotropic formations of the upper continental crust and in oceanic crustal layers 2c and 3 in oceanic crustal layers 2a and 2b however the effects of fracturing on compressional and shear velocities lead to inaccurate results the heat flow heat production relationship which provides one method of determining subsurface heat production has well documented limitations allis 1979 and rybach and buntebarth 1982 1984 on the basis of laboratory measurements have proposed quantitative relationships between heat production and rock compositional and physical properties the well log k u and th data indicate that heat production can be predicted from compositional data within a factor of 2 or 3 predictions of heat production from acoustic velocity and bulk density measurements are only accurate to within an order of magnitude three factors account for these results 1 the natural variability of velocity and density for a given rock composition 2 the tendency of u and th to associate with secondary rather than primary minerals and 3 u and th redistribution through fluid flow and metamorphism thus seismic velocity based heat production profiles can at best be taken as first order estimates which may misrepresent the complexity of the continental crust however the correlation of formations of known heat production with subsurface structures when combined with a suite of existing techniques for estimating heat production may lead to more accurate results

in situ investigations of thermal conductivity heat production and past hydrothermal circulation in the cajon pass scientific drillhole california wireline logs from the cajon pass drillhole provide observations of crustal properties and processes near the san andreas fault mineralogical profiles developed from geochemical logs are combined with a technique for calculating thermal conductivity from the volume fractions of component minerals variations in the equilibrium temperature gradient correlate with conductivity contrasts and thus with lithology rather than with fluid circulation k u and th contents calculated from gamma spectroscopy logs yield heat production values which range from 1 3 to 2 4 w m averaging 1 8 w m in the section from 500 to 1800 m evidence for depletion of u relative to th raises the possibility of extensive fluid circulation in the past however discontinuity of depletion across faults suggests that the fluid regime responsible for u depletion predated san andreas faulting

geologic setting and lithologic column of the cajon pass deep drillhole the cajon pass deep drillhole penetrates a late tertiary basin developed on crystalline basement in the sw mojave desert 4 km from the san andreas fault cores continuous cuttings and geophysical logs from phase i show great diversity in rock types structure and alteration the hole encountered cajon formation arkoses granodiorite tonalite unusual megacrystic granite and augen gneiss granitic and pelitic gneisses with quartzite quartzofeldspathic orthogneiss cut by sheets of hornblende gabbro and interlayered mafic and quartzofeldspathic orthogneisses with rare calcsilicate intervals foliation and compositional layering have low dips throughout the column and layered gneisses contain 10 cm scale recumbent folds faults and alteration zones bound several rock units with low apparent dips basement cores are typically cut by steep fractures 1 mm wide that contain zeolites calcite or chlorite epidote fractures and faults decrease in abundance with depth

indian ocean zonal mode activity in a multicentury integration of a coupled aogcm consistent with climate proxy data 1 the coupled atmosphere ocean system over the indian ocean termed indian ocean zonal mode iozm and its activity over the past 200 years is analyzed in a paleoclimate simulation from a coupled atmosphere ocean general circulation model aogcm validation shows that the aogcm captures spatio temporal patterns of sea surface temperature anomalies as well as the seasonal phase locking feature of the iozm the period 1820 1880 exhibits a high frequency of climatically significant iozm events compared to a relatively low frequency in the 20th century this shift in frequency provides a climate dynamics background for the interpretation of proxy data from east africa a region subjected to anomalously strong october december precipitation during iozm events in the late 19th century east african lakes had highstands e g lake victoria and its glaciers stable extents e g kilimanjaro consistent with a wetter climate due to the higher frequency of iozm events

heat flow heat production and crustal structure in peri atlantic regions abstract a linear relationship is commonly observed between heat flow and heat generation it provides information about the distribution of radioelements with depth over large regions the linear relationship is no more tenable but points still cluster within an elongated trend in which a regression analysis provides the bulk reduced heat flow and a gross estimate of the heat production distribution with depth over the whole considered region when geological provinces share an identical heat flow heat generation relation they form a geothermal province data measurements in western europe suggest that at least two provinces should be considered one can be related to the hercynian crust and the second to the older caledonian crust we suggest that the depth obtained from thermal data corresponds to the depth of the mafic granulite layer western france south and central england share identical geothermal parameters which can be correlated with the depth of the granulitic layer down to 17 18 km data from scotland do not fit the relationship of south and central u k and present a lower slope indicating that the radiogenic enriched layer is shallow 8 10 km this correlates with the seismic structure of the caledonian crust where the granulite layer is observed at this depth data from scotland can be compared to those from norway newfoundland new hampshire and eastern appalachian crust where the same crustal composition is observed

radiocarbon dating of glacial dust layers and soils at kilimanjaro s northern ice field as the african climate history recorded in kilimanjaro s northern ice field nif is rapidly lost the age of the glacier remains disputed current age estimates from ice core data and glacial dynamics modeling disagree by an order of magnitude 11 700 vs 1000 years old we present radiocarbon dates of glacial dust and proximal soil samples collected from in and around the edge of the nif that support the hypothesis that the peripheral portions of the nif glacier are younger and more dynamic than the center samples of a dust rich ice layer 1 5 m above the base at the edge of the 40 m high glacier ice cliff were found to be 1600 790 years old these dates agree with the prediction of significant growth and shrinkage in glacial coverage over the last millennium the variation in radiocarbon ages likely arises from heterogeneity in the summit volcanic soils the main source of the dust recovered from the glacier and cryoconite microbial activity sediment samples of a supraglacial pond had modern radiocarbon ages further demonstrating the impact of cryoconite microbial communities on radiocarbon measurements of glacial samples after accounting for the variability in the sample ages and the effects of microbial activity we contend that the lower i e younger limit of the radiocarbon age range is the most reliable assessment of the age of the ice in which it was trapped

glacier recession on cerro charquini 16 s bolivia since the maximum of the little ice age 17th century cerro charquini bolivia cordillera real 5392 m a s l was selected as a site to reconstruct glacier recession since the maximum of the little ice age lia in the central andes five glaciers located on differently exposed slopes present comprehensive and well preserved morainic systems attributed to former centuries the moraines were dated by lichenometry and show a consistent organization on the different slopes the past geometry of the glaciers was reconstructed using ground topography and aerophotogrammetry lichenometric dating shows that the lia maximum occurred in the second half of the 17th century after which the glaciers have receded nearly continuously over the last decades of the 20th century 1983 97 recession rates increased by a factor of four on the northern and western slopes glaciers receded more than on the southern and eastern slopes by 78 and 65 of their lia maximum area respectively the mean equilibrium line altitude ela rose by about 160 m between the lia maximum and 1997 recession rates were analysed in terms of climatic signal suggesting that glacier recession since the lia maximum was mainly due to a change in precipitation and that the 19th century may have been drier for the 20th century a temperature rise of about 0 68c appears to be the main cause of glacier recession recent climatic conditions from 1983 to 1997 correspond to a mass deficit of about 1 36 m w e a 1 if such conditions persist the small glaciers below 5300 m a s l in the cordillera real should disappear completely in the near future

using neural networks to predict thermal conductivity from geophysical well logs summary we present a new approach based on neural networks to predict the thermal conductivity of sedimentary rocks from a set of geophysical well logs this method is calibrated on ocean drilling program odp data which provide several thousands of conductivity measurements combined with five geophysical well logs sonic density neutron porosity resistivity and gamma ray this data set is used to train multilayer perceptrons mlp and to find an empirical relationship between well logs mlp inputs and thermal conductivity mlp output validation tests suggest that mlp provide better estimates of thermal conductivity within 15 per cent confidence level than classical linear models and still give satisfying results with sets of only four well logs if neutron porosity is included in two odp sites 863b and 1109d mlp s predictions are compared to conventional mixing methods although this latter technique gives reliable results provided that rocks description is precise enough the mlp is more straightforward does not need any extra parameter and makes predictions in good agreement with the experimental trends this method will be useful in the estimation of heat flow from data acquired in scientific and industrial boreholes

late pleistocene climate conditions in the north chilean andes drawn from a climate glacier model a climate glacier model was used to reconstruct late glacial climate conditions from two case study glaciers at 18 and 22 s in the arid sub tropical western andes of northern chile the model uses i the geometry of the late glacial maximum glaciation ii modern diurnal and annual cycles amplitudes and lapse rates of the climate iii empirical statistical sublimation melt and accumulation models developed for this area and iv dynamic ice flow through two known cross sections for steady state conditions the model is validated with modern conditions and compares favorably with the glaciological features of today the mass balance model calculates the modern equilibrium line altitude at 18 s as high as 5850 m field data 5800 m whereas no glaciers exist in the fully arid southern area at 22 s despite altitudes above 6000 m and continuous permafrost for late glacial times the model results suggest a substantial increase in tropical summer precipitation ap 840 50 10 mm a 1 for the northern test area 1000 10 30 mm a 1 for the southern test area and a moderate temperature depression t 4 4 0 1 0 2 c at 18 s 3 2 0 1 c at 22 s extratropical frontal winter precipitation june september was 15 of the total annual precipitation a scenario with higher winter precipitation from the westerlies circulation belt does not yield a numerical solution which matches the observed geometry of the glaciers therefore we conclude that an equatorward displacement of the westerlies must be discarded as a possible explanation for the late pleistocene glaciation in the andes of northern chile

solar radiation cloudiness and longwave radiation over low latitude glaciers implications for mass balance modelling broadband radiation schemes parameterizations are commonly used tools in glacier mass balance modelling but their performance at high altitude in the tropics has not been evaluated in detail here we take advantage of a high quality 2 year record of global radiation g and incoming longwave radiation l measured on kersten glacier kilimanjaro east africa at 5873 m a s l to optimize parameterizations of g and l we show that the two radiation terms can be related by an effective cloud cover fraction neff s og or l can be modelled based on neff derived from measured l or g respectively at neff 1 g is reduced to 35 of clear sky g and l increases by 45 65 depending on altitude relative to clear sky l validation for a 1 year dataset of g and l obtained at 4850 m on glaciar artesonraju peruvian andes yields a satisfactory performance of the radiation scheme whether this performance is acceptable for mass balance studies of tropical glaciers is explored by applying the data from glaciar artesonraju to a physically based mass balance model which requires among others g and l as forcing variables uncertainties in modelled mass balance introduced by the radiation parameterizations do not exceed those that can be caused by errors in the radiation measurements hence this paper provides a tool for inclusion in spatially distributed mass balance modelling of tropical glaciers and or extension of radiation data when only g or l is measured

micro meteorological conditions for snow melt conditions meteorologiques des periodes de debut et de fin des fontes des neiges et glaces de glaciers alpins on utlise la temperature de l air l humidite les rayonnements total global reflechi le coefficient d echange turbulent utilise est 18 5 wm 2 k 1 il apparait que la neige peut fondre a 10 c et rester solide a 10 c

40ar 39ar dating of silurian and late devonian cleavages in lower greenschist facies rocks in the westminster terrane maryland usa 40 ar 39 ar dating of muscovite biotite and k feldspar combined with microstructural analysis of lower greenschist facies polymetamorphic phyllitic rocks and marbles were successfully used to decipher the thermal and tectonic histories of the westminster and adjacent terranes in western maryland the presence of unreset detrital muscovite in some samples demonstrates that temperatures in these rocks never exceeded the closure temperature for argon diffusion in muscovite 350 50 c minor biotite in some arkoses constrains the minimum metamorphic temperatures to 320 c these data show an early silurian ca 430 ma cleavage in the western part of the westminster terrane and a late devonian event ca 370 ma in the eastern westminster and adjacent potomac terranes these two cleavage domains are separated by the ne trending newly identified parrs ridge fault zone we propose that the sinistral transpressive collision of the carolina terrane with laurentia emplaced the western portion of the westminster terrane in the pennsylvania embayment along the martic fault where it was folded and cleaved at ca 430 ma but otherwise largely sheltered from later deformation the later late devonian dextral transpressive accretion of the outboard potomac terrane thrust rocks of the eastern westminster and potomac terranes to the west causing late devonian 360 370 ma s 2 cleavage in these rocks but only minimal discrete overprinting s 3 cleavages in rocks farther west final juxtaposition and thermal convergence of these terranes occurred along reactivated dextral strike slip faults in the alleghanian at ca 300 ma

seventy six years of mean mass balance rates derived from recent and re evaluated ice volume measurements on tropical lewis glacier mount kenya 1 lewis glacier on mt kenya has a unique history of detailed study making it among the best documented tropical glaciers here we present i a new ice volume determination based on a bedrock dem constructed from gpr data acquisition and ii the glacier s mean mass balance rates over the last 76 years derived from volume and area estimates based on seven historical maps and the newly determined bedrock topography total ice volume in 2010 was 1 90 0 30 10 6 m 3 with a mean maximum ice depth of 18 3 m 45 3 m which is one order of magnitude larger than previously published values in 2010 the glacier had lost 90 79 of its 1934 glacier volume area with the highest rates of ice volume loss occurring around the turn of the century computed mean mass balance rates covering the whole period of glaciological surveys of lewis glacier provide the longest record of tropical glacier change and show that the mean mass balance rate varies consistently with global estimates but the magnitude is always more negative than in other regions citation prinz r a fischer l nicholson and g kaser 2011 seventy six years of mean mass balance rates derived from recent and re evaluated ice volume measurements on tropical lewis glacier mount kenya geophys res lett 38 l20502 doi 10 1029 2011gl049208

elemental and mineralogical analyses using geochemical logs from the cajon pass scientific drillhole california and their preliminary comparison with core analyses estimates of elemental and mineralogical abundances from geochemical logs are compared to preliminary chemical and modal analyses from cores in the cajon pass scientific drillhole accuracies of log computed weight percent oxide and mineralogy determinations range from 10 to 30

relationships between the petrophysical properties density seismic velocity heat generation and mineralogical constitution the petrophysical properties density p compressional wave velocity v p and heat generation a exhibit considerable variation with rock type to characterize a given rock quantitatively a single parameter the cation fraction expressed by the k value has been found to be suited best 100 crystalline rocks have been sampled to cover the widest possible range in k value from silicic types like granophyres and granites through granodiorites tonalites diorites gabbros amphibolites hornblendites pyroxenites to ultrabasic rocks p k a and v p were determined experimentally the latter at 0 5 kbar 50 mpa the interrelations between these properties were established by regression analysis the relation k and v p k show a linear dependence whereas a k a and a v p follow exponential laws in a w m 3 12 20 230 5 k mole cm 3 in a 22 5 8 15 g cm 3 and in a 16 5 2 74 v p km s all correlation coefficients are better than 0 9

thermal conductivity of unconsolidated sediments with geophysical applications a theoretical model for the prediction of the thermal conductivity of unconsolidated granular sediments with application to sand shale mixtures is presented the sediment is modeled as an assemblage of grains of thermal conductivity s immersed in a pore fluid of thermal conductivity in order to take into account for the thermal interactions between the grains a differential effective medium approach is used to provide a relationship between the effective thermal conductivity of the isotropic mixtures of grains saturated by the pore fluid the porosity and the thermal conductivities of the grains and pore fluid the influence of the topology of the interconnected pore space is accounted for through the use of the electrical cementation exponent m which is related to the electrical formation factor f by f m where is the interconnected porosity the main assumption of the model lies in the small contiguity between the grains this assumption holds well for unconsolidated sand shale mixture sediments as demonstrated by comparing the model to available experimental data the model offers the possibility to derive thermal conductivity profiles from downholes measurements of natural radioactivity electrical resistivity and bulk density

glacier climate interaction at low latitudes in the low latitudes there is an absence of major thermal seasonality yet there are three different climate regimes related to global circulation patterns and their seasonal oscillation the humid inner tropics the dry subtropics and intermediate between these two the outer tropics for the respective glacier regimes the vertical profiles of specific mass balance vbps are modeled considering vertical gradients of accumulation air temperature and albedo the duration of the ablation period and a factor for the ratio between melting and sublimation the model is first calibrated with data from hintereisferner austrian alps and is then applied to tropical conditions the simulated vbp matches well the measured profiles from irian jaya and mount kenya due to lack of field evidence the subtropical vbp cannot be verified directly however application of the respective model versions separately to the humid and dry seasons of the outer tropical glaciar uruashraju cordillera blanca peru provides reasonable results glaciers in the humid inner tropics are considered to be most sensitive to variations in air temperature while dry subtropical glaciers are most sensitive to changes in air humidity the two seasons of the outer tropics have to be viewed from these different perspectives

determination of thermal conductivity for deep boreholes two methods for thermal conductivity determinations on rock cores and fragments were tested on a suite of samples from the kontinentales tiefbohrprogramm der bundesrepublik deutschland ktb superdeep drill hole in germany they were also compared with estimates of thermal conductivity using the mineral composition of the rock and physical well logs and with in situ thermal conductivity measurements laboratory methods provide reasonably precise determinations of the thermal conductivities of both solid core 5 and drill cuttings 10 at room temperature and pressure the most common methods presently used for crystalline rocks are the steady state divided bar db technique and the transient half space line source ls sample preparation and measurement times are comparable for the db and ls with sample preparation being more time consuming on average for isotropic rocks there is little to choose from between the two methods which both give reliable values of conductivity in the vertical direction the ls is easier to set up and use in field laboratory situations which renders it the preferred method for field reconnaissance the gneissic crystalline rocks penetrated by the ktb boreholes typically have anisotropy of the order of 10 20 the db provides unambiguous values of conductivity in a given direction so its use is preferable for obtaining both principal conductivities and the vertical component anisotropy can be estimated using ls measurements in many different directions but the potential for large random errors is much greater than with the more straightforward db approach for deep research wells the difficulties of extrapolating laboratory results to in situ conditions particularly temperature present additional obstacles to determining heat flow laboratory measurements of water saturated samples under in situ conditions combined with in situ measurements and judicious use of calculations based on mineralogy and well log derived physical properties can aid in the accurate characterization of thermal conductivity in deep wells the application of different methods helped to link variations of heat flow with depth in the ktb hole to the anisotropy of thermal conductivity or thermal refraction and thus allowed the calculation of background heat flux in this geologically complex area

seasonality in equatorial climate over the past 25 k y revealed by oxygen isotope records from mount kilimanjaro multiproxy analysis of a well dated 25 ka lake sediment sequence from lake challa on the eastern flank of mount kilimanjaro east africa reveals the climatic controls that govern both the lake s paleohydrology and the climate proxy record contained in the mountain s receding ice cap the oxygen isotope record extracted from diatom silica 18odiatom in lake challa sediments captured dry conditions during the last glacial period and a wet late glacial transition to the holocene interrupted by younger dryas drought further it faithfully traced gradual weakening of the southeastern monsoon during the holocene overall 18odiatom matches the branched isoprenoid tetraether bit index of rainfall induced soil runoff except during 25 22 ka and the past 5 k y when insolation forcing due to orbital precession enhanced the northeastern monsoon this pattern arises because during these two periods a weakened southeastern monsoon reduced the amount of rainfall during the long rainy season and enhanced the opposing effect of evaporation intensity and or length of the austral winter dry season importantly our lake based reconstruction of moisture balance seasonality in equatorial east africa also helps us understand the oxygen isotope record contained in mount kilimanjaro ice negative correlation between ice core 18o and lake challa 18odiatom implies that moisture balance is not the primary climate control on the long term trend in ice core 18o

deglaciated areas of kilimanjaro as a source of volcanic trace elements deposited on the ice cap during the late holocene abstract ice fields on kilimanjaro 5895 m a s l tanzania are retreating and 85 of the ice cover has been lost since 1912 the degree to which this recession is exceptional during the holocene is uncertain as age control of the entire ice stratigraphy exists only for the very shallow and very bottom ice of the northern ice field this empirical evidence suggests that the kilimanjaro ice cover may be a persistent holocene feature while a model based on maximum possible extent and a constant shrinkage rate of the summit glaciers suggests a cyclic decay time on the order of one to two centuries today the mass balance of these ice fields is negative and no persistent ice accumulation zones are observed over multiannual scales the expanding deglaciated area within the kilimanjaro caldera should act as an increasingly larger and productive source of volcanic origin aeolian dust that is quickly deposited onto the surface of the adjacent ice fields particularly in the seasonal absence of caldera snow cover variations in the local dust influx may directly influence albedo and the energy balance of these ice fields investigating the characteristics of insoluble material entrapped in the ice remnants of kilimanjaro can thus provide insights into the extent of ice and or continuity of the summit snow cover through time here we report the trace element composition linked to the insoluble particles entrapped in holocene kilimanjaro ice in the context of the current understanding of the past ice accumulation processes including solid precipitations and ablation contributing to build the horizontal caldera ice fields for this purpose we analysed an ice core drilled to bedrock from the northern ice field thought to span the late holocene 2200 bc 1950 ad the ultra low trace element concentrations recorded in this kilimanjaro core are consistent with a generally low volcanic dust source availability i e limited exposure of the deglaciated area in the caldera and fairly continuous ice accumulation during the late holocene in contrast the maximum concentrations for most of the trace elements recorded in the surface ice section suggest that the current lack of ice accumulation on the kilimanjaro ice fields is unusual over the last 4 ka

estimation of thermal conductivity from the mineral composition influence of fabric and anisotropy measured values of thermal conductivity from crystalline rocks are compared with values calculated from the mineral content using the layered model first thermal conductivity is estimated using data based on quasi isotropic mixtures of fragments or powder second the approach is applied on core data considering the anisotropy of some rock forming minerals the numerical value of estimated thermal conductivity is controlled by the quartz content sheet silicates control anisotropy and fabric in gneisses and their thermal consequences if imformation about the fabric of the rock is available the anisotropy of minerals can be considered in a layered model and this improves the estimation of thermal conductivity from mineral contents

a heat generation model for continental crust based on deep drilling in the baltic shield abstract this paper presents a heat generation model for the old continental crust on the basis of a new petrological model on the origin evolution and deep structure of the crust in which petrological geochemical and geophysical data obtained from the kola superdeep borehole and other deep boreholes drilled into the crystalline basement of the east european platform are taken into account the petrological section obtained from the borehole observations was extrapolated down to the moho boundary taking into consideration the evolution and generalized seismic model of the continental crust in our model the continental crust is subdivided into three layers a granite gneiss layer 0 17 km a charnokite enderbite layer 17 30 km and a basic layer including autochthonous restites of the protocrust 30 40 km the boundaries between the layers correspond to seismic surfaces k1 and k2 the crustal contribution to heat flow is estimated to be about 25 mw m2 52 of the total heat flow for the baltic shield and the mantle heat flow is 22 24 mw m2 a comparison is made between the heat generation model obtained in this study and the ones estimated from seismic velocity structure the difference in the heat generation value between these models may originate from the differing geological and tectonic history of the sampling localities

comment on recent glacial recession in the rwenzori mountains of east africa due to rising air temperature by richard g taylor lucinda mileham callist tindimugaya abushen majugu andrew muwanga and bob nakileza

an interpretation of wide angle compressional and shear wave data in southwest germany poisson s ratio and petrological implications shear wave velocity especially when used with compressional wave velocity is an important constraint on estimates of the composition and physical state of the continental lithosphere we present shear velocity s models derived from high quality s wave data along three profiles in southwest germany which combine with existing p wave velocity p models to give poisson s ratio in the crust and uppermost mantle we then construct a laterally varying petrological model of the crust by comparing our p and s models with published laboratory measured rock velocities in general poisson s ratio is 0 25 in the uppermost crust 0 22 0 23 in the mid crust but reaching a low of 0 15 in the black forest low p zone and varies laterally from 0 24 to 0 30 in the lower crust the average poisson s ratio of the whole crust is everywhere about 0 25 the laminated signature of the lower crust prominent on reflection and p wave refraction data is absent on the s wave refraction data implying a strong high low alternation of poisson s ratio in the lower crust this suggests that the lower crustal laminae represent mafic silicic compositional layering for example basic sills in an originally more quartz rich lower crust rather than alternating zones of high and low pore pressure there is no evidence for a shear wave low velocity zone lvz in the black forest mid crust despite the presence of a strong p wave lvz this suggests high quartz content and the presence of pore fluids at low not high pore pressure a clear p to s converted moho reflection pm s is visible on several shots indicating that the moho is at least locally a first order discontinuity no shear wave refractions from the upper mantle are present even where strong p wave refractions are observed possibly indicating an increase of poisson s ratio with depth in the upper mantle the petrological modeling indicates that the upper and middle crust are probably of granitic composition that the mid crustal low p zones have high quartz content and that the lower crust probably consists of granulites of laterally varying bulk composition from granodioritic to gabbroic the lower crust is more mafic in areas of high reflection density on seismic reflection profiles suggesting that the laminations are caused by mafic intrusions into the lower crust either prior to the variscan orogeny or during tertiary volcanic activity

solar heating rates and temperature profiles in antarctic snow and ice observations of temperature maxima at about 10 cm depth in cold antarctic snow during summer have previously been explained by proposing that solar heating is distributed with depth whereas thermal infrared cooling is localized at the surface the solid state greenhouse an increase in temperature from the surface to 10 cm depth t 4 k found by rusin 1961 on the antarctic plateau was successfully reproduced by schlatter 1972 in a combined radiative transfer and heat transfer model

well log derived estimates of thermal conductivity in crystalline rocks penetrated by the 4 km deep ktb vorbohrung well log measurements of compressional and shear velocity vp vs density and temperature from the 4 km deep ktb vorbohrung pilot hole were applied in a phonon conduction model for the thermal conductivity of a crystalline solid the resulting conductivity estimates were compared with conductivities klab measured on the nearly continuous 91 recovery core previous studies have shown the log derived conductivity klog to be within 15 of klab in isotropic or flat lying anisotropic crystalline rocks the section penetrated by the ktb pilot hole includes both predominantly isotropic metabasites and highly anisotropic gneisses with foliation dips ranging from horizontal to vertical the predictions of the phonon model were accurate within 4 in the metabasites but inaccurate by as much as 23 in the gneisses the accuracy of the model in the metabasites confirms the utility of the phonon conduction approach in isotropic or weakly anisotropic rocks but the discrepancies in the anisotropic gneisses remain unexplained these relatively large discrepancies between klog and klab correspond to depths at which laboratory measurements of vs under in situ conditions deviate from the sonic log vs this suggests that sonic log determinations of vs may not be reliable in dipping anisotropic rocks alternatively the laboratory vs measurements may not constitute a representative sample or there may be errors in the phonon conduction model if the discrepancies can be tied to errors in sonic log vs measurements the phonon conduction model may provide a tool for deriving thermal conductivity profiles of the earth s crust from seismic studies of vp and vs

is there a relationship between seismic velocity and heat production for crustal rocks abstract several investigators proposed an empirical relationship between heat production and seismic velocity for rocks typical of the continental crust these relationships could allow for indirect resolution of the distribution of heat producing elements with depth new heat production data for rock samples from the pikwitonei granulite domain and the sachigo granite greenstone subprovince of the superior province do not follow these relationships indicating that heat production cannot be reliably predicted from seismic velocity these two parameters are not likely to be related as velocity depends upon the major mineral constituents of rocks whereas heat production results from radiogenic components concentrated in both major and trace minerals in rocks

tropical ice core records evidence for asynchronous glaciation on milankovitch timescales over the last 28 years ice core records have been systematically recovered from ten high elevation ice fields nine of which are located in the low latitudes each core has provided new information about the regional climate and environmental change and together their records challenge existing paradigms about the earth s climate system when viewed collectively these ice core histories provide compelling evidence that the growth glaciation and decay deglaciation of large ice fields in the lower latitudes are often asynchronous both between the hemispheres and with high latitude glaciation that occurs on milankovitch timescales although stable isotopic records suggest that global scale cooling occurred during the last glacial stage lgs we contend that precipitation is the primary driver of glaciation in the low latitudes this is consistent with the time transgressive nature of precession driven changes in insolation and hence precipitation such that glaciers advance retreat in the tropics north of the equator while glaciers retreat advance in the tropics south of the equator thus the coeval inter hemispheric retreat of glaciers in the 20th century and the beginning of the 21st century is atypical copyright 2005 john wiley sons ltd

the stress heat flow paradox and thermal results from cajon pass conventional friction models predict a substantial thermal anomaly associated with active traces of strike slip faults but no such anomaly is observed from over 100 heat flow determinations along 1 000 km of the san andreas fault the cajon pass well is being drilled to bring deep heat flow and stress data to bear on this paradox preliminary heat flows to 1 7 km in the neighboring arkoma well indicated a positive anomaly of about 30 as would be expected if frictional resistance of the fault were 50 mpa or so but the pliocene and pleistocene history of the transverse ranges particularly high rates of uplift and erosion could also explain the anomaly preliminary stress results from cajon pass and a new interpretation of regional data by mark d zoback and colleagues suggests that the maximum compressive stress near the fault is almost normal to the trace and hence the resolved shear stress is low and the fault weak although this is consistent with long standing evidence from low heat flow vexing questions remain regarding the physics of strike slip faulting the heat flow data show large variability with depth probably from three dimensional structure and an overall decrease from over 90 mw m in the upper kilometer to less than 80 mw m in the lower 300 m with no evidence of advective heat transfer whether this decreasing trend is significant and whether it continues downward to the background value 70 mw m less the radiogenic heat from overlying rocks as expected for a weak fault must be verified with data from greater depth

radiogenic heat production of crustal rocks an assessment based on geochemical data a survey of the geochemical literature and unpublished data has resulted in the classification of u th and k concentrations by rock type over 2500 data entries have been compiled permitting calculation of their radiogenic heat production in the igneous rocks mean heat production ranges from highs of 12 20 heat production units hpu wm 3 in some peralkaline intrusives through 4 hpu in acidic 2 in intermediate and 1 in basic rocks to a low of 0 3 hpu in ultramafic rocks siliceous clastic rocks generally have greater heat production 2 to 4 hpu than do chemical sedimentary rocks including the carbonates 0 4 to 2 hpu the heat production of metamorphic rocks generally depends on the radioelement contents of their igneous and sedimentary predecessors modified by metamorphic processes based on estimates of the proportion of the continental crust that specific rock types occupy the weighted mean radiogenic heat production of the upper continental crust estimated from this data base is 3 hpu

fracture distribution and basement structure from measurements of electrical resistivity in the basement of the cajon pass scientific drillhole california in situ deep and shallow measurements of electrical resistivity recorded with the dual laterolog in the basement of the cajon pass scientific drillhole are compared with laboratory measurements of resistivity and porosity on fracture free core samples this comparison is the basis of a simple electrical model of the pore space of the rock from which both matrix and fracture porosity are derived in parallel the analysis of borehole electrical images obtained with the formation microscanner provides a means to identify the fractures that intersect the borehole wall to evaluate their frequency and to determine their orientation further processing of these images enables us to distinguish mineralized from fluid filled fractures the comparison of laterolog derived fracture porosity computed over a large volume of rock with a pair of fracture intensity profiles obtained from the analysis of the two images of the borehole wall is the key of a new technique by which drillhole related fractures either due to hydraulic fracturing or to stress induced borehole breakouts and natural fractures either open or mineralized are discriminated the fractures in the upper part of cajon pass basement are inferred from the analysis of in situ resistivity measurements as mostly steep and mineralized

mass balance of glaciers and ice caps consensus estimates for 1961 2004 1 working with comprehensive collections of directly measured data on the annual mass balance of glaciers other than the two ice sheets we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960 mass balance was slightly below zero around 1970 and has been growing more negative since then excluding peripheral ice bodies in greenland and antarctica global average specific balance for 1961 1990 was 219 112 kg m 2 a 1 representing 0 33 0 17 mm sle sea level equivalent a 1 for 2001 2004 the figures are 510 101 kg m 2 a 1 and 0 77 0 15 mm sle a 1 including the smaller greenland and antarctic glaciers global total balance becomes 0 38 0 19 mm sle a 1 for 1961 1990 and 0 98 0 19 mm sle a 1 for 2001 2004 for 1991 2004 the glacier contribution 0 77 0 26 mm sle a 1 is 20 30 of a recent estimate of 3 2 0 4 mm a 1 of total sea level rise for 1993 2005 while our error estimates are not rigorous we believe them to be liberal as far as they go but we also discuss several unquantified biases of which any may prove to be significant

estimation of thermal conductivity and its spatial variability in igneous rocks from in situ density logging characterisation of thermal conductivity of rock and its spatial variability by laboratory measurements is costly and time consuming there is an incentive to find more cost effective and rapid methods a new empirical relationship between density and thermal conductivity for igneous rocks has been found this paper explains that the relationship is based on the rock forming processes which in turn generate typical mineral compositions based on this relationship thermal conductivity can be estimated from geophysical density loggings experience has shown that this indirect method of determining the thermal conductivity can be used to characterise the spatial variability of thermal conductivity for certain rock types the spatial data can be used in the modelling of thermal rock domains applications of the statistical relationship are presented and illustrative examples are given of how spatial variability of thermal conductivity can be estimated based on the site investigations in a crystalline bedrock environment in sweden possible deficiencies of the method are identified such as uncertainties associated with different rock forming minerals methods of improvement are also discussed

thermophysical properties of the po basin rocks summary we present an analysis on thermal properties density and porosity of clastic chemical biochemical and intrasedimentary volcanic rocks collected from petroleum exploration wells of the po basin northern italy moreover we investigate the applicability of the hashin shtrikman s model for a mineral aggregate in combination with the zimmerman s model that takes pore shape into account to calculate the bulk thermal conductivity in case of macroscopically isotropic rocks deviations between predicted and measured values range from 2 2 per cent to 6 9 per cent and significantly decrease if a proper pore aspect ratio is chosen regarding the volumetric heat capacity approximate estimates were obtained by means of a weighted average of the volumetric heat capacity of the mineral grains and that of the pore filling water the differences between the computed and measured values range from 6 2 per cent to 4 9 per cent and on average the computed volumetric heat capacity is lower by 1 6 per cent the water loss during compaction and the temperature increase with depth are main factors controlling thermal properties an anisotropy effect occurs in the case of rocks rich in sheet silicates due to rotation of these minerals the vertical thermal conductivity of sheet silicates decreases exponentially with burial depth from 2 13 w m 1 k 1 at the surface to 0 52 w m 1 k 1 at 4 5 km the laboratory data allow the formulation of compaction curves

the cajon pass scientific drilling experiment overview of phase 1 the cajon pass scientific drilling project is a broad interdisciplinary experiment involving over two dozen principal scientists phase i of drilling coring and downhole experimentation began dec 8 1986 and ended april 2 1987 with the hole at a depth of 2115 m 82 m of core recovered and a wide range of downhole experiments successfully completed in this paper we briefly outline the scientific motivation for the project and provide an overview of the scientific program we also indicate some of the varied research areas in the earth sciences where data obtained in this experiment will provide unique and important insight into active in situ processes regional geologic structure and rock and fluid composition and origin

thermal conductivity from core and well log data abstract the relationships between thermal conductivity and other petrophysical properties have been analysed for a borehole drilled in a tertiary flysch sequence we establish equations that permit us to predict rock thermal conductivity from logging data a regression analysis of thermal conductivity bulk density and sonic velocity yields thermal conductivity with an average accuracy of better than 0 2 w m k 1 as a second step logging data are used to compute a lithological depth profile which in turn is used to calculate a thermal conductivity profile from a comparison of the conductivity depth profile and the laboratory data it can be concluded that thermal conductivity can be computed with an accuracy of less than 0 3 w m k 1 from conventional wireline data the comparison of two different models shows that this approach can be practical even if old and incomplete logging data are used the results can be used to infer thermal conductivity for boreholes without appropriate core data that are drilled in a similar geological setting

exposed cross sections through the continental crust implications for crustal structure petrology and evolution abstract the continental crust is exposed in cross section at numerous sites on the earth s surface these exposures which appear to have formed by obduction along great faults during continental collision may be recognized by exposures of deep crustal rocks exhibiting asymmetric patterns of metamorphic grade and age across the faults and by distinctive bouguer anomaly patterns reflecting dipping basement structure and an anomalously deep mantle from an examination of five complexes which meet these criteria it is concluded that the most prominent layering in the crust is not compositional but metamorphic the lower crust consists of granulite facies rocks of mafic to intermediate composition while the intermediate and shallow levels consist predominantly of amphibolite facies gneisses and greenschist facies supracrustal rocks respectively post metamorphic granitic intrusions are common at intermediate to shallow levels position of discontinuities in refraction velocity where present commonly correspond to changes in composition or metamorphic grade with depth the continental crust is characterized by lateral and vertical heterogeneities of varying scale which are the apparent cause of the complex seismic reflections recorded by cocorp field observations coupled with geochemical data indicate a complex evolution of the lower crust which can include anatexis multiple deformation polymetamorphism and reworking of older crustal material the complexity of the crust is thus the result of continuous evolution by recycling and metamorphism through time in a variety of tectonic environments

density and seismic velocity in relation to mineralogical constitution based on an ionic model for minerals considering silicates and spinels as a close packing of spherical ions the oxygen ions because of their relatively large ionic radius use up more than 90 of the total ionic volume the close packing of oxygen forms a framework structure with partially constant physical properties the cations including silicon are small enough to fit into the interstices between the large sized oxygen ions without widening their framework structure the idealized space filling character of the cations explains the variations in physical properties of minerals on the basis of one variable only the cation packing index labeled k value k number of cations per mole avogadro s number s molar volume this variable is used to describe the density as well as the seismic velocity it is shownthat relationships between k value and both density and seismic velocity have approximately a linear character

p t t paths and differential alleghanian loading and uplift of the bronson hill terrane south central new england late paleozoic u pb ages of sphene and 4 0 ar 3 9 ar cooling ages of amphibole and muscovite from rocks of the bronson hill terrane in connecticut and central massachusetts reflect a late paleozoic alleghanian overprinton acadian metamorphic rocks prograde alleghanian sphenes crystallized during the late pennsylvanian and eliminate the possibility that amphibole ages reflect delayed permian cooling from devonian acadian metamorphism fourteen new amphibole ages from connecticut form a north to south trend of decreasing age from 294 to 245 ma while in massachusetts four new amphibole ages together with three others from the literature produce a random carboniferous pattern seven new muscovite ages support existing data indicating uniform cooling throughout the bronson hill terrane through 350 c in the early triassic the rate of permian cooling defined by amphibole muscovite pairs increases from 4 c my in northern connecticut to 50 c my near long island sound hinged loading and hinged but delayed exhumation in the southern part of the bronson hill terrane with the hinge in central connecticut explain these ages and cooling rates as well as a southerly increasing metamorphic field gradient one dimensional thermal modeling indicates that loading of bronson hill rocks must have begun by the late mississippian the time of peak alleghanian metamorphic temperature decreases southward from early permian in northern connecticut to late permian to the south these results demonstrate that the metamorphic effects of the alleghanian orogeny are not restricted to the avalon terrane of southeastern new england on the contrary the alleghanian orogeny reset 4 0 ar 3 9 ar mineral ages recrystallized minerals partially melted felsic rocks and transposed fabrics at least as far west as the bronson hill terrane in south central new england

estimation of heat flow in oil wells based on relation between heat conductivity and sound velocity abstract based on published data it is assumed that the ratio of sound velocity to thermal conductivity exhibits a linear relation with formation temperature for most sedimentary rocks end page 1360 combination of this assumption with fourier s heat flow law yields q ln tl c tu c 1 a tl tu where tl and tu are the subsurface temperatures at the top and the bottom of an interval respectively tl and tu the sound travel times and q is the heat flow this relation has been tested in the case of 10 wells for which accurate data were available the relation generated satisfactory fits with the measured data for siliciclastic and carbonate rocks the parameters a and c take respective values of 1 039 and 80 031 heat flow q is expressed relative to the heat flow in the standard well bolderij 1 in the groningen gas field bolderij unit bu a method for estimating the relative heat flow from bottomhole tempeatures as observed during logging operations and sound travel times from well shoot in combination with sonic log data has been developed and tested in the viking and central grabens of the uk sector of the north sea in this region the mean relative heat flow using data from 120 wells is 0 601 bu with a standard deviation of 0 055 bu comparisons of calculated relative heat flow values in bu with heat flow values in si units conventionally obtained suggests that the bolderij unit is equivalent to about 77 mwm 2 end of article last page 1361

introduction background and implications of the linear heat flow heat production relationship the discovery in the late 1960s of the linear heat flow heat production relationship was a major advance in the understanding of the thermal structure of continents however although heat flow provinces have now been defined in all continents except antarctica the full implications of the relationship to deep thermal structure and the limitations of the relationship to applications in all terranes are not yet clear in addition despite major advances in the geochemical factors controlling the distribution of heat production in the crust a geochemical rationale for the relationship is lacking the relationship was originally interpreted in terms of one dimensional models but new two and three dimensional model studies suggest more complex interpretations in terms of lower crustal heat flow contributions to these problems in this special issue represent new observational geochemical and modeling studies of the relationship and a renewed attempt to understand the thermal and geochemical implications of the relationship

recent advances in rock physics the need to extract more information about the subsurface from geophysical and petrophysical measurements has led to a great interest in the study of the effect of rock and fluid properties on geophysical and petrophysical measurements rock physics research in the last few years has been concerned with studying the effect of lithology fluids pore geometry and fractures on velocity the mechanisms of attenuation of seismic waves the effect of anisotropy and the electrical and dielectric properties of rocks understanding the interrelationships between rock properties and their expression in geophysical and petrophysical data is necessary to integrate geophysical petrophysical and engineering data for the enhanced exploration and characterization of petroleum reservoirs the use of amplitude offsets s wave seismic data and full waveform sonic data will help in the discrimination of lithology the effect of in situ temperatures and pressures must be taken into account especially in fractured and u

contrasting p t t paths thermochronologic evidence for a late paleozoic final assembly of the avalon composite terrane in the new england appalachians strongly contrasting pressure temperature time paths for the avalon composite terrane and the structurally overlying putnam nashoba zone in eastern new england obtained from thermochronologic and thermobarometric data are best explained by a late paleozoic underthrusting of cover rocks by the avalon composite terrane we present new ar and u pb thermochronologic data that show that in the southern hope valley zone permian 280 ma anatectic metamorphic conditions of 700 c and 6 kbar were quenched by relatively rapid cooling 12 c m y and exhumation 0 5 km m y for 40 m y in contrast peak metamorphic conditions in the putnam nashoba zone predate silurian intrusions and slower cooling 3 5 c m y began at about 400 ma one dimensional thermal modeling suggests that these two belts were not in thermal equilibrium during the permian metamorphism of the avalon composite terrane because of the absence of high grade alleghanian metamorphism in rocks overlying the avalon terrane we conclude that high grade alleghanian metamorphism in the avalon terrane occurred east of rocks now overlying it and that significant motion between avalon and this cover occurred after peak alleghanian metamorphism similarly contrasting metamorphic histories between avalon inliers willimantic window massabesic complex gneiss pelham dome and their cover rocks reveals the regional significance of this boundary the core rocks all show permian cooling but the cover rocks show post acadian cooling ages decreasing from east to west to the pelham area where hornblende ages in avalon and cover differ by only 35 rather than 80 m y model calculations show that thermal equilibrium between instantaneously thrusted blocks of rocks is generally obtained in tens of millions of years consequently underthrusting of avalon is constrained to be middle mississippian or younger because the leading edge of the underthrusting block would have been heated the longest and would have most closely approached thermal equilibrium with its cover core rocks of the pelham dome must have been relatively close to this leading edge thus carboniferous to permian underplating from a generally eastward direction best explains these thermochronologic relationships

two dimensional inverse modeling of crustal thermal regime with application to east european geotraverses the modeling of crustal thermal regimes is basically the inference of subsurface distributions of heat flow density and temperature by continuing downward the near surface measurements of heat flow density temperature thermal conductivity and heat production to account for the uncertainties in the near surface data and in the subsurface distributions of thermal conductivity and heat production and to provide explicit estimates for the uncertainties in the resulting models we have employed a bayesian inverse formulation that incorporates the a priori information on model parameters in the form of a joint gaussian probability density function and that gives the inverse solution in the form of the most probable estimates and the a posteriori covariance matrix for the model parameters to illustrate the method we apply it to the modeling of thermal regimes along east european geotraverses eegt 5 and eegt 1 using both a linear 5 point finite difference and a quadrilateral isoparametric finite element discretization two features are emphasized first we introduce an a priori autocovariance function for the heat flow density at model base to help stabilize the solution second we demonstrate the improvement in solution accuracy and resolution when a priori temperature information is available and incorporated in the inversion for the geotraverses studied the finite difference and finite element formulations yield essentially identical results although there is a substantial difference in the extent of their parameterization in general the surface and basal heat flow densities are similar in shape implying a relatively uniform total crustal heat production across the geotraverses both the heat flow densities and the crustal temperatures exhibit strong lateral variations that appear to correlate with the tectonic age the heat flow densities and temperatures are low in the precambrian east european platform relatively higher in the variscan units high in the alps and very high in the pannonian basin the results support the presence of lateral variations of up to 40 m w m 2 in the moho heat flow density provided that one accepts as reasonable an a priori standard deviation of 25 for the surface heat flow density and an uncertainty of a factor of two for the heat production finally the a posteriori and the observed surface heat flow densities match well but exceptions occur in localized regions suggesting the presence of perturbing effects that cannot be accounted for in a steady state purely conductive model

a new approach to resolving climate cryosphere relations downscaling climate dynamics to glacier scale mass and energy balance without statistical scale linking 1 we present a novel combination of methods to quantify the local mass response of mountain glaciers to large scale circulation previously such multiscale approaches bypassed the mesoscale processes of the mountain induced atmospheric flow by statistical transfer functions or subgrid parameterizations and included simplified glacier mass balance mb models here we show on the basis of kilimanjaro east africa as a test case that a limited area atmospheric model lam and a process resolving mb model can be linked without statistical corrections at their interface this is evident from robust energy and mb patterns at the glacier surface regardless of whether the mb model is forced by 1 in situ meteorological measurements or 2 uncorrected output from the high resolution lam grid over the glacier area the latter is achieved by multiple grid nesting in the land atmosphere ocean domain of the lam since this setup resolves the mesoscale process space we also show the potential to increase knowledge of how dynamical thermodynamic and microphysical phenomena of the mountain induced flow affect glacier mb all these results are encouraging for future research because they demonstrate that a dynamical system which operates on very different space time scales can be quantified in a fully physical way if dynamic meteorology and glaciology are exploited in a complementary sense this will enhance the process understanding of forward problems glacier response to climate forcing and backward problems climate signal extraction from past extents of mountain glaciers

energy balance model validation on the top of kilimanjaro tanzania using eddy covariance data eddy covariance data collected over a horizontal surface on the largest ice body on kilimanjaro tanzania over 26 29 july 2005 were used to assess the uncertainty of calculating sublimation with a surface energy balance seb model data required for input to the seb model were obtained from an existing automatic weather station surface temperatures that were solved iteratively by the seb model were used to compute emitted longwave radiation turbulent heat fluxes using the aerodynamic bulk method and the subsurface heat flux roughness lengths for momentum and temperature which were found to be the most important input parameters controlling the magnitude of modelled bulk method turbulent heat fluxes were obtained using eddy covariance data the roughness length for momentum was estimated to be 1 7 10 3 m while the length for temperature was one order of magnitude smaller modelled sensible and latent heat fluxes bulk method compared well to eddy covariance data with root mean square differences between 3 1 and 4 8 w m 2 for both turbulent heat fluxes modelled sublimation accounted for about 90 of observed ablation confirming that mass loss by melting is much less important than sublimation on the horizontal surfaces of the remaining plateau glaciers on kilimanjaro

anomalous heat and mass budget of glaciar zongo bolivia during the 1997 98 el nino year during el nino southern oscillation enso warm events outer tropics glaciers usually experience a deficit of precipitation an increase of air temperature and a strongly negative mass balance at glaciar zongo bolivia this was particularly striking during the vigorous 1997 98 el nino event one of the strongest of the century and which resulted in an annual depth of runoff two thirds higher than normal we compare the energy balance on the glacier between two contrasting cycles 1996 97 la nina year and 1997 98 el nino year due to a 1 3 c increase of annual mean air temperature the sensible heat flux slightly increases from 6 1 to 9 8 w m 2 during the el nino year sublimation is reduced leaving more energy for melting le 18 1 w m 2 in 1996 97 and le 11 6 w m 2 in 1997 98 the main factor responsible for the dramatic increase in melting is the net all wave radiation which is three times higher in 1997 98 than in 1996 97 48 7 and 15 8 w m 2 respectively this sharp increase of net all wave radiation is related to the decrease of albedo due to the precipitation deficit

late taconian and pre acadian history of the new england appalachians of southwestern connecticut new u pb age determinations and field observations combined with published field relations refine the late taconian and pre acadian history of the new england appalachians of southwestern connecticut foliation within the camerons line shear zone was developed after 514 11 ma but prior to 445 1 5 ma this structure probably experienced renewed movement in the early silurian 437 2 ma as suggested by new xenotime growth in protomylonite metasedimentary and metavolcanic rocks east of camerons line were deposited were isoclinally folded and reached temperatures in excess of about 550 c before emplacement of small dioritic plutons of the 453 3 ma brookfield plutonic series igneous titanites in brookfield plutons cooled below u and pb diffusion e g 525 25 c in the latest ordovician to earliest silurian and were not reset in the acadian the newtown gneiss is a composite magmatic complex composed of quartz diorite 446 2 ma granodiorite 436 2 ma and granite 438 2 ma low 207 pb 204 pb feldspar isotopic compositions and 1150 ma zircon inheritance in the newtown gneiss and brookfield plutonic series are consistent with interaction with grenvillian crust or crustally derived material we propose that the newtown and harrison gneisses and possibly the brookfield plutonic series make up the plutonic roots of a late ordovician to early silurian 454 438 ma magmatic arc complex generated during subduction along the eastern north american continental margin magmatic activity was coeval with that in the bronson hill anticlinorium to the east ca 454 442 ma

is the decline of ice on kilimanjaro unprecedented in the holocene glaciers on kilimanjaro s highest peak kibo are currently regarded as a persistent feature of the holocene here we synthesize all available measurements observations and our understanding of current processes on kibo gained from intensive research over the past decade to formulate an alternative hypothesis about the age of these ice fields this suggests a shorter discontinuous history of the tabular shaped glaciers on kibo s plateau where typical life cycles of the ice may last only a few hundred years if life cycles overlap they are likely the cause of the observed steps in the plateau glaciers thus it is likely that ice has come and gone repeatedly on kibo s summit plateau throughout the holocene such a cyclicity is supported by lake derived proxy records

early local last glacial maximum in the tropical andes the local last glacial maximum in the tropical andes was earlier and less extensive than previously thought based on 106 cosmogenic ages from beryllium 10 dating from moraines in peru and bolivia glaciers reached their greatest extent in the last glacial cycle 34 000 years before the present and were retreating by 21 000 years before the present implying that tropical controls on ice volumes were asynchronous with those in the northern hemisphere our estimates of snowline depression reflect about half the temperature change indicated by previous widely cited figures which helps resolve the discrepancy between estimates of terrestrial and marine temperature depression during the last glacial cycle

kilimanjaro glaciers recent areal extent from satellite data and new interpretation of observed 20th century retreat rates 1 recent and long term variations in ice extent on kilimanjaro are investigated in the context of 20th century climate change in east africa quickbird satellite data show that the areal extent of glaciers on kilimanjaro is 2 51 km2 in february 2003 to assess glacier retreat on kilimanjaro two glacier systems are identified 1 plateau 5700 m and 2 slope 5700 m vertical wall retreat that governs the retreat of plateau glaciers is irreversible and changes in 20th century climate have not altered their continuous demise rapid retreat of slope glaciers at the beginning of the 20th century implies a strong departure from steady state conditions during this time this strong imbalance can only be explained by a sudden shift in climate which is not observed in the early 20th century results suggest glaciers on kilimanjaro are merely remnants of a past climate rather than sensitive indicators of 20th century climate change

a tectonic model for the late paleozoic of southeastern new england hornblende and biotite sup 40 ar sup 39 ar age spectra from rocks in south central connecticut help define a permian triassic cooling curve for the area together with petrologic and structural information a time temperature pressure strain path is established similar data for the narragansett basin in rhode island and massachusetts allow correlation of the late paleozoic histories of the two areas together these data suggest that in the late paleozoic south central new england was part of a fold thrust belt and the narragansett basin was a retroarc foreland basin nw se compression during the final assembly of pangaea resulted in se directed thrusting causing the development of clastic wedges in adjacent rhode island and massachusetts in the late carboniferous early permian a clockwise rotation of this deformation from nw to nne led to northward underthrusting and concomitant uplift of both eastern connecticut and rhode island in the permian and triassic

heat production and thermal conductivity of rocks from the pikwitonei sachigo continental cross section central manitoba implications for the thermal structure of archean crust the pikwitonei and sachigo subprovinces of central manitoba provide a cross sectional view of the superior province crust in cross section the upper to mid level crust is composed of synformal greenstone belts surrounded by tonalitic gneisses both of which are intruded by granitoid plutons this crustal structure persists downward into the granulite facies where keels of the greenstone belts can be found to constrain thermal models of the crust we measured heat production and thermal conductivity in 60 rocks from this terrain using standard gamma ray spectrometry and divided bar techniques large vertical and lateral heterogeneities in heat production in the upper crust are evident heat production is high in granites and metasedimentary rocks intermediate in tonalite gneisses and low in the portions of greenstone belts dominated by mafic meta igneous rocks in the deeper granulite facies rocks heat production decreases by a factor of two in the tonalitic gneisses and remains low in the high grad

heat production in an archean crustal profile and implications for heat flow and mobilization of heat producing elements we have measured concentrations of heat producing elements th u and k in 58 samples representative of the main lithologies in a 100 km transect of the superior province of the canadian shield from the michipicoten wawa greenstone belt near wawa ontario through a domal gneiss terrane of amphibolite grade to the granulite belt of the kapuskasing structural zone near foleyet this transect has been interpreted as an oblique cross section through some 25 km of crust uplifted along a major thrust fault and thus provides an opportunity to examine in detail a continuous profile into deep continental crust of archean age mean heat production values for these terranes based on aereal distribution of major rock types and calculated from their th u and k concentrations are michipicoten greenstone belt 0 72 w m 3 wawa domal gneiss terrane amphibolite grade 1 37 w m 3 kapuskasing granulites 0 44 w m 3 among the silicic plutonic rocks tonalites granites and their derivative gneisses the relatively large variation in heat production correlates with modal abundances of accessory minerals including allanite sphene zircon and apatite we interpret these variations as primary pre metamorphic the relatively high weighted mean heat production of the domal gneiss terrane can be accounted for by the larger proportion there of late stage th u and k rich granitoid plutons these may have been derived from the underlying kapuskasing granulite terrane leaving it slightly depleted in heat producing elements transport of th u and k therefore could have taken place in silicate melts rather than in aqueous or carbonic metamorphic fluids this conclusion is supported by the lack of a statistically significant difference in heat production between tonalites tonalite gneisses and mafic rocks of amphibolite versus granulite grade the pre metamorphic radioactivity profile for this crustal section is likely to have been uniformly low with a mean heat production value less than 1 w m 3 this result is distinctly different from measured profiles in more silicic terranes which show decreasing heat production with depth this implies fundamental differences in crustal radioactivity distributions between granitic and more mafic terranes and may be an important factor in selective reactivation of lithologically different terranes possibly resulting in preferential stabilization of basic terranes in the geological record our results indicate that a previously determined apparently linear heat flow heat production relationship for the kapuskasing area does not relate to the distribution of heat production with depth low but significant heat production 0 4 0 5 w m 3 continues to lower crustal depths with no correlation to the depth parameter from the linear relationship this low heat production may be a minimum average granulite heat production and suggests that in general heat flow through the moho is 8 10 mw m 2 lower than the reduced heat flow calculated from the heat flow heat production regression

intra surface radiative transfer limits the geographic extent of snow penitents on horizontal snowfields penitents are broad snow spikes and ridges that range in height between centimeters and meters two key features of penitents remain unexplained 1 they generally form at low latitudes and 2 their ridges and troughs have an east west orientation here we show that surface to surface exchange of shortwave radiation and the local geometry of the sun s daily arc across the sky are the key processes that in the absence of other effects determine the geographic extent of where surface roughness features can grow or dissipate on snowfields and ice surfaces as an application of our analysis we examine the question of the geographic extent of snow penitents on horizontal surfaces the results show that surface to surface radiative transfer can explain why penitents do not form on horizontal surfaces more than 558 off the equator we further show on the basis of the sun s path across the sky that penitents that are corrugated i e occur in long ridges or rows must align their ridge axis within 308 of the east west transect