Will Gosnold - Academia.edu (original) (raw)

Papers by Will Gosnold

Journal of Geophysical Research, 2010

Borehole temperature profiles provide a record of ground surface temperature (GST) change at the ... more Borehole temperature profiles provide a record of ground surface temperature (GST) change at the decadal to centennial time scale. GST histories reconstructed from boreholes are particularly useful in climate reconstruction if changes in GST and surface air temperature (SAT) are effectively coupled at decadal and longer time periods and it can be shown that borehole temperatures respond faithfully to surface temperature changes. We test these assumptions using three boreholes in northwestern Utah that have been repeatedly logged for temperature over a time span of 29 years. We report 13 temperaturedepth logs at the Emigrant Pass Observatory borehole GC-1, eight at borehole SI-1 and five at borehole DM-1, acquired between 1978 and 2007. Systematic subsurface temperature changes of up to 0.6°C are observed over this time span in the upper sections of the boreholes; below approximately 100 m any temperature transients are within observational noise. We difference the temperature logs to highlight subsurface transients and to remove any ambiguity resulting from steady state source of curvature. Synthetic temperature profiles computed from SAT data at nearby meteorological stations reproduce both the amplitude and pattern of the transient temperature observations, fitting the observations to within 0.03°C or better. This observational confirmation of the strong coupling between surface temperature change and borehole temperature transients lends further support to the use of borehole temperatures to complement SAT and multiproxy reconstructions of climate change.

Knowledge of subsurface temperatures obtained from heat flow and equilibrium temperature measurem... more Knowledge of subsurface temperatures obtained from heat flow and equilibrium temperature measurements were used as a basis for evaluation of the usefulness of the non-equilibrium temperatures of oil and gas wells for geothermal exploration. We find that the data in the Geothermal Gradient Map of North America do not conform to the thermal regime of Nebraska; and, that if the BHT data were the only data used, we would have underestimated our resource by about 80%. Differences in geological sections and heat flow between Nebraska and the U.S. Gulf coast where the correction data for the USGS map were obtained are the reasons for the discrepency. Some significant inaccuracies in the BHT data may not be correctable.

Analysis of temperature-depth (T-z) profiles from seven boreholes in northern Germany provided ne... more Analysis of temperature-depth (T-z) profiles from seven boreholes in northern Germany provided new borehole paleoclimate data from a previously unsampled region of Europe and offered a test of a widely used temperature-depth inversion scheme. Ground surface temperature histories (GSTH) determined by inversion of T-z profiles from the seven boreholes indicate stable temperatures from 1600 until the 1890's followed by consistent warming to the present. Four sites at Wulsdorf show warming from 1890 to present of 0.22, 0.23, 0.43, and 0.69 degrees and three sites at Bexhovede show warming of 0.58, 1.01 and 1.57 degrees. The boreholes were drilled in Quaternary deposits with till, silt, sand and gravel in a glacial spillway as well as Pliocene/Miocene sand and silt in the North German Basin. All of the boreholes are relatively shallow, 100 to 145 meters deep, but the thermal diffusivity of the silt and sand is low 0.5-0.9 * 10-6 m2 s-1 and the temperature information contained in the...

A combination of several sources including: radiogenic heating, processes of mantle and core form... more A combination of several sources including: radiogenic heating, processes of mantle and core formation and differentiation, delayed radiogenic heating, earthquakes, and tidal friction account for the surface heat flux in the Earth. Radiogenic heating is of much interest in various fields of geosciences. Inferences from recent experiments with reactor antineutrinos and solar neutrinos showed that the age of geoneutrinos is at hand for constraining radiogenic heat. Because of the deep penetrating properties of the neutrinos this type of radiation in the decay of the heat producing elements (HPE) is ideally suited for the investigation of the deep interiors of the Earth compared to conventional radiometric methods for HPE employing alpha-, beta- and gamma rays. This presentation will address the considerations for a dedicated geoneutrino detector to be set up for investigating the interior regions all the way to the center of the Earth.

Reproduction processes used in creating this map have slightly distorted linear dimensions, map s... more Reproduction processes used in creating this map have slightly distorted linear dimensions, map scale should be used with caution.

AAPG Bulletin, 1989

Stratigraphic and thermal conductivity data were combined to analyze the thermostratigraphy of th... more Stratigraphic and thermal conductivity data were combined to analyze the thermostratigraphy of the Williston basin. The present thermostratigraphy is characterized by geothermal gradients of the order of 60 mK/m in the Cenozoic and Mesozoic units, and 30 mK/m in the Paleozoic units. The differences in geothermal gradients are due to differences in thermal conductivities between the shale-dominated Mesozoic and Cenozoic units and the carbonate-dominated Paleozoic units. Subsidence and compaction rates were calculated for the basin and were used to determine models for time vs. depth and time vs. thermal conductivity relationships for the basin. The time/depth and time/conductivity relationships include factors accounting for thermal conductivity changes due to compaction, cementation, and temperature. The thermal history of the Bakken shale, a primary oil source rock in the Williston basin, was determined using four different models, and values for Lopatin's time-temperature index (TTI) were calculated for each model. The first model uses a geothermal gradient calculated from bottom-hole temperature data, the second uses present-day thermostratigraphy, the third uses the thermostratigraphic relationship determined in this analysis, and the fourth modifies the third by including assumed variations in continental heat flow. The thermal histories and the calculated TTI values differ markedly among the modelsmore » with TTI values differing by a factor of about two between some models.« less

Evidence for chemical interaction between plutons and meteoric ground water and analyses of the m... more Evidence for chemical interaction between plutons and meteoric ground water and analyses of the micro-scale and mega-scale distribution of uranium and thorium suggests that thermal convection in batholith complexes mobilizes uranium and may partially explain the exponential model for the vertical distribution of crustal heat production. Investigations of the distribution of uranium, thorium, and potassium within and around eight shallow plutons show evidence for mobilization and redistribution of uranium that was not bound in resistate-refractory minerals. Induced fission track radiography of thin sections was used to reveal the mineral associations of uranium within the rocks. Shallow plutons showing evidence of significant chemical interaction with meteoric groundwater (delta 18O) contain significant amounts of uranium in secondary hydrous minerals and secondary oxides. Plutons from deeper levels in the crust that show no evidence of interaction with meteoric ground water show ura...

AGU Fall Meeting Abstracts, Dec 1, 2002

ABSTRACT We have tested the accuracy of direct coupling between ground surface temperatures (GST)... more ABSTRACT We have tested the accuracy of direct coupling between ground surface temperatures (GST) and surface air temperatures (SAT) by comparison of daily, monthly, and annual SAT data with borehole data from the north central US and Canada. Synthetic T-z profiles generated from daily SAT data from an array of 89 automated meteorological stations were compared with repeat measurements of T-z profiles in boreholes initially logged ten to twenty-six years ago. This analysis shows that changes in borehole temperatures agree with changes in surface air temperatures and soil temperatures on multi-decade timescales. Generation of synthetic T-z profiles based on daily, monthly, and annual data produces the identical final profiles although more information is contained in the daily and monthly data. This analysis of different data sets yielded a surprising correlation between the TOA composite solar irradiance and the daily SAT and soil temperatures at the meteorological stations. This correlation is not evident with monthly and annual temperature data. This research is supported by NSF ATM-038384.

ABSTRACT Development of geothermal energy in any capacity is a positive step toward a sustainable... more ABSTRACT Development of geothermal energy in any capacity is a positive step toward a sustainable energy future. The resource is enormous and has the capacity to supply most future demand for electrical power if technology can meet some substantial challenges. Electrical power from geothermal energy has several compelling characteristics: a small footprint, low emissions, continuous availability, and sustainability. However, a common perception of geothermal energy is that it is available only in a few isolated localities and thus cannot contribute significantly to future electrical power needs. This perception neglects the stored thermal energy available everywhere in the upper 10 km of Earth's crust. We are investigating the potential for power production in oil-producing sedimentary basins where subsurface temperatures are sufficient for intermediate geothermal resources (90 °C -150 °C) at depths greater than 3 km. Existing estimates of geothermal energy stored at depth in sedimentary formations in the U.S. have been based only on a few aquifers and have not included the greater volume of fluids in oil-bearing formations. We reevaluated the accessible geothermal resource base for the north central US and found that including geothermal fluids in oil-producing formations increased the resource estimate by a factor of eight. Preliminary analysis of other basins indicates that the current estimate of thermal energy in the U.S. (100,000 EJ) may be of the order of 400,000 EJ. This is particularly significant due to recent technological advances leading to commercialization of scalable organic Rankine cycle (ORC) engines. Until recently, ORC systems were available only on an at large scale, i.e., 10s of MW, and had efficiencies of about 10 percent. Currently there are at least five manufacturers making scalable ORC systems in the 50 kW to 1 MW range, and at least one system has an efficiency of about 17 percent and is expected to attain an efficiency in the low 20s as it is scaled up to produce power in the MW range. Values needed for these systems are temperatures of 92+ °C and flow rates of 140-1000 gpm. In a detailed analysis of the North Dakota part of the Williston Basin, we used heat flow, bottom-hole temperatures, and measured temperature gradients to calculate the energy contained within specific formations having temperatures in the range of 100 °C to 150 °C. We find that at a 2% recovery factor, approximately 4500 MW/hr can be recovered at depths of 3-4 km. North Dakota currently produces approximately 3100 MW/hr from non-renewable sources such as coal and petroleum. We conclude that the geothermal resource in the Williston Basin could completely replace fossil fuels as an electrical power supply for North Dakota.

The results of the first three years of geothermal research in Nebraska are encouraging in their ... more The results of the first three years of geothermal research in Nebraska are encouraging in their promise for the discovery and development of low-temperature geothermal resources and from the standpoint of scientific value. A sucessful method for geothermal exploration has been developed and extensive low-temperature geothermal deposits have been discovered in Cretaceous age rocks that underlie a total area of about 107,000 km/sup 2/ and contain about 1000 x 10/sup 18/ J of stored energy. Heat flow data indicate zones of large-scale, slow flow in deep aquifers. This discovery of deep aquifer flow patterns by surface heat flow has important implications for both geothermics and hydrology. The heat flow data also indicate some areas of high heat flow that may be due to high radioactive heat generation in the Precambrian crystalline rocks. One of the original tasks of the program is evaluation of the bottom hole temperatures (BHT) for more than 14,000 oil and gas exploration wells. The...

The geothermal method to reconstruct the past ground surface temperature (GST) history by inverti... more The geothermal method to reconstruct the past ground surface temperature (GST) history by inverting the present-day temperature-depth (T-z) distribution measured in a hole has become a useful paleoclimate reconstruction tool. Subsurface temperature field is sensitive to changes in the surface conditions (reflecting changing climate), which slowly propagate downwards producing tiny transient departures from the steady state T-z distribution. Several old holes originally drilled for heat flow research and carefully repeatedly logged within the last 20-30 years present good conditions for testing the coherence between GST data inferred from measured T-z profiles and the surface air temperature (SAT) record. A project was proposed to resolve differences between the multi-proxy and borehole paleoclimate record to address the separation of the potential anthropogenic component from the natural radiative forcing of the present climate warming. Here we present preliminary results for four h...

This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees. makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This report has been reproduced directly from the best available copy.

ABSTRACT Several elements of terrestrial heat flow indicate that post-glacial warming in parts of... more ABSTRACT Several elements of terrestrial heat flow indicate that post-glacial warming in parts of northern hemisphere continents may have been of the order of 12° C to15° C rather than 3° C to 5° C as is generally accepted in terrestrial heat flow research. The signal we observe is a subtle but systematic curvature in the temperature gradient in the upper 2 km of the crust. Heat flow in high latitude regions of Europe and North America shows a systematic increase in heat flow with depth. This is observed in individual boreholes and in ensembles of heat flow determinations at different depths in different boreholes. In Europe, the increase in heat flow with depth has been observed by analysis of more than 1500 deep boreholes located throughout the Fennoscandian Shield, East European Platform, Danish Basin, Germany, Czech Republic, and Poland. There are significantly fewer deep boreholes in North America, but the increase in heat flow with depth appears in examination of a suite of 759 sites in the IHFC Global Heat Flow Database for the region east of the Rocky Mountains and north of latitude 40 N. These ensemble observations indicate the presence of a post-glacial warming signal, but they do not provide a precise estimate of the amplitude. We have estimated the amplitude of warming in the north central U. S. using temperature gradient measurements and thermal maturity data from the Williston Basin. The rocks in the upper 2 km are relatively homogenous Tertiary and Cretaceous marine shales. Thermal gradients in thick clastic sediments should decrease with depth as thermal conductivity increases due to compaction. However, temperature vs. depth profiles in the basin increase with depth throughout the upper 2 km. Also, thermally mature Bakken Formation (Ordovician-Mississippian) occurs at shallow depths on the eastern flank of the basin in disagreement with thermal history calculations based on heat flow determined from shallow (less than 400 m) boreholes. Reconciling curvature in the temperature gradients and thermal history models yields an estimate of 12 to 15 °C of post glacial warming.

Journal of Geophysical Research, 2010

Borehole temperature profiles provide a record of ground surface temperature (GST) change at the ... more Borehole temperature profiles provide a record of ground surface temperature (GST) change at the decadal to centennial time scale. GST histories reconstructed from boreholes are particularly useful in climate reconstruction if changes in GST and surface air temperature (SAT) are effectively coupled at decadal and longer time periods and it can be shown that borehole temperatures respond faithfully to surface temperature changes. We test these assumptions using three boreholes in northwestern Utah that have been repeatedly logged for temperature over a time span of 29 years. We report 13 temperaturedepth logs at the Emigrant Pass Observatory borehole GC-1, eight at borehole SI-1 and five at borehole DM-1, acquired between 1978 and 2007. Systematic subsurface temperature changes of up to 0.6°C are observed over this time span in the upper sections of the boreholes; below approximately 100 m any temperature transients are within observational noise. We difference the temperature logs to highlight subsurface transients and to remove any ambiguity resulting from steady state source of curvature. Synthetic temperature profiles computed from SAT data at nearby meteorological stations reproduce both the amplitude and pattern of the transient temperature observations, fitting the observations to within 0.03°C or better. This observational confirmation of the strong coupling between surface temperature change and borehole temperature transients lends further support to the use of borehole temperatures to complement SAT and multiproxy reconstructions of climate change.

Knowledge of subsurface temperatures obtained from heat flow and equilibrium temperature measurem... more Knowledge of subsurface temperatures obtained from heat flow and equilibrium temperature measurements were used as a basis for evaluation of the usefulness of the non-equilibrium temperatures of oil and gas wells for geothermal exploration. We find that the data in the Geothermal Gradient Map of North America do not conform to the thermal regime of Nebraska; and, that if the BHT data were the only data used, we would have underestimated our resource by about 80%. Differences in geological sections and heat flow between Nebraska and the U.S. Gulf coast where the correction data for the USGS map were obtained are the reasons for the discrepency. Some significant inaccuracies in the BHT data may not be correctable.

Analysis of temperature-depth (T-z) profiles from seven boreholes in northern Germany provided ne... more Analysis of temperature-depth (T-z) profiles from seven boreholes in northern Germany provided new borehole paleoclimate data from a previously unsampled region of Europe and offered a test of a widely used temperature-depth inversion scheme. Ground surface temperature histories (GSTH) determined by inversion of T-z profiles from the seven boreholes indicate stable temperatures from 1600 until the 1890's followed by consistent warming to the present. Four sites at Wulsdorf show warming from 1890 to present of 0.22, 0.23, 0.43, and 0.69 degrees and three sites at Bexhovede show warming of 0.58, 1.01 and 1.57 degrees. The boreholes were drilled in Quaternary deposits with till, silt, sand and gravel in a glacial spillway as well as Pliocene/Miocene sand and silt in the North German Basin. All of the boreholes are relatively shallow, 100 to 145 meters deep, but the thermal diffusivity of the silt and sand is low 0.5-0.9 * 10-6 m2 s-1 and the temperature information contained in the...

A combination of several sources including: radiogenic heating, processes of mantle and core form... more A combination of several sources including: radiogenic heating, processes of mantle and core formation and differentiation, delayed radiogenic heating, earthquakes, and tidal friction account for the surface heat flux in the Earth. Radiogenic heating is of much interest in various fields of geosciences. Inferences from recent experiments with reactor antineutrinos and solar neutrinos showed that the age of geoneutrinos is at hand for constraining radiogenic heat. Because of the deep penetrating properties of the neutrinos this type of radiation in the decay of the heat producing elements (HPE) is ideally suited for the investigation of the deep interiors of the Earth compared to conventional radiometric methods for HPE employing alpha-, beta- and gamma rays. This presentation will address the considerations for a dedicated geoneutrino detector to be set up for investigating the interior regions all the way to the center of the Earth.

Reproduction processes used in creating this map have slightly distorted linear dimensions, map s... more Reproduction processes used in creating this map have slightly distorted linear dimensions, map scale should be used with caution.

AAPG Bulletin, 1989

Stratigraphic and thermal conductivity data were combined to analyze the thermostratigraphy of th... more Stratigraphic and thermal conductivity data were combined to analyze the thermostratigraphy of the Williston basin. The present thermostratigraphy is characterized by geothermal gradients of the order of 60 mK/m in the Cenozoic and Mesozoic units, and 30 mK/m in the Paleozoic units. The differences in geothermal gradients are due to differences in thermal conductivities between the shale-dominated Mesozoic and Cenozoic units and the carbonate-dominated Paleozoic units. Subsidence and compaction rates were calculated for the basin and were used to determine models for time vs. depth and time vs. thermal conductivity relationships for the basin. The time/depth and time/conductivity relationships include factors accounting for thermal conductivity changes due to compaction, cementation, and temperature. The thermal history of the Bakken shale, a primary oil source rock in the Williston basin, was determined using four different models, and values for Lopatin's time-temperature index (TTI) were calculated for each model. The first model uses a geothermal gradient calculated from bottom-hole temperature data, the second uses present-day thermostratigraphy, the third uses the thermostratigraphic relationship determined in this analysis, and the fourth modifies the third by including assumed variations in continental heat flow. The thermal histories and the calculated TTI values differ markedly among the modelsmore » with TTI values differing by a factor of about two between some models.« less

Evidence for chemical interaction between plutons and meteoric ground water and analyses of the m... more Evidence for chemical interaction between plutons and meteoric ground water and analyses of the micro-scale and mega-scale distribution of uranium and thorium suggests that thermal convection in batholith complexes mobilizes uranium and may partially explain the exponential model for the vertical distribution of crustal heat production. Investigations of the distribution of uranium, thorium, and potassium within and around eight shallow plutons show evidence for mobilization and redistribution of uranium that was not bound in resistate-refractory minerals. Induced fission track radiography of thin sections was used to reveal the mineral associations of uranium within the rocks. Shallow plutons showing evidence of significant chemical interaction with meteoric groundwater (delta 18O) contain significant amounts of uranium in secondary hydrous minerals and secondary oxides. Plutons from deeper levels in the crust that show no evidence of interaction with meteoric ground water show ura...

AGU Fall Meeting Abstracts, Dec 1, 2002

ABSTRACT We have tested the accuracy of direct coupling between ground surface temperatures (GST)... more ABSTRACT We have tested the accuracy of direct coupling between ground surface temperatures (GST) and surface air temperatures (SAT) by comparison of daily, monthly, and annual SAT data with borehole data from the north central US and Canada. Synthetic T-z profiles generated from daily SAT data from an array of 89 automated meteorological stations were compared with repeat measurements of T-z profiles in boreholes initially logged ten to twenty-six years ago. This analysis shows that changes in borehole temperatures agree with changes in surface air temperatures and soil temperatures on multi-decade timescales. Generation of synthetic T-z profiles based on daily, monthly, and annual data produces the identical final profiles although more information is contained in the daily and monthly data. This analysis of different data sets yielded a surprising correlation between the TOA composite solar irradiance and the daily SAT and soil temperatures at the meteorological stations. This correlation is not evident with monthly and annual temperature data. This research is supported by NSF ATM-038384.

ABSTRACT Development of geothermal energy in any capacity is a positive step toward a sustainable... more ABSTRACT Development of geothermal energy in any capacity is a positive step toward a sustainable energy future. The resource is enormous and has the capacity to supply most future demand for electrical power if technology can meet some substantial challenges. Electrical power from geothermal energy has several compelling characteristics: a small footprint, low emissions, continuous availability, and sustainability. However, a common perception of geothermal energy is that it is available only in a few isolated localities and thus cannot contribute significantly to future electrical power needs. This perception neglects the stored thermal energy available everywhere in the upper 10 km of Earth's crust. We are investigating the potential for power production in oil-producing sedimentary basins where subsurface temperatures are sufficient for intermediate geothermal resources (90 °C -150 °C) at depths greater than 3 km. Existing estimates of geothermal energy stored at depth in sedimentary formations in the U.S. have been based only on a few aquifers and have not included the greater volume of fluids in oil-bearing formations. We reevaluated the accessible geothermal resource base for the north central US and found that including geothermal fluids in oil-producing formations increased the resource estimate by a factor of eight. Preliminary analysis of other basins indicates that the current estimate of thermal energy in the U.S. (100,000 EJ) may be of the order of 400,000 EJ. This is particularly significant due to recent technological advances leading to commercialization of scalable organic Rankine cycle (ORC) engines. Until recently, ORC systems were available only on an at large scale, i.e., 10s of MW, and had efficiencies of about 10 percent. Currently there are at least five manufacturers making scalable ORC systems in the 50 kW to 1 MW range, and at least one system has an efficiency of about 17 percent and is expected to attain an efficiency in the low 20s as it is scaled up to produce power in the MW range. Values needed for these systems are temperatures of 92+ °C and flow rates of 140-1000 gpm. In a detailed analysis of the North Dakota part of the Williston Basin, we used heat flow, bottom-hole temperatures, and measured temperature gradients to calculate the energy contained within specific formations having temperatures in the range of 100 °C to 150 °C. We find that at a 2% recovery factor, approximately 4500 MW/hr can be recovered at depths of 3-4 km. North Dakota currently produces approximately 3100 MW/hr from non-renewable sources such as coal and petroleum. We conclude that the geothermal resource in the Williston Basin could completely replace fossil fuels as an electrical power supply for North Dakota.

The results of the first three years of geothermal research in Nebraska are encouraging in their ... more The results of the first three years of geothermal research in Nebraska are encouraging in their promise for the discovery and development of low-temperature geothermal resources and from the standpoint of scientific value. A sucessful method for geothermal exploration has been developed and extensive low-temperature geothermal deposits have been discovered in Cretaceous age rocks that underlie a total area of about 107,000 km/sup 2/ and contain about 1000 x 10/sup 18/ J of stored energy. Heat flow data indicate zones of large-scale, slow flow in deep aquifers. This discovery of deep aquifer flow patterns by surface heat flow has important implications for both geothermics and hydrology. The heat flow data also indicate some areas of high heat flow that may be due to high radioactive heat generation in the Precambrian crystalline rocks. One of the original tasks of the program is evaluation of the bottom hole temperatures (BHT) for more than 14,000 oil and gas exploration wells. The...

The geothermal method to reconstruct the past ground surface temperature (GST) history by inverti... more The geothermal method to reconstruct the past ground surface temperature (GST) history by inverting the present-day temperature-depth (T-z) distribution measured in a hole has become a useful paleoclimate reconstruction tool. Subsurface temperature field is sensitive to changes in the surface conditions (reflecting changing climate), which slowly propagate downwards producing tiny transient departures from the steady state T-z distribution. Several old holes originally drilled for heat flow research and carefully repeatedly logged within the last 20-30 years present good conditions for testing the coherence between GST data inferred from measured T-z profiles and the surface air temperature (SAT) record. A project was proposed to resolve differences between the multi-proxy and borehole paleoclimate record to address the separation of the potential anthropogenic component from the natural radiative forcing of the present climate warming. Here we present preliminary results for four h...

This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees. makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This report has been reproduced directly from the best available copy.

ABSTRACT Several elements of terrestrial heat flow indicate that post-glacial warming in parts of... more ABSTRACT Several elements of terrestrial heat flow indicate that post-glacial warming in parts of northern hemisphere continents may have been of the order of 12° C to15° C rather than 3° C to 5° C as is generally accepted in terrestrial heat flow research. The signal we observe is a subtle but systematic curvature in the temperature gradient in the upper 2 km of the crust. Heat flow in high latitude regions of Europe and North America shows a systematic increase in heat flow with depth. This is observed in individual boreholes and in ensembles of heat flow determinations at different depths in different boreholes. In Europe, the increase in heat flow with depth has been observed by analysis of more than 1500 deep boreholes located throughout the Fennoscandian Shield, East European Platform, Danish Basin, Germany, Czech Republic, and Poland. There are significantly fewer deep boreholes in North America, but the increase in heat flow with depth appears in examination of a suite of 759 sites in the IHFC Global Heat Flow Database for the region east of the Rocky Mountains and north of latitude 40 N. These ensemble observations indicate the presence of a post-glacial warming signal, but they do not provide a precise estimate of the amplitude. We have estimated the amplitude of warming in the north central U. S. using temperature gradient measurements and thermal maturity data from the Williston Basin. The rocks in the upper 2 km are relatively homogenous Tertiary and Cretaceous marine shales. Thermal gradients in thick clastic sediments should decrease with depth as thermal conductivity increases due to compaction. However, temperature vs. depth profiles in the basin increase with depth throughout the upper 2 km. Also, thermally mature Bakken Formation (Ordovician-Mississippian) occurs at shallow depths on the eastern flank of the basin in disagreement with thermal history calculations based on heat flow determined from shallow (less than 400 m) boreholes. Reconciling curvature in the temperature gradients and thermal history models yields an estimate of 12 to 15 °C of post glacial warming.