In January 2020, a scientific borehole planning workshop sponsored by the International Continent... more In January 2020, a scientific borehole planning workshop sponsored by the International Continental Scientific Drilling Program was convened at Cornell University in the northeastern United States. Cornell is planning to drill test wells to evaluate the potential to use geothermal heat from depths in the range of 2700-4500 m and rock temperatures of about 60 to 120 • C to heat its campus buildings. Cornell encourages the Earth sciences community to envision how these boreholes can also be used to advance high-priority subsurface research questions. Because nearly all scientific boreholes on the continents are targeted to examine iconic situations, there are large gaps in understanding of the "average" intraplate continental crust. Hence, there is uncommon and widely applicable value to boring and investigating a "boring" location. The workshop focused on designing projects to investigate the coupled thermal-chemical-hydrological-mechanical workings of continental crust. Connecting the practical and scientific goals of the boreholes are a set of currently unanswered questions that have a common root: the complex relationships among pore pressure, stress, and strain in a heterogeneous and discontinuous rock mass across conditions spanning from natural to human perturbations and short to long timescales. The need for data and subsurface characterization vital for decision-making around the prospective Cornell geothermal system provides opportunities for experimentation, measurement, and sampling that might lead to major advances in the understanding of hydrogeology, intraplate seismicity, and fluid/chemical cycling. Subsurface samples could also enable regional geological studies and geobiology research. Following the workshop, the U.S. Department of Energy awarded funds for a first exploratory borehole, whose proposed design and research plan rely extensively on the ICDP workshop recommendations.
As part of an effort to develop a geothermal energy source beneath its campus, Cornell University... more As part of an effort to develop a geothermal energy source beneath its campus, Cornell University is planning to probe the “boring” old continental crust upon which many people live.
Example assumes: Hydrostatic conditions Brine density 1000-1250 kg/m 3 Water table at 37 m depth ... more Example assumes: Hydrostatic conditions Brine density 1000-1250 kg/m 3 Water table at 37 m depth Constrained by Fluid Composition Data Unconstrained 2) Engineering Research to Optimize Matching Heat Requirements to Geological Opportunities What rock type underlies Cornell? Utilize well cuttings USGS Geologic map of New York State with locations of wells whose cutting samples were studied by B. Valentino (2016, Cornell University). The color of the well marker (legend top left) indicates the major basement lithologies present in the borehole samples. Legend for colors of some of the major lithologic units exposed in the Adirondack Mountains shown below map. Colors of well samples do not match geologic map colors. Biotite and/or hornblende granite gneiss Mangerite, pyroxene-(hornblende) syenite gneiss Metanorthosite & anorthositic gneiss Interlayered metasedimentary rock & granitic, charnockitic, mangeritic, or syenitic gneiss Charnockite, mangerite, pyroxene-quartz syenite gneiss
Because of its low-temperature category, geothermal energy resources in the Northeastern United S... more Because of its low-temperature category, geothermal energy resources in the Northeastern United States have not been carefully explored. With today's population-driven demand for thermal energy in the Northeastern U.S., Enhanced Geothermal Systems (EGS) have shown the potential for using low-grade resources to provide both direct thermal use and combined-heat-and-power (Tester et al., 2006; Tester et al., 2010). This study provides a more complete picture of geothermal resources across the Appalachian Basin of New York State and Pennsylvania. A set of resource maps, including geothermal gradient, surface heat flow, and estimated depth to the 80 ˚C isotherm, were developed by incorporating thousands of new temperature-depth data collected as an incidental by-product of drilling for oil and natural gas in the NY-PA Appalachian Basin. Areas of favorable geothermal resource potential were found in central and southwestern New York, and along the eastern border of the Appalachian Basin in Pennsylvania.
Between 20-22°S the forearc basin of northern Chile consists of the Quillagua-Llamara sub-basin a... more Between 20-22°S the forearc basin of northern Chile consists of the Quillagua-Llamara sub-basin and the Pampa del Tamarugal. A distinguishing modern feature is that the Loa River flows in a deeply incised canyon through this atypically low elevation sector of the forearc basin, and then cuts west across the Coastal Cordillera. The basin fill facies demonstrates a persistent tendency to be a low sector of the forearc during the Late Miocene and the Late Pliocene. A new method to measure paleo-altitudes in the Atacama Desert system was applied to 18 locations with ancient gypsic soil in the Coastal Cordillera and forearc basin. The method determines whether soil gypsum formed under the influence of marine fog, and uses the modern altitude-fog relations to estimate paleo-altitude. For soil ages spanning about 5.5 – 1 Ma at three locations east of the Loa River, the ancient soil indicates that subsidence during the Pliocene and during the Quaternary lowered the forearc elevation by mini...
Prior to the 24-26 March 2015 extreme precipitation event that impacted northern Chile, the scena... more Prior to the 24-26 March 2015 extreme precipitation event that impacted northern Chile, the scenarios for Pleistocene and Holocene wetter paleoclimate intervals in the hyperarid core of the Atacama Desert had been attributed to eastern or southwestern moisture sources. The March 2015 precipitation event offered the first modern opportunity to evaluate a major regional precipitation event relative to those hypothetical paleoclimate scenarios. It was the first opportunity to determine the 18O and 2H composition of a major precipitation event that might eventually be preserved in geological materials. The driver for the March 2015 event was a synoptic-scale weather system, a cutoff cold upper-level low system that traversed the Pacific Ocean at a time of unusually warm temperatures of Pacific surface water. Ground-based precipitation data, stable isotopes in precipitation and river samples, NCEP/NCAR reanalysis atmospheric data and air mass tracking are utilized to connect the Earth su...
An elevation‐dependent relationship of the 87Sr/86Sr ratio of Holocene surface accumulations of s... more An elevation‐dependent relationship of the 87Sr/86Sr ratio of Holocene surface accumulations of sulfate salts is demonstrated for a continental margin hyperarid setting. In the Atacama Desert of northern Chile, gypsum and anhydrite of multiple origins exist widely on superficial materials that originated during the last 10,000 years. An important source of calcium sulfate is from offshore‐generated stratocumulus clouds that are advected onto the continent, where they generate fog that transfers water droplets to the ground surface which, upon evaporation, leaves calcium sulfate crystals. Meteorological measurements of the cloud base and top altitudes average ∼400 m and ∼1100 m above sea level (masl), respectively. The seawater ratio of 87Sr/86Sr (0.70917) is distinctively higher than that reported for weathered mean Andean rock (less than 0.70750). Samples of 28 modern surface salt accumulations for locations between 200 and 2950 masl and between ∼19°30′ and ∼21°30′S verify that 87S...
Based on study of the ages and nature of Cenozoic non marine clastic strata of the Manantiales ba... more Based on study of the ages and nature of Cenozoic non marine clastic strata of the Manantiales basin, at the bcundary between the Principal and Frontal Cordilleras of the Andes of southern San Juan Province, Argentina, the authors interpret deformation history of the La Ramada thrust belt. The 3,600 m thick section in the Manantiales basin coarsens upward from large sandstones near the base to coarse conglomerates in the upper several hundred meters, with tour smaller scale cycles of upward coarsening facies. The upper three facies cycles have lacustrine deposits at the base. In all but the uppermost cycle, the upper strata were deposited by river systems flowing subparallel to the mountain belt. The upper part of the upper cycle consists of deposits of an eastward inclined alluvial fan. Ages of the strata were determined from fission-track dating of zircons in four ash layers (17.1 to 11.5 Ma, with 20' uncertainties of 1.4 to 2.9 my) and magnetic polarity stratigraphy in the lower 3,000 m of the section. Thermal demagnetization revealed 18 polarity zones; these probably correlate to chrons 5n.2 through 5Er, or an age range of approximately 10.5-19 Ma for the lower 3,000 m. The authors interpret that the bases of the facies cycles, dated as 19, 15.7, 12.5, and 10.5 Ma, indicate approximate initiation ages of episodes of deformation. The authors suggest that faults in the western part of the thrust belt were active before 15.7 Ma, that principal shortening on the La Ramada fault began about 15.7 Ma, and that activity on the Espinacito thrust began about 12.5 Ma.
The western Andean mountain front forms the western edge of the central Andean Plateau. Between 1... more The western Andean mountain front forms the western edge of the central Andean Plateau. Between 18.5° and 22°S latitude, the mountain front has ∼3000 m of relief over ∼50 km horizontal distance that has developed in the absence of major local Neogene deformation. Models of the evolution of the plateau, as well as paleoaltimetry estimates, all call for continued large‐magnitude uplift of the plateau surface into the late Miocene (i.e., younger than 10 Ma). Longitudinal river profiles from 20 catchments that drain the western Andean mountain front contain several streams with knickpoint‐bounded segments that we use to reconstruct the history of post‐10 Ma surface uplift of the western flank of the central Andean Plateau. The generation of knickpoints is attributed to tectonic processes and is not a consequence of base level change related to Pacific Ocean capture, eustatic change, or climate change as causes for creating the knickpoint‐bounded stream segments observed. Minor valley‐fi...
Since 90 Ma, the nonmarine Salar de Atacama Basin has been the largest, deepest, and most persist... more Since 90 Ma, the nonmarine Salar de Atacama Basin has been the largest, deepest, and most persistent sedimentary basin of northern Chile. Integration of 200 km of two‐dimensional seismic reflection data with surface geological data clarifies Oligocene and Neogene evolution of the northern part of the basin. A normal fault with 6 ± 1 km of vertical separation controlled the western boundary of the basin during the accumulation of the Oligocene–lower Miocene Paciencia Group. The combination of this structure, a similar one in the Calama Basin, and regional structural data suggests that localized extension played an important role within a tectonic environment dominated by margin‐perpendicular compression and margin‐parallel strike‐slip deformation. Seismic data substantiate the surface interpretation that much of the Cordillera de la Sal ridge resulted from diapiric flow of the Paciencia Group. Diapiric flow initiated during the late early Miocene or middle Miocene, associated with a ...
The recognition of accreted terranes and their importance in orogenesis has spurred the search fo... more The recognition of accreted terranes and their importance in orogenesis has spurred the search for allochthonous fragments along the western and southern margins of South America. Here we present stratigraphic and petrologic data from Chile and Argentina between 29° and 33°S latitude that demonstrate the “suspect” nature of several major terranes, which we infer to have been accreted during the Paleozoic. Three lower‐middle Paleozoic terranes are described (from east to west): (1) the Pampeanas terrane, a Cambrian‐Devonian magmatic and metamorphic province built on late Precambrian basement at the margin of South America, (2) the Precordillera terrane, a Cambrian‐Devonian shelf‐slope‐oceanic basin assemblage bounded by mélanges on both sides and bearing many stratigraphic similarities to the lower‐middle Paleozoic of the Northern Appalachians, and (3) the “Chilenia” terrane, which has largely been obliterated by late Paleozoic magmatism and metamorphism. The distribution of Carbonif...
In January 2020, a scientific borehole planning workshop sponsored by the International Continent... more In January 2020, a scientific borehole planning workshop sponsored by the International Continental Scientific Drilling Program was convened at Cornell University in the northeastern United States. Cornell is planning to drill test wells to evaluate the potential to use geothermal heat from depths in the range of 2700-4500 m and rock temperatures of about 60 to 120 • C to heat its campus buildings. Cornell encourages the Earth sciences community to envision how these boreholes can also be used to advance high-priority subsurface research questions. Because nearly all scientific boreholes on the continents are targeted to examine iconic situations, there are large gaps in understanding of the "average" intraplate continental crust. Hence, there is uncommon and widely applicable value to boring and investigating a "boring" location. The workshop focused on designing projects to investigate the coupled thermal-chemical-hydrological-mechanical workings of continental crust. Connecting the practical and scientific goals of the boreholes are a set of currently unanswered questions that have a common root: the complex relationships among pore pressure, stress, and strain in a heterogeneous and discontinuous rock mass across conditions spanning from natural to human perturbations and short to long timescales. The need for data and subsurface characterization vital for decision-making around the prospective Cornell geothermal system provides opportunities for experimentation, measurement, and sampling that might lead to major advances in the understanding of hydrogeology, intraplate seismicity, and fluid/chemical cycling. Subsurface samples could also enable regional geological studies and geobiology research. Following the workshop, the U.S. Department of Energy awarded funds for a first exploratory borehole, whose proposed design and research plan rely extensively on the ICDP workshop recommendations.
As part of an effort to develop a geothermal energy source beneath its campus, Cornell University... more As part of an effort to develop a geothermal energy source beneath its campus, Cornell University is planning to probe the “boring” old continental crust upon which many people live.
Example assumes: Hydrostatic conditions Brine density 1000-1250 kg/m 3 Water table at 37 m depth ... more Example assumes: Hydrostatic conditions Brine density 1000-1250 kg/m 3 Water table at 37 m depth Constrained by Fluid Composition Data Unconstrained 2) Engineering Research to Optimize Matching Heat Requirements to Geological Opportunities What rock type underlies Cornell? Utilize well cuttings USGS Geologic map of New York State with locations of wells whose cutting samples were studied by B. Valentino (2016, Cornell University). The color of the well marker (legend top left) indicates the major basement lithologies present in the borehole samples. Legend for colors of some of the major lithologic units exposed in the Adirondack Mountains shown below map. Colors of well samples do not match geologic map colors. Biotite and/or hornblende granite gneiss Mangerite, pyroxene-(hornblende) syenite gneiss Metanorthosite & anorthositic gneiss Interlayered metasedimentary rock & granitic, charnockitic, mangeritic, or syenitic gneiss Charnockite, mangerite, pyroxene-quartz syenite gneiss
Because of its low-temperature category, geothermal energy resources in the Northeastern United S... more Because of its low-temperature category, geothermal energy resources in the Northeastern United States have not been carefully explored. With today's population-driven demand for thermal energy in the Northeastern U.S., Enhanced Geothermal Systems (EGS) have shown the potential for using low-grade resources to provide both direct thermal use and combined-heat-and-power (Tester et al., 2006; Tester et al., 2010). This study provides a more complete picture of geothermal resources across the Appalachian Basin of New York State and Pennsylvania. A set of resource maps, including geothermal gradient, surface heat flow, and estimated depth to the 80 ˚C isotherm, were developed by incorporating thousands of new temperature-depth data collected as an incidental by-product of drilling for oil and natural gas in the NY-PA Appalachian Basin. Areas of favorable geothermal resource potential were found in central and southwestern New York, and along the eastern border of the Appalachian Basin in Pennsylvania.
Between 20-22°S the forearc basin of northern Chile consists of the Quillagua-Llamara sub-basin a... more Between 20-22°S the forearc basin of northern Chile consists of the Quillagua-Llamara sub-basin and the Pampa del Tamarugal. A distinguishing modern feature is that the Loa River flows in a deeply incised canyon through this atypically low elevation sector of the forearc basin, and then cuts west across the Coastal Cordillera. The basin fill facies demonstrates a persistent tendency to be a low sector of the forearc during the Late Miocene and the Late Pliocene. A new method to measure paleo-altitudes in the Atacama Desert system was applied to 18 locations with ancient gypsic soil in the Coastal Cordillera and forearc basin. The method determines whether soil gypsum formed under the influence of marine fog, and uses the modern altitude-fog relations to estimate paleo-altitude. For soil ages spanning about 5.5 – 1 Ma at three locations east of the Loa River, the ancient soil indicates that subsidence during the Pliocene and during the Quaternary lowered the forearc elevation by mini...
Prior to the 24-26 March 2015 extreme precipitation event that impacted northern Chile, the scena... more Prior to the 24-26 March 2015 extreme precipitation event that impacted northern Chile, the scenarios for Pleistocene and Holocene wetter paleoclimate intervals in the hyperarid core of the Atacama Desert had been attributed to eastern or southwestern moisture sources. The March 2015 precipitation event offered the first modern opportunity to evaluate a major regional precipitation event relative to those hypothetical paleoclimate scenarios. It was the first opportunity to determine the 18O and 2H composition of a major precipitation event that might eventually be preserved in geological materials. The driver for the March 2015 event was a synoptic-scale weather system, a cutoff cold upper-level low system that traversed the Pacific Ocean at a time of unusually warm temperatures of Pacific surface water. Ground-based precipitation data, stable isotopes in precipitation and river samples, NCEP/NCAR reanalysis atmospheric data and air mass tracking are utilized to connect the Earth su...
An elevation‐dependent relationship of the 87Sr/86Sr ratio of Holocene surface accumulations of s... more An elevation‐dependent relationship of the 87Sr/86Sr ratio of Holocene surface accumulations of sulfate salts is demonstrated for a continental margin hyperarid setting. In the Atacama Desert of northern Chile, gypsum and anhydrite of multiple origins exist widely on superficial materials that originated during the last 10,000 years. An important source of calcium sulfate is from offshore‐generated stratocumulus clouds that are advected onto the continent, where they generate fog that transfers water droplets to the ground surface which, upon evaporation, leaves calcium sulfate crystals. Meteorological measurements of the cloud base and top altitudes average ∼400 m and ∼1100 m above sea level (masl), respectively. The seawater ratio of 87Sr/86Sr (0.70917) is distinctively higher than that reported for weathered mean Andean rock (less than 0.70750). Samples of 28 modern surface salt accumulations for locations between 200 and 2950 masl and between ∼19°30′ and ∼21°30′S verify that 87S...
Based on study of the ages and nature of Cenozoic non marine clastic strata of the Manantiales ba... more Based on study of the ages and nature of Cenozoic non marine clastic strata of the Manantiales basin, at the bcundary between the Principal and Frontal Cordilleras of the Andes of southern San Juan Province, Argentina, the authors interpret deformation history of the La Ramada thrust belt. The 3,600 m thick section in the Manantiales basin coarsens upward from large sandstones near the base to coarse conglomerates in the upper several hundred meters, with tour smaller scale cycles of upward coarsening facies. The upper three facies cycles have lacustrine deposits at the base. In all but the uppermost cycle, the upper strata were deposited by river systems flowing subparallel to the mountain belt. The upper part of the upper cycle consists of deposits of an eastward inclined alluvial fan. Ages of the strata were determined from fission-track dating of zircons in four ash layers (17.1 to 11.5 Ma, with 20' uncertainties of 1.4 to 2.9 my) and magnetic polarity stratigraphy in the lower 3,000 m of the section. Thermal demagnetization revealed 18 polarity zones; these probably correlate to chrons 5n.2 through 5Er, or an age range of approximately 10.5-19 Ma for the lower 3,000 m. The authors interpret that the bases of the facies cycles, dated as 19, 15.7, 12.5, and 10.5 Ma, indicate approximate initiation ages of episodes of deformation. The authors suggest that faults in the western part of the thrust belt were active before 15.7 Ma, that principal shortening on the La Ramada fault began about 15.7 Ma, and that activity on the Espinacito thrust began about 12.5 Ma.
The western Andean mountain front forms the western edge of the central Andean Plateau. Between 1... more The western Andean mountain front forms the western edge of the central Andean Plateau. Between 18.5° and 22°S latitude, the mountain front has ∼3000 m of relief over ∼50 km horizontal distance that has developed in the absence of major local Neogene deformation. Models of the evolution of the plateau, as well as paleoaltimetry estimates, all call for continued large‐magnitude uplift of the plateau surface into the late Miocene (i.e., younger than 10 Ma). Longitudinal river profiles from 20 catchments that drain the western Andean mountain front contain several streams with knickpoint‐bounded segments that we use to reconstruct the history of post‐10 Ma surface uplift of the western flank of the central Andean Plateau. The generation of knickpoints is attributed to tectonic processes and is not a consequence of base level change related to Pacific Ocean capture, eustatic change, or climate change as causes for creating the knickpoint‐bounded stream segments observed. Minor valley‐fi...
Since 90 Ma, the nonmarine Salar de Atacama Basin has been the largest, deepest, and most persist... more Since 90 Ma, the nonmarine Salar de Atacama Basin has been the largest, deepest, and most persistent sedimentary basin of northern Chile. Integration of 200 km of two‐dimensional seismic reflection data with surface geological data clarifies Oligocene and Neogene evolution of the northern part of the basin. A normal fault with 6 ± 1 km of vertical separation controlled the western boundary of the basin during the accumulation of the Oligocene–lower Miocene Paciencia Group. The combination of this structure, a similar one in the Calama Basin, and regional structural data suggests that localized extension played an important role within a tectonic environment dominated by margin‐perpendicular compression and margin‐parallel strike‐slip deformation. Seismic data substantiate the surface interpretation that much of the Cordillera de la Sal ridge resulted from diapiric flow of the Paciencia Group. Diapiric flow initiated during the late early Miocene or middle Miocene, associated with a ...
The recognition of accreted terranes and their importance in orogenesis has spurred the search fo... more The recognition of accreted terranes and their importance in orogenesis has spurred the search for allochthonous fragments along the western and southern margins of South America. Here we present stratigraphic and petrologic data from Chile and Argentina between 29° and 33°S latitude that demonstrate the “suspect” nature of several major terranes, which we infer to have been accreted during the Paleozoic. Three lower‐middle Paleozoic terranes are described (from east to west): (1) the Pampeanas terrane, a Cambrian‐Devonian magmatic and metamorphic province built on late Precambrian basement at the margin of South America, (2) the Precordillera terrane, a Cambrian‐Devonian shelf‐slope‐oceanic basin assemblage bounded by mélanges on both sides and bearing many stratigraphic similarities to the lower‐middle Paleozoic of the Northern Appalachians, and (3) the “Chilenia” terrane, which has largely been obliterated by late Paleozoic magmatism and metamorphism. The distribution of Carbonif...
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