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John A. Harper - One of the best experts on this subject based on the ideXlab platform.
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a geochemical context for stray gas investigations in the northern appalachian basin implications of analyses of natural gases from neogene through Devonian Age strata
AAPG Bulletin, 2014Co-Authors: Fred J. Baldassare, Mark A. Mccaffrey, John A. HarperAbstract:As the pace of drilling activity in the Marcellus Formation in the northern Appalachian Basin has increased, so has the number of alleged incidents of stray natural gas migration to shallow aquifer systems. For this study, more than 2300 gas and water samples were analyzed for molecular composition and stable isotope compositions of methane and ethane. The samples are from Neogene- to Middle Devonian-Age strata in a five-county study area in northeastern Pennsylvania. Samples were collected from the vertical and lateral sections of 234 gas wells during mud gas logging (MGL) programs and 67 private groundwater-supply wells during baseline groundwater-quality testing programs. Evaluation of this geochemical database reveals that microbial, mixed microbial and thermogenic, and thermogenic gases of different thermal maturities occur in some shallow aquifer systems and throughout the stratigraphy above the Marcellus Formation. The gas occurrences predate Marcellus Formation drilling activity. Isotope data reveal that thermogenic gases are predominant in the regional Neogene and Upper Devonian rocks that comprise the potable aquifer system in the upper 305 m (1000 ft) (averAge 13C1 = 43.53; averAge 13C2 = 40.95; averAge DC1 = 232.50) and typically are distinct from gases in the Middle Devonian Marcellus Formation (averAge 13C1 = 32.37; averAge 13C2 = 38.48; averAge DC1 = 162.34 ). Additionally, isotope geochemistry at the site-specific level reveals a complex thermal and migration history with gas mixtures and partial isotope reversals (13C1 13C2) in the units overlying the Marcellus Formation. Identifying a source for stray natural gas requires the synthesis of multiple data types at the site-specific level. Molecular and isotope geochemistry provide evidence of gas origin and secondary processes that may have affected the gases during migration. Such data provide focus for investigations where the potential sources for stray gas include multiple, naturally occurring, and anthropogenic gases.
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A Geochemical Context for Stray Gas Investigations in the Northern Appalachian Basin: Implications of Analyses of Natural Gases from Quaternary-through-Devonian-Age Strata in North-Central Pennsylvania
2013Co-Authors: Fred J. Baldassare, Mark A. Mccaffrey, John A. HarperAbstract:As the pace of drilling activity in the Marcellus Formation in the northern Appalachian 21 Basin has increased, so has the number of alleged incidents of stray natural gas migration to two shallow aquifer systems. For this study, more than 1,900 gas and water samples were analyzed for molecular composition and stable isotope compositions of methane and ethane. The samples are from Quaternary to Middle Devonian-Age strata in a five-county study area in northeastern Pennsylvania. Samples were collected from 181 gas wells during mudgas logging programs and from 67 private water supply wells during baseline groundwater-quality testing programs. Evaluation of this database reveals that microbial, mixed microbial/thermogenic, and thermogenic gases occur in some shallow aquifer systems, and that the gas occurrences pre-date Marcellus Formation drilling activity. Isotope data reveal that thermogenic gases in the regional Quaternary/ Upper Devonian shallow subsurface (averAge δ13 C1 = -42.13 ‰; averAge δDC1 = - 228.26 ‰) typically are distinct from gases in Middle Devonian strata (averAge δ13 C1 = -32.87 ‰; averAge δDC1 = -163.45 ‰). Additionally, gas geochemistry at the site-specific level reveals a complex thermal and migration history with gas mixtures and partial isotope reversals (δ13 C1> δ13 C2) in units above the Marcellus Formation.
Robert P. Wintsch - One of the best experts on this subject based on the ideXlab platform.
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Silurian-Devonian Age and tectonic setting of the Connecticut Valley-Gaspe trough in Vermont based on U-Pb SHRIMP analyses of detrital zircons
American Journal of Science, 2010Co-Authors: Cory K. Mcwilliams, Gregory J. Walsh, Robert P. WintschAbstract:U-Pb SHRIMP Ages of detrital zircons from metasedimentary rocks of the Connecticut Valley-Gaspe trough in Vermont corroborate a Silurian-Devonian Age of deposition for these strata and constrain their provenances. Ages of randomly selected detrital zircons obtained from quartzites within the Waits River and Gile Mountain Formations range from Archean to Devonian with Mesoproterozoic, Neopro- terozoic, Ordovician, and Silurian Age populations suggesting both eastern and western sources of the sediments. The two youngest single-grain detrital zircon Ages from samples collected in the Waits River Formation are 418 ± 7 and 415 ± 2 Ma. The youngest single-grain detrital zircon Age from the eastern part of the Gile Mountain Formation is 411 ± 8. The youngest detrital zircons from the western portion of the Gile Mountain Formation comprise an Age population with a weighted averAge of 409 ± 5 Ma. These ∼409 Ma zircons are likely of volcanic origin, perhaps derived from the Piscataquis magmatic belt to the east. The absence of younger volcanic zircons in the coarser-grained eastern facies of the Gile Mountain Formation suggests the eastern sediments are older and were buried during Piscataquis volcanism and deposition in the west. The shift in protoliths from calcareous silts and muds of the Waits River Formation to quartzo-feldspathic sands of the Gile Mountain Formation implies a change from a continental slope-like depositional environment to a near-shore or terrestrial environment of deposition. This change supports a transition in the nature of the basin from an intercontinental back-arc extensional setting to a foreland basin setting. Maximum depositional Ages of sediments above and below this facies bound- ary constrain the timing of transition in basin style between about 415 and 411 Ma. Given the timing of the approaching Acadian wedge, this shift in basin style likely reflects westward migration of thrust sheets during the Acadian orogeny. The fine-grained nature of the youngest silts, muds and turbidites suggests that sedimentation occurred in increasingly deeper water. The implied basin subsidence was likely caused by lithospheric flexure as the Acadian wedge approached from the east. The timing of this subsidence is constrained to be younger than the youngest zircons at about 409 Ma.
N D Sergeeva - One of the best experts on this subject based on the ideXlab platform.
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a Devonian 2000 km long dolerite dyke swarm belt and associated basalts along the urals novozemelian fold belt part of an east european baltica lip tracing the tuzo superswell
Gff, 2016Co-Authors: V N Puchkov, Richard E Ernst, Michael Hamilton, Ulf Soderlund, N D SergeevaAbstract:AbstractTwo dolerite dyke swarms are recognized along and paralleling the Ural Mountains, Russia. The Uralian swarm is 1400-km long (2300-km long if traced from its inferred plume centre). Further north, the Pay-Khoy swarm can be traced through the Pay-Khoy–Novaya Zemlya fold belt for a distance of c. 250 km (800-km long if traced from its inferred plume centre). An Upper Devonian Age for volcanism associated with the Pay-Khoy swarm is well constrained by isotopic data. A Devonian Age for the Uralian swarm was until now supported mainly by broad geological field relationships between the dykes and host rocks, i.e. dykes locally cut Proterozoic, Ordovician to Devonian sedimentary rocks, but never Carboniferous sequences. Rare isotopic Age determinations also support an Upper Devonian Age for the weakly altered dykes. Herein, a new precise U–Pb baddeleyite Age determination of 377.2 ± 0.9 Ma is reported from a large (>50-m wide) gabbro–dolerite dyke cutting the uppermost Proterozoic in the Middle Urals. Thi...
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A Devonian >2000-km-long dolerite dyke swarm-belt and associated basalts along the Urals-Novozemelian fold-belt: part of an East-European (Baltica) LIP tracing the Tuzo Superswell
GFF, 2016Co-Authors: V N Puchkov, Richard E Ernst, Michael Hamilton, Ulf Soderlund, N D SergeevaAbstract:AbstractTwo dolerite dyke swarms are recognized along and paralleling the Ural Mountains, Russia. The Uralian swarm is 1400-km long (2300-km long if traced from its inferred plume centre). Further north, the Pay-Khoy swarm can be traced through the Pay-Khoy–Novaya Zemlya fold belt for a distance of c. 250 km (800-km long if traced from its inferred plume centre). An Upper Devonian Age for volcanism associated with the Pay-Khoy swarm is well constrained by isotopic data. A Devonian Age for the Uralian swarm was until now supported mainly by broad geological field relationships between the dykes and host rocks, i.e. dykes locally cut Proterozoic, Ordovician to Devonian sedimentary rocks, but never Carboniferous sequences. Rare isotopic Age determinations also support an Upper Devonian Age for the weakly altered dykes. Herein, a new precise U–Pb baddeleyite Age determination of 377.2 ± 0.9 Ma is reported from a large (>50-m wide) gabbro–dolerite dyke cutting the uppermost Proterozoic in the Middle Urals. Thi...
Fred J. Baldassare - One of the best experts on this subject based on the ideXlab platform.
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a geochemical context for stray gas investigations in the northern appalachian basin implications of analyses of natural gases from neogene through Devonian Age strata
AAPG Bulletin, 2014Co-Authors: Fred J. Baldassare, Mark A. Mccaffrey, John A. HarperAbstract:As the pace of drilling activity in the Marcellus Formation in the northern Appalachian Basin has increased, so has the number of alleged incidents of stray natural gas migration to shallow aquifer systems. For this study, more than 2300 gas and water samples were analyzed for molecular composition and stable isotope compositions of methane and ethane. The samples are from Neogene- to Middle Devonian-Age strata in a five-county study area in northeastern Pennsylvania. Samples were collected from the vertical and lateral sections of 234 gas wells during mud gas logging (MGL) programs and 67 private groundwater-supply wells during baseline groundwater-quality testing programs. Evaluation of this geochemical database reveals that microbial, mixed microbial and thermogenic, and thermogenic gases of different thermal maturities occur in some shallow aquifer systems and throughout the stratigraphy above the Marcellus Formation. The gas occurrences predate Marcellus Formation drilling activity. Isotope data reveal that thermogenic gases are predominant in the regional Neogene and Upper Devonian rocks that comprise the potable aquifer system in the upper 305 m (1000 ft) (averAge 13C1 = 43.53; averAge 13C2 = 40.95; averAge DC1 = 232.50) and typically are distinct from gases in the Middle Devonian Marcellus Formation (averAge 13C1 = 32.37; averAge 13C2 = 38.48; averAge DC1 = 162.34 ). Additionally, isotope geochemistry at the site-specific level reveals a complex thermal and migration history with gas mixtures and partial isotope reversals (13C1 13C2) in the units overlying the Marcellus Formation. Identifying a source for stray natural gas requires the synthesis of multiple data types at the site-specific level. Molecular and isotope geochemistry provide evidence of gas origin and secondary processes that may have affected the gases during migration. Such data provide focus for investigations where the potential sources for stray gas include multiple, naturally occurring, and anthropogenic gases.
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A Geochemical Context for Stray Gas Investigations in the Northern Appalachian Basin: Implications of Analyses of Natural Gases from Quaternary-through-Devonian-Age Strata in North-Central Pennsylvania
2013Co-Authors: Fred J. Baldassare, Mark A. Mccaffrey, John A. HarperAbstract:As the pace of drilling activity in the Marcellus Formation in the northern Appalachian 21 Basin has increased, so has the number of alleged incidents of stray natural gas migration to two shallow aquifer systems. For this study, more than 1,900 gas and water samples were analyzed for molecular composition and stable isotope compositions of methane and ethane. The samples are from Quaternary to Middle Devonian-Age strata in a five-county study area in northeastern Pennsylvania. Samples were collected from 181 gas wells during mudgas logging programs and from 67 private water supply wells during baseline groundwater-quality testing programs. Evaluation of this database reveals that microbial, mixed microbial/thermogenic, and thermogenic gases occur in some shallow aquifer systems, and that the gas occurrences pre-date Marcellus Formation drilling activity. Isotope data reveal that thermogenic gases in the regional Quaternary/ Upper Devonian shallow subsurface (averAge δ13 C1 = -42.13 ‰; averAge δDC1 = - 228.26 ‰) typically are distinct from gases in Middle Devonian strata (averAge δ13 C1 = -32.87 ‰; averAge δDC1 = -163.45 ‰). Additionally, gas geochemistry at the site-specific level reveals a complex thermal and migration history with gas mixtures and partial isotope reversals (δ13 C1> δ13 C2) in units above the Marcellus Formation.
Gerard J M Versteegh - One of the best experts on this subject based on the ideXlab platform.
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aliphatic and aromatic biomarkers from gondwanan sediments of late ordovician to early Devonian Age an early terrestrialization approach
Organic Geochemistry, 2011Co-Authors: Mariafernanda Romerosarmiento, Armelle Riboulleau, Marco Vecoli, Gerard J M VersteeghAbstract:Abstract Twenty one core samples of Late Ordovician to Early Devonian Age from sections in southern Tunisia, North African Platform (Gondwana) and containing marine and terrestrial organic matter with microbial input were investigated to link the aliphatic and aromatic hydrocarbon distributions with the terrestrial and marine palynomorph content (e.g. acritarchs, prasinophytes, chitinozoans, cryptospores and trilete spores). In addition to several biomarkers of algal/bacterial origin, long chain n-alkanes that might be derived from land plants, as well as the terrestrial diterpane, norabietane, were found. Several land plant-derived biomarkers, such as retene, cadalene, simonellite, tetrahydroretene and C19 isohexylalkyl naphthalene were observed in the aromatic fractions. While these terrestrial biomarkers could be clearly recognized in the middle Silurian–lower Devonian samples, their presence in the upper Ordovician–lower Silurian sediments is more doubtful, because of much lower relative abundances. The land plant biomarkers show a fairly good correlation with the occurrence and abundance of cryptospores and trilete spores, derived from bryophytes and tracheophytes, which covered the emerged areas around the Ghadamis Basin during the Silurian and Devonian. The early tracheophytes (e.g. Cooksonia, lycophytes and zosterophylls) are therefore suggested as a new terrestrial source for most of the saturated and aromatic biomarkers found in sediments of Middle Silurian to Early Devonian Age.