John N Aleinikoff
John Aleinikoff is a Scientist Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 109
U-Pb zircon age of metafelsite from the Pinney Hollow formation: Implications for the development of the Vermont Appalachians U-Pb zircon age of metafelsite from the Pinney Hollow formation: Implications for the development of the Vermont Appalachians
The Pinney Hollow Formation of central Vermont is part of a rift-clastic to drift-stage sequence of cover rocks deposited on the Laurentian margin during the development of the Iapetan passive margin in Late Proterozoic to Cambrian time. Conventional U-Pb zircon data indicate an age of 571+ or -5 Ma for a metafelsite from the Pinney Hollow Formation. Geochemical data indicate that the...
Authors
Gregory J. Walsh, John Aleinikoff
Distinguishing Grenvillian basement from pre-Taconian cover rocks in the Northern Appalachians Distinguishing Grenvillian basement from pre-Taconian cover rocks in the Northern Appalachians
Distinguishing Grenvillian basement rocks from pre-Taconian cover sequences in the Appalachians is a first-order problem essential for accurate structural interpretations. The Cavendish Formation in southeastern Vermont presents a classic example of this problem. Doll and others (1961) showed the Cavendish Formation as younger than the Middle Proterozoic Mount Holly Complex but older...
Authors
Paul M. Karabinos, John N. Aleinikoff, C. Mark Fanning
Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance
Loess in eastern Colorado covers an estimated 14 000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20–14 ka) and correlates reasonably well with the culmination and...
Authors
D.R. Muhs, J. N. Aleinikoff, Thomas W. Stafford, R. Kihl, J. Been, S. A. Mahan, S. Cowherd
Late Quaternary loess in northeastern Colorado: Part II - Pb isotopic evidence for the variability of loess sources Late Quaternary loess in northeastern Colorado: Part II - Pb isotopic evidence for the variability of loess sources
Loess in eastern Colorado covers an estimated 14 000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20–14 ka) and correlates reasonably well with the culmination and...
Authors
J. N. Aleinikoff, D.R. Muhs, R.R. Sauer, C.M. Fanning
Stratigraphic and structural implications of conodont and detrital zircon U-Pb ages from metamorphic rocks of the Coldfoot terrane, Brooks Range, Alaska Stratigraphic and structural implications of conodont and detrital zircon U-Pb ages from metamorphic rocks of the Coldfoot terrane, Brooks Range, Alaska
New paleontologic and isotopic data from the Emma Creek and Marion Creek schists of the Coldfoot terrane, Arctic Alaska superterrane, central Brooks Range, suggest Devonian and possibly younger ages of deposition for their sedimentary protoliths. Conodonts from marble of the Emma Creek schist, intruded by a roughly 392 Ma orthogneiss, are late Lochkovian (early Early Devonian, between...
Authors
Thomas E. Moore, J. N. Aleinikoff, A. G. Harris
Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia
Uranium-lead dating of zircons from the Montpelier Anorthosite confirms previous interpretations, based on equivocal evidence, that the Goochland terrane in the eastern Piedmont of Virginia contains Grenvillian basement rocks of Middle Proterozoic age. A very few prismatic, elongate, euhedral zircons, which contain 12–29 ppm uranium, are interpreted to be igneous in origin. The vast...
Authors
J. N. Aleinikoff, J. Wright Horton, M. Walters
Science and Products
Filter Total Items: 109
U-Pb zircon age of metafelsite from the Pinney Hollow formation: Implications for the development of the Vermont Appalachians U-Pb zircon age of metafelsite from the Pinney Hollow formation: Implications for the development of the Vermont Appalachians
The Pinney Hollow Formation of central Vermont is part of a rift-clastic to drift-stage sequence of cover rocks deposited on the Laurentian margin during the development of the Iapetan passive margin in Late Proterozoic to Cambrian time. Conventional U-Pb zircon data indicate an age of 571+ or -5 Ma for a metafelsite from the Pinney Hollow Formation. Geochemical data indicate that the...
Authors
Gregory J. Walsh, John Aleinikoff
Distinguishing Grenvillian basement from pre-Taconian cover rocks in the Northern Appalachians Distinguishing Grenvillian basement from pre-Taconian cover rocks in the Northern Appalachians
Distinguishing Grenvillian basement rocks from pre-Taconian cover sequences in the Appalachians is a first-order problem essential for accurate structural interpretations. The Cavendish Formation in southeastern Vermont presents a classic example of this problem. Doll and others (1961) showed the Cavendish Formation as younger than the Middle Proterozoic Mount Holly Complex but older...
Authors
Paul M. Karabinos, John N. Aleinikoff, C. Mark Fanning
Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance
Loess in eastern Colorado covers an estimated 14 000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20–14 ka) and correlates reasonably well with the culmination and...
Authors
D.R. Muhs, J. N. Aleinikoff, Thomas W. Stafford, R. Kihl, J. Been, S. A. Mahan, S. Cowherd
Late Quaternary loess in northeastern Colorado: Part II - Pb isotopic evidence for the variability of loess sources Late Quaternary loess in northeastern Colorado: Part II - Pb isotopic evidence for the variability of loess sources
Loess in eastern Colorado covers an estimated 14 000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20–14 ka) and correlates reasonably well with the culmination and...
Authors
J. N. Aleinikoff, D.R. Muhs, R.R. Sauer, C.M. Fanning
Stratigraphic and structural implications of conodont and detrital zircon U-Pb ages from metamorphic rocks of the Coldfoot terrane, Brooks Range, Alaska Stratigraphic and structural implications of conodont and detrital zircon U-Pb ages from metamorphic rocks of the Coldfoot terrane, Brooks Range, Alaska
New paleontologic and isotopic data from the Emma Creek and Marion Creek schists of the Coldfoot terrane, Arctic Alaska superterrane, central Brooks Range, suggest Devonian and possibly younger ages of deposition for their sedimentary protoliths. Conodonts from marble of the Emma Creek schist, intruded by a roughly 392 Ma orthogneiss, are late Lochkovian (early Early Devonian, between...
Authors
Thomas E. Moore, J. N. Aleinikoff, A. G. Harris
Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia
Uranium-lead dating of zircons from the Montpelier Anorthosite confirms previous interpretations, based on equivocal evidence, that the Goochland terrane in the eastern Piedmont of Virginia contains Grenvillian basement rocks of Middle Proterozoic age. A very few prismatic, elongate, euhedral zircons, which contain 12–29 ppm uranium, are interpreted to be igneous in origin. The vast...
Authors
J. N. Aleinikoff, J. Wright Horton, M. Walters