John A. Westgate
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View article: Ibex Hollow Tuff from ca. 12 Ma supereruption, southern Idaho, identified across North America, eastern Pacific Ocean, and Gulf of Mexico
Ibex Hollow Tuff from ca. 12 Ma supereruption, southern Idaho, identified across North America, eastern Pacific Ocean, and Gulf of Mexico Open
The Ibex Hollow Tuff, 12.08 ± 0.03 Ma (40Ar/39Ar), is a widespread tephra layer erupted from the Bruneau-Jarbidge volcanic field of southern Idaho. Tephra from this eruption was deposited across much of western and central North America an…
View article: Detrital glass in a Bering Sea sediment core yields a ca. 160 ka Marine Isotope Stage 6 age for Old Crow tephra
Detrital glass in a Bering Sea sediment core yields a ca. 160 ka Marine Isotope Stage 6 age for Old Crow tephra Open
For decades, the Old Crow tephra has been a prominent stratigraphic marker for the onset of Marine Isotope Stage (MIS) 5e, the last interglaciation, in subarctic northwest North America. However, new zircon U-Pb dates for the tephra sugges…
View article: An integrative geochronological framework for the Pleistocene So'a basin (Flores, Indonesia), and its implications for faunal turnover and hominin arrival
An integrative geochronological framework for the Pleistocene So'a basin (Flores, Indonesia), and its implications for faunal turnover and hominin arrival Open
View article: Characterization of Lower and Middle Pleistocene tephra beds in the southern plains of western Canada
Characterization of Lower and Middle Pleistocene tephra beds in the southern plains of western Canada Open
Wellsch Valley tephra, near Swift Current, southwestern Saskatchewan, and Galt Island tephra, near Medicine Hat, southeastern Alberta, have been referenced in the literature since the 1970s, but little is available on their physical and ch…
View article: Glass fission-track ages, composition, and origin of tephra beds in the Upper Cretaceous Kanguk Formation, Banks Island, Arctic Canada
Glass fission-track ages, composition, and origin of tephra beds in the Upper Cretaceous Kanguk Formation, Banks Island, Arctic Canada Open
More than 50 conspicuous tephra beds occur in the Kanguk Formation on the southwestern coast of Banks Island. Their glass shards are remarkably well preserved and permit comprehensive characterization, offering the potential for reliable, …
View article: The Carpathian obsidians – Contribution to their FT dating and provenance (Zemplín, Slovakia)
The Carpathian obsidians – Contribution to their FT dating and provenance (Zemplín, Slovakia) Open
View article: Tephra glass chemistry provides storage and discharge details of five magma reservoirs which fed the 75 ka Youngest Toba Tuff eruption, northern Sumatra
Tephra glass chemistry provides storage and discharge details of five magma reservoirs which fed the 75 ka Youngest Toba Tuff eruption, northern Sumatra Open
The Youngest Toba Tuff contains five distinct glass populations, identified from Ba, Sr and Y compositions, termed PI (lowest Ba) – PV (highest Ba), representing five compositionally distinct pre‐eruptive magma batches that fed the eruptio…
View article: QUA volume 91 issue 2 Cover and Back matter
QUA volume 91 issue 2 Cover and Back matter Open
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View article: Quaternary tephra from the Valles caldera in the volcanic field of the Jemez Mountains of New Mexico identified in western Canada
Quaternary tephra from the Valles caldera in the volcanic field of the Jemez Mountains of New Mexico identified in western Canada Open
A fine-grained, up to 3-m-thick tephra bed in southwestern Saskatchewan, herein named Duncairn tephra (Dt), is derived from an early Pleistocene eruption in the Jemez Mountains volcanic field of New Mexico, requiring a trajectory of northw…
View article: Middle Eocene CO<sub>2</sub>and climate reconstructed from the sediment fill of a subarctic kimberlite maar
Middle Eocene CO<sub>2</sub>and climate reconstructed from the sediment fill of a subarctic kimberlite maar Open
Eocene paleoclimate reconstructions are rarely accompanied by parallel estimates of CO2 from the same locality, complicating assessment of the equilibrium climate response to elevated CO2. We reconstruct temperature, precipitation, and CO2…
View article: Age and context of the oldest known hominin fossils from Flores
Age and context of the oldest known hominin fossils from Flores Open