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40Ar 39Ar age constraints on neogene sedimentary beds, Upper Ramparts, half-way Pillar and Canyon village sites, Porcupine river, east-central Alaska 40Ar 39Ar age constraints on neogene sedimentary beds, Upper Ramparts, half-way Pillar and Canyon village sites, Porcupine river, east-central Alaska

40Ar/39Ar ages of volcanic rocks are used to provide numerical constraints on the age of middle and upper Miocene sedimentary strata collected along the Porcupine River. Intercalated sedimentary rocks north of latitude 67°10′N in the Porcupine terrane of east-central Alaska contain a rich record of plant fossils. The fossils are valuable indicators of this interior region's paleoclimate...
Authors
Michael J. Kunk, H. Rieck, T. D. Fouch, L. David Carter

The Pennsylvanian Fire Clay tonstein of the Appalachian basin—Its distribution, biostratigraphy, and mineralogy The Pennsylvanian Fire Clay tonstein of the Appalachian basin—Its distribution, biostratigraphy, and mineralogy

The Middle Pennsylvanian Fire Clay tonstein, mostly kaolinite and minor accessory minerals, is an altered and lithified volcanic ash preserved as a thin, isochronous layer associated with the Fire Clay coal bed. Seven samples of the tonstein, taken along a 300-km traverse of the central Appalachian basin, contain cogenetic phenocrysts and trapped silicate-melt inclusions of a rhyolitic...
Authors
C. L. Rice, Harvey E. Belkin, T.W. Henry, R. E. Zartman, Michael J. Kunk

Paleogene stratigraphy of the Solomons Island, Maryland, corehole Paleogene stratigraphy of the Solomons Island, Maryland, corehole

The Solomons Island corehole was drilled in the hope of obtaining a continuous and more nearly complete section of upper Paleocene and lower Eocene strata than are found in the discontinuous and fragmentary sections in the outcrop belt to the west. Consultation with Harry Hansen (Maryland Geological Survey) on possible drilling sites that were within the limits of our equipment and...
Authors
Thomas G. Gibson, Laurel M. Bybell

The Manson Impact Structure: 40Ar/39Ar age and its distal impact ejecta in the Pierre Shale in southeastern South Dakota The Manson Impact Structure: 40Ar/39Ar age and its distal impact ejecta in the Pierre Shale in southeastern South Dakota

The 40Ar/39Ar ages of a sanidine clast from a melt-matrix breccia of the Manson, Iowa, impact structure (MIS) indicate that the MIS formed 73.8 ± 0.3 million years ago (Ma) and is not coincident with the Cretaceous-Tertiary boundary (64.43 ± 0.05 Ma). The MIS sanidine is 9 million years older than 40Ar/39Ar age spectra of MIS shock-metamorphosed microcline and melt-matrix breccia...
Authors
G. A. Izett, W. A. Cobban, J. Obradovich, Michael J. Kunk
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