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Composition of biotite phenocrysts in Ordovician tephras casts doubt on the proposed trans-Atlantic correlation of the Millbrig K-bentonite (United States) and the Kinnekulle K-bentonite (Sweden) Composition of biotite phenocrysts in Ordovician tephras casts doubt on the proposed trans-Atlantic correlation of the Millbrig K-bentonite (United States) and the Kinnekulle K-bentonite (Sweden)

Biotite phenocryst compositions in three thick, widespread Ordovician K-bentonites, the Deicke and Millbrig from Big Ridge, Alabama, and the Kinnekulle from Mossen, Västergötland, Sweden, fall into three distinct groups, and so the proposed intercontinental correlation of the Millbrig and the Kinnekulle is suspect. Because the biotites are nearly pristine compositionally, electron...
Authors
John T. Haynes, W.G. Melson, Michael J. Kunk

An 40Ar/39Ar thermochronology of the Ofoten‐Troms region: Implications for terrane amalgamation and extensional collapse of the northern Scandinavian Caledonides An 40Ar/39Ar thermochronology of the Ofoten‐Troms region: Implications for terrane amalgamation and extensional collapse of the northern Scandinavian Caledonides

Fifteen 40Ar/39Ar cooling ages are reported for metamorphic hornblende and muscovite from far traveled terranes constituting the Ofoten nappe stack of northern Norway. Eight cooling ages on hornblende range from 425 to 394 Ma and seven muscovite ages, from the same or nearby outcrops as the hornblendes, range from 400 to 373 Ma. These data are compared with 40Ar/39Ar ages from over a...
Authors
Janet E. Coker, Mark G. Steltenpohl, A. Andersen, Michael J. Kunk

Age of the Cenomanian-Turonian boundary in the Western Interior of the United States Age of the Cenomanian-Turonian boundary in the Western Interior of the United States

High precision 40Ar/39Ar laser-microprobe ages of individual sanidines,40Ar/39Ar plateau age spectra on bulk sanidine concentrates, U-Pb zircon ages, and zircon and apatite fission-track ages from three bentonites bracketing the Cenomanian-Turonian boundary in the Western Interior of the United States suggest an age for the boundary of 93.1 ± 0.3 (2σ. The lowermost bentonite comes from...
Authors
B. J. Kowallis, Eric H. Christiansen, Alan L. Deino, Michael J. Kunk, L. Heaman

Geology of the Waterford quadrangle, Virginia and Maryland, and the Virginia part of the Point of Rocks quadrangle Geology of the Waterford quadrangle, Virginia and Maryland, and the Virginia part of the Point of Rocks quadrangle

The bedrock geology of the Waterford quadrangle and of the Virginia part of the Point of Rocks quadrangle consists of a portion of the Middle Proterozoic basement core and its cover sequence on the eastern limb of the Blue Ridge anticlinorium and the adjacent early Mesozoic Culpeper basin. The three major rock associations in this area are: 1) Middle Proterozoic gneisses intruded by late
Authors
William C. Burton, A.J. Froelich, J. S. Pomeroy, K. Y. Lee

Age and diagenesis of the upper Floridan Aquifer and the intermediate aquifer system in southwestern Florida Age and diagenesis of the upper Floridan Aquifer and the intermediate aquifer system in southwestern Florida

No abstract available.
Authors
Lucy McCartan, S.D. Weedman, G.L. Wingard, Lucy E. Edwards, P. J. Sugarman, M.D. Feigenson, M. L. Buursink, J.C. Libarkin

Sedimentary patterns across the Paleocene-Eocene boundary in the Atlantic and Gulf Coastal Plains of the United States Sedimentary patterns across the Paleocene-Eocene boundary in the Atlantic and Gulf Coastal Plains of the United States

Fossiliferous clay and sand belonging to calcareous nannofossil Zones NP 9 (latest Paleocene) and NP 10 (earliest Eocene) are widespread in the US Gulf and Atlantic Coastal Plains. Although the thickness of Zone NP 9-NP 10 strata is several times greater in the eastern Gulf Coastal Plain than in the Atlantic Coastal Plain, the hiatus that usually is present between these two zones in...
Authors
Thomas G. Gibson, Laurel M. Bybell
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