Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Haynes, J. T. Articles by Kunk, M. J. Search for Related Content GeoRef GeoRef Citation

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)

¹ Department of Mineral Sciences, National Museum of Natural History, MRC-119, Smithsonian Institution, Washington, D.C. 20560
² U.S. Geological Survey, MS-981, National Center, Reston, Virginia 22092

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 microprobe analyses provide a precise geochemical fingerprint of each bed. Millbrig and Kinnekulle biotites contain more FeO* and MnO and less MgO and TiO₂ than do Deicke biotites. Millbrig biotites contain more MgO and less TiO₂ than Kinnekulle biotites, and Kinnekulle biotites contain appreciably more Al₂O₃ than either Deicke or Millbrig biotites. Each of these tephras was unmistakably the product of a gigantic explosive volcanic eruption, but the differences in phenocryst chemistry point to derivation from three compositionally different magma batches.

This article has been cited by other articles:

				S. SHARMA, G. R. DIX, and M. VILLENEUVE Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians Geological Magazine, March 1, 2005; 142(2): 145 - 158. [Abstract] [Full Text] [PDF]

				R. A. Batchelor and R. A. Batchelor Geochemistry of biotite in metabentonites as an age discriminant, indicator of regional magma sources and potential correlating tool Mineralogical Magazine, August 1, 2003; 67(4): 807 - 817. [Abstract] [Full Text] [PDF]

				C.-H. Chen, T. F. Yang, S.-R. Song, Y. Iizuka, and K.-Y. Wei Toba ash layers in the South China Sea: Evidence of contrasting wind directions during eruption ca. 74 ka: Comment and Reply: COMMENT Geology, November 1, 2000; 28(11): 1055 - 1056. [Full Text] [PDF]

				MOHAWKIAN (UPPER ORDOVICIAN) CONODONTS OF EASTERN NORTH AMERICA AND BALTOSCANDIA Journal of Paleontology, November 1, 2000; 74(6): 1122 - 1147.

				W. D. Huff, S. M. Bergstrom, D. R. Kolata, C. A. Cingolani, and R. A. Astini Ordovician K-bentonites in the Argentine Precordillera: relations to Gondwana margin evolution Geological Society, London, Special Publications, January 1, 1998; 142(1): 107 - 126. [Abstract] [PDF]