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)
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Abstract
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.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | 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) |
| Series title | Geology |
| DOI | 10.1130/0091-7613(1995)023<0847:COBPIO>2.3.CO;2 |
| Volume | 23 |
| Issue | 9 |
| Year Published | 1995 |
| Language | English |
| Publisher | GSA |
| Contributing office(s) | Eastern Geology and Paleoclimate Science Center |
| Description | 4 p. |
| First page | 847 |
| Last page | 850 |
| Country | United States, Sweden |
| State | Alabama |
| Other Geospatial | Big Ridge, Västergötland |
| Google Analytic Metrics | Metrics page |