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The origin of the White Beds below the Cretaceous-Tertiary boundary in the Gubbio section, ItalyThis paper examines the origin of the 20-50-cm-thick set of whitish limestone beds found immediately underlying the Cretaceous-Tertiary (K-T) boundary in Umbrian sections. On the basis of isothermal remanent magnetization (IRM) acquisitions and thermal demagnetization experiments, it is argued that the white beds were deposited under the same conditions as the underlying pink beds and that the anomalously low IRM intensities found in the white beds resulted from the reduction of hematite in the originally pink beds followed by the removal of the Fe(2+) ions. The whitening of the beds is ascribed to the consequence of downward infiltration of reducing waters resulting from the large quantity of organic matter produced by the extinctions at the K-T boundary. The white interval below the K-T boundary is thus compatible with the hypothesis of impact-triggered mass extinction.
Document ID
19910037671
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lowrie, W.
(Zuerich Eidgenoessische Technische Hochschule, Zurich, Switzerland)
Alvarez, W.
(Eidgenoessische Technische Hochschule Zurich, Switzerland)
Asaro, F.
(California, University Berkeley, United States)
Date Acquired
August 15, 2013
Publication Date
June 1, 1990
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 98
Issue: 4-Mar
ISSN: 0012-821X
Subject Category
Geophysics
Accession Number
91A22294
Funding Number(s)
CONTRACT_GRANT: NSF EAR-88-16421
Distribution Limits
Public
Copyright
Other

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