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Book Chapter

K–T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits

By
F. Martínez-Ruiz
F. Martínez-Ruiz
Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Facultad de Ciencias, Avda. Fuentenueva, s/n. 18002 Granada, Spain (fmruiz@goliat. ugr. es)
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M. Ortega-Huertas
M. Ortega-Huertas
Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva, s/n. 18002 Granada, Spain
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I. Palomo-Delgado
I. Palomo-Delgado
Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva, s/n. 18002 Granada, Spain
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J. Smit
J. Smit
Department of Sedimentary Geology, Vrije Universiteit, 1081 HV Amsterdam, Netherlands
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Published:
January 01, 2001

Abstract

The Cretaceous-Tertiary (K-T) boundary interval recovered by the ODP Leg 171 at Site 1049 (Blake Nose, NW Atlantic) contains a thick (9–17 cm) spherule bed marking the boundary. The spherules are mainly perfect spheres with a lesser proportion of oval spherules. They usually range from 100 to 1000 μm. This bed represent the diagenetically altered impact ejecta from Chicxulub and further supports this structure as the site of the K-T impact. Mineralogical and geochemical investigations indicate that impact-generated glass was altered to smectite. Transmission electron microscopy observations revealed in some spherules that smectite is forming from a Si-rich or Ca-rich material, which could suggest a precursor similar to Haitian glasses. The variable thickness and the presence of some Cretaceous planktonic foraminifera and clasts of Cretaceous chalk suggest reworking of the ejecta material. However, the spherule bed confirms that a large volume of the Chicxulub ejecta material reached the Blake Nose Plateau.

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Contents

Geological Society, London, Special Publications

Western North Atlantic Palaeogene and Cretaceous Palaeoceanography

Dick Kroon
Dick Kroon
University of Edinburgh, UK
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R. D. Norris
R. D. Norris
Woods Hole OI, USA
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A. Klaus
A. Klaus
Ocean Drilling Program, USA
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Geological Society of London
Volume
183
ISBN electronic:
9781862394315
Publication date:
January 01, 2001

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