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TitleGeochronology and calibration of global Milankovitch cyclicity at the Cenomanian-Turonian boundary
AuthorProkoph, A; Villeneuve, M; Agterberg, F P; Rachold, V
SourceGeology vol. 29, no. 6, 2001 p. 523-526,<0523:gacogm>;2
Alt SeriesGeological Survey of Canada, Contribution Series 2000282
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf
Subjectsgeochemistry; geochronology; marine geology; sedimentology; argon argon dating; argon argon dates; sea water geochemistry; organic carbon; organic geochemistry; transgressions; sedimentation rates
Illustrationsgraphs; bar graphs; tables; formulae
AbstractNew 40Ar/39Ar geochronology and global cyclostratigraphic calibration provide high-resolution insights into the timing of geochemical fluctuations across oceanic anoxic event II (OAE II). Five new 40Ar/39Ar data from a single section in western Canada suggest an age of 96.4 ± 1 Ma for the Cenomanian-Turonian (C-T) boundary. This is ?3 m.y. older than previously dated. Time-series analysis (e.g., wavelet transform) reveals that OAE II was synchronously deposited worldwide over a period of ?320 k.y. The preservation and stationarity of Milankovitch cyclicity in sections across the Atlantic indicates that no major fluctuations in sedimentation rate occur across the OAE II, except for a minor short- term decrease in the rate just before the C-T boundary. A ?13Corg increase of >2‰ took place at the beginning of OAE II over a period of ?110 k.y., and likely represents a period of worldwide excessive organic carbon burial during transgression, leading to a 12C depletion of seawater and sedimentation. This interval was followed by a three-step decrease to pre-OAE II ?13C values.

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