Lyell Collection
Journal of the Geological Society
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Weedon, G. P.
Right arrow Articles by Gallois, R. W.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Journal of the Geological Society; 2004; v. 161; issue.4; p. 655-666;
DOI: 10.1144/0016-764903-073
© 2004 Geological Society of London

Original Article

Cyclostratigraphy, orbital tuning and inferred productivity for the type Kimmeridge Clay (Late Jurassic), Southern England

Graham P. Weedon1, Angela L. Coe1 & Ramues W. Gallois2

1 1Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK (e-mail: Graham.Weedon@ntlworld.com)
2 292 Stoke Valley Road, Exeter, Devon EX4 5ER, UK

Three independently measured variables (magnetic susceptibility, photoelectric factor and total gamma-ray) obtained from throughout the type Kimmeridge Clay Fm in Dorset (Southern England) were used to identify regular metre-scale, sedimentary cycles. Spectral analysis demonstrates that for long stratigraphical intervals the cycles are expressed as large-amplitude cycles of 1.87–4.05 m wavelength and smaller-amplitude cycles of around half that wavelength. These cycles are interpreted to record orbital obliquity and precession, respectively. The much larger amplitude of the inferred obliquity cycles compared with the precession cycles may indicate a high-latitude climatic forcing transferred to lower latitudes via sea-level variations. Orbital tuning indicates that the Early Kimmeridgian (sensu anglico) lasted at least 3.6 Ma (95 longer-wavelength cycles) and the Late Kimmeridgian at least 3.9 Ma (103 longer-wavelength cycles). The first detailed productivity estimates for the Kimmeridge Clay Fm, on a cycle-by-cycle calculation, indicate that average productivity of the type Kimmeridge Clay (220 g m–2 a–1) was less than the average productivity on modern continental shelves. The high average organic carbon content of the type Kimmeridge Clay (3.8% total organic carbon) cannot be attributed to high average productivity. However, the average organic carbon content is consistent with low siliciclastic mineral dilution of organic matter and/or elevated preservation linked to reduced bottom-water oxygenation.


Keywords: Kimmeridgian, Dorset, cyclostratigraphy, productivity, mudrock.




This article has been cited by other articles:


Home page
 Geological MagazineHome page
J. C. W. COPE
Correlation problems in the Kimmeridge Clay Formation (Upper Jurassic, UK): lithostratigraphy versus biostratigraphy and chronostratigraphy
Geological Magazine, 2009; 146: 266 - 275.
[Abstract] [Full Text] [PDF]

Home page
 Geological MagazineHome page
M. AURELL and B. BADENAS
Facies and depositional sequence evolution controlled by high-frequency sea-level changes in a shallow-water carbonate ramp (late Kimmeridgian, NE Spain)
Geological Magazine, 2004; 141: 717 - 733.
[Abstract] [Full Text] [PDF]