Orbitally forced Lofer cycles in the Dachstein Limestone of the Julian Alps (northeastern Italy)
- 1Institute of Geology, Department of Earth Sciences, Swiss Federal Institute of Technology (ETH) Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland
- 2Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
Abstract
Lofer cyclothems of the Upper Triassic Dachstein Limestone of the Julian Alps (northeastern Italy) are the focus of a new sedimentological-cyclostratigraphic study. A 112-cycle-long field section reveals that the meter-scale basic cycle shallows upward, from subtidal megalodont-bearing subfacies to intertidal laminites, capped by a paleosol subfacies. Time-series analysis of a correlative grayscale scan of a high-resolution field photograph shows that a 166-m-thick succession of Lofer cycles has time-frequency characteristics consistent with Earth's precession index, suggesting that the Lofer cycles were generated by eustatic sea-level oscillations that were forced by Milankovitch cycles.
Footnotes
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↵*E-mails: andrea.cozzi{at}erdw.ethz.ch; hinnov{at}jhu.edu; hardie{at}jhu.edu
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↵GSA Data Repository item 2005157, Grayscale scan data and outcrop picture, is available online at www.geosociety.org/pubs/ft2005.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA.
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- Accepted 13 June 2005.
- Received 24 February 2005.
- Revision received 9 June 2005.
- Geological Society of America
