Present address: Department of Earth Sciences, Durham University, South Road, Durham, DH1 3LE England.
Orbitally forced sedimentary rhythms in the stratigraphic record: is there room for tidal forcing?
Article first published online: 13 JUL 2011
© 2011 The Authors. Journal compilation © 2011 International Association of Sedimentologists
Volume 59, Issue 2, pages 379–392, February 2012
How to Cite
DE BOER, P. L. and ALEXANDRE, J. T. (2012), Orbitally forced sedimentary rhythms in the stratigraphic record: is there room for tidal forcing?. Sedimentology, 59: 379–392. doi: 10.1111/j.1365-3091.2011.01255.x
- Issue published online: 17 JAN 2012
- Article first published online: 13 JUL 2011
- Manuscript received 7 August 2009; revision accepted 28 April 2011
- Coastal lowlands;
- lunar nodal cycle;
- Milankovitch cycles;
- peritidal carbonate cycles;
- tidal deposits
The imprint of orbital cycles, which result from the varying eccentricity of the Earth’s orbit and changes in the orientation of its axis, have been recognised throughout the Phanerozoic rock record. Variations in insolation and their effect on climate are generally considered to be the sole transfer mechanism between the orbital variables and cyclic sedimentary successions. Common oceanographic principles, however, show that the ocean tide also responds to variations in the orbital parameters. The ocean tide has not yet been considered to be a valid, additional transfer mechanism for the orbital variations. In geological studies of Milankovitch cycles in sedimentary successions the insolation paradigm offers satisfying explanations, and the role of long-term variations of the ocean tide has not yet been appreciated. Variations in the ocean tide, related to changing eccentricity (at present 0·0165, theoretical maximum 0·0728), affect a variety of oceanographic and sedimentary processes. In addition to the widely accepted paradigm of orbitally forced insolation changes, the tidal transfer of orbital signals may explain certain less well-understood aspects of orbitally induced cycles in the stratigraphic record related to ocean mixing, organic productivity, and tidal processes in shallow seas and deep water. Variations of the ocean tide in relation to the 18·6 year lunar nodal cycle, which has no insolation counterpart by which they may be obscured, indeed show that these relatively small variations can produce significant effects in sedimentary environments that are sensitive to variations in the strength of the ocean tide. In analogy with the 18·6 year lunar nodal cycle, orbital variations of the tide on Milankovitch time scales are likely to have affected sedimentary systems in the past.