Comparison of Ancient Tidal Rhythmites (Carboniferous of Kansas and Indiana, USA) with Modern Analogues (the Bay of Mont-Saint-Michel, France)
- B. W. Flemming and
- A. Bartholomä
Published Online: 14 APR 2009
Copyright © 1995 The International Association of Sedimentologists
Tidal Signatures in Modern and Ancient Sediments
How to Cite
Tessier, B., Archer, A. W., Lanier, W. P. and Feldman, H. R. (1995) Comparison of Ancient Tidal Rhythmites (Carboniferous of Kansas and Indiana, USA) with Modern Analogues (the Bay of Mont-Saint-Michel, France), in Tidal Signatures in Modern and Ancient Sediments (eds B. W. Flemming and A. Bartholomä), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304138.ch17
- Published Online: 14 APR 2009
- Published Print: 11 AUG 1995
Print ISBN: 9780865429789
Online ISBN: 9781444304138
- ancient tidal rhythmites with modern analogues - comparison;
- tidal rhythmites, common in mid-continental Carboniferous sequences;
- tidal rhythmites, displaying vertical record of tidal cyclicities;
- estuarine morphology, controlling the tidal dynamics;
- Douglas Group, containing decametre-scale cycles;
- rhythmites, occurring within planar bedding
In the upper intertidal area of the Mont-Saint-Michel Bay estuary, the sediment consists of silty and sandy heterolithic facies which commonly display well-developed neap–spring cycles. Such facies have been termed ‘tidal rhythmites’ because they exhibit rhythmicity directly related to tidal periodicities. The vertically accreted tidal bundles are related to flood-dominant deposition. They constitute a sedimentary record of a single semi-diurnal tidal cycle. The neap—spring cycle is reflected by a vertical evolution in thicknesses of successive ‘tidal bundles’ and types of bedforms. These neap—spring records range from a few cm to one dm in thickness and can be expressed in planar lamination, flaser to wavy bedding, and climbing-ripple bedding.
Tidal rhythmites are common in mid-continental Carboniferous sequences in the US. They are well developed in the interior coal basins. Because such facies lack marine body fossils and contain few trace fossils, they have commonly been interpreted as non-marine. However, analyses of sequential series of laminae thicknesses indicate well-developed periodicities indicative of tidal influences during deposition. Modern analogues for such rhythmites have been described from upper reaches of estuarine systems such as the macrotidal Bay of Mont-Saint-Michel. Comparison of the Carboniferous tidal rhythmites with these modern analogues indicates many similarities, which extend to both physical and biogenic sedimentary structures.
In the modern environments, similar tidal rhythmites are best developed in high intertidal estuarine settings. In the Mont-Saint-Michel Bay, tidal rhythmites are observed within restricted secondary channels of the inner estuarine domain protected from ocean wave reworking and fluvial energies. However, high concentrations of suspended sediment are required to produce these facies. In the Bay of Mont-Saint-Michel, high suspended sediment concentrations are produced by offshore wave dynamics. The physical similarities observed between the supposed Carboniferous and the modern tidal rhythmites suggest that they have been deposited in comparable environments with similar hydrodynamic conditions. This similarity in structures may be used as a tool to reinterpret some of the Carboniferous facies and to specify their palaeo-environmental conditions.