Tidal rhythmites and their implications

Tidal rhythmites are unequivocal evidence of marine conditions in sedimentary basins and can preserve a record of astronomically induced tidal periods. Unlike modern tide and tidal deposits, analysis of ancient tidal rhythmites, however, is not straightforward. This paper highlights the advances made in the tidal rhythmite research in the last decade and reviews the methodologies of extracting lunar orbital periods from ancient tidal rhythmites, the mathematics behind the use of tidalites, and their limitations and uncertainties. We have shown that analysis of ancient tidal rhythmite may help us to estimate the palaeolunar orbital periods in terms of lunar days/month accurately. Determination of absolute Earth–Moon distances and Earthʹs palaeorotational parameters in the distant geological past from tidal rhythmite, however, is ambiguous because of the difficulties in determining the absolute length of the ancient lunar sidereal month.