Tidal depositional systems in the rock record: A review and new insights

Some of the principles of tidal-wave theory and examples of mega-, macro-, meso- and microtidal coasts are reviewed, as well as sedimentary successions showing general tidal signals (tidalites) and thinly-laminated, cyclically stacked tidal strata (tidal rhythmites). Although tidalites are well known for their muddy stratification, some of the most spectacular tidal deposits are the sand-rich, cross stratified successions that accumulated as tidal dunes, compound dunes and tidal bars in deltas, estuaries, shelves and straits. Recent progress has been made on modelling of ancient tidal strata, (1) in relation to sea-level rise and fall, (2) in recognition of the systematic changes occurring within the important fluvial–marine transition zone, (3) in the prediction of ancient tidally influenced deposits using shoreline morphology, shelf width and accommodation to supply ratios, and in (4) generation of palaeo-ocean models and the computation of tidal dynamics in ancient seas and seaways. Recent key insights into ancient tidal strata include the recognition of fluid-mud deposits, the realization of the significance of tidal bars versus tidal dunes, the use of palaeogeographic data for prediction of tidal sediments and the recognition of ancient tidal-strait deposits.