The Dur At Talah sequence outcrops in the Abu Tumayam Trough, in the southern part of the Sirt Basin (Libya). This formation consists of two units, the New Idam Unit at the base and the Sarir Unit at the top. This stratigraphic succession highlights a regressive trend attributed to the upper Eocene. Sedimentological investigations based on lithofacies and ichnofacies suggest that the depositional environments were mainly dominated by a tidal dynamic in the New Idam Unit. Several palaeoenvironments have been defined in this unit: The basal part is built up of an intertidal to supratidal flat system associated with oyster patches. The medium part is characterized by an estuarine channels belt. The upper part exposes typical facies of tidal delta plain and a prograding bar system (mouth-bars). The extremely good preservation of sedimentary structures and sequences allows investigation of the recording of tidal cycles at various scales of time, from the elementary tidal cycle to the solstitial cycle. A comparison with modern Mont-Saint-Michel Bay (France) deposits is proposed to validate facies and palaeoenvironment interpretations in the New Idam Unit. Tidal overprint in the New Idam Unit is expressed through tidal rhythmites composed of horizontal laminations, ripples (flaser, wavy or lenticular) as well as climbing ripples. The elementary recording is made of a mud-sand couplet corresponding to one tide event (slack and flood/ebb). The next scale of recording corresponds to the semi-lunar neap-spring cycle (fortnightly) up to, occasionally, the lunar cycle. Finally, a higher wavelength cycle is recognized corresponding to semi-annual cyclicity. All these cycles are identified in large-scale sedimentary bodies attributed to tidal channels and are best expressed within IHS. The superimposition of the different tidal cycles controls the heterolithic nature of the channel infill. In addition, the tidal rhythmites constitute an accurate chronometer to estimate the duration of tidal channel migration and infilling. This estimation is possible due to the very good preservation of the rhythmites and because of the scarcity of internal erosions within the channel infill.