Combined studies of palynomorph and palynofacies assemblages with micropalaeontological and mineralogical analyses, allow us to state the sedimentary environment and depositional characteristics. This combination of studies provides the framework from which we select the organic elements for assessing transgressive or regressive trends related to highstands acid low-stands of the water or sea level. The selected clues are: miospores and dinocysts diversity and abundance, Pteridophyta spores, aquatic Monocotyledons, Ephedraceae, the multifarious amorphous organic mailer and black woody-coaly debris, vegetal tissues, algae and resinous bodies. Furthermore, the abundance of kaolinite and smectite clay minerals has been taken into account. Three types of deposits are analysed: a marine sequence of Oligocene beds, an upward grading of continental shales into marine marls of the same Oligocene age as the previous sequence, and a continental clay and brown-coal Eocene deposit. The differences between continental/swampy and marine environments are generally differences in abundance of the chosen clue-elements, or more rarely, differences in the presence or absence of an element. In both marine and continental sequences, certain horizons are enriched in Pteridophyta spores as well as in cuticles, tissues and black woody-coaly debris. These assemblages reflect the enhanced influence of continental supply caused by a strong fluvial activity which is related to lowstands of the water level. At this time, the fringe of borderland vegetation was more developed (aquatic or moisture-loving monocotyledons, Ephedraceae in drier places), and smectite occurred in the poorly-drained depressions. On the contrary, water highstands brought a spread of the aquatic domain that mobilized the kaolinite on the continent and enhanced the abundance oi algal tissues and, for example, Palmae pollen. At this time, black debris was less common, but amber-coloured resinous bodies were present and linked with the increase of Pinaceae pollen. Thus, the fluctuation of the water or sea level in a depositional area may show, for example, the position of the maximum flooding surface. In this respect, the proposed clue-elements define tectonic or eustatic sea-level changes by an approach other than that of sequence stratigraphy.