This route begins on the promenade at the west end of Santa Marian beach, where the information panel stands. If we look southwards, we will see some grey limestones from the Carboniferous Period which stick out on the relief as a vertical wall. This wall rougly coincides with an important fracture known as “Ribadesella/Ribeseya Fault”, which runs through the inner part of the town and borders the Jurassic rocks that extend from here to the coastal cliffs.
Along this walk we find a rhythmic alternation of thin layers of limestone and dark grey marls bearing plenty of marine fossils (Rodiles Formation). These accumulated in a shallow open sea which covered all Asturias at that time.
This calcareous series is suddenly interrupted by the presence of the first layers of conglomerates, sandstones and reddish lutites of fluvial origin (Vega Formation). Intercalations of calcareous fossil soils (“caliches”) bearing vertical root traces typical of a semiarid climate, and grey marls and limestones of lacustrine origin, are occasionally presents.
The net erosive contact between this calcareous marine succession and the overlying continental sequence resulted in a sudden elevation of the sea floor, which emerged due to the tectonic strain: this gave rise to a lack of sedimentation and erosion which constitutes a “stratigraphic gap”.
As we approach the end of the promenade, we come to new alternation of greyisch marls and limestones with some interbedded sandstones on the lower part (Tereñes Formation), which at that time represented a low coastal area, very rich in muds.
Such a succession, which exteds westwards along the cliff, comprises different layers rich in minute bivalves (“coquinas”) together with desiccation cracks and frequent dinosaur footprints. The latter occur on the surface of the strata either as roughly rounded depressions (quadrupedal dinosaur tracks) or as three-toed imprints (bipedal dinosaur tracks).
On the way down to the cliff from the end of the promenade we can observe some of these footprints. From this point, about 150 m further west along the base of the cliff lies a large slab of sandy limestone (about 80º seaward-inclined) which shows diffuse ripple marks due to the wave action at the time. Several footprints of quadrupedal dinosaurs (sauropods) can be discerned on this slab.