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A complex interplay between distinct geological units is responsible for the unique beauty of this rocky shore. Limestones, marls and clays of the Upper Jurassic through Cretaceous (Albian limestones) are folded and thrust with a geometry implying a NNE-SSW direction of shortening related to diapirism during the global Alpine Orogeny. These are evidences for an important compressive event that occurred prior to the deposition of the Middle Miocene highly fossiliferous sequences of the Lagos-Portimão Formation, thus constraining the Algarve basin main inversion phase.
Layers with macroforaminifera (Orbitulinidae family) are of special interest on Cretaceous paleogeographic and paleoenvironmental reconstructions.
The deformation and emersion of the Mesozoic units led to a first stage of karst development before being overlapped as an angular unconformity by the transgressive sequences of the Lagos-Portimão Formation through a series of marine terrace platforms, the lowermost re-elaborated by present day coastal abrasion. The original geometry of the fossilized paleo-rocky shore is still visible with bioerosion trace fossils produced by several lithophagous organisms contemporary of the early coastal marine deposition stage of the Lagos-Portimão formation.
Highly fossiliferous levels of the Lagos-Portimão formation outcrop as pectinid coquina and shell-in-shell diversified and mineralized mollusk orictocoenoses of shallow high energy facies. These units also emerged and a second karst development stage acted during an estimated 3 Ma time interval upon this Middle Miocene formation. Its correlative unconformity is fossilized by micaceous fine sands (areola facies) and well-rounded quartz pebbles (bichouro) of the Upper Tortonian Cacela Formation.
A last emersion and karst development occurred during the Plio-Quaternary and is still active today which is responsible for the deformation of the upper siliciclastic units inside the present day dissolution sinkholes and dolines.
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