Geoturism Balearic Islands

A delta is a sedimentary deposit associated with the estuary of a river course. There are many current examples, one of the most outstanding nationally is the Ebro Delta. 

Deltas, when active, are very dynamic and comprise one of main sources of sediment in the sea basins. Their name alludes to the Greek letter, which with its triangular outline reminds us of the morphology of the delta itself. 

During the Lower and Middle Miocene (20-15 Ma, approximately), just before the formation of Eivissa as the island we know today, some deltas were also formed. 

These, in general terms, have different parts: a proximal area (attached to the river course, continental) with coarse-grain sedimentation, and a distal one (far from the river course, marine) with fine-grain sedimentation. 

Near the area of Penyal de s’Àguila, at Es Portitxol, one can observe the proximal part of the delta, composed by conglomerates and gravel. However, at this stop what is shown corresponds to the distal stratigraphic unit and reflect the specific environmental conditions in which they were formed.</p><p><br></p></div>">facies, known as delta front and prodelta. These comprise very well-defined strata of marls (prodelta) with intercalations of sandstones (delta front). The whole set of sediments is under the thrust of the oldest materials of the Keuper stratigraphic unit and reflect the specific environmental conditions in which they were formed.</p><p><br></p></div>">facies of the first stop.

The delta is the substratum on which the richest ecosystems are developed. With the passing of millions of years these can leave fossil evidence. In this case in hand, the typical fossils are not the organisms that inhabit the sea bottom, rather their activity traces, known as trace fossils. Specifically, what we can observe in the tectonic, eustatic or antropical processes</span></p></div>">outcrop are galleries that serve as crustacean dens. This type of trace fossil is known by the technical term Domichnia (from domum, house in Latin).