Two remarkable examples of Portuguese Neogene bioeroded rocky shores: new data and synthesis

The study of bioeroded rocky paleoshores applied to the practical resolution of paleontological and geological issues, already showed its usefulness. The study of the geological record of this kind of paleoenvironments in Portugal, with particular interest in Neogene occurrences, has resulted in a better understanding of the geological history of the study areas in the context of the regional tectonics evolution and the main Neogene transgressive phases. Two Neogene bioeroded rocky shores (Foz da Fonte, with new data being presented herein, and Oura), remarkable for both their extension and associated fossil record, have been analysed and the bioerosion ichnoassemblages identified. The bioerosion trace fossils include structures produced by clionaid sponges, polychaete and sipunculid annelids, acrothoracican cirripedia, endolithic bivalves, and echinoids. All the bioerosion structures correspond to the boring activity of endolithic and mobile epibenthic organisms. From an ethological point of view, dwelling structures (domichnia) represented by the ichnotaxa Entobia, Caulostrepsis, Maeandropolydora, Trypanites, Rogerella and Gastrochaenolites are dominant, while those related with a combination of feeding habits such as trapping - food farming and food searching, grichnion-pascichnia (compound trace fossil Ericichnus-Circolites) are the less common. A relatively diverse assemblage of in situbody fossils has also been identified associated with these bioeroded surfaces, mainly made up of oysters, barnacles and colonial corals.