Preliminary study of bioerosion in the deep-water coral Lophelia, Pleistocene, Rhodes, Greece

Samples of Lophelia were taken at two localities in the Lindos Bay Clay (Lower Pleistocene) of the Rhodes Formation on the Dodecanese Island of Rhodes. At a coastal exposure at Vasphi, northeast Rhodes, about 200 fragments of Lophelia were collected in situ from the clay and surface preservation of these is consequently particularly fine. The second collection of material was made at an exposure south of Lardos, about 35 km further south. This material comprised some 800 fragments of Lophelia collected both in situ and loose; preservation quality of the surfaces of these is variable. Both collections derive from single fl at beds of coral fragments. Bioerosion of the corals shows a good diversity, comprising about 18 ichnotaxa, five in open nomenclature, including: Orthogonum lineare, Saccomorpha clava and other microborings (probably exclusively of endolithic fungi), Oichnus isp. (pits and holes of various forms, probably all deriving from foraminifers), dish-shaped etchings possibly produced by the foraminifer Hyrrokkin sarcophaga, Palaeosabella prisca (polychaete worm borings), Caulostrepsis isp. (polychaete borings), probable Maeandropolydora isp. (polychaete borings), Talpina isp. (phoronid borings), Podichnus centrifugalis (attachment scars of brachiopods), Centrichnus eccentricus (attachment scars of anomiid bivalves), Gnathichnus pentax (tooth scratches by regular echinoids), and Entobia ispp. (borings of endolithic sponges). Three small, radiating forms around a millimetre in size are difficult to attribute to particular tracemaking organisms. They are retained in open nomenclature as Semidendrina-form (possibly foraminifera borings), a non-camerate radiating form and a hirsute camerate form. No ctenostome bryozoan borings were observed. Talpina isp. is abundant at Vasphi but scarce at Lardos. Otherwise the relative abundance of the trace fossils is comparable at the two localities. The total amount of bioerosion varies considerably in different parts of the coral skeleton. On the basis of SEM imagery, three categories of bioerosional intensity are introduced: 1, slight bioerosion; 2, medium bioerosion, and 3, heavy bioerosion. The distribution of Gnathichnus pentax and the absence of Radulichnus inopinatus indicates an aphotic environment. The microbioerosional assemblage correlates with the Saccomorpha clava / Orthogonum lineare Ichnocoenosis, which also indicates an aphotic seafloor.