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<\/p>\nEntobia is a well-known ichnofacies typical for nearshore environments, differentiated from\u00a0the Gnatichnus ichnofacies as being related to more stable conditions in high-energy\u00a0settings and longer times of exposure of the bottoms. Surroundings of the city of Alicante\u00a0(Villafranqueza section, SE Spain), boring structures related to the Entobia ichnofacies were\u00a0observed on an Eocene rockground colonized after a Miocene marine ingression. Reefrelated\u00a0facies are present as coral colonies developed after the transgression and show\u00a0evidence of bioerosive activity. The relationship existing between the growing coral colony\u00a0and boring organisms is addressed in order to elucidate ecological interactions and\u00a0palaeoenvironmental conditions. The studied section is characterized by a very evident\u00a0angular unconformity dividing the underlying Eocene sandy turbiditic beds from the overlying\u00a0Miocene coastal limestones. The Entobia ichnofacies is developed on a variety of\u00a0substrates, represented by the Eocene rockground, resedimented lithoclasts, different\u00a0bioclasts (mainly thick shelled bivalves and gastropods) and coral bioconstructions. Boring\u00a0structures are mainly represented by Gastrochaenolites, Entobia (usually preserved as\u00a0internal mould) and, more rarely, Trypanites. Differences in the relative abundance of the\u00a0three ichnotaxa were observed according to the substrate: i) on the rockground,\u00a0Gastrochaenolites and Trypanites are the most abundant ichnotaxa, being\u00a0Gastrochaenolites represented by different ichnospecies; ii) the three ichnotaxa are present\u00a0in litho- and bio-clasts; iii) in corals, almost exclusively Gastrochaenolites torpedo is found.\u00a0On the rockground, deep penetrating borings as Gastrochaenolites are differently\u00a0preserved, being present complete forms together with partially eroded ones on the same\u00a0surface. This would suggest that colonization occurred over long times, due to prolonged\u00a0exposure of the bottoms. Together with possible ecological restrictions, a preservation bias\u00a0induced by such a prolonged exposure must be considered in order to justify the relative\u00a0abundance of the deep structures typical for the Entobia ichnofacies with respect to the\u00a0shallow-tiered ones. Where Gastrochaenolites is associated to corals, bivalves were found\u00a0inside the bioerosion structures being mainly represented by Lithophaga sp.. In this sense,\u00a0a bioerosive activity specialism is detected, since Gastrochaenolites is extremely more\u00a0abundant in the bioconstructions produced by the coral Tarbellastrea than in those where\u00a0other types of corals are present (e.g. Porites and Siderastraea), thus suggesting some kind\u00a0of ecological interplay. Moreover, the study of the geometrical and morphological\u00a0relationship between Tarbellastrea and Gastrochaenolites shows that, in part of the\u00a0observed specimens, the coral was growing all around the lithophagid borehole. This would\u00a0suggest that corals and bivalves developed at the same time and that the shelly colonization\u00a0and the progress of the host patch reef did not occur in different successive phases.<\/p>\n
Cite as: Giannetti, A., Falces-Delgado, S., and Baeza-Carratal\u00e1, J. F. \u00a0(2019):\u00a0Interaction of boring organisms with corals. Entobia ichnofacies\u00a0development in a transgressive nearshore scenario. 34th IAS International Meeting of Sedimentology, Rome 10-13 September 2019. \u201cSedimentology to face societal challenges on risk, resources and record of the past. \u00a0Sesion 8.A-660.<\/p>\n
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The Villafranqueza unconformity in the logo of the Alicante University Departament of Earth Science and Environment.<\/p>\n","protected":false},"excerpt":{"rendered":"
Entobia is a well-known ichnofacies typical for nearshore environments, differentiated from\u00a0the Gnatichnus ichnofacies as being related to more stable conditions in high-energy\u00a0settings and longer times of exposure of the bottoms. Surroundings of the city of Alicante\u00a0(Villafranqueza section, SE Spain), boring … Continue reading