--> Abstract: Stratigraphic Significance of the <I>Entobia</I> Ichnofacies in Rocky Shore Paleoenvironments, Pliocene, NW Mediterranean, by J. M. De Gibert, J. Martinell, and R. Domenech; #90937 (1998)

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Abstract: Stratigraphic Significance of the Entobia Ichnofacies in Rocky Shore Paleoenvironments, Pliocene, NW Mediterranean

GIBERT, JORDI M. DE, University of Utah; JORDI MARTINELL, Universitat de Barcelona; ROSA DOMENECH, Universitat de Barcelona

Assemblages of bioerosion trace fossils corresponding to the Entobia ichnofacies in rocky shore paleoenvironments are very common in Pliocene marginal marine basins along the northwestern Mediterranean coast in eastern Spain and southern France. The boring ichnotaxa are dominated by Gastrochenolites and Entobia. Other common bioerosion trace fossils include Maeandropolydora, Caulostrepsis, Trypanites, Circolites and Iranema.

All these occurrences of fossil rocky shores correspond to the same transgressive event, which took place in the Lower Zanclean (Lower Pliocene). This transgression was a regional event in the Mediterranean, which took place after the reopening of the conexion between the Mediterranean Sea and the Atlantic Ocean, which had been closed during the “Messinian crisis” in the Upper Miocene. Hence, these rocky shores are correlatable along a single stratigraphic surface with a wide geographic distribution that probably extends to the eastern Mediterranean. This surface constitutes a very important stratigraphic sequence boundary in the stratigraphy in the area.

The distribution of the borings in these fossil rocky shores directly relates to the position of sea level during the highstands that mark maximum transgression. The sudden disappearance of borings at a particular height, sometimes associated with an erosional notch or a vertical zonation of the trace fossils, is a very good indicator of the highstand position of sea level. In some cases, this position differs significantly from that which would have been inferred from the transition between marine and continental sediments during the sedimentary filling of the basins.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah