Fossil brachiopods from the Roman site on Mogador Island (Essaouira, Morocco): Implications for past exchange of products

Abstract

Archaeological excavations on Mogador Island (Essaouira, Morocco) in 2009 yielded two fossil marine brachiopods found in a refuse layer with Roman finds dated from the first to third century AD (pottery, glass, metal). These fossils originated from marine sediments of the Early Cretaceous age (a geological epoch, about 145–100 million years ago). Four more brachiopods of the same species had previously been found in the 1960s within a Roman building. As the island of Mogador consists entirely of geologically young (about 2 million-year-old) Pleistocene dunes, the provenance of the brachiopods is not of local origin. Geological strata of Cretaceous age are unknown from Mogador. In order to record the source area of the well-preserved brachiopods, the material has been studied in detail. Based on their external morphology and internal structures revealed by serial sectioning, the brachiopods under discussion were identified as Lamellaerhynchia rostriformis. Marine Early Cretaceous sediments containing abundant specimens of this species crop out in the area between Agadir and Essaouira and further to the east. The two fossil brachiopods discussed here most likely came from this area ca. 50 km east-southeast of Mogador. The source rocks for the specimens under discussion can be assigned to the Hauterivian geological period (132–129 million years ago) of the Early Cretaceous, according to the local mass occurrence of L. rostriformis on mainland Morocco. Based on the archaeological evidence associated with the brachiopod fossils we discuss possible modes and reasons for their translocation. We see clear evidence for a purposeful collection and storage of these fossils.