Late Miocene deep-sea trace fossil associations in the Vera Basin, Almería, Southeastern Spain

Abstract

The Vera Basin in southeastern Spain was a small, tectonically active depocenter throughout the Miocene. In the early Messinian, approximately 7.2 to 6.0 million years ago, the basin received hemipelagic marl deposits that were punctuated by turbidite events. Soles of thin, turbidite sand beds preserve an abundance of pre-depositional graphoglyptid (agrichnial) burrows that represent diverse deep-sea ichnocoenoses, including Paleodictyon, Urohelminthoida and Helminthorhaphe. Post-depositional feeding burrows, including Ophiomorpha (created by crustaceans) and Scolicia (created by echinoids) occur sparsely in some turbidite beds, but they are far out-numbered by the pre-depositional agrichnial burrows. This diverse trace fossil association occurred in a small, short-lived, coastal basin that apparently never got more than a few hundred meters deep. As the basin opened up and flooded in the Late Miocene, the sea floor was colonized rapidly by benthic organisms of uncertain biological affinity, who created a wide variety of anastomosing and meandering tunnels, in which a nourishing food supply (probably bacteria or fungi) apparently grew on mucus-lined walls