Mysterious ichnology: The trace fossil record of dumb animals doing some surprisingly smart things on ancient Spanish seafloors

Notícia | 12-03-2014

Cicle de conferències en homenatge a Jordi M. de Gibert (1968-2012)

A càrrec de: Prof. Tony Ekdale (Dpt. Geology and Geophysics, University of Utah, EUA)

Dia: Dimecres 12 de març
Hora: 12:00 h
Lloc: Aula Magna de la Facultat de Geologia

Three case studies of trace fossil (ichnofossils) associations in different regions of Spain illustrate how some very specialized feeding habits of ancient animals may be interpreted, even though the taxonomic identities of those animals are unknown, because the animals are not preserved as body fossils. Some of the types of feeding structures that they produced in the sediment reflect surprisingly “smart” behavior patterns, because the architecture and geometry of their trace fossils are amazingly complex!

In Middle Miocene shallow-marine strata of Murcia, densely branched tunnels of the trace fossil Spongeliomorpha iberica contain distinctive wall scratchings (“bioglyphs”). The bioglyph patterns suggest that both scraping and grasping behaviors were used by the burrowers as they fed upon algal(?) growth on the tunnel walls. In Cretaceous-Eocene turbidite deposits of Guipúzcoa, a very high diversity of deep-sea feeding traces can be documented in the scenic sea cliffs. The tightly meandering trace fossil Scolicia, was a grazing trail that was produced by a mobile, sediment-ingesting, deposit feeder. The geometrically patterned trace fossil Paleodictyon apparently was constructed as an underwater “garden”, where the burrow occupant(s) cultivated microbial growth on the tunnel walls as a source of food. In Late Miocene turbidite deposits of Almería, a wide variety of deep-sea feeding traces can be observed in inland outcrops. These include abundant Paleodictyon and other “gardening” trace fossils, as well as less common Scolicia and other grazing trace fossils. In addition to paleoecology, trace fossil studies such as these examples have important implications for understanding paleoenvironmental conditions, sequence stratigraphy and basin tectonics.