Trace fossils and their palaeoecological significance in Lower Cretaceous lacustrine conservation deposits, El Montsec, Spain

Abstract

La Pedrera and La Cabrúa at El Montsec, Spain, are two Lower Cretaceous lacustrine conservation deposits (Konservat-Lagerstätten) that have provided a rich, diverse, and well-preserved faunal and floral fossil record. Although the lithographic limestones where the body fossils are found are finely laminated and essentially undisturbed by bioturbation, epigenic trace fossils occur on the surface of certain laminae. Trace fossils at La Pedrera include the fish trail Undichna britannica and the arthropod trackway Hamipes didactylus, while the ichnospecies found at La Cabrúa are Steinsfjordichnus brutoni, Gordia arcuata, Cochlichnus anguineus and Undichna britannica, all but the last corresponding to the activity of small invertebrates. The trace fossil occurrences record short-term events in a lake bottom that did not support any benthic life for most of its history. Differences in the trace fossil assemblages for the two localities agree with sedimentological data in attributing a more distal position for La Pedrera.