Sedimentology and ichnology of the Robbedale Formation (Lower Cretaceous), Bornholm, Denmark

An exposure of the Lower Cretaceous Robbedale Formation adjacent to the Rønne Golf Course, Bornholm, has permitted a more detailed study of the trace fossils than has been made hitherto. A lithofacies analysis indicates that the sediments were deposited on the lower to upper shore face in a wave dominated barred coastal environment. The following trace fossils are present: Conichnus conosinus isp. n., Cylindrichnus isp., Ophiomorpha nodosa, Skolithos linearis, Teichichnus rectus, Thalassinoides suevicus forms 1 and 2. These seven trace fossils are contained in nine ichnofabrics. The ichnofabrics are closely related to sedimentary facies and suggest a shallow marine sedimentary environment. The abiotic factors, sediment stability and grain size, probably affected the distribution of ichnofabrics by controlling the occurrence of trace makers and their behaviour. Associated with Ophiomorpha nodosa at one horizon are a series of trace fossils that may be interpreted as fodinichnial structures. They somewhat resemble "ray-holes". The available nomenclature for such structures is discussed and the name Conichnus conosinus isp. n. is proposed.