A bed by bed analysis of the Bonarelli Level (late Cenomanian) in the Bottaccione Gorge and the Contessa Valley (Gubbio, Italy, area) reveals ichnofabric variations that follow lithofacies changes. Ichnofabric analysis has been approached in ~60 samples for every section, using thin sections of rocks and wet cut surfaces for three-dimensional observations. The ichnofabric includes five ichnotaxa: Chondrites isp., Planolites isp., Thalassinoides isp., Trichichnus linearis , and Zoophycos isp.; their abundance and preservation fluctuate with the substrate consistency, oxygen content, and productivity. The ichnotaxa are absent in many beds that show primary lamination and were deposited under true anoxic conditions, but it is surprising that they are present in many thin beds inside the Bonarelli interval (10 in Bottaccione and 14 in Contessa). In the underlying and overlying Scaglia Bianca (late Cenomanian) carbonate deposits, the presence of a totally bioturbated background, together with superimposed discrete trace fossils (the same ichnotaxa as in the Bonarelli Level), reveals the absence of anoxic conditions (except for cherty layers), but the presence of minor fluctuations between aerobic and slightly dysaerobic conditions is marked by changes in ichnotaxa abundance.

The Contessa Valley and the Bottaccione Gorge located close to Gubbio (central Italy) include some of the most complete successions of Paleogene sediments known from the Tethyan realm. Owing to the continuous deposition in a pelagic setting, a rather modest tectonic overprint, and the availability of excellent age control through magnetostratigraphy, biostratigraphy, chronostratigraphy, and tephrostratigraphy, and direct radioisotopic dates from interbedded volcaniclastic layers, these sediments have played a prominent role in the establishment of standard Paleogene time scales. We present here a complete and well-preserved Paleogene pelagic composite succession of the Gubbio area that provides the means for a more accurate and precise calibration of the Paleogene time scale. As a necessary step toward the compilation of a more robust database on a wide scale so to improve the magnetostratigraphic, biostratigraphic, and chronostratigraphic framework of the classical Tethyan zonations, enabling regional and supraregional correlations, we have constructed a record of reliable Paleogene planktonic foraminifera, calcareous nannofossil, and dinocyst biohorizons commonly used in tropical to subtropical Cenozoic zonations. In addition, an age model is provided for the Paleogene pelagic composite succession based on magnetostratigraphy, planktonic foraminifera, calcareous nannofossils, and dinocysts that contributes to an integrated chronology for the Paleogene Tethyan sediments from 66 to 23 Ma.

Abstract Extensive outcrops in the Umbria–Marche Basin of central Italy include some of the most complete successions of Palaeogene sediments known from the Tethyan Realm. Owing to the continuous deposition in a pelagic setting, a rather modest tectonic overprint, the availability of excellent age control through magneto-, bio-, chemo- and tephrostratigraphy, and direct radioisotopic dates from interbedded volcaniclastic layers, these sediments have played a prominent role in the establishment of standard Palaeogene time scales. We present here a complete and well-preserved Palaeogene pelagic composite succession of the Umbria–Marche Basin, which provides the means for an accurate and precise calibration of the Palaeogene time scale. As a necessary step towards the compilation of a more robust database on a wide scale so as to improve the magneto-, bio- and chronostratigraphic framework of the classical southern Tethyan zonations, enabling regional and supraregional correlations, we have constructed a record of reliable Palaeogene planktonic foraminifera, calcareous nannofossil and dinocyst biohorizons commonly used in tropical to subtropical Cenozoic zonations. In addition, an age model is provided for the Palaeogene pelagic composite succession based on magnetostratigraphy, planktonic foraminifera and calcareous nannofossils, which contributes to an integrated chronology for the Palaeogene Tethyan sediments from c. 65.5 to 23 Ma. Supplementary material: Tables 1 to 13 which provide further details of the Palaeogene pelagic succession of the Umbria–Marche Basin (central Italy) are available at http://www.geolsoc.org.uk/SUP18539