ABSTRACT The Bottaccione Gorge at Gubbio, in central Italy, has been an important source of information about Cretaceous and Paleogene Earth history. At the much younger end of the historical continuum, it is also important for understanding the early history of Gubbio itself, for which the only written, although somewhat ambiguous, evidence comes from the Tavole eugubine, the unique bronze tablets which are a kind of Rosetta Stone for the Umbrian language. The role of the Bottaccione Gorge is debated in the history of Gubbio. The road through the gorge, crossing the Monti di Gubbio, is an important element for explaining the location of the city. One of the first settlements (late Bronze Age) is recognized from archaeological evidence at the top of a morphological fault scarp on the slope of Monte Ingino. In the Iron Age, the city described in the Tavole eugubine developed, in which Okri (fortress), Tota (city), and three sacred gates are mentioned. The locations of Okri , Tota , and the gates are still under study. According to the most likely hypothesis, Tota would have developed in the plain, on the right bank of the Torrente Camignano, while the initial settlement would have been transformed into Okri , to which the sacred gates would belong. Another gate may have been placed at the entrance to the Bottaccione Gorge. When the Eugubini (the people of Gubbio) built the new, post-Roman Gubbio in the twelfth century, they still identified, as the most suitable place for a fortified city, the location above the scarp on the slope of Monte Ingino, and they built two new gates at its lateral ends. The city was likely equipped with a third gate that faced the Bottaccione Gorge. In the thirteenth century, the Bottaccione Aqueduct was built to bring water to the highest point of Gubbio. Thus, two waterways—one natural (Torrente Camignano) and the other artificial—still branch off from Bottaccione to reach Gubbio at two different points that determine the lowest and highest levels of the city.

The Bottaccione Gorge at Gubbio, Italy, a source of many discoveries in Earth history, was first recognized as an outstanding geological section by Guido Bonarelli (1871–1951). Bonarelli is remembered today mainly for the meter-thick Bonarelli Level, the local manifestation of oceanic anoxic event 2 (OAE 2), which he first recognized and described. Setting aside Bonarelli’s long and distinguished career as a petroleum geologist in Borneo and Argentina, this paper concentrates on his role in the long and difficult effort to date the Scaglia rossa pelagic limestone of the Bottaccione Gorge and the surrounding Umbria-Marche Apennines. Old photographs show a barren Bottaccione Gorge a century ago; Bonarelli apparently had much better outcrops than we do today, after reforestation shortly before the middle of the twentieth century. In the absence of macrofossils, and with the inability to extract isolated foraminifera from these hard limestones, the Scaglia was dated indirectly in the late nineteenth century, and believed to be entirely of Cretaceous age, implying errors as great as 40 m.y. We can now understand why this dating seemed satisfactory at the time, because it did not conflict with Charles Lyell’s view that there should be a huge hiatus corresponding to a major faunal overturn like the Cretaceous-Paleogene (K-Pg) boundary, and because thrust faulting that contradicted it had not yet been discovered. The K-Pg boundary was correctly placed within the Scaglia in 1936 when Otto Renz identified the foraminifera in thin section. Renz wrote with pleasure of a field trip with Bonarelli, who later presented Renz’s new dating to the Società Geologica Italiana on a 1940 field trip to Gubbio. These two are the predecessors of all the geologists who have worked in the Bottaccione Gorge since the Second World War.

ABSTRACT At present, the Global Stratotype Section and Point (GSSP) for the base of the Bartonian remains the only GSSP of the Paleogene System to be defined by the International Subcommission on Paleogene Stratigraphy (ISPS) and the International Commission on Stratigraphy (ICS). Here, we present the results of an integrated, high-resolution study of calcareous plankton and benthic foraminifera biostratigraphy and a detailed magneto-, chemo-, and cyclostratigraphic analyses carried out through the upper Lutetian to the upper Priabonian pelagic sediments of the Bottaccione Gorge section near Gubbio, central Italy, to check its stratigraphic completeness and constrain in time the optimal interval for defining and positioning the GSSP for the base of the Bartonian Stage. The high-resolution and solid integrated stratigraphic framework established at Bottaccione confirmed the completeness of the section, which meets the ICS recommendations for a potential designation as a GSSP for the base of the Bartonian Stage. Thus, the Bottaccione section was compared with the parastratotype section of the Bartonian in its type area, Alum Bay, UK. On this basis, two reliable criteria for defining and positioning the Bartonian GSSP at Bottaccione are provided: (1) the base of magnetic polarity chronozone C18r as the primary correlation criterion and (2) the base of the calcareous nannofossil Dictyococcites bisectus , which defines the CNE14/CNE15 zonal boundary as a secondary correlation criterion.

ABSTRACT The complete and well-studied pelagic carbonate successions from the Umbria-Marche basin (Italy) permit the study of the event-rich stratigraphic interval around the Cretaceous-Paleogene boundary (e.g., Deccan volcanism, boundary impact, Paleocene recovery, and climate). To test the robustness of various proxy records (bulk carbonate δ 13 C, δ 18 O, 87 Sr/ 86 Sr, and Ca, Fe, Sr, and Mn concentrations) inside the Umbria-Marche basin, several stratigraphically equivalent sections were investigated (Bottaccione Gorge, Contessa Highway, Fornaci East quarry, Frontale, Morello, and Petriccio core). Besides the classical Gubbio sections of Bottaccione and Contessa, the new Morello section is put forward as an alternative location for this stratigraphic interval because it is less altered by burial diagenesis. Elemental profiles (Ca, Fe, Sr, Mn) acquired by handheld X-ray fluorescence (pXRF) efficiently provide regional chemostratigraphic and paleoenvironmental information. The Deccan volcanism, the Cretaceous-Paleogene boundary, the characteristic pattern of the Sr/Ca profile across the boundary driven by the extinction and recovery of coccolithophores, and the Dan-C2 hyperthermal event are examples of such recorded paleoenvironmental events. Moreover, cyclostratigraphic analyses of proxies of detrital input (magnetic susceptibility and Fe concentrations) show the imprint in the sedimentary record of a 2.4 m.y. eccentricity minimum around 66.45–66.25 Ma, and suggest that the occurrence of the Dan-C2 hyperthermal event was astronomically paced.

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.

ABSTRACT The Cretaceous and Paleogene pelagic limestone and marl formations of the Umbria-Marche Apennines of north-central Italy have proven to be exceptional recorders of the history of Earth and of life on Earth, and they have been the subject of numerous geological and paleontological studies over the last several decades. Founded a quarter century ago, in 1992, the Geological Observatory of Coldigioco is a research and teaching center focused on these exceptional rocks. This chapter is a historical introduction that briefly reviews the highlights of the lithologic, biostratigraphic, sedimentologic, magnetostratigraphic, impact-stratigraphic, geochemical, geochronological, time-scale, and cyclostratigraphical research done on the Umbria-Marche stratigraphic sequence, much of it facilitated by the Geological Observatory of Coldigioco. This review covers work up to the Coldigioco 25th anniversary Penrose conference in September 2017; it does not treat work presented at that conference or done since then. A remarkable irony is that a century ago, the Umbria-Marche Cretaceous–Paleogene sequence was so difficult to date that early work contained an error of ~35 m.y., but now there is a reasonable hope that this entire section may eventually be dated to an accuracy and precision of ~10,000 yr. This review begins with an homage to the little medieval city of Gubbio, its wild Festa dei Ceri, and its Bottaccione Gorge, where much of the research described here has been done. The review ends with three points of perspective. The first is the notion that sometimes geology can be done by looking up at the sky, and astronomy can be done by looking down at Earth, with much of the Coldigioco-based research being of this latter kind. The second is the observation that geology and paleontology are contributing far more new information to Big History—to our integrated knowledge of the past—than any other historical field in the humanities or sciences. The third is that three of the major scientific revolutions of geology in the twentieth century have direct connections to the Umbria-Marche stratigraphic sequence—the turbidite revolution, the development of plate tectonics, and the downfall of strict uniformitarianism.

We studied a high-resolution multiproxy data set, including magnetic susceptibility (MS), CaCO 3 content, and stable isotopes (δ 18 O and δ 13 C), from the stratigraphic interval covering the uppermost Maastrichtian and the lower Danian, represented by the pelagic limestones of the Scaglia Rossa Formation continuously exposed in the classic sections of the Bottaccione Gorge and the Contessa Highway near Gubbio, Italy. Variations in all the proxy series are periodic and reflect astronomically forced climate changes (i.e., Milankovitch cycles). In particular, the MS proxy reflects variations in the terrigenous dust input in this pelagic, deep-marine environment. We speculate that the dust is mainly eolian in origin and that the availability and transport of dust are influenced by variations in the vegetation cover on the Maastrichtian-Paleocene African or Asian zone, which were respectively located at tropical to subtropical latitudes to the south or far to the east of the western Tethyan Umbria-Marche Basin, and were characterized by monsoonal circulation. The dynamics of monsoonal circulation are known to be strongly dependent on precession-driven and obliquity-driven changes in insolation. We propose that a threshold mechanism in the vegetation coverage may explain eccentricity-related periodicities in the terrigenous eolian dust input. Other mechanisms, both oceanic and terrestrial, that depend on the precession amplitude modulated by eccentricity, can be evoked together with the variation of dust influx in the western Tethys to explain the detected eccentricity periodicity in the δ 13 C record. Our interpretations of the δ 18 O and MS records suggest a warming event ~400 k.y. prior to the Cretaceous-Paleogene (K-Pg) boundary, and a period of climatic and environmental instability in the earliest Danian. Based on these multiproxy phase relationships, we propose an astronomical tuning for these sections; this leads us to an estimate of the timing and duration of several late Maastrichtian and Danian biostratigraphic and magnetostratigraphic events.

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.

The late Eocene may have been a period with an enhanced flux of extraterrestrial matter to Earth related either to a comet or an asteroid shower. The evidence comes from two very large and several medium-sized impact craters, at least two microtektite-microkrystite layers, and a stratigraphic interval with enhanced extraterrestrial 3 He, all within the period ca. 36.3–34.3 Ma. Here, we show that the distribution of sediment-dispersed extraterrestrial (ordinary chondritic) chromite (EC) grains in the Massignano section, central Italy, can be used to test whether the flux of ordinary chondritic matter to Earth was enhanced in the late Eocene. In twelve limestone samples, each weighing ~12–15 kg, from 1.25 m to 10.25 m above the base of the section, only 1 EC grain was found. Based on the total amount of limestone analyzed, 167 kg, this corresponds to 0.006 EC grain kg ‒1 limestone. This is a factor of five lower than the 0.029 EC grain kg ‒1 recovered in 210 kg of latest Cretaceous–Paleocene limestone from the Bottaccione Gorge section at Gubbio, central Italy. The difference can readily be explained by an approximately threefold higher sedimentation rate in the late Eocene at Massignano. In essence, our results speak against a late Eocene asteroid shower. Apparently, there was no significant increase in the flux of extraterrestrial chromite at this time, such as that after the disruption of the L-chondrite parent body in the mid-Ordovician, when the EC flux was enhanced by two orders of magnitude. We also discuss the potential to search for lunar minerals in the Massignano section in order to test the recent hypothesis that late Eocene 3 He enrichments originated from impact-ejected lunar regolith.