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.

The Early Cretaceous represents a time interval in the greenhouse world that was characterized by dramatic changes in the paleogeography, paleoceanography, and paleoclimate of the Earth system. Furthermore, a striking, prominent feature of the geomagnetic polarity time scale is the ~34 m.y. period of the normal polarity field (Cretaceous Normal Polarity Superchron). Although marine anomalies and paleomagnetic data from deep-sea cores and land sections indicate that a reversed polarity (M0r) with a duration of ~0.4 m.y. occurred before the superchron, incomplete exposure, coupled with gaps in sampling due to the presence of marl layers, has limited the identification of M0r in a number of sections. An integrated multidisciplinary investigation of lower Cretaceous sediments at the base of the Poggio le Guaine (PLG) core (Northern Apennines, central Italy) was carried out to identify the Barremian-Aptian contact, which is defined by the M0r lower boundary. Rock magnetic measurements of the studied interval of the PLG core reveal magnetite as the main magnetic carrier. Paleomagnetic results indicate a short interval characterized by reverse polarity. This interval is in the uppermost part of the Hedbergella excelsa planktonic foraminiferal zone and in the upper part of the Chiastozygus litterarius (NC6) calcareous nannofossil zone. Stable carbon (δ 13 C) and oxygen (δ 18 O) isotopes indicate a chemostratigraphy of the PLG core with the signature of oceanic anoxic event 1a (OAE 1a). The lithological expression of OAE 1a is the organic-rich black shale unit known as the Selli Level. The comparison of our magnetostratigraphic, biostratigraphic, and chemostratigraphic records throughout the Barremian-Aptian boundary with those available from previously investigated oceanic and land-based sites allows recognition of the magnetochron M0r and OAE 1a at PLG for the first time.

The highest stages of the stratigraphic range of the planktonic foraminiferal Rotalipora cushmani were investigated in a 313-k.y.-long interval of the classical Tethyan Bottaccione section (Gubbio, Italy), the type locality of the C org- rich Bonarelli Level, which is the sedimentary expression of the worldwide latest Cenomanian oceanic anoxic event 2 (OAE 2).The disappearance of R. cushmani is associated with the major turnover of marine microfauna and microflora that involves both planktonic and benthic foraminifera, and calcareous nannofossils, slightly before the onset of OAE 2, which, according to current available data, was triggered by a massive pulse of submarine mafic volcanism accompanying the initial emplacement of the Caribbean large igneous province (CLIP). This pulse of volcanic activity probably turned the climate in a strengthened greenhouse mode, accelerating continental weathering and increasing nutrient supply in oceanic surface waters via river runoff and triggering higher fertility in the global ocean. Our investigation shows that the marine biotic turnover started ~55 k.y. before the onset of OAE 2 and is closely coeval with the first major episode, as recorded by the unradiogenic trend in 187 Os/ 188 Os, of the ongoing magmatic activity of the CLIP, which produced increasing p CO 2 , ocean dissolution and/or acidification with a severe carbonate crisis and fertilization through enormous quantities of biolimiting metals. The marine microfauna and microflora reacted rapidly to new conditions of higher p CO 2 and fertility by undergoing marked changes following three main steps. We evaluate this pattern and postulate that the first pulse of volcanogenic CO 2 from the CLIP emplacement (ca. 94.2 or 94.6 Ma) played a fundamental role in the marine biotic turnover recorded shortly before the onset of OAE 2 and notably in the local or regional disappearance of R. cushmani in the central-western Tethys.

Based on its completeness, the Bottaccione-Contessa composite section (BCCS; Gubbio area, Italy) has been analyzed to infer the paleobathymetry throughout the interval spanning the uppermost Albian to the lower Danian. Foraminifera are generally abundant and well preserved and the assemblages are dominated by planktonic foraminifera (planktonic/benthic ratio > 99%). The investigation of the benthic foraminiferal assemblages allows us to infer a lower bathyal depositional environment along most of the BCCS. A somewhat shallower deposition paleodepth is estimated for the Danian part of the BCCS, although this difference could be ascribed to the post–Cretaceous-Paleogene (K-Pg) boundary effect. This study further enhances the application potential of benthic foraminiferal assemblages as a paleobathymetric proxy.

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 Paleocene–early Eocene interval is punctuated by a series of transient warming events known as hyperthermals that have been associated with changes in the carbon isotope composition of the ocean-atmosphere system. Here we present and discuss a detailed record of calcareous nannofossil and foraminiferal assemblages coupled with high-resolution geochemical, isotopic, and environmental magnetic records across the middle Ypresian at the Contessa Road section (Gubbio, Italy). This allows characterization of the Eocene Thermal Maximum 3 (ETM3, K or X) and recognition of four minor (I1, I2, J, L) hyperthermals. At the Contessa Road section, the ETM3 is marked by short-lived negative excursions in both δ 13 C and δ 18 O, pronounced changes in rock magnetic properties, and calcium carbonate reduction. These changes coupled with the moderate to low state of preservation of calcareous nannofossils and planktonic foraminifera, higher FI and agglutinated foraminifera values, along with a lower P/(P + B) ratio (P—planktonic; B—benthic) and coarse fractions provide evidence of enhanced carbonate dissolution during the ETM3. A marked shift toward warmer and more oligotrophic conditions has been inferred that suggests unstable and perturbed environmental conditions both in the photic zone and at the seafloor.

Abstract The Monte Cagnero sedimentary section, which crops out in the northeastern Apennines near Urbania in the Umbria–Marche Basin (Italy), contains well-exposed strata spanning the middle Eocene to lower Oligocene interval. We use an integrated magnetobiostratigraphic approach to generate a high-resolution age model for the Monte Cagnero section, with the goal of obtaining a reliable chronostratigraphic framework for studying Eocene–Oligocene palaeoceanographic changes during the switch from greenhouse to icehouse conditions. The studied sediments consist of alternating reddish and greenish limestones and marlstones. A new integrated age model for the section is based on high-resolution palaeomagnetic analyses, combined with detailed planktonic foraminiferal and calcareous nannofossil biostratigraphic results. Rock magnetic measurements show that the magnetic mineralogy is dominated by a mixture of high- and low-coercivity minerals, probably representing a combination of hematite and magnetite. A robust magnetostratigraphic signal, together with the identification of key planktonic foraminiferal and nannofossil biostratigraphic events, allows construction of a detailed age model for the section. Based on these results, we infer that the section spans a continuous interval (within magnetochron resolution) from the middle Eocene to lower Oligocene ( c . 41–27 Ma; Chrons C18r–C12r). The Monte Cagnero section, therefore, represents a sequence that is suitable for studying the impact of the Neo-Tethyan gateway closure on subtropical Eocene circulation and determining the nature and timing of palaeoceanographic changes in the Tethys through the late middle Eocene to early Oligocene interval.

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

The Eocene-Oligocene transition marks the passage from “greenhouse” conditions to an “icehouse state” with progressive global cooling starting in the early middle Eocene. The late Eocene is also characterized by a high concentration of extraterrestrial impacts, the effects of which, on living organisms and climatic changes, are still not understood. We carried out a high-resolution investigation on planktonic foraminiferal assemblages in an 8-m-thick segment of the Massignano global stratotype section and point for the Eocene-Oligocene boundary with the aim of assessing the effects that the impacts may have had on the environment and this group of organisms. The studied interval is punctuated by three late Eocene iridium-rich layers, several cosmic signatures, and enhanced levels of 3 He. The two lower closely spaced iridium anomalies are possibly linked to the Popigai and Chesapeake Bay impact events, respectively, whereas no particular impact event can be assigned to the third anomaly, even if it might be correlated with some large craters. Interpretation of data suggests that all the impacts had no abrupt, dramatic effects on planktonic foraminifera. However, acting as forcing factors, they induced some environmental perturbations and may have contributed to remarkable climate changes superimposed on the general late Eocene cooling trend. The Popigai and Chesapeake Bay impact events triggered significant changes in the water mass structure, in terms of stratification and trophic resources, associated with some climatic excursions that took place within chron C16n.1n and chron C15r and at the transition between planktonic foraminiferal zones P15 and P16. The short-term warming pulse recognized after the Popigai impact might have been due to greenhouse effects produced by injection of CO 2 into the atmosphere and/or the release of methane hydrate after the impact itself. The dynamic between hydrological and climate changes across the impactoclastic layers as observed at Massignano displays different features at each impact event, probably due to the context in which each occurred in terms of impactor size, location, and target rocks. The relatively long duration of the enhanced cooling following the Chesapeake Bay impact suggests that this event induced a progressive cooling and triggered a feedback mechanism that sustained the initial impact-induced changes. Similar patterns of climatic excursions reported worldwide across the equivalent impact-ejecta horizons indicate that the impact-induced climate changes recorded at Massignano appear to be global in extent.