No abstract

Terra Nova, 24, 380–386, 2012 Abstract A high‐resolution, integrated stratigraphic framework (stable isotope stratigraphy, standard calcareous nannofossil and foraminiferal biostratigraphy, magnetostratigraphy) together with geochemical and rock magnetic properties’ analyses of a complete and well‐preserved succession at Contessa Valley (Gubbio, central Italy) have offered an excellent opportunity to identify and constrain the Palaeocene to early Eocene hyperthermals and carbon isotope excursions (CIEs). In addition, we provide the first evidence in the Tethys Ocean of CIEs, previously identified in the Pacific, Atlantic and Southern Oceans, highlighting their global significance and of some unknown CIEs. Their characteristics are compared with those reported for deep‐sea cores and other land‐based sections to test whether the signature associated with CIEs documented in our composite section might give evidence for tracing them over wider areas. The Contessa composite section thus represents a reference succession also for insight into the magnetobiochronostratigraphy and the magnitude of early Palaeogene hyperthermals and CIEs.

No abstract available. <br><br> doi:<a href="http://dx.doi.org/:10.2204/iodp.sd.13.07.2011" target="_blank">:10.2204/iodp.sd.13.07.2011</a>

Abstract. The Xingu River is a large clearwater river in eastern Amazonia and its downstream sector, known as the Volta Grande do Xingu ("Xingu Great Bend"), is a unique fluvial landscape that plays an important role in the biodiversity, biogeochemistry and prehistoric and historic peopling of Amazonia. The sedimentary dynamics of the Xingu River in the Volta Grande and its downstream sector will be shifted in the next few years due to the construction of dams associated with the Belo Monte hydropower project. Impacts on river biodiversity and carbon cycling are anticipated, especially due to likely changes in sedimentation and riverbed characteristics. This research project aims to define the geological and climate factors responsible for the development of the Volta Grande landscape and to track its environmental changes during the Holocene, using the modern system as a reference. In this context, sediment cores, riverbed rock and sediment samples and greenhouse gas (GHG) samples were collected in the Volta Grande do Xingu and adjacent upstream and downstream sectors. The reconstruction of past conditions in the Volta Grande is necessary for forecasting future scenarios and defining biodiversity conservation strategies under the operation of Belo Monte dams. This paper describes the scientific questions of the project and the sampling surveys performed by an international team of Earth scientists and biologists during the dry seasons of 2013 and 2014. Preliminary results are presented and a future workshop is planned to integrate results, present data to the scientific community and discuss possibilities for deeper drilling in the Xingu ria to extend the sedimentary record of the Volta Grande do Xingu.

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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

Spatial and temporal geomagnetic field variations have been observed over different geological timescales. Ancient field measurements, mainly obtained from geological materials (sedimentary and igneous rocks), allow investigations of directional and intensity variability of the paleomagnetic field that result from processes operating in Earth's fluid core (see, e.g., Hulot et al., 2010). Particularly, information about paleosecular variation (PSV), long-term variations of the order of 10 5 -10 6 years (e.g., Johnson & McFadden, 2015), is essential to better understand temporal geomagnetic field evolution and to constrain numerical geodynamo models (

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 refl ect astronomically forced climate changes (i.e., Milankovitch cycles). In particular, the MS proxy refl ects 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 infl uenced 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 infl ux 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.