Valeria Luciani

An early Eocene carbon cycle perturbation at 52.5 Ma in the Southern Alps: Chronology and biotic response

An early Eocene carbon cycle perturbation at ~52.5 Ma from the southern Alps: Chronology and biotic response

Paleoecology of the Cretaceous–Tertiary mass extinction in planktonic foraminifera

Abstract Paleobiogeographic patterns of the Cretaceous–Tertiary (K–T) mass extinction in planktonic foraminifera in Tunisia, spanning environments from open marine upper bathyal, to shelf and shallow marginal settings, indicate a surprisingly selective and environmentally mediated mass extinction. This selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction, including species richness, ecological generalists, ecological specialists, surface and subsurface dwellers, whether based on the number of species or the relative percent abundances of species. The following conclusions can be reached for shallow to deep environments: about three quarters of the species disappeared at or near the K–T boundary and only ecological generalists able to tolerate wide variations in temperature, nutrients, salinity and oxygen survived. Among the ecological generalists (heterohelicids, guembelitrids, hedbergellids and globigerinellids), only surface dwellers survived. Ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively. Biserials thrived during the latest Maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early Danian. Triserials thrived only in shallow marginal marine environments, or similarly stressed ecosystems, during the latest Maastrichtian, but dominated both open marine and restricted marginal settings in the early Danian. This highly selective mass extinction pattern reflects dramatic changes in temperature, salinity, oxygen and nutrients across the K–T boundary in the low latitude Tethys ocean which appear to be the result of both long-term environmental changes (e.g., climate, sea level, volcanism) and short-term effects (bolide impact).

Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal for defining the middle-late Eocene boundary

The Alano section has been presented at the International Subcommission on Paleogene Stratigraphy (ISPS) as a potential candidate for defi ning the global boundary stratotype section and point (GSSP) of the late Eocene Priabonian Stage. The section is located in the Venetian Southern Alps of the Veneto region (NE Italy), which is the type area of the Priabonian, being exposed along the banks of the Calcino torrent, near the village of Alano di Piave. It consists of ~120–130 m of bathyal gray marls interrupted in the lower part by an 8-m-thick package of laminated dark to black marlstones. Intercalated in the section, there are eight prominent marker beds, six of which are crystal tuff layers, whereas the other two are bioclastic rudites. These distinctive layers are useful for regional correlation and for an easy recognition of the various intervals of the section. The section is easily accessible, crops out continuously, is unaffected by any structural deformation, is rich in calcareous plankton, and contains an expanded record of the critical interval for defi ning the GSSP of the Priabonian. In order to further check the stratigraphic completeness of the section and constrain in time the critical interval for defi ning the Priabonian Stage, we performed a high-resolution study of integrated calcareous plankton biostratigraphy and a detailed magnetostratigraphic analysis. Here, we present the results of these studies to open a discussion on the criteria for driving the “golden spike” that should define the middle Eocene–late Eocene boundary.

High-resolution planktonic foraminiferal analysis from the Cretaceous–Tertiary boundary at Ain Settara (Tunisia): evidence of an extended mass extinction

Abstract The Ain Settara section, located in the Kalaat-Senan area of north–central Tunisia, spans the Cretaceous–Tertiary (K–T) boundary which is characterized by a red layer and a thin non-bioturbated boundary clay. Sediment accumulation across the K–T boundary at Ain Settara was probably interrupted by three short hiatuses and/or condensed sedimentation. The first hiatus occurs at the top of the CF1 Zone; the second hiatus/condensation occurred just below the boundary clay and the third hiatus at the P0/P1a boundary, in the earliest Danian. These hiatuses are marked by weak unconformities, bioturbation and sudden disappearances/appearances of species which are known to disappear/evolve sequentially in continuous sections. Quantitative high-resolution planktonic foraminiferal analysis across zones CF1(upper), P0 and P1a(1) reveals an extended and selective mass extinction. All 41% of the species which disappeared at or below the K–T boundary are rare to very rare and primarily ecologically specialized keeled deeper-dwelling tropical–subtropical forms (Globotruncana, Globotruncanita, Gublerina, Planoglobulina, Rosita (Contusotruncana), Racemiguembelina). Their combined relative abundance varies between 10% and 15% of the total population at the end of the Maastrichtian. The K–T crisis thus appears more catastrophic when viewed in tropical–subtropical assemblages and based on analysis of larger species (>200 μm) which preferentially includes the more specialized forms, though, in fact, the K–T mass extinction actually involved a relatively small part of the foraminiferal population in terms of relative abundance. The pattern of extinction and changes in dominant population at Ain Settara appear to be very similar to the planktonic foraminiferal turnover of the other north–central Tunisian sections (El Kef, Elles). The selective mass extinction pattern suggests that the catastrophic effects of the bolide impact superimposed those related to long-term environmental changes, such as variations in temperature, sea-level and associated water-mass changes.

Organic carbon burial following the middle Eocene climatic optimum in the central western Tethys

We present trace metal geochemistry and stable isotope records for the middle Eocene Alano di Piave section, NE Italy, deposited during magnetochron C18n in the marginal Tethys Ocean. We identify a

PLANKTONIC FORAMINIFERA AND ENVIRONMENTAL CHANGES ACROSS THE BONARELLI EVENT (OAE2, LATEST CENOMANIAN) IN ITS TYPE AREA: A HIGH-RESOLUTION STUDY FROM THE TETHYAN REFERENCE BOTTACCIONE SECTION (GUBBIO, CENTRAL ITALY)

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The middle Eocene climatic optimum (MECO): A multiproxy record of paleoceanographic changes in the southeast Atlantic (ODP Site 1263, Walvis Ridge)

500 kyr long carbon isotope perturbation event we infer to be the middle Eocene Climatic Optimum (MECO) confirming the northern hemisphere expression and global occurrence of MECO. Interpreted peak climatic conditions are followed by the rapid deposition of two organic rich intervals (

Guembelitria irregularis Bloom at the K-T Boundary: Morphological Abnormalities Induced by Impact-related Extreme Environmental Stress?

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Tethyan Cenomanian pelagic rhythmic sedimentation and Pleistocene Mediterranean sapropels: is the biotic signal comparable?

3\% TOC) and contemporaneous positive

Environmental perturbations at the early Eocene ETM2, H2 and I1 events as inferred by Tethyan calcareous plankton (Terche section, northeastern Italy)

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