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Late Eocene impact-induced climate and hydrological changes; evidence from the Massignano global stratotype section and point (central Italy)

Rodolfo Coccioni, Fabrizio Frontalini and Silvia Spezzaferri
Late Eocene impact-induced climate and hydrological changes; evidence from the Massignano global stratotype section and point (central Italy) (in The late Eocene Earth; hothouse, icehouse, and impacts, Christian Koeberl (editor) and Alessandro Montanari (editor))
Special Paper - Geological Society of America (2009) 452: 97-118


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 strato-type 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 (super 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 (sub 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.

ISSN: 0072-1077
EISSN: 2331-219X
Serial Title: Special Paper - Geological Society of America
Serial Volume: 452
Title: Late Eocene impact-induced climate and hydrological changes; evidence from the Massignano global stratotype section and point (central Italy)
Title: The late Eocene Earth; hothouse, icehouse, and impacts
Author(s): Coccioni, RodolfoFrontalini, FabrizioSpezzaferri, Silvia
Author(s): Koeberl, Christianeditor
Author(s): Montanari, Alessandroeditor
Affiliation: Universita degli Studi di Urbino, Dipartimento di Scienze dell'Uomo, dell'Ambiente e della Natura, Urbino, Italy
Affiliation: University of Vienna, Department of Lithospheric Research, Vienna, Austria
Pages: 97-118
Published: 2009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2452-2
Meeting name: Geological Sociaty of America (GSA) Penrose conference
Meeting location: Ancona, ITA, Italy
Meeting date: 20071003Oct. 3-6, 2007
References: 137
Accession Number: 2009-074333
Categories: Stratigraphy
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 2 tables, sketch map
N43°31'60" - N43°31'60", E13°48'00" - E13°48'00"
Secondary Affiliation: Osservatorio Geologico di Coldigioco, ITA, ItalyUniversity of Fribourg, CHE, Switzerland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200940
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