Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (17) Citing Articles via Google Scholar Google Scholar Articles by Giusberti, L. Articles by Oddone, M. Search for Related Content GeoRef GeoRef Citation

Mode and tempo of the Paleocene-Eocene thermal maximum in an expanded section from the Venetian pre-Alps

Luca Giusberti^,1, Domenico Rio², Claudia Agnini³, Jan Backman⁴, Eliana Fornaciari⁵, Fabio Tateo⁶ and Massimo Oddone⁷

¹ Department of Geology, Paleontology and Geophysics, Padova University, Via Giotto 1, I-35137 Padova, Italy
² Department of Geology, Paleontology and Geophysics, Padova University, Via Giotto 1, I-35137 Padova, Italy, and Institute of Geosciences and Earth Resources, Consiglio Nazionale delle Ricerche (CNR) Padova, c/o Department of Geology, Paleontology and Geophysics, Padova University, Via Giotto 1, I-35137 Padova, Italy
³ Department of Geology, Paleontology and Geophysics, Padova University, Via Giotto 1, I-35137 Padova, Italy
⁴ Department of Geology and Geochemistry, Stockholm University, SE-106 91 Stockholm, Sweden
⁵ Department of Geology, Paleontology and Geophysics, Padova University, Via Giotto 1, I-35137 Padova, Italy
⁶ Institute of Geosciences and Earth Resources, Consiglio Nazionale delle Ricerche (CNR) Padova, c/o Department of Geology, Paleontology and Geophysics, Padova University, Via Giotto 1, I-35137 Padova, Italy
⁷ Department of General Chemistry, University of Pavia, Via Taramelli 12, I-27100 Pavia, Italy

The central part of the Piave River valley in the Venetian pre-Alps of NE Italy exposes an expanded and continuous marine sediment succession that encompasses the Paleocene series and the Paleocene to Eocene transition. The Paleocene through lowermost Eocene succession is >100 m thick and was deposited at middle to lower bathyal depths in a hemipelagic, near-continental setting in the central western Tethys. In the Forada section, the Paleocene succession of limestone-marl couplets is sharply interrupted by an 3.30-m-thick unit of clays and marls (clay marl unit). The very base of this unit represents the biostratigraphic Paleocene-Eocene boundary, and the entire unit coincides with the main carbon isotope excursion of the Paleocene-Eocene thermal maximum event. Concentrations of hematite and biogenic carbonate, ¹³C measurements, and abundance of radiolarians, all oscillate in a cyclical fashion and are interpreted to represent precession cycles. The main excursion interval spans five complete cycles, that is, 105 ± 10 k.y. The overlying carbon isotope recovery interval, which is composed of six distinct limestone-marl couplets, is interpreted to represent six precessional cycles with a duration of 126 ± 12 k.y. The entire carbon isotope excursion interval in Forada has a total duration of 231 ± 22 k.y., which is 5%–10% longer than previous estimates derived from open ocean sites (210–220 k.y.). Geochemical proxies for redox conditions indicate oxygenated conditions before, during, and after the carbon isotope excursion event. The Forada section exhibits a nonstepped sharp decrease in ¹³C (–2.35) at the base of the clay marl unit. The hemipelagic, near-continental depositional setting of Forada and the sharply elevated sedimentation rates throughout the clay marl unit argue for continuous rather than interrupted deposition and show that the initial nonstepped carbon isotope shift was not caused by a hiatus. A single sample at the base of the unit lacks biogenic carbonate. Preservation of carbonate thereafter improves progressively up-section in the clay marl unit, which is consistent with a prodigiously abrupt and rapid acidification of the oceans followed by a slower, successive deepening of the carbonate compensation depth. Increased sedimentation rates through the clay marl unit (approximately the main interval of the carbon isotope excursion) are consistent with an intensified hydrological cycle driven by super-greenhouse conditions and enhanced weathering and transport of terrigenous material to this near-continental, hemipelagic environment in the central western Tethys.

The sharp transition in lithology from the clay marl unit to the overlying limestone-marl couplets in the recovery interval and the coincident shift toward heavier ¹³C values suggest that the silicate pump and continental weathering, the cause of the enhanced terrigenous flux to Forada, stopped abruptly. This implies that the source of the light CO₂ eased to be added to the ocean-atmosphere system at the top of the clay marl unit.

Key Words: Paleocene-Eocene thermal maximum • carbon isotope record • central western Tethys • stratigraphy • geochemistry • mineralogy • chronology • silicate pump

This article has been cited by other articles:

				L. ALEGRET, S. ORTIZ, X. ORUE-ETXEBARRIA, G. BERNAOLA, J. I. BACETA, S. MONECHI, E. APELLANIZ, and V. PUJALTE THE PALEOCENE-EOCENE THERMAL MAXIMUM: NEW DATA ON MICROFOSSIL TURNOVER AT THE ZUMAIA SECTION, SPAIN Palaios, May 1, 2009; 24(5): 318 - 328. [Abstract] [Full Text] [PDF]

				M. J. Nicolo, G. R. Dickens, C. J. Hollis, and J. C. Zachos Multiple early Eocene hyperthermals: Their sedimentary expression on the New Zealand continental margin and in the deep sea Geology, August 1, 2007; 35(8): 699 - 702. [Abstract] [Full Text] [PDF]