HR: 0800h
AN: PP51D-1356    [Abstracts]
TI: From Greenhouse to Icehouse: Evidence of Climatic Changes Across the Marine Eocene-Oligocene Transition From the Massignano GSSP Section (Central Italy)
AU: * Coccioni, R
EM: cron@info-net.it
AF: Istituto di Geologia e Centro di Geobiologia dell'Universit\`{a}, Campus Scientifico, Localit\`{a} Crocicchia, Urbino, PU 61029 Italy
AU: Marsili, A
EM: andrea.marsili@uniurb.it
AF: Istituto di Geologia e Centro di Geobiologia dell'Universit\`{a}, Campus Scientifico, Localit\`{a} Crocicchia, Urbino, PU 61029 Italy
AU: Montanari, A
EM: sandro.ogc@fastnet.it
AF: Osservatorio Geologico, Coldigioco, Frontale di Apiro, MC 62020 Italy
AB: The transition from global "greenhouse" conditions of the early and middle Eocene to global "icehouse" conditions of the early Oligocene marks a turning point in Cenozoic Earth history which was marked by reorganization of global ocean circulation patterns and significant turnovers in the marine and terrestrial biota (Prothero et al., 2003) and led to the development of the first East Antarctic ice-sheet, close to the Eocene/Oligocene boundary (33.7 Ma). The Massignano GSSP for the Eocene/Oligocene boundary (Premoli Silva & Jenkins, 1993), exposed in an abandoned quarry in the Monte Conero area, on the Adriatic coast of central Italy, was investigated at high-resolution in order to provide evidence for climatic changes across the marine Eocene-Oligocene transition. The Massignano section is 23-m thick and consists of alternating reddish/greenish-grey marls and calcareous marls with several biotite-rich levels of volcanic origin which were deposited in a lower bathyal depositional setting, at a paleodepth of 1000-2000 m (Coccioni & Galeotti, 2003). A complete geological record of 3 myr (from 36.2 to 33.2 Ma according to the time scale of Berggren et al., 1995) is preserved which spans the interval from the latest Eocene to the early Oligocene, from Chron C16n to C13n (Bice & Montanari, 1988; Lowrie & Lanci, 1994), and is provided by an accurate calibration of bio- and geochemical events. Cosmic signatures are also recorded in the Massignano section (Montanari et al., 1993) where three impactoclastic, iridium-rich layers occurs in the middle-lower part of the succession (Montanari et al., 1988, 1993; Bodeselitsch et al., 2004). They are possibly linked to the Popigai and Chesapeake Bay impacts and related to a comet shower over a duration of 2.2 myr (Farley et al., 1998). Calcareous nannofossil and foraminiferal assemblages (Coccioni et al., 2000; Spezzaferri et al., 2002), dinoflagellate cyst palynology (Brinkhuis & Biffi, 1993), ostracod faunas (Dall'Antonia et al., 2003), oxygen and carbon isotopes (Bodeselitsch et al., 2004), and environmental magnetism (Jovane et al., 2004) provide evidence of a major cooling trend with warm pulses. These pulses seems to be global in extent and may have been triggered by multiple impact events during the Late Eocene comet shower that may have played an important role related to the deterioration of the global climate at the end of the Eocene Epoch. The release of methane hydrate during and after an impact in a continental shelf (like the Chesapeake Bay impact) or seafloor, or impacts of $^{12}$C-rich comets may account for the observed negative isotope excursions. References Bice D. and Montanari A., 1988. IUGS Spec. Publ., Graf. Aniballi, 111-117; Bodeselitsch B. et al., 2004. E.P.S.L., 223, 283-302; Brinkhuis H. and Biffi U., 1993. Mar. Mic., 22, 131-183; Coccioni R. et al., 2000. Terra Nova, 12, 258-263; Coccioni R. and Galeotti S., 2003. In: Prothero D.R. et al., (eds.), 2003. Columbia Univ. Press, 438-452; Dall'Antonia B. et al., 2003. Mar. Mic., 48, 91-106; Farley K.A. et al., 1998. Science, 280, 1250-1253; Jovane L. et al., 2004. Geoph. Res. Let., 31, L15601, doi:10.1029/2004GL020554; Lowrie W. and Lanci L., 1994. E.P.S.L., 126, 247-258; Montanari A. et al., 1993. Palaios, 8, 420-437; Montanari A. et al., 1988. IUGS Spec. Publ., Graf. Aniballi, 195-208; Premoli Silva I. and Jenkins D.G., 1993. Episodes, 16, 379-382; Prothero D.R. et al., (eds.), 2003. Columbia Univ. Press, 541 pp.; Spezzaferri S. et al., 2002. J. Foram. Res., 32, 188-199.
DE: 4825 Geochemistry
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
DE: 1512 Environmental magnetism
DE: 1600 GLOBAL CHANGE (New category)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting