HR: 0830h
AN: PP41B-0838    [PDF]
TI: Aptian-Albian Carbon Burial Episodes At The Apulian Platform Margin (Gargano Promontory, Southern Italy): Regional Versus Global Driven-Mechanisms
AU: * Luciani, V
EM: lcv@unife.it
AF: Dipartimento di Scienze della Terra, Universit… di FerraraParks Road, Corso Ercole I d'Este, 32, Ferrara, 44100 Italy
AU: Cobianchi, M
EM: miriam@unipv.it
AF: Dipartimento di Scienze della Terra, Universit… di Pavia, Via Ferrata 1, Pavia, 27100 Italy
AU: Jenkyns, H C
EM: Hugh.Jenkyns@earth.ox.ac.uk
AF: Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR United Kingdom
AU: Lupi, C
AF: Dipartimento di Scienze della Terra, Universit… di Pavia, Via Ferrata 1, Pavia, 27100 Italy
AB: The Gargano Promontory (Southern Italy), located at the eastern margin of the Apulia Platform, is a peculiar area of the Tethys where the transition between platform and adjacent basins is exposed on land. Microfossil distribution patterns and high-resolution carbon- and oxygen-isotope curves, calibrated against planktonic foraminiferal and calcareous nannofossil biostratigraphy, are provided for the Aptian-Albian pelagic succession (Marne a Fucoidi). The Gargano Promontory sequence shows similarities with that of the nearby Umbria-Marche Basin, though some lithological differences exist probably due to the platform proximity. In the Marne a Fucoidi of the Gargano area, four carbon burial episodes were documented. The biostratigraphic data assign the older black shale to the Selli Level equivalent (Lower Aptian); this carbon-rich interval is immediately followed by another black shale early Late Aptian in age. In the Albian portion of the succession two anoxic episodes occur and correlate the `Urbino Level' (OAE1b, Lower Albian) and `Amadeus segment' (OAE1c, Upper Albian) of the Umbria-Marche Basin.The carbon-and oxygen-isotope record is in line of evidence with the curves documented elsewhere. Nevertheless, regional controlling factors influenced the record of the global anoxic events producing sedimentary expressions and biotic responses which may differ from those of the type-locality. The Selli Event (OAE1a), characterized by a pronounced abrupt negative carbon-isotope excursion, is generally interpreted as a high productivity episode followed by a global cooling trend. In the Gargano Promontory, albeit the carbon- and oxygen-isotope curves support the same evolution, the micropaleontological data do not give evidence of particularly high fertility of the surface waters.The lower Upper Aptian black shale appears as a local event and correlates the main Aptian carbon-isotope positive excursion. For this episode, the micropaleontological data indicate an increase in surface-water fertility. In the Lower and Upper Albian stratigraphic interval, the carbon-isotope curve records two pronounced negative shifts followed by marked increases of the values. The oxygen-isotope curve shows negative shifts in the same stratigraphic position, which may be interpreted as, essentially primary, records of warming events. The synchronous negative shifts in carbon and oxygen isotope curves may be the documentation of dissociation of gas hydrates somewhere in the world ocean and the near-instantaneous oxidation of the released methane to another greenhouse gas, carbon dioxide and consequent rapid global warming. The two Albian episodes of organic carbon burial, the `Urbino' and Amadeus' level equivalents, correlate the carbon and oxygen shifts. Microfossil distribution patterns give evidence of high productivity for these episodes. Global versus regional features of Albian anoxic episodes are still largely debated. A reliable correlation exists between the Lower Albian successions of the Gargano Promontory, the Vocontian Basin (Southeastern France) and the Magazan Plateau (Northwest Africa). Similar isotopic signatures for the Albian events may record phenomenma that were similar in kind.
DE: 1030 Geochemical cycles (0330)
DE: 1040 Isotopic composition/chemistry
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting