title: Thermogenic methane release as a cause for the long duration of the PETM.
abstract: The Paleocene-Eocene Thermal Maximum (PETM) (∼56 Ma) was a ∼170,000-y (∼170-kyr) period of global warming associated with rapid and massive injections of13C-depleted carbon into the ocean-atmosphere system, reflected in sedimentary components as a negative carbon isotope excursion (CIE). Carbon cycle modeling has indicated that the shape and magnitude of this CIE are generally explained by a large and rapid initial pulse, followed by ∼50 kyr of13C-depleted carbon injection. Suggested sources include submarine methane hydrates, terrigenous organic matter, and thermogenic methane and CO2from hydrothermal vent complexes. Here, we test for the contribution of carbon release associated with volcanic intrusions in the North Atlantic Igneous Province. We use dinoflagellate cyst and stable carbon isotope stratigraphy to date the active phase of a hydrothermal vent system and find it to postdate massive carbon release at the onset of the PETM. Crucially, however, it correlates to the period within the PETM of longer-term13C-depleted carbon release. This finding represents actual proof of PETM carbon release from a particular reservoir. Based on carbon cycle box model [i.e., Long-Term Ocean-Atmosphere-Sediment Carbon Cycle Reservoir (LOSCAR) model] experiments, we show that 4-12 pulses of carbon input from vent systems over 60 kyr with a total mass of 1,500 Pg of C, consistent with the vent literature, match the shape of the CIE and pattern of deep ocean carbonate dissolution as recorded in sediment records. We therefore conclude that CH4from the Norwegian Sea vent complexes was likely the main source of carbon during the PETM, following its dramatic onset.
authors: Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Faculty of Geosciences, Utrecht University, 3584CS Utrecht, The Netherlands; j.frieling1@uu.nl.
authors: Joost
authors: J
authors: Frieling
authors: Centre for Earth Evolution and Dynamics, University of Oslo, N-0315 Oslo, Norway.
authors: Henrik H
authors: HH
authors: Svensen
authors: Centre for Earth Evolution and Dynamics, University of Oslo, N-0315 Oslo, Norway; Volcanic Basin Petroleum Research, Oslo Innovation Centre, N-0349 Oslo, Norway.
authors: Sverre
authors: S
authors: Planke
authors: Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Faculty of Geosciences, Utrecht University, 3584CS Utrecht, The Netherlands.
authors: Marlow J
authors: MJ
authors: Cramwinckel
authors: Applied Petroleum Technology, N-2027 Kjeller, Norway.
authors: Haavard
authors: H
authors: Selnes
authors: Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Faculty of Geosciences, Utrecht University, 3584CS Utrecht, The Netherlands.
authors: Appy
authors: A
authors: Sluijs
keywords: PETM; carbon cycle; climate change; thermogenic methane; volcanism