Bolide summer: The Paleocene/Eocene thermal maximum as a response to an extraterrestrial trigger

Abstract

The standard paradigm that the Paleocene/Eocene thermal maximum (PETM) represents a threshold event intrinsic to Earth's climate and connected in some way with long-term warming has influenced interpretations of the geochemical, climate, and biological perturbations that occurred at this event. As recent high-resolution data have demonstrated that the onset of the event was geologically instantaneous, attempts to account for the event solely through endogenous mechanisms have become increasingly strained. The rapid onset of the event indicates that it was triggered by a catastrophic event which we suggest was most likely a bolide impact. We discuss features of the PETM that require explanation and argue that mechanisms that have previously been proposed either cannot explain all of these features or would require some sort of high-energy trigger. A bolide impact could provide such a trigger and, in the event of a comet impact, could contribute directly to the shape of the carbon isotope curve. We introduce a carbon cyle model that would explain the PETM by global warming following a bolide impact, leading to oxidation of terrestrial organic carbon stores built up during the late Paleocene. Our intention is to encourage other researchers to seriously consider an impact trigger for the PETM, especially in the absence of plausible alternative mechanisms.

Drilling disturbance and constraints on the onset of the Paleocene–Eocene boundary carbon isotope excursion in New Jersey

“…All attempts at explaining the event involve the addition of large amounts of isotopically light carbon to the exogenic carbon pool. Non-exclusive possibilities include volcanic emissions (Eldholm and Thomas, 1993;Bralower et al, 1997;Storey et al, 2007), the mobilization and oxidation of seafloor methane from clathrates (Dickens et al, 1995;Katz et al, 1999), emission of thermogenic methane from deeply buried hydrocarbons after igneous intrusion (Kurtz et al, 2003;Svenson et al, 2004), oxidation of organic-rich sediments in epicontinental seas (Higgins and Schrag, 2006), release of dissolved carbon compounds from stratified marine basins (Nisbet et al, 2009), runaway release of methane from rapidly melting permafrost (Deconto et al, 2012), combustion of part of the P. N. Pearson and E. Thomas: Drilling disturbance and constraints on the onset of the Paleocene-Eocene biosphere (Huber, 2008), and extraterrestrial carbon dumped by a comet, the impact of which could have triggered further methane release (Kent et al, 2003;Cramer and Kent, 2005;Wang et al, 2013). Most stratigraphic records indicate a geologically rapid onset, but that definition could mean any duration between approx.…”

“…Most stratigraphic records indicate a geologically rapid onset, but that definition could mean any duration between approx. 20 thousand years (Cui et al, 2011) and a few thousand years (e.g., Kennett and Stott, 1991;Thomas et al, 2002;Zachos et al, 2005Zachos et al, , 2007Aziz et al, 2008a) or just a few years, i.e., effectively instantaneous (Kent et al, 2003;Cramer and Kent, 2005). Resolution of this question will provide constraints on the likely source of the carbon and advance our understanding of disturbances of Earth's carbon cycle and their effect on ocean chemistry and life.…”

Magnetofossil spike during the Paleocene‐Eocene thermal maximum: Ferromagnetic resonance, rock magnetic, and electron microscopy evidence from Ancora, New Jersey, United States

“…Kent et al dismissed the possibility that the magnetic properties of the New Jersey PETM clay were produced by magnetofossils because they imaged only isolated, equidimensional magnetite under transmission electron microscopy (TEM). The production of a similarly anomalous magnetic nanophase, albeit one composed of ferric oxyhydroxides, as fallout condensate from the end-Cretaceous impact [Wdowiak et al, 2001] led them to hypothesize instead that the PETM was a ''bolide summer'' triggered by a cometary impact [Cramer and Kent, 2005;Kent et al, 2003].…”

Two massive, rapid releases of carbon during the onset of the Palaeocene–Eocene thermal maximum

“…Several proposed models do not satisfy these constraints, either because the triggering mechanism is unique (for example, bolide impacts 21 ), or because they release carbon at relatively low rates (for example, seaway desiccation 22 , permafrost oxidation 23 ). Recent evidence for extremely rapid PETM C release that has been suggested to support an impact trigger for the event 3 is derived from a short marine-margin record, which may truncate evidence for the POE.…”