Estimating the impact of the cryptic degassing of Large Igneous Provinces: A mid-Miocene case-study

Abstract

21Large Igneous Provinces (LIPs) have been emplaced throughout Earth's history, erupting that can release significant volumes of carbon into the ocean-atmosphere system (Bryan and , 2008; Coffin and Eldholm, 1994; Courtillot and Renne, 2003; Ernst et al., 2005).47 Ernst 48While the LIPs with the largest volumes (e.g. the Siberian Traps or the Central Atlantic 49Magmatic Province) are widely accepted to have triggered episodes of carbon cycle 50 perturbation, global warmth and ecological crisis (Grard et al., 2005; Sobolev et al., 2011; 51 Wignall, 2005 51 Wignall, , 2001, the case for LIPs with smaller (≤2x10 6 km 3 ) volumes (e.g., the Deccan 52Traps or the Columbia River Basalt), emitting sufficient CO 2 to cause a significant global 53 impact is a subject of debate (Caldeira and Rampino, 1990; Diester-Haass et al., 2009; 54 Kender et al., 2009; Self et al., 2006; Taylor and Lasaga, 1999 2011a; Erwin, 2006; Ganino and Arndt, 2010, 2009; Iacono-Marziano et al., 2012; Retallack 60 and Jahren, 2008; Svensen et al., 2009 Svensen et al., , 2004, and the potential impact of the recycling of 61 mafic crust into the LIP magma source (Sobolev et al., 2011 2013; Barry et al., 2013Barry et al., , 2010 Hooper, 1997 Hooper, , 1988 Reidel et al., 2013b; Wolff and Ramos, 78 2013) (Fig. 2), with the initiation of the CRB eruptions coinciding with the core of both the 79 MCO and the MCIE (Fig. 1). In detail, the peak of the carbon cycle perturbation occurs ca. 8016.0 Ma (Fig. 3) parameters, and the lack of dynamic ocean, atmosphere and terrestrial biosphere components. 119Both models are tuned with estimates for mid-Miocene parameters (Tables S1-3) burial, is also analysed by calculating a sensitivity index using the formula:where S is the sensitivity index, p the parameter value, Y the model results for p, and ' 143denoting the parameter value and model results after the ± 10 % change in p (Haefner, 1996). 144A sensitivity index value of S ≤ ±0. the Siberian Traps) ( Table 2). An EAF of 2.0-6.4 also applies to this crustal-contamination 217 emission scenario. 218An additional source of cryptic degassing beyond magma degassing is the In Figure 4 we compare palaeorecords with model simulations for δ 13 C, CCD and 247 atmospheric CO 2. We find that sub-aerial basalt degassing alone has a negligible effect in our 248 simulations, but that adding cryptic degassing results in excursions similar to those seen in 249 the palaeorecords. In some respects these results are counter-intuitive because they simulate: carbon an isotopic value of -12 ‰ results in a δ 13 C excursion similar to but slightly larger 266 than in our best-fit simulation in MTW08 (Fig. S1), indicating that our main conclusions are 267 not particularly sensitive to uncertainty in this parameter. 268We find that in MTW08 an emission scenario of 1000 Pg C from the Steens and 3000-4000 Pg C of this emitted during just the GRB eruptions, best fits the palaeorecords. 279This emission range falls within the upper end of the range 460-6...

Global carbon cycle perturbation across the Eocene‐Oligocene climate transition

“…In comparison to the variability demonstrated during the Eocene, the CCD remains relatively stable in the equatorial Pacific after the EOT despite fluctuations in Oligocene ice sheets and temperatures [ Palike et al ., ; Pälike et al ., ]. CCD stability was only interrupted in the mid‐Miocene, by the shoaling and subsequent redeepening of the CCD potentially associated with the deglaciation and reglaciation bracketing the Miocene Climatic Optimum [ Lyle , ; Armstrong McKay et al ., ]. This observation implies that post‐EOT fluctuations in sea level and climate mostly failed to restore Eocene levels of shelf carbonate burial, suggesting that a threshold in the ocean carbonate system may have been crossed at the EOT beyond which a substantial fraction of carbonate burial permanently shifted to ocean basin settings.…”

Using 40Ar/39Ar ages of intercalated silicic tuffs to date flood basalts: Precise ages for Steens Basalt Member of the Columbia River Basalt Group

“…Even if this mismatch were attributed to an offset between orbitally tuned ages and the isotopic record, the eruption of the entire Columbia River Basalt Group can account for only a small part of the Middle Miocene 3-8°C warming relative to preindustrial values (You et al, 2009), even with a generous allowance for degassing of related intrusions and unspecified carbon-bearing host rocks (Armstrong McKay et al, 2014). Hence, this relatively small flood basalt episode is unlikely to have caused the Miocene Climatic Optimum, but the CO 2 it emitted could have helped intensify it and delay reglaciation of Antarctica (Armstrong McKay et al, 2014;Holbourn et al, 2015).…”

Distinct Degassing Pulses During Magma Invasion in the Stratified Karoo Basin—New Insights From Hydrothermal Fluid Flow Modeling

“…Jones et al (2016) estimate a release of up to 70 Mt carbon (C) per cubic kilometer of magma emplaced based on various studies of the Karoo LIP (Aarnes et al, , 2011Svensen et al, 2007). This process is now broadly accepted as one of the main driving mechanisms for rapid climate change and mass extinction (e.g., Aarnes et al, 2010;Ganino & Arndt, 2009) such as the End-Permian (Siberian Traps, Heydari et al, 2008;Retallack & Jahren, 2008;Svensen et al, 2009), the End-Triassic (Central Atlantic Magmatic Province, e.g., Blackburn et al, 2013;Jones et al, 2016), the Toarcian (Karoo-Ferrar LIP, Svensen et al, 2007Svensen et al, , 2012Burgess et al, 2015), the Palaeocene-Eocene Thermal Maximum (Northeast Atlantic Igneous Province, e.g., Svensen et al, 2004), and the mid-Miocene climatic optimum associated with the Columbia River Basalt (McKay et al, 2014). Traces of violent release of thermogenic gases at the basin top are found in the form of pipe-like structures that root to the contact aureole of the sill intrusions at depth (Figure 1).…”