Marine organic carbon burial increased forest fire frequency during Oceanic Anoxic Event 2

New Constraints on Global Geochemical Cycling During Oceanic Anoxic Event 2 (Late Cretaceous) From a 6‐Million‐year Long Molybdenum‐Isotope Record

“…For OAE 2, U isotopes (Clarkson et al., 2018) and Zn isotopes (Sweere et al., 2018) also show remarkably muted changes compared to Late Cenomanian background compositions. In both cases, significant metal‐isotope variability was registered during OAE 2 rather than at its onset or termination, specifically during the so‐called Plenus Cold Event, an interval of regionally modulated cooling and re‐oxygenation of ocean waters (Boundinot & Sepúlveda, 2020; Jenkyns et al., 2017; O'Connor et al., 2020). These geochemical changes, a negative excursion in the case of Zn, a positive excursion in the case of U, can be related to the isotopically distinct behavior of these elements during burial in reducing and oxidizing sedimentary environments and the consequent effect on ocean chemistry.…”

Carbon Cycling During Oceanic Anoxic Event 2: Compound‐Specific Carbon Isotope Evidence From the Western Interior Seaway

“…While the overall trend of the CIE phase reflects global-scale organic carbon burial (e.g., Owens et al, 2018), the concomitant punctuation of isotopically light carbon in both marine and terrestrial biomarkers likely indeed reflects a pulse of isotopically light CO 2 to the ocean-atmosphere system (Figure 6d). While some studies have shown evidence of forest fires in the western US during the middle of the initial CIE (Baker et al, 2019), other studies of the SH#1 core have not shown such evidence (Boudinot & Sepúlveda, 2020), highlighting uncertainties in the sources and extent of such CO 2 pulse at this interval. The similarities in terrestrial biomarker δ 13 C records from the WIS (this study) and the Atlantic basin (Kuypers et al, 1999) with marine biomarkers and resulting pCO 2 estimates (Figure 6d) do support the interpretation of globally increased pCO 2 even during the initial CIE, and ultimately highlights the dynamic nature of the global carbon cycle at the onset of OAE2.…”

“…, increased ocean temperature (Bice et al, 2006;Huber et al, 2002;O'Brien et al, 2017;Wilson & Norris, 2001), and ultimately widespread marine organic carbon burial during OAE2 (Arthur et al, 1987;Schlanger & Jenkyns, 1976). Questions remain, however, concerning the nature of the carbon cycle perturbations within the OAE2 event itself (e.g., Boudinot & Sepúlveda, 2020;O'Connor et al, 2019).…”

“…The Smokey Hollow #1 core (SH#1 core; Figure 1) presents an expanded sedimentary BOUDINOT ET AL. record of OAE2 from the western margin of the Western Interior Seaway (WIS; Jones et al, 2019) that contains both marine-derived and terrestrially derived biomarkers (Boudinot & Sepúlveda, 2020;, providing a high-resolution archive of marine and atmospheric carbon, respectively. Using carbon isotopes of biomarkers in the SH#1 core, we test the hypotheses that (a) carbon isotopes from marine-derived and terrestrial-derived biomarkers preserved in neritic ecosystems record changes in global and local carbon cycle dynamics, (b) that OAE2 was spurred by a pulse of CO 2 to the atmosphere before the event, (c) that the onset (initial CIE) of OAE2 was characterized by a unilateral drawdown of atmospheric and aqueous CO 2 , and (d) that the Plenus event experienced multiple pulses of enhanced atmospheric CO 2 input.…”

Characteristics and evolution of inertinite abundance and atmospheric pO2 during China’s coal-forming periods

“…Early Cretaceous anoxic event (Huang et al 2008) had profound effects on the atmosphere-ocean system, as well as the accompanying global cooling and the enhancement of the ocean oxidative capacity. Boudinot and Sepúlveda (2020) believed that the Mid-Cretaceous oceanic anoxic event would lead to a decrease in pCO 2 and an increase in pO 2 in the atmospheric and oceanic system, and trigger mountain fires, indicating that the oxygen content in the Mid-Cretaceous was not low. Atmospheric pO 2 was calculated by simulating the abundance of inertinite in coal during this period.…”