Sedimentary Mercury Enrichments as a Marker for Submarine Large Igneous Province Volcanism? Evidence From the Mid‐Cenomanian Event and Oceanic Anoxic Event 2 (Late Cretaceous)

Abstract

Oceanic Anoxic Event 2 (OAE 2), during the Cenomanian‐Turonian transition (∼94 Ma), was the largest perturbation of the global carbon cycle in the mid‐Cretaceous and can be recognized by a positive carbon‐isotope excursion in sedimentary strata. Although OAE 2 has been linked to large‐scale volcanism, several large igneous provinces (LIPs) were active at this time (e.g., Caribbean, High Arctic, Madagascan, Ontong‐Java) and little clear evidence links OAE 2 to a specific LIP. The Mid‐Cenomanian Event (MCE, ∼96 Ma), identified by a small, 1‰ positive carbon‐isotope excursion, is often referred to as a prelude to OAE 2. However, no underlying cause has yet been demonstrated and its relationship to OAE 2 is poorly constrained. Here we report sedimentary mercury (Hg) concentration data from four sites, three from the southern margin of the Western Interior Seaway and one from Demerara Rise, in the equatorial proto‐North Atlantic Ocean. We find that, in both areas, increases in mercury concentrations and Hg/TOC ratios coincide with the MCE and the OAE 2. However, the increases found in these sites are of a lower magnitude than those found in records of many other Mesozoic events, possibly characteristic of a marine rather than atmospheric dispersal of mercury for both events. Combined, the new mercury data presented here are consistent with an initial magmatic pulse at the time of the MCE, with a second, greater pulse at the onset of OAE 2, possibly related to the emplacement of LIPs in the Pacific Ocean and/or the High Arctic.

High-resolution bio- and chemostratigraphy of an expanded record of Oceanic Anoxic Event 2 (Late Cenomanian–Early Turonian) at Clot Chevalier, near Barrême, SE France (Vocontian Basin)

“…A significant increase in dissolved oxygen of ocean waters would have been brought about by cooling, which in turn apparently led to oxidation of previously deposited organic matter during the early stages of OAE 2 causing the transient release of many redox--sensitive and chalcophiic elements initially derived from basalt-seawater interaction during the PCE (Orth et al, 1993;Sinton and Duncan, 1997;Snow et al, 2005;Clarkson et a., 2018;Sweere et al, 2018). Oxidation of this organic matter during the PCE would have added isotopically depleted dissolved CO 2 to the bottom waters, probably in addition to that volcanically or hydrothermally derived, as suggested by osmium--isotope profiles from many parts of the world (Turgeon and Creaser 2008;Du Vivier et al, 2015 and mercury anomalies from the Atlantic and Western Interior Seaway (Scaife et al, 2017). Changes in upwelling intensity of such a CO 2 --rich water mass might well have influenced the composition of near-surface waters.…”

Ooidal ironstones in the Meso-Cenozoic sequences in western Siberia: assessment of formation processes and relationship with regional and global earth processes

“…The close correspondence between Hg anomalies and hypoxic intervals within the Meso-Cenozoic ironstone deposit in West Siberian Sea establishes the relationship between LIPs and OAEs (cf. Percival et al 2015Percival et al , 2018Ernst and Youbi 2017;Scaife et al 2017;Them et al 2019). These large volcanic events possibly contributed to the formation of extensive ironstone ore deposits on ocean floor (cf.…”

“…Recent investigations explore the relationship between periods of intense volcanism (Large Igneous Provinces, LIPs), global ocean anoxic events and the formation of ooidal ironstone deposits (Percival et al 2015;Ernst and Youbi 2017;Scaife et al 2017;Keller et al 2018). Although Van Houten (1986) and Van Houten and Arthur (1989) indicated a relationship between ooidal ironstones and anoxic events, this is yet to be investigated thoroughly (Turgeon and Creaser 2008;Jenkyns 2010;Raven et al 2018).…”

“…Further, concentrations of trace metals such as molybdenum, vanadium, uranium are widely used as proxies for reflecting (Rudmin et al 2019) depositional redox condition (Brumsack 2006;Tribovillard et al 2006;Algeo and Tribovillard 2009;Lebedel et al 2013). Mercury anomaly traces global volcanism in a few studies (Scaife et al 2017;Sabatino et al 2018;Them et al 2019). An integrated study involving pyrite framboids, trace element concentrations and mercury anomaly of the Bakchar ironstone deposit is likely to provide a detailed perspective for establishing the relationship between hypoxia, global volcanism, rifting and the origin of ooidal ironstones.…”

Cyanobacteria Proliferation in the Cenomanian‐Turonian Boundary Interval of the Apennine Carbonate Platform: Immediate Response to the Environmental Perturbations Associated With OAE‐2?

“…Large emissions of CO 2 were released during this time due to intense volcanic activity associated with the emplacement of Large Igneous Provinces (LIPs; Caribbean and High Arctic LIPs). These periods of enhanced eruptive activity have been invoked as the possible trigger of OAE-2 (Du Vivier et al, 2014Flögel et al, 2011;Jenkyns et al, 2017;Jones & Jenkyns, 2001;Kuroda et al, 2007;Meyers, 2014;Schaife et al, 2017;Schroder-Adams et al, 2019;Snow et al, 2005;Tegner et al, 2011;Turgeon & Creaser, 2008). Following, the CO 2 emitted to the atmosphere would have increased temperature and precipitation extremes (Heimhofer et al, 2018;Van Helmond et al, 2014;Wagner et al, 2013).…”