Enrichment of redox-sensitive trace metals (U, V, Mo, As) associated with the late Hauterivian Faraoni oceanic anoxic event

Abstract

The Faraoni Level is a short-lived oxygendeficient event that took place during the latest Hauterivian. In order to improve our understanding of the palaeoenvironmental conditions that occurred during this event, we have analysed the contents of several redox-sensitive trace elements (U, V, Mo, As, Co, Cd, Cu, Zn, Ni, Pb, Cr) from bulk limestone samples of late Hauterivian-early Barremian age from three reference sections. U, V, Mo and As show consistent and significant enrichments during the Faraoni event whereas the other redox-sensitive trace elements analysed here are not systematically enriched. In order to explain this discrepant behaviour, we propose that the Faraoni Level was deposited during a period of anoxic conditions near the sediment-water interface. The distinctive peaks in U, V, Mo and As contents are traceable throughout the three studied sections and represent a good correlation tool which helps to identify the Faraoni Level and its equivalents in the western Tethyan realm and outside of the Tethys. For example, a peak in U contents in upper Hauterivian sediments of the northwestern Pacific realm (ODP leg 185, site 1149) may well be an expression of the Faraoni event in this particular basin.

Evidence for oxic conditions during oceanic anoxic event 2 in the northern Tethyan pelagic realm

“…In the case of the formation of Cretaceous black shales, different models have been proposed including e either alone or in combination e large-scale increases in primary productivity, world-wide expansion of oxygen-minimum zones and the intensification of water-column stratification (Schlanger and Jenkyns, 1976;Arthur and Schlanger, 1979;Jenkyns, 1980;Scholle and Arthur, 1980;Bralower and Thierstein, 1984;Pederson and Calvert, 1990;Jenkyns, 2003;Pancost et al, 2004;Hardas and Mutterlose, 2007;Pearce et al, 2009). Recently, the stratigraphic distribution of redox-sensitive trace elements (RSTE; e.g., U, V, As, Mo and Co) has been explored in OAE-related sediments throughout the Mesozoic, in order to trace the temporal and spatial evolution in oxygen contents (Algeo and Maynard, 2004;Bodin et al, 2007;Brumsack, 2006;Algeo and Maynard, 2008). In addition, the evolution in phosphorus (P) contents and accumulation rates has been employed to trace both changes in the marine P cycle and their impact on primary productivity rates, as well as the influence of anoxic bottom-water conditions on the capacity of the sedimentary reservoir to retain P (Ingall and Van Cappellen, 1990;Van Cappellen and Ingall, 1994;Mort et al, 2007).…”

“…The determination of Al, Fe and redox-sensitive trace elements was performed on bulk rock following the procedure described in Bodin et al (2007). The samples were attacked by suprapur nitric acid and elements contents were determined by a quadrupole ICP-MS (ELAN 6100, Perkin Elmer), using a quantitative mode with a mean precision of 1e2% depending on the element under consideration.…”

Bridging the Faraoni and Selli oceanic anoxic events: late Hauterivian to early Aptian dysaerobic to anaerobic phases in the Tethys

“…This suggests that the RSTE are present in the soluble carbonate phase and not derived from partial leaching of the detrital fraction (cf. also Bodin et al, 2007). The RSTE data were, therefore, not normalized by aluminum contents.…”

“…These elements are considered as redox-sensitive trace elements (RSTE), which are used as an indicator of the presence and intensity of oxygen depletion at the site of sediment deposition (Algeo and Maynard, 2004;Tribovillard et al, 2006;Bodin et al, 2007).…”

Determination of Vanadium (IV) and (V) in Southern Nevada Groundwater by Ion Chromatography-Inductively Coupled Plasma Mass Spectrometry~!2009-12-24~!2010-02-10~!2010-05-11~!

“…Vanadium pentoxide aerosols are "possibly carcinogenic to humans" [1,6,7]. Vanadium is an environmentally important trace element because of its redox sensitivity [2,[8][9][10].…”