Abstract
High-resolution osmium (Os) isotope stratigraphy across the Cenomanian–Turonian Boundary Interval from 6 sections for four transcontinental settings has produced a record of seawater chemistry that demonstrates regional variability as a function of terrestrial and hydrothermal inputs, revealing the impact of palaeoenvironmental processes. In every section the 187Os/188Os profiles show a comparable trend; radiogenic values in the lead up to Oceanic Anoxic Event 2 (OAE 2); an abrupt unradiogenic trend at the onset of OAE 2; an unradiogenic interval during the first part of OAE 2; and a return to radiogenic values towards the end of the event, above the Cenomanian–Turonian boundary. The unradiogenic trend in 187Os/188Os is synchronous in all sections. Previous work suggests that activity of the Caribbean LIP (Large Igneous Province) was the source of unradiogenic Os across the OAE 2 and possibly an instigator of anoxia in the oceans. Here we assess this hypothesis and consider the influence of activity from other LIPs; such as the High Arctic LIP.A brief shift to high radiogenic 187Os/188Os values occurred in the Western Interior Seaway before the onset of OAE 2. We evaluate this trend and suggest that a combination of factors collectively played critical roles in the initiation of OAE 2; differential input of nutrients from continental and volcanogenic sources, coupled with efficient palaeocirculation of the global ocean and epeiric seas, enhanced productivity due to higher nutrient availability, which permitted penecontemporaneous transport of continental and LIP-derived nutrients to trans-equatorial basins.
Highlights
The Cenomanian–Turonian boundary (CTB) Oceanic Anoxic Event 2 (OAE 2) records an extensive period of global anoxia, represented worldwide by sections containing organic-rich marine sedimentary rocks
Based on the trend to unradiogenic Osi values at Site 1260, Vocontian Basin, Furlo and Site 530 we suggest that the initiation of volcanism was at least ∼200 kyr prior to ‘A’ (∼94.58 Ma; Fig. 3, CLIP i), with the major pulse of submarine volcanism happening at ∼−30 kyr (94.41 Ma; Fig. 3, CLIP ii), where all locations possess near mantle-like Osi values
An influx of nutrients from the continents preconditioned the oceans and helped to trigger OAE 2 through increased productivity and, to Jones and Jenkyns (2001), we infer that rising sea level may have been the tipping point for the development of widespread anoxia
Summary
The Cenomanian–Turonian boundary (CTB) OAE 2 records an extensive period of global anoxia, represented worldwide by sections containing organic-rich marine sedimentary rocks. We present a high-resolution initial osmium isotope (187Os/188Os; Osi) stratigraphy of the upper Cenomanian to lower Turonian from 4 transcontinental sections, and the Osi data from two previously analyzed representative sections of the protoNorth Atlantic and Tethyan margin (Fig. 1; ODP Site 1260 and Furlo; Turgeon and Creaser, 2008) with additional analysis to enhance resolution.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
