Upper Devonian mercury record from North America and its implications for the Frasnian–Famennian mass extinction

Combined Nitrogen‐Isotope and Cyclostratigraphy Evidence for Temporal and Spatial Variability in Frasnian–Famennian Environmental Change

“…Sedimentary TN contents increase from <0.1 wt% in background strata to up to 0.17 wt% and 0.23 wt% across FF boundary strata of the H‐32 and Kowala records, respectively (Figures 3a and 3b). For both archives, this rise in TN broadly matches a previously reported increase in TOC contents (Liu et al., 2021; Percival et al., 2019, 2020). In contrast, both TOC and TN contents are extremely low (<0.1 wt%) throughout the studied interval at Sinsin (Figure 3c).…”

“…Biostratigraphy for H-32 is from DeVleeschouwer et al (2017); Kowala from this study (TableS2in Supporting Information S1); Sinsin fromSandberg et al (1988), referred to new conodont zonation whereby the presence of A. ubiquitus indicates the FZ13c Zone(Girard et al, 2005;Sandberg et al, 2002). Carbon data for the H-32 core are fromLiu et al (2021); Kowala TOC, P tot , and P tot / Al data are fromPercival et al (2019Percival et al ( , 2020; Sinsin δ 13 C data are from DeVleeschouwer et al (2017). All other data are from this study.…”

“…The H‐32 core drilled sediments deposited on the western slope of this basin, predominantly consisting of carbonate‐poor siltstones and shales (Witzke & Bunker, 2002). The FF boundary is defined by conodont biostratigraphy (Day & Witzke, 2017; De Vleeschouwer et al., 2017), and is placed just stratigraphically above a transition from the relatively organic‐lean (typically <0.5 wt% total organic carbon; TOC) green and gray siltstones and marls of the Sweetland Creek Shale to much more organic‐rich (2–5 wt% TOC) mudstones of the Grassy Creek Shale (Day & Witzke, 2017; Liu et al., 2021; Witzke & Bunker, 2002). However, there is no biostratigraphic evidence (i.e., missing conodont zones) of a major disconformity associated with this abrupt lithological change, and a gradual increase in δ 13 C org (assumed to mark the UKW Level) across this transition shows no sharp step in values that would suggest missing strata.…”

“…A cyclostratigraphic timescale has been developed for the FF interval of the H-32 core, based on magnetic susceptibility and carbon-isotope data, together with conodont biostratigraphy (Da Silva et al, 2020;De Vleeschouwer et al, 2017). The new δ 13 C org data set for the H-32 core reported by Liu et al (2021), whilst of lower resolution than the record of De Vleeschouwer et al (2017), spans a broader stratigraphic range and suggests that the base of the isotopic excursion associated with the UKW Event is stratigraphically lower than previously assumed. As a key chemostratigraphic anchor point in defining the Frasnian-Famennian timescale around the world, this repositioned base of the δ 13 C excursion allows for the cyclostratigraphic age model of the H-32 core, and its correlation with the other FF records in De Vleeschouwer et al (2017) and Da Silva et al (2020), to be refined more accurately.…”

Carbon cycle dynamics and ecology revealed by the carbon isotopic composition of single organic microfossils during the Late Devonian Biotic Crisis

“…Our data also support the findings of others (e.g., Boyer et al, 2021) that oxygen levels were spatially and temporally variable; such variability could act as an additional stressor to marine benthic fauna. What further triggers lead to the elevated extinction seen specifically in the Lower and Upper Kellwasser Events remains uncertain; while volcanism has been implicated (Racki et al, 2018), this evidence is not conclusive, nor global in distribution (Liu et al, 2021; Pippenger et al, 2020).…”