A meta-analysis of the Steptoean Positive Carbon Isotope Excursion: The SPICEraq database

The Steptoean Positive Carbon Isotope Excursion (SPICE), inorganic aragonite precipitation and sea water chemistry: Insights from the Middle–Late Cambrian Port au Port Group, Newfoundland

“…A review of published global SPICE data (Pulsipher et al, 2021) confirms that water depth and facies have a significant effect on the extent of the carbon isotope excursion. In the Amadeus Basin (Schmid et al, 2018), open marine sequences were found to show the full +5‰ excursion, whereas nearshore shelf environment deposits displayed a reduced (+2 to +3.5‰) excursion, similar to the values observed in the PAP.…”

“…The positive δ 13 C SPICE excursion in the PAP, is part of a global phenomenon (Pulsipher et al, 2021; Saltzman et al, 2000). In Newfoundland, it was first identified in the FCS by Saltzman et al (2004) and in the MPS by Hurtgen et al (2009).…”

“…It was subsequently observed in both by Barili et al (2018) although not as clearly in the MPS as by Hurtgen et al (2009). Globally, the SPICE δ 13 C can reach up to +5 ‰ (Pulsipher et al, 2021; Saltzman et al, 2000) but less so in the PAP. Saltzman et al (2004) observed a δ 13 C excursion of ca +3.5‰, Hurtgen et al (2009) ca +4‰, and Barili et al (2018) ca +2.5 to +3‰ (Figures 3 and 4).…”

“…According to Schmid et al (2018), the lower δ 13 C signature in nearshore sediments compared to the deep shelf, suggests a possible isotopic gradient between dissolved inorganic carbon in sea water and atmospheric CO 2, which was very high in the Cambrian (3500–4000 µatm, Berner, 2006). Jones et al (2019) and Pulsipher et al (2021) suggested that the trend was probably driven by different early diagenetic conditions based on the extent of interaction between sea water and sediment in shallow (fluid‐buffered diagenesis) and deep (sediment buffered diagenesis) water carbonates. The thickness of the SPICE also varied in the Amadeus Basin, ranging from 14 to 119 m with thicker sequences in the deeper areas of the basin (Schmidt et al, 2018).…”

“…The Cambrian was a time of significant evolution of life in the oceans with not only two major evolutionary explosions (Phase 1 and 2) but also extinctions during the Sinsk event and, much more significant, at the Steptoean Positive Carbon Isotope Excursion (SPICE) in the Late Cambrian (Furongian) (Zhuravlev & Wood, 2018). The SPICE (Saltzman et al, 1998) is a global carbon isotope excursion with δ 13 C values typically ca 4–5‰ although values can be lower (Pulsipher et al, 2021).…”