Chemostratigraphy of the Mesoproterozoic‐Neoproterozoic Transition

Characteristics of the carbon cycle in late Mesoproterozoic: Evidence from carbon isotope composition of paired carbonate and organic matter of the Shennongjia Group in South China

“…Therefore, such 13 C-enriched carbonates also occur in the Yemahe and Wenshuihe formations of the Shennongjia Group (this work; Tian et al, 2018;Zou et al, 2019), thereby suggesting a possibly global phenomenon. In addition, some studies have proposed that the sharply δ 13 Ccarb positive excursion up to +5‰ around 1200 Ma can be served as a marker for global stratigraphic correlation (Frank et al, 2003;Bartley et al, 2007;Lathrop, 2018;Silva-Tamayo et al, 2018;Paula-Santos et al, 2021) and consequently, these new observations from South China raise questions about the term 'boring billion' adopted for the Mesoproterozoic.…”

“…It is also interesting to note that substantially lower  13 Ccarb values <-2‰ are observed during the interval from ~1100 to 1050 Ma, in several worldwide localities such as in the Turukhansk Group in Siberia (Knoll et al, 1995;Bartley et al, 2001), Vazante Group in Brazil (Azmy et al, 2001;Misi et al, 2011), Bylot Supergroup in the Nunavut of Canada (Kah et al, 1999(Kah et al, , 2001, and Atar/EI Mreïti Group in West Africa (Kah et al, 2012;Gilleaudeau and Kah, 2013;Silva-Tamayo et al, 2018). The lowest values close to -6‰ are generally present in deep-water sedimentary environments and ascribed to the diagenetic oxidation and anaerobic remineralization of organic carbon (Gilleaudeau and Kah, 2013).…”

“…Thus, the  13 Ccarb and  13 Corg are widely used as indicators for the fraction of organic carbon burial [forg, forg = Fbo/(Fbo + Fbc), where Fbo is the flux of organic carbon burial, and Fbc represents the flux of carbonate burial], which is then used to infer the oxidation state of the Earth's surface environments (Hayes et al, 1999;Bartley and Kah, 2004). It has been observed that the  13 Ccarb values increase substantially from ~0‰ in the early Mesoproterozoic to ~+4‰ in the late Mesoproterozoic (Kah et al 1999;Bartley and Kah, 2004;Kah et al, 2012;Silva-Tamayo et al, 2018;Lathrop, 2018;George et al, 2019;Paula-Santos et al, 2021). These moderately positive  13 Ccarb values are generally attributed to elevated rates of organic carbon burial.…”