Chemostratigraphy of Paleoproterozoic carbonate successions of the Wyoming Craton: tectonic forcing of biogeochemical change?

The carbon cycle and associated redox processes through time

“…Accepting these compositions as representative of the global pool of oceanic DIC would imply a near-trebling of f. Writing three years after Karhu & Holland (1996) published 'Carbon isotopes and the rise of atmospheric oxygen', Melezhik et al (1999) drew on additional data to define three apparently separate pulses of isotopic enrichment. That dissection of the record yields the three spikes in f that are represented by broken lines in figure 9a (alternative stratigraphic correlations yield only two spikes; Bekker et al 2003). The isotopic signal has been associated with other lines of geochemical evidence indicating that the atmosphere became more oxidizing at about the same time.…”

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

“…Iron formations in the Quadrilátero Ferrífero region in Brazil, Middleback Ridge (Gawler Craton) in South Australia, Nimba and Simandou Ranges in Liberia and Guinea, Krivoy Rog area in Ukraine, and Kursk Magnetic Anomaly (KMA) region in Russia are broadly similar in age based on available geochronological and chemostratigraphical constraints, and also display similar patterns of macrobanding (Prilutzky et al, 1992;Kulik and Korzhnev, 1997;Egal et al, 2002;Bekker et al, 2003;Phillips et al, 2006;Spier et al, 2007;Szpunar et al, 2011). These IFs were also deposited on reactivated continental margins, and are separated by prominent unconformities from overlying Palaeoproterozoic sequences, which correspond to a long gap in sedimentation following the supercontinent assembly at ca.…”

C- and Sr-isotope stratigraphy of the São Caetano complex, Northeastern Brazil: a contribution to the study of the Meso-Neoproterozoic seawater geochemistry

“…Oscillatory δ 13 C pathways encountered in carbonate sequences worldwide have been attributed, in the long term, to periods of high tectonic activity during which inputs and outputs of the available C org resulted in changes in the C-isotope composition of seawater respectively (Derry et al 1992, Lindsay and Brasier 2002, Bekker et al 2003. For instance, enriched δ 13 C values have been attributed to periods of high tectonic activity during which enhanced C org burial causes high levels of oxygenation levels in ocean and atmosphere, as well as high biologic diversification events (Des Marais 1997).…”

“…For instance, enriched δ 13 C values have been attributed to periods of high tectonic activity during which enhanced C org burial causes high levels of oxygenation levels in ocean and atmosphere, as well as high biologic diversification events (Des Marais 1997). These values are also expected during periods of high C org sequestration during widespread subduction of C org -rich sedimentary slabs and during widespread oceanic closure (Lindsay and Brasier 2000, Bekker et al 2003. Alternatively, it has also been proposed that short lasting phenomena such as upwelling, relative sea level changes, ocean water stratiphication, among other, can also generate fluctuating, environment dependant δ 13 C pathways in the sedimentary record as observed in Phanerozoic sedimentary succession (Mitchell et al 1996, Scholle andArthur 1980).…”

“…Well-constrained C-and Sr-isotope chemostratigraphic data for Proterozoic limestone sequences have been used to detect changes in the geochemical Schrag 2002, Bekker et al 2003.…”