Sensitivity of the epeiric sea carbon isotope record to local-scale carbon cycle processes: Tales from the Mohawkian Sea

δ44/40Ca variability in shallow water carbonates and the impact of submarine groundwater discharge on Ca-cycling in marine environments

“…For example, some of the scatter observed in the putative record of calcium isotope variation in Phanerozoic oceans (Farkas et al, 2007), much of which is reconstructed from analyses of brachiopod shells collected from the deposits of epeiric seas, may be due to local Ca-cycling effects. A similar claim has been made for carbon isotope records reconstructed from epeiric sea carbonate successions (Patterson and Walter, 1994;Holmden et al, 1998;Immenhauser et al, 2003;Panchuk et al, 2005Panchuk et al, , 2006Melchin and Holmden, 2006;Fanton and Holmden, 2007;Immenhauser et al, 2008;Swart, 2008;LaPorte et al, 2009).…”

“…There is a growing body of work documenting local carbon cycling effects in epeiric seas, both in the geological past (Beauchamp et al, 1987;Holmden et al, 1998;Finney et al, 1999;Immenhauser et al, 2003;Kaljo et al, 2004;Gischler and Lomando, 2005;Panchuk et al, 2005Panchuk et al, , 2006Melchin and Holmden, 2006;Fanton and Holmden, 2007;Immenhauser et al, 2008;Swart, 2008;LaPorte et al, 2009) and at the present day (Patterson and Walter, 1994;Swart and Eberli, 2005). Recently, it was reported that a d 44/40 Ca study of Ordovician carbonates in the Williston Basin suggested the presence of local Ca-cycling effects in epeiric sea carbonates (Holmden, 2009).…”

Carbon cycling across the southern margin of Laurentia during the Late Ordovician

“…Carbonate sediments in these shallow platform settings show less variability than that observed in δ 13 C DIC but still vary by up to 2‰ (Swart et al, 2009). Observed regional differences in δ 13 C carb values across North America have led to the suggestion that geographic gradients in δ 13 C DIC (similar to those found in the modern) existed in Laurentia's epeiric sea (Holmden et al, 1998;Panchuk et al, 2005;Young et al, 2005).…”

“…However, a number of other processes (e.g. increased carbonate weathering, local anoxia, increased authigenic carbonate deposition, varying degrees of meteoric diagenesis, changes in C-weathering flux/source, and sea level fluctuations) can also cause or contribute to increases in δ 13 C on a variety of length and time scales (Kump and Arthur, 1999;Kump et al, 2000;Immenhauser et al, 2003;Panchuk et al, 2005;Melchin and Holmden, 2005;Fanton and Holmden, 2007;Schrag et al, 2013) without necessarily being associated with a major change in climatic forcing. Additionally, existing evidence of the GICE is strongly biased toward data from the interiors of shallow epeiric seas.…”

“…The restricted nature of epeiric seas and their proximity to terrestrial C-weathering sources could lead to the generation of spatial gradients and excursions in δ 13 C (Holmden et al, 1998;Melchin and Holmden, 2005;Panchuk et al, 2005;Fanton and Holmden, 2007). Remarkably little variation in surface water δ 13 C DIC (b0.5‰) is observed across open ocean settings, however modern examples of shallow carbonate platforms (e.g.…”