The Ordovician Sebree Trough: An oceanic passage to the Midcontinent United States

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

“…In order to have the same effect as F 70 at À 29x, the required flux of upwelled carbon is 459 Â 10 12 mol C yr À 1 , equivalent to 58 m 3 yr À 1 of water. This quantity is reasonable from the perspective of current velocity in modern upwelling zones (e.g., 0.02 m s À 1 to 0.1 m s À 1 in the Peru Margin upwelling zone; Tomczak and Godfrey, 1994), assuming a range in the width of the Sebree Trough from 25 km to 125 km (Kolata et al, 2001) and depth on the order of 10 2 m to 10 3 m. This carbon flux is likely an underestimate of the amount of carbon required, however, because the waters that upwelled along the Sebree Trough were high in phosphate (Kolata et al, 2001), so the flux of low d 13 C carbon from upwelling would have to offset the isotopic effects of enhanced productivity (Panchuk et al, accepted for publication). Another difficulty with this scenario is that low d 13 C DIC from upwelling would have entered the Midcontinent from the south, then moved northward, so the lowest d…”

“…Upwelling Kolata et al (2001) suggest that the Sebree Trough (Fig. 1) provided a pathway into the Mohawkian Sea for waters from the oxygen minimum zone of the Iapetus Ocean, with prevailing winds and the Coriolis effect transporting these waters northward onto the Midcontinent carbonate platform.…”

“…The Midcontinent may also have received low d 13 C carbon from chemical weathering on land (Holmden et al, 1998), and from ocean oxygen minimum zone waters upwelled along the Sebree Trough ( Fig. 1; Kolata et al, 2001). Seawater may have exchanged relatively freely between the Taconic Aquafacies and the Iapetus Ocean, and between the Taconic Aquafacies and the Southern and Arch Margin Aquafacies, distributing 13 C-enriched DIC from the Taconic Foreland Basin photic zone.…”

“…Differences in carbon cycling between aquafacies in the Mohawkian Sea have been linked to water column depth and seawa- Holmden et al, 1998;Panchuk et al, accepted for publication). Lithofacies are modified from Leslie (1995), Leslie and Bergströ m (1997), and Kolata et al (2001). Nash.…”

“…D.=Jessamine Dome. The position of the Sebree Trough is derived from Kolata et al (2001). b) Model carbon reservoirs.…”