21 Geochemical Proxies for Marine and Continental Paleoenvironments

Monday, 15 April 2024
3:50 PM - 5:30 PM
Windsor Ballroom Salon A

THE POTENTIAL OF THE CAROLINA TERRANE AS A PALEOCEANOGRAPHIC RECORD OF THE IAPETUS OCEAN

Paper number: 21-1
Program: Theme Sessions
Time: 3:50 PM – 4:10 PM

Authors

Abstract

Fossils and detrital zircon dates suggest that the metasedimentary successions associated with the Carolina Terrane span from the Ediacaran through the Middle Cambrian, and are thus contemporaneous with the diversification of early animal phyla. Since these sediments were deposited on the flanks of an arc in the Iapetus Ocean, they have the potential to provide a valuable record of open ocean chemical conditions during this crucial interval in earth history. This study focuses on metasediments from the Ediacaran through Early Cambrian Albemarle Group, collected from the New London Syncline in central NC, supplemented by samples from the Middle Cambrian Asbill Pond Formation in South Carolina. The Albemarle Group preserves fine-scale sedimentary structures, including hummocky cross stratification and soft sediment deformation, indicating deposition in a tectonically active setting at or near storm wave base. Samples from a site along the axis of the New London Syncline, representing some of the youngest (Early Cambrian) material exposed in the fold structure, show domal stromatolites with millimetric lamination, and were deposited in the photic zone.

Despite little to no preserved organic carbon, samples yield measurable nitrogen, likely preserved in the form of clay-bound ammonium. Isotope results suggest a marine nitrogen cycle based on assimilation of nitrate was already in place by the Ediacaran, and a slight shift toward more negative values in the Early Cambrian may indicate an increased role of nitrogen fixation. Redox-sensitive trace elements are consistently depleted below crustal levels – as this is unlikely to reflect oxic conditions in this time interval, it probably reflects the low inventories of dissolved trace metals in seawater. Analysis of iron speciation and pyrite petrography will provide independent constrains on redox conditions, allowing for trace elements to be interpreted in light of global trace element inventories.

Geological Society of America Abstracts with Programs. Vol. 56, No. 2

doi: 10.1130/abs/2024SE-398645

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