The Silent VOICE—Searching for Geochemical Markers to Track the Impact of Late Jurassic Rift Tectonics

Abstract

A causal mechanism for the Volgian Isotopic Carbon Excursion (VOICE) remains enigmatic. Elemental geochemical profiles of the Deer Bay Formation, Sverdrup Basin, Arctic Canada that record the VOICE and contemporaneous strata are herein examined to provide insight into depositional environments during Late Jurassic-Early Cretaceous time. Silver (Ag) and Cadmium (Cd) are enriched across the VOICE at localities on Axel Heiberg Island, and in Tithonian (∼Volgian) strata of Ellef Ringnes Island. Other redox-sensitive trace elements do not exhibit spatially or temporally consistent patterns and indicate oxic conditions. A lack of relationship across the VOICE between Ag and the quality, quantity, and isotopic composition of organic matter suggests that the negative isotope excursion and interval of Ag enrichment are not merely functions of changes in organic matter source or amount, while a lack of spatially consistent change in geochemical indices of weathering similarly excludes climate change and/or sediment provenance as a driver. Therefore, in a ventilated setting and without marked changes in organic matter content, Ag enrichment may be due to hydrothermal activity. Contemporaneous Ag enrichment in strata from Svalbard suggests that a source of hot fluid sufficient to produce Ag-rich seawater may have been related to rifting in the adjacent proto-Amerasia Basin. Hydrothermal activity may also have been a widespread source of isotopically depleted carbon. This work develops new geochemical fingerprints that may be used to trace the spatial extent of hydrothermal events that do not leave an extinction pattern but may nonetheless have a far-reaching influence on biogeochemical systems.