Possible decoupling of the geochemical cycles of sulfur and carbon during the early Cretaceous (Hauterivian)

Author(s): Kristall, B.; Hurtgen, Matt T.; Sageman, Bradley B.
Author Affiliation(s): Primary:
Northwestern University, Department of Earth & Planetary Sciences, Evanston, IL, United States
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: During the past decade there has been significant focus on understanding the global sulfur cycle during the Mid- to Late-Cretaceous. The occurrence of several oceanic anoxic events (OAEs) during this time period and the relationships among the sulfur, carbon, and oxygen cycles controlling the redox state of the ocean have been motivating factors in this research. These efforts have centered on identifying what impact, if any, massive volcanism and evaporite deposition associated with opening of the South Atlantic had on the sulfate content of the ocean and what role these events may have played in triggering OAEs. However, relatively little work has been done to characterize the sulfur cycle during the Early Cretaceous. In the present study, we have analyzed the sulfur isotope composition of carbonate-associated sulfate (CAS) from Hauterivian-aged samples (Resolution Guyot ODP Hole 866A). We found a previously unrecognized ≈4 ppm positive sulfur isotope excursion in sulfate sulfur. This well structured, excursion spans approximately 15-20 m of core and is estimated to be less than 300-500 kyr. Corresponding carbonate carbon isotope analyses do not show a comparable, well-structured excursion. During this event δ13C values vary only by 0.25-0.5 ppm. The rapid shift and recovery in δ34S sulfate suggests either that this event was regional or that the Early Cretaceous oceans contained low sulfate levels (<5 mmol/kg) with high total input/output fluxes. We will utilize a simple geochemical box model of the C and S cycle to assess the variability in the fluxes and/or fractionation factors necessary to produce the observed S isotope shift without a corresponding change in C isotope composition.
Year of Publication: 2013
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cores; Cretaceous; Hauterivian; Leg 143; Lower Cretaceous; Marine sediments; Mesozoic; Mid-Pacific Mountains; North Pacific; Northwest Pacific; ODP Site 866; Ocean Drilling Program; Pacific Ocean; Resolution Seamount; Sediments; West Pacific
Coordinates: N211957 N211958 E1741853 E1741850
Record ID: 2015083158
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