Strontium isotope geochemistry of modern and ancient archives: tracer of secular change in ocean chemistry

• Main Authors: Zaky, Amir, Brand, Uwe, Buhl, Dieter, Blamey, Nigel, Bitner, Aleksandra, Logan, Alan, Gaspard, Daniele, Popov, Alexander
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2018
• Subjects: Arctic; Indian; Pacific
• Online Access: http://hdl.handle.net/1807/93805; http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2018-0085

Strontium isotopes of marine archives provide a significant means for tracing physical and chemical processes operating over geologic time. Modern articulated brachiopods and halite samples were collected from all depths of the world’s main water bodies. Material from the Arctic, North and South Atlantic, North and South Pacific, Indian and Southern Oceans as well as Caribbean and Mediterranean Seas provide baseline parameters for diagenetic screening and reconstruction of seawater curves. The strontium isotopic ratio of modern brachiopods is unobscured by latitude, depth and biologic factors (Order, valves, and shell segment). However, there is a small but significant impact of external sources reflected by salinity and temperature on the strontium isotope ratio of modern brachiopods. We found a significant difference in 87Sr/86Sr of brachiopods from polar and temperate-tropical habitats (p = 0.001), which should be considered when working with deep-time archives. The average 87Sr/86Sr value of all our modern shells (0.709160 ±0.000019; N = 95) and halite (0.709153) is similar to values measured for modern seawater (0.710167 ±0.000009; p = 0.118). The radiogenic strontium content of present-day seawater does not vary significantly, and modern biogenic-calcite 87Sr/86Sr ranges from 0.709126 to 0.709233 with a fluctuation of about ± 0.000054. With the most rigorous diagenetic evaluations and stratigraphic assignment of deep-time samples, and applying the strontium isotope fluctuation recorded by modern biogenic calcite to ancient carbonates and a 1 Myr interval, reconstructions resulted in a seawater-87Sr curve with greater details during the Phanerozoic and Neoproterozoic. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.