Constructing a High-Resolution Record of Silurian Paleoclimate Using Carbonate Oxygen Isotopes

Abstract

The collection of δ¹⁸O data from carbonates provides insight into the temperature of Earth millions of years ago. Paleozoic δ¹⁸O records are currently compiled from brachiopod fossils because of their resistance to diagenetic alteration, but this data is relatively sparse and not well time-resolved. Bulk carbonate δ¹⁸O data can present a more full view geographically and temporally, but is more susceptible to diagenesis. Here we overcome these challenges by using simple age models alongside previously collected δ¹⁸O data from δ¹³C studies to show that bulk carbonates can preserve a primary isotopic signal of Silurian temperatures, as well as generate a high-resolution climate record of the Silurian Period that correlates climate fluctuations with δ¹³C events. We then present Δ47-derived temperatures from clumped stable isotope analysis from four Silurian sites, and show that the reported temperatures can be consistent with the bulk rock δ¹⁸O record. With bulk carbonate δ¹⁸O measurements able to reconstruct an accurate record of Silurian temperatures, this generates an even larger dataset than the existing brachiopod compilation from E. Grossman and Joachimski (2020), and shows that this technique can be further applied to construct temperature records throughout the Paleozoic. Additionally, having a clear link between δ¹³C and temperature allows for a better understanding of carbon isotope excursions and their causes.