Title: Baltoscandian Ordovician and Silurian brachiopod carbon and oxygen stable isotope trends: Implications for palaeoenvironmental and palaeotemperature changes.
Author: Gul, Bilal
University of Tartu

Introductory information
87 brachiopod samples were collected Lelle D-102 drill core and 14 outcrops in Estonia (Ohesaare, Eivere, Reinu, Abula, Jaani, Paramaja, Undva, Porkuni, Hosholm, Saxby, Rakvere, Ristna, Aluvere, and Pakri; Figure 1) spanning unevenly from the Middle Ordovician up to the Pridoli (Silurian). The new material covers mainly Katian-Sheinwoodian interval and some Dapingian and Pridoli units. Previously published brachiopod isotopic data was used for comparison and for filling in the stratigraphic intervals not covered by the newly collected material (Rasmussen et al. 2016, Heath et al. 1988, Kaljo et al. 2017, Hints et al. 2010 and Gul et al. 2021.

Methodological information
The powdered material was analysed for stable isotopes (oxygen and carbon) using a Thermo Scientific Delta V Advance continuous flow isotope ratio mass spectrometer at the Department of Geology, University of Tartu. Delta V advantage (continuous flow) + GasBench II samples were dissolved (reaction time >8 hours) in H3PO4 (99%) at 25°C. The results are reported as d notation in per mil relative to Peedee belemnite (VPDB) for both oxygen and carbon, and reproducibility of the results is generally better than ±0.1‰ and ±0.2‰ for carbon and oxygen (respectively). The international laboratory standards (from IAEA) IAEA-60, NBS 18 and LSVEC were used. 

Data specific information:
Ordovician and Silurian brachiopods range between ca -7‰ to 0‰ and -2.6‰ to +7.3‰.
‰= per mil
C=carbon
O=oxygen

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