INITIAL RESULTS OF INTEGRATED CONODONT AND CARBON ISOTOPE BIOCHEMOSTRATIGRAPHY OF THE SILURIAN ALTAJME CORE, GOTLAND, SWEDEN

The Altajme core was recovered from Gotland, Sweden, and has previously been studied for high-resolution chemostratigraphy of carbon, oxygen, nitrogen, and sulfur isotopes. A series of seven high-resolution Chemical Abrasion – Isotope Dilution – Thermal Ionization Mass Spectrometry (CA-ID-TIMS) dates have also been generated from K-bentonites preserved in the core. The position of multiple identifiable ash layers near the Llandovery-Wenlock boundary and the early Homerian are also present in the core and help to identify the Sheinwoodian ‘Ireviken’ and Homerian ‘Mulde’ biogeochemical events. Sampling for chemical analysis had to be conducted prior to destructive sampling for biostratigraphy of conodonts. Now, the first conodont samples are available from the Sheinwoodian interval of the Altajme core. Here, we present these initial findings that allow us to combine the multiple integrated chemostratigraphic signals with the excellent conodont biostratigraphy of Gotland. The Silurian succession of Gotland, Sweden, serves as the primary reference standard for the conodont zonation of the Wenlock and Ludlow series.

Given the exceptionally marly strata of the Sheinwoodian portion of the Altajme core, we utilized a hybrid digestion method of an initial soak in Stoddard Solvent, followed by a soak 10% double-buffered acetic acid. Following the first soak the Stoddard Solvent was recovered, and the sample was immediately covered with boiling water containing a half-teaspoon of Sodium Metaphosphate. Most samples completely disaggregated upon being covered with the boiling water solution and the samples were small enough that they did not require heavy liquid separation. The few samples that did not disaggregate were followed by a second soak in 10% double-buffered acetic acid and resulted in similarly small samples.