Stable carbon isotope stratigraphy of the Silurian in the Jočionys-299 borehole (eastern Lithuania)

Abstract

In recent years it has become commonplace to formalize chemostratigraphic units and identify isotopic zones (chemo­stratigraphic units) from excursions. Stable carbon isotopes have been used in solving stratigraphic problems in the Silurian for more than 30 years. δ13C data supplement other stratigraphic proxies, allowing the subdivision of geological sections and more precise correlation. In this paper we give new δ13C data from the Silurian section of the Jočionys-299 borehole, which is located in eastern Lithuania, crossing shallow marine and lagunal deposits. Based on δ13C variability, the Ireviken carbon isotope excursion (CIE), the Šlilalė CIE, and probably the Valgu CIE have been identified in the investigated section. The Valgu CIE is linked to the lower part of the Švenčionys Formation. The Ireviken CIE is linked to the upper parts of the Švenčionys Formation and the Paprieniai Formation (rise in δ13C values), the Jočionys Formation (moderately stable δ13Ccarb values) and the Verknė Formation (fall in δ13C values). A small negative δ13C shift is documented in the Pabradė Formation. Chemostratigraphy together with biostratigraphic data allow us to correlate eastern Lithuanian lithostratigraphic units (shallow marine environment) with the global Silurian Geochronological Scale more accurately.

Keywords

• carbon isotopes
• chemostratigraphy
• silurian
• lithuania.